19th International Conference on Numerical Combustion

Kyoto, JapanMay 7-10, 2024

Book of Abstracts

Welcome Note
Carbon dioxide (CO2) is the largest contributor to greenhousegases, and the majority of its emissions originate fromthe combustion of fossil fuels such as coal, oil and naturalgas. Therefore, countermeasures to the impact of CO2 areurgently required. Energy that is directly converted fromwind and sunlight, that is renewable energy has gained
attention in recent years as an alternative to the energy
obtained through burning of fossil fuels. However, theirglobal application is time-consuming and demanding.
Therefore, to obtain clean and efficient energy during
combustion, research has been actively conducted on
methods for burning carbon-free fuels such as hydrogen(H2) and ammonia (NH3), which do not contribute to net CO2
emissions. H2 and NH3 can be produced ultimately from theelectrolysis of water using renewable energy, increasing the
expectations for the realization of carbon-free combustion
systems used in energy production devices. Furthermore,
improved safety, reduced costs, and reduced emissions ofenvironmental pollutants from aircraft engines are strongly
desired. Although the use of aircrafts temporarily declined
owing to the impact of the COVID-19 pandemic, it is expected
to increase in the future. The usage of rockets is also
expected to increase as these are at the heart of the spaceindustry for important infrastructure related to the futuresocial, economic, and security activities. In addition, precise
prediction and control of wildland fires have been serious
challenges. Therefore, further understanding of combustion
physics and development of advanced combustion
technologies are becoming increasingly important.
Combustion is an extremely complex phenomenon in which
reactions involving hundreds of chemical species occur
over thousands to tens of thousands of steps at most, ina turbulent flow field, accompanied by heat generation.
Therefore, numerical simulations are essential for elucidating
the mechanisms, developing combustion systems that
efficiently utilize these principles, and selecting optimal
operating conditions.
The International Conference on Numerical Combustion(ICNC) is a major international conference in the combustion
field. The ICNC has been held biennially for exchanging
information and improving the level of research on thescience and technology of combustion through multilateralexchange. Locations for the ICNC were in Europe and theUnited States; the recent locations for ICNC include Avignon(France) in 2015, Orlando (U.S.A.) in 2017, Aachen (Germany)in 2019, and San Diego (U.S.A.) in 2022 (postponed by one
year because of COVID-19).
The 19th ICNC in 2024 (ICNC2024) will be held in Kyoto,
Japan: the first non-western hosting venue for the
conference. The ICNC2024 will be held with the full supportof The Combustion Institute and its Japan section. Kyoto
city is not only the cultural capital of Japan and a major
tourist destination, but also famous as the place where the
Kyoto Protocol regarding the reduction of greenhouse gas
emissions was first adopted on 11 December, 1997. At the
ICNC2024, a total of 20 mini-symposia will be held, and 4
invited lectures and more than 470 oral presentations will bedelivered in the mini-symposia and the general tracks. We
sincerely hope that researchers and engineers worldwide
working in this field will come together and join in lively
discussions and information exchange on both basic andapplied research.

Greetings, on behalf of the Organizing Committee

Ryoichi Kurose, Mamoru Tanahashi and Yasuhiro Mizobuchi

1Invited Speaker
Hideaki Kobayashi

Tohoku University, Japan

Fundamentals and Applications ofAmmonia Combustion for Carbon Neutrality

Abstract

Short Biography

Ammonia is one of the most fundamental chemicals. It is an

Hideaki Kobayashi is a Research Professor at Tohoku

investigated for more than 80 years. It is currently a candidate

ammonia combustion, development of ammonia gas

old and new fuel whose potential for fuel use has already been
for decarbonization fuels alongside hydrogen towards carbon

neutrality. Basic research and technological development

have intensified rapidly within the last decade. The focus onammonia or hydrogen depends on the geopolitical conditions

affecting the availability of renewable energy for production
and the cost of transportation of these fuels. The huge demandfor energy in the power generation, industrial and maritime

sectors means that the expected future distribution volumes
are also huge. This has created international competition as
well as international cooperation to build global supply chains.

Ammonia and hydrogen can be regarded as family fuelswith interdependencies in the production process as well as

University, Japan. He is involved in projects on basic
turbines and industrial furnaces using ammonia, with a view
to decarbonization and fuel conversion in the energy andindustrial sectors. He also works on national and international

project evaluations and international standardization onammonia utilization as a fuel. Professor Kobayashi has been
involved in research on fundamental processes of combustion
phenomena in extreme environments, such as high-pressure
turbulent premixed combustion, supersonic combustion,

microgravity combustion and low-oxygen, high-temperature
air combustion. He served as the team leader of the ammonia

direct combustion research in the national project SIP “Energy
Carriers”, which ran for five years from 2014.

commonalities in terms of decarbonization fuels, but their

Professor Kobayashi completed his master degree at Tohoku

has very high reactivity and ignitability and NOx production isuniversity, where he obtained his PhD in 1991. After working as

combustion characteristics are completely different. Hydrogendue to thermal NO, whereas ammonia has very low reactivity
and ignitability and NOx production is due to fuel NO.

Modern combustion science, i.e. detailed reaction mechanism
construction, large-scale numerical analysis methods andlaser diagnostics, play an important role in solving these
problems. In addition, the use of ammonia as a fuel in a highpressure environment, such as large gas turbines and marine

engines, requires the technological development to injectliquid ammonia and burn. New basic research is needed on

liquid ammonia spray formation and combustion, and low
NOx combustion methods under high pressure. The lecture

describes the progress in technological development towards
the social implementation of ammonia combustion systems,

University in 1983 and became an assistant professor at thean associate professor, he became a professor at Institute of
Fluid Science, Tohoku University in 2003. He served as Program

Co-Chair of the 32nd International Symposium on Combustionin 2008, President of Combustion Society of Japan from 2015
to 2017 and Vice-President of The Combustion Institute from2016 to 2020. He received The Commendation for Scienceand Technology by The Minister of Education, Culture, Sports,

Science in 2017 and Technology and The Thermal EngineeringAward for Outstanding Academic Contribution by The Japan

Society of Mechanical Engineers in the same year. In 2018 he
was honored as a Fellow of The Combustion Institute and in
2022 he was awarded The Bernard Lewis Gold Medal.

as well as basic research efforts, particularly in ammonia gas
turbine combustion.

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19th International Conference on Numerical Combustion

Invited Speaker
Terese Løvås

Norwegian University of Science and Technology, Norway

Do the Thermodynamic Properties of New
Fuels Challenge the Current State-of-the-art
Modeling?

Abstract
After the UN Climate Meeting COP28, there is little doubt that weare experiencing the “beginning of the end” of the fossil fuel era.
Nearly every country in the world is committed to transitioning
away from fossil fuels. Other critical key outcomes from themeeting included a commitment to triple the renewable energy
capacity by 2030. The combustion community has, for a while
now, already devoted much research to address these matterswith a focus on understanding and enabling the usage of lowcarbon or carbon-free fuels such as methanol, hydrogen, andammonia in combustion devices. It has been argued that
combustion as a means of energy production is not the obstacle
to climate change but rather the fuel used.
However, the advances in combustion technology that are
now becoming state-of-the-art represent a challenge whenintroducing new fuels to existing combustion technology. Highpressure direct injection is a common strategy for fuel delivery
systems in internal combustion engines, whereas reactivity
controlled compression ignition (RCCI) and direct dual fuelstratification (DDFS) are being explored to achieve satisfactory
engine performance with effective control combustion tominimize emissions. Moderate or Intense Low oxygen Dilution(MILD) combustion technology is yet another strategy is anotherpromising strategy for clean and efficient combustion.
These new approaches do, however, require a fundamental
understanding of the fuel’s behavior under demanding
conditions. Differences in boiling point and latent heat ofvaporization give rise to phenomena such as cavitation or flash
boiling in the injection system and cause spray development
and evaporation inside the combustion chamber to deviatesignificantly from the familiar hydrocarbon fuel sprays. It is
worth noting that thermodynamic properties of ammonia
are usually found in refrigeration tables. Many modelingapproaches currently widely used in combustion research do notsatisfactorily account for these phenomena, and existing models
need to be further adapted and extended for a broader range ofthermodynamic properties.
In the lecture, an overview of the most critical properties ofconcern will be given alongside a description of their importancefor phenomena such as vaporization, cavitation, and flash
boiling. Existing models will be reviewed to explore areas ofdevelopment. Comparison with experiments will allow us to
identify the importance of such model development to capture
new fuels’ applicability in current combustion devices correctly.
Short Biography
Dr. Løvås completed her master’s in relativistic astrophysics
at the Niels Bohr Institute at the University of Copenhagen in
Denmark in 1998. She obtained her doctorate in combustion
physics at Lund University in Sweden in 2002, focusing on
chemical kinetics and model reduction. She also holds a master’s
degree from the University of Cambridge.
Dr. Løvås has, among other things, worked as a researcher andlecturer in energy technologies at Queen Mary University of
London and as a researcher at the University of Cambridge. She
has been a Fellow in Engineering at Churchill College, Cambridge.
Since 2009, Løvås has been a Professor and group leader for thethermal energy research group at the Department of Energy andProcess Engineering at the Norwegian University of Science andTechnology, NTNU. Here, she has also extended her research
towards solid fuels. She has led several research projects onammonia and hydrogen combustion for marine applications inrecent years. In August 2017, Dr. Løvås took the position of Headof the Department of Energy and Process Engineering at NTNU.
She became the first female head in the department’s history.
Dr. Løvås has been teaching thermodynamics and combustion
science at various universities and has authored more than 90
peer-reviewed journal papers. She has participated in manycollaborative projects at the national and international levels.
She is a member of the Board of Directors of the Combustion
Institute and has been joint Editor of the Proceedings of the
Combustion Institute since 2020. From 2011-2017, she waspresident of the Scandinavian Nordic section at the international
research community Combustion Institute, and from 20152023, she took over as president of the Federation of European
sections of the same research community. She is a board
member of the Swedish national research program and strategic
research center CECOST, Center for Combustion Science andTechnology. In addition, she was a board member for thenational infrastructure provider for computational science in
Norway UNINETT Sigma2 AS.

3Invited Speaker
Matthias Ihme

Stanford University, USA

Machine-learning for Combustion:
Opportunities and Challenges

Abstract

Short Biography

Combustion and energy conversion play critical roles in all

Matthias Ihme is Professor in the Department of Mechanicalincluding the utilization of sustainable energy sources for

Sciences at SLAC National Accelerator Laboratory. He holds

facets of environmental and technological applications,power-generation, the mitigation of harm from wildfire hazards,
or the reductions of emissions from furnaces and industrial

processing systems. Computational and mathematical tools

have long been crucial in combustion research in the formof high-fidelity simulations, dynamical-system modeling,
and data analytics. With the advent of data-driven methods,

machine learning (ML) offers numerous new opportunities forpredictive modeling, improving existing research methods,

and extracting new knowledge from data. In this presentation,
we discuss recent progress on how ML can impact the fieldof combustion and energy conversion and discuss the needfor injection physical principle and domain knowledge forEngineering at Stanford and the Department of Photona BSc. degree in Mechanical Engineering, a MSc. degreein Computational Engineering, and a Ph.D. in MechanicalEngineering. His research interests are broadly on thecomputational modeling of reacting flows, the development of

numerical methods, and the investigation of advanced energy

conversion concepts and molecular processes. He is a recipientof the NSF CAREER Award (2009), the ONR Young InvestigatorAward (2010), the AFOSR Young Investigator Award (2010),
the NASA Early Career Faculty Award (2015), the Hiroshi Tsuji

Early Career Research Award (2017), and the Bessel Award of
Alexander von Humboldt Foundation (2021).

successful machine-learning application in combustion.
Specifically, instead of image and textual data seen in many

ML applications, combustion ML learns from data extracted
from large-scale simulations, high-resolution experiments, andsensors, which can introduce challenges tied to dimensionality,

sparsity, and scarcity. Here, domain knowledge and expertisecan help alleviate these challenges, with the additional benefit
of introducing physical constraints seen in real-world problems.
We discuss these knowledge-guided strategies and further

requirements in combustion ML linked to interpretability,

uncertainty quantification, robustness, consistency, andbenchmark datasets.

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19th International Conference on Numerical Combustion

Invited Speaker
Epaminondas Mastorakos
University of Cambridge, UK

Advances in Simulations of Dual-fuelCombustion

Abstract

Short Biography

In this talk, the Doubly-Conditioned Moment Closure sub-Epaminondas Mastorakos is the Hopkinson/ICI Professor ofcontext of recent simulations of lifted spray flames, dual-fuelUniversity of Cambridge. He joined Cambridge in 2000 after

grid combustion model is presented and discussed in the
swirl flames, and diesel-ignited ammonia flames. The seminar
discusses the strengths and limitations of the approach andincludes a review of salient features of dual-fuel flames and thechallenges associated with their modelling. Comparison withother modelling approaches for this problem is attempted.

Applied Thermodynamics at the Engineering Department,

education at Imperial College and Cornell University and post-

doctoral appointments in Keio University (Yokohama, Japan),
Institut Francais du Petrole (Paris, France), and the Institute forHigh Temperature Process (Patras, Greece).

He has experience with fuels, energy, combustion, atmosphericchemistry, aerosols, the fluid mechanics of shale oil and gas,forest fires, and energy systems for aviation and shipping. His
lab has received funding from industry, the EU, Singapore’s

NRF and UK’s EPSRC on a range of topics, with significant

activity on gas turbine and diesel engine combustion, andaviation and shipping decarbonisation. He is currently the
Combustion Research Coordinator in the Rolls-Royce /Cambridge University Gas Turbine Partnership. His papers

have received numerous prizes from the Combustion Instituteand the American Society of Mechanical Engineers and he has

been elected Fellow of the Combustion Institute (2018), Fellowof the UK Institute of Mechanical Engineers (2019), and Fellowof the Royal Academy of Engineering (2022).

Concerning numerical combustion, he has focused his work on
implementing the Conditional Moment Closure and its variants
to LES of various flames of practical relevance such as gas
turbine combustors.

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MS01 Reaction Kinetics of Carbon-Neutral Fuels
Organizers: Akira Miyoshi1, Yasuyuki Sakai2
1

Hiroshima University, 2Ibaraki University

MS01 Reaction Kinetics ofCarbon-Neutral Fuels
Chair: Akira Miyoshi
Co-Chair: Yasuyuki Sakai
Wednesday, May 8; 15:30 - 16:50; Room J

Combustion Properties of Alcohol Fuels
Akira Miyoshi

Hiroshima University, Japan

In order to achieve the carbon-neutral society, ourenergy sources should shift toward biofuel and synthetic
fuels. Alcohols, methanol and ethanol, are the promisingalternative fuels for gasoline either by neat fuel or dropin fuels for existing petroleum fuels. Using their chemical
kinetic models, anti-knock properties and laminar burning
velocities has been well confirmed. In the present study,
the extinction flame stretch, which largely determines thelean limit of the SI super lean combustion and ignition
problems at cold start, has been extensively investigatedby the numerical simulation of counter-propagating premixed flame and nitrogen stream. The non-additive anti-knock effect (octane hyper-boost) of ethanol to alkanes
has been also investigated by the autoignition simulations.
Contact: akiramys@hiroshima-u.ac.jp

Development of High-Performance
Formula 1 Fuel Component and its
Carbon-Neutralization
Kohtarro Hashimoto
Honda R & D Co. Ltd., Japan

High-performance component of Formula 1 (F1) fuelwas developed using chemical reaction calculations.
Chemical reaction models of various hydrocarbons werecreated using KUCRS. Ignition timing of these hydrocarbons under the pressure conditions of the combustion
chamber of F1 engine were calculated using Ansys Chemkin. As the candidate for high performance components
having anti-knock properties was found, it has been used6

for F1 fuel component from 2019 Japan Grand Prix (GP).
Next, carbon-neutralization of this high-performance component was attempted. Renewable hydrogen and biomass
as carbon sources were used to produce e-methanol. In
addition to e-methanol, biochemical produced from second-generation biomass and chemicals were used to produce this high-performance component. As a result, thishigh-performance component was composed of 58.5% ofrenewable carbon. The F1 fuel mixed with this component
was used for in the 2021 Saudi Arabia GP and Abu Dhabi
GP for Honda’s power unit.
Contact: kohtaro_hashimoto@jp.honda

A Chemical Kinetic Study on the
Autoignition Mechanism of Ammonia/
hydrocarbon mixtures
Yasuyuki Sakai1, Takahiro Sako2, Sekai Miyamoto3,
Takahiro Yamaguchi3, Hisashi Nakamura4

Ibaraki University, Japan, 2Osaka Gas Co.,Ltd., Japan, 3Kawasaki Heavy
Industries, Ltd, Japan, 4Tohoku University, Japan1

The use of ammonia combustion is one way to contribute to the carbon neutralization of marine engines
and industrial furnaces. During the transition period fromhydrocarbon fuels derived from fossil resources to ammonia, various forms of ammonia combustion are envisioned
such as natural gas/ammonia, light oil/ammonia, heavy
oil/ammonia co-firing, and pure ammonia firing. The present study reports an analysis of the combustion reaction
mechanism of hydrocarbon/ammonia mixtures by using
a detailed chemical kinetics mechanism developed byauthors. Starting from the reaction mechanism of hydrocarbon mixtures (methane, ethane, propane, n-butane,
and isobutane), an ammonia combustion mechanism andmechanism of the intermediate species containing bothcarbon and nitrogen atoms (CN, HCN, CH2NH2, etc.) produced during the combustion of hydrocarbon/ammonia
mixture were added. The present mechanism includes 462
species and 2720 reactions. Ignition delay times and laminar flame velocities were used for the validations of ourmechanism. Ignitability is suppressed under both high andlow temperature conditions with increasing the amount ofammonia, however there is a region where ignitability of

19th International Conference on Numerical Combustion

MS01 Reaction Kinetics of Carbon-Neutral Fuels

ethane is enhanced at 60~90% ammonia mixture. A similar trend appears in the calculation results for methane/ammonia mixtures, but not for propane/ammonia and butane/ammonia mixtures. We will give the analysis of thesepromotion/suppression effects in the presentation.
Contact: yasuyuki.sakai.qr80@vc.ibaraki.ac.jp

Laminar burning velocity of ethanol/air
premixed flame under lean conditions

Yuki Ito, Kento Masui, Taku Mizutani, Hidefumi Kataoka,
Daisuke Segawa
Osaka Metropolitan University, Japan

Ethanol is derived from biomass and is a carbon-neutral fuel. The combustion experiments of ethanol/air
mixture under lean conditions were conducted using a
spherical combustion vessel. The laminar combustion
velocity was derived from the obtained pressure history.
Numerical calculations of a one-dimensional premixedethanol/air flame were performed using a detailed reaction mechanism. The calculated laminar burning velocity
was compared with the experimental results of laminarburning velocity.
Contact: hkataoka@omu.ac.jp

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MS02 Direct numerical simulations, analysis, andmodeling of premixed hydrogen flames
Organizers: Heinz Pitsch1, Mamoru Tanahashi2, Andrew Aspden3, Martin Rieth4, Michael Gauding1
RWTH Aachen University, 2Tokyo Institute of Technology, 3Newcastle University, 4Sandia National Laboratories

1

MS02-1 Direct numericalsimulations, analysis, andmodeling of premixed hydrogen
flames (1)Chair: Thomas Howarth
Friday, May 10; 09:50 - 11:50; Room K

Thermodiffusively-unstable leanpremixed hydrogen flames: Lengthscale effects and turbulent flame speed
modelling
E. F. Hunt, A. J. Aspden

Newcastle University, United Kingdom

Burning hydrogen in a lean premixed mode can control high flame speeds, temperatures and emissions, but
can result in thermodiffusively-unstable flames. Recent
work [CNF111805] has demonstrated that two-dimensional freely-propagating flames can be well characterised with a stability parameter that arises from classicalstability analysis [JFM489p179], and was then extended
to three-dimensional freely-propagating and turbulent
flames [CNF112811]. These two studies were restricted torelatively-small length scales. The present paper considers the influence of domain and integral length scales on
local and global flame behaviour across a broad range ofreactant (i.e. temperatures and pressures) and turbulence
conditions (i.e. Karlovitz and Damkohler numbers). The
general local flame behaviour (and moreover the local
flame speed model from [CNF112811]) is demonstrated to
be independent of length scale at a fixed Karlovitz number. Consequently, once thermodiffusive effects on thelocal flame speed have been accounted for, turbulent
flame speeds are determined solely by flame surface area
enhancement. A range of turbulent flame speed models
are compared with the present simulation data and thosein [CNF112811]. Limitations were found when evaluating
turbulent flame speeds in the small domains inherent to
DNS, which can be misinterpreted as “the bending effect".
Comparisons are made varying fuel Lewis number from8

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0.35 to 2.0, which demonstrate contrasting behaviour,both locally (i.e. local flame speed and curvature dependence) and globally (i.e. flame surface area enhancement).
Finally, consequences for the turbulent premixed regime
diagram are discussed.
Contact: andrew.aspden@ncl.ac.uk

DNS of a hydrogen flame interactingwith homogeneous isotropic turbulence
maintained by a deterministic force

Yifan Xu1, Jian Fang2, Zhen Lu1, Xiaojun Gu2, Zhi X. Chen1

1
Peking University, China, 2Science and Technology Facilities Council,
United Kingdom

Studying the interplay between a hydrogen flame andturbulence is crucial for the advancement of next-generation carbon-neutral combustion systems. In our present
work, we conduct a series of direct numerical simulations(DNS) to investigate the dynamics of a premixed hydrogen
flame interacting with the compressible homogeneous
isotropic turbulence (HIT) maintained by a deterministic
force under different pressure and turbulence intensity.
Under this particular forcing method applied to turbulence at large scales, the relationship between the forcing
intensity and the resulting fluctuating velocity aligns wellwith the experimental results. In our study, we compare
the statistics of turbulent burning velocity of hydrogen
flames under different conditions and verify the common
occurrence of bending effects at elevated pressures. To
further explore the dynamics of the HIT-flame interaction
and fully leverage the advantages of high-precision direct
numerical simulations, we analyse several flame behaviours such as stretch and instability, as well as higher-order turbulence statistics such as skewness. The probability density function (PDF) for the tangential strain rate andcurvature are displayed and the results indicate a strong
correlation between the flame surface structure and theturbulence generated by the large-scale forcing.
Contact: yifanxu@pku.edu.cn

19th International Conference on Numerical Combustion

MS02 Direct numerical simulations, analysis, and modeling of premixed hydrogen flames

Effects of Reynolds number onthermodiffusive flame instabilities:
Direct numerical simulations of turbulent
lean hydrogen jet flamesMichael Gauding, Thomas Howarth, Lukas Berger,
Heinz Pitsch
RWTH Aachen University, Germany

Lean premixed hydrogen/air flames are significantly
affected by thermodiffusive instabilities. These originate
from the disparity between heat and mass fluxes due tothe low Lewis number of hydrogen and lead to significantly increased burning velocities. In turbulent flames, theseeffects persist and are even further amplified by synergistic interactions among turbulence and thermodiffusive
instabilities.
In this work, the dependence of these synergistic interactions on the Reynolds number is quantitatively assessed via direct numerical simulations (DNS) of premixedhydrogen/air jet flames utilizing finite rate chemistry in aslot burner configuration. A fixed reactant condition is employed (equivalence ratio of 0.4, 1 bar, 298 K) and the jet
slot width is increased to vary the jet Reynolds numbers
between 5,500 and 22,000 while keeping the Karlovitz
number constant. Global and surface-local statistics are
retrieved to characterize the jet and turbulence-flame
interaction. The dependence of thermodiffusive instabilities on the jet Reynolds number is analyzed through local
curvature, strain and stretch rate, and flame morphology.
Variations of the local reactivity, which are linked to thefluctuations of equivalence ratio, are analyzed. Strain
effects are assessed by comparison with laminar counterflow flamelets.
Contact: m.gauding@itv.rwth-aachen.de

Direct Numerical Simulation of a LeanPremixed Turbulent Swirling Hydrogen
Flame
Abhishek Lakshman Pillai1, Umair Ahmed2, Nilanjan
Chakraborty2, Ryoichi Kurose1
1

Kyoto University, Japan, 2Newcastle University, United Kingdom

This study presents an analysis of turbulent combustion in an actual laboratory-scale lean-premixed (equivalence ratio = 0.45) low-swirl hydrogen flame using Direct
Numerical Simulation (DNS). This lean-premixed hydrogen
flame is stabilized using a Low-Swirl Burner (LSB) witha swirl number = 0.39. The DNS incorporates detailed
chemical kinetics for hydrogen combustion and the differential diffusion of chemical species is considered by computing their respective diffusion velocities from the Max-well-Stefan equation. The DNS domain is discretized by a
non-uniform Cartesian grid with nearly 6 Billion grid points
and is executed on the supercomputer Fugaku (RIKEN
Japan) using 200,000 cores. Interrogation of the generated DNS database reveals that differential diffusion ofreactants influences the local flame structure and causes
the occurrence of localized super-adiabatic temperatures.
While combustion is found to occur predominantly in thelean-premixed mode, some local regions of non-premixed
combustion are found in the shear layers owing to mixture
inhomogeneities arising from mixing and stratification
effects in the hydrogen flame’s swirling turbulent shear
layers. Additionally, the DNS database is used to analyze
the flame structure and the statistical behaviors of various
quantities such as the mixture fraction, progress variable,temperature, chemical species concentrations, and surface density function in detail.
Contact: pillai.abhisheklakshman.2e@kyoto-u.ac.jp

DNS study of turbulent boundary layer
flashback in parallel channel for leanhydrogen-air premixed flame

Reo Kai1, Kotaro Yada2, Kazuhiro Kinuta2, Hiroaki
Watanabe1, Ryoichi Kurose2
1

Kyushu University, Japan, 2Kyoto University, JapanTo develop a stable hydrogen-fueled combustor with
low NOx emissions, preventing and understanding the
flashback of a lean hydrogen-air premixed flame is oneof the most challenging. This study focuses on the flashback in the vicinity of the wall, namely the boundary layer
flashback. To elucidate the mechanism of flashback of alean hydrogen-air premixed flame in a turbulent boundary
layer, a direct numerical simulation of turbulent boundary
layer flashback in parallel channel for a lean hydrogen-air
premixed flame at an equivalence ratio of 0.5, an unburnt
gas temperature of 750 K, a pressure of 1 atm, and afriction Reynolds number of 180 is performed employing a detailed chemical reaction mechanism including 9
chemical species and 19 chemical reactions. The obtained
results are analyzed to investigate the contributions offlame-flow interaction, flame-flame interaction, local
equivalence ratio distribution, and thermal diffusive instability on the flashback behavior, such as flashback speed.
Contact: reokai@tse.kyushu-u.ac.jp

9MS02 Direct numerical simulations, analysis, and modeling of premixed hydrogen flames

MS02-2 Direct numericalsimulations, analysis, andmodeling of premixed hydrogen
flames (2)DNS of a laboratory lean CH4/H2
low-swirl flame impinging on an inclined
wall
Mohammadreza Nozari1, Olivier Chabot1, Sandeep Jella2,
Martin Vabre1, Luming Fan3, Marc Day4, Patrizio Vena3,
Lucas Esclapez5, Bruno Savard1

Polytechnique Montréal, Canada, 2Siemens Energy Canada Limited,
Canada, 3National Research Council Canada, Canada, 4National Renewable
Energy Laboratory, Canada, 5National Renewable Energy Laboratory,
United States

Chair: Martin Rieth
Friday, May 10; 13:00 - 15:00; Room K

1

Direct numerical simulation of a lean swirling premixed
H2/CH4 flame impinging on an inclined isothermal wall is
performed. The case simulated is a laboratory flame with
Reynolds number of 20,000 and Karlovitz number of 300.
The fuel/air mixture consists of 70% hydrogen and 30%
methane with equivalence ratio of 0.41. The simulation
results are compared with experimental results from OHxCH2O PLIF and stereo-PIV measurements. Consistently,
the flame features a bowl-shape stabilization, with a corrugated, continuous flame front at the leading edge, followed by highly fragmented reaction zones downstream.
A remarkably large cloud of CH2O and CO is formed
downstream of the quenching point, also observed experimentally. The simulation results indicate that the cloudis the result of incomplete methane combustion causedby the stabilization of ultra-lean H2/CH4 reaction zones
in strong shear layers. These reaction zones can sustain
mean strain rates significantly larger than the 1D extinction strain rate. The role of wall heat loss on the flamestabilization and flame structure in phase space is alsopresented.
Contact: bruno.savard@polymtl.ca

DNS on flame structure and species
distribution of a partially premixed steamdiluted oxygen/hydrogen combustion
with inclining impinging jets geometry
Shan Jiang1, Ye Wang1, Masayasu Shimura2, Mamoru
Tanahashi1

Tokyo Institute of Technology, Japan, 2National Institute of Advanced
Industrial Science and Technology, Japan1

We conducted direct numerical simulations (DNSs) toinvestigate the flame structure, mixing properties as well
as distribution of chemical species in a partially premixed
steam-diluted oxygen/hydrogen combustion with inclining
impinging jets geometry. It was found that the distance
between jet nozzle groups poses significant influences byenhancing the interaction between neighboring flow fields
and flame in the upstream region. Specifically, closer proximity of nozzle groups corresponds to a more extensive
concentration of hydrogen upstream, along with a more
intense recirculation in the domain between hydrogennozzles. The upstream concentration of hydrogen may
be attributed to the recirculation domain continuouslytransporting unburnt gases upstream. Furthermore, we
observed that under smaller hydrogen nozzle spacings,
the flames from adjacent groups of nozzles merges together and tends to be closer to the upstream region.
Additionally, analysis using the Normalized Flame Index(NFI) revealed that the typical triple flame structure wasno longer present under shorter nozzle group distances.
The mixture in both premixed and non-premixed modes
is more fragmented and distributed near the jet impinging
points in the upstream part, compared to cases with larger nozzle group distances.
Contact: jiang.s.ae@m.titech.ac.jp

Near-wall dynamics of V-shape hydrogenair flame in a turbulent channel flow
Ye Wang, Mamoru Tanahashi
Tokyo Institute of Technology, JapanThe correlation between three-dimensional geometricstructure and near-wall dynamics of turbulent hydrogen
flame has been studied using direct numerical simulation10

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19th International Conference on Numerical Combustion

MS02 Direct numerical simulations, analysis, and modeling of premixed hydrogen flames

with detailed chemistry, considering the V-shape flame ina turbulent channel flow. The principal curvatures (k1, k2)
and the local fuel consumption speed of each flame element are evaluated. The results show that, the influenceof the wall is predominant in shaping the flame geometry
in the buffer layer and viscus sublayer of near-wall turbulence, resulting in near-wall flames that are primarily cylindrical and convex towards either the burned or unburnedside. Additionally, it is found that the local fuel consumption speed is not solely reliant on the flame's mean curvature but also on its principal curvatures: flame elementswith identical mean curvature values but larger differences between k1 and k2 statistically exhibit higher fuelconsumption speeds. This is different from the previous
findings of the turbulent flame free of wall. The current
study highlights the critical role of the three-dimensional
geometry and principal curvatures to the near-wall flame
reactions and proportions, which should be considered in
the future modelling of near-wall turbulent premixed hydrogen combustion.
Contact: wang.y.by@m.titech.ac.jp

Inducing Spiky Flame Fronts in Lean
Hydrogen Flames through Expansion
Waves
Samir Boset Rojas Chavez1, Hongxia Yang2, Kevin
Cheevers2, Deanna Lacoste1, Matei Radulescu2
1

King Abdullah University of Science and Technology, Saudi Arabia,
University of Ottawa, Canada

2

Hydrogen lean flames exhibit a fractal-like propagation,
where larger cells encompass smaller, similar cells within
the flame front. This structure results in cell intersections leaving behind funnels of unburned gases. Recent
studies have highlighted the role of expansion waves ineither accelerating burning velocity or quenching flames,
depending on the expansion ratio and the wave's propagation direction relative to the flame (i.e., from burned
to fresh gases or vice versa). Our study explores a novel
effect of expansion waves on lean hydrogen-air flames(φ=0.3). We employed reactive Navier-Stokes equations ina two-dimensional domain, supplemented by cylindrical
Hele-Shaw configuration experiments. A central shocktube in the Hele-Shaw setup generates expansion waves
moving from burned to fresh gases. Our findings reveal an
immediate cell flipping post-expansion wave interaction,
followed by a distorted, spiky flame front formed by the
combination of cell flipping and unburned gas funnels.
Contact: samirboset.rojaschavez@kaust.edu.saOn the behaviour of Reynolds stresses
and their dissipation rates during
boundary layer flashback of a richhydrogen-air premixed flame within aturbulent channel flow

Umair Ahmed1, Abhishek Pillai2, Nilanjan Chakraborty3,
Ryoichi Kurose4
1

Newcastle Univeristy, United Kingdom, 2Kyoto University, Japan,
Newcastle University, United Kingdom, 4Kyoto Univeristy, Japan

3

A Direct Numerical Simulation (DNS) database forboundary layer flashback of hydrogen-air premixed flamein a turbulent channel flow has been utilised to investigate
the interrelation between Reynolds stresses and their dissipation rates. The Reynolds stresses and their dissipation
rates have been found to exhibit significant deviations
during boundary layer flashback when compared with thecorresponding non-reacting flow. The anisotropy of Reynolds stresses and their dissipation rate tensors are foundto be qualitatively similar. However, the components of
the anisotropy tensors of Reynolds stress and viscous dissipation rate are not related according to a linear scaling,hence the models based on this assumption are not successful in capturing the viscous dissipation rate components obtained from the DNS data. By contrast, a model,
which includes the invariants of the anisotropy tensor of
Reynolds stresses and satisfies the limiting conditions for
isotropy and 2-component limit captures the componentsof the viscous dissipation rate tensor more successfully
for both non-reacting and reacting cases. Therefore, thismodel can be used for approximating the dissipation
rate tensor in the Reynolds stress transport equation in
the context of hybrid Reynolds Averaged Navier-Stokes/
Large Eddy Simulation modelling strategies.
Contact: umair.ahmed@newcastle.ac.uk

Impact of the Soret Effect on the
Thermodiffusive Instability in Hydrogen
FlamesSofiane Al Kassar1, Ollie Moore1, William Lauder1, Lukas
Berger2, Heinz Pitsch2, Antonio Attili1

The University of Edinburgh, United Kingdom, 2RWTH Aachen University,
Germany

1

Lean premixed hydrogen flames are prone to thermodiffusive instabilities, which originate from the differential diffusion between hydrogen and other species. The
Soret effect, often called thermodiffusion, could play arole in augmenting differential diffusion due to thermal
gradients. This study explores its impact on thermodiffusive instabilities in premixed flames at different pressure
and temperatures, in both the linear and non-linear re-11

MS02 Direct numerical simulations, analysis, and modeling of premixed hydrogen flames

gimes, via Direct Numerical Simulations with finite ratechemistry and detailed transport models. Various blendsof hydrogen and methane are considered to discern thevarious effects.
In the linear phase, initially planar flames are exposed
to weak multi-wavelength perturbations, allowing for theexamination of growth rates for each harmonic. In the
non-linear phase, a fully developed regime is achieved,
and the characteristics of the complex and multiscale cellular structures emerging from the instability are analysed.
In addition, the enhancement of the flame speed due tothe instability is investigated.
The results reveal a gradual reduction in the influenceof the Soret effect with increasing pressure and temperature. At ambient conditions, the Soret effect enhances
differential diffusion effects, playing a significant role inthe development of the thermodiffusive instability, while
its impact is negligible at a pressure of 20 atmospheres.
Contact: s2337719@ed.ac.uk

Analysis of thermodiffusive fluxes inhydrogen premixed flames using flamelet
generated manifolds
Emiliano M. Fortes1, Eduardo J. Pérez-Sánchez1, Ambrus
Both1, Temistocle Grenga2, Daniel Mira1

Barcelona Supercomputing Center , Spain, 2University of Southampton,
United Kingdom

1

The development of reduced-order models is of paramount importance to reduce the computational costassociated with the chemical effects involved in reacting
flow simulations. In particular, tabulated chemistry methods in the context of flamelet generated manifolds, haveshown high potential to reproduce complex flow conditions from gaseous to spray flames with a high level ofaccuracy and reliability. In this study, an extension of thismethod to include detailed transport phenomena basedon a mixture-average model is presented to describe theformation of thermodiffusive instabilities in hydrogen premixed flames. A dedicated analysis of the coupling terms
involved in the thermodiffusive transport is performed
and their weights across the flame front are examined tounderstand the contributions from each control variable
to the global thermodiffusive balance. In addition, themodeling capability of the flamelet generated manifolds
method is assessed with respect to the grid size and thestrength of the thermodiffusive transport determined by
the flow conditions.

MS02-3 Direct numericalsimulations, analysis, andmodeling of premixed hydrogen
flames (3)Chair: Michael Gauding
Friday, May 10; 15:20 - 17:40; Room K

Data-driven modeling of thermodiffusively unstable hydrogen-air flames
Pasquale Eduardo Lapenna1, Arianna Remiddi1,
Francesco D'Alessio1, Guido Troiani2, Francesco Creta1

1

Sapienza University of Rome , Italy, 2ENEA Research Center, Italy

State-of-the-art turbulent combustion models do notinclude the possible impact of thermo-diffusive instabilities, which have been shown theoretically, numerically,and experimentally to have a significant role in leanhydrogen premixed flames. In this contribution, we leverage variable fidelity data from both simulations andexperiments to address the modeling of thermodiffusive
unstable flames. The main idea is to develop a data-driven
framework capable of reproducing the structure and propagation of unstable flames in both laminar and turbulent
settings. This is done by resorting to the optimal estimator
concept while using small- to medium-scale two-dimensional simulations of cellular hydrogen flames to generate
tabulated thermochemical manifolds. Then the large eddy
simulation (LES) sub-filter terms are closed using the Filtered-Tabulated-Chemistry-LES (FTACLES) formalism. The
reference data are therefore filtered in the physical spaceand stored as a function of a properly defined set of filtered progress variables. A-priori and a-posteriori testingof the proposed framework is presented and discussed
for laminar unstable flames. Then the inclusion of turbulent effects is discussed by means of the definition of awrinkling factor term derived from both experiments andadditional simulations. The modeling role of the synergistic interaction between turbulence and thermodiffusive
instability is also discussed.
Contact: pasquale.lapenna@uniroma1.it

Contact: daniel.mira@bsc.es

12

19th International Conference on Numerical Combustion

MS02 Direct numerical simulations, analysis, and modeling of premixed hydrogen flames

Modelling of Turbulent Boundary Layer
Flashback of a Lean Premixed Hydrogen
Flame with Large Eddy Simulation and
Flamelet Generated Manifolds Including
Preferential Diffusion

Stijn Schepers, Rob Bastiaans, Roy Hermanns, Jeroen van
Oijen
Eindhoven University of Technology, Netherlands

The high burning velocity and high diffusivity of hydrogen result in unwanted phenomena like flame flashbackin combustion systems running on hydrogen. Especiallyin gas turbines, boundary layer flashback seems to be
the prominent flashback mechanism, and accurate andefficient models are necessary to predict this unwanted
phenomenon. In this research, a CFD combustion model
is developed to investigate flame flashback in a turbulent boundary layer. The chemistry is reduced using theFlamelet Generated Manifold (FGM) method and extended
to account for the large preferential diffusion effects ofhydrogen. Turbulence is modeled using Large Eddy Simulation (LES), and the turbulence-chemistry interaction
is modeled using a presumed beta probability density
function (PDF). This FGM-LES tool is applied to a turbulent
channel flow filled with a lean premixed hydrogen-air mixture. Initially, a cold flow simulation is performed to ensurea fully developed turbulent flow and the results are compared to DNS data reported in literature. Subsequently, apart of the domain is ignited to investigate flame propagation in the turbulent boundary layer. The FGM-LES tool isvalidated against DNS and experimental data of boundary
layer flashback in similar turbulent channels reported in
the literature. It is assessed if the preferential diffusion
model in the FGM-LES tool captures thermodiffusive
instabilities with sufficient accuracy and if the expectedboundary separation zone is visible. Subsequently, the validated FGM-LES tool is used to study the influence of thewall temperature on the flashback behavior.
Contact: s.n.j.schepers@tue.nl

Flamelet Generated Manifolds for leanpremixed turbulent hydrogen flamesGabriela Sanchez, Jeroen van Oijen

Eindhoven University of Technology, Netherlands

The interest in developing models that can predict hydrogen combustion is continuously increasing. Hydrogenis a carbon-free alternative fuel; however, its high diffusivity leads to strong wrinkling of the flame and fluctuationsof elements mass fractions and enthalpy along the flame
front due to preferential diffusion. In this study, we investi-gate how the Flamelet Generated Manifold technique canbe applied to model these phenomena. We performed
Direct Numerical Simulations (DNS) of two cases withdetailed chemistry and different Reynolds numbers. Then,
we built several manifolds varying different parameters,such as equivalence ratio, temperature and heat releaserate, in order to account for fluctuations caused by preferential diffusion. With these manifolds, we predicted
species mass fractions and source terms, and we compared them to the DNS. For both cases, we found that
two-dimensional manifolds with equivalence ratio fluctuations are sufficient to predict the main species massfractions; however, it was necessary to add enthalpy as
an independent variable to predict radicals mass fractions
and source terms accurately. These results represent anadvance in the development of a model for lean turbulent
hydrogen combustion, further facilitating the executionof simulations of hydrogen flames in complex geometries
such as gas turbines.
Contact: g.e.sanchez.bahoque@tue.nl

Filtered tabulated chemistry for multiregime hydrogen combustion
Samuel Dillon1, Renaud Mercier2, Benoît Fiorina1
1

EM2C Laboratory, CNRS, CentraleSupélec, Université Paris-Saclay, France,
Safran Tech, Digital Sciences & Technologies Department, France

2

Hydrogen represents a potential solution for the decarbonization of the aviation industry, however, new challenges arise due to transport and thermochemical properties which differ from conventional fuels. In practicalapplications, pure premixed injection is usually avoided tolimit flashback propensity and both diffusion and partially-premixed flame structures, often stabilised by swirled
injectors, are frequently observed in emerging burner designs. Multi-regime flamelet-type approaches for LES are
popular due to their low cost, however, these approaches
pose two key challenges: 1.) Correct distinction between
combustion regimes and 2.) Coupling with the LES, where
flame structures are unresolved at the mesh scale. The
F-TACLES (Filtered tabulated chemistry for LES) model
which couples tabulated chemistry with LES using thefiltering approach, has been recently extended to accountfor multi-regime combustion by incorporating filtered
1-D partially-premixed flamelets. The distinction between
combustion regimes is accounted for by the inclusion of
the resolved scalar dissipation rate as a tabulation coordinate. This model is tested on the 3-D turbulent coaxial
HYLON (Hydrogen Low-NOx) injector developed at IMFT
in Toulouse. This configuration has two operating conditions, an attached flame (A) and a lifted partially-premixed
flame (L). Both the attached and lifted partially-premixed

13

MS02 Direct numerical simulations, analysis, and modeling of premixed hydrogen flames

flames are investigated and compared against mono-archetype F-TACLES models.
Contact: samuel.dillon@centralesupelec.fr

Manifold-based modeling for differential
diffusion in turbulent premixed leanhydrogen flamesKatie VanderKam, Sydney Rzepka, Michael E Mueller
Princeton University, United States

Premixed lean hydrogen flames are subject to thermodiffusive instabilities induced by differential diffusion
effects, and understanding and predicting differential diffusion and its effects on flame propagation and emissions
are imperative for the widespread adoption of alternativehydrogen-based fuels. Manifold-based combustion models are attractive for reducing the computational cost of
simulating turbulent reacting flows. While these models
are often derived assuming unity effective Lewis numbers,
one-dimensional manifold equations in progress variablefor premixed combustion can be derived without suchan assumption and are parameterized by the progress
variable dissipation rate and curvature. This work will
investigate how fluctuations in the progress variable dissipation rate and curvature influence both local and global
flame behavior as well as manifold model performance.
To study these phenomena, detailed simulations havebeen conducted for laminar and turbulent premixed leanhydrogen flames. The manifold model was evaluated both
statistically and instantaneously against the simulation
data. The results demonstrate how fluctuations in the
progress variable dissipation rate and curvature influence
flame structure and how each should be treated from amanifold modeling standpoint.
Contact: kev2@princeton.edu

Response of two-dimensional leanhydrogen-air laminar premixed flames toacoustic oscillations
Frederick William Young, Umair Ahmed, Nilanjan
Chakraborty
Newcastle University, United Kingdom

The response of two-dimensional lean hydrogen-air
laminar premixed flames to acoustic oscillations has been
analysed. Simulations for two equivalence ratios of 0.4
and 0.7 have been performed, to gain insights into thethermoacoustic response of lean hydrogen-air flames,
which are prone to thermo-diffusive instabilities. The
initially flat planar laminar flames have been subjected14

to acoustic oscillations representative of different soundpressure levels (SPL) to observe how acoustic waves influence the onset of flame wrinkling which triggers the thermo-diffusive effects induced by sub-unity Lewis number tofurther perturb the flame surface. It has been found thatthe flame response is sensitive to the strength of the imposed acoustic oscillation with different corrugation wavelengths observed on the flame surface for different soundpressure levels. The influence of equivalence ratio on thethermoacoustic response of the flames and the impact on
the observed flame corrugations has also been assessed.
Dispersion relations relating the perturbation growth rates
to the flame surface corrugation wavelengths have beenobtained and the effect of varying the frequency of imposed acoustic oscillation on the response of the flames
has also been explored.
Contact: f.young3@newcastle.ac.uk

Propagation characteristics of leanturbulent premixed ammonia-hydrogen
flamesRuslan Khamedov, Mohammad Rafi Malik, Francisco E.
Hernández Pérez, Hong G. Im
King Abdullah University of Science and Technology, Saudi Arabia

Given the widespread interest in carbon neutrality,
ammonia represents a potential energy carrier withoutcarbon dioxide emissions. To obtain fundamental insights
into the propagation and flame structural characteristics
of fuel-lean turbulent premixed NH3-H2-N2-air flames in
the presence of turbulence, three-dimensional direct numerical simulations are carried out with complex chemistry. In particular, we consider three mixtures with different
levels of H2 ratio, specifically NH3-air, 60%NH3-25%H215%N2-air, and 40%NH3-45%H2-15%N2-air under fixedvelocity and length ratios. To comprehensively assess theimpact of diffusive-thermal imbalances on hydrogen-enriched ammonia flames, additional solutions with unity-Lewis-number transport were analyzed and comparedwith those obtained using the mixture-averaged transportmodel. The increase of H2 fraction in the fuel leads toelevated mean turbulent flame speed and stretch factor,
indicating the impact of thermal-diffusive instability. The
turbulent flame speed of the 60%NH3-25%H2-15%N2air flame displays pronounced oscillations, a phenomenon
absent in other mixtures considered in the current study.
This behavior is attributed to the preferential diffusion ofH2 mixed with the low-reactive NH3 in moderate quantities, resulting in a higher generation of flame elements
extending into the product side and dynamic evolution of
H2. The flame structure analysis, in terms of conditional
averages, revealed a distinctive variation in H2 and H

19th International Conference on Numerical Combustion

MS02 Direct numerical simulations, analysis, and modeling of premixed hydrogen flames

atom distributions. The flames with a higher H2 fraction(40%NH3-45%H2-15%N2-air) produced a second peak of
H2O2 in the trailing edge region, indicating additional production in the intense reaction zone. Additionally, in the
60%NH3-25%H2-15%N2-air flame, the reaction rate of H2
exhibited a unique behavior, with H2 being produced in
the intermediate flame zone and rapidly consumed in thereaction zone, differing from other cases.
Contact: ruslan.khamedov@kaust.edu.sa



15

MS03 Combustion Noise and Thermoacoustic
Instabilities
Organizers: Abhishek Lakshman Pillai1, Matthias Ihme2, Ryoichi Kurose1
1

Kyoto University, 2Stanford University

MS03-1 Combustion Noise andThermoacoustic Instabilities (1)Chair: Abhishek Lakshman Pillai
Co-Chair: Matthias Ihme
Friday, May 10; 13:00 - 15:00; Room C

A Hybrid CFD/CAA Solver for Simulating
Noise Generation in Real Fluid Flows
under Transcritical and Supercritical
Conditions

Abhishek Lakshman Pillai, Takuto Yamada, Sho Wada,
Ryoichi Kurose
Kyoto University, Japan

Turbulent real fluid flows are encountered in thehigh-pressure combustors of supercritical gas turbine
engines which offer the advantage of high thermal efficiency. However, reacting real fluid flows are also capableof generating significant noise whose mechanisms andcharacteristics remain to be fully understood. This work
presents a hybrid CFD/CAA solver that considers real gas
effects for simulating real fluid flows and describes thegeneration and radiation of noise from them. In this hybrid
solver, Large-Eddy Simulation (LES) predicts the turbulent
flow field, and the Linearized Euler Equations (LEE) aresolved in the CAA simulation to predict the acoustic field.
As a first step towards our future goal of applying thedeveloped solver to simulate noise generation in transcritical and supercritical combustion, two inert nitrogen jets,
one under transcritical (injected at cryogenic temperature)and the other under supercritical conditions, are simulated. Results show that the acoustic sources contributing
to the low-frequency noise are located closer to the endof the jets’ potential cores, while those contributing to
the high-frequency noise are located further upstream.
Furthermore, acoustic fields radiated by the transcritical
jet and the supercritical jet are characterized in terms ofnoise directivity and spectral content of sound pressures.
Contact: pillai.abhisheklakshman.2e@kyoto-u.ac.jp

16

What is the potential of next-generation
aviation gas turbine combustors for noise
reduction?

Matthias Ihme1, Davy Brouzet1, Benyamin Krisna1, Duane
McCormick2, C Aaron Reimann2, Jeff Mendoza2
Stanford University, United States, 2Raytheon Technologies ResearchCenter, United States

1

Aircraft noise is a major concern because of its adverse
effect on the quality of life, health, and property valueof communities in proximity to airports and flight corridors. Recent progress in the development of advanced
gas-turbine combustors offer opportunities to reducenoise emission. We present large-eddy simulations of anext-generation combustor and examine the emission of
the direct and indirect combustion-noise contributions. To
account for the complex geometry, a low-order acoustic
reconstruction technique is developed that is based on a
Green’s function approach. Comparisons with a conventional rich-quench-lean combustor configuration showthat that this advanced combustor concept has a direct
effect on the acoustics, which is attributed to two specifictechnological novelties, namely (i) the reduced residence
time due to compact combustor geometry and (ii) the
reduction of the entropy inhomogeneities due the absence of dilution. These results provide opportunities foradvanced combustion technologies to achieve substantial
reductions in combustion noise.
Contact: mihme@stanford.edu

Numerical Analysis of Thermodiffusive
Unstable Premixed Lean Hydrogen-Air
Slit Flames

Borja Pedro Beltran, Matthias Helmut Meinke, Wolfgang
Schroeder
RWTH Aachen University, Germany

Combustion noise appears in aero- and stationary gas
turbines as well as in industrial boilers and furnaces. The
acoustic modes generated by heat release fluctuations
can interact with the gas filled plenum chambers or ducts

19th International Conference on Numerical Combustion

MS03 Combustion Noise and Thermoacoustic Instabilities

and lead to large amplitude low-frequency vibrations.
These are generated by a dynamic feedback loop between
the acoustic waves and velocity fluctuations causing
flame front perturbations and thus heat release variations.
Recently, hydrogen has received increasing attention asa renewable energy source. An important aspect in thedevelopment of hydrogen combustors, in which pure hydrogen or hydrogen-enriched natural gas are burnt, is thesignificant change in thermoacoustic stability.
In this work, lean premixed, two-dimensional hydrogen-air slit flames are investigated by using highly resolved numerical simulations. The fuel-air-equivalence
ratio is varied and the impact on the general flame dynamics is investigated. For the various cases, intrinsic instabilities of the non-excited flame lead to strong cellular
structures along the flame front, which cause constantpocket shedding and strong pressure fluctuations at theflame tip. Due to Markstein-length related effects, intrinsic
differences are identified, when compared to methane-air
premixed flames. A detailed investigation of the generated thermoacoustic modes is performed by solving theacoustic perturbation equations, in which acoustic sources determined from the flow field solution are used. These
investigation enhance the understanding of the various
acoustic source contributions to the overall acoustic fieldof premixed hydrogen-air flames.
Contact: m.meinke@aia.rwth-aachen.de

Exploring the connection between
combustion noise and thermoacoustic
instability
Mohsen Talei1, Jenzen Ho1, Sandeep Jella2
1

The University of Melbourne, Australia, 2Siemens Energy Canada , Canada

Thermoacoustic instability, commonly initiated by
combustion noise is one of the challenges hampering
the development of cleaner gas turbines. This presentation will examine the link between combustion noise andthermoacoustic instability, using high-fidelity simulations
such as direct numerical simulation (DNS) and large-eddy
simulation (LES). The primary focus is on premixed flames,
exploring the fundamentals of combustion noise, soundsources in premixed flames, and their contributions acrossthe sound pressure level spectrum. The talk also examines the impact of hydrogen addition on sound generationin hydrogen/methane premixed flames, using results from
our DNS studies. In the subsequent section, findings from
LES of combustors fuelled with hydrogen/methane mixtures will be presented. The discussion will highlight theconnection between combustion noise and thermoacoustic instability, underlining its implications for modeling.
Finally, the presentation will offer insights into future directions for research, with a specific focus on enhancing



our predictive capabilities for thermoacoustic instability.
Contact: mohsen.talei@unimelb.edu.au

On the roles of spray response to pressure
oscillations in combustion instability in
a combustor with a lean-burn coaxiallystaged fuel injector
Kazuaki Matsuura1, Kodai Kato1, Riko Hosoi2, Yuta Sasaki2,
Yoshio Zama2, Takeshi Yamamoto1, Ryoichi Kurose3
1

Japan Aerospace Exploration Agency, Japan, 2Gunma University, Japan,
Kyoto University, Japan

3

Proper models on the fuel spray response to pressure
oscillations driven by combustion instabilities are crucial
to improve CFD. Fluctuation of fuel flow rate is especiallysignificant as it induces equivalence ratio oscillation. However, such models do not seem to be fully establishedyet. In some literatures, a simple quasi-steady model was
employed (Lieuwen and Zinn 1998 and Kato et al. 2008),
whereas in others, the employed models were not explicitly described sometimes. On the other hand, Pillai etal. (2020) performed “numerical” experiments by LES on
the effects of the artificially-introduced response delays,
showing their notable impacts.
In our talk, two relevant attempts, still in progress, areto be presented.
Firstly, to investigate the impacts of the response, asimilar approach to Pillai et al. was applied to a rectangular combustor equipped with a coaxially-staged lean burninjector. The results were compared with those similar to
Matsuura et al. (2015). The injector with optical access into
its pre-mixing duct provided information equivalent to fuelconcentration, which can be used for fulfilling CFD validations.
Secondly, by means of a siren facility with a crossflow
injection in a rectangular duct, the velocity inside its
injection hole was measured by PIV to investigate theresponse. The aim was a new empirical model. It in fact
showed deviation from the quasi-steady one. It was thenintroduced to the CFD above.
The numerical results on the quasi-steady response,
the numerical experiments and the empirical model are to
be presented and compared in our presentation.
Contact: matsuura.kazuaki@jaxa.jp

17MS03 Combustion Noise and Thermoacoustic Instabilities

High-frequency transverse combustion
instabilities of lean-premixed purehydrogen-air flames
Kyutae Kim

Korea Advanced Institute of Science and Technology, Korea

The present experimental investigation is concernedwith combustion dynamics of lean-premixed pure hydrogen-air flames. To mitigate flashback risk in relatively fast
premixed hydrogen flames, we use a multislit injector
assembly with a slit width of 1.5 mm, of the same orderof magnitude as the characteristic thickness of lean-premixed hydrogen flames. We carry out extensive measurements of self-excited pressure oscillations over a broad
range of operating conditions between 30 and 100 kW
thermal power. The experimental datasets are analyzed
using the acoustic wave decomposition method, low-order thermoacoustic network modeling, and FEM-based
three-dimensional Helmholtz simulations. We show thatlean-premixed multislit hydrogen flames undergo strong
high-frequency pressure oscillations between 3.1 and 3.5
kHz in excess of 25 kPa, originating from the triggering of
the first tangential mode of the combustion chamber. We
demonstrate that the transverse mode is characterizedby high-amplitude spinning modes in the clockwise direction under relatively short combustor length conditions,discontinuously switching to counter-clockwise spinningmodes at relatively long combustor length, and eventually transitioning to a moderate standing wave modeat the same resonant frequency. These observations
demonstrate the previously unidentified complex modal
dynamics induced by lean-premixed multislit hydrogen-air
flames.
Contact: kt_kim@kaist.ac.kr

MS03-2 Combustion Noise andThermoacoustic Instabilities (2)Chair: Abhishek Lakshman Pillai
Co-Chair: Matthias Ihme
Friday, May 10; 15:20 - 17:20; Room C

Modeling Considerations for Combustion
Dynamics ROM Tools
Vishal Acharya

Georgia Institute of Technology, United States

Gas Turbine combustion systems operate in a varietyof combustion paradigms ranging from premixed to gaseous diffusion to spray flames. In each of these cases, com-18

bustion instabilities occur with varying levels of propensity. During these instabilities, the unsteady heat release
rate oscillations couples with one or more of the natural
acoustic modes in a favorable feedback loop resulting
in growth of pressure disturbances. These then lead tostructural and thermal loads that are detrimental to thehardware, off-design operation leading to increased emissions and decreased efficiency and ultimately increased
operating costs. To mitigate these instabilities, one design
methodology uses robust acoustic network models of thegas turbine systems that incorporates the different volumes as acoustic elements with the heat release element
comprising thermoacoustic coupling. This requires reduced order models for the heat release that can capture
unsteady dynamics under different fluctuations for all thedifferent operating modes. In this presentation, we shallcover system thermoacoustic modeling methodologies
and specifically consider models for premixed flames,
diffusion flames and spray flames that are suitable for a
reduced order framework of a design tool.
Contact: vishal@aerospace.gatech.edu

Numerical Analysis of Amplifying
Longitudinal Combustion Instability in a
Self-Excited Combustor

Seiji Tsutsumi1, Noriyasu Omata1, Taro Shimizu1,
Masahito Akamine2, Junya Aono3
1

Japan Aerospace Exploration Agency, Japan, 2University of Tokyo, Japan,
Research Center of Computational Mechanics, Inc., Japan3

A numerical study using compressible Large-Eddy
Simulation with a flamelet progress variable approach
was conducted to understand the self-excited longitudinal
combustion instability in a Continuously Variable Resonant Combustor (CVRC) with an oxidizer inlet duct of 0.14
m. A numerical experiment in which the temperature of
the inflow oxidizer was increased stepwise from 600 K in
20 K increments was conducted. The combustion noisewith small amplitude was observed at 600 K. With theincrease of the temperature, the self-exited combustion
instability of the first longitudinal mode appeared, and thiswas remarkably amplified when the temperature changed
from 700 K to 720 K. Using the phase-averaging method,
vortex-driven combustion instability was observed in thecase of 720 K. The period of the first longitudinal modein the combustion chamber was almost equal to the sumof the period of the traveling wave in the oxidizer inlet
duct and the time for the convection of vortex in theshear layer to the location of maximum heat release. In
the case of 700 K, the timing of these phenomena wasout of phase. The timing of these phenomena is essential
for reduced-order models of combustion instability, and19th International Conference on Numerical Combustion

MS03 Combustion Noise and Thermoacoustic Instabilities

a series of the authors’ studies will be presented at thisconference.
Contact: tsutsumi.seiji@jaxa.jp

Application of Matveev–Culick Model to
Combustion Instability in a Self-Excited
Combustor

and the effects of realistic boundary conditions. Self-excited azimuthal modes in annular combustors can exhibitmode switching between spinning and standing states,
and the orientation of the standing modes can change asa function of time. A multiple-input single-output azimuthal flame describing function is implemented into a quaternion valued low-order model to explore how different
flame responses, caused by modes spinning in different
directions, can affect the dominant mode of excitation.

Masahito Akamine1, Seiji Tsutsumi2, Taro Shimizu2,
Noriyasu Omata2, Junya Aono3
1

University of Tokyo, Japan, Japan Aerospace Exploration Agency, Japan,
Research Center of Computational Mechanics, Inc., Japan3

The reduced-order deterministic model for combustion
instability involving vortex shedding proposed by Matveev
and Culick (Combust. Sci. Tech. 175(6) 2003) and extended
by Seshadri, Nair, and Sujith (Combust. Theor. Model. 20(3)2016) is adapted to a single-element modeled rocket combustor called Continuously-Variable Resonance Combustor (CVRC) to understand the mechanisms of the self-excited longitudinal combustion instability and its transition
dynamics. The original model is modified to represent (1)the sound propagation and reflection in the oxidizer inlet
duct and (2) the interaction between the non-premixed
flame and vortices, both of which have been identified as
key elements of the feedback loop by a numerical simulation presented in the other part of authors’ series of studies. The validity of the model is examined by comparing
the results with the corresponding numerical simulations.
Contact: akamine@thermo.t.u-tokyo.ac.jp

Azimuthal instabilities in annular
combustors

Nicholas Alexander Worth1, Håkon Nygård2, Abhijat
Verma2

1

Contact: nicholas.a.worth@ntnu.no2

Norwegian University of Science and Technology, Norway, 2NTNU, Norway

Gas turbine engines are an integral part of the global
energy production infrastructure. The ability to rapidly
scale their power output makes them an attractive partner
to intermittent renewable energy sources, meaning they
are likely to retain their importance throughout the energy
transition. However, designing future gas turbine systems
that can operate in a fuel-flexible manner, accepting awide variety of alternative carbon-free fuels is not straightforward, and hindered by our incomplete understanding ofthese fuels and some important phenomena which occur
during their use, including combustion instabilities. In thistalk recent experimental work on thermoacoustic instabilities in annular combustors will be presented, with anemphasis on the careful excitation of modes of interest,LES Study of Combustion Instability in a
Laboratory-Scale Rocket Combustor
Shingo Matsuyama

Japan Aerospace Exploration Agency, Japan

In the present study, large-eddy simulation (LES) is
performed to simulate combustion instability in a laboratory-scale rocket combustor equipped with a single
gaseous hydrogen/gaseous oxygen coaxial injector. LESs
are conducted for corresponding combustion-instability
experiments, and the self-excited combustion instability
is successfully reproduced. The first tangential (1T) modein the combustion chamber is captured by the LES, andits amplitude and frequency are consistent with the experimental observations. The coupling behavior between
the flame motion and acoustic instability is investigated indetail from the LES results. The Rayleigh index calculated
from LES flowfield data reveals that a driving factor for
the instability is the unsteady pulsating-flame motion. The
analysis of time series data indicates that the unsteadypulsating-flame behavior is caused by the coupling between the fuel injection and the 1T mode. The present
study demonstrates the capability of LES to accurately
capture the unsteady heat release and its coupling withpressure oscillations. LES is a powerful tool which canclarify details of flame structures that are not completely
understood from the experimental measurements.
Contact: matsuyama.shingo@jaxa.jp

Numerical investigation ofthermoacoustic oscillation of a hydrogenmicromix flame with LES

Daniel Kroniger1, Hiromu Kamiya1, Atsushi Horikawa1,
Ryuta Suzuki2, Erik Munktell3, Rene Braun4

Kawasaki Heavy Industries, Ltd., Japan, 2Siemens K.K., Japan, 3Siemens
Industry Software AB, Sweden, 4Siemens Digital Industries Software,
Germany

1

Numerical simulation of thermoacoustic instabilities in

19

MS03 Combustion Noise and Thermoacoustic Instabilities

a combustor is a promising method for modeling combustion induced thermoacoustic oscillations. The objective of
this article is the analysis of instabilities of the hydrogenmicromix flames. The micromix combustion principle has
been developed for high hydrogen content fuels. This
concept is based on miniaturizing non-premixed type
flames to suppress NOx emissions. The risk of flashback
is avoided by rapid mixing via jet-in-crossflow.
In this study, numerical simulations have been conducted with Simcenter STAR-CCM+ from Siemens Digital
Industries Software. LES is used for turbulent modelling
and resolving periodical phenomena. Two complete micromix flames with opposed injection direction are included in the computational domain. The boundary conditions
are defined on the base of acoustic mode analysis results.
The LES results are validated against experimental resultsfrom a test rig with generic micromix flame configuration.
The solution of flow pattern is analyzed with POD for periodically recurring flow phenomena.
A strong periodical interaction of the flames at a thermal load of 170% (referred to the rated power of the gas
turbine) could be found in the numerical results. The oscillation mode of the high-frequency regime is identified
in the unsteady flow structure and confirmed via POD.
Contact: kroniger_daniel@global.kawasaki.com

20

19th International Conference on Numerical Combustion

MS04 Linearized Modelling of Flame Dynamics
Organizer : Thomas Ludwig Kaiser
Technical University Berlin

MS04 Linearized Modelling of
Flame Dynamics
Chair: Thomas Ludwig Kaiser
Friday, May 10; 09:50 - 11:50; Room J

On the importance of turbulencemodelling in a linear mean field analysisof turbulent flame configurations

Thomas Ludwig Kaiser1, Thorsten Zirwes2, Feichi Zhang3,
Kilian Oberleithner11Technical University Berlin, Germany, 2Universität Stuttgart, Germany,
Karlsruhe Institute of Technology, Germany

3Adjoint Linear Mean Field Analysis (LMFA) of turbulent
reacting flows facilitates a holistic inverse design procedure with a focus on thermoacoustics and flame noisefor real-world combustion systems. In laminar/stationary
flames, the temporal mean state fulfills the non-linear
governing equations of the flow, including the reaction
model. Hence a linearization is possible, as demonstrated by various authors in recent years. LMFA of turbulent
flames, however, poses a significantly more complicatedchallenge. Here, the temporal mean state does not fulfil
the governing equations of the flow, introducing mean
flow inconsistency issues during the linearization of thegoverning equations. We demonstrate that this problem
can be circumvented by linearizing a Reynolds-Averaged
Navier-Stokes (RANS) reaction model around the temporal mean state obtained by Large Eddy Simulations (LES).
In the LES, the turbulent flame is acoustically actuatedfrom the upstream direction by harmonic excitation.
The analysis reveals that the linearized reaction model accurately reproduces the flame dynamics coherent
with the harmonic actuation of an acoustically actuatedturbulent Bunsen flame with high accuracy. However, it
is also shown that state-of-the-art turbulence closure in
the LMFA appears to inadequately describe the interaction of the background turbulence and the coherent flow
fluctuation. Therefore, we investigate the interaction of
turbulence and the coherent fluctuation using a priori
and a posteriori analysis of different turbulence models.
Furthermore, we discuss the necessity of introducing a
new phase-averaging technique due to density variations,

analogous to the Favre average in the RANS framework.
Contact: t.kaiser@tu-berlin.de

Tri-Global stability analysis of reacting,swirling flows

Parth Patki, Benjamin Emerson, Vishal Acharya, Timothy
LieuwenGeorgia Institute of Technology, United States

Swirling jets are used as canonical flow fields in combustion systems with the well-established advantage ofa swirl-stabilized flame. The unsteady vortical hydrodynamic structures in these flows play integral roles in theoperability and emissions of these combustors. However,modeling these structures and their impact on the flame
remains challenging today. Hydrodynamic stability analysis has been a prominent and efficient technique forlow order modeling of coherent structures for the pastfew decades. The objective of this study is to develop a
reduced order model by the means of a Tri-Global hydrodynamic stability framework to gauge vortical flowmodes of a swirling and reacting mean flow computed byLarge Eddy Simulation based upon a commercial nozzle.
Tri-Global linear stability analysis, which is often considered to be a computationally expensive technique inliterature, is employed by exploiting the sparsity patternsof a linearized Navier Stokes equations through a highaccuracy, centered finite difference scheme. Upon discretizing the linearized governing equations about a 7-pointstencil, a generalized-eigenvalue problem is formulated
leading to a sparse stiffness coefficient matrix. The GEVP
is solved using a shift-and-invert technique to detect thenatural, linear vortical modes of the base-flow in the global framework. A helical mode decomposition in carried out
to extract the helical m modes commonly associated withswirling jets. Future work includes the addition of boundary forcing to simulate external noise and studying theharmonically forced global modes for the same base-flow.
Contact: vishal@aerospace.gatech.edu

21

MS04 Linearized Modelling of Flame Dynamics

Identifying flame response mechanisms ina swirl-stabilised combustor using multilayer networks
Vivek Thazhathattil, Anindya Datta, Saarthak Gupta,
Santosh Hemchandra
Indian Institute of Science, India

Thermoacoustic (TA) oscillation dynamics are investigated in the technically premixed PRECCINSTA swirl-stabilized combustor, for different methane-hydrogen fuelblends under atmospheric conditions using reacting flow
large eddy simulation (LES). Prior work from our group
analyzing the experimental data shows the presence ofintermittent TA and precessing vortex core (PVC) oscillations for the pure methane case and coherent TA oscillations without a PVC with H2 enrichment. Multi-layer
network analysis uses time series data from the LES solutions. We construct multi-layer networks connecting pressure at discrete points in the flow field with subnetworks
for heat-release, mixture fraction and velocity fluctuations.
Both inter-layer and intra-layer links are established basedon information theoretic measures of causality (mutual
information, transfer entropy), determined from the data
within synchronized time windows. Time-varying weighted
degree of connections between the heat release layer
and other layers are expected to clarify the relative importance of velocity and mixture fraction fluctuations on TA
and verify hypotheses made in prior studies. Additionally,
we will use centrality metrics on velocity and mixture
fraction layers to reveal the spatial positions of criticalregions. Where meaningful, we will compare results fromnetwork analysis with those from physics-based stability
and resolvent analysis to demonstrate the equivalence ofboth methods.
Contact: anindyadatta@iisc.ac.in

Neural-network based Jacobians of nonlinear closure terms for global linear
analysis
Philipp Brokof, Axel Zimmermann, Wolfgang Polifke,
Grégoire Varillon
Technical University of Munich, Germany

Global linear analysis of turbulent reactive flows promises sensitivity analysis and adjoint shape optimizationof combustion systems, but relies on Reynolds triple decomposition that requires closure terms to model turbulence. While common two-equation closures for turbulent
stresses and heat release rate in the Reynolds averaged
Navier Stokes (RANS) equations can be linearised directly,
their accuracy is often insufficient compared to large eddy22

simulations (LES) that are state of the art for reactive
flows. As a remedy, the assimilation of case-specific RANS
closures that reproduce LES mean fields with physics
informed neural network has been proposed. However,upon finding such a closure, the question arises how toincorporate it in a global linear analysis. Here, we suggest
a purely data driven approach, encoding the local non-linear mapping from the flow’s state vector to the closure ina second neural network (NN), and subsequently exploiting the NN’s direct differentiability to obtain the Jacobianof the closure needed for linear analysis. We explore thefeasibility of the idea on increasingly complex cases, forwhich the non-linear closure is known, by comparing linear transfer functions obtained from NN-based Jacobians
with those obtained from the non-linear equations undersmall forcing.
Contact: philipp.brokof@tum.de

Subcritical bifurcation of a premixed
annular V-flame

Chuhan Wang1, Lutz Lesshafft2, Christopher Douglas3,
Chun-Xiao Xu1

1
Tsinghua University, China, 2CNRS, Ecole Polytechnique, Institut
Polytechnique de Paris, United States, 3Massachusetts Institute ofTechnology, United States

This work aims to characterize the self-excited axisymmetric oscillations of a premixed laminar V-flame, in anannular jet of lean premixed methane and air. The flameis anchored near the rim of the centerbody, forming an
inverted cone, whereas the strongest vorticity is concentrated along the outer shear layer of the annular jet. Consequently, the reaction and vorticity dynamics are largely
separated, except near the flame tip, where both coalesce.
The global eigenmodes corresponding to the linearized
reacting flow equations around the steady base state arecomputed in an axisymmetric setting. We identify an arc
branch of eigenmodes exhibiting strong oscillations at
the flame extinction. Unlike the other categories of eigenmodes present in the eigenspectrum, the eigenvalues
associated with the arc branch are unaffected by the domain size and become destabilized as the Reynolds number increases. The frequency of the leading eigenmode isfound to be nearly identical to the Lagrangian advection
time from the nozzle outlet to the flame surface along theinner shear layer. This linear result suggests a non-local
intrinsic feedback mechanism involving interactions between perturbations at the nozzle edge and the flame tip.
Nonlinear time-domain analysis also reveals this instability to be subcritical. Hence, even when the flame is linearlystable, perturbations of sufficient amplitude can trigger
limit-cycle oscillations sustained by nonlinear feedback.

19th International Conference on Numerical Combustion

MS04 Linearized Modelling of Flame Dynamics

Notably, linear analysis of the time-averaged limit-cycle
state yields eigenmodes that do not match the nonlinear
oscillation frequencies, due to the system’s strong nonlinearity.
Contact: chuhan_wang@mail.tsinghua.edu.cn

23

MS05 Liquid Ammonia Spray and Combustion:
Numerical Modelling
Organizers: Jiangkuan Xing1, Christine Rousselle2
1

Kyoto University, 2Université d’OrléansMS05-1 Liquid Ammonia Sprayand Combustion: Numerical
Modelling (1)Chair: Jiangkuan Xing
Co-Chair: Christine Rousselle
Friday, May 10; 13:00 - 15:00; Room B

High-fidelity modelling of liquid ammonia
spray and combustion
Jiangkuan Xing, Zhenhua An, Ryoichi Kurose
Kyoto University, Japan

Directly using liquid ammonia can simplify the fuel supply system and reduce the start-up time. Liquid ammonia
will undergo flash boiling with strong heat loss due to its
low boiling point and is usually co-fired with small-molecular fuels for better stabilization. How to accurately model
the unique phase change and the subsequent combustion processes is still an open question. To this end, thisstudy aims to establish high-fidelity and efficient modelingstrategies for liquid ammonia spray and combustion. Specifically, a combined phase change model is developed
for describing the ammonia flash spray, and its accuracy
and superiority are assessed under various conditions bycomparing the predictions with the experimental data andother models’ predictions. Subsequently, liquid ammonia
combustion in a temporally evolving mixing layer is studied using direct numerical simulation (DNS) with detailed
chemistry to provide a deep insight into the multiple fuelstreams and strong heat loss. Extended flamelet-basedmodels are developed considering the complicated fuelstreams and strong heat loss. Their performances areevaluated with the DNS data as benchmarks. The premixed mode dominates in the liquid ammonia combustion, and the premixed flamelets are recommended to be
used for the liquid ammonia flame.
Contact: xing.jiangkuan.6h@kyoto-u.ac.jp

Computational singular perturbation
analysis applied to evaporation ofammonia droplets

Lorenzo Angelilli1, Riccardo Malpica Galassi2, Pietro Paolo
Ciottoli2, Francisco E Hernandez-Perez3, Mauro Valorani2,Hong G Im3, Venkat Raman1
University of Michigan, United States, 2Sapienza, Italy, 3KAUST, Saudi
Arabia1

Computational singular perturbation (CSP) has beeneffective in analyzing complex chemically reacting flows
by systematically retrieving intrinsic timescales and slow
invariant manifolds. This study marks the inaugural application of the analytical and computational framework to
scrutinize Lagrangian droplets experiencing evaporationand dispersion in the adjacent gases. The mathematicalformulation is derived to integrate CSP tools into thedroplet dynamics equations, with the tangential stretchingrate (TSR) to characterize the explosive/dissipative natureof the system. Ammonia droplet case studies are subsequently conducted. The CSP indices indices are explored
to offer a comprehensive analysis of different subprocesses and their interplay in modifying droplet dynamics
and justify the roles of mass-driven and thermally-driven
regime evaporation regimes at different environmental
temperature.
Contact: langelil@umich.edu

Observation of liquid ammonia spraystructure injected from a pressure-swirl
nozzle up to elevated pressure

Akihiro Hayakawa1, Hirofumi Yamashita1, Kohei Oku1,
Keito Honda1, Sophie Colson2, Gauthier Reibel1, Chen
Yi-rong1, K.D. Kunkuma A. Somarathne1, Ekenechukwu C.
Okafor3, Taku Tsujimura4, Shintaro Ito2, Masahiro Uchida2,
Taku Kudo1, Hideaki Kobayashi1
Tohoku University, Japan, 2IHI Corporation, Japan, 3Kyushu University,
Japan, 4National Institute of Advanced Industrial Science and Technology,
Japan

1

To clarify liquid ammonia spray characteristics are important for development of ammonia-fueled gas turbine.

2419th International Conference on Numerical Combustion

MS05 Liquid Ammonia Spray and Combustion: Numerical Modelling

In addition, detail understandings of liquid ammonia spray
are important for the modeling of numerical simulation. In
this study, the structure of liquid ammonia spray injectedfrom a pressure-swirl nozzle up to elevated pressure wereexperimentally investigated. Experiments were performed
for non-reacting flows using a high-pressure chamber, andthe environment pressure increased up to 0.7 MPa. The
liquid ammonia spray structure was observed using highspeed backlight imaging. The structure of liquid ammonia
spray was compared with that of ethanol spray structure
to clarify the effects on flush boiling on spray formation
characteristics. Also, the liquid ammonia spray was characterized using the degree of superheat. The high-speed
backlight images showed that the the spray angle of liquidammonia spray increased with an increase in the environmental pressure. For the liquid ammonia temperature of
294 K, the spray density seems to be changed non-monotonically with an increase in the pressure. In this study, toclarify the liquid ammonia spray characteristics in detail,laser diagnostics were employed.
Contact: hayakawa@flame.ifs.tohoku.ac.jp

Numerical study of the flame structure
and interaction between droplet/flame of
LNH3 spray flame in a swirl combustor

Jiawen Liu1, Meng Zhang1, Zhenhua An2, Jinhua Wang1,
Zuohua Huang1
1

Xi'an Jiaotong University, China, 2Kyoto University, Japan

Direct combustion of liquid ammonia has the potential
to reduce system costs and heat loss of gas turbine (GT).
However, its tendency to flash and the high latent heat ofvaporization can lead to combustion deterioration. Previous research suggests that stabilizing a liquid ammonia
flame requires swirl and preheated air. So far, the specificflame structure and interaction between the spray andflame of a liquid ammonia swirl flame remain inadequately explored. To fill this research gap, the liquid ammonia
spray model was first validated based on particle drop
image analysis and thermocouple temperature measurements. Subsequently, utilizing the OpenFOAM-8 platform,
a detailed investigation of the flame and spray behaviors
in a swirl burner using pure liquid ammonia as fuel was
carried out through a large eddy simulation. The findings
revealed that the droplet evaporation time scale is notably
shorter than the convection time scale, resulting in nearly no single droplet combustion regime occurring in thepresent configuration. The rapid evaporation of droplets
generates a preheating zone with a distinct temperature
and NH3 concentration gradient between the flame andthe spray area for preheating the fresh mixture. The flame
exhibits the characteristics of a pre-evaporated gaseous

flame, which shows a complex, mainly non-premixed
structure, yielding various combustion modes. Furthermore, the flame base exhibits noticeable heat loss, whichleads to frequently observed local extinction phenomena.
This is primarily caused by the increase of the evaporation
source term, while the increase of scalar dissipation rate
shows minimal effects.
Contact: ljw-1107@stu.xjtu.edu.cn

Direct numerical simulations ofcombustion characteristics with liquidammonia direct injection under enginelike conditions
Ziwei Huang, Haiou Wang, Kun Luo, Jianren Fan
Zhejiang University, China

Ammonia is an ideal zero-carbon fuel and it can beused directly in a liquid state. However, the utilization ofliquid ammonia in engines is constrained by its unique
physical and chemical properties. Direct injection of liquidammonia is a promising solution for internal combustion
engines, but its combustion characteristics are not wellunderstood yet. In the present work, liquid ammonia direct
injection under compression ignition engine-like conditions is investigated using direct numerical simulation(DNS) and the combustion characteristics of ammonia
spray are analyzed. The ammonia spray is injected from acircular nozzle, where the ammonia spray is auto-ignited
under engine-relevant thermochemical conditions, resulting in complex turbulent ammonia spray combustion. A
low Mach number DNS code is employed for solving theconservation equations for reacting flows with detailed
chemistry, in which block-structured adaptive mesh refinement is implemented to reduce the computational cost.
Using the DNS data, the ignition and combustion processes of the ammonia spray are analyzed. The emission characteristics of the ammonia spray flame are examined. Theinteractions between the turbulence and ammonia spray
jet flame are also reported.
Contact: wanghaiou@zju.edu.cn

Liquid ammonia spray : flash-boilingphenomenon
Christine Rousselle, Camille Hespel
UNiversité d'Orléans, France

Ammonia is a very interesting alternative for thermal
applications as gas turbines and internal combustion
engines. The injection of liquid ammonia into the combustion chamber has the double advantage of doing away25

MS05 Liquid Ammonia Spray and Combustion: Numerical Modellingwith a vaporization system and stratifying the local air/fuel mixture during combustion. Ammonia has a very highsaturation vapor pressure compared to other e-fuels suchas methanol. Therefore, during the expansion within theinjector, bubbles can be created and generate atomizationand vaporization described as flash boiling phenomena,
accompanied by a strong cooling of the medium due toits high latent heat of vaporization. The objective will beto provide a review of the recent experimental data which
provide further analysis of the process, to highlight thescientific questions and last to question about the challenges to model it for accurate simulations.
Contact: christine.rousselle@univ-orleans.fr

MS05-2 Liquid Ammonia Sprayand Combustion: Numerical
Modelling (2)Chair: Jiangkuan Xing
Co-Chair: Christine Rousselle
Friday, May 10; 15:20 - 17:00; Room B

Models for liquid ammonia sprays:
developments on Eulerian and Lagrangian
approaches
Michele Battistoni

University of Perugia, Italy

Predictive models for liquid ammonia sprays are ofutmost importance for the development and optimizationof direct injection engines and gas turbine burners. This
work presents developments for both Lagrangian discrete parcel method, and Eulerian multiphase approach.
Ammonia poses new challenges because of its high latent
heat of vaporization and the low vapor pressure whicheasily induces flash boiling, externally or also internally inthe nozzle.
Within the Lagrangian method, a correlation for the
primary breakup is proposed to determine droplet sizes
and near-exit jet cone angle, to reproduce seamlessly
flash-boiling and non-flashing regimes. Also, a model basedon nucleation and growth of bubbles within liquid droplets
is discussed, whose main feature is the prediction of a radial momentum transfer resulting from droplet explosions.
The Eulerian model, capable of resolving the internaland external nozzle flow, uses a flash-boiling mass transfer model adapted to ammonia properties and is based on
single-fluid formulation, also referred to as four equation
model. A drift-flux model version is presented which includes a velocity slip model.
Reynolds Averaged Navier Stokes (RANS) approach for
turbulence is used. Numerical results for each approach26

are compared with experimental liquid and vapor tip penetrations, spray morphology and Sauter Mean Diameter(SMD) measurements, for a multi-hole and a single hole
injector. In addition, local temperature predictions are discussed, for both liquid and gaseous phases, highlighting
and quantifying the strong cooling effect that ammonia
produces during the phase change process.
Contact: michele.battistoni@unipg.it

Numerical investigation of flash-boiling
atomization characteristics of liquidammonia fuel at various superheat
degrees

Kunkuma Amila Somarathne1, Hirofumi Yamashita1,
Kohei Oku1, Keito Honda1, Taku Kudo2, Akihiro Hayakawa1,
Hideaki AMILA Kobayashi1
1

Tohoku University, Japan, 2 Tohoku University, Japan

Recent studies on gaseous ammonia combustion haveshown that ammonia will be an important energy vector ina carbon-neutral society by 2050. World-first 50 kw gaseous ammonia gas turbine systems was built in Fukushima,
Japan. However, ammonia is commercially available asa liquid in high-pressure cylinders at room temperature.
Thus, it has been reported that considerable energy isconsumed by vaporizer and compressor when liquid ammonia is converted to gaseous ammonia. On the other
hand, high pressure is an exceedingly important factor in
improving the efficiency of gas turbine systems in termsof thermodynamics. Therefore, the ammonia gas turbine
using liquid ammonia spray combustion contributes toimproving the efficiency of the entire gas turbine system
including peripheral equipment.
Recent numerical and experimental studies on liquidammonia spray characteristics and combustion showedthat releasing high-pressure liquid ammonia through a
nozzle below the saturation pressure causes the liquid tobe superheated, resulting in-tense flash boiling. On theother hand, flash-boiling spray characteristics such asplume angle, droplet size, penetration distance are highly
dependent on superheat degree and nozzle geometries
and surface roughness. Thus, in this study single hole nozzle injector was used to visualize the spray patterns using
backlight images and the degree of super heat is varied
by altering combustor ambient pressure and liquid ammonia injection temperature. The bubble nucleation density,
bubble departure frequency, and vapor volume fractions
were calculated numerically using a nucleation theory.
The droplet diameter reduction factor of liquid ammonia
at various superheat degrees was numerically obtained
and compared with alcohol and alkane liquid fuels.
Contact: kunkuma_s@tohoku.ac.jp

19th International Conference on Numerical Combustion

MS05 Liquid Ammonia Spray and Combustion: Numerical Modelling

Internal and Near-Nozzle Flow ofAmmonia Using the ECN Spray G Injector
Daniel Goette1, Sampath Rachakonda2, David Schmidt3

1
University of Stuttgart, Germany, 2University of Massachusetts, UnitedStates, 3University of Massachusetts Amherst, United States

The global transportation sector is undergoing a shift
from fossil-based fuels to carbon-free alternatives dueto the adverse effects of burning fossil fuels on climate,health, and limited resources. Ammonia is a promisingcarbon-free fuel due to its relatively simple synthesis fromgreen hydrogen and its superior storage capabilities whencompared to pure hydrogen. However, challenges persist,with limited understanding of ammonia combustion andspray behavior during high-pressure injection. This research focuses on the near-nozzle spray behavior during
direct injection of ammonia. Computational fluid dynamics
simulations of flash-boiling ammonia injection through theEngine Combustion Network's Spray G 8-hole fuel injector were performed. An in-house solver that accounts forthermal non-equilibrium using the Homogeneous Relaxation Model (HRM) was used. The simulations were carriedout at varying injection temperatures and ambient pressures and compared with each other. Shock structures inthe spray due to supersonic flow velocities were found to
be present at injections with a degree of superheat as low
as Rp = 8.5, causing the spray to collapse, increasing spray
penetration and threatening wall wetting. The high rate ofvaporization combined with ammonia’s high enthalpy ofvaporization results in a severe temperature drop in the
combustion chamber, possibly impacting steady and efficient combustion.
Contact: st156990@stud.uni-stuttgart.de

Numerical investigation of liquidammonia combustion in MILD conditions
Zhenhua An, Jiangkuan Xing, Ryoichi Kurose
Kyoto University, Japan

Abstract: Liquid ammonia has received increasing attention as a carbon-free fuel in power equipment due toits advantage in simplifying the system and shortening
the start-up time. However, low combustion intensity andhigh NOx emissions pose challenges for liquid ammonia
combustion applications. Moderate or Intense Low oxygen Dilution (MILD) combustion technology is a promising
approach to enhance the combustion stability while keeping the NOx emissions at an acceptable level. The present
study aims to numerically investigate the ammonia spray
flames under MILD conditions. Specifically, series of temporally evolving ammonia spray jet flames, stabilized ina hot co-flow, are investigated using detailed chemistry.



Different co-flow conditions (oxygen concentration andtemperature) are considered, including the MILD combustion, high temperature combustion (HTC), and traditional
combustion (TC) conditions. The detailed chemistry anddiffusion are considered in the numerical method. The
combustion stability and emission performance under
MILD conditions are explored and compared with thoseunder the HTC and TC conditions to highlight the differences.
Contact: an.zhenhua.27u@st.kyoto-u.ac.jp

Numerical investigation of hydrogenfired prechamber ignition of the ammonia
main charge in reciprocating engines
Thomas Indlekofer, Nils Erland L. Haugen, Andrea
GruberSINTEF Energy Research, Norway

Ammonia-fired reciprocating engines have emerged asa promising technology in the maritime and power-generation sector at medium scale (1-10 MW). The use of ammonia cracking to produce small quantities of hydrogenthat can be used as a combustion promoter instead offossil fuels, enables this technology to provide a purely
carbon-free propulsion and power-generation technology.
In this context, a hydrogen-fired prechamber turbulent
jet ignition approach has been proposed and it is envisioned to offer significant advantages by accelerating theammonia ignition and combustion process, increasing its
reliability and completeness and achieving low NOx, N2O
and NH3 emissions if combined with a non-premixed ammonia flame configuration. This study exploits an OpenFOAM-based Large Eddy Simulation (LES) model to investigate the combustion behaviour of an ammonia main
charge ignited by a hydrogen-fired prechamber. Firstly,
a conventional port-injection configuration for the ammonia main charge is considered and the hydrogen-fired
prechamber is found to provide a strong ignition source
for ammonia-air mixtures. The effect of the main-charge
equivalence ratio and of the wall temperature on combustion efficiency and emissions formation is evaluated. Secondly, the same hydrogen-fired prechamber configurationis shown to be able to successfully ignite a liquid ammonia main charge directly injected as a spray and modelledusing Lagrangian Point Particles (LPP).
Contact: nils.e.haugen@sintef.no27

MS06 Detonations in Liquid-Fuel Sprays:
Recent Progress and Open Questions
Organizers: Alexei Poludnenko1, Hai Wang2
University of Connecticut, 2Stanford University

1

MS06-1 Detonations in LiquidFuel Sprays: Recent Progress andOpen Questions (1)A molecular view of shocks and shockdroplet interactions

Chair: Alexei Poludnenko
Co-Chair: Hai Wang
Wednesday, May 8; 10:40 - 12:20; Room I

Stanford University, United States

Numerical Modeling of Gaseous and Spray
Detonations in Hydrocarbon Fuels using
Complex Chemistry
Alexei Poludnenko, Sai Sandeep Dammati, Abeetath
Ghosh
University of Connecticut, United States

Recent years have seen a resurgence of interest in
detonation-based propulsion systems. Design and development of such systems requires accurate and predictive
numerical modeling of detonations both in gaseous andliquid hydrocarbon fuels. This in turn relies heavily on the
fidelity of the underlying physical and chemical models,
including the description of chemical kinetics, as well as
spray droplet drag, evaporation, and secondary atomization. Most of these constituent models have been developed for low-speed combustion and multi-phase flow regimes, and their accuracy and applicability in the extreme
flow conditions characterstic of detonations is not clear. In
this work, we use two- and three-dimensional Eulerian-Lagrangian simulations of spray detonations propagating inliquid n-dodecane to perform the detailed characterizationof the hydro- and thermodynamic regimes experienced
by the spray in a detonation front. These calculations use
complex chemistry, multi-species transport, and state-ofthe-art spray sub models. Furthermore, we compare theobserved dynamics and properties of spray detonations
with their purely gas-phase counterparts both in the
pre-vaporized n-dodecane, as well as in other gaseous hydrocarbon fuels. Finally, we discuss the applicability of theexisting spray sub-models and their required extensions
for the accurate modeling of spray detonations.
Contact: alexei.poludnenko@uconn.edu

28

Hai Wang, Amitesh Sivaraman Jayaraman, Ethan Samuelgenter, Nikolaos Kateris
Gas-phase and two-phase detonations are characterized by small spatial regions of thermodynamic nonequilibrium, which may impact mass, momentum, energy
transport, and chemical reactions in a manner that is
not suitably described by the Navier-Stokes equations
and conventional chemical kinetics. To examine theseeffects, we carried out a series of molecular dynamics(MD) studies targeting a better understanding of several phenomena with direct relevance to gas-phase andspray detonations. These problems include translational
nonequilibrium in shock fronts, vorticity generation near
triple points, shock-induced transport of long-chain molecules behind the shock, shock-droplet interactions, andthe resulting droplet fragmentation upon shock impact.
The focus of the analysis is on the effect of non-equilibrium on the transport of mass, momentum, and energy
behind a shock front. The implications of the findings on
detonation physics, chemistry, and simulations will be discussed in detail.
Contact: haiwang@stanford.edu

Detonation propagation in droplet-laden
flows
Venkat Raman, Ral Bielawski
University of Michigan, United States

Multiphase detonations pose a number of modelingand computational challenges. This includes, but not limited to, the description of shock-induced breakup of droplets, propagation of shock-reaction fronts through dense
spray medium, evaporation and inhomogeneous mixing offuel with oxidizer, and the initiation of reactions in thesehighly complex and time-varying fields. In this talk, preliminary findings on the shock-droplet interactions, andextensions to reaction coupling in dense spray regime will

19th International Conference on Numerical Combustion

MS06 Detonations in Liquid-Fuel Sprays: Recent Progress and Open Questions

be discussed. Where applicable, comparisons with experiments will be shown. A summary of the critical modelingand data needs will be provided.
Contact: ramanvr@umich.edu

Numerical Study on the Effect of Droplet
Spatial Distribution on Liquid-Fueled
Detonation
Manoj Paudel, Jacob McFarland
Texas A & M University, United States

This study investigates the impact of initial droplet
spatial distribution, in particular the presence of droplet clusters, on the multiphase detonation phenomena.
2D Euler-Lagrange simulations with low vapor pressureliquid fuel (n-decane) and air(N2/O2) will be presented.
The hydrodynamic code FLASH is used for the solutionof reactive Euler equations with multiphase source terms
where coupling is achieved through operator splitting. The
directionally split Piecewise Parabolic Method (PPM) and
Bader-Deuflhard method implemented in FLASH will be
used for the solution of Euler equations and the system of
ODEs from reaction kinetics respectively. Interchange ofvariables and source terms from particles to gas (and viceversa) is achieved with bi-linear mapping of variables between the Lagrangian points and Eulerian mesh. A threestep reduced mechanism tuned to reproduce ZND parameters of the detailed mechanism for variable equivalence
ratios is used for reactions in the gas phase. For the particle phase, deformation, evaporation and breakup will beconsidered through the modified Taylor Analogy Breakup(TAB) model, Abramzon-Sirignano evaporation model, and
Kelvin-Helmholtz Rayleigh-Taylor (KHRT) breakup model
respectively. Simulations for both globally lean and richmixtures with varying degree of initial clustering of micron
sized droplets will be presented to study the detonation
speed and structure under heterogeneous multiphaseconditions.
Contact: manojpdl@tamu.edu

Wedge-stabilized oblique detonation in
n-dodecane droplet and air mixtures
Huangwei Zhang

national university of Singapore, Singapore

This study numerically investigates wedge-induced
oblique detonation waves (ODW) in n-dodecane droplet/
air mixtures under real flight conditions. The results revealthat the discrete droplets introduce considerable non-uniformity and unsteadiness in the ODW. Specifically, the

5-μm droplets can complete evaporation slightly after theoblique shock wave, resulting in an increased initiation
length compared to the gaseous ODW with the sameequivalence ratio. The deflagration front is irregular andpeninsula shaped. The transition mode exhibits a combined smooth and abrupt modes. The effects of droplet
size and flight altitude on the ODW morphology are alsostudied. As the droplet diameter increases, there is a corresponding increase in droplet penetration distance in the
induction zone, shifting the evaporation front downstream.
The angle of the oblique shock wave slightly increases,
and the reaction front changes non-monotonically as thedroplet size varies. Moreover, with increasing flight altitude, the significant decrease in inflow pressure leads toreduced droplet evaporation rate and therefore increased
droplet penetration distance. The results also show thatthe transition mode is significantly affected by the droplet
size and flight altitude.
Contact: mpezhu@nus.edu.sg

MS06-2 Detonations in LiquidFuel Sprays: Recent Progress andOpen Questions (2)Chair: Alexei Poludnenko
Co-Chair: Hai Wang
Wednesday, May 8; 13:30 - 15:10; Room I

Molecular hotspots and shock enhanced
transport in detonation waves
Matei Radulescu, Ramki Murugesan
University of Ottawa, Canada

Detonation waves in gases and multi-phase systems
are very complex, involving a highly transient cellular
structure and a turbulent reaction zone coupled withtransverse shocks. The role of out-of-equilibrium phenomena in these waves remains unclear despite extensive
research on the underlying physics. Using hard spheremolecular dynamics simulations for a single activatedexothermic reaction, we demonstrate and quantify two
fundamental mechanisms where species resulting froma reactive collision provide modification of the surrounding reactivity and wave sustenance. First, we demonstrate the role of molecular hotspots, first predicted by
Prigogine. Species evolving from a reactive collision
have a substantial excess of translational energy. This
excess energy serves in promoting neighboring reactive
collisions. The absence of molecular chaos accelerates
the reactivity by a factor of two (Murugesan et al. Comb.
Flame 2019). The role of out-equilibrium reactions is29

MS06 Detonations in Liquid-Fuel Sprays: Recent Progress and Open Questions

further demonstrated in the presence of shock waves bya mechanism first postulated by Zel’dovich (Murugesan
PhD 2023). We study the problem of shock to detonationtransition using molecular dynamics of a single exothermic reaction. Results suggest that shock-induced ignition and transition to detonation involve non-equilibrium
reactions that overlap with the shock structure, showing
strong translational non-equilibrium with reactive fingers.
We find that shock amplification rate and transition todetonation are approximately twice faster than predictedby conventional continuum Euler hydrodynamic models.
A Navier-Stokes model with hard sphere transport properties effectively captures the acceleration process.
Contact: matei@uottawa.ca

Pathological propagation regimes inliquid-fuel detonations
Raúl Hernández-Sánchez1, César Huete1, Daniel
Martínez-Ruiz2

Universidad Carlos III de Madrid, Spain, 2Universidad Politécnica de Madrid,
Spain

1

Detonation waves are supersonic reactive fronts involving strong pressure variations, which propagate in aself-sustained manner when a sonic surface isolates themfrom downstream conditions. In ideal gaseous detonations, it is possible to predict the Chapman-Jouguet velocity associated with the sonic condition based on equilibrium states.
Nonetheless, there exists a distinct propagation regime
called pathological detonation, wherein the sonic condition is not attained at the equilibrium state but within thereactive region. This regime may arise when endothermic
effects are considered, leading to the formation of aninternal sonic point where local thermicity vanishes. The
self-sustained propagation regime is then obtained placing the sonic point in the neutrally thermal zone, which
requires studying the detonation structure. Indeed, endothermic effects acting behind the sonic point are decoupled from the detonation propagation mechanism, leading
to higher propagation speeds. This regime is commonly
analyzed for endothermic and exothermic competing
reactions of multistep chemical schemes. However, thisstudy extends the understanding of pathological detonations, revealing their occurrence in liquid-fueled detonations where droplet vaporization dominates the late stageof the non-equilibrium region. The range of appearance ofsuch detonations is shown to increase with the fuel droplets Stokes number and the mixture equivalence ratio.
Contact: raulhern@ing.uc3m.es

30



The Influence of non-premixed heatcombustion on spray detonations
Ryan Houim

University of Florida, United States

Numerical simulation of stoichiometric JP10 and air
detonations were performed. The governing equations
representing a fully compressible reactive gas and an Eulerian model to represent the JP-10 droplets were solved.
The results show a cellular multiphase detonation consistent with previous literature. Two heat release zones
were found. A primary heat release occurs in a narrow
region (~5-10 mm) behind the leading shock where thedroplets are convectively heated, vaporize, and burn inthe shock-heated air. A secondary heat release occurs
over an extended region where fuel-rich pockets continue
to burn as turbulent non-premixed flames. The secondary
non-premixed heat release zone is caused by multiphaseflow effects that occur in the primary heat release zone.
Finite Stokes number effects cause the droplets to lag
behind the shock wave while the air is compressed immediately. Droplet inertia effect produces a thin band where
the local equivalence ratio decreases substantially. Eventually, the droplets accelerate in the post-shock flow andthe local equivalence ratio increases and even becomes
fuel-rich in small regions. This results in alternating fuel-rich and fuel-lean regions that persist throughout the
primary reaction zone and continue to burn in the secondary heat release zone as non-premixed flames. Thissecondary non-premixed heat release zone is unique tosprays and its influence on the detonation structure is notwell understood.
Contact: rhouim@ufl.edu

Nonthermal termolecular reaction effects
on planar and oblique detonations
Jacqueline H Chen1, Akanksha Baranwal2, Jorge Salinas1,
Swapnil Desai3, Yujie Tao4, Ragu Sivaramakrishnan5

Sandia National Laboratories, United States, 2Sandia National Laboratoies,
United States, 3ALIR Corporation, United States, 4Southeast University(China), China, 5Argonne National Laboratory, United States1

In applications involving fast transport conditions
including supersonic transport and planar and obliquedetonations, there is a high probability of occurrence of
non-thermal reactions due to the presence of non-trivial
amounts of highly reactive radicals including H, O and OH
apart from O2 as demonstrated recently (M. P. Burke etal., (2017), Tao et al., (2021)) that participate in collisionalcooling. High-fidelity simulations were performed to assess the significance of non-thermal reactivity induced byradical-molecule association and radical-radical recombi-

19th International Conference on Numerical Combustion

MS06 Detonations in Liquid-Fuel Sprays: Recent Progress and Open Questions

nation reactions on the initiation, propagation and structure of planar and oblique detonation waves for different
mixture conditions. It is found that non-thermal reactivity
induced by radical-molecular association reaction R5:
H+O2 (+M) ↔ HO2 (+M) and radical-radical recombination reaction R16: H+OH (+M) ↔ H2O (+M) can alter thewedge-stabilized oblique detonation wave (ODW) and planar detonation wave (PDW) propagation and structure.
Contact: jhchen@sandia.gov

Numerical modeling of chemical
combustion induced by blast waves
interactions

Fumiya Togashi1, Joseph D Baum1, Rainald Lohner2,
Orlando A Soto3, Mariana Cruz4

Applied Simulations Inc., United States, George Mason University, UnitedStates, 3Applied Simulations Inc, United States, 4Defense Threat Reduction
Agency, United States
1

2Combustion of spatially dispersed liquid chemical uponinteraction with a blast wave was investigated in this effort. The numerical simulation modeled a test in whicha plastic bottle filled with the liquid simulant and a small
explosive detonator were hung in a chamber, while a primary explosive charge was hung some distance away. The
primary charge detonation was delayed to allow evolutionof the spray prior to interaction with the blast environment The oxygen balance in the chamber was positive.
A CFD methodology capable of modeling the complete
set of physical processes was required to better understand the controlling physical mechanisms. Explosive
detonation was modeled using the Jones-Wilkins-Lee (JWL)
equation of state, while simulant reaction was modeledusing Chemkin-II, coupled with our in-house CFD solver.
A reduced kinetics reaction model based on the GRIMech3.0 combined with simulant decomposition kinetics
was developed. The numerical model incorporates a volume-of-fluid methodology. Turbulence was modeled usinga MILES (Monotonically integrated LES) model. The mostchallenging part was the accurate modeling of the liquidbulk break-up to ligaments and further to large droplets,
as no theoretical or even an empirical model exists forthis phenomenon. A 0-D analysis of simulant droplet heattransfer and ignition was also conducted prior to the fullscale simulation. The analysis indicated the importance ofthe numerical modeling of liquid aerosolization during thedispersion and cascading into small droplets by the blast
wave interaction.
The numerically predicted bottle break and liquid dispersion agreed well with the test visualization data, andthe predicted pressure captured the pressure changes
during evaporation and reaction. The excellent agreementof the measured and predicted pressure histories indi-

cates that the current numerical methodology accurately
models simulant combustion as well as all other controlling physical mechanisms.
Contact: fumiya.togashi@gmail.com

MS06-3 Detonations in LiquidFuel Sprays: Recent Progress andOpen Questions (3)Chair: Alexei Poludnenko
Co-Chair: Hai Wang
Wednesday, May 8; 15:30 - 17:10; Room I

Modeling of High-Pressure Transcritical
Phase Change at Liquid-Fueled
Detonation Conditions
Navneeth Srinivasan, Suo Yang

University of Minnesota, Twin Cities, United States

Liquid-fueled detonation engines are of significant
interest due to the on-board practicality of storing liquid
fuels comparing to gaseous fuels. With pressures of 2040 bar or higher, these engines involve thermodynamically transcritical and supercritical processes, such as
evaporation facilitated by transcritical shock/detonationinteraction and high-temperature mixing. Fuel-air mixtures
are multi-component, complicating matters with elevatedmixture critical points compared to individual constituents.
This necessitates thermodynamic modeling to understandliquid fuel interactions with detonation waves, thickened
interfaces, weakened surface tension, and transcriticalphase change. The vapor-liquid equilibrium (VLE) theory,a first-principled model describing multiphase thermodynamics, faces computational challenges and robustness
issues when integrated with CFD modeling. Ongoing
efforts address these challenges, including developing
reduced-order models, shared-memory in-situ adaptive
tabulation (ISAT) of VLE solutions, and an artificial neuralnetwork (ANN)-aided VLE model. These approaches havebeen applied to study transcritical shock-droplet interactions and (reacting) turbulent mixing layers, offering
insights into transcritical fluid behavior. Questions persist
regarding fuel droplet evaporation at elevated pressures.
Primary tests on droplet evaporation using the ANN-aided VLE model reveal a potential decrease in evaporation
timescales near critical points. Additionally, exploring
non-equilibrium droplet physics remains an open question,emphasizing the importance of understanding equilibrium
solutions for model development, even in non-equilibrium
scenarios.
Contact: srini237@umn.edu

31

MS06 Detonations in Liquid-Fuel Sprays: Recent Progress and Open Questions

Vibrational Nonequilibrium Effects in
Hydrogen Detonations
Stephen Voelkel1, Mark Short2, Carlos Chiquete2

Los Alamos National Laboratory, United States, 2 Los Alamos National
Laboratory, United States

1

Detonations in gaseous systems exhibit vibrational
nonequilibrium not only through the induction zone but
also throughout the reaction zone, potentially affecting
both hydrodynamic and chemical reaction characteristics.
In general, reactant species are vibrationally cold andtranslationally hot, resulting in competing effects thatsimultaneously suppress and enhance reaction rates,
respectively. This imbalance of energy modes can evenpersist into the post-reaction product state. Due to thechaotic nature of gaseous detonations, it is not clear thatthese competing effects will simply cancel out, particularlyin unstable detonation regimes. We seek to further assess
these nonequilibrium processes and their physical effects
in gaseous, hydrogen-based detonations. To this end, we
will present a vibrationally-informed equation of state andreaction rate model that accounts for energy exchange
between translational-rotational, vibrational, and chemical
modes. A multi-temperature approach will be implemented, which leverages a common translational-rotationaltemperature and a set of species-specific vibrationaltemperatures. This model will be utilized to numericallyassess how different ambient conditions, such as varied
inert species at varied concentrations, affect the induction
and reaction zones as well as detonation stability (pulsation) characteristics.
Contact: svoelkel01@gmail.com

32

19th International Conference on Numerical Combustion

MS07 Computational Tools for DetonationDriven Propulsion Physics
Organizers: Jiro Kasahara1, Venkat Raman2, Jeong-Yeol Choi3, Akiko Matsuo4, Nobuyuki Tsuboi5
Nagoya University, 2University of Michigan, 3Pusan National University, 4Keio University, 5Kyushu Institute of Technology

1

MS07-1 Computational Tools for
Detonation-Driven Propulsion
Physics (1)ing future RDE designs.

Chair: Jiro Kasahara
Co-Chair: Akiko Matsuo
Friday, May 10; 09:50 - 11:50; Room G

Lagrangian Particle Analysis of
Detonations in Stratified Reactant
Mixtures

Numerical Analysis of the Characteristic
Chemical Time-scale in a C2H4/O2 Nonpremixed Rotating Detonation Engine

Jeong-Yeol Choi, Mohammedniyasdeen Nejaamtheen
Pusan National University, Korea

This study elucidates the characteristic chemical kinetics timescales pertinent to rotating detonation engines(RDEs). The presence of supersonic-speed detonations in
an RDE gives rise to a highly intricate reacting flow field,
encompassing processes across a broad range of timescales. In particular, the characteristic times associatedwith various combustion kinetics, (deflagration, deflagration-to-detonation transition (DDT), and detonation), injection processes (backflow and recovery), flow dynamics(residence time and mixing), wave arrival time, and acoustic modes (longitudinal and transverse resonance). This
study specifically aims to explore variations in chemical
kinetics time scales, given their significant impact on detonative heat release. The investigation focuses on C2H4,
a higher hydrocarbon-based fuel, across equivalence
ratios ranging from 0.25 to 1.25, considering three plenum
pressure variations: 1, 2, and 5 atm. The chemical reaction
time is typically 15 times greater than the induction time,
and the chemical equilibrium time in RDE demonstrates
a wider range, from 0.006 to 160 ns, depending on the
inflow conditions and the fuel-mixture composition. This
bears implications for optimizing detonative heat release,particularly in pre-detonation deflagration in real RDEs.
Overall, this study serves as the groundwork for an extended investigation into characteristic time scales, aiming
to deepen our understanding of flow physics for optimiz-Contact: niyasdeen.aero@gmail.com

Michael Ullman, Ral Bielawski, Venkat Raman
University of Michigan, United States

In many practical applications of detonation-laden
flows, non-premixed reactants are supplied to the device
via discrete injection. This often creates spatial and temporal variations in reactant mixedness, wherein pockets
of partially premixed reactants are situated amongst regions of pure fuel or oxidizer. So call “stratified reactant
mixtures” have been found to impact macroscopic wave
behaviors, such as detonation cell size and wave speed,
but the mechanisms driving discrepancies from ideal
detonation propagation remain unclear. To address this,the present work considers two- and three-dimensional
simulations of detonations traversing stratified reactant
mixtures in rectangular channels. Adaptive mesh refinement and detailed chemical kinetics are used to simulate
the complex induction and reaction zones with O(100)cells per notional ZND induction length. A digital filtering
approach is used to generate reactant mixtures with threedifferent stratification length scales, and the subsequenteffects on wave speed, structure, and stability are analyzed. To examine how the detonation processes the nonuniform reactants, an in-situ Lagrangian particle tracking
algorithm is implemented in the solver. This allows thestate of notional fluid particles to be stored at runtime,such that the thermodynamic cycles experienced by fluidswith different initial reactant compositions can be analyzed. These investigations thus provide translatable insights
into the underlying physical phenomena dictating unsteady detonation propagation in applications of interest,
such as rotating detonation engines (RDEs).
Contact: mullman@umich.edu

33

MS07 Computational Tools for Detonation-Driven Propulsion Physics

Two-dimensional Numerical Simulation
on Dimethyl Ether / Oxygen Premixture
Detonation in a Narrow Channel Using
Reduced Chemical Reaction Model:
Effects of Numerical Accuracy on
Formation of Cellular Sub-Structure
Nobuyuki Tsuboi1, Daiki Kubota1, A. Koichi Hayashi2
1

Kyushu Institute of Technology, Japan, 2Aoyama Gakuin University, Japan

Two-dimensional numerical simulations on dimethyl
ether (DME)/oxygen detonations are performed using
a reduced reaction model to investigate the effects ofnumerical resolution on unstable features of the cellularsub-structure. The Zhao et al. model which includes 55
chemical species and 290 elementary reactions is used in
the present study. The two-dimensional simulations withdifferent channel widths and numerical accuracy showthat the detonation propagates at the CJ (Chapman-Jouguet) velocity and strongly irregular cellular structures
are observed for all cases. However, the simulated mean
and maximum/minimum detonation cell sizes depend on
the grid resolution and the spatial order of the numerical flux. A sub-structure, associated with the transverse
detonation, is captured by the higher-order scheme. This
sub-structure causes a generation of many triple points
because of a short induction distance between the Machstem and the combustion front. The fifth-order WCNS
(weighted compact nonlinear scheme) schemes improve
the resolution near the shock wave and combustion front
compared with the second-order MUSCL.
Contact: tsuboi@mech.kyutech.ac.jp

Massless-tracer analysis of detonationturbulence interaction in non-diluted
stoichiometric hydrogen/oxygen mixture:a DNS study
Sou Suzuki1, Kazuya Iwata1, Reo Kai2, Ryoichi Kurose1
1

Kyoto University, Japan, 2Kyushu University, Japan

Detonation engines have extensively been studied sofar, but most of the related fundamental research ignored
the effect of turbulence caused by propellant injection.
Our recent work performed direct numerical simulations(DNSs) of detonation-turbulence interaction and showedthat turbulence collapses cellular structure and promotes
reactions. As a further investigation, particle-based analysis is useful because the detonation peaky structure
could not be captured via conventional time and spatial
average. Therefore, in this study, DNS with newly incorporated massless tracer analysis is performed to evaluate
the peaky structure and the effects of turbulences on
the detonation in a non-diluted stoichiometric hydrogen/34



oxygen mixture in detail. The results show that the massless-tracer analysis can reproduce peaky structures anddemonstrate that the distributions of inflow velocity into
the shock affect subsequent structures. Also, the stronger
turbulence increases the peak pressure, promotes chemical reactions, widens the distribution of inflow velocity into
the shock, and shortens the induction length, which is theactual distance from the shock to the flame. Moreover,the high peak pressure under strong turbulence is causedby the region of higher inflow velocity into the shock.
These suggest that the use of present analysis is effective
for understanding the detailed physics of detonation in
non-ideal situations. An extension to Eulerian-Lagrangianmodeling with inertial particles for two-phase detonation
is being planned for our future works.
Contact: suzuki.sou.48s@st.kyoto-u.ac.jp

LES simulation of Tangential-mode
Combustion Instability in the Rocket
Combustor with Multiple Impinging-type
Injectors
Bu-Kyeng Sung, Jeong-Yeol Choi
Pusan National University, Korea

In the present numerical simulation, the rocket combustion with 48 impinging-type injectors is simulated byusing the RPL3D in-house code. The combustor was designed as a rotating detonation rocket engine by Nagoya
University. Also, the combustor is experimentally assessedand confirmed operatable as an RDRE. By reviewing thedesign of the combustor, it is found to have undesirable
design conditions which may trigger the combustion instability of the rocket combustor. This undesirable design
condition, such as a large mixture distribution adjacentto the wall, for the rocket engine acts as a necessary
condition for the rotating detonation engine. The gaseous Ethylene and the oxygen is used as a propellant. The
quasi-global chemistry mechanism with 9 species and 10
reaction steps is used. The ignition is achieved by applying a temperature of 1800 K in the combustor. After theignition, the combustion instability is derived without any
trigger function. The combustion instability was developed
over a millisecond of simulation. After the flow had fully
developed, the period of pressure peaks was comparedwith a C-J detonation condition. The speed of the detonation wave was found to be 2239.9 m/s and compared to
the CJ condition, the velocity deficit correspond to 24 %similar to most of the rotating detonation engines. Therefore, it is concluded that this rocket combustion instability
is a rotating detonation.
Contact: tjdqnrud91@pusan.ac.kr

19th International Conference on Numerical Combustion

MS07 Computational Tools for Detonation-Driven Propulsion Physics

Numerical Analysis on Pressure
Gain Combustion of Radial-Rotating
Detonation Engine

A. Koichi Hayashi1, Takumi Ito2, Nobuyuki Tsuboi2, Kohei
Ozawa2, Yuta Otsuka3, Kazuhiro Ishii3
1

Aoyama Gakuin University, Japan, 2Kyushu Institute of Technology, Japan,
Yokohama National University, Japan

3

Disc-type Rotating Detonation Engine (D-RDE) is usefuldevice for a practical RDE at the point of its compactness.
So far, we have been especially studying D-RDE numerically and experimentally since more than five years. The
present work will show the discussion of the results, theirsummery, important findings, and future direction, basedon Pressure Gain (PG) through our understandings fromthe passed studies. Furthermore, knowing the accuracy
and problems of numerical analyses and the comparison
between the numerical results and experimental ones, wewill discuss about D-RDE to get a better PG. One of thepoints we will talk is some solution from the point of viewsof gas-turbine engine. So far, we obtained the PG values
for numerical simulations as well as experiments, which
provide quite good agreement with the results by thepassed several researchers’ studies. One of our findings
from those passed PG results is that the PG values are
independent from the RDE configurations such as regular
RDE and Disk-RDE.
Contact: supernova.hayashi@gmail.com

MS07-2 Computational Tools for
Detonation-Driven Propulsion
Physics (2)Chair: Jeong-Yeol Choi
Co-Chair: Nobuyuki Tsuboi
Friday, May 10; 13:00 - 15:00; Room G

3D Evaluation of H2-Air Non-Premixed
Gas Injection Ports Number on Flow Field
in Disk RDE

Takumi Ito1, Nobuyuki Tsuboi1, Kouhei Ozawa1, Koichi A
Hayashi2
1

Kyushu Institute of Technology, Japan, 2Aoyama Gakuin University, Japan

Detonation is a form of combustion in which combustion waves induced by a shock wave propagate throughthe reaction mixture. Rotating Detonation Engine (RDE), in
which detonation waves rotate in an annular combustor,
is said to improve theoretical thermal efficiency by morethan 20% compared to the Brayton cycle. Therefore, it isattracting attention as a next-generation engine; in 2018,



a Disk Rotating Detonation Engine (DRDE) was proposed,
which combines a radial turbine with a high expansion
ratio per stage with an RDE. Previous studies showedcharacteristics propagation of approaching and departing
under premixed injection with hydrogen-oxygen. However,no similar propagation was observed in the case of hydrogen-air. Therefore, this study presents a three-dimensional viscosity simulation of a DRDE (disk-type rotary detonation engine) using the Navier-Stokes equations with
the UT-JAXA reaction mechanism for hydrogen-air. The
purpose of this study is to visualize the propagation pattern in the DRDE combustor, to investigate the effect of
the number of injection ports on the propagation patternunder non-premixed injection conditions, and to evaluate
the effect on stable detonation propagation and DRDE
performance. These evaluations and indices such as Pressure-Gain will be used to estimate the performance of the
DRDE when a turbine is inserted.
Contact: ito.takumi578@mail.kyutech.jp

LES Modeling and Analysis of Flow andCombustion Dynamics in a Hydrogenair Rotating Detonation Engine Coupledwith Diverging Nozzle and Turbine Stator
BladesPinaki Pal

Argonne National Laboratory, United States

A large-eddy simulation (LES) study is conducted to numerically investigate the combustion dynamics as well as
aero-thermal phenomena in a non-premixed hydrogen-air
rotating detonation engine (RDE) configuration coupledwith a diverging-shaped lower-end wall and downstream
turbine stator blades. The wall-modeled LES framework
incorporates hydrogen-air detailed chemical kinetics andadaptive mesh refinement (AMR). A comparative analysis
is carried out for two operating conditions with different
fuel/air mass flow rates but global equivalence ratio ofunity. Numerical results indicate significant deflagrative
combustion occurring in the fill region. Moreover, theleading detonation wave is found to be trailed by a characteristic azimuthal reflected-shock combustion (ARSC)
wave, which consumes unburned vitiated reactants thatleak through the main detonation wave. A novel combustion diagnostic technique based on chemical explosivemode analysis (CEMA) is employed to quantify the fractionof heat release occurring in the detonative mode versus
deflagrative mode for the simulated conditions. Lastly,
analysis of combustion behavior and phase-averaged exit
flow profiles is performed in the presence and absence ofturbine stator blades.
Contact: pal@anl.gov

35

MS07 Computational Tools for Detonation-Driven Propulsion Physics

Numerical Investigation of the Interaction
between the Exhaust Flow of Reflective
Shuttling Detonation Combustor andSupersonic Turbulent Flow

Moeno Miyashita1, Akiko Matsuo1, Eiji Shima1, Noboru
Itouyama2, Akira Kawasaki3, Ken Matsuoka2, Jiro Kasahara2
Keio University, Japan, 2Nagoya University, Japan, 3Shizuoka University,
Japan

1

In this study, three-dimensional numerical analyses for
Reflective Shuttling Detonation Combustor (RSDC) withexternal main flow were conducted to investigate the newconcept of RSDC for practical use. The computationaltargets of RSDC are the region where the hydrogen-air
premixed gas flows from three rows of injectors set atthe bottom in fuel-rich conditions. The main flow area isthe region where the air flows at Mach number 3, and the
RSDC was connected with the main flow area. The reflective wall distance, the height, and the width of RSDC were
set to 45.0 mm, 53 mm, and 5 mm. The governing equations used in this study were three-dimensional compressible Navier-Stokes equation and a chemical conservation
law of 9 species. The Hybrid LES/RANS model was also
used as the turbulence model. As a result, the mixtureof the exhaust flow of RSDC and the main flow were observed in the main flow area, and the excess hydrogen in
the exhaust flow combusted. In addition to these results,
the effect of the inflow angle of exhaust flow of RSDC was
further investigated by analyzing additional targets, which
RSDC were connected with the main flow area at different
angles.
Contact: moenomiyashit@keio.jp

Numerical Consideration to Geometry ofDiverging Rotating Detonation Engine

Takumi Sada1, Akiko Matsuo1, Eiji Shima1, Noboru
Itouyama2, Akira Kawasaki3, Ken Matsuoka2, Jiro Kasahara2
Keio University, Japan, 2Nagoya University, Japan, 3Shizuoka University,
Japan

1

In this study, the flow structure and propulsive performance of the diverging RDEs were investigated, andits geometry was considered. The combustor length andbottom diameter were fixed at 70 mm and 20 mm, respectively, and hydrogen-air premixed gas was used as
propellant. A detonation propagated stably in the straightchannel, while internal pressure and combustion efficiency decreased in the diverging RDE with angle of 5 deg(position to start diverging: 0 mm). Based on these results,
we searched for the optimum geometry to maintain rapid
combustion and improve propulsive performance. Here,analyses for combustor geometries with 10, 20, and 3036

mm of position to start diverging were conducted. Supersonic exhaust was observed in all combustors with adiverging section. In particular, in the case of 20 and 30
mm, the flow choked at the start point of the diverging,and the pressure distribution near the bottom was similar
to that of a straight channel. It is considered that highcombustion efficiency can be maintained by diverging
the flow path behind the detonation, where combustion
proceeds rapidly. In addition, the relationship between
the combustion region, geometry, and propulsive performance was summarized, and guidelines were obtained for
optimal design.
Contact: t.sada000@keio.jp

A low-dimensional modeling approachto acceleration of an internal flow of arotating detonation engine

Kotaro Nakata1, Noboru Itouyama1, Ken Matsuoka1, Jiro
Kasahara1, Akira Kawasaki2, Hiroaki Watanabe3, Akiko
Matsuo4, Ikkoh Funaki5, Kazuyuki Higashino6

Nagoya University, Japan, 2Shizuoka University, Japan, 3École nationalesupérieure de mécanique et d'aérotechnique, France, 4Keio University,
Japan, 5Institute of Space and Astronautical Science, Japan, 6Nets Co., Ltd.,Japan
1

A quasi-one-dimensional flow model for an internal
flow of a rotating detonation engine (RDE) with multiple
diverging angles (constant diverging angles from −3 to 5deg) was proposed to reveal its acceleration mechanism.
An RDE without an inner cylinder that had an inlet diameter of 20 mm was focused on, and gaseous ethylene-oxygen or hydrogen-oxygen was utilized as the propellants.
In a diverging channel, a subsonic flow near the injector
surface was accelerated via heating from a detonative
combustion, choked around the middle of the channel,
and then accelerated to supersonic speed. In the converging channel, a smaller exit area resulted in a higher
pressure, and a subsonic flow was gradually accelerated
to be sonic speed at the exit due to mechanical converging. To validate the model, experimental results frompressure measurements and optical observations wereintroduced. Axial pressure distributions in the calculationand in the experiments had the same tendency, and highspeed images captured from the side of the RDE implied acompact heat release region near the injector surface as
estimated in the calculation. These results suggested thatthe internal flow of the RDE can be reasonably estimatedby the quasi-1-D model.
Contact: nakata.kotaro.g1@s.mail.nagoya-u.ac.jp

19th International Conference on Numerical Combustion

MS08 Advances in Detailed Numerical Simulationof Reciprocating Engines
Organizers: Yasuo Moriyoshi1, Taisuke Nambu2
Chiba University, 2Japan Aerospace Exploration Agency

1

MS08 Advances in Detailed
Numerical Simulation of
Reciprocating Engines
Chair: Yasuo Moriyoshi
Co-Chair: Taisuke Nambu
Wednesday, May 8; 10:40 - 12:20; Room J

Research and Development of a
Combustion Flow Analysis Program for
Reciprocating Engines Using the Cartesian
Grid and an Immersed Boundary Method

Taisuke Nambu1, Hiroki Yao2, Takuhito Kuwabara3, Ryohei
Kirihara3, Yasuhiro Mizobuchi1
Japan Aerospace Exploration Agency, Japan, 2Ryoyu systems, Japan, 3FMIC
R&D, Japan

1

This presentation shows ongoing research and development efforts on the combustion flow analysis program,
HINOCA, with a focus on detailed simulations of reciprocating engines using large-scale computer. A bottleneck
in performing detailed combustion flow analysis of motoring and firing of reciprocating engines is the computational grid generation cost associated with geometry motion.
The analysis program uses the Cartesian grid method
and an Immersed Boundary (IB) method, which significantly reduces the computational grid generation costand achieves good performance in large-scale parallel
computation. However, the use of the Cartesian grid and
IB method is known to cause problems such as reduced
accuracy near shape walls and poor conservatism. Ongoing research and development efforts are underway to
improve these aspects.
This presentation provides an overview of the analysis
methodology used by HINOCA, including analysis examples. The analysis based on the Cartesian grid method
and the IB method shows that it is possible to analyze
reciprocating engines with many complex geometries withthe same or better accuracy than the analysis using a
conventional boundary-fit grid method.
Contact: nambu.taisuke@jaxa.jp

Conceptual Study of High Efficiency
Reciprocating Engine with Pre-chamber
Combustion
Takayuki Ito1, Masahiro Matsuoka1, Toru Takabayashi2
1Japan Automobile Research Institute, Japan, 2Honda Motor Co., Ltd., Japan

This presentation shows ongoing conceptual study ofthe spark ignition engine by using combustion flow analysis program HINOCA, which uses the Cartesian grid method and an Immersed Boundary (IB) method and involves
many physical and chemical sub models to represent thecomplex phenomena in engine combustion. HINOCA provides the useful information to explore the newly method
for improving the engine combustion such as the suppression of the cycle-by-cycle variation with its scalability on
the large-scale computer. We focus on the use of active
type of pre-chamber which enables to enhance the leanlimit for highly efficient lean combustion. The pre-chamber combustion has potentiality for significant reductionof the combustion instability when the ultra-lean premixture is applied to aim the achievement for high-efficiency
gasoline engines. Furthermore, we found that the utilization of the autoignition around the jet flame improves thethermal efficiency due to rapid combustion and reductionof the unburnt fuel near the in-cylinder wall.
This presentation introduces the recent our parametric study for the effects of the compression ratio andin-cylinder condition such as gas composition on the heatrelease rate profile and the potentiality for the improving
the thermal efficiency.
Contact: titoh@jari.or.jp

Approach to Carbon Neutral Fuel Engine
Combustion Analysis Using Ansys Forteand Model Fuel Library
Junya Fukuyama
Ansys Japan, Japan

As countries around the world move toward carbon
neutrality, the transportation sector, including passenger

37

MS08 Advances in Detailed Numerical Simulation of Reciprocating Engines

cars (two-wheeled and four-wheeled), trucks, and ships,
construction machineries, and agricultural machineries, aswell as stationary generators are required to switch to alternative fuels that reduce CO₂ emissions. Under such circumstances, hydrogen engines are attracting attention asa new alternative to conventional diesel and gasoline engines. In this presentation, the three-dimensional combustion simulation approach will be explained, which is one of
the essential simulation technologies for hydrogen engine
development. Ansys has been working on combustion
simulation for carbon-neutral fuels for many years. Fuelmodeling is also important to appropriately express the
combustion process, Ansys has built a Model Fuel Libraryand uses these fuel characteristics to perform combustion
analysis with Ansys Forte. The latest development efforts
and simulation examples for hydrogen engine combustionin Ansys will be demonstrated.

the calculations was examined.
Contact: thori@mech.eng.osaka-u.ac.jp

Contact: junya.fukuyama@ansys.com

Numerical Analysis of Soot Contamination
Process in Diesel Engine Combustion
Tsukasa Hori1, Shohei Ueno2, Shinya Sawada2,
Fumiteru Akamatsu1
1

Osaka University, Japan, 2Osaka Univeristy, Japan

Combustion improvements and the use of aftertreatment systems have reduced soot emissions fromengines. On the other hand, depending on the engine
conditions, soot may be introduced into the engine oil due
to impingement of the spray flame on the combustion
chamber liner, resulting in deterioration of the engine oil
performance. In the case of diesel engines, it is believedthat soot adheres to the engine oil film on the cylinder
liner wall due to the impingement of the spray flame on
the wall, and that the sliding motion of the engine pistontransports the soot to the oil pan, where it is mixed into
the engine oil. However, although prediction models havebeen developed for soot itself, few models have been developed for soot deposition on walls. The objective of thisstudy was to predict soot contamination of oil in diesel engines. An engine combustion simulation code developedby the authors was used for the calculations. PRFs of cetane and isocetane were used as the fuel reaction mechanism. PAH formation by gas phase reaction is considered
up to pyrene. Soot formation from pyrene was calculatedusing the method of moments. Then, a soot adhesion
model that takes thermophoretic motion into account wasdeveloped for the moment method and incorporated into
the numerical analysis code. Numerical calculations were
performed for engine conditions in which soot contamination with engine oil was measured, and the accuracy of38

19th International Conference on Numerical Combustion

MS09 Numerical Combustion Research on
Fundamental Phenomena in Automobile Engines
Organizers: Shinji Nakaya1, Tsukasa Hori2
The University of Tokyo, 2Osaka University

1

MS09 Numerical Combustion
Research on Fundamental
Phenomena in Automobile
Engines
Chair: Shinji Nakaya
Co-Chair: Tsukasa HoriThursday, May 9; 09:50 - 12:10; Room J

Numerical analysis of the initial flame
kernel development with spark channel
elongation in spark ignition process under
turbulent tumble flow conditions using
LES/FGM
Shinji Nakaya, Fangsi Ren, Mitsuhiro TsueThe University of Tokyo, Japan

A numerical simulation model on the spark ignition
process in lean-combustion spark ignition (SI) engines
operating under high flow speed turbulent conditions wasdeveloped. The model employs Large Eddy Simulation(LES) coupled with a tabulated chemistry based on the
flamelet generated manifold (FGM). The numerical model
incorporates the elongation, restrike, and shortcut modelsof the spark discharge channel, considering the electric
circuit and the spatial distribution of local electric fields.
Three-dimensional LES simulations were conducted toinvestigate the spark ignition process in turbulent tumble
flows for lean gasoline or ethanol mixtures in a rapid compression machine, operating at elevated temperaturesand pressures. The results indicated that the numericalmodel successfully reproduced elongation, shortcut, andrestrike behaviors observed in experimental studies. Qualitative agreement with experimental data was achievedin the initial flame kernel development, even with a tabulated chemistry of Flamelet-Generated Manifold (FGM)
models. The size of the flame kernel was confirmed wellwith the experimental one. Additionally, the numerical results represented local quenching behaviors observed in
the experiments, demonstrating the model's capability tocapture detailed combustion phenomena. The influenceof Lewis number on the spark ignition process was also
explored in the present study.
Contact: tsnakaya@mail.ecc.u-tokyo.ac.jp

Effect of flame quenching distance andflame-wall geometry on the near-wall CO
formation for turbulent premixed CH4-air
combustion in a constant volume vessel
Ye Wang, Mamoru Tanahashi
Tokyo Institute of Technology, JapanA three-dimensional direct numerical simulation has
been conducted for the turbulent premixed CH4-air combustion in a constant volume vessel. The local near-wallflame quenching positions of turbulent flame-wall interaction process are identified based on the flame’s local fuelconsumption speed, and the CO emission of near-wallflame is investigated for its correlation to the local nearwall flame quenching distance and flame-wall geometry.
The results show that, the local flame gets near-wallquenched primarily with a head-on quenching configuration. Meanwhile, the physical barrier effect of wall causes the “lack of fuel” in the flame front and that further
leads to the statical reduction of CO emission during thenear-wall flame quenching process. Additionally, the COemission exhibits dependence on both local quenching
distance and quenching mode (flame-wall geometry): a
greater level of CO emission rate can be found on thenear-wall flame with a longer quenching distance or underquenching mode of back-on quenching (flame oriented
far from the wall), as the flame front can be better exposed to the unburned mixture. Moreover, the behaviors
of CO-related elementary reactions are also investigatedto support the current findings.
Contact: wang.y.by@m.titech.ac.jp

MS09 Numerical Combustion Research on Fundamental Phenomena in Automobile Engines

Combustion characteristics of ammoniahydrogen mixtures by turbulent jet
ignition
Dong Han, Jinlu Huo

Shanghai Jiao Tong University, China

Ammonia, as a hydrogen carrier and zero-carbon fuel,holds promise for achieving zero carbon emissions frominternal combustion engines. The pre-chamber turbulent
jet ignition, characterized by multi-point distributed ignition and rapid combustion, could be applied to ammonia
combustion to extend combustion limits and stability. This
study investigates the impacts of hydrogen energy fraction and equivalence ratio on the ammonia-hydrogen mixtures jet ignition in a constant volume combustion chamber with pre-chamber ignition system by CFD Simulation.
The results indicate that, with high hydrogen content andnear-stoichiometric combustion conditions, the flame
thickness decreases. This allows the fire nucleus to penetrate the main-chamber, even with the jet hole stretchingeffect and heat loss, forming the flame ignition. When thehydrogen energy fraction decreases or the equivalence
ratio drops, the increased flame thickness lead to thepre-chamber flame being easily and completely quenched
as it passes through the jet orifice, resulting in the formation of a jet into the main-chamber that contains only
the combustion thermal products. In comparison to theflame ignition, the jet ignition demonstrates a prolonged
ignition delay time, with ignition occurring at the jet tip,
distanced from the pre-chamber outlet. Therefore, thehot jets formed by ammonia-hydrogen fuel mixtures withhigh hydrogen ratios or stoichiometric mixtures provide
advanced main-chamber mixture ignition and stronger jet
flow.
Contact: dong_han@sjtu.edu.cn

Numerical Simulation of Spark Ignition
Processes Considering Preferential
Diffusion and Thermal Plasma
Tsukasa Hori1, Naohiro Yoshinaga1, Shota Yamada2,
Yusuke Oda1, Shinya Sawada1, Fumiteru Akamatsu1
1

Osaka University, Japan, 2Osaka Univeristy, Japan

In order to improve the thermal efficiency of spark-ignition engines, there is a need to predict the success or
failure of spark-ignition and flame kernel growth for lean
mixtures. In recent years, the prediction of sub-chamber
ignition and ignition for mixtures of hydrocarbon fuel,ammonia and hydrogen have become promising. It is
required to predict the preferential diffusion effect appropriately for the mixing composition in addition to improv-

40



ing the prediction of spark discharge such as discharge
path elongation and re-discharge. Preferential diffusion
effects can be taken into account by considering multi-component transport properties. On the other hand, thesimulation considering plasma requires time resolution tocapture the transfer of electrons. From the viewpoint ofcomputational load, it is difficult to predict from the startof discharge to the flame kernel growth. In this study, wedeveloped an numerical simulation method of spark ignition process that takes thermal plasma into account. By
assuming local equilibrium and considering spark ignition
plasmas as thermal plasmas, flame kernel growth calculations can be performed without changing the calculation
time scale due to the introduction of plasma. In addition,
the simulation considering thermal plasma predicts theelongation process of the discharge path and the flow associated with the discharge. In this talk, we will introduce
the development of a numerical simulation for spark ignition that takes into account preferential diffusion effects
and thermal plasma, and the simulation results of spark
discharges and flame kernel growth.
Contact: thori@mech.eng.osaka-u.ac.jp

Autoignition behaviour of n-heptane
studied using 2D DNS
Ajit Kumar Dubey1, Youhi Morii2, Kaoru Maruta2
1

Indian Institute of Technology Roorkee, India, 2Tohoku University, Japan

This work presents 2D DNS study at higher initial temperatures where the end-gas autoignition changes its
nature. The autoignition center moves away from the end
wall as the initial mixture temperature increases. This is
attributed to the multiple reflections from the side walls
in 2D enclosure due to which higher temperature regionis created inside the domain and away from the wall. As
the initial temperature increases from 1100 K to 1200 K
autoignition kernel moves further away from the endwall. In 2D DNS, the autoignition is initiated at significantly
lower level of temperature inhomogeneity as comparedto 1D DNS. The autoignition modes are also influenced byincrease in pressure. The autoignition center moves towards spark ignited flame front as the pressure increases
and new modes are observed at significantly higher pressure.
Contact: ajit.dubey@me.iitr.ac.in

19th International Conference on Numerical Combustion

MS09 Numerical Combustion Research on Fundamental Phenomena in Automobile Engines

Prediction of Knock Intensity for an
Optical SI Engine with Various Primary
Reference Fuels
Jiabo Zhang1, Shi Hao2, Dong Han1, Zhen Huang1

Shanghai Jiao Tong University, China, 2King Abdullah University of Scienceand Technology, Saudi Arabia

1

To provide fundamental insights into the underlying
mechanisms of knock occurrence in a spark-ignition (SI)engine, optical diagnostic measurements were performed
at advanced spark timing under boosted conditions. Employing high-speed imaging, deflagration-to detonationtransition (DDT) processes were recorded. The relationships between the unburned mixture fraction (UMF) andtwo metrics associated with the knock intensity levels,
namely the maximum amplitude of pressure oscillation(MAPO) and the peak in-cylinder pressure, Pmax, were examined. In contrast to common beliefs, we found that theknock intensity represented by MAPO is not strongly correlated with UMF, because UMF alone is inherently insufficient to represent the thermo-chemical properties of thebulk mixture inhomogeneities and its chemical reactivity
at the onset of end-gas autoignition occurrence. Instead,a much stronger correlation was found between UMF
and a newly proposed normalized-peak-pressure metric,
allowing an a prior prediction of Pmax, which is a criticalparameter associated with the propensity of engine failure if Pmax exceeds the strength limit of the engine. To
quantitatively predict MAPO under SI-engine conditions,a refined model was proposed by imposing the pressure
and temperature traces into the zero-dimensional (0-D)
reactor model, such that the thermochemical propertiesof the transient mixture state at the onset of end-gas
autoignition are properly incorporated into the predictive
criteria. The model is proved to reliably predict the endgas autoignition and the knock intensity levels dictatedby MAPO regardless of the stochastic nature of the knock
development process and fuel types.

the solid phase and the gas phase during a combustion
process. The influence of the solid on the flame structuresand flame properties as well as the influence of the flameon the thermo-mechanical behavior in the solid are investigated with the focus on internal combustion engines
conditions. A stagnation flow flame close to a plane wallis considered as a representative model, which is simple
but also relevant for many engineering conditions. The
numerical simulation of the combustion process is basedon detailed chemical mechanisms and detailed moleculartransport models including thermal diffusion. The modelfor the solid is based on the thermo-elasticity assumption. We present a fully coupled solution of the governing
equations for the solid and the gas phase. As a result, it isshown that the plane wall (e.g. its heat conductivity) cansignificantly affect the flame properties (e.g. its stability
against extinction), and the flame, in return, can affect thethermal stresses in the plane wall, and the solid is more
likely to undergo a plastic deformation at high pressures.
Contact: chunkan.yu@kit.edu

Contact: zhangjiabo@sjtu.edu.cn

Numerical investigation of the effect of
combustion process on material thermalload under internal combustion engines
conditions
Chunkan Yu, Ulrich Maas

Karlsruhe Institute of Technology, Germany

While thermo-mechanical analysis in solids and combustion processes in the gas phase have been intensively
studied separately, their interaction is less investigated.
This talk focuses on the coupling between processes in

41

MS10 Sustainable Aviation Fuel: Modeling
Challenges and Opportunities
Organizers: Shashank Yellapantula1, Jacqueline H Chen2
National Renewable Energy Laboratory, 2Sandia National Laboratories

1

MS10 Sustainable Aviation
Fuel: Modeling Challenges andOpportunities

es associated with SAFs will be discussed.

Chair: Shashank Yellapantula
Co-Chair: Jacqueline H Chen
Friday, May 10; 09:50 - 11:50; Room C

Modeling sustainable aviation fuelcombustion kinetics with a functionalgroup approach

Challenges and Opportunities in Using
Numerical Simulations for Increased
Adoption of Sustainable Aviation Fuels

Shashank Yellapantula, Bruce Perry, Sreejith Nadakkal
Appukuttan, Marc Day
National Renewable Energy Laboratory, United States

Liquid fuels from bio-derived sources, sustainable aviation fuels (SAF), are currently the most promising avenue
to decarbonize aviation. Currently, there are seven fuels
produced from various sustainable feedstocks that are
certified to use in commercial aviation in US. All of theseseven fuels, also known as drop-in fuels, need to be blended with petroleum based jet fuels at various blend ratios,
maximum being 50%. In order to achieve significant
decarbonization several 100% drop-in fuels need to becertified and the production process scaled up to millionsof gallons. However, cost and amount of fuel needed for
certifying a new synthetic fuel presents a major challenge.
To de-risk certification of 100% drop-in SAF, simulations
provide a cost-effective alternative to screen several fuelcandidates in a time efficient and cost-effective manner.
In this mini-symposium, we will highlight challenges andopportunities for simulation of aircraft engine combustors
with a specific goal of faster and cheaper routes to adoption of 100% SAF. As a part of this mini-symposium, thisfirst talk will introduce the concept of drop-in SAF, the SAF
certification process, and highlight the risks associated withthis process. Additionally, the talk will highlight the criticalrole that simulations can play to de-risk and reduce costsof newer SAF certification. Finally, the talk will introduce all
the following talks where all aspects of modeling challeng-42

Contact: shashank.yellapantula@nrel.gov

Pierantonio Lo Greco1, Sirio Brunialti1, Qi Wang1, Xiaoyuan
Zhang2, Mani Sarathy1
1

KAUST, Saudi Arabia, 2USTC, China

Sustainable aviation fuels have the potential to replace
conventional petroleum derived fuels in long-haul flights.
The chemical composition of SAFs determines their
combustion properties and performance in flight. It is
important to determine how feedstock variability and variations in SAF production processes impact fuel chemicalcomposition and combustion kinetics. Here, we present afunctional group approach to (FGMech) simplify the kinetic modeling of SAF combustion. The FGMech methodology enable rapid development of reaction mechanisms,
thermodynamic data, and transport data for real fuels withcomplex chemical composition. The FG-Mech approachis used here to develop kinetic models for conventional
Jet-A1 and SAFs produced by hydrotreating of fatty acids(HEFA). The kinetics models are validated by comparing
predicted results of C2H2 and C3H4 with experimental
shock tube measurements. Subsequently, the kinetic model is merged with a PAH formation mechanism and results
are compared with simple reactor experiments. Finally themechanisms for NOx, sulfate and nucleation-growth-oxidation of soot are added. Furthermore, the FGMech models are applied to simulate emissions from a turbofan (withemphasis on NOx, CO and soot). The emission model
also implements a variable distribution of mass flow rates
in the burner as a function of engine operating conditions.
The model’s predicted values are compared with experimental measurements from NASA APEX and ACCESS
campaigns to assess the model’s accuracy.
Contact: mani.sarathy@kaust.edu.sa

19th International Conference on Numerical Combustion

MS10 Sustainable Aviation Fuel: Modeling Challenges and Opportunities

A perspective on supercritical fuel-flow
modeling needs with SAF
Guillaume Ribert

CNRS & INSA de Rouen, France

The critical point of any pure substance can be definedby the highest pressure and temperature, for which distinct liquid and gas phases can be observed. When thepressure exceeds such critical pressure, the distinction between gas and liquid vanishes, and real-gas effects must
be addressed. For binary and other multicomponent fluids,
several locations of critical points are found depending on
the concentration of each fluid. Such phenomena are classically encountered in rocket engine applications but canalso appear in gas turbines, particularly if sustainable aircraft fuels (SAF) are used. This high level of pressure has
a direct impact on the flow Reynolds number through thekinematic viscosity. The Reynolds number increases withpressure involving a decrease of the Kolmogorov scalewith consequences on the mesh requirements. Furthermore, under these severe thermodynamical conditions,flames become very thin with steep density gradients,
meaning a modeling effort is required for both turbulent
flow description and propulsion applications. An overview
of the different challenges related to this research theme
will be detailed in the context of using SAF for aeronautical propulsion.
Contact: guillaume.ribert@insa-rouen.fr

Toward comprehensive manifoldbased combustion modeling of multicomponent Sustainable Aviation Fuels in
turbulent reacting flows
Michael Edward Mueller, Israel J Bonilla, S Trevor Fush,Philip Satterthwaite
Princeton University, United States

Multi-component liquid fuel combustion poses several
computational modeling challenges. Multiple fuel components requires the use of large chemical mechanisms,
which are generally computationally intractable with “brute
force” combustion modeling approaches so requires reduced-order manifold-based combustion models. The fuelcomponents may have varying rates of vaporization, so
the manifold-based model must accommodate a diversityof local fuel compositions, increasing model dimensionality. Additionally, liquid fuel combustion with varying
vaporization rates can exhibit complex multi-regime combustion. In this work, progress toward a comprehensive
manifold-based combustion model for multi-component
liquid fuel combustion is detailed. To accommodate varia-

43MS10 Sustainable Aviation Fuel: Modeling Challenges and Opportunities

tions in the local fuel composition, the local fuel composition is considered as an input to the manifold-based model. The importance of the local fuel composition on thethermochemical state is demonstrated with a particularemphasis on emissions. To accommodate this relatively
high-dimensionality of the manifold-based model, In-Situ Adaptive Manifolds (ISAM) computes solutions to the
manifold equations ‘on-the-fly’ and stores them for reuselater in the simulation. The performance and scalabilityof ISAM in LES with chemical mechanisms of varying size
from ten species to hundreds of chemical species andwith different “fuel” dimensionalities are assessed. Finally, generalization of the model to complex multi-regime
combustion is discussed including both multi-modal combustion and quasi-staged combustion.
Contact: muellerm@princeton.edu

Experimental Approaches for Validationof SAF Combustion
Tonghun Lee, Audrey Godsell, Casey O'Brien, Paxton
Wiersema
University of Illinois Urbana-Champaign, United States

This presentation will outline an effort to develop a
new compact test rig (M1 combustor) for prescreening
sustainable aviation fuels (SAFs) prior to tier 3 and 4 tests
in the ASTM D4054 evaluation process. The M1 combustor is designed to operate on a small quantity of fuel,and its combustion characteristics for various fuels arecharacterized using state-of-the-art laser and optical diagnostics including multiphase X-ray measurements at theAdvanced Photon Source (Argonne National Laboratory).
The goal is to provide an open architecture that can beutilized for prescreening of SAF as well as provide high-fidelity data for validation of numerical models. Combustor
test results of lean blow out and ignition, based on a variety of fuels with varying properties representative of SAF,
will be presented. Additionally, the presentation will coversome of the latest work in rapid optimization of chemical
kinetics models for SAF which can be utilized in modeling the M1 combustor. This includes utilizing advanced
machine learning based analysis to understand the uncertainty space when models are optimized using limited
experimental data.

Combustion dynamics in a lab-scale
combustor using DNS

Bruno S. Soriano, Christian Lacey, Jacqueline Chen
Sandia National Laboratories, United States

The combustion process in aero-engines is a resultof complex interactions between multi-phase flows withdifferent fuel properties, mixture preparation in turbulent
flows and complex chemical reactions. The liquid injectionof multi-component fuels often results in partially-premixed mixture preparation which can also vary in termsof fuel composition and generate complex multi-mode
combustion. Fuel pyrolysis and mixing of the various fuelfragments with the local mixture increases the dimensionality of the problem. The presence of extinction andreignition in stringent conditions near flame blow-off increases the difficulties to correctly model the combustion
process for engineering simulations. The flame sensitivity
to blow-off has been observed to be related to the fuelpropensity to ignite, measured in terms of the derived cetane number. In this work, combustion dynamics involvedin jet fuel combustion is investigated using a laboratory-scale swirl-stabilized spray flame modeled using direct
numerical simulation. Simulations are performed for two
fuels with dissimilar cetane numbers: the first with thecommercially available Jet-A; and the second with Alcohol-To-Jet, a low cetane number Sustainable Aviation Fuel(SAF) called C1. The combustion dynamics is investigatedin terms of the combustion modes and the propagation
mode of the edge flames generated from local extinction
at the stoichiometric mixture fraction. Statistics in termsof the edge flame displacement speed are also analyzed
for the two fuels. Finally, modeling closures in the context
of multi-modal combustion are discussed.
Contact: bsouzas@sandia.gov

Contact: tonghun@illinois.edu

44

19th International Conference on Numerical Combustion

MS11 Liquid Rocket Engine Combustion
Organizers: Takanori Haga1, Taro Shimizu1, Hiroshi Terashima2
Japan Aerospace Exploration Agency, 2Hokkaido University

1

MS11 Liquid Rocket Engine
Combustion
Chair: Taro Shimizu
Co-Chair: Hiroshi Terashima
Thursday, May 9; 09:50 - 12:30; Room G

Large-Eddy Simulations of subscale LOX/
GH2 rocket combustors with different
fuel injection temperatures
Takanori Haga, Taro Shimizu

Japan Aerospace Exploration Agency, Japan

Large-eddy simulations are performed for subscalerocket combustors by solving the compressible Navier-Stokes equations with the flamelet progress variable
model. To account for real-gas thermodynamics andtransport of the cryogenic propellants, the Soave-RedlichKwong equation of state and Chung’s model are used. Inhouse solver “LS-FLOW-HO” is used, in which the high-order flux-reconstruction scheme is employed on overset
unstructured hexahedral grids.
First, a single coaxial injector case tested at JAXA Kakuda Space Center is considered. To reproduce the injector
acoustic modes with proper upstream boundary conditions, the geometry of the injection manifolds is includedin the simulation. The computed power spectral density(PSD) of the pressure was compared with the experimental data, and the overall characteristics agreed reasonably
well. In the higher amplitude case, interference between
LOX core and GH2 annular flow occurred in the recessedregion at the injector end, and coupling of the core deformation and the injector 1L mode was observed.
Next, LES of DLR BKD 42 injectors is conducted. In theexperiment, higher amplitude of 1T mode was observed in
the higher hydrogen temperature case LP4. The computed combustion pressure and the PSD will be comparedwith the experiment and the characteristics of the combustion flow field will be discussed.

Injection parameter identification forsevere pressure oscillations in a highpressure H2/O2 rocket-type chamber

Riku Shimoyama, Atsushi Kubota, Hiroshi Terashima
Hokkaido University, Japan

Combustion instabilities are a severe problem fordeveloping liquid rocket engines. The combustion instabilities may generate large pressure oscillations, causing
severe damage to the combustion chamber. This study
numerically investigates the effects of injection velocity
and mixture ratios on the combustion instability in H2/O2
rocket-type engines with low-temperature injection. The
compressible Navier-Stokes equations, including the species-mass equations, are solved with a detailed chemical
kinetic mechanism. The results indicate that the combustion instabilities with strong pressure waves are generated under low-velocity or low mixture ratio conditions.
The instability conditions using the velocity and mixture
ratios agree with several experimental data. The results
also suggest that the low-temperature injection may not
be a primary cause of the combustion instabilities. Whenstrong instabilities occur, some unburned hydrogen remains downstream. The local Rayleigh index indicatesthat the unburned hydrogen remaining in a downstream
region causes the interaction between the exothermic
fluctuations by combustion reactions and pressure fluctuations in a chamber. Therefore, the present study suggests that the unburned hydrogen remaining downstream
is a primary cause of the combustion instabilities withstrong pressure waves. The injection velocity and mixture
ratios, which indicate the amount of unburned hydrogen
downstream, are a metric for predicting combustion instability.
Contact: shimoyama.riku.r1@elms.hokudai.ac.jp

Contact: haga.takanori@jaxa.jp

45

MS11 Liquid Rocket Engine Combustion

Characterization of injectors near field in
LRE firing plates

Pasquale Eduardo Lapenna1, Arianna Remiddi2, Marco
Pizzarelli3, Rocco Pellegrini3, Enrico Cavallini3, Mauro
Valorani2, Francesco Creta2
1

Sapienza University of Rome , Italy, 2Sapienza University of Rome, Italy,
Italian Space Agency, Italy3

Liquid Rocket Engines (LRE) are usually characterized by extreme conditions in terms of temperature andpressure, making the experimental investigation of suchdevices complex and often limited to indirect measurements. The injection region, in particular, lacks a thoroughdescription from both the experimental and numericalstandpoints. In this framework, the interest toward variable-fidelity computational fluid dynamics (CFD) simulations is rapidly increasing with a twofold aim. On one
hand, high-fidelity simulations such as large eddy simulations (LES) and direct numerical simulation (DNS) can provide data and information which are typically hindered toexperiments. Low-fidelity simulations like unsteady RANS,
on the other hand, can be used to characterize large andcomplex domains and to develope reduced order models
for simulations at the system level. This contribution aims
at the characterization of the injectors near-field regionof rocket combustion chambers, with particular attention
devoted to the mixing and recirculation region, and comprising the effects of the injector layout on the ensuingflow field and thermal load. The work will leverage the useof a tabulated chemistry approach coupled with multi-fidelity solvers ranging from unsteady RANS to LES, and will
be based on reference test cases widely validated in therocket community.
Contact: pasquale.lapenna@uniroma1.it

Modeling of Wall Heat Flux in Liquid
Rocket Engines
Matthew Harvazinski

tions taking place in the near wall region, model the heattransfer into the solid wall, and account the radiation loss
inside the combustor. For example, simulations without
reactions can lead to errors of 2-5 times in the wall heat
flux. In this study a series of simulations is done using different levels of fidelity to demonstrate the resolution andmodels required to accurately capture the wall heat flux ina liquid rocket engine.
Contact: matthew.harvazinski.1@us.af.mil

Determination of the Drop Size andDistributions during Liquid Injection:
Impinging and Effervescent Sprays
Jungeun Park, T.-W. Lee

Arizona State University, United States

Determination of drop size is important in propellant
and other injection processes. Evaporation and subsequent combustion are predicated on the initial drop diameter and its distributions. For this reason, many models
exist. In place of modeling, we have developed an analytical framework based on integral form of the conservation
equations, which leads to an expression for the Sautermean diameter as a function of the injection and fluid parameters. This has been validated for the basic injection
geometries, and in this work we demonstrate extension
and applicability to spray flows for propellant injection:
impinging and effervescent sprays. Again, the results arecompared with experimental data. In addition to providing
quantitative predictions of the drop size and distributions,
physical mechanisms of the spray atomization processes
can be understood withing this framework. For impinging
sprays, it is the cancellation of the lateral momentum andkinetic energy that leads to the formation of small droplets. This algorithm can also be combined with computational fluid dynamics for efficient and accurate simulationsof propellant injection.
Contact: attwl@asu.edu

United States Air Force Research Laboratory, United States

Heat transfer plays an important role in liquid rocket
engines, a large amount of heat is transferred from the
combustor to the walls of the engine. Walls can also play
an important role in the thermal management of the device because of regenerative cooling. Accurately modelingthe wall heat transfer is difficult because of the added resolution and sophistication of the models required. In thisstudy we look at using both conjugate heat transfer andradiation heat transfer to capture the wall heat flux in alaboratory scale rocket engine. Simulations show that toaccurately capture the wall heat flux you must capture thethermal boundary layer, account for the chemical reac-46

An efficient numerical algorithm forsolving multi-component real fluid flows
in rocket engines
Sho Wada1, Reo Kai2, Abhishek Lakshman Pillai1, Ryoichi
Kurose11

Kyoto University, Japan, 2Kyushu University, JapanTo reduce the development costs and improve thereliability of rocket engines, model-based development
is necessary, which uses numerical simulations in theearly design stage to evaluate the stability and efficiency

19th International Conference on Numerical Combustion

MS11 Liquid Rocket Engine Combustionof rocket engines under operating conditions. However,numerical simulations of transcritical fluids in rocket engines suffer from the small time-step size limitation due
to the acoustic CFL number and numerical instabilities
arising from spurious pressure oscillation at the materialinterface, which lead to high computational costs anddivergence of calculations, respectively. To address theseissues, using a semi-implicit algorithm employing a method to mitigate spurious pressure oscillations at materialinterfaces appears to be a promising approach. In thisstudy, a semi-implicit pressure-based solver that reduces
the computational cost by over 90% compared with theclassical explicit density-based solver has been developed
for multicomponent real-fluid inert systems. This is a preliminary step towards our goal of applying this algorithm
to the transcritical combustion field in the future. The validity of the developed algorithm is tested with benchmark
1D and 2D numerical problems, and its results and computational cost are compared with those of the classicaldensity-based explicit solver.

exhibited by the LOX/GH2 surface due to the inhomogeneities generated by injection.
Contact: nguyenly@stanford.edu

Contact: wada.sho.88z@st.kyoto-u.ac.jp

Interface-Capturing Simulations ofTranscritical LOX/GH2 Injection using
Unified-Fluids Regularized-Interface
MethodNguyen Ly, Matthias Ihme
Stanford University, United States

In modern rocket engines, cryogenic propellants are
injected into a high-pressure combustion chamber tomaximize thermodynamic efficiency and performance.
Specifically, examples of LOX/GH2 injection engines
operating at supercritical pressures with respect to thecritical point of oxygen are found in the main-stage engines of SLS and Ariane 6. Despite the wide adoption, thephysical mechanisms for mixing between LOX and GH2
streams remain poorly understood. One principal issue
is the immiscibility of oxygen and hydrogen, resulting in
the existence of liquid/vapor interfaces even at arbitrarily
high-pressure conditions, when the surface temperature
is below the mixture critical point. Thus, the investigationof the spatio-temporal transition of the LOX/GH2 surface
between subcritical evaporation and supercritical mixing
remains an open challenge. To address this, we present a
Regularized-Interface Method (RIM) that was derived fromup-scaling the nanoscale interface-resolving methods
based on the Linear Gradient Theory of Van der Waals,
thus allowing for the unified interface-capturing simulations of both subcritical interfacial and supercritical mixing
dynamics. Using this method, we numerically analyze thecomplex spatio-temporal transcritical transition dynamics



47

MS12 Spread of ammonia combustion research- Role of numerical simulation Organizers: Hisashi Nakamura1, Ekenechukwu C Okafor2
Tohoku University, 2Kyushu University

1

MS12-1 Spread of ammonia
combustion research - Role ofnumerical simulation - (1)Chair: Hisashi Nakamura
Co-Chair: Ekenechukwu Chijioke Okafor
Wednesday, May 8; 10:40 - 12:40; Room D

Secondary Air Dilution of the Primary
Combustion Zone of Two-Stage RichLean Ammonia Combustors; A Numerical
Study of the Effects on Emissions Control

Ekenechukwu Chijioke Okafor1, Hirofumi Yamashita2,
Osamu Kurata3, Norihiko Iki3, Takahiro Inoue3, Hyun Jo3,
Masayasu Shimura3, Taku Tsujimura3, Akihiro Hayakawa2,
Hideaki Kobayashi3,

Kyushu University, Japan, 2Tohoku University, Japan, 3National Institute ofAdvanced Industrial Science and Technology, Japan

1

Experimental studies in two-stage gas turbine combustors suggest that the secondary air injected downstreamof the combustor may flow towards the primary zone forsufficiently large secondary air flow rates. This diluting
effect of the secondary air on the primary zone may limit
the potentials of two-stage rich-lean combustion andinhibit flame stabilization. In this study, large eddy simulations of flows in models of two-stage gas turbine combustors were conducted using a reduced reaction mechanism
to study the effects of the uncontrolled primary zone
dilution on ammonia-methane-air combustion and emissions control at various primary zone equivalence ratios. It
was found that the dilution event encouraged NOx emission due to non-uniformity of the mixture in the primaryzone. By controlling the flow of secondary air towards theprimary zone, a higher combustion temperature and amore uniform equivalence ratio in the primary zone wereachieved, which enabled a better control of NOx emission.
However, emissions of unburned fuel species such as
NH3, H2, HCN and CO could be encouraged when primaryzone dilution is mitigated because of insufficient mixing of
the hot gases from the primary zone and the secondary
air in the secondary zone. It was found that the emission48

of N2O from two-stage rich lean combustors is mainly
due to its production in the secondary zone.
Contact: ekene.okafor@mech.kyushu-u.ac.jp

Effect of Secondary Fuel Injection inAmmonia / Natural Gas Co-Fired Gas
Turbine Combustor

Shintaro Ito, Masahiro Uchida, Yusuke Komatsu, Toshiro
Fujimori
IHI corporation, Japan

Ammonia is gaining recognition as a fuel for CO2 reduction, but technology development is required to establish and expand the value chain. Especially, developmentof low NOx combustion technology is crucial to promote
the use of ammonia as a fuel. In this study, technology to co-fire 20% ammonia with natural gas for 2 MWclass gas turbines was developed. Two-stage combustion
method is adopted for ammonia / natural gas co-firing
to achieve low NOx combustion. Through computationaland experimental study using two-stage combustor, theeffect of ammonia supplying point on NOx emission wasinvestigated. In the computation, detailed reaction mechanism was used to investigate the process of low NOx
combustion. Comparison of numerical results showed thatNOx emissions were lower when all ammonia is supplied
to the secondary zone than when it is supplied to the primary zone. Comparison of flame structure suggested thatoxygen concentration in the ammonia combustion zone
affects NOx emission. Engine tests results using a 2 MWclass gas turbine confirmed a same tendency as a numerical simulation. These results clearly demonstrated theeffectiveness of secondary ammonia injection in reducing
NOx emission.
Contact: uchida7785@ihi-g.com

19th International Conference on Numerical Combustion

MS12 Spread of ammonia combustion research - Role of numerical simulation -Multi-Scalar Flamelet Approach for
Simulating Ammonia Co-firing Burners
Kozo Aoki, Hiroyuki Takeishi, Keisuke Miura, Kenji
Yamamoto
Mitsubishi Heavy Industries, Ltd., JapanThe objective of this work is to construct and verify
the two-stream premixed flamelet approach in gas-gas
dual fired burners. A numerical framework using large
eddy simulations (LES) combined with Flamelet Generated
Manifolds (FGM) are applied to ammonia-methane flames.
Premixed flamelet library for ammonia-methane combustion is constructed with two mixture fractions (ZNH3 andZCH4) since partially premixed combustion mode withlocally different ammonia-methane ratio appears in actual gas turbine combustors. A model swirl burner in theliterature, which has fuel supplying lines for ammonia-air
and methane-air mixtures individually, is selected for verification of the LES. A progress variable (C) and additional
non-dimensional parameters, Z=ZNH3+ZCH4 and A=
ZNH3/Z, are defined to construct a flamelet library in (Z,C, A) space. Turbulence-chemistry interaction in the subgrid scale is considered by using presumed beta PDF forthe variances of Z and C. Thus, the tabulated quantities
are parametrized by five parameters (Z, C, A, Z”, C”). LESof the elemental burner under the literature condition(21% overall NH3 ratio) successfully reproduces the flame
shape represented by OH-PLIF images. Differences in the
results between the present flamelet approach and detailed chemistry are also discussed in statistically.
Contact: kozo.aoki.z5@mhi.com

Numerical Investigation of Secondary
Injection System in Developing Low-NO
Ammonia Co-combustion Furnaces with
Detailed Chemistry and Conjugate Heat
Transfer
Yinan Yang, Tsukasa Hori, Shinya Sawada, Fumiteru
Akamatsu
Osaka University, Japan

In the context of utilizing ammonia for co-firing power
generation, the air-staged strategy is recognized as aneffective method for controlling NO emission due to its
ability to stage air input, thereby creating a fuel-rich region within the furnace. To investigate the NO formation
and reduction characteristics under various conditions
within an air-staged strategy employing the secondary
injection system, the present study utilized three-dimensional numerical simulations to investigate the impact of
the secondary nozzle diameter (D2) and the secondary

air ratio (λ2). The conjugate heat transfer (CHT) method is
utilized to accurately simulate thermal conditions at the
furnace walls. Results indicate that with a constant total
air ratio (λ = 1.2), simply increasing the secondary air ratio,
which promotes fuel-rich combustion in the primary combustion zone, does not correspond to a linear decrease in
NO emission at the furnace outlet. Instead, as the secondary air ratio increases, NO emissions at the furnace outlet
follow a V-shaped trend, minimizing when primary andsecondary air ratios are equivalent. Additionally, increasing the secondary nozzle diameter, thereby enhancing
fluid recirculatory motion, proves to be an effective meansof suppressing NO emissions. This study underscores that
adjustments in the secondary injection system parameters can significantly control NO formation, even without
extensive structural modifications to existing combustion
furnace infrastructure.
Contact: yang@combu.mech.eng.osaka-u.ac.jp

Numerical simulation of hightemperature air / ammonia / methane
mixing combustion for industrial furnaces

Nozomu Hashimoto1, Shinichiro Takemura2, Takeshi
Inoue2, Yunan Sakai1, Hisashi Nakamura3, Yusuke Konno1,
Osamu Fujita1
Hokkaido University, Japan, 2Rozai Kogyo Kaisha, Ltd., Japan, 3Tohoku
University, Japan

1

Ammonia is one of the promising fuels for future zero-carbon industries. By introducing ammonia as a fuelfor industrial furnaces, huge amounts of carbon dioxide
emissions from industrial furnaces can be reduced in the
future. In this study, the numerical simulations were conducted for the high-temperature air / ammonia / methane
mixing combustion field of the lab-scale burner and 465
kW class combustion test furnace. The predicted results
for the lab-scale burner by the numerical simulations
were validated by the measurement results of NH radical
concentration distributions obtained by Laser Induced
Fluorescence. The NH-radical concentration distribution
predicted by the simulation was consistent well with thatmeasured by the experiment. Employing the same simulation method, the numerical simulation for the combustion
field of 465 kW class combustion test furnace was also
conducted. The numerical simulation successfully precited the tendency of the exhaust gas NO concentration
reduction when the configurations of the oxidizer andfuel injection ports of the burner were changed. From theanalysis of the numerical simulation data, it was foundthat the essential for the NO concentration reduction of
the high-temperature air / ammonia / methane mixing
combustion is avoiding the NO formation from ammonia

49

MS12 Spread of ammonia combustion research - Role of numerical simulation -by creating the low oxygen gas composition region near
the injection of ammonia gas.
Contact: nozomu.hashimoto@eng.hokudai.ac.jp

MS12-2 Spread of ammonia
combustion research - Role ofnumerical simulation - (2)Chair: Hisashi Nakamura
Co-Chair: Ekenechukwu Chijioke Okafor
Wednesday, May 8; 13:30 - 15:10; Room D

Detailed Diffusion Effects on Thermal andChemical Kinetics in a Turbulent NH3/H2
Non-premixed Flame
Ahmed Abdelnasser Tawfik Adam, Reo Kai, Hiroaki
Watanabe
Kyushu University, Japan

Ammonia (NH3) and hydrogen (H2), as sustainable fuelsources, may become more important in achieving andcontrolling zero carbon emissions from combustion devices. A thorough understanding of detailed diffusion (DD)is necessary for the proper prediction of combustion processes fueled by NH3-H2, especially because of the higher
diffusivity of H2 compared with thermal diffusivity and diffusivities of O2 and NH3. Assuming that turbulent mixing
greatly exceeds molecular mixing, it is common practicein turbulent combustion simulations to ignore the effectsof DD, hence simplifying the modeling process. However,
it is important to understand that, despite this assumption
is valid for hydrocarbon fuels, it loses significance whenit comes to the burning of H2 because of the significant
influence of DD. In this work, two direct numerical simulations of a turbulent NH3/H2 non-premixed flame in the
mixing layer are conducted, one considers the DD andthe other assumes the unity Lewis number (ULN) to investigate the DD effect. It is found that the DD lets more
fuel diffuse toward the flame front, which enhances thestability of the flame significantly compared with the ULN
assumption.
Contact: adam.ahmed.542@s.kyushu-u.ac.jp

Modelling of turbulent premixed swirl
flames for 70/30 vol% NH3/H2 fuel-air
mixtures

Joanna Jójka1, Ali Alnasif2, Syed Mashruk2, Agustin ValeraMedina2Poznan University of Technology, Poland, 2Cardiff University, United
Kingdom1

Accurate prediction of ammonia turbulent combustion emissions is crucial for the further development of
combustion systems. Fuel-air mixtures with a 70/30 vol%NH3/H2 ratio were numerically investigated for a premixed burner setup with a fixed power of 10kW.
RANS calculations were performed with Reynolds
stress transport using a complex chemistry and species
transport model with respect to thermal and mixture averaged diffusion. Turbulence-chemistry interaction wasmodelled using the Eddy Dissipation Concept with Stagni
and Nakamura kinetic reaction mechanisms.
The numerical results were evaluated in terms of flame
shape, flame stability and emissions, with a focus on theNO, N2O and NO2 shares in the flue gases and the unburned NH3 prediction capabilities of the model.
Qualitative and quantitative agreement was achieved
within the equivalence ratio (φ) range of 0.8-1.2, while therelative error of the NO predictions did not exceed 3.5%
with respect to the uncertainty of the experimental results.
Gradients of NH3 and NO shares in the flue gases forthe modelled turbulent flames were found to be shifted
towards stoichiometric conditions compared to the same
mixture and mechanism for a burner-stabilised stagnation 1D flame outcome. A significant overprediction ofNO emission was expected for very lean mixtures φ = 0.6,
as deviations can be related to the simplification of finestructure reaction fractions commonly used in the EDC
model. Despite its limitations in the very lean conditions,the model correctly predicted a decrease in NO concentration in the flue gases, associated with a rapid increasein N2O emission.
Contact: joanna.jojka@put.poznan.pl

INSIGHT INTO NH3 FORMATIONCHARACTERISTICS AT RICH CONDITIONS
IN 70/30 VOL% NH3/H2 FLAMESAli Alnasif1, Joanna Jójka2, Syed Mashruk1, Agustin ValeraMedina1
Cardiff university, United Kingdom, 2Poznań University of Technology,
Poland1

Recent studies have highlighted that in fuel blends witha 70/30 vol% ratio of ammonia/hydrogen, the ratio of
final to initial mole fractions of NH3 is notably high. This50

19th International Conference on Numerical Combustion

MS12 Spread of ammonia combustion research - Role of numerical simulation -finding underscores the importance of a comprehensive
understanding of the product gases, especially the residual NH3, in NH3/H2 laminar flames. Such understanding
is critical for designing NH3-fueled combustors to comply
with stringent emission regulations. Understanding theunderlying chemistry in the oxidation of NH3/H2 mixtures
is a pivotal factor for the flexible utilization of these mixtures in various applications, including propulsion systems
and power generation. In this context, the current work
investigates 70 kinetic reaction mechanisms from theliterature in atmospheric conditions. This study aims toevaluate the effectiveness of these mechanisms in predicting the mole fraction of unburned NH3 in a volumetricfuel mixture of 70% NH3 and 30% H2. The findings revealed that the Lamoureux kinetic model yielded reliable
estimations of the unburned NH3 within the equivalence
ratio (φ) range of 1-1.2. However, its accuracy decreased byaround 1.4 of φ. Notable variations were observed in thereaction steps and rate parameters among these tested
mechanisms. Predominantly, NH3 was converted to NH2
radicals through reactions with OH across all temperatures, with a secondary role played by O radicals at low
to intermediate temperatures. At higher temperatures,
NH3 dehydrogenation also occurred via H radicals, asevidenced in the NH3+H ⇌ NH2+H2 reaction. Additionally,at the combustion exit, NH3 regeneration was primarily
driven by the NH3 ⇌ NH2+H reaction at a temperature of
504 K.
Contact: AlnasifAH@cardiff.ac.uk

Evaluation of a manifold model for leanammonia/hydrogen/nitrogen-air laminarpremixed flames
Sydney Lauren Rzepka, Katie VanderKam, Hernando
Maldonado Colman, Michael E Mueller
Princeton University, United States

Partially cracked ammonia is a promising hydrogen
carrying fuel with logistical advantages compared topure hydrogen. Under fuel-lean conditions, ammonia/
hydrogen/nitrogen-air premixed flames can be thermodiffusively unstable. These instabilities have implications forflame propagation speeds as well as the local formationof nitrogen oxides and nitrous oxide. In this work, detailed
two-dimensional simulations of laminar premixed flames
are conducted to understand the development of thermodiffusive instabilities in flames of ammonia/hydrogen/nitrogen mixtures and air. The degree of ammonia cracking is varied to understand the influence of fuel composition on the instability behavior and subsequent formationof nitrogen oxides and nitrous oxide. The databases fromthese simulations are then used to evaluate a premixed

manifold model. Manifold models significantly decrease
computational cost by mapping the high dimensional
thermochemical state to a lower dimensional manifold.
This work assesses how accurately a manifold model for
premixed combustion, including differential diffusion effects and flame curvature influences, captures differential
diffusion effects as well as the formation of nitrogen oxides and nitrous oxide.
Contact: sr5286@princeton.edu

Chemical effects of ammonia on sootsuppression in laminar diffusion flames

Junjun Guo1, Qi Wang2, Erica Quadarella2, S. Mani Sarathy2,
Hong G. Im1
King Abdullah University of Science and Technology, Saudi Arabia, 2King
Abdullah University of Science and Technology , Saudi Arabia

1

The co-firing of ammonia (NH3) with hydrocarbon fuels
is an effective strategy for reducing CO2 emissions andaddressing the inherent low reactivity of NH3. However,soot formation presents a potential challenge in thiscontext. In this study, numerical investigations of laminar
counterflow and coflow diffusion flames are conducted
to understand the chemical effect of NH3 on soot formation. To improve the prediction of reduced PAH with NH3
substitution, an additional reaction of C3H3 and HCN isincorporated into the gas-phase mechanism. Moreover,a recently proposed reactive soot inception model is employed and the soot surface growth model is improvedto account for the blocking of active sites on the sootsurface by NH3 decomposition products (such as NH2).
The results demonstrate that NH3 substitution leads to adecrease in H radical and an increase in H2. Such a chemical effect is integrated well into the reactive inception
model, leading to improved predictions of soot volume
fraction and mean particle diameter in NH3-blended ethylene flames. Moreover, the consideration of soot-NH2
reactions further reduces the HACA surface growth ratein NH3-blended flames, leading to an additional improvement in the predictions of the sensitivity of soot volume
fraction and mean particle diameter to NH3 substitution.
This study demonstrates the importance of C-N chemistryin both gas-phase and solid-gas reactions on PAHs andsoot formation. Future work is needed to develop morecomprehensive C-N chemical pathways for predictions of
co-firing of ammonia with hydrocarbon fuels.
Contact: junjun.guo@kaust.edu.sa51

MS12 Spread of ammonia combustion research - Role of numerical simulation -MS12-3 Spread of ammonia
combustion research - Role ofnumerical simulation - (3)Chair: Hisashi Nakamura
Co-Chair: Ekenechukwu Chijioke Okafor
Wednesday, May 8; 15:30 - 17:10; Room D

Ammonia/coal co-firing on a complex
CI-α burner with preheated combustion
air streams using multi-stream FPV-LES
approach
Sujeet Yadav, Hiroaki Watanabe
Kyushu University, JapanThe FPV-LES approach applied to multi stream complex burners with preheated secondary, tertiary, andstaged combustion air streams, closely resembling conditions observed in commercial-scale power plant burners
has limitation considering different temperatures of oxidizer streams. To address this limitation, a new approachis introduced that considers the oxidizer temperature as
an additional lookup parameter by using three different
non-adiabatic flamelet libraries corresponding to different oxidizer temperatures for primary, secondary, andtertiary/staged streams. The thermochemical space isparameterized using seven-dimensional non-adiabatic
flamelet library, incorporating three mixture fractions forammonia, coal volatiles, and char-off gases as well as
mixture fraction variance, reaction progress variable, total enthalpy, and oxidizer temperature. The accuracy of
proposed approach is tested by performing multi stream
FPV-LES modeling of ammonia/coal co-firing on a 760
kWth semi-industrial test furnace of Central Research Institute of Electric Power Industry (CRIEPI) equipped withadvanced low NOx CI-α burner with preheated secondary, tertiary, and staged combustion air streams. The 7D
NA-FPV-LES model accurately captured the flow field inprimary reaction zone, which previous model failed to do
due to differences in oxidizer stream temperatures. This
resulted into more accurate O2 mole fraction profile and,
consequently, a better NO emission profile.
Contact: imsujeet@tse.kyushu-u.ac.jp52



A kinetic mechanism for ammonia-dopedhydrocarbon combustion: emerging
nitrogen chemistry of C3 and larger
speciesQi Wang, Myriam Belmekki, Manuel Monge Palacios,
Tairan Wang, Mani Sarathy

KAUST, Saudi Arabia

Ammonia (NH3) is a hydrogen carrier that can facilitate
the sustainable energy transition by enabling co-firingwith hydrocarbon fuels. In this work, we developed a new
kinetic mechanism for ammonia-doped hydrocarbon combustion by employing a combination of ab initio and kinetic study. New reaction pathways of large hydrocarbons reacting with NH3 and NH2 radical were proposed, and theirrate constants were determined by high-level quantum
chemistry calculation and robust kinetic method. Aftermerging a C2H4 combustion mechanism with the nitrogenchemistry up to C2, these proposed pathways and recent
literature on small nitrogen-containing species (e.g., NH2,
NH3, and HCN) reacting with C3 and larger hydrocarbons(e.g., polycyclic aromatic hydrocarbons) were included.
This mechanism was validated against literature measurements on laminar burning velocity of C2H4/NH3 premixed
flames, ignition delay time of NH3/O2/Ar mixtures, andprofiles of temperature and mole fractions of some gasphase species in a set of pure, N2-doped, or NH3-doped
C2H4 counterflow diffusion flames. Simulations also showthat these additional pathways are important to reproduce
experimentally measured quantities, such as the PAH reduction in C2H4/NH3 diffusion flames. Compared to literature mechanisms, our new kinetic model brings the model
predictions closer to experimental measurements without
the need for empirical adjustments.
Contact: mani.sarathy@kaust.edu.sa

Investigation of temperature and species
distributions in ammonia diffusion flames
Xingchang Xu, Minhyeok Lee, Yuji Suzuki
The University of Tokyo, Japan

Information on radical distributions in ammonia (NH3)flames is limited but vital for the development of high-fidelity ammonia kinetic models. In this study, the temperature and NH/OH radical distributions in the counterflow
NH3 diffusion flames have been investigated both experimentally and numerically. The flame temperature wasvaried in the range of 2200 to 2750 K by controlling thedilution ratio and measured using the Rayleigh scattering thermometry. The distributions of NH and OH were
captured by planar laser-induced fluorescence (PLIF).

19th International Conference on Numerical Combustion

MS12 Spread of ammonia combustion research - Role of numerical simulation -Furthermore, two-dimensional numerical simulations considering the actual burner configuration were performed
to validate the performance of recently proposed ammonia kinetic models against the present experimental data,
and additional one-dimensional numerical simulations
were also conducted to obtain insights into the discrepancies among the selected ammonia models. The results
show that all tested models reasonably predict the flame
temperatures. Compared with the experimental data, themodels predict the distribution of OH well at temperatures
below 2300 K but tend to underpredict the width of OH
profiles as temperatures increase. On the other hand, themodels show larger discrepancies in predicting peak OH/
NH concentrations at lower temperatures, which could be
the focus of future refinement of ammonia kinetic models.
Contact: ysuzuki@mesl.t.u-tokyo.ac.jp

Numerical simulation of laminar flame
propagation of ammonia/air premixture
under microgravity conditions

Masaya Muto1, Xia Yu2, Nozomu Hashimoto2, Hisashi
Nakamura3, Ryoichi Kurose4

Meijo University, Japan, 2Hokkaido University, Japan, 3Tohoku University,
Japan, 4Kyoto University, Japan1

Effect of gravity on laminar flame propagation of ammonia/air premixture is investigated under a normal-gravity condition and a micro-gravity condition by using thenumerical simulation of a three-dimensional sphericalpropagating flame. In order to accurately capture theflame propagation, direct numerical simulation is applied
to the flow field with a minimum grid size of 0.5 mm. And
GRI-Mech 3.0 mechanism is adopted for detailed chemical
reactions of ammonia/air premixture. Numerical calculation using a cubic calculation domain captures sphericalflame propagation within approximately 50ms from thestart of ignition of the ammonia/air premixture. The propagation speed of spherical flame propagation by numerical simulation is measured using the same flame front
tracking method as in the experimental measurement andcompared with the experimental values.

Chemical kinetic studies of ammonia andtheir application in numerical combustion
simulations
Hisashi Nakamura, Kenta Tamaoki, Yuki Murakami,
Keisuke Kanayama, Kaito Hirose, Takumi Harada,
Masahiko Izumi, Takuya Tezuka
Tohoku University, Japan

Ammonia is now recognized as an important chemical
for storing and transporting renewable energy. In recent
years, ammonia combustion for energy utilization has attracted attention in order to compensate for fluctuations
in electricity produced from renewable energy sources
and to achieve the decarbonization of large-scale transportation and high-temperature heating processes thatare difficult to electrify. This presentation introduces background, recent studies of ammonia chemical kinetics, andtheir application to numerical combustion simulations in
our group. To improve prediction performance of detailed
ammonia reaction models, species measurements in ammonia oxidation at intermediate temperatures have been
conducted using a micro flow reactor with a controlledtemperature profile (MFR) and gas analyzers such as a gas
chromatograph and mass spectrometer. Measured resultsin MFR as well as literature data such as ignition delay
times, laminar flame speeds, and speciation data in othersystems have been used for model validation. In addition
to the detailed models, small ammonia reaction models
are necessary for large-scale numerical combustion simulations such as boilers and furnaces. The presentation
also introduces generation method of small ammonia reaction models using genetic algorithms.
Contact: hisashi.nakamura@tohoku.ac.jp

Contact: mutom@meijo-u.ac.jp

53

MS13 Advances in dimensionality reduction andmanifold learning for the parametrization andmodeling of large combustion systems
Organizers: Temistocle Grenga1, Alessandro Parente2
University of Southampton, 2Université Libre de Bruxelles

1

MS13-1 Advances indimensionality reduction andmanifold learning for theparametrization and modeling oflarge combustion systems (1)Chair: Temistocle Grenga
Co-Chair: Alessandro Parente
Friday, May 10; 13:00 - 15:00; Room H

Dynamic Mode Decomposition analysis ofpremixed flames
Temistocle Grenga1, Antonio Attili2

University of Southampton , United Kingdom, The University of
Edinburgh, United Kingdom

1

2

Dynamic Mode Decomposition (DMD) has the capability to decompose flow field data into distinct coherent
modes, enabling the determination of their oscillation
frequencies and rates of growth or decay. This permits
the exploration of unsteady and dynamic phenomena, acapability beyond what conventional statistical analyses
can provide. This decomposition method is applicable foranalyzing data encompassing a wide spectrum of temporal and spatial scales because it identifies structures characterizing the physical phenomena independently of theirenergy content.
In this study, a specially designed DMD algorithm tailored for handling massive databases is utilized to examine
three-dimensional Direct Numerical Simulation data of spatially evolving turbulent planar premixed methane/air jet
flames across different Reynolds numbers.
This study aims to identify the key modes and frequencies crucial for the evolution of the flow field, particularly
concerning physical phenomena such as heat release andturbulence and their interaction.
The results are compared to previous analyses ofhydrogen/air jet flames in order to assess the role of differential diffusion in both fuel/air mixtures considered, as

54

well as their impact with respect to the turbulence intensity.
Contact: t.grenga@soton.ac.uk

Vector Quantization Partial Least Square(VQPLS) for enhanced semi-supervised
clustering for combustion manifold regression
Matteo Savarese1, Rafi Malik2, Himanshu Dave1,
Alessandro Parente1

Universite Libre de Bruxelles, Belgium, 2King Abdullah University of
Science and Technology, Saudi Arabia

1

PCA-based combustion simulations are increasingly
being used through the development of PC-transport
approaches. In such models, the tabulation of the source
term of new variables (PC scores) is a fundamental stepand is often approximated by complex nonlinear functions, such as Artificial Neural Networks (ANN) or Gaussian Process Regression (GPR). However, the training ofthese models can be computationally expensive, and theirfunctional forms may introduce non-negligible overhead
costs during simulations.
To address this challenge, the presented clustering
algorithm aims to identify data clusters where the relationship between PCA scores and the source term can beeffectively approximated by a linear model. The algorithm
relies on Partial Least Squares (PLS), a dimensionality reduction technique that considers the relationship between
the independent and dependent variables. This is particularly attractive to partition thermo-chemical state-space
effectively according to their relationship with the source
term. Therefore, in such a routine, the data are clustered
to minimize local linear regression errors. A user-defined
threshold on the desired error is then fixed, and clusters
with linear regression error above such threshold are joined
and modelled with nonlinear tools. This work will be beneficial in reducing training time of complex nonlinear tools,
as well as simplifying their functional form.
Contact: matteo.savarese@ulb.be

19th International Conference on Numerical Combustion

MS13 Advances in dimensionality reduction and manifold learning for the parametrization and modeling of large combustion systems

Application of In-Situ Adaptive Manifolds(ISAM) for the study of highly stratified
multi-regime flames
Anurag Surapaneni

Barcelona Supercomputing Center, Spain

The triple flame represents a canonical combustion
problem and serves as a benchmark test case for studying
multi-regime combustion models. In this current investigation, triple flames at different mixing lengths are examined using finite rate chemistry, tabulated manifolds basedon premixed flamelets, and a multi-modal combustion
model. The finite rate chemistry method is employed as areference to assess both the tabulated premixed flamelet
manifold and the multi-modal combustion models. The
study’s objective is to quantify deviations and identify limitations in the application of manifold-based methods in
multi-regime problems. Manifolds with varying resolutions
are utilised in both tabulated methods to assess the impact of manifold resolution on the solutions. Key aspectsof the problem, such as flame shape, flame surface area,and propagation speed, are compared across the different
methods. The study then proceeds to a scatter plot analysis of the thermochemical states obtained from thesemethods. It concludes by delineating the limitations within
which manifold methods can be effectively applied. Finally, the scope for future work is outlined.
Contact: anurag.surapaneni@bsc.es

On-the-fly reduced-order modeling oflarge combustion systems leveraging
time-dependent bases with CUR
decomposition
Ki Sung Jung1, Cristian Lacey1, Hessam Babaee2,
Jacqueline Chen1

Sandia National Laboratories, United States, 2University of Pittsburgh,
United States

1

While data-driven reduced-order modeling (ROMs)
have been successfully demonstrated in turbulent combustion simulations, their performance often relies on theselection and availability of appropriate datasets for offline
training. Recently, ROM leveraging time-dependent baseswith CUR decomposition, called TDB-CUR, was introduced
to approximate the solution of nonlinear matrix partial
differential equations by adapting the reduced-ordermodel on-the-fly without relying on a priori knowledge,
demonstrating the accuracy, robustness, and efficiencyof the model for a range of non-linear problems. In thispresentation, the applicability of the TDB-CUR is assessed
for chemically reactive flow simulations. A clustered dy-namic adaptive chemistry and rank-adaptive scheme arecoupled with TDB-CUR to enhance the computational efficiency of the ROM. It has been successfully demonstrated that TDB-CUR has an excellent agreement with direct
numerical simulation (DNS) results for methane-air flamesfor various canonical configurations. The performance of
the TDB-CUR approach is further evaluated using DNS
of compression ignition of large hydrocarbon fuels in thenegative temperature coefficient regime. The results showthat TDB-CUR can accurately replicate multi-stage ignition of a primary reference fuel/air mixture under engine
relevant conditions.
Contact: kjung@sandia.gov

Understanding the role of latent variables
in accelerated integration of stiff
chemical systems using autoencoders
Vijayamanikandan Vijayarangan, Harshavardhana A
Uranakara, Francisco E Hernández Pérez, Hong G Im
King Abdullah University of Science and Technology, Saudi Arabia

Efficient computation of finite-rate chemical kinetics remains a critical challenge in modern reacting flow
simulations due to inherent system stiffness. Building
upon our previous research, this study introduces adynamic-informed data-driven methodology aimed at
mitigating stiffness in chemical dynamics. By leveraging
a combined autoencoder and neural ordinary differential
equation approach, this method effectively eliminates
stiffness, thereby relaxing the time step requirements. The
autoencoder facilitates the computation of an optimized
low-dimensional latent space, yet its formulation remains
to be explored. Due to this, the combined neural system istreated as a black box. Recognizing the latent space as a
curved manifold with curvilinear coordinates, simple tools
from Riemann geometry are employed for the analysis.
In this work, information geometry is utilized to unveil thegeometric structure of the latent variables corresponding
to the physical state variables within the statistical model.
This exploration delves into revealing insights about theshape and geometry of the manifold. Additionally, thenecessary degrees of freedom essential for describing
the chemical dynamics accurately are determined. The
findings contribute to a deeper understanding of the underlying structure, aiding in more efficient computationalmodelling of reacting flow systems.
Contact: vijayamanikandan.vijayarangan@kaust.edu.sa55

MS13 Advances in dimensionality reduction and manifold learning for the parametrization and modeling of large combustion systems

Effect of Parametric Uncertainty
in Numerical Simulations Using
Dimensionality Reduction and Non-linear
Regression: Application to a HydrogenFueled Flameless Combustion Furnace

MS13-2 Advances indimensionality reduction andmanifold learning for theparametrization and modeling oflarge combustion systems (2)Univeristé Libre de Bruxelles, Belgium

Chair: Temistocle Grenga
Co-Chair: Alessandro Parente
Friday, May 10; 15:20 - 17:00; Room H

Ruggero AmaduzziThis work explores cost-effective uncertainty quantification (UQ) methods, crucial when dealing with high-dimensional uncertain parameter spaces. Employing proper
orthogonal decomposition and gaussian process regression (POD/GPR) technique, we constructed a surrogate
model for a 2-dimensional RANS response involving nine
uncertain parameters encompassing reaction rates, turbulence, combustion models, and inlet mass flow variations.
The surrogate model provided insights into the variance
contributions of these parameters.
Notably, within the furnace's flame region, the turbulence parameter $C_{2\varepsilon}$ and the PaSR combustion model constant $C_{mix}$ exhibited significant
influence on response variability. Conversely, farther fromthe flame, uncertainty in the inlet air mass flow $u_{air}$gained prominence due to its substantial impact on the
combustion chamber's recirculation pattern driven by the
air inlet jet.
More in general, the POD/GPR approach's efficacy lies
in navigating complex spaces with minimal simulations
compared to traditional UQ methods. This enables aninitial assessment of numerous uncertain parameters in
simpler models like 2D RANS. Then, the more critical parameters can be scrutinized using advanced models like3D RANS or LES.
Contact: ruggero.amaduzzi@ulb.be

Generalized progress variable and crossdissipation rate in turbulent lifted flames
using a multi-modal manifold-based
combustion model
Israel Joseph Bonilla1, Cristian E. Lacey2, Michael E.
Mueller1

Princeton University, United States, 2Sandia National Laboratories, UnitedStates1

Multi-modal manifold models in mixture fraction andgeneralized progress variable have been previously implemented in Large Eddy Simulation (LES), demonstratingthat manifold-based models can be generalized to nolonger require a priori assumptions about the underlying
combustion process. In this work, the influence of the definition of the generalized progress variable and its influence on the cross-dissipation rate of the mixture fraction
and the generalized progress variable is investigated with
LES of a multi-modal turbulent lifted hydrogen jet flame ina vitiated coflow. The multi-modal manifold-based model is implemented within the In-Situ Adaptive Manifolds(ISAM) computational framework, and two definitionsof the generalized progress variable are considered: astandard linear generalized progress variable that is anormalized product mass fraction and a nonlinear generalized progress variable whose gradients vanish in the asymptotic limit of nonpremixed combustion. This aspect of
the generalized progress variable definitions significantly
alters the relative magnitudes of the mixture fraction andgeneralized progress variable dissipation rates and fundamentally changes the behavior of the cross-dissipation
rate.
Contact: israel.bonilla@princeton.edu

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19th International Conference on Numerical Combustion

MS13 Advances in dimensionality reduction and manifold learning for the parametrization and modeling of large combustion systems

Dynamic Cell Clustering with Principal
Component Analysis for massively parallel
multi-regime reactive flows
Antoine Stock1, Vincent Moureau1, Julien Leparoux2,
Renaud Mercier2
1

COmplexe de Recherche Interprofessionnel en Aérothermochimie, France,
Safran Tech, France2

Dynamic Cell Clustering (DCC), also referred as Cell
Agglomeration, is an optimisation technique used to reduce the cost of finite-rate chemistry in reactive flows. It
consists of three steps: i) grouping of elements with similar composition into clusters, ii) computation of a single
element per cluster and iii) mapping of the computed elements to the remaining elements of the cluster throughinterpolation and extrapolation. Principal Component
Analysis (PCA) is used during the initial clustering step toidentify dominant features within the composition spaceand reduce its dimensionality. This approach is demonstrated in the CORIA Rouen Spray Burner (CRSB) using either global parallel PCA and local PCA within each core. In
this burner, multi-regime combustion occurs through fueldroplets that evaporate before and within the flame front
leading to partially premixed and diffusion flames, making it a challenging case for PCA. The simulations run on
10,000 cores with 300 million tetrahedral cells. With the
DCC-PCA methodology, the cost of chemistry is reduced
by 50% while introducing a relative error on source termsof less than 1%.
Contact: antoine.stock@coria.fr

JuLES: A Data-Driven Framework for
Subfilter Model Development of Reactive
Flows on Supercomputers at Scale
Mathis Bode

Forschungszentrum Jülich GmbH, Germany

JuLES (JUelich Large-Eddy Simulation) is a disruptive
Software-as-a-Service (SaaS) platform for developing reduced models of reactive flows in the shortest possible
time and with unprecedented predictive accuracy. It is
integrated into the supercomputing environment at the
Jülich Supercomputing Centre, including the JupyterLabcloud, HPC resources, and quantum computing, to provide
maximum opportunities with minimum barriers to entry.
Technically, JuLES uses Physics-Informed Enhanced Super-Resolution Generative Adversarial Networks (PIESRGAN) for Large-Eddy Simulation (LES). PIESRGAN for LES
enables the data-driven development of reduced models
for reactive flows that have been shown to be significantly
superior to existing models in terms of prediction accura-cy, robustness, and universality, while reducing simulation
costs by two orders of magnitude and I/O by as muchas three orders of magnitude. Consequently, industrial
development processes are potentially accelerated by
years. The combination of classical, well-established fluid
mechanics techniques and cutting-edge AI technology,
its ability to fully scale on today's supercomputers, and its
cloud-based n:m on-the-fly training make it a very powerful tool for industrial transformation and even ready forthe upcoming exascale machine JUPITER. Multiple combustion applications are discussed in this work.
Contact: m.bode@fz-juelich.de

A Co-kurtosis PCA based Dimensionality
Reduction for Chemical Kinetics:
A-Posteriori Analysis
Shiva Sai Tadikonda1, Hemanth Kolla2, Aditya Konduri1
Indian Institute of Science, India, 2Sandia National Laboratories, UnitedStates1

A low-dimensional representation of thermo-chemical
scalars based on cokutorsis principal component analysis(CoK-PCA) has been shown to effectively capture stiff
chemical dynamics in reacting flows relative to the widelyused principal component analysis (PCA). The effectiveness of the reduced manifold was evaluated in a priori
analyses using both linear and nonlinear reconstructionsof thermo-chemical scalars from aggressively truncatedprincipal components. In this study, we demonstrate theefficacy of a CoK-PCA-based reduced manifold using a
posteriori analysis. Simulations of spontaneous ignition
in a homogeneous reactor that pose a challenge in accurately capturing the ignition delay time as well as the profiles of the scalar within the reaction zone are considered.
A manifold assessment in the a priori setting showed thatPCs from CoK-PCA are less stiff than those from PCA. The
principal components were evolved from the initial conditions using two ODE solvers. First, a standard solver thatuses an aritifical neural network to estimate the source
terms. Second, a neural ODE solver that incorporates thetime integration of PCs in training ANNs, which predict
their source terms. The time-evolved profiles of the PCs
and ANN-reconstructed thermo-chemical scalars demonstrate the robustness of the CoK-PCA based low-dimensional manifold in accurately capturing the ignition
process. Furthermore, we observed that the neural ODE
solver provides more accurate results than the standard
ODE solver. The results from this study demonstrate thepotential of CoK-PCA-based manifolds to be implemented
in massively parallel reacting flow solvers.
Contact: konduriadi@iisc.ac.in57

MS13 Advances in dimensionality reduction and manifold learning for the parametrization and modeling of large combustion systems

Effects of combustor wall temperatureon the low-temperature chemistry inturbulent premixed DME/air swirl flames

Wenjun Lin1, Zhenhua An2, Weijie Zhang1, Jinhua Wang1,
Zuohua Huang1, Huangwei Zhang3
Xi'an jiaotong University, China, 2Kyoto University, Japan, 3National
University of Singapore, Singapore

1

The environment of the outer recirculation zone (ORZ)
in swirl flame is favorable for low-temperature ignition
under fuel lean conditions, but the factors affecting theORZ combustion modes remain unclear. This study investigates the effects of wall thermal boundary conditions
on combustion modes using the LES-FGM method. The
results of tabulated chemistry were firstly validated by theexperiment data and the detailed chemistry. It is foundthat the flame topology is highly sensitive to the wall thermal boundary condition. Based on the correlation between
temperature and species in the time-averaged results, it
is inferred that there is a link between wall temperatureand combustion modes. Through temporal analysis of
species and heat release rate in the ORZ, the stable Mode
II and Mode IV as well as the unstable Mode III are identified. Subsequent chemical reaction pathway analysis on
specific probes reveals that different combustion modes
undergo distinct chemical reaction pathways. Finally, thedefinition of combustion modes used in experiments isrefined by utilizing the chemical reaction fluxes in the simulations. This refined definition is applied to classify combustion modes across the entire computational domain.
The results confirm the consistency between the combustion modes determined in experiments based on OH andCH2O and those determined in simulations using chemical reaction fluxes. Based on these findings, the adaptability of the FGM-LES method in predicting lean premixed
swirling flame can be ascertained, and the mechanism ofwall thermal boundary conditions on combustion modes
in premixed swirling flame is recognized.
Contact: linwenjun1113@outlook.com

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19th International Conference on Numerical Combustion

MS14 Numerical modeling and simulation ofreactive dense particle-laden flows
Organizer : Takuya Tsuji
Osaka University

MS14-1 Numerical modeling andsimulation of reactive dense
particle-laden flows (1)Multi-scale simulation of solid fuelconversion in dense particulate reactive
systems

Chair: Takuya Tsuji
Wednesday, May 8; 10:40 - 12:20; Room G

Zhejiang University, China

A new DEM-CFD solver for reactive dense
gas-solid flows based on a characteristic
splittingTakuya Tsuji1, Yuki Yakata1, Dorian Faroux2, Kimiaki
Washino1, Masaya Muto3, Hiroaki Watanabe4, Ryoichi
Kurose51

Osaka University, Japan, 2DENSE Ltd., Japan, 3Meijo University, Japan,
Kyushu University, Japan, 5Kyoto University, Japan

4

Reactive dense gas-solid flows play important roles
in carbon neutrality. Interplays between flow and dense
particle dynamics, heat and mass transfers, and chemical reactions over a wide range of spatiotemporal scales
make its behavior complex. Due to its inherent opacity,
experimental diagnosis is difficult, and the realization ofhigh-fidelity numerical simulation is important but stillchallenging. In this study, a new unresolved DEM-CFD
solver based on the fractional-step method is proposed.
A characteristic splitting enables the separation of theacoustics from the advection, resulting in the efficient calculation of gas motions. All governing equations including
the Helmholtz equation for the pressure variations arevolume-averaged. Details of the algorithm and the resultsof several validation cases are presented.
Contact: tak@mech.eng.osaka-u.ac.jp

Shuai Wang, Jiahui Yu, Junjie Lin, Kun Luo, Jianren Fan

Solid fuel conversion is quite common in many engineering fields, including biomass gasification, coal combustion, solar panel waste pyrolysis, chemical looping
combustion, blast furnace ironmaking, etc [1]. These kindsof processes are extremely complex involving both physical changes and chemical changes. Understanding thefundamentals governing the gas-solid flow and coupledheat and mass transfer is of paramount importance tothe design, control, and optimization of dense particulate
reactive systems. In this talk, we will present the recent
work related to the development of multi-scale numericalmethods, including computational fluid dynamics-discreteelement method (CFD-DEM), coarse-grained method(CGM), and multiphase particle-in-cell (MP-PIC) with complex thermochemical sub-models [2-4]. The integrated
models were validated using experimental data, demonstrating their reasonable accuracy.
The CFD-DEM model enables the high-fidelity simulation of lab-scale apparatuses and provides detailed
information on particle residence time, heat transfer
contribution, carbon conversion ratio, and other crucial
parameters. In contrast, the CGM and MP-PIC models
facilitate the high-efficiency simulation of pilot-scale andindustrial-scale apparatuses, offering in-depth insights
into vital in-furnace phenomena such as cluster evolution,size-/density-induced segregation, gas pollutant formation, and so on. The multi-scale simulation approach is
expected to provide valuable information for optimizing
the process of solid fuel conversion in reaction-intensive
apparatuses.
Contact: wshuai2014@zju.edu.cn

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MS14 Numerical modeling and simulation of reactive dense particle-laden flows

Particle-resolved lattice Boltzmann
simulations for sedimentation of reactive
particles involving coke deposition
Yiqi Song, Xue Li, Mao Ye

Chinese Academy of Sciences, China

Catalysts have been widely applied in various chemical processes. When hydrocarbons are employed as
feedstock, coke deposition on the catalyst can result in
the coverage of active sites and blockage of nanopores,
leading to the decrease of reaction rates and even deactivation of the catalyst1,2. In this work, a particle-resolved
lattice Boltzmann method (LBM) with a hybrid multiple-relaxation-time scheme was used to investigate theeffect of coke formation on particle-fluid interaction. The
particle-fluid interface was treated using the Immersed
Boundary method (IBM). The sedimentation of a single
particle and a pair of particles with varying reaction rates
constant have been simulated, in which the change ofcatalyst physical property and reaction activity due tocoke deposition were considered. The results show thatthe increase of coke deposition on the catalyst can accelerate the sedimentation rate of a single catalyst particle
owing to the gradual increase of weight. For the case of apair of particles, the drafting, kissing, and tumbling (DKT)
phenomenon of coked particles is different from that of
non-reactive particles. Suppose that these two particles
have different deactivation rates because of uneven concentration distribution, and the second DKT phenomenon
occurred earlier with a larger reaction rate.
Contact: songyiqi@dicp.ac.cn

Coarse grained CFD-DEM simulations ofiron-iron oxide conversion in fluidized
beds
Yali Tang, Niels Gerbrand Deen

Eindhoven University of Technology, Netherlands

Iron powder has enormous potential to boost the energy transition, as an energy carrier in a carbon-neutral
circular energy economy. This is realized by the cyclic
storage and release of renewable energy via processes ofiron reduction and oxidation.
In this work, a numerical model, coupled between CFD
and coarse-grained DEM, is developed for simulatingchemical conversion processes of micron-sized iron/ironoxide powder in fluidized beds (FB) at intermediate temperatures. An unreacted shrink core model is incorporated
for iron reduction/oxidation, utilizing reaction kinetics fromthermogravimetric analysis experiments. Furthermore, thetemperature-dependent solid bridge force is considered60as the interparticle cohesive force. With careful validation,
the developed model is demonstrated to predict quantitatively the effects of different operating parameters (suchas temperature, gas velocity, reactive gas concentration)on the oxidation/reduction behaviour of iron/iron oxide
powder. The temperature is found crucial to both oxidation and reduction processes. Increasing temperature, on
one hand, speeds up the chemical reaction. On the other
hand, higher temperature triggers the sintering of solid
particles, which may cause serious agglomeration or evendefluidization. An optimal operating temperature window
has been determined from systematic simulations of bubbling FB. Finally, simulations considering different reactor
types (bubbling FB, turbulent FB, spouted FB, vibrating FB)
provide design guidance to the engineering processes of
the iron power technology.
Contact: y.tang2@tue.nl

Numerical modelling the reaction
propagation in Al based thermites

Emilian Tichtchenko, Alain Esteve, Benoit Bedat, Olivier
Simonin, Carole Rossi
CNRS, France

Nanothermites are promising energetic materials as
their high-temperature reaction driven by the oxidationof a metallic fuel associated with the reduction of anoxidizer, can exhibit extremely fast burning rates, exceeding hundreds of m/s. By modifying reactant size,
stoichiometry, and compaction conditions, it is possible
to tailor combustion properties, including temperatureand intermediate reactions. Unfortunately, the complex
multiphasic physics governing thermite combustion,
where combustion gases interact with burning particles,
is still poorly understood and documented, while being
the key step to depict the dynamics of the flame front.
We developed a first one-dimensional (1D) model that
describes the dynamics of the reaction front propagationin Al/CuO powdered thermite considering the reacting
flow combined with heat transfer, chemistry and fluid
flow. CuO was chosen as it is the widest used metallic
oxidizer, that decomposes below the flame temperature,
leading a a gas phase reaction. Separate mass, momentum and energy transport equations for the three phases, namely Al, CuO particles and gas mixture, are written
in the frame of N-Euler approach for multiphase reactive
flows. These equations are coupled by modeled interphase transfer terms. After the description of the theoretical formulation and numerical method, two numericalexperiments, i.e. mixture of Al/CuO powder burning into
semi-open and closed tubes, will be discussed with thegoal to understand the multiphase flow physics in the

19th International Conference on Numerical Combustion

MS14 Numerical modeling and simulation of reactive dense particle-laden flows

thermite flame front.
Contact: rossi@laas.fr

MS14-2 Numerical modelingand simulation of reactive dense
particle-laden flows (2)Chair: Yali Tang
Wednesday, May 8; 13:30 - 15:10; Room G

DEM-CFD modeling of limestones withactual diameter distribution flowing down
in a combustion field in a rotary kiln
Susumu Tsuchiya1, Masaya Muto2, Fumiteru Akamatsu3,
Ryoichi Kurose4, Yuta Umeno5, Takayuki Nishiie5

Yabashi Industries CO.,LTD., Japan, 2Department of Environmental
Technology,Meijo University , Japan, 3Department of MechanicalEngineering, Osaka University , Japan, 4Department of MechanicalEngineering and Science, Kyoto University , Japan, 5Numerical Flow
Designing CO.,LTD, Japan1

In this study, is to clarify the gas temperature distribution in the kiln and the behavior of limestones flowing
down in the kiln by performing a numerical simulation of
the combustion field in the actual rotary kiln.
RANS simulation coupled with Discrete Element Method (DEM) is applied to a combustion reaction flow fieldwith limestone motion in a real rotary kiln. The governing
equations for the gas phase are the conservation equations of mass, momentum, energy, mass of each chemical
species. Standard k-epsilon model is used as a turbulent
model. For the flowing limestone, the Discrete Element
Method (DEM) is applied to consider the contact force
between the limestone and the inner wall of the kiln, andbetween the limestone particles. A limestone particle size
distribution based on measured values in the actual kiln isgiven as the limestone injection condition in the simulation.
Result shows that the present analysis satisfactorily
predicts the gas chemical composition at the outlet ofkiln, and that the mutual interference and decarboxylation
process of limestone are well reproduced.
Contact: susumu@mail.yabashi.co.jp

Consistent treatment of added mass, andmass and heat exchange in dense reactive
gas-particle flow simulations
Rodney O Fox1, Jacob Posey2, Ryan W Houim2
1

Iowa State University, United States, 2University of Florida, United States

In recent work, we have developed a multifluid modelfor high-speed, polydisperse, gas-particle flow with solidand gas-phase reactions. This model is well-posed due tothe inclusion of added mass and the particle-fluid-particle
stresses. The added mass is modeled as fluid surrounding
a solid particle and traveling with the same velocity as
the particle. In the context of non-reacting flow without
mass transfer, the volume of fluid representing the added
mass changes locally in a dense flow to adjust to the local volume fraction of the disperse phase. Moreover, theadded-mass fluid and the solid particle are assumed tohave the same temperature, which can be different thanthe continuous gas phase moving with its own velocity.
In this work, we extend the model in a consistent mannerto allow for the added-mass fluid and the solid to havedifferent thermodynamic properties, which are also different than the continuous gas phase. For reactive flows,
the chemical mass fractions in the solid, added-mass fluidand continuous fluid will generally be different and must
be modeled consistently to obtain the correct overall
mass/heat-transfer rates. Here, dense reactive gas-solid
flow simulations for high-speed flows are used to verify
the proposed model under different flow regimes with andwithout chemical reactions.
Contact: rofox@iastate.edu

Multi-scale insights of chemical looping
combustion in a three-dimensional
bubbling fluidized bed
Junjie Lin, Kun Luo, Jianren Fan
Zhejiang University, China

Chemical looping combustion (CLC) has emerged as
an effective carbon capture and storage (CCS) technique.
Yet, the intricate interaction of flow, temperature, andspecies fields presents challenges in comprehending theunderlying mechanism from multi-scale aspects. In thiswork, a computational fluid dynamics-discrete element
method (CFD-DEM) reactive model is developed, featuringa coarse-grained method to provide efficient calculation
and a modified drag model to consider the polydispersity
effect. After comprehensive validations, the integrated
model is applied to simulate the CH4-fueled CLC process
in a fuel reactor (FR), with a discussion of the effects ofparticle size distribution and reactor inner diameter on

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MS14 Numerical modeling and simulation of reactive dense particle-laden flows

the system performance. The results demonstrate thatthe particle-scale polydispersity, bubble-scale dynamics,
and reactor-scale structure can significantly influence theinteractions between gaseous fuel and oxygen carriers in
the CLC system. These factors play a crucial role in determining the thermochemical characteristics of the system.
Particularly, bubbles in the FR with a smaller diameter
display a characteristic of “fewer but larger”, whereas bubbles in the newly devised FR with a larger diameter exhibita feature of “more but smaller”. Consequently, enhanced
uniformity in gas-solid physicochemical properties, heightened CO2 concentration, and improved combustion efficiency can be achieved in our newly designed CLC reactor.
Overall, this study imparts valuable multi-scale insights
into the physical-thermal-chemical characteristics of the
CLC process.
Contact: linjunjie@zju.edu.cn

Full-loop reactive simulation of catalytic
cracking CFB system with mechanicalvalvesBona Lu, Yuting Wu, Wei Wang

Institute of Process Engineering, Chinese Academy of Sciences, China

Circulating fluidized bed (CFB) systems are the coreunits of many chemical and energy processes. In thisstudy, a full-loop simulation of an industrial reaction-regeneration CFB system is realized by modeling mechanical valves under the framework of two-fluid model. The
EMMS-matrix model is used for regions operated in fast
fluidization or pneumatic transport, and the EMMS-bubbling model for the bubbling or turbulent fluidization. The
twelve-lump kinetic model is used to describe endothermic catalytic cracking reaction, and the coke combustion
model is adopted for exothermic coke burning reaction.
The solid phase is treated as a mixture of solid catalysts
and coke, and the gas phase is treated a mixture of twelve
species (eleven is gas products and the other is steam).
During the circulation of solid phase throughout the fullloop system, coke deposition on solid catalysts varies andsimultaneously accompanies with heat transfer between
the reactor and regenerator. The results show that compared to the full-loop hydrodynamic simulation, the reactive simulation needs much more time to achieve the loop
balance, as spent solid catalysts in the regeneration parthas experienced multiple circulations from the top region
to the bottom region through external circulation pipe tomaintain enough long residence time for complete cokeburning. In addition, it is found that there exists one-order-magnitude difference in solid concentration fluctuation frequency for the full-loop simulation and the single
riser simulation. Such difference should be taken into ac-

62

count in optimize and scale-up the mesoscale structures.
Contact: bnlu@ipe.ac.cn

Modelling of gas-solid reacting flows andindustry applications
Yansong Shen

University of New South Wales, Australia

Process design and control play a significant role inmodern industries. Most processes and reactors are very
complex, as they usually involve not only multiphase flows
but also heat and mass transfers related to chemical reactions and their interactions – the so-called reacting flowwhere powder plays an important role in operation stability and efficiency. The operation must be optimized in order to be competitive and sustainable, particularly undermore and more demanding economic and environmental
conditions. This will need continuous innovative researchand development. Computer simulation and modelling,supported by online data and experiments, have emerged
as an indispensable adjunct to the traditional modes of investigation for the design, control and optimization of processes, reactors, and devices. Several case studies including hydrogen generation, storage and use in the net zerosteel industry are presented in this talk to demonstratethat the modelling works are indeed helpful to understandfundamentals and optimize & develop new, cleaner andmore efficient technologies towards net zero industry innovations with measurable outcomes and profits.
Contact: ys.shen@unsw.edu.au

MS14-3 Numerical modelingand simulation of reactive dense
particle-laden flows (3)Chair: Yansong Shen
Wednesday, May 8; 15:30 - 16:50; Room G

A high-order quadrature method of
moments implementation for dense
polydisperse granular reactive flows
Jacob Posey1, Rodney Fox2, Ryan Houim1
1

University of Florida, United States, 2University of Iowa, United States

Dense, high-speed, and reactive multiphase flow models are common in nature are routinely used in engineering applications including pyroclastic flows, heterogeneous explosive charges, and dust explosions. We recently
developed a theoretical model that accounts for dense

19th International Conference on Numerical Combustion

MS14 Numerical modeling and simulation of reactive dense particle-laden flows

polydisperse granular mixtures interacting with compressible reactive gases using quadrature method of moments(QMOM). Our original implementation used first-ordernumerical methods for 1D applications. Here, we present
an extension of the method to multiple dimensions andhigh-order methods. The numerical fluxes for the gas
and particle system are computed by approximating thefull Riemann problem as a series of individual Riemannproblems for the gas and each particle moment. The gasphase fluxes are computed using a traditional approachbased on the HLLC Riemann solver and fifth-order MUSCL. The Wheeler algorithm is used to convert particle moment equations into size-conditioned mass, momentum,
and energy equations. The granular fluxes for each ofthese size-conditioned moments are computed independently and using the AUSM+-up flux scheme. The results of these individual gas and granular Riemann problems are assembled to form the transport operators of
the governing equations. Effects of drag, convective heattransfer, particle collisions, etc. are integrated using an
operator splitting approach with analytical approximations
when possible. Results of the high-order method show
substantial improvement over the first-order method.
Simulations of shock waves interacting with bi-disperse
aluminum particle curtains and the explosive dispersal ofaluminum particles will be presented.
Contact: rhouim@ufl.edu

GPU-accelerated CFD-DEM modeling ofdense gas-solid reacting flow
Jiahui Yu, Shuai Wang, Kun Luo, Jianren Fan
Zhejiang university, China

Dense gas-solid reacting flow is quite common in
many engineering fields such as energy conversion, petro-chemical processing, mineral processing, chemicalengineering, and pharmaceutical manufacturing. These
kinds of processes are extremely complex involving both
physical changes and chemical changes. Understanding
the fundamentals governing the gas-solid flow and coupled heat and mass transfer is of paramount importanceto the design, control, and optimization of dense gas-solid
reacting systems of various types. Computational fluid dynamics – discrete element method (CFD-DEM) has beenrecognized as a useful tool to achieve this goal, yet thismethod suffers from expensive computational resources.
Accordingly, this work develops a graphics processing unit
(GPU)-accelerated CFD-DEM reactive model, featuring
heat transfer, heterogeneous reactions, and homogenous
reactions. The accuracy of the GPU-accelerated heat andmass transfer sub-models are detailly verified and the simulation results are in good agreement with analytic solu-

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tions. Additionally, this model can accurately predict thethermochemical behavior of the particle cooling process
in a bubbling fluidized bed and the coal-fueled chemicallooping gasification process, confirming its reliability insimulating dense gas-solid reacting systems. Furthermore,
the GPU-accelerated strategy is demonstrated to perform
great speed-up performance and stability. This work is expected to provide a reliable and high-performance parallel
calculation method for numerically studying the gas-solid
dense reacting flows.
Contact: yujiahui@zju.edu.cn

A hybrid inversion model using
measurement data for optimized CFD
simulations of fluidized beds
Xue Li, Mao Ye

Dalian Institute of Chemical Physics, Chinese Academy of Sciences, China

The hydrodynamic behavior in gas-solid fluidized beds
is complex and the mechanism is not yet complete. The
computational fluid dynamic (CFD)-based simulation models contain simplified theoretical models and empiricalformulas, which may result in differences between simulations and actual situations. Here, a cross-platform hybrid
model was constructed to optimize the selectable parameters of simulation models according to the measurements. The hybrid model utilized the open-source MFiX
software for CFD simulation and developed in-home codefor parameter optimization. And a python component was
built for data transfer and runtime control between simulation and parameter optimization. The proposed hybrid
model was validated by a CFD-DEM (discrete element
method) simulation of a pseudo two-dimensional fluidized
bed. Select the solid volume fraction at the cross-sectionof one static bed height as the monitoring variable (orreference) and the Kalman filtering method as the optimization algorithm. The proposed hybrid model can predict
the simulated solid volume fraction change curves withdozens of time steps of simulation results, compare thepredicted results with reference data, and iteratively optimize CFD parameters under an inverse strategy. The optimized CFD-DEM model can better match the referencedata.
Contact: lixue@dicp.ac.cn

63MS14 Numerical modeling and simulation of reactive dense particle-laden flows

Numerical study on unsteady combustionin Stoker furnace
Takashi Ikeda, Kenji Yamamoto, Toshihiko Setoguchi,
Junji Imada
Mitsubishi Heavy Industries, Ltd., Japan

Garbage is regarded as one of the primary carbon
neutral energy resource. Waste incinerator with stoker furnace generates power using garbage, and it has relatively
stable supply of electricity compared to other renewableenergy resource.
In stoker furnace, energy and chemical transportation
by solid phase and gas phase with chemical reaction significantly may affect the combustion phenomena. Therefore, it is necessary to construct the simulation code toconsider not only solid and gas phase behavior but alsointeraction of each other and chemical reaction.
In this study, Discrete Element Method (DEM) andComputational Fluid Dynamics (CFD) were strongly coupled for reconstructing phenomena in stoker furnace. In
addition, chemical reaction of solid and gas phase wasalso implemented in those simulation. Although simulation showed a similar flame location compared to actual
furnace under steady operation conditions, flame had
unsteady flickering. It is considered that flickering of flame
mainly caused by variation of amount of intermittent fuelsupply.
Contact: takashi.ikeda.m4@mhi.co.jp64

19th International Conference on Numerical Combustion

MS15 Combustion simulation acceleration using
GPU and manycore heterogenous computing
hardwares
Organizers: Zhi X. Chen1, Hong Im2, Venkat Raman3

Peking University, 2King Abdullah University of Science and Technology, 3University of Michigan

1

MS15 Combustion simulation
acceleration using GPU andmanycore heterogenous
computing hardwares
Chair: Zhi X. Chen
Co-Chair: Hong G Im
Wednesday, May 8; 13:30 - 15:10; Room J

GPU-accelerated CSP solver for highfidelity simulations of reactive flows

Alessandro Carinci1, Francisco E. Hernández-Pérez1,
Riccardo Malpica Galassi2, Mauro Valorani3, Hong G. Im4King Abdullah Univerisity of Science and Technology, Saudi Arabia,
Sapienza Univerity of Rome, Italy, 3Sapienza University of Rome, Italy,
4King Abdullah University of Science and Technology, Saudi Arabia
1

2

In this work, recent progress in the development of a
Computational Singular Perturbation (CSP) solver, accelerated with Graphics Processing Units (GPUs), is presented
in the context of multidimensional reacting flow simulations. An assessment of its impact on the performance ofthe KAUST Adaptive Reactive Flows Solver (KARFS) for
high-fidelity simulations is conducted. We implemented
a batched CSP solver, following the Kokkos programming model for performance portability. At each grid
point, applying the operator-splitting technique, the CSP
solver removes the stiffness on-the-fly and numericallyintegrates a non-stiff reduced order model (ROM) of thechemical kinetics operator. This permits to advance thethermo-chemical state with an explicit numerical scheme
making use of larger integration time steps. On the hardware side, the solver is accelerated with GPU cards, executing the algorithm independently at each grid point andexploiting all the parallelism layers offered by Kokkos.

nekCRF: An exascale-ready finite-ratechemistry solver designed for GPUaccelerated supercomputers

Mathis Bode1, Ananias Tomboulides2, Christos Frouzakis3
Forschungszentrum Jülich GmbH, Germany, 2Aristotele University
Thessaloniki, Greece, 3ETH Zuerich, Switzerland

1

Most of the performance of the latest generation of
HPC systems, and especially all exascale supercomputers,
is based on GPUs. Many codes were originally designed
to run on CPUs, and switching to GPUs is highly non-trivial. This is especially true for reactive flow solvers due tothe large number of scalar fields and the resulting stiff
systems. In the frame of the Center of Excellence in Combustion (CoEC), the development of nekCRF, a GPU-based
solver for extreme-scale computational fluid dynamics(CFD) for low Mach number compressible reactive flows
has been enabled. nekCRF is based on the well-established high-order spectral element code nekRS and solves
the low-Mach form of the Navier-Stokes equations together with the energy and species transport equations.
nekCRF was run on up to 3600 NVIDIA A100 GPUs of
JUWELS Booster, the fastest German supercomputer, andshowed excellent scaling. Single node performance wasdemonstrated to be very efficient due to code design andhigh-performance computing (HPC) optimizations. Several
test cases, ranging from canonical tests and flame kernels in confined geometries to complex applications withmoving meshes, confirmed the numerical and physical accuracy of nekCRF. Overall, nekCRF is fully exascale-readyand can be used to accurately simulate turbulent flamesin open or closed domains with unprecedented resolution.
Contact: m.bode@fz-juelich.deContact: alessandro.carinci@kaust.edu.sa

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65

MS15 Combustion simulation acceleration using GPU and manycore heterogenous computing hardwares

An integrated framework for accelerating
reactive flow simulation using GPU andmachine learning models

Runze Mao1, Yingrui Wang2, Min Zhang1, Han Li1, Zhi X.
Chen1

combustion simulation speed of OpenFoam by a factorof 10 to 100. Additionally, the program offers interfaces inboth C language and Python, making it effortlessly callable by other numerical simulation programs to incorporate combustion simulation capabilities.

1
Peking University, China, 2Shanghai SenseTime Intelligent Technology Co.,
LTD, China

Recent progress in artificial intelligence (AI) andhigh-performance computing (HPC) have brought potentially game-changing opportunities in accelerating reactive flow simulations. In this study, we introduce an opensource computational fluid dynamics (CFD) frameworkthat integrates the strengths of machine learning (ML)and graphics processing unit (GPU) to demonstrate their
combined capability. Within this framework, all computational operations are solely executed on GPU, including
ML-accelerated chemistry integration, fully-implicit solvingof PDEs, and computation of thermal and transport properties, thereby eliminating the CPU-GPU memory copy
overhead. Optimisations both within the kernel functions
and during the kernel launch process are conducted toenhance computational performance. Strategies such as
static data reorganisation and dynamic data allocation
are adopted to reduce the GPU memory footprint. The
computational performance is evaluated in two turbulent
flame benchmarks using quasi-DNS and LES modelling,respectively. Remarkably, while maintaining a similar levelof accuracy to the conventional CPU/CVODE-based solver, the GPU/ML-accelerated approach shows an overall
speedup of over two orders of magnitude for both cases.
This result highlights that high-fidelity turbulent combustion simulation with finite-rate chemistry that requires
normally hundreds of CPUs can now be performed on
portable devices such as laptops with a medium-end GPU.
Contact: maorz1998@stu.pku.edu.cn

A combustion simulation program library
accelerated by GPU
Guanlin Dang1, Yuqing Cai2, Zhi Chen1
1

Contact: gldang@foxmail.com

Deep learning-enabled exascale flame
simulation with detailed chemical kinetics
accuracy on New Sunway Supercomputer
Zhuoqiang Guo1, Zhi X. Chen2, Weile Jia1
1

Institute of Computing Technology, Chinese Academy of Sciences, China,
Peking University, China

2

Combustion simulation based on accurate chemical
reactions is the de facto standard in simulation of ignition,engine design, etc. OpenFOAM and DeepFlame combine
to implement Deep learning-enabled flame simulation
with detailed chemical kinetics accuracy. The new Sunway
supercomputer is an exascale heterogeneous many-coresupercomputer with more than 42 million heterogeneous
cores. In this work, we further enhanced the performanceof the OpenFOAM and DeepFlame code on the new Sunway supercomputer through optimization in three key areas: DNN inference, sparse solver, and startup process. In
the DNN inference process, we leveraged mixed precision
techniques to significantly enhance the speed of DNN inference. For the sparse solver, we tailored various sparse
matrix operators including SymSpMV, SpMV, SymGS, etc.
based on Sunway's architecture, which greatly accelerated
the construction and solution process of sparse matrices
in OpenFOAM. Addressing the challenge of prolonged
startup times in large-scale OpenFOAM simulations, we
introduced methods such as Multi-Procedure Fusion,
Foam File Indexing, and Two-Level Parallel IO. These
innovations resulted in a substantial acceleration of the
OpenFOAM startup process, enabling us to conduct exascale flame simulations on the new Sunway.
Contact: guozhuoqiang20z@ict.ac.cn

Peking University , China, 2Tianjin University, China

This article introduces a GPU-accelerated chemical
ordinary differential equations (ODE) solver library, which
encompasses four primary components: the calculationof thermodynamic properties, the solution of chemical
reaction rates, the calculation of Jacobian matrices forchemical reaction equations, and the solution of ODE for
chemical reactions. This program library can be seamlessly integrated with OpenFoam to enhance the numericalsimulation process of combustion under ideal gas conditions. Depending on the circumstances, it can boost the66

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19th International Conference on Numerical Combustion

MS16 High-fidelity numerical simulations using
FUGAKU-scale supercomputers in AcademicIndustrial Collaborations
Organizers: Kenji Yamamoto1, Nobuyuki Oshima2, Ryoichi Kurose3
Mitsubishi Heavy Industries, 2Hokkaido University, 3Kyoto University

1

MS16 High-fidelity numericalsimulations using FUGAKU-scale
supercomputers in AcademicIndustrial Collaborations
Chair: Kenji Yamamoto
Co-Chair: Nobuyuki Oshima
Thursday, May 9; 09:50 - 12:10; Room H

Development of High-fidelity numericalsimulations for aviation and powerplantgasturbune combustors
Nobuyuki Oshima , Ryoichi Kurose , Takeo Oda ,Tomoko Tsuru3
1

2

3

temperature and fuel mixture. Carbon less fuel as hydrogen mixing and liquid fuel including spray behavior foraviation engine are most recent challenges towards afull simulation of gasturbine combustors.
Contact: oshima@eng.hokudai.ac.jp

Evaluation of Ignition Feasibility in an
Aviation Engine: Preliminary Equivalence
Ratio Results and Ongoing Developments
in FUGAKU-Enabled, BCM-Based LargeEddy Simulations

Younghwa Cho1, Nobuyuki Oshima1, Rahul Bale2, ChungGang Li3, Makoto Tsubokura2, Tomoko Tsuru4, Takeo Oda4

1

Hokkaido university, Japan, 2Kyoto university, Japan, 3Kawasaki Heavy
Industries, Japan1
Hokkaido University, Japan, 2RIKEN Center for Computational Science,
Japan, 3National Cheng Kung University, Taiwan, 4Kawasaki Heavy
Industries, Ltd., Japan

Prediction of complex behavior of turbulent combustion flow in the gasturbine combustor has been amajor industrial target of high-performance computing
challenge. During these two decades, computer power
development enables to perform thousand time largerof grid resolution (around 10 million to 100 billion grids)
to simulate the combustors of industrial gasturbine.
For this purpose, collaboration researches by using thesuper-computers as “Earth simulator”, “K” and “Fugaku”
have developed the high-fidelity numerical simulationof turbulent combustion flows. They have investigatednumerical models of large eddy simulation (LES) andflamelet approach, and also validated them for aviationand powerplant gasturbine combustors by the implementation to high-performance computing software as“Frontflow/red” and “CUBE” specially designed for thelatest supercomputer in 2000’s and 2020’s, respectively.
High-resolution LES has revealed turbulent mixing behavior and flame holding mechanism in the detail designof industrial combustors. Prediction of NOx production
under lean turbulent combustion are well developed by
the high-fidelity solution of instantaneous profiles ofThis work leverages the high computational powerof the supercomputer FUGAKU in combination with the
Building-Cube Method (BCM) to carry out large-eddy
simulations (LES) that assess the likelihood of ignite ina target aviation engine combustor. The inquiry focuses
on examining the distribution of the equivalence ratio,
which can serve as an indicator of ignition occurrences.
The utilization of BCM, particularly the "CUBE" framework
developed by the Riken Center for Computational Science (RCCS), is an essential feature of this study since itenables rapid and realistic simulation of intricate engine
designs.
This work is currently progressing towards comprehensive combustion modeling. However, the current emphasis
is on investigating the dynamics of spray particles using
an Euler-Lagrangian approach, with n-Dodecane being
used as the fuel. This approach provides initial observations regarding the feasibility of reaching ignition.
In addition, the compressible immersed boundary
approach (IBM) is employed to efficiently handle the complex geometry of aviation engines. The presentation will
also address prior research that has played an essential67MS16 High-fidelity numerical simulations using FUGAKU-scale supercomputers in Academic-Industrial Collaborations

role in enhancing the use of large-scale spray combustion
LES, accurately capturing the complex features that define
aviation engine combustors.
Contact: younghwa@eis.hokudai.ac.jp

Performance Evaluation of Aero Engine
Combustor by LES Integrating Turbulent
Atomization Model
Yusuke Komatsu1, Junya Yoshida2, Junji Shinjo3, Hiroaki
Watanabe4, Masahiro Uchida11erates electricity by burning oxygen and hydrogen in a
stoichiometric ratio with steam dilution. Therefore, this cycle is a zero-emission and carbon-free power generation
system that does not produce nitrogen oxides (NOx) or
carbon dioxide (CO2). In this study, large eddy simulation(LES) is performed for the entire flow field of the combustor in this cycle, including the cooling flow path, andthe validity of the LES is investigated by comparing withthe experiments. The results show that the present LES iscapable of capturing the general behavior of the combustion-steam dilution-cooling flow fields in the combustor.
Contact: hiroki1.kasuya@toshiba.co.jp

IHI corporation, Japan, 2Numerical Flow Designing CO.,LTD., Japan,
Shimane university, Japan, 4Kyushu university, Japan

3

Performance requirements for jet engines are becoming
increasingly severe, requiring the use of numerical simulations for rapid and efficient development. Increasing thescale of simulation and improving accuracy are required fordevelopment applications. In this study, integration of thefuel atomization process into combustion LES was focused
to further improve the accuracy of performance prediction.
Liquid atomization processes are elementary processes
that have a significant impact on combustor performance,
but the complexity of the phenomena makes it difficult to
integrate them into turbulent combustion simulations. To
integrate turbulent atomization into turbulent combustion
calculations, the liquid behavior was calculated using Euler-Euler method and the droplets after atomization were
calculated as Lagrangian particles. The process of atomization from the Eulerian phase liquid is described by a
LES subgrid type turbulent atomization model. Simulations
were performed for kerosene combustion in a three-sector
high-pressure combustor to evaluate the impact of themodel. Simulation results confirm that the integration of
the turbulence atomization model has a significant effecton the combustion behavior in the vicinity of the injector.
This is because the turbulence atomization model affects
the fuel/air mixing behavior at the flame tip, which also affects emission prediction.
Contact: uchida7785@ihi-g.com

Numerical investigation of oxygenhydrogen combustion with steam dilution
for a zero-emission power generation
systemHiroki Kasuya1, Yasunori Iwai1, Masao Itoh1, Yuichi
Morisawa1, Takayuki Nishiie2, Kazuhiro Kinuta3, Ryoichi
Kurose3

Numerical simulation of boundary layer
flashback of hydrogen-air premixed flameusing an LES/NA-FGM-PD approach
Shinichi Fukuba1, Takayuki Nishiie2, Kazuhiro Kinuta3,
Kazuya Iwata3, Ryoichi Kurose3
Mitsubishi Heavy Industries, Ltd., Japan, 2Numerical Flow Designing
CO.,LTD., Japan, 3Kyoto University, Japan

1

Prevention of flashback is one of the key issues for the
Dry Low NOx (DLN) hydrogen-fired gas turbine combustor. In order to accelerate the combustor development,
high-precision, and low-cost numerical simulation technology is required. Reproducing the boundary layer flashbackof the hydrogen flame using computational fluid dynamics(CFD) is challenging because it requires resolving the turbulent boundary layer while considering the heat loss to
the wall and the preferential diffusion effect. In this study,a large eddy simulation (LES) employing a non-adiabatic
flamelet-generated manifolds approach considering theeffects of heat loss and the preferential diffusion, referred
to as an NA-FGM-PD method, is applied to simulate hydrogen-air premixed flame propagating in a rectangularchannel. Then, the validity of the NA-FGM-PD approachto predict boundary layer flashback is examined by comparing it with the experimental data. The results show thatan NA-FGM-PD approach captures the flashback limit
variation and flame behavior observed in the experiments,
in which flashback occurred when increasing equivalence
ratio or decreasing air flow velocity. This suggests that
the NA-FGM-PD approach will be an effective tool in thedevelopment of DLN hydrogen-fired gas turbine combustors.
Contact: shinichi.fukuba.qf@mhi.com

Toshiba Energy Systems & Solutions Corporation, Japan, 2Numerical Flow
Designing CO., LTD., Japan, 3Kyoto University, Japan1

The oxygen-hydrogen combustion turbine cycle gen-68

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19th International Conference on Numerical Combustion

MS16 High-fidelity numerical simulations using FUGAKU-scale supercomputers in Academic-Industrial Collaborations

Super-simulation of Coal Gasification
Facility on Fugaku

Shinobu Yoshimura1, Hiroaki Watanabe2, Ryoichi Kurose3,
Tomonori Yamada1, Shigeki Kaneko1
The University of Tokyo, Japan, 2Kyushu University, Japan, 3Kyoto
University, Japan1

In our work, we target one of innovative clean energy
systems, i.e. carbon-free coal gasification plant. The coalgasification is one of the key technologies to drasticallyreduce CO2 emission from coal fired power generation.
Coal is crushed into fine particulate matter and thenpartially burned into gas in a high-pressure and elevated-temperature environment. We perform a high-fidelity
two-way coupled simulation of combustion turbulent
flow and thermal conduction and cooling in a reactor
vessel of a laboratory-scale coal gasification facility. We
first explain our developed multiphysics and multiscale
simulations on the Supercomputer Fugaku, which we callSuper-simulation in short. Here a unique parallel coupler,
REVOCAP_Coupler, is used to integrate highly parallelized
independent solvers such as a FVM-based combustion
LES flow solver, FFR-Comb, and a FEM-based thermal
conduction and cooling solver, ADVENTURE_Thermal.
The simulation results are quantitatively compared withexperimental results obtained from the laboratory-scale
experimental facility. We succeeded in quantitatively reproducing the experimental phenomena in the facility withregard to temperature distribution as well as generated
chemical components. The developed simulations will be
powerful tools to improve the design and operation of actual coal gasification plants.

ditions and the gasifier configuration. CFD calculations
were performed using Euler-Euler calculations with FrontFlow/red, and the multi-objective optimization algorithm
was NSGA-II. Burner blowout velocity, oxygen concentration, steam concentration, and gasifier configuration wereset as design variables, and the objective functions were
maximize gas heating value, maximize H2/CO ratio, andminimize char volume. The results showed that Pareto
fronts were observed for each gasifier geometry, indicating that multi-objective optimization calculations may beutilized for gasification reactor design.
Contact: k-tanno@criepi.denken.or.jp

Contact: yoshi@sys.t.u-tokyo.ac.jp

Multi-objective optimization of operating
conditions and reactor configuration of
gasifier for solid fuels using FUGAKUKenji Tanno1, Satoshi Umemoto1, Hiroaki Watanabe2,
Ryoichi Kurose1
Central Research Institute of Electric Power Industry, Japan, 2Kyushu
University, Japan

1

Among recycling technologies for plastics and otherchemical products, gasification is one of the most promising recycling technologies because it can treat wastes
that are difficult to recycle as materials and has very highefficiency because it is processed in a reactor at high temperature and pressure. However, suitable operating conditions and gasifier configuration vary depending on theproperties of the feedstock. In this study, multi-objective
optimization calculations based on the genetic algorithm
were performed to investigate the optimal operating con-

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MS17 Machine learning techniques for reacting
flow simulation and analysis
Organizers: Abdulla Ghani1, Anh Khoa Doan2, Hiroshi Gotoda3

Technical University of Berlin, 2Delft University of Technology, 3Tokyo University of Science1

MS17-1 Machine learningtechniques for reacting flow
simulation and analysis (1)Chair: Anh Khoa Doan
Co-Chair: Hiroshi Gotoda
Friday, May 10; 13:00 - 15:00; Room L

Data-driven identification of precursors
of extreme events in reacting flows

Mihnea Khoa Floris , Tadikonda Shiva Sai Sai , Dibyajyoti
Nayak2, Ivan Langella1, Konduri Aditya2, Nguyen Anh
Khoa Doan1
1

2Delft University of Technology, Netherlands, Indian Institute of Science,
India

1

2

Many combustion systems can exhibit extreme events
which are events where the combustor exhibits large
excursions away from its design point. Examples of such
events are flame blow-out or flashback in hydrogen combustors. The prediction of such events is very challenging
due to the complex chaotic and multiscale effects at theorigin of these events and the limited observations wehave of those.
In this work, we develop machine learning techniques
to identify precursors of extreme events, and specifically
we tackle the problem of flashback prediction in a leanhydrogen reheat combustor which exhibits intermittent
flashback. We first use a co-kurtosis based approach toidentify the features of the thermochemical and flow state
which are the most relevant for the onset of flashback.
This allows for an efficient low-dimensional representation. From this reduced representation, a modularity-based
clustering algorithm is employed to segregate between
clusters which contain normal and extreme (flashbacking)states, and the cluster located in-between these states,
which are the precursor states of flashback.
We show that our approach is able to identify precursors of flashback that provide a prediction time relatively
large compared to the duration over which the combustor
is stable between two flashback events. The performanceof our method when using shorter time series or other70sets of features (such as those coming from measurable
quantities) is also investigated.
Contact: n.a.k.doan@tudelft.nl

Synchronized state and formation
mechanism of spray combustion
oscillations in a backstepped combustor
Kenta Kato1, Hiroyuki Hashiba1, Jun Nagao2, Hiroshi
Gotoda1, Yusuke Nabae1, Ryoichi Kurose2
1

Tokyo University of Science, Japan, 2Kyoto University, Japan

We examine the synchronized state and formation
mechanism of spray combustion oscillations in a backstepped combustor from the perspective of symbolic dynamics and machine learning. We use the symbolic recurrence quantification analysis [Mori et al., Proc. Combust.
Inst., vol. 39, p. 4671, 2023; Mori et al., Phys. Rev. Appl.,
vol. 19, 034097, 2023] and the causality analysis basedon a random forest [Leng et al., Chaos, vol. 29, 093130,
2019] to the numerical results obtained by a large-eddy
simulation [Kitano et al., Combust. Flame, vol. 170, p. 63,
2016; Pillai et al., Combust. Flame, vol. 220, p. 337, 2020]. A
phase-synchronized state (desynchronized state) between
the acoustic pressure and heat release rate fluctuations
exhibits in the upstream region (downstream region) of
the combustor. This is clearly identified in the recurrence
rate on the symbolic recurrence plots. The causal analysis based on a random forest reasonably shows that thelarge-scale organized vortex motion significantly affects
the mutual coupling between the acoustic pressure andheat release rate fluctuations with pseudo-periodic dynamics.
Contact: 4523521@ed.tus.ac.jp

19th International Conference on Numerical Combustion

MS17 Machine learning techniques for reacting flow simulation and analysis

Probabilistic Machine Learning for DataBased Flame Dynamics Modeling
Axel Zimmermann, Alexander J. Eder, Camilo F. Silva,
Wolfgang Polifke
Technical University of Munich, Germany

Accurately modeling flame dynamics is crucial for predicting thermoacoustic instabilities. While neural networks
have demonstrated their effectiveness in reproducing thenonlinear dynamics of laminar premixed flames, their applicability to turbulent flames has yet to be demonstrated.
The challenges in this application are manifold: Firstly, thesparsity of data, resulting from the high computational demand of reacting flow simulations; secondly, the presenceof combustion noise resulting in noisy data; and thirdly,
the 'black box' nature of these models raises questions
about their reliability for industrial use.
In this study, we seek to address the aforementioned
issues using Bayesian neural networks (BNNs). BNNs
promise a significant advantage in this context due totheir inherent capability to quantify uncertainty. Uncertainty estimation can provide insights into data requirements
across various flame dynamics regimes, thus potentiallyreducing the overall required data. Moreover, with BNNs,
combustion noise can be naturally modeled by choosing
an appropriate likelihood function.
We first present the capabilities of the Bayesian approach on a laminar premixed flame. We train the networkon broadband-forcing data and evaluate whether the predicted flame-describing function and the associated confidence intervals can be trusted. Subsequently, we show
first results for turbulent flames.
Contact: axel.zimmermann@tum.de

Data assimilation for reacting flows:
Deep learning PDE models to augment
turbulent combustion simulations
Priyesh Rajesh Kakka, Jonathan F MacArt
University of Notre Dame, United States

The traditional Boussinesq and gradient-diffusion hypotheses in turbulence modeling struggle to accurately
represent turbulent fluxes in premixed flames, mainly due
to counter-gradient transport. Current methods to include
heat-release effects in turbulence closures often rely on
linear combinations of limit case models, indicating a needfor a more adaptable, comprehensive approach for diverse turbulent combustion regimes. In response, we propose to augment traditional turbulence models with deepneural networks in a data assimilation framework. These
networks are trained to improve low-fidelity partial differential equation (PDE) models using high-fidelity data by

employing a PDE-constrained, adjoint-based optimization
algorithm. This approach has proven to be effective fortraining turbulence models in both nonreacting large-eddy simulation (LES) and Reynolds-averaged Navier–Stokes(RANS) frameworks. A crucial element of this strategy is
PyFlowCL, a high-performance solver for compressible
turbulent reacting flows. It solves both the forward andadjoint PDEs, needed for model training, by leveraging
automatic differentiation capabilities. We introduce aneural-network-aided RANS closure model and demonstrate its capability to predict the evolution of turbulent
jet flames across a range of Damköhler numbers. The
model’s generalizability is further tested for out-of-sample
cases, marking a significant enhancement in RANS modelclosures for turbulent combustion prediction.
Contact: pkakka@nd.edu

A Probabilistic Framework for Data
Assimilation of Reacting Dynamical
Systems using a Gaussian Process
Regression-based Reduced-Order Modeland Sparse Measurements

Alberto Procacci, Salvatore Iavarone, Laura Donato, Axel
Coussement, Alessandro Parente
Université Libre de Bruxelles, Belgium

The objective of this work is to develop a mathematical framework to assimilate sparse noisy measurementsof a dynamical system with the prediction coming from a
Gaussian Process regression-based reduced-order model,
in a fully Bayesian fashion. The reduced-order model ofthe dynamical system is built by coupling dimensionality
reduction, obtained using the proper orthogonal decomposition, and non-linear regression via Gaussian Process
regression. The Gaussian Process regression is a Bayesian
regression framework in which the prediction is modeled
as a sample from a multivariate Gaussian distribution. This
characteristic can be leveraged to represent the dynamical system as a stochastic model, by employing the mean
and uncertainty of the predictive distributions as parameters of the model.
The sparse measurements are also modeled as a stochastic process represented by a multivariate Gaussian
distribution. This let us assimilate the measured samples
and the reduced-order model by conditioning its predictive distribution with the sparse measurements.
This framework is tested on a pulsating laminar
non-premixed methane flame, in a nitrogen-diluted coflow. The results are compared with established methods
for data assimilation such as the Ensembled Kalman Filter.
Contact: alberto.procacci@ulb.be71

MS17 Machine learning techniques for reacting flow simulation and analysis

Turbulence Fine-scale Reconstruction
Using Learning Techniques

Andreas H Rauch, Anthony Carreon, Venkat Raman
University of Michigan, United States

Turbulent flows are critical to engineering combustion
applications, but numerical simulations of practical engineering devices cannot afford to resolve all turbulence
and flame features throughout the domain. This motivates
multiscale modeling approaches using adaptive meshrefinement (AMR). AMR enables the efficient simulationof a vast range of length and time scales through targeted refinement of local features. However, generating
finer meshes using AMR alone cannot restore high wavenumber turbulence features at the interface between
mesh levels. This requires super-resolution turbulence
to provide high-fidelity inflow conditions to fully resolved
regions. This work explores novel learning techniques togenerate sub-grid scale turbulence for super-resolution
boundary conditions. Shock-turbulence interaction simulations are performed at coarse and fine resolutions to generate matching training data pairs. Then, learning techniques, including a U-net model, are trained to generate
sub-grid scale turbulence from an input coarse turbulent
field, restoring fine-scale turbulent kinetic energy in the
post-shock region, where the turbulent scales drasticallyreduce. This offers a computationally efficient approachfor high-fidelity simulations of shock-laden reacting flows,
including detonations and supersonic combustion.

turbulent lean hydrogen/air flames are prone to thermodiffusive instabilities, resulting in a highly wrinkled
flame front and a substantial increase in flame speed.
However, DNS is computationally prohibitive for engineering applications, necessitating reduced-order approaches,such as large-eddy simulation (LES). Conventional turbulent combustion LES models, though, face challenges
in accurately simulating turbulent lean hydrogen flames,
leading to a considerable discrepancy between LES andDNS. Ongoing modeling efforts have addressed many of
the unclosed LES terms; however, models for the subgrid-scale (SGS) stress tensor and scalar fluxes still havesevere shortcomings in regimes relevant to hydrogen
combustion, where instabilities manifest across different
scales, starting from small and growing to larger scales.
Therefore, improving the modeling of these fluxes is crucial, and considering the super-resolution (SR) approach
becomes fundamental to accurately reconstruct SGS fluctuations.
We propose a dynamic data-driven mixed model thatcombines an SR, machine-learning-based, scale-similarity
model, which explicitly reconstructs SGS terms, and an
eddy-viscosity type model. A priori tests for lean premixed
turbulent hydrogen slot-jet flame show a high correlationof the instantaneous SGS stress and scalar fluxes withthe corresponding DNS data. A posteriori LES simulations
will be presented to assess the ability of the data-driven
mixed model to represent the thermodiffusive instabilities
and flame-turbulence interactions.
Contact: l.nista@itv.rwth-aachen.deContact: ahrauch@umich.edu

MS17-2 Machine learningtechniques for reacting flow
simulation and analysis (2)Chair: Anh Khoa Doan
Co-Chair: Abdulla Ghani
Friday, May 10; 15:20 - 17:20; Room L

A Dynamic Data-Driven Mixed Modelfor the Subgrid-Scale Stress Tensor and
Scalar Fluxes in Large-Eddy Simulation of
Turbulent Lean Hydrogen Flames
Ludovico Nista1, Fabian Fröde2, Temistocle Grenga3,
Jonathan F. MacArt4, Antonio Attili5, Heinz Pitsch2

RWTH Aachen University , Germany, 2RWTH Aachen University, Germany,
University of Southampton, United Kingdom, 4University of Notre Dame,
United States, 5University of Edinburgh, United Kingdom
1

3

Direct numerical simulations (DNS) have shown that72

Large-Eddy Simulation of flamelesscombustion with neural-network driven
chemistryLuc Vervisch1, Huu-Tri Nguyen2, Camille Barnaud3, Danh
Nguyen4, Pascale Domingo5
INSA ROUEN NORMANDY, France, 2Verallia , France, 3Ariane Group,France, 4ArcelorMittal, France, 5CNRS, France

1Large eddy simulation of a flameless combustion furnace is discussed with a comparison against experimental
measurements of the mean thermochemical quantities.
The focus is on introducing flow simulations of complex
chemistry through the training of neural networks, tosimulate the oxidation of a gaseous fuel representative ofrecycled gases available in the steel industry. A canonicalproblem, based on a non-adiabatic stochastic micro-mixing model and combined with a detailed chemistry description, is set up to train the neural networks before theflow simulation. For these networks to be predictive, thethermochemical composition space is automatically decomposed into sub-domains from a partitioning algorithm.

19th International Conference on Numerical Combustion

MS17 Machine learning techniques for reacting flow simulation and analysis

A neural network is trained in every sub-domain to returnthe increments in time of the most influential thermochemical quantities, from the knowledge of temperatureand species mass fractions solved with the flow. Implemented in an open-source low-Mach number fluid mechanics code, the neural networks complex chemistry is
shown to be very efficient in CPU time, with an overheadof only 60% compared to the non-reactive multi-species
simulation of the furnace.
Contact: luc.vervisch@insa-rouen.fr

A comprehensive study on the accuracy
and generalization of deep learninggenerated chemical ODE integrators
Ruixin Yang, Han Li, Zhi X Chen
Beijing University, China

The application of deep neural networks (DNNs) shows
significant promise as a viable alternative to directly integrating chemical source terms in combustion simulations.
However, challenges persist in ensuring high precisionand generalization across various fuels and flow conditions. In this study, we propose and validate a consistent
DNN approach for integrating chemistry across a rangeof fuels and premixed flame configurations. This approach
involves generating a thermochemical base state froma set of low-dimensional laminar flames, followed by aneffective perturbation strategy to enhance coverage ofthe composition space for improved generalization. A
constraint criterion based on heat release rate is thenapplied to eliminate nonphysical perturbed states, thereby enhancing overall accuracy. Without specific tuning,
three DNNs are consistently trained for three representative fuels: hydrogen, ethylene, and Jet-A. Comprehensive
validations are conducted using 1-D laminar flames andtwo typical turbulent premixed flames. The DNN model
predictions for various physical characteristics, such as
laminar and turbulent flame speeds, dynamic flame structures influenced by turbulence-chemistry interactions, andconditional scalar profiles, exhibit good agreement withresults obtained from direct integration. This underscores
the exceptional accuracy and generalization ability of the
proposed DNN approach. Furthermore, when the DNN
is employed in simulations, a significant acceleration inchemistry integration is achieved, with approximately a50-fold increase for the ethylene/air flame and a 90-foldincrease for the Jet-A/air flame.
Contact: risinyoung@zju.edu.cn

A combined PCA-CSP solver for
dimensionality and stiffness reduction inreacting flow simulations

Rafi Malik1, Riccardo Malpica Galassi2, Hong G. Im1, Mauro
Valorani2
1

King Abdullah University of Science and Technology, Saudi Arabia,
Sapienza University, Italy

2

In reacting flow simulations, reduced-order models(ROM) play a crucial role in enhancing our understandingof the physical processes and accelerating simulations.
Data-driven Principal Component Analysis (PCA) for dimensionality reduction and the physics-based Computational Singular Perturbation (CSP) for temporal stiffness
reduction have demonstrated their effective roles in accelerated computing without losing fidelity.
The present study proposes a new algorithm, that combines the benefits of both methods by a double mapping
operation from the state-space to time-decoupled andlower-dimensional PCA-CSP latent variables. In this approach, the complex reactive system is first mapped onto
the orthogonal space by the PCA projection, followed by
the dynamical time-scale decomposition of CSP operated
on the PC-score variables, such that the time integrationis performed on the active modes using the G-scheme
algorithm. The PCA-CSP methodology also introduces theconcept of latent Jacobian, representing the Jacobian matrix in the latent space of PCA variables.
The approach is validated on an ignition test caseof a homogeneous ammonia/air mixture with detailed
chemistry. Significant computational savings are achieved
through the eigenvalue decomposition of the much smaller latent Jacobian matrix of the PC scores, without loss of
accuracy. The results suggest a potential for the PCA-CSP
algorithm to achieve substantial acceleration of high-fidelity reacting flow simulations involving large number ofvariables with a wide spectrum of time scales.
Contact: mohammadrafi.malik@kaust.edu.sa

Physics-Informed Neural Networks for
Turbulent Combustion: Extracting Closure
from Multiscalar Measurements

Arsalan Taassob1, Anuj Kumar1, Kevin M. Gitushi1, Rishikesh
Ranade2, Tarek Echekki1
1

North Carolina State University, United States, 2Ansys, Inc., United States

We develop a physics-informed neural network (PINN)
to evaluate closure terms for turbulence and chemicalsource terms from temperature, major species, and velocity point measurements. The goal is to develop closurefor the transport of momentum and the thermo-chemical
state. We adopt a deep operator network (DeepONet)73

MS17 Machine learning techniques for reacting flow simulation and analysis

to accommodate two sub-networks related to two inputs: the spatial coordinates and flame inlet parameters,
including inlet velocities and recess lengths of the fuelinlet. The PINNs are trained on several Sydney Flames
and validated on an additional flame. A relatively shallow
network attached to PINNs is used to relate the unconditional means of the species to their source terms in theirtransport equations. Additional observations of the PINNs
are evaluated for the species' reaction rates. The terms
are evaluated by integrating the species’ reaction rates
conditioned on principal components (from principal component analysis implemented on experimental data) andthe principal components’ joint PDFs from the experimental data. The measured species' reaction rate conditional
means are evaluated using 0D simulations to recovernon-measured species and evaluate reaction rates. The
results show that the species, the mixture fraction, andthe axial and radial velocity components can adequately
be represented with PINNs compared to experimental
statistics. Moreover, PINNs can reconstruct closure terms
associated with turbulence and scalars' transport, including the species' chemical source terms.
Contact: techekk@ncsu.edu

Sparse data and reactive flow physicsinformed neural networks
Abdulla Ghani

Technische Universität Berlin, Germany

In this talk, I will present a new method to reconstruct
reactive flow fields based on sparse data. To do so, wedeveloped neural networks that incorporate governing
equations for reactive flow fields, called reactive flow
physics-informed neural networks (RF-PINNs). The goal
is to perform flow field reconstruction using a minimal
amount of data, e.g. a handful of velocity profiles obtained
from PIV measurements. I will demonstrate the effectiveness of our method on multiple cases including laminarand turbulent flames, and discuss future work in this field.
Contact: ghani@tu-berlin.de74

19th International Conference on Numerical Combustion

MS18 Data-driven tools for HPC simulations ofe-fuels combustion
Organizers: Federica Ferraro1, Alessandro Stagni2
Technical University Braunschweig, 2Politecnico di Milano

1

MS18 Data-driven tools for
HPC simulations of e-fuels
combustion
Chair: Federica Ferraro
Co-Chair: Alessandro Stagni
Friday, May 10; 09:50 - 11:50; Room H

A workflow for the semidetailed modelingof complex e-fuels: application tooxymethylene ethers

Alessandro Stagni1, Timoteo Dinelli1, Alessandro Pegurri1,
Andrea Bertolino2, Alessandro Parente2, Marco Mehl1,
Tiziano Faravelli11Politecnico di Milano, Italy, 2Université Libre de Bruxelles, Belgium

When the chemical complexity of e-fuels grows to ahigher level, as is the case of oxymethylene ethers (OMEs),
the resulting kinetic mechanisms might have a limited
applicability due to their size. In this case, simplification
techniques need to be implemented for their integration
into HPC simulations. In this work, we show that the kinetic modeling of longer-chain fuels can be simplified toa great extent by building up a single workflow, based oni) the definition of a smaller, archetypal species (dimethoxymethane – or OME1); ii) the coupling between lumping
techniques and analogy and rate rules, based on the archetypal species, to develop the reaction submodules ofeach OME; iii) a data driven optimization, based on reaction classes, retaining the consistency previously definedamong the different modules.
Such a workflow proved able to finalize a semidetailed
model, with accuracy features competitive with the literature mechanisms, as shown by the large-scale validation
performed for each of the components of the OME family.
At a second stage, this can be effectively coupled withskeletal reduction methodologies, to bring the size of themechanism to acceptable levels for HPC applications.

Leveraging data assimilation techniques
to integrate experimental and synthetic
measurements in the kinetic mechanismsof e-fuels
Timoteo Dinelli1, Tiziano Faravelli2, Alessandro Stagni2,
Matthias Ihme1
1

Stanford University, United States, 2Politecnico di Milano, Italy

The current development of kinetic mechanisms relies
heavily on the data-driven optimization of kinetic rates,
previously evaluated by direct measurements and quantum chemical calculations. Different methods have beendeveloped to integrate information from experimental
measurements into kinetic models, including the solution
mapping method by Frenklach or the Method of Uncertainty Minimization using Polynomial Chaos Expansions
by Sheen and Wang. Recently, the Bayesian approach
has attracted significant attention in the chemical kinetics community, as it provides a probabilistic approach toquantify uncertainties from both prior knowledge andexperimental data. In this context, data assimilation (DA)methods offer opportunities to integrate experimental
and synthetic measurements into numerical simulations.
Among the various DA techniques, the Ensemble Kalman
Filter (EnKF) is selected for this research due to its ability
to include quantities not contained in the solution vector,
and its robust evaluation of the error covariance: it is astatistical method, applicable to large-scale inverse problems like the one faced in this research. To this end, we
have explored the possible applications of EnKF to optimize rate parameters of kinetic mechanism for promisinge-fuels candidates.
Contact: timoteo.dinelli@stanford.edu

Contact: alessandro.stagni@polimi.it

75

MS18 Data-driven tools for HPC simulations of e-fuels combustion

Enhancing computational efficiency oflaminar flames simulations through timedependent bases
Eva Muñoz1, Hessam Babaee2, Alessandro Parente1

Université Libre de Bruxelles, Belgium, University of Pittsburgh, UnitedStates1

2

Combustion is inherently complex, as it involves multiple scales and intricate physical processes, resulting incomputationally expensive simulations in terms of both
memory and CPU time. To address this challenge, reduced-order models play a crucial role in enhancing ourunderstanding of the process and accelerating simulations.
This research focuses on reduced-order modeling using the time-dependent bases (TDBs) approach [1]. TDB
solves species transport equations for basis vectors in a
low-dimensional manifold. The method is data-free anddesigned to ensure that the projection operator adjusts
and rotates to align with the instantaneous flow characteristics, making it potentially suitable for unsteady problems.
The objective of this study is to investigate the method
potential for a range of fuels and operating conditions,
identifying strategies to maximize the reduction potentialof the approach. To this purpose, TDB approach is implemented in laminarSMOKE [2], an OpenFOAM-based
software designed to solve laminar flames with detailed
chemistry. The analysis covers CFD simulations of steadyand transient laminar axisymmetric coflow diffusion
flames burning mixtures of burning mixtures of H2, CH4,
or n-heptane with N2 in air [3, 4].
[1] Ramezanian D., Nouri A.G., Babaee H. Computer Methods in Applied Mechanics and Engineering, 382, 8, 2021.
DOI:10.1016/J.CMA.2021.113882.
[2] Cuoci A., Frassoldati A. et al. Energy and Fuels 2013 27(12), 7730-7753. DOI: 10.1021/ef4016334.
[3] Toro V. V. ,Mokhov A. V. et al. Proceedings of the Combustion Institute, 30, 1, 1 2005. DOI:10.1016/J.PROCI.2004.08.221.
[4] D’Alessio G., Parente A. et al. Combustion and Flame,
211, 1, 2020. DOI:10.1016/J.COMBUSTFLAME.2019.09.010.
Contact: eva.munoz.salamanca@ulb.be

Evaluation of Neural Network
Performance for Chemistry Closure
through Domain Decomposition

T.Jeremy Karpowski1, Federica Ferraro2, Arne Scholtissek3,
Christian Hasse3
TU Darmstadt, Germany, 2TU Braunschweig, Germany, 3TU Darmstadt,
STFS, Germany

1

Artificial Neural Networks (ANN) are emerging as adata-driven alternative for the chemistry closure in CFD ofreactive flows for their capabilities of learning the correlation between transported control variables and the fullthermochemical state, including also the relevant chemical source terms.
However, ANNs are not directly trainable to a sufficient
relative tolerance when the output quantities span multiple orders of magnitude, which is the case for chemicalsource terms.
To overcome this issue, previous works applied multiple networks, each responsible for a subset of the fullchemistry manifold of the training data. It was observed
that, with an increase in the number of subdomains, simpler networks are able to predict their respective subdomain with higher accuracy compared to a single network.
In this work, an ensemble neural network (eNN) model for predicting the species chemical source terms inreacting flows is presented. Specifically, the decomposition method, the accuracy of the resulting eNN, and thelimitation of the approach are explored in a parameter
study. The proposed closure is applied to test cases ofincreasing complexity for hydrogen-air mixture, including
autoignition problems and laminar premixed flames thatdevelop thermo-diffusive instabilities.
Contact: federica.ferraro@tu-braunschweig.deAnalysis of flamelet-based manifolds forturbulent H2-flames subject to thermodiffusive instabilities

Hannes Böttler1, Driss Kaddar1, Jeremy Karpowski1, Federica
Ferraro2, Arne Scholtissek1, Hendrik Nicolai1, ChristianHasse1
Technische Universität Darmstadt, Germany, 2Technische Universität
Braunschweig, Germany

1

While flamelet-based modeling techniques have beensuccessfully applied in many scale-resolving simulationsof turbulent hydrocarbon flames, transferring the approach to (lean) turbulent hydrogen flames still representsa challenge. One of the reasons is the fine-scale wrinklingof the flame front due to both, intrinsic thermo-diffusive
instabilities and turbulence, which leads to an increasein the flame surface area and consequently the flame’s

76

19th International Conference on Numerical Combustion

MS18 Data-driven tools for HPC simulations of e-fuels combustion

burning rate. In an earlier work, we have demonstrated
the application of flamelet-based models to laminarthermo-diffusively unstable hydrogen flames, which has
shown that including curvature effects in the generationof the manifold leads to improved model predictions. In
the present work, we analyze this modeling technique fora turbulent hydrogen flame. A DNS of a turbulent leanpremixed hydrogen-air slot flame with finite-rate chemistry is carried out first. The flame’s thermochemical stateis examined using a composition space model, separately
considering effects from strain and curvature. An a-priori
analysis confirms that the previously developed tabulated
manifolds fall short of capturing all the turbulent flame
phenomena. An extended manifold, spanned by control
variables for mixing, reaction progress, strain, and curvature, is shown to improve the results significantly. With
this, the present work provides novel insights into therequired manifold complexity for capturing the physics ofturbulent lean hydrogen flames.
Contact: scholtissek@stfs.tu-darmstadt.deA universal LES subfilter model based on
AI super-resolution and application tohydrogen flames
Mathis Bode1, Bogdan Danciu2, Christos Frouzakis2
1

Forschungszentrum Jülich GmbH, Germany, 2ETH Zuerich, Switzerland

The green energy transition requires the adaptationand optimization of many combustion applications. In
particular, the switch to hydrogen as a carbon-free fuelis a key task here. This is not possible without the combination of highly accurate direct numerical simulations(DNS) to understand physical phenomena in detail andreduced models, especially large-eddy simulation (LES),
to address real-world applications. Physics-informed enhanced super-resolution generative adversarial networks(PIESRGAN) are a promising approach to systematicallyderive general LES subfilter models from DNS data. The
general idea is to train an AI network with different datasets in such a way that it is able to "reconstruct" DNS-like
resolution from filtered data. This allows super-resolutionof data in an a priori sense and the accurate prediction of
the temporal evolution in an a posterior sense by closing
the LES equations using the AI super-resolution subfilter
model. This work presents a universal derivative modeland its application to hydrogen flames. Besides the prediction of complex chemistry, a focus is on the simultaneous correct modeling of turbulent flow in complex geometries. The universal subfilter model results in an extremely
good prediction accuracy and can significantly speed upcomplex simulations.
Contact: m.bode@fz-juelich.de

77

MS19 Tabulation Methods for Homogeneous andHeterogeneous Reacting Flow: Machine Learningand Other Approaches
Organizers: Stelios Rigopoulos1, Francesca Di Mare2, Fabian Sewerin3Imperial College London, 2Ruhr Universitat Bochum, 3Otto-von-Guericke University Magdeburg

1

MS19 Tabulation Methodsfor Homogeneous andHeterogeneous Reacting Flow:
Machine Learning and Other
Approaches
Chair: Stelios Rigopoulos
Co-Chair: Fabian Sewerin
Friday, May 10; 09:50 - 12:10; Room L

is shown that accurate results can be achieved for bothmajor and minor species, with a 10-50 times accelerationof the chemical reaction step.
Contact: s.rigopoulos@imperial.ac.uk

Criteria to switch from tabulation toneural networks in computational
combustion

Zacharias Nikolaou1, Luc Vervisch1, Pascale Domingo2

Machine Learning Tabulation of Chemical
Kinetics for Turbulent Combustion
Simulations
Stelios Rigopoulos, Thomas Readshaw, Tianjie Ding,
William Philip Jones
Imperial College London, United Kingdom

The computation of turbulent flames with methods
that involve direct coupling of chemistry and flow is a very
computationally demanding task, especially for large andcomplex mechanisms that are often required to simulate
combustion of commercial fuels, soot formation and newsustainable fuels. We show the progress of a methodology, the hybrid flamelet/random data and multiple multilayer perceptrons (HFRD-MMLP) method, developed within
our research group for a number of years, which employs
machine learning to replace the real-time computationof thermochemistry. As such, it is applicable to methods
such as Direct Numerical Simulation (DNS), Probability
Density Function (PDF) methods, unsteady flamelet, Conditional Moment Closure (CMC), Multiple Mapping Closure (MMC), Linear Eddy Model (LEM), Thickened Flame
Model, the Partially Stirred Reactor (PaSR) method (as in
OpenFOAM) and the computation of laminar flames. The
fundamentals of the method are explained and a numberof case studies are shown for different types of turbulent
flames, fuels and reaction mechanisms. The large eddy
simulation (LES) – PDF approach is employed, together
with the stochastic field method for numerical solution. It

78



1

INSA ROUEN NORMANDY, France, 2CNRS , France

Motivated by the need to reduce computational costs,
look-up tables are widely used in numerical simulationsof laminar and turbulent flames, for the thermodynamics
of the mixture, for detailed chemistry, and for turbulent
combustion closures. At the same time, there have been
many studies where artificial neural networks have been
trained to replace the classic tabulation approach, andtheir performance against tabulation is typically evaluatedafterward. The computational efficiency is an important
ingredient, and criteria are needed to decide whether or
not it is worthwhile in the first place to employ neuralnetworks at all, and if so what the potential bounds on thecomputational time and memory gains (if any) over tabulation are. Analytical expressions will be presented for thecomputational cost of tabulation and of neural networks
including the effect of network structure. The scaling laws
are validated using both model test-data but also data
based on a canonical problem which involves inferringlaminar flame speeds of methane/hydrogen mixtures at
off-training conditions. The proposed scaling laws leadnaturally to a framework for effective decision-making between adopting look-up tables or neural networks.
Contact: luc.vervisch@insa-rouen.fr

19th International Conference on Numerical Combustion

MS19 Tabulation Methods for Homogeneous and Heterogeneous Reacting Flow: Machine Learning and Other Approaches

Classification of thermochemical states
in turbulent premixed combustion using
autoencoder neural networks
Cheng Chi, Pascal Bock, Gabor Janiga, Dominique
ThéveninOtto-von-Guericke University Magdeburg, Germany

Low-dimensional modeling (LDM) of the thermochemical variables, such as Flamelet Prolongation of Intrinsic
low-dimensional manifolds (FPI) and Flamelet Generated
Manifold (FGM), are very useful for combustion simulations, especially when the chemical mechanism is complex. A crucial ingredient for LDM is the choice of low-dimensional representations (i.e., controlling variables),conventionally determined by prior knowledge or principal
component analysis (PCA). Controlling variables determined by prior knowledge are easy to understand andstraightforward to implement in LDM. E.g., a progress variable is used to determine the progress of the flame. However, when the thermochemical states – for instance when
considering detailed transport models – become complex,
additional controlling variables – out of prior knowledge –are needed to obtain an accurate representation. PCA isable to identify low-dimensional representations without
any prior knowledge. Since PCA is in principle a linear
regression, it is well suited for linear problems, but shows
limitations for non-linear processes. In contrast to PCA, anautoencoder neural network (AENN) offers a suitable representation for non-linear problems as well. In this work,
an AENN has been used to obtain the low-dimensional
representations of the intricate thermochemical statesfound during turbulent premixed combustion. Up to now
it is difficult to interpret the physical meaning of the latent
space in the data-driven reduced dimensions. Therefore, adirect application of autoencoder as LDM – to replace FPI
and FGM – is not really feasible. On the other hand, thepresent study takes the benefit of an AENN to classify thethermochemical states based on an automatic sensitivity
analysis (automatic differentiation) of the thermochemicalvariables on the data-driven reduced dimensions. In thisway, the controlling thermochemical variables can be
identified at every local position and grouped to indicate
different combustion process, e.g., ignition, local extinction, flame propagation. Validation of this technique isperformed for NH3/H2/air premixed flames, which are ofincreasing interest for future carbon-free combustion.
Contact: cheng.chi@ovgu.deHarnessing a reduced orderrepresentation to solve the spatiallyinhomogeneous population balance
equation
Fabian Sewerin

Otto von Guericke University Magdeburg, Germany

Aerosols are frequently characterized in terms of aparticle size distribution whose spatial and temporal evolution is governed by a population balance equation (PBE).
Physically, the PBE synthesizes spatial particle transport
due to advection and diffusion with localized particle formation, growth, breakup or coagulation. A particular challenge associated with the numerical solution of the PBE in
a Eulerian framework is the economical parameterizationof the particle size distribution in terms of a finite numberof scalars, affording a size-discrete approximation. With theobjective of minimizing the number of scalars, we present
a novel reduced order representation of the particle size
distribution that involves the notion of size-characteristics
and is informed by training solutions of the PBE acquiredin simplified reactors. The shape functions underlying the
reduced order representation are identified using a proper
orthogonal decomposition (POD) of the training dataset,
while the scalars’ evolution equations are obtained froma constrained Galerkin projection of the PBE. Considering the dispersion and growth of an aerosol in a laminarplane jet flow, we demonstrate that the PBE-POD solver
requires about four times fewer scalars to achieve a given
accuracy than adaptive grid methods. While the achievable accuracy is limited by the adequacy of the training dataset, the PBE-POD method delivers, by design, the best
least-squares approximation of the exact solution in termsof the chosen shape functions.
Contact: fabian.sewerin@ovgu.de

Modeling of Turbulent Reactive Flows
Using a Self-Learning Reduced Order
Model

Kai Niemietz1, Clément Scherding2, Walter Gemassmer1,
Taraneh Sayadi3, Heinz Pitsch1

RWTH Aachen University, Germany, 2Sorbonne University, France, 3CNAM,
France1

Many applications in turbulent combustion rely onsome form of reduced order model. Flamelet-type models
with pre-computed, tabulated chemistry are widely usedand perform well. However, the creation of an appropriate
and accurate table requires considerable knowledge andtime. Data-driven models have shown a lot of promise in
reducing this work. They are fast, simple to use, and can79

MS19 Tabulation Methods for Homogeneous and Heterogeneous Reacting Flow: Machine Learning and Other Approaches

provide high accuracy. But the result is often a black box.
What is more, data-driven extrapolation to new, unknown
data is not obvious. A feature required in most applications.
In this work, we implemented the RONAALP algorithm(Reduced Order Nonlinear Approximation with Active
Learning Procedure) which combines off-line training witha self-learning approach to handle extrapolation eventson-the-fly. The off-line training relies on a combinationof nonlinear auto-encoders, community clustering, andradial basis function networks to develop an efficient andcompact base model from limited training data. The active
learning procedure expands the base model to consider
extrapolation outside of the original training data. The algorithm was developed and validated for hypersonic flows
in non-equilibrium. We transferred the methodology toturbulent reacting flows, training the model on 1D flamelet
data, and using a direct numerical simulation (DNS) of
two parallel turbulent premixed methane/air flames withflame-wall interaction as validation.
The base model performs as well as the original tabulation, without the effort of constructing the appropriate
table. Due to the defined extrapolation procedure, active
learning with either DNS data or additional flamelet data
improves the predictions.
Contact: k.niemietz@itv.rwth-aachen.de

Data driven modelling of sub-grid micromixing for PDF methods
Salvador Navarro-Martinez1, Tin-Hang Un2

Imperial College London, United Kingdom, 2Imperial College London,
Portugal

1

Probability Density Function (PDF) methods have been
proven successful in modelling combustion in a wide
range of configurations. Using a sub-grid joint scalar PDF,
the approach can close the filtered reaction source term
exactly. Moreover, by including velocities into the joint
PDF, the method yields a unified turbulence-chemistryinteraction model. These methods are very general andhave good synergies with chemistry tabulation methods.
However, the sub-grid PDF transport equation is not fully
closed and requires modelling. Most of the literature used
the Simplified Langevin Model approach, which assume
isotropy at the smallest scales and depends on filter width,
sub-grid kinetic energy and a triad of RANS-calibrated
constants. A more general model requires closure of theLangevin tensor, which includes the turbulent dissipation.
This is a very complex parameter to model due to its intermittent nature, but crucial in modelling extreme events
such as extinction and ignition. This work explores theuse of small Deep Neural Networks (DNN) to represent80a Generalised Langevin Model. A realisability constrain is
imposed to link dissipation and sub-grid Reynold stress.
The Reynolds stresses and velocity gradients are used as
input data of the network. The DNN is trained with forced
isotropic turbulence DNS at three different Reynolds numbers, with different filtering criteria. The new model shows
good agreement with unseen DNS data and outperforms
the SLM at several resolutions.
Contact: s.navarro@imperial.ac.uk

Evaluation of Breakpoint Optimization
Procedure for High dimensional Flamelet
Tables
Himeko Yamamoto, Takanori Haga
Japan Aerospace Exploration Agency, Japan

High-dimensional flamelet tables improve the applicability of the flamelet based models, but increase inmemory size of the table is important issue for massively
parallel computing. In this study, breakpoint optimization
procedure for high-dimensional flamelet tables has beendeveloped, to optimize the balance between memory size
and accuracy of the table. In order to improve an accuracy of the optimization, process of obtaining abundantsolutions of counterflow diffusion flames is automated.
Constrained nonlinear optimization algorithm is applied
for process of finding optimal breakpoints of the table.
Several conditions of the number of breakpoints in eachcontrol parameter of the table and objective functionsin the optimization are evaluated. A priori analysis using
the optimized flamelet table of flamelet progress variableapproach which implemented in a compressible flow analysis solver is conducted for a H2/O2 flame. Finally, thesame framework will be applied to the flamelet table ofquasi-two-dimensional flamelet model.
Contact: yamamoto.himeko@jaxa.jp

19th International Conference on Numerical Combustion

MS20 Modeling and Simulation of High-speed
Compressible Reacting Flows
Organizer : Venkat Raman
University of Michigan

MS20 Modeling and Simulationof High-speed Compressible
Reacting Flows
Chair: Venkat Raman
Thursday, May 9; 09:50 - 12:30; Room K

Stability and Dynamics of High-speed,Compressible, Premixed and Nonpremixed Turbulent Reacting Flows
Alexei Poludnenko

University of Connecticut, United States

In a wide range of practical systems, from hypersonicscramjet engines to detonation-based combustors, turbulent reacting flows operate in rather extreme, high-speed,
highly compressible regimes. In this talk, we discuss several phenomena characteristic of such regimes, whichwere discovered in recent years using direct numericalsimulations. In particular, we show that premixed turbulent flames can develop pulsations with significant peakto-peak amplitudes. Such unstable burning can resultin the pressure build-up and the formation of shocks,
ultimately even driving transition to a detonation, when
the flame speed approaches or exceeds the speed of a
Chapman-Jouguet deflagration. Recent results also show
existence of a similar unstable burning regime in non-premixed flames. Such instability is intrinsic to a flame, and it
can develop even in the absence of the surrounding combustor walls or obstacles. Furthermore, coupling of pressure and density gradients, as well as heat-release-driven
dilatation across the flame can lead to the anisotropic
generation of turbulence inside the flame volume andflame acceleration. In particular, we show that this process
can result in turbulent flame propagation and substantial
self-acceleration even in the absence of the upstream
turbulence. We discuss the physical mechanisms behindthese phenomena along with the implications of theseresults for subgrid-scale LES combustion models.
Contact: alexei.poludnenko@uconn.edu

Effect of Fuel Dispersion on Reaction
Structure in Supersonic Flowpaths
Shivank Sharma, Venkat Raman
University of Michigan, United States

Efficient combustion is a major challenge in the development of hypersonic vehicles. Single transverse injectors
face limitations in the mixing uniformity, thereby impacting the combustion efficiency. Multiport injection schemes
lead to the formation of complicated shock structures
formed by the interaction and reflection of the individual
bow shocks generated due to the blockage of the jets.
These curved shocks enhance the vorticity generation
process, and their interaction with the jet fuel plumes
downstream further strengthens the existing vorticalstructures, leading to enhanced mixing. These configurations, however, suffer from greater pressure losses andsuppression of jet penetration due to the influence of
opposing jets. This work aims to investigate the influenceof different jet-to-crossflow momentum ratios on multiple
sonic ethylene jets issued into a Mach 3 crossflow using
an adaptive mesh refinement (AMR) based compressible
flow solver with detailed chemistry. The analysis will focus
on the influence of the momentum ratio and turbulenceon the mixing, ignition characteristics, and reaction zone
structure for the multiple injector configuration. AMR isemployed to resolve the shocks, shear layers, and reaction
front locations, preserving an overall fidelity comparable
to direct numerical simulation while concurrently maintaining a computational cost akin to large eddy simulation.
Contact: sshivank@umich.edu

High-Order Discontinuous Galerkin
Methods for Compressible, Chemically
Reacting, Multicomponent Flows
Eric J Ching, Ryan F Johnson

US Naval Research Laboratory, United States

This talk presents a nonlinearly stable, high-order discontinuous Galerkin (DG) method for the chemically react-81

MS20 Modeling and Simulation of High-speed Compressible Reacting Flows

ing, compressible Navier-Stokes equations. The following
nonlinear-stability properties are mathematically guaranteed: boundedness of species mass fractions, positivityof density, positivity of pressure, and boundedness (frombelow) of specific thermodynamic entropy. Satisfactionof these properties allows for adequate suppression ofnumerical instabilities and discrete conservation of mass,
total energy, and atomic elements over a wide range ofmeshes and polynomial orders. In addition, the methodology effectively maintains pressure equilibrium in smoothregions of the flow. Operator splitting is employed tohandle stiff chemical reactions. The resulting formulationis compatible with curved elements of arbitrary shape, avariety of numerical flux functions, general quadraturerules with positive weights, and mixtures of thermally perfect gases. Several test cases involving reacting and nonreacting multicomponent flows are computed in a robust,conservative, and accurate manner, ranging from one-dimensional shock-tube and thermal-bubble-advection
problems to multidimensional moving detonation waves,chemically reacting shock/mixing-layer interaction, andreacting jet in supersonic crossflow. This talk will conclude
with discussions on DG's effectiveness, lessons learned inpursuing DG for propulsion simulations, and its potential
role as a future design tool.
Contact: ryan.johnson@nrl.navy.mil

LARGE EDDY SIMULATION (LES) OF
HIGH SPEED COMPRESSIBLE REACTIVE
FLOWS
Christer Fureby

Lund University, Sweden

Large Eddy Simulation (LES) has rapidly evolved asa powerful computational method for high-speed compressible reactive flows, in-between Direct Numerical
Simulation (DNS) and Reynolds Averaged Navier Stokes(RANS) in accuracy and cost. These flows are extremely
challenging due to the combined complexities of turbulent compressible flow and combustion chemistry, putting
additional requirements on the numerical schemes used.
Here we will review the physical processes involved inhigh-speed compressible reactive flows and discuss therequirements for modeling each of these processes. Also
to be commented on, is the interplay between the physics
modeling and the need for low-dissipation schemes withability to capture shocks and other flow discontinuities.
Particular attention will be paid to phenomena not usuallyconsidered in LES of high-speed compressible reactive
flows such as thermal radiation and thermal combustor-wall boundary conditions. Results from a small selection of experimentally investigated supersonic combustion82



cases will be presented, and the sensitivity to chemical
reaction mechanisms, LES combustion models, thermalradiation modeling and thermal combustor-wall boundary
conditions will be illustrated and discussed. Qualitativeand quantitative comparison with experimental data will
guide formulating a set of suggestions regarding how
to make appropriate judgements when selecting the required physical model-ing details and set-ups.
Contact: christer.fureby@energy.lth.se

Chemical Kinetic Modeling for HighSpeed Compressible Combusting Flows

Hai Wang1, Kevin Dong1, Yue Zhang1, Gregory P. Smith2
Stanford University, United States, 2Stanford Research Institute (SRI),
United States

1

High-speed compressible combusting flows are characterized by a significantly broadened thermochemical
state space. Accurate combustion chemistry modeling inthese flows is challenging in two aspects. First, the frequent local extinction and ignition sensitize hierarchicalchemistry to an extent that testing a combustion chemistry model against a small set of legacy combustion property data (e.g., laminar flame speed, shock tube ignition,
counterflow extinction) is insufficient for validating its accuracy over the broader thermochemical state conditions
which can be encountered in high-speed flows. Second,
the broadened thermochemical state space also renders
conventional model reduction strategy inadequate. To
address these problems, we discuss our recent Foundational Fuel Chemistry Model 2 (FFCM-2) effort, focusing on
optimization of a comprehensive H2, H2/CO, C1-4 reaction
model through data assimilation followed by uncertainty
quantification and minimization. In addition, we explore
an approach that combines low-dimensional manifold
identification with deep neural network training to obtain
reduced models for computational fluid dynamics.
Contact: haiwang@stanford.edu

Modelling strategies for Large Eddy
Simulation of high-speed reacting flows
Salvador Navarro-Martinez

Imperial College London, United Kingdom

Numerical simulation of high-speed reacting flows has
many challenges. High-Reynolds number flows requires
turbulence modelling. In scramjets mixing fuel and oxidiser is incomplete due to short residence times and finite
rate effects are important with strong turbulence-chemistry interaction, with large non-linearities in the reaction

19th International Conference on Numerical Combustion

MS20 Modeling and Simulation of High-speed Compressible Reacting Flows

rates. Similarly, in rocket-type cryogenic injectors, non-ideal equations of state introduce complex relations between
the thermodynamic properties. In LES, all these turbulenceinteractions require modelling and implementation in asolver. The simulations require resolving shocks, thin mixing layers and turbulent eddies simultaneously. To maintain stability, numerical schemes add artificial dissipation,
but this process introduces erroneous mixing and dissipates turbulence. This numerical dissipation mask turbulence modelling and artificially coarsen unresolved scales
and can, for example, accelerate the flame or cause blowoff. Sophisticated modelling approaches may be wasted if
dissipative solvers are used. Numerical dissipation can act
as an implicit sub-grid modelling (ILES); however, it canmisrepresent behaviour close to walls or in unresolved regions. The main bottleneck is how to identify a-priori thebehaviour of the combined numerical model-solver. This
work explores modelling strategies on a scramjet configuration, including the effects of several numerical schemes,mesh resolution and combustion models: ILES, PaSR and
PDF approaches.
Contact: s.navarro@imperial.ac.uk

An analysis of non-premixed ethylene-air
flame stabilization in a cavity flameholder
with orthogonal fuel injection
Priyabrat Dash, Konduri Aditya

Indian Institute of Science, Bengaluru, India

Ramjet and scramjet engines are critical for the next
generation of high-speed air travel. In scramjets, theflow is decelerated from a hypersonic freestream Mach
number to a lower supersonic Mach number at the combustor entry. To stabilize flames within the combustor,
cavity flameholders are employed. It is imperative toglean fundamental insights into such flame stabilization
across operating conditions. To do so, we use high-fidelity
simulations of cavity-stabilized non-premixed ethylene-air
flames inside a model combustor resembling a jet-incrossflow configuration at nominal flow conditions. The
combustor geometry comprises a rectangular cross-section with a ramp-cavity, and two injectors (pilot and main)
to introduce the fuel. The simulations are conductedusing the open-source massively parallel code PeleC,
incorporating a 22-species reduced order mechanismwith 206 elementary reactions. We assess the sensitivityof flame anchoring toward perturbations caused by the
pre-combustion shock train by mimicking its unsteadinessin the inlet conditions. The combustion characteristics
and the role of the recirculation zone in assisting ignitionat the flame anchoring point are studied. Additionally, we
conduct a detailed investigation of the progress of individ-

ual reactions and the production/consumption of reacting
species.
Contact: priyabratd@iisc.ac.in

Effect of a Turbulent Chemistry
Interaction Model on Prediction of
Scramjet Combustor Flows

Masatoshi Kodera, Masahiro Takahashi, Kan Kobayashi,
Sadatake Tomioka
Japan Aerospace Exploration Agency, Japan

Combustion tests for an ethylene fueled scramjet combustor with cavity flameholders used for a flight experiment have been conducted at Ramjet Engine Test Facility(RJTF) of JAXA under Mach 6 flight conditions using two
types of airflows, clean air (M6S) and vitiated air (M6V).
M6V is generated by H2/O2 combustion containing water
vapor, while M6S is generated by a thermal storage heater.
The RJTF results showed pressure rise due to combustion
was lower at M6V in the cavity and downstream diverging
combustor sections compared to M6S. On the other hand,
RANS CFD assuming laminar combustion was not able
to reproduce the difference between the two conditions
obtained from the RJTF tests even if turbulent Schmidt
number and turbulence model were changed. Therefore,
we incorporated a partially stirred reactor (PaSR) model,
which is one of the Turbulence Chemistry Interaction (TCI)
models, into the CFD. Application of this model improved
the agreement with the RJTF results in terms of the wallpressure distributions of the combustor. In this study, we
will focus on the effect of the TCI model on the simulationof scramjet combustor flows and discuss the results indetail.
Contact: kodera.masatoshi@jaxa.jp83Track01 Laminar flames

Track01-1 Laminar flames (1)Chair: Jeroen Van Oijen
Wednesday, May 8; 10:40 - 12:20; Room M

Stabilization of flames in narrow
channels by a highly conductive wallsegment: effect of the Lewis number andapplication to hydrogen-air flames
Carmen Jimenez
CIEMAT, Spain

In this work, we study the effect of the Lewis number inthe stabilization of premixed flames in narrow channels by
a wall segment of finite length with high thermal conductivity and thermal capacity. The thermal conductivity ofthis wall segment is assumed to be so high that the temperature inside it is uniform. First, the auxiliary problemof flame stabilization at a given temperature of a highly
conductive wall segment is considered and the total heat
flux in this segment is calculated. It is shown that the heat
flux becomes zero for certain values of the imposed temperature. These temperature values correspond then to
solutions of the original problem, where the conductive
wall segment is in contact only with the flame and is isolated from the external environment.
We show that for low Lewis number flames, this novel
concept for flame stabilization only by thermal means
provides stable operation for a wide range of values of
the reactants flow rate, giving a large flexibility in terms of
power output variation and exceeding the performancefound in classical heat recirculating devices. We also showthat multiple steady-state flame solutions may appear,
which can complicate the operation of these devices.
Contact: Carmen.jimenez@ciemat.es

Flame stabilization by a highly conductive
cylinder: multiple steady-state solutions
and dynamics
Vadim N. Kurdyumov, Anne Dejoan, Carmen Jiménez

CIEMAT, Spain

This study examines stabilization of a premixed flameby a circular cylinder placed perpendicularly to the uniform flow of the reacting mixture. It is assumed that thecylinder has high thermal conductivity. Its temperature is
not fixed, but it is determined by a thermal flame-cylinderbalance. The numerical investigation is carried out on thebasis of low Mach number Navier-Stokes equations coupled with the conservation equations for the energy andthe fuel mass. Two models for transport coefficients arecompared. The first model assumes they have constantvalues, and the second takes into account their changewith temperature.
Numerical modeling shows that within the specificrange of parameters of this study the system can haveseveral steady-state solutions corresponding to different
cylinder temperatures. Moreover, at least two solutions
are shown to be stable, the two solutions corresponding
to the hottest and coldest cylinder temperatures. The actual occurence of one or another regime depends on theinitial conditions.
Contact: vadim.k@ciemat.es

Effect of the exhaust gases boundary
condition on the stability and propagation
regimes of a premixed flame in a slenderchamberDavid Rodríguez-Gutiérrez1, Raquel Gómez-Miguel1,
Eduardo Fernández-Tarrazo2, Mario Sánchez-Sanz2

Instituto Nacional de Técnica Aeroespacial, Spain, 2Universidad Carlos III
de Madrid, Spain

1

This work presents a numerical analysis of the propagation of laminar premixed flames in slender semi-open
chambers. The study aims to evaluate the influence of theboundary conditions in the combustion process.
For this task, the combustion process is initiated witha local temperature raise close to the open end of thechamber. When activation temperature is reached, a84

19th International Conference on Numerical CombustionTrack01 Laminar flames

self-sustained combustion process begins, forming aflame that propagates along the chamber. Noise introduced into the system during ignition in the form of pressure waves interact and perturb the flame. The growth ofthese perturbations can induce thermos-acoustic oscillations in the flame and even modify the flame propagation
regime.
All these phenomena has been studied using a constant pressure outlet boundary condition, an extensively
used boundary condition for internal flows. However,given the strong non-linear nature of the reactive-flow,
the thermo-acoustics and stability of the freely propagating flame problem, the use of this boundary condition
can compromise the accuracy of the solutions obtained,
as phenomena taking place at the chamber exit is not
resolved: pressure wave reflections, flow entrainment or
pulsating jets.
These overlooked phenomena can have a strong impact in the evolution combustion process itself. To evaluate this impact a domain surrounding the channel is added, accounting for the external atmosphere, being able toaccurately resolve the exhaust low speed jet. A comparison with published constant pressure outlet results is carried out, providing an initial assessment of the impact thechamber exit phenomena has on the combustion process.
Contact: rdguezgd@inta.es

Darrieus-Landau instability in a shear flow
Prabakaran Rajamanickam, Joel Daou
University of Manchester, United Kingdom

The Darrieus-Landau instability of premixed flames
propagating in a narrow Hele-Shaw channel in the presence of a strong shear flow is investigated, incorporating
also the Rayleigh-Taylor and diffusive-thermal instabilities. The shear flow also induces Taylor dispersion which
results in anisotropic diffusion.
To understand how the anisotropy affects flame stability, two cases are considered, namely flame propagationin (1) the streamwise and (2) the spanwise directions. The
analysis is based on a two-dimensional model derived
by asymptotic methods and solved numerically, to characterise the influence of the flow Peclet number Pe, theLewis number Le and the Rayleigh number Ra. Dispersion
curves characterizing the perturbation growth rate arecomputed for selected values of Pe, Le and Ra.
Taylor dispersion is found to suppress the Darrieus-Landau instability and to weaken flame wrinklingwhen the flame propagates in the streamwise direction.
In contrast, for spanwise propagation, the flame is stabilized in Le<1 mixtures, but destabilized when Le>1. For
spanwise propagation, stagnation points and counter-ro-tating vortices are encountered in the flame near the unburnt gas side. It is shown that vorticity can be produced
by a curved flame in a Hele-Shaw channel even without
gravity, and that it remains confined to the flame.
Contact: joel.daou@manchester.ac.uk

Diffusive-thermal instabilities ofpremixed flames in channel flows: 3D
stability investigation and flow-induced
anisotropic diffusion effects

Joel Daou, Prabakaran Rajamanickam, Aiden Kelly, Julien
LandelUniversity of Manchester, United Kingdom

The presentation comprises two studies related to the
diffusional-thermal instabilities of premixed flames:(1) an investigation of the influence of the direction ofa shear flow relative to that of flame propagation in narrow channels and (2) a 3D analysis of the instabilities offlames propagating along the flow direction in channelsof arbitrary width.
The first study compares analytically derived stability
results with simulations involving the Lewis number Le,
the Peclet number Pe, and the angle between the direction of propagation and the flow direction. Cellular instabilities expected when Le < 1 are now found to occur due
to Taylor dispersion in Le >1 mixtures, provided the angle
exceeds 75 degrees.
The second study examines flames in a Poiseuille flow.
The instability is found to be a combination of the traditional diffusive-thermal instability and a recently identified
transition from symmetric to asymmetric flames. Instability regions are identified in the Le-Pe plane. In narrow
channels, it is found that flames are always symmetricwith Taylor dispersion enhancing the cellular instability in
Le < 1 mixtures and suppressing the oscillatory instability
when Le >1. In large-scale channels, both instabilities
persist with stronger propensity for asymmetry when theflow opposes flame propagation and Le<1.
Contact: joel.daou@manchester.ac.uk

85

Track01 Laminar flames

Track01-2 Laminar flames (2)Chair: Ronan Vicquelin
Thursday, May 9; 09:50 - 12:30; Room M

DMD analysis on quasi-steady behaviorsof sporadic flames in counterflow under
low-speed low-Lewis-number conditions
Takaki Akiba, Akira Tsunoda, Youhi Morii, Hishashi
Nakamura, Kaoru Maruta
Tohoku University, JapanThe quasi-steady ball-like flames in counterflow at low
Lewis number was observed in microgravity experiments
and named sporadic flame, and they were also confirmedin three-dimensional numerical simulation with diffusive
thermal model at Lewis number lower than or equal to 0.5.
The DMD (dynamic mode decomposition) analysis wasapplied for the temperature distribution of these sporadic
flames in a quasi-steady state in order to understand theirseemingly chaotic behaviors. The DMD analysis unveiled
three predominant unique modes in the sporadic flames: (I)planar, (II) radial, and (III) circular modes. The decomposedmodes showed two distinct spatial segments; the area
forming sporadic flames near the counterflow axis andthe area splitting and transporting flame pieces at outerpart of the counterflow field. Furthermaore, fast Fouriertransform (FFT) analysis was employed to examine thecharacteristic length scales of these decomposed modes,
specifically the (II) radial and (III) circular structures. FFTanalysis quantified identical characteristic length scales inboth radial and angular directions, indicating a consistentscale across different spatial orientations within these distinct flame structures. This symmetry suggests underlying
principles and essential symmetries governing these chaotic flame dynamics in counterflow fields.
Contact: takaki.akiba.q3@dc.tohoku.ac.jp

Measurement of Laminar Burning
Velocity for pre-mixed fuel air mixtures atelevated temperatures and pressures
Subhashree Sampath

Sastra Deemed University, India

Adding hydrogen to methane improves combustion
efficiency, lowers carbon emissions, and supports a shift
to cleaner and more sustainable energy practices. The
present investigation reports numerical study using ANSYS CHEMKIN PRO software on laminar burning velocity
variation of CH4+H2+air mixtures at elevated temperatures (300 K - 650 K) and pressures (1 - 5 bar). Hydrogen86is blended with methane gas to reduce carbon emission
into the atmosphere, to improve the flammability characteristics and subsequently combustion performance.
The effect of mixture equivalence ratio (0.7 to 1.3) andH2 fraction (10% to 50% by volume) have been reported
at elevated temperatures and pressures using chemical
kinetic models like GRI Mech 3.0 and FFCM -1 and havebeen compared with existing literature data. The obtained
results show that variation of equivalence ratio has a direct effect on the flame speed. It can be observed that as
the dilution ratio of H2 increases there is an increase inflame speed due to the high diffusivity of hydrogen. This
increase is due to faster formation of reaction radicals of
H2, O and OH . When it comes to pressures, it can be noted that there is a decrease in the burning velocity value
with an increase in pressure due to suppression in energyof the species in the reactants that slows down the flame
propagation. Flame speed varies linearly with the temperature ratio due to increase in kinetic energy of moleculesin the combustible mixture.
Contact: subha.sam96@gmail.com

Numerical investigation of effects ofpressure and equivalence ratio on laminarhydrogen flame flashback behavior
Kazuhiro Kinuta, Takatomo Yasuda, Kotaro Yada, Naoki
Sugimura, Ryoichi Kurose
Kyoto University, Japan

These days, a hydrogen-fueled combustor is gathering
attention as a key technology to achieve carbon neutrality. For the development of hydrogen-fueled combustors,
predicting and preventing the occurrence of a flashback
is one of the most challenging issues. However, the flashback behavior is dramatically different depending on theconditions, such as the equivalence ratio, the ambientpressure, and the unburnt gas temperature. Therefore,
further research on flashback under various conditions isrequired for a thorough understanding of the fundamental
properties of flashback behavior. In this study, the effectsof equivalence ratio and ambient pressure on a hydrogen
flame flashback and their interaction are investigated indetail. Two-dimensional numerical simulations of hydrogen-air premixed flame flashback in laminar channel flow
are performed under various equivalence ratios and ambient pressures using a detailed reaction mechanism that
includes 9 chemical species and 19 chemical reactions.
The results show that the equivalence ratio and ambientpressure affect the flashback speed, critical condition of
the flashback occurrence, and formation of the backflow
regions.
Contact: kinuta.kazuhiro.36w@st.kyoto-u.ac.jp

19th International Conference on Numerical CombustionTrack01 Laminar flames

Flashback limits of H2 premixed laminarflames: a numerical investigation basedon the “1+M” multi-component diffusion
model
Alberto Cuoci1, Bertrand Naud2, Manuel Arias-Zugasti3,
Alessio Frassoldati1

Politecnico di Milano, Italy, 2Centre for Energy, Environmental andTechnological Research (CIEMAT), Spain, 3Departamento de Física
Matemática y de Fluidos, Facultad de Ciencias UNED, Spain
1

Molecular diffusion is known to be a key process in
combustion. The estimation of mass diffusion fluxes in
multidimensional simulations including detailed chemistry
is usually carried out using the mixture-averaged model.
On the contrary, because of its high computational cost,
the complete multicomponent formulation has been
mainly used in 1D calculations only (especially when thenumber of chemical species is large) [1].
In this work, we explored a novel multicomponent
diffusion model, referred to as “1+M” formulation [2], able
to ensure accuracy levels similar to the complete formulation at the same cost of mixture-averaged. In particular,
the numerical analyses were focused on the description of
flashback occurring in laminar premixed flames fed withpure H2. More specifically, 3D numerical simulations werecarried out on a multi-hole geometry that emulates perforated burners commonly found in domestic condensing
burners. The simulations, including detailed kinetics andconjugate heat transfer with the burner plate, considereda range of equivalence ratios from 0.50 to 1 and various
hole-to-hole distances for a more comprehensive analysis. The results confirmed the need to adopt advanced
diffusion models for the correct description of flashback
phenomena occurring in H2 flames.
References[1] M. Arias-Zugasti, P-L- Garcia-Ybarra, J.L. Castillo, Combustion and Flame, 163 (2016) 540–556.
[1] Naud B., Córdoba O., Arias-Zugasti M., Combustion and
Flame, 249 (2023) 112599
Contact: alberto.cuoci@polimi.it

Ignition delay based estimation oflaminar burning velocity as the minima
of autoignitive reaction wave speed withunity Lewis number
Youhi Morii, Kaoru Maruta
Tohoku University, Japan

Understanding laminar flames is crucial for comprehending combustion phenomena. The laminar burning
velocity, a key characteristic velocity of these flames, isrecognized as an eigenvalue in the governing equationsof one-dimensional flames. In this study, we present a
novel approach to derive the laminar burning velocity. Our
previously reported theory demonstrated that for a unity
fuel Lewis number, the processes of zero-dimensional
ignition and one-dimensional deflagration are equivalent.
This equivalence is established through a spatio-temporaltransformation, involving normalized temperature and fuelmass fraction, which represents the reaction's progress.
Our theory posits that once a temperature is established,
all related thermodynamic properties within the system
can be determined, since temperature acts as a Legendre transformable function to these properties. Buildingon this, we discovered that the temperature gradient in
one-dimensional deflagration is constrained by the profile
of zero-dimensional ignition. Further, we found that thisgradient is influenced by local velocity, which has an identifiable lower limit. We define this minimum velocity as theminima of autoignitive reaction wave speed. Consequently, this velocity is identified as the laminar burning velocity
for a unity fuel Lewis number.
Contact: morii@edyn.ifs.tohoku.ac.jp

Study on heat losses and flow rate on
premixed hydrogen-air flame shape fromthickness of Hele-Shaw burner
Ziyin Chen1, Pierre Boivin1, Christophe Almarcha2, SongZhao1

M2P2 (CNRS, Centrale Marseille, Aix-Marseille University), France, 2IRPHE(CNRS, Centrale Marseille, Aix-Marseille University), France

1

The ability to accurately simulate flame propagationand predict flame instabilities for different gap sizes andequivalence ratios is crucial for the design of micro-scale
combustion devices. In this work, numerical simulation
based on a combination of the Lattice-Boltzmann methodand detailed chemistry kinetic mechanism is carried out torecover stable premixed hydrogen-air flame front shapeson the thickness of a Hele-Shaw burner. Fundamental 2D
flame shapes between narrow plates are computed bytaking into account heat losses at the walls as well as the87Track01 Laminar flames

flow rate ahead of flame front. Our numerical results successfully reproduce steady flame front shapes observed inexperiments, all exhibiting convex profiles towards freshgases over a wide range of equivalence ratio (from 0.35
to 2.0). The impact of equivalence ratios, gap sizes, heatlosses and flow rate on flame shape symmetry/asymmetry properties have been investigated. Flame fronts tend
to be more asymmetric then symmetric with increasing
equivalence ratio. The range of symmetric flames narrows
with increasing gap size. Additionally, both increases ofheat losses and flow rate would widen the range of symmetric flames, hence it is essential to consider these two
factors for the range of equivalence ratios where the transition from symmetry to asymmetry occurs.
Contact: ziyin.chen@univ-amu.fr

Multi-point optimization for laminarhydrogen flames

Cristopher Lorenzo Morales Ubal, Nijso Beishuizen,
Jeroen van Oijen
Eindhoven University of Technology, Netherlands

Due to the increasing demand for high-efficiency andlow-impact environmental technologies, hydrogen has
become a prominent candidate to replace fossil fuels in
combustion systems due to its lower emissions. However, as environmental regulations have become tighter,
optimized combustion devices are required in order tomeet these requirements. Therefore, this work presents
developments in multi-point optimization for laminarhydrogen burners using the Discrete-Adjoint (DA) design
framework within the multiphysics software suite SU2. The
multi-point optimization is carried out in order to obtaina good balance between minimizing pollutant emissions
and thermal efficiency over a range of equivalence ratios.
The optimization cycle is driven using the open-source
design optimization framework FADO. For combustion
modeling, the flamelet generated manifold (FGM) approach, including preferential diffusion effects, is used.
Using the FGM, the thermochemical properties are stored
in lookup tables as functions of mixture fraction, enthalpy,
and progress variable. For retrieving the information during simulations, artificial neural networks (ANNs) are usedin order to replace the lookup tables and reduce computational requirements. These ANNs are trained using theopen-source platform for machine learning TensorFlow.
Finally, robust geometrical constraints will be shown,which allow to obtain optimized designs while preserving
mesh quality along the DA-design cycle.
Contact: c.l.morales.ubal@tue.nl

88

Numerical Investigation on Flame Spreadover a Thin Circular Duct

Vipin Kumar, Kambam Naresh, Arvind Bharath S R, Amit
Kumar
Indian Institute of Technology Madras Chennai, India

The flame spread over combustible solids, such as
cellulose paper, polymers, woods and textiles, constitutes
a fundamental problem in the field of fire research. In thepresent study, flame spread over commonly encounteredcircular duct geometry is investigated numerically in normal gravity and microgravity environments.
A 2-D axi-symmetric numerical model is developed accounting for char formation to investigate the importantmechanisms that controls the flame spread phenomena
over circular duct geometry. In the present model themass, momentum and energy conservation equations in
gas phase are solved along with one-step, second orderglobal gas phase reaction between fuel vapor and oxygen.
In solid phase first order Arrhenius pyrolysis model is considered and mass and energy equation are solved in flame
fixed coordinate system.
In the numerical investigation, it is found that radiation
feedback from the char at inner core region of duct plays
an important role on flame spread rate. Also, as the fuelradius increases the flame spread rate increases in thematrix of study.
Contact: vipinsrivastava2010@gmail.com

Track01-3 Laminar flames (3)Chair: Youhi Morii
Friday, May 10; 09:50 - 11:50; Room M

Effect of confinement on the propagation
patterns of lean hydrogen-air flamesAnne Dejoan1, Zhenghong Zhou2, Daniel FernandezGalisteo1, Paul David Ronney2, Vadim N. Kurdyumov1

Centro de Investigaciones Energeticas, Mediambientales y Tecnologicas,
Spain, 2University of Southern California, United States
1

The effect of confinement on the propagation of leanhydrogen-air flames in a Hele-Shaw cell formed by twoparallel plates separated by a small distance is studied
numerically. Flame propagation is modeled using a quasi-three-dimensional (quasi-3D) approximation, where
the momentum conservation equation is asymptoticallyreduced to Darcy’s law. Chemistry is described by a onestep reduced kinetics with a simple model for transport
properties. To assess the influence of momentum loss,
comparisons are made with results obtained in an un-

19th International Conference on Numerical CombustionTrack01 Laminar flamesconfined geometry corresponding to a purely two-dimensional (2D) domain. Heat losses to the wall plates are also
considered. The results demonstrate that momentum loss
mainly increases the flame surface area by elongating thecellular structures in a finger-like form, with a relatively
small enhancement of the reactivity at the flame front,
consistent with a mechanism of hydrodynamic nature.
This elongation leads to approximately a 50% increasein flame speed compared to the absence of confinement.
Conversely, heat losses are observed to flatten the largescale flame front and, if sufficiently large, can lead to theformation of isolated propagating two-headed flame cells
or, ultimately, one-headed flame cells. The present results
are well-aligned with recent experimental results.
Contact: d.galisteo@ciemat.es

Effect of Taylor dispersion on triple flame
propagation
Shumeng Xie1, Joel Daou2, Prabakaran Rajamanickam2,
Zheng Chen1
1

Peking University, China, 2University of Manchester, United Kingdom

Triple flames have been observed in non-premixed
micro-combustion experiments, accompanying e.g. theformation of so-called diffusion-flame streets. In thepresent work, we identify the effect of Taylor dispersion
or shear-enhanced diffusion on the propagation of such
triple flames.
The study is carried out numerically within the thermo-diffusive approximation of constant density and transport properties and is based on a two-dimensional model
derived asymptotically by depth-averaging the governing
equations in a Hele-Shaw type configuration. The propagation speed of the triple flame, positive or negative, andits existence domain are determined in terms of three parameters, namely the Damköhler number, the fuel Lewis
number and the Peclet number, with the latter quantifying
the strength of Taylor dispersion.
It is found that Taylor dispersion significantly affects
the propagation and existence domain of the triple flame,
both directly through diffusion enhancement which thickens the flame leading-edge and modifies its curvature,and indirectly e.g. through the instability of the underlying
diffusion-flame tail of the triple flame observed above critical values of the Lewis and Peclet numbers. In addition
to the propagating and retreating triple flames, additional
solutions are identified depending on the Lewis and Peclet
numbers, including periodic flame arrays, and slowly-drifting isolated burning structures.
Contact: joel.daou@manchester.ac.uk

Thermal Radiation Effects in Spherical
Flame Simulations of Steam-diluted
Hydrogen-Air Mixtures
Julie Ben Zenou, Ronan Vicquelin

Université Paris-Saclay, CNRS, CentraleSupélec, Laboratoire EM2C, FranceThis study investigates the effect of thermal radiation
on steam-diluted hydrogen-air flames. Steam dilution reduces flashback risks, temperature, and NOx emissions.
These mixtures also impact nuclear safety, potentiallyarising in reactor cooling system breaches.
Prior studies using 1D simulations showed radiation(emission and reabsorption) significantly alters the laminarburning velocity (with observed accelerations exceeding
50% in realistic lean conditions). However, these models
fall short in replicating experiments due to oversimplified
geometry.
This research therefore shifts to 3D spherical flames,
commonly used to measure laminar burning velocities
experimentally. The goal is to match experimental resultsfrom a constant pressure spherical chamber using Direct
Numerical Simulation coupled with a Monte Carlo radiation solver. This approach involves a two-way coupling
between two 3D finite volume solvers. The combustion
solver provides the temperature and composition, while
the radiative solver returns the radiative power field. Special attention is paid to the compatibility of the different
meshes and the adjustment of the coupling period toachieve the required accuracy. The aim is to accurately
quantify radiation's impact and assess the precision of adiabatic fit models in predicting unstretched laminar burning velocities in lean and very lean hydrogen-air flames
diluted with steam.
Contact: julie.benzenou@centralesupelec.fr

Propagation and self-acceleration of
circular expanding hydrogen/air flames at
cryogenic temperature
Linlin Yang, Zheng Chen
Peking University, China

Hydrogen plays an important role in reducing carbon
dioxide emission. The widespread use of hydrogen raises
concerns on safety issues such as fires and explosions
related to cryo-compressed hydrogen. Therefore, it isnecessary to understand the combustion properties ofhydrogen at cryogenic temperatures. In this study, we
conduct two-dimensional simulations of circular expanding hydrogen/air flame in an open space and investigate
the flame morphology evolution and self-acceleration
process. Stoichiometric hydrogen/air mixtures with89

Track01 Laminar flamesnear-unity Lewis number at cryogenic temperature (100K) and normal temperature (300 K) are considered sothat the flame propagation is mainly affected by theDarrieus-Landau instability (DLI) instead of the diffusional-thermal instability (DTI). Since the thermal expansion
increases greatly with the decrease in the initial temperature, the DLI at cryogenic temperature becomes muchstronger than that at normal temperature, which results insignificant increase in flame propagation speed, total heatrelease rate, acceleration exponent as well as violent cell
evolution including cell growth, splitting and merging. The
stronger DLI at lower initial temperature leads to larger
cell number, smaller mean cell size and longer mean cell
depth. Analysis on cell statistics shows that the intermittent characteristics of flame propagation speed is mainly
caused by cell evolution. Interestingly, the peak value offlame propagation speed at cryogenic temperature canexceed that at normal temperature. The heat release rate
and flame propagation speed at cryogenic temperature
can be comparable to those at normal temperature. Suchcounterintuitive observation provides useful insights tofire safety control of cryogenic hydrogen utilization.
Contact: yangll@pku.edu.cn

Numerical studies on the propagationof ultra-lean hydrogen/air flames in anarrow gap
Linlin Yang, Zheng Chen
Peking University, China

Understanding the propagation of ultra-lean hydrogen
flame is important for hydrogen safety control. In thisstudy, we conduct 3D numerical simulations on ultra-leanpremixed hydrogen/air flame propagation in an open
Hele-Shaw cells with conductive heat loss. By changing
the wavenumber of perturbation imposed on the circular
ignition kernel, effects of ignition kernel shape on flame
cell propagation are studied. It is found that the ignition
kernel shape significantly affects the flame cell evolution.
When no perturbation is imposed on the circular ignition
kernel, the smooth flame front splits into two isolatedball-like flame cells. These two flame cells propagate outwardly in one-headed finger regime. When the sinusoidal
perturbation is imposed, flame front splits twice and forms
four flame cells propagating outwardly in different flame
regimes including one-headed finger and two-headed
finger. The number of isolated flame cells is not sensitive
to perturbation wavenumber. However, the distributionof flame cells as well as the interaction between adjacentcells is greatly affected by the perturbation wavenumber
since it affects the isolated flame cells formation. Moreover, due to heat loss and counteraction of flame enhance-90ment by positive stretch rate, the flame cell experiences
periodic expanding and shrinking during its evolution.
Furthermore, different flame cells tend to evolve into thesame final state and the distance before reaching the final
state is small when the isolated flame cell is far from adjacent cells. The present results help to understand the different regimes of ultra-lean hydrogen flame propagation.
Contact: yangll@pku.edu.cn

The propagation mechanism of laminar,
premixed DME/air flames

Mohammad I Radaideh1, Dimitrios C Kyritsis2, Dimitris A
Goussis2
University of Michigan, United States, 2Khalifa University, United ArabEmirates

1

Dimethyl ether (CH3OCH3 or DME) is a bio-fuel thatcan be produced from renewable sources; e.g., liquefaction of biogas generated from fermentation processes.
With the context of exploring its combustion characteristics, the propagation mechanism of DME/air steady, laminar, premixed flames is analyzed, using the tools of Computational Singular Perturbation (CSP). It is shown that thismechanism is encapsulated by an explosive mode, when it
acts in a narrow region that includes the point where themaximum heat release rate (MHRR) occurs. The intense
chemical activity downstream of MHRR generates heatand radicals that diffuse upstream, initiating chemical
activity there that is sustained by the convective motionof DME and O2. The reaction contributing the most to
the propagation mechanism is H+O2->OH+O, followedby other reactions that generate the radicals O, H andOH that are reactants of the most exothermic reactions(e.g., CH3+O->CH2O+H, CH2O+H->HCO+H, CH2O+OH->HCO+H2O). The species with the most impactful upstream
diffusion is H, followed by OH and O that support theaction of the explosive mode and of H2 that opposes it.
The explosive mode is not everywhere meaningful; e.g.,
upstream of the flame, where transport dominates.
The proposed methodology carries out in an algorithmic manner the paper-and-pencil asymptotic analysis,
introduced in the 80s by N. Peters, F.A. Williams and otherresearchers. However, being algorithmic, the CSP methodology is not hindered by the size of the kinetics mechanism or the complexity of the reacting configuration
employed.
Contact: dimitris.goussis@ku.ac.ae

19th International Conference on Numerical CombustionTrack01 Laminar flames

Track01-4 Laminar flames (4)Chair: Ekenechukwu Chijioke Okafor
Friday, May 10; 13:00 - 15:00; Room M

Effect of Ozone Addition on Extinction
limits of Hydrogen/Ammonia-Air
Premixed Counterflow Flames
Krishnakant Agrawal1, Mayank Pandey2

Indian Institute of Technology (IIT) Delhi , India, 2Indian Institute ofTechnology (IIT) Delhi, India

1

Effects of Ozone addition on enhanced reactivity leading to increased flame speed, ignition limits and achieving
cool flames has been reported in literature. However,studies on the impact on flame extinction limits in case ofstrained flames are relatively scarce. Extinction resistanceof flame due to stretch is an important property for understanding combustion behaviour in turbulent flows as well
as for chemistry tabulation. The present study investigates
the effects of ozone addition on the extinction of strainedhydrogen/oxygen/nitrogen and ammonia/oxygen/nitrogen flames, emphasising change flame structure due tothe chemical kinetics of ozone. A twin premixed flame,
symmetrical about stagnation plane and a single premixed
flame opposing inert nitrogen are studied computationallyusing the counterflow flame configuration. The additionof ozone in oxidizer further promotes the reactions bygenerating the radical pool of O, OH, HNO, NO, etc. especially for lean mixtures, which show significantly higher
extinction stain rates (ESR) than those without ozone.
This is predominantly due to the additional ozone layer inthe preheat zone also manifesting as dual peaks in heatrelease rate profile. However, the ozone addition has alimited effect on rich mixtures. In the case of ammonia,
although HNO production is significant on the rich side,
limited O, OH, and NO radicals suppress the further chain
branching through NH2, NH, etc. The flames with different
burner separation distances (BSD) are also studied to further the understanding of apparatus independent ESR and
its use in the validation of kinetic models.
Contact: kkant@mech.iitd.ac.in

Optimized Progress variable for methanehydrogen flames
Fatemeh Chitgarha1, fathollah ommi1, Amir Mardani2

Tarbiat Modares university, Iran, Islamic Republic of, 2Sharif university oftechnology, Iran, Islamic Republic of

1

In the context of gas turbines, the turbulent burning
speed is strongly influenced by the laminar burning speed,which is directly tied to the type of fuel being used. Whena portion of methane fuel is replaced with hydrogen, it hasa significant impact on the chemical processes involved.
This not only affects the rate at which fuel is consumed
but also has implications for flame stability, potentiallyleading to higher integral fuel consumption rates. Whenconsidering a non-unity Lewis number for fuels that
include hydrogen, there are localized variations in the
distribution of species and temperature. These localizedchanges have an effect on the local consumption rate offuel, which can result in an unstable flame. To study thisphenomenon, the flamelet model is employed, which represents flames as a collection of one-dimensional laminarflames. , and a genetic algorithm is used to optimize theprogress variable by minimizing non-monotonicity terms
and the gradient of species concentrations.
By constructing flamelet tables with a non-unity Lewis number and introducing hydrogen into methane fuel,different progress variables are compared. The findings
highlight the significant influence of certain chemical species on the progress variable and demonstrate the sensitivity of the defined cost function to the selected species,
particularly when there is an increase in the amount ofhydrogen in the fuel. It is crucial to include CO in the progress variable definition to accurately represent the combustion process.
Contact: chitgarha.mech@gmail.com

Estimating Soot Formation/Oxidation
Rates using Explainable Machine Learning
Andisheh Khanehzar, Seth Dworkin
Toronto Metropolitan University, Canada

Soot, the second most significant contributor to climate change following CO2, has detrimental effects
on the environment and human health. Understanding
soot formation and oxidation is crucial for mitigating theenvironmental impacts of hydrocarbon combustion. Numerical modeling of soot formation requires considerable
computational resources and time due to its dependence
on numerous physical and chemical processes, entailingthe integration of thermodynamics, heat transfer, chemical kinetics, particle dynamics, and fluid dynamics. A key
goal of the combustion industries is to develop accurate
and computationally inexpensive approaches for obtaining soot properties. This study investigates the applicationof Explainable Machine Learning (XML) to estimate sootformation/oxidation rates by employing the histories ofcorrelated gas-related variables, such as temperature,
mixture fraction, and species concentrations. The current
work finds the complex relation between input featuresand soot formation/oxidation rates and provides transpar-91

Track01 Laminar flamesent insights into the ML algorithm's decision-making process. The approach aids in gaining a deeper understanding of the physical aspects involved in soot formation withlower computational costs compared to CFD simulations.
Prediction accuracy is tested over two segregated flames,
having an R2 value of approximately 0.87.
Contact: andisheh.khanehzar@torontomu.ca

Numerical Study of Co-combustion
Characteristics of Ammonia and CokeOven Gas

ZongYu Pan1, Ta-Hui Lin2, Fang-Hsien Wu1, Guan-Bang
Chen1

National Cheng Kung University, Taiwan, 2National Chen Kung University,
Taiwan1This study numerically investigates the co-combustionof ammonia with coke oven gas (COG) that is produced
during the manufacture of metallurgical coke. Chemkin-Pro 2020 R1 software with a detailed chemical mechanism is used to predict adiabatic, freely propagating laminar burning velocities for NH3/COG combustion. Ammonia
is a new type of carbon-free fuel and has the advantage
of easy transport. However, ammonia combustion has
some defects, such as a high ignition temperature, lowflame temperature, slow flame speed, and narrow rangeof flammability. COG, abundant in hydrogen, possesses
a substantial energy content and can effectively address
the limitations associated with ammonia combustion.
Co-combustion strategy synergizes the advantages ofboth fuels, aiming to maximize their potential and achievecarbon reduction benefits. By delving into the fundamental flame properties and pollution emission characteristics,
a detailed analysis will be performed for the combustion
kinetics and thermodynamics of the co-combustion system. Furthermore, the study will also explore combustion
characteristics of NH3/COG-air premixed flames including
adiabatic flame temperature, flame velocity, flame structure, and species distribution. The results will contribute to
the development of a novel combustion technology withpotential environmental benefits, simultaneously improving the utilization efficiency of both ammonia and COG.
Contact: n16114275@gs.ncku.edu.tw

Numerical Study on Hydrogen Peroxide
Effect on Syngas/Air Premixed
Combustion

Annas Fauzy, Guan-Bang Chen, Fang-Hsien Wu, Ta-Hui
Lin
1

National Cheng Kung University, Taiwan

Synthetic gas (syngas), derived from biomass gasification, is a promising fuel source and is mainly composedof hydrogen and carbon monoxide. However, syngas is
usually categorized as a low-caloric fuel that needs to beenhanced for various combustion applications. Typically,
syngas combustion can be enhanced by adding a strongoxidant, such as hydrogen peroxide. Hydrogen peroxide(H2O2) is a strong oxidizer that yields oxygen, steam, andappreciable heat after decomposition. Adding hydrogen
peroxide to syngas combustion can significantly enhance
the potential of syngas through chemical modifications.
Different roles of H2O2 in syngas/air combustion can beleveraged to realize its advantages. These roles include
treating H2O2 as a fuel addition, an oxidizer addition,
and an oxygen replacement in air. This study numericallyinvestigates the effects of H2O2 on syngas/air-premixed
combustion by varying the H2O2 addition method using
the CANTERA package combined with a detailed chemicalmechanism. The adiabatic flame temperature, laminarburning velocity, flame structures, and some major species evolution for one-dimensional simulation are discussed under different simulation conditions. The results
will contribute to the development of syngas as a promising fuel with potential environmental benefits, simultaneously improving the utilization efficiency.
Contact: n18087050@gs.ncku.edu.tw

Track01-5 Laminar flames (5)Chair: TBD
Friday, May 10; 15:20 - 17:20; Room M

Regimes of autoignitive stretched flame
bounded by “Explosive transition of
deflagration” and spontaneous ignition
front
Akira Tsunoda, Youhi Morii, Kaoru Maruta
Institute of Fluid Science, Tohoku University, JapanTo enhance thermal efficiency and lower emissions,advanced engine technologies like HCCI are gaining focus.
These operate in extreme conditions like high temperature and pressure, posing challenges such as knocking.
Traditional laminar deflagration theory, which separates

92



19th International Conference on Numerical CombustionTrack01 Laminar flames

deflagration into preheat and reaction zones, does not
fully explain these phenomena. This study examines
deflagration limits at elevated temperatures, introducing
concepts of "Explosive transition of deflagration" theory,the limit of deflagration with Lewis number greater thanunity (Le > 1) caused by chemical reactions in the preheatzone, and "spontaneous ignition front", represented by
the characteristic speed in temperature-inhomogeneous
mixtures proposed by Zel'dovich. The study confirmed
equivalency between 0D ignition and 1D counterflow
flame (stretched flame) with Le = 1, applying this tonumerical simulations of 1D stretch-free and stretched
flames for Le > 1. 1D stretched flames showed three reaction front regimes with increasing mixture temperature:(I) conventional deflagration, (II) deflagration affected byspontaneous ignition in the preheat zone, and (III) spontaneous ignition front. "Explosive transition of deflagration" of 1D stretch-free flame was observed in the vicinityof the boundary between the regimes (I) and (II). Regime(III)'s phenomena aligned with Zel'dovich's spontaneous
ignition front theory.
Contact: akira.tsunoda.s5@dc.tohoku.ac.jp

Evaluation of Soret Diffusion Models for
Hydrogen Combustion
Thorsten Zirwes, Andreas Kronenburg
University of Stuttgart, Germany

Hydrogen is becoming increasingly important as a
zero-carbon fuel. However, hydrogen is characterized bystrong differential diffusion effects due to its high diffusivity. This not only affects Fickian diffusion (non-unity
Lewis number effects), but an additional mass flux due tothermodiffusion (Soret effect) becomes important as well.
The most accurate approach currently is to compute thermodiffusion coefficients from the multi-component diffusion model. However, the computational cost for the multi-component diffusion model is prohibitively large when
performing full 3D simulations of hydrogen flames. In thiswork, we implemented five different approximate diffusion
models from the literature and directly compared themto the multi-component diffusion model. These include
models available in commercial codes like Fluent andChemkin, in-house codes and the literature. The model by
Warnatz et al. yields the best results for thermodiffusion
coefficients of the light species H and H2, but predictionof heavier species shows significant differences. Overall,
the model by Chapman and Cowling performs the best,
while other commonly used models show large discrepancies to the multi-component reference values. The bestmodel is then used to perform a full 3D simulation of athermodiffusively unstable hydrogen flame to study theformation of cellular structures.
Contact: thorsten.zirwes@itv.uni-stuttgart.de

Numerical investigation of a water
droplet interacting with an hydrogen/air
counterflow flame
Maria Rosaria Acquaviva, Biagio Cassese, Alessandro
Porcarelli, Ivan Langella
Delft University of Technology, Netherlands

The mutual interaction between a single water droplet
and a strained laminar premixed hydrogen-air flame isnumerically investigated in this work. The topic is relevant
because the injection of water droplets is emerging as
a possible solution to lower NOx emissions in premixed
combustion systems. Indeed, the water vapor locatedclose to the flame absorbs heat with a consequent reduction of temperature, thermal NOx, and the possible
control of temperature fluctuations. However, for commonhydrocarbon fuels the process of water droplet evaporation near the flame might lead to local extinction withconsequent increasing of CO emissions. Conversely, thestrong reactivity of hydrogen can prevent the occurrenceof local extinction when the injected droplets reach theflame front, which makes water injection very attractive
for hydrogen flames. Together with this, the vapour cloudforming around the droplets during the evaporation process might induce a local wrinkling of the flame front withconsequently local curvature effects which are particularly important in lean hydrogen flames due to the highdiffusivity of hydrogen. These effects are studied in thiswork by means of two dimensional detailed chemistry
simulations, specifically focusing on the local interaction
between strain and the local curvature induced by the
droplet-flame interaction.
Contact: m.r.acquaviva@tudelft.nl

Nozzle Angle Effect on Premixed Conical
Flame-Flickering Characteristics

Chenghao Qian, Gaofeng Wang, Haroun Hassan, Keqi Hu
Zhejiang University, China

Experimental and numerical simulation methods were
utilized to investigate the impact of nozzle angle on thecharacteristics of premixed conical flame flickering. This
study specifically examined a typical premixed conicalflame (Bunsen flame) across a range of nozzle directions
from 0° to 180°. A notable aspect of this research is thecomprehensive collection of flame flickering frequency
data obtained through heat release signal experiments.

93Track01 Laminar flames

While the flickering frequencies exhibit a consistent influence from equivalence ratio and Reynolds number, theirdistribution varies across different nozzle angles. The
research also presents a novel empirical correlation forgeneral nozzle angles based on the collected data. To
provide clearer insights into flame behavior under varying
nozzle angles, velocity fields were visualized using Particle
Image Velocimetry (PIV) experiments and Direct Numerical Simulation (DNS). The results indicate that the nozzle
angle not only alters downstream shear strength but also
affects general flame flickering and vortex shedding motions.
Contact: chenghao_q@zju.edu.cn

Three-dimensional simulations of ultralean hydrogen-air flames in narrow gaps
Ruben Palomeque-Santiago1, Anne Dejoan2, Daniel
Fernandez-Galisteo3, Mario Sánchez-Sanz1

Universidad Carlos III de Madrid, Spain, 2Centro de Investigaciones
Energéticas, Medioambientales y Tecnológicas, Spain, 3Centro deInvestigaciones Energeticas, Mediambientales y Tecnologicas, Spain

1

Motivated by recent experimental evidence demonstrating the stationary propagation of isolated flame
cells in ultra-lean mixtures containing hydrogen andair between two parallel plates, this work conducts athree-dimensional study to numerically explore the transition between the double-cell and the circular flame
solution in relation to the equivalence ratio. The chemistry
is described by a one-step reduced kinetics, previously
developed for hydrogen-air deflagration, along with asimple model for the transport properties. The separation
distance between the plates is fixed at 4 mm. Additionally,
the impact of heat loss through the walls on the development of each flame solution is examined. The simulations
reveal propagation velocities and sizes of isolated flame
cell solutions consistent with the experimental observations.

portunity to develop portable power devices, which can beapplied on micro unmanned aerial vehicles, micro-satellite
thrusters, or micro chemical reactors and sensors This
work studies numerically micro-combustion to design micro-propulsion, which can be applied on micro unmanned
aerial vehicles or CubeSat. For these numerical studies we
use a numerical framework for the numerical modeling oflaminar flows with homogeneous reactions and analyze
heat transfer within the solid walls of the microchannel
using the Conjugate Heat Transfer method. The implementation was fully validated with numerical and experimental studies.
In this work, we conduct a numerical study of flame
dynamics in complex geometries, exploring the impact ofvarious materials commonly used in aerospace applications on propulsion. By adjusting input parameters andoperational conditions, we aim to understand how different materials affect the design and performance of the
micro-burner systems. We examine five material groups,
including adiabatic materials, ceramics (LTCC and HTCC),
metals (two stainless steels), amorphous materials (twohigh-temperature glasses), and high thermal conductivity
materials (silicon, aluminum, and copper-tungsten alloys).
A new type of flame dynamics for Hydrogen/air combustion were observed, named Pulsatory Flame Burst(PFB) [1-6]. The phenomenon known as Pulsatory Flame
Burst (PFB) is a specific flame behavior characterized byburst-like flame pulsation due to flow and combustion
interactions. As of currently, PFB only occurs in undulatinggeometries with premixed hydrogen and air, and the flame
bursts involve the ignition, propagation, bifurcation (splitting), and extinction of the flame in a cyclic manner. Thisnew type of flame dynamics can be explored to design
new efficient and compact green energy burner due to theextended limit for flammability introduced by the interplay
between fluid dynamics and combustion, particularly due
to the vortices generated on the nonlinear geometry of
the burner.
Contact: aafonso@fe.up.pt

Contact: d.galisteo@ciemat.es

Numerical Investigation of microcombustion flame dynamics on wavy
systems: materials and performance
analysisDavid D. Dias1, Pedro Resende2, Alexandre M. Afonso3
1

CEFT / FEUP, Portugal, 2MorPheus / IPVC, Portugal, 3CEFT / FEUP, Portugal

The increasing demand on combustion based micro-power generation systems, mainly due to the highenergy density of hydrocarbon fuels, created a great op-94



19th International Conference on Numerical CombustionTrack02 Kinetics, mechanism reduction

Track02-1 Kinetics, mechanism
reduction (1)Chair: Maria U. Alzueta
Wednesday, May 8; 15:30 - 17:10; Room K

Deep mechanism reduction (DeePMR)
method for fuel chemical kinetics
Tianhan Zhang

Southern University of Science and Technology, China

Fuel chemistry represents a typical complex system involving thousands of intermediate species and elementary
reactions. Traditional mechanism reduction methods, suchas sensitivity analysis and graph-based approaches, failto explore global correlations of the sub-systems, thereby
compromising their efficiency and accuracy. A novel machine learning-based approach called deep mechanism
reduction (DeePMR) has been developed to address thisissue. The current method transforms mechanism reduction into an optimization problem in the combinatorial
space of chemical species while mitigating the curse ofdimensionality inherent in the high-dimensional space. We
propose an iterative sampling-training-predicting strategy
combining deep neural networks with genetic algorithms
to learn the landscape of the combinatorial space andlocate the targeted subspace. Applying DeePMR to fuelchemistry mechanisms has led to much more compact
mechanisms than traditional methods, including directed
relation graph (DRG) or path flux analysis (PFA) methods,
with three to four orders of magnitude acceleration innumerical simulation. In addition, reduced mechanisms
by DeePMR indicate a principal-satellite formulation for
constructing chemical reaction mechanisms, providing
a straightforward yet effective alternative to hierarchy-based construction methods. The DeePMR method
provides a general framework for model reduction acrossvarious fields.

An open-source toolbox for chemical
kinetic mechanism’s optimization

Adnan Tolga Kurumus, Atmadeep Bhattacharya, Parsa
Tamadonfar, Ossi Kaario
Aalto University, Finland

In the field of chemical kinetics, optimizing kinetic
mechanisms is highly important for more accurate simulations and predictions. This study introduces a noveland open-source toolbox based on JAYA optimization algorithm. JAYA has already proven its capabilities in manyengineering problems, and in this study, it is utilized forthe first time in the field of chemical kinetic mechanism
optimization. The toolbox uses Cantera for solving chemistry related computations, ensuring robust and reliable
results. A notable feature of this toolbox is its user-friendly Graphical User Interface (GUI), developed in a Python
environment. This GUI simplifies the optimization process
and, with its open-source nature, is accessible to a wider
range of users. It enables users to conduct sensitivity
analysis and define the uncertainty ranges of Arrhenius
rates, which are crucial for fine-tuning mechanisms. The
toolbox is capable of optimizing three combustion parameters such as ignition delay times, laminar burning velocities, and jet-stirred reactor mole fractions. Additionally,by using "multiprocessing" library, each data point can beevaluated on different processors, which helps in reducing
the overall computational time. After numerous test runs,
the results have been satisfactory, demonstrating thetoolbox’s capability to effectively and accurately optimize
chemical kinetic mechanisms.
Contact: adnan.kurumus@aalto.fi

Combined chemical reaction network andtime scale analyses for reduced models of
combustion of complex fuels
Viatcheslav Bykov1, Vladimir Goldshtein2

Karlsruher Institut für Technologie, Germany, 2Ben-Gurion University of
the Negev, Israel

1

Contact: zhangth@sustech.edu.cn

Chemical reaction networks (CRNs) of combustion systems based on mass action laws and Arrhenius reaction
rates of elementary reactions remain the primary sources
for complexity of the combustion models. A number of95Track02 Kinetics, mechanism reduction

variables / species and parameters used as well as stiffness of models complicates significantly the computational treatment considerably. This becomes even morecrucial once a mixture of different fuels is considered.
In this work, we use a combination of time scale, invariant manifolds and chemical reaction network analyses
to study ignition delay times of combustion systems ofcomplex fuels. The blends of hydrogen, methane mixed
with ammonia as combustible systems are considered.
Rigorous time scale analysis of detailed model and study
the CRN properties, while varying the composition, identifies the rate limiting and coupled sub-networks controllingthe ignition delay times and describing the course of
combustion system dynamics. As a results key reactions
controlling the progress and constraining the states are
identified, which can be used to both improve the detailed
models as well as to reduce detailed chemical reaction
models.
Contact: viatcheslav.bykov@kit.edu

Minimizing Reduced Mechanism Costs via
Bounded Reaction Rate Optimization andTargeted Reaction State Sampling forEngineering Applications
Adam L. Comer1, Joshua P. Sykes2, Brent A. Rankin2

Innovative Scientific Solutions, Inc., United States, 2Air Force ResearchLaboratory, United States

1

Finite rate chemistry is a computationally expensive
component of many numerical simulations of combustion
applications. With significantly lower computational costcompared to detailed chemical mechanisms, reduced
mechanisms employing the quasi-steady state approximation (QSSA) typically reproduce key combustion responses with high accuracy. However, simulation costs with reduced mechanisms are still significantly higher than thosewith global mechanisms. To lower costs while maintaining
accuracy sufficient for engineering applications, two ideas
are considered: 1) optimization of reaction rates within
uncertainty bounds and 2) reduction at targeted sets ofconditions corresponding to a single combustor operating point. Reduction costs are low relative to numericalsimulations of applications, so a unique mechanism canbe created for each operating point with minimal impact
on computational budgets. Recently presented work on
novel skeletal mechanisms derived from this approachdemonstrates cost-savings that range from marginal to
50% relative to skeletal mechanisms in the literature, andin cases where cost-savings are marginal, order of magnitude reductions in ignition delay errors are observed.
In this presentation, the QSSA is applied to these novel
skeletal mechanisms to yield novel reduced mechanisms;

96

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cost and accuracy improvements are then considered relative to existing reduced mechanisms. Cost assessments
include comparisons of chemical timescale estimates andassociated time step restrictions for numerical simulationof applications.
Contact: Adam.L.Comer@gmail.com

NH3/DME oxidation at different pressures
Adrián Ruiz-Gutierrez, Paloma Rebollo, Pedro García-Ruiz,
María U. Alzueta
University of Zaragoza, Spain

The present study deals with the conversion of NH3/
DME mixtures in tubular flow reactor setups at differentpressures, ranging from atmospheric to 40 bar. The experimental work includes variation of temperature (500-1425K), O2 excess ratio (λ= 0-3), NH3/DME ratio (0.5-10) andpressure (up to 40 bar). Additionally, the influence of the
impact of the presence of NO has also been considered at
atmospheric pressure. The results show that the presenceof DME affects the oxidation behavior of NH3, displacing
its oxidation at low temperatures. This effect increases as
DME concentration increases. O2 availability and pressure
influence significantly the conversion of both componentsof the mixture, shifting it to lower temperatures as O2
excess ratio and pressure increase. Similar effect is produced by the presence of NO, except for DME oxidation,
which is only enhanced under fuel-lean conditions in thepresence of NO. Pressure also acts to increase N2O production. Simulation of the experimental results has been
done using different mechanisms and results indicate thatvarying pressure implies significant differences in both experimental results and reaction pathways.
Contact: uxue@unizar.e

19th International Conference on Numerical CombustionTrack02 Kinetics, mechanism reduction

Track02-2 Kinetics, mechanism
reduction (2)Chair: TBD
Friday, May 10; 09:50 - 11:50; Room E

Development of a Kinetic Mechanism
for Ammonia blended Combustion
Applications in CI Engines and Gas
Turbines

Sayak Banerjee, Raja Banerjee, Dinesh Prabhakaran
Indian Institute of Technology Hyderabad, India

Ammonia (NH3) is considered a promising carrier ofrenewable hydrogen and a zero-carbon fuel. Despite its
many advantages, ammonia does suffer from poorer
combustion characteristics compared to traditional hydrocarbons like lower flame speeds, high ignition delay
times and high NOx formation propensity. Hence ammonia must be used in blended form with other traditional
fuel molecules like Methane, Kerosene and Diesel in dual
fuel CI engines or Gas Turbine applications, at least at theinitial stages. The current work is aimed at constructing
a semi-detailed ammonia – methane – hydrogen – n-dodecane mechanism consisting of 242 species and 1769
reactions including both nitrogen oxides (NOx) and sootsub-mechanisms to investigate the combustion and emission characteristics of potential blends of ammonia withtraditional fuels in emerging gas turbine and CI engine
systems. The ignition delay and laminar flame propertiesof the fuels and their blends have been predicted using
this mechanism and validated extensively with numericalor experimental data available in the literature. Some initial combustion and emission characteristics of promising
blends are also discussed.
Contact: sayakb@mae.iith.ac.in

A skeletal chemical kinetic mechanism forammonia-kerosene oxidation in air
Vijrumbana Yempally, Vanteru Mahendra Reddy
Indian Institute of Technology Kharagpur, India

The immediate transition of kerosene-based gas turbine engines towards sustainable energy generation canbe achieved through the adoption of ammonia-kerosene
blends combustion. In addition, the slow combustion kinetics of ammonia can be addressed by burning it withhigher reactivity fuels like kerosene. It is essential todevelop ammonia-kerosene mechanisms to grasp the impact of adding ammonia on the combustion characteris-tics and emission features of kerosene-based fuels. In thepresent work, ammonia-kerosene skeletal chemical kinetic
mechanism is developed using the decoupling methodology to avoid conflicts in rate constants for identical reactions while merging mechanisms. The present mechanism
includes four subsets: ammonia subset, kerosene subset,
O2/H2 subset, C1/NOX/NHi subset. The ammonia subset
with N/O/H reactions is taken from Okafor mechanism
meant for NH3/CH4 oxidation in air. The kerosene subset
with C/O/H reactions along with the O2/H2 subset is taken from Zettervall mechanism meant for Jet A-1 oxidationin air. The C1/NOX/NHi subset is adopted from Okafor
mechanism as coupling reactions between nitrogen andcarbon primarily rely on interactions involving small radicals in high-temperature chemistry. The reaction rate
constants of different subsets are updated from several
mechanisms from the literature based on flame speed
and OH sensitivity analyses. The newly proposed mechanism demonstrated close validation of laminar burning
velocity and ignition delay values with the experimental
data at different pressures, temperatures, and equivalence
ratios for neat fuels owing to the lack of data related tothe blends.
Contact: vijrumbhana@gmail.coms

Developing an Ionic Mechanism for
Numerical Modeling of Ion Currents inAmmonia-Air Flames
Dhaminda Hewavitarane1, Sadami Yoshiyama1,
Ryo Kudo1, Boseok Jeong1, Mitsuhiro Izumi2, Tsutomu
Kusuhara2

The University of Kitakyushu, Japan, 2Diamond & Zebra Electric Mfg. Co.
Ltd, Japan

1

With the advent of ammonia-air combustors, diagnosing the state of combustion within these devices becomes
necessary. As with hydrocarbon flames, ammonia-air
flames possess a measurable ion current and a relationship between the equivalence ratio of the ammonia
fuel-air mixture and this ion current is seen to exist. In
laminar stagnated flame experiments, this relationship isquite straight forward with the ion current peaking in thelean zone just shy of stoichiometry and falling off eitherside of this. However, in complex combustors such as swirl
burners, what can be described as a “spatial ion current
map” is observed. In order to understand the phenomena responsible for the complex ion currents observed in
combustors, numerical modelling becomes a necessity.
Arguably the most important component in this numericalmodeling process is the reaction mechanism. While several reaction mechanisms exist for ammonia-air combustion,
an ionic reaction mechanism did not exist prior to this97

Track02 Kinetics, mechanism reduction

Track02-3 Kinetics, mechanism
reduction (3)research endeavor. This study details the path taken indeveloping the ionic mechanism, how well it corroborates
experimental findings, its application in chemical kinetics
based numerical simulations, some peculiarities of applications in these models, and aspects of the mechanismthat require further improvement.
Contact: h-dhaminda@kitakyu-u.ac.jp

Simplified chemical reaction modeland its application in combustion anddetonation
Yuanxiang Sun

Beijing Institute of Technology, China

The simplified model of REDIM was established according to the experimental parameters and boundary
conditions in this paper . By comparing the relationshipbetween the CO2 generation rate and its mass fractionin the developed REDIM model and the same relationship diagram in the single-step method and the primitive
method, the validity of the REDIM model is verified. The
N-S equation considering viscous diffusion and heat conduction is established, and the LES control equation is obtained by spatial filtering of the N-S equation. The flame
surface density model is used in the single-step reaction
model and the elementary reaction model. In the REDIM
model, the flame surface density model is combined with
the REDIM method to generate a manifold to form a new
combustion model. A numerical simulation calculation
program capable of simulating the whole process of combustible gas flame acceleration and DDT was prepared.
Large eddy numerical simulations were carried out using
three chemically simplified reaction models (one-stepreaction model, 14-component 19-step elementary reaction model and REDIM model) for experiments of DDT insmall-scale pipeline and the scenario that DDT doesn’t
happen in small-scale pipeline. By comparing with theexperimental results, the accuracy of the numerical simulation results of the REDIM model is verified.
Contact: sunyuanxiang002@126.com

98

Chair: Akira Miyoshi
Friday, May 10; 13:00 - 15:00; Room J

On the kinetics of oxidation of n-butane
at high-pressure
Philippe Dagaut, Guillaume Dayma

Centre National de la Recherche Scientifique, France

The autoxidation of n-butane was studied experimentally in a jet-stirred reactor at 10 atm over a range of temperatures (530-1030 K) and equivalence ratios (0.25, 1, and
1.5). Products of oxidation were analyzed in the gas phaseby gas chromatography using several detectors (Flame
ionization detector, thermal conductivity detector, quadrupole mass spectrometer), hydrogen peroxide analyzer,
and Fourier transform infrared spectroscopy. Besides
the n-butane and oxygen, 38 products were quantified.
Kinetic modeling was performed using a kinetic reaction
mechanism already used to simulate previous n-butane
oxidation experiments in the cool-flame regime. Although
improvements are needed to better describe the oxidationof n-butane under the present conditions, the model represents the major trends of n-butane oxidation. A kinetic
analysis indicated the major reaction pathways to products and the sensitive reactions.
Contact: philippe.dagaut@cnrs-orleans.fr

Effect of Oxygen Enrichment on the
Combustion and Emission Characteristicsof Premixed n-Butane/Air Flames
Debojit Sharma1, Mani Bhusan Rajguru Mohapatro2,
Vanteru Mahendra Reddy1

Indian Institute of Technology, Kharagpur, India, 2Indian Institute ofTechnology Kharagpur, India

1

The numerical investigation is carried out on laminarpremixed n-butane/air mixtures enriched with oxygen,with the range of enrichment factors varying from 0 to 0.79
for lean (φ = 0.8), stoichiometric (φ = 1.0), and rich (φ =1.2) mixtures, respectively. The role of oxygen enrichment
on combustion characteristics is thoroughly investigatedby comparing its major global thermal properties andemissions using a detailed kinetic mechanism with 67 species and 475 elementary reactions. Oxygen enrichment
increases the overall heat release rates, flame speed,
adiabatic flame temperature, and reaction zone temperature. A gradual decrease in flame thickness is observed

19th International Conference on Numerical CombustionTrack02 Kinetics, mechanism reduction

with increasing O2 enrichment. The rate of increment inflame speed is more predominant in the range of oxygen
enrichment factor of β = 0-0.4, with respect to the higher
range of β = 0.5-0.79 for all the cases of equivalence ratio,
φ. The peak value of the heat release rate of the stoichiometric n-butane/air mixture increases by about 20.9%
and 48.5% for the enrichment factors, β = 0.4 and β = 0.79,
respectively. The CO emission index indicates a linearly
increasing trend with increasing O2 enrichment, while
the NOx emission index portrays parabolic dependencewith an increase in O2 enrichment. The outcome of thepresent work can be implemented as the fundamental database for CFD modelling of oxygen-enriched combustion
for the different hydrocarbons using DNS/LES modellingin real-time combustion applications.
Contact: sharmadebojit3@gmail.com

Reduced models for the methanehydrogen air systems using Reaction
Diffusion Manifolds accounting fordifferential diffusion

Sudhi Shashidharan1, Viatcheslav Bykov2, Ulrich Maas2
Karlsruhe Institute of Technology , Germany, 2Karlsruhe Institute ofTechnology, Germany

1

The description of differential diffusion, particularly inblended fuels, has always presented a challenging problem in manifold-based model reduction. In blended fuelmixtures, modelling diffusion coupled with reduced kinetics is a challenging task. In addition, considerable careis needed when using manifolds for the reduced system
integration, because system states that may evolve awayfrom the manifold due to diffusion processes have to berelaxed back onto the slow manifold which is both invariant and attractive.
In this talk, a generic approach to treat differential
diffusion effects in manifold based reduced models ispresented. To define a reduced system of equations, theterms in the governing equation are projected onto theslow manifold in local coordinates. The net rate of movement along the manifold then describes the evolution of
the system according to the slow processes. In addition,
it is shown that usage of generalized coordinates to describe the manifold and integrate the system equations
increases the robustness of the method considerably.
The approach is applied to Reaction Diffusion Manifolds (REDIMs) for premixed methane-hydrogen-air mixtures in freely propagating flames. The variation of flamespeed with change in hydrogen content in the mixture iscomputed and used to validate the reduced model.
Contact: sudhi.shashidharan@kit.edu

A ethanol reduced mechanism using realgas equation of state and its applicationin virtual chemistry

Paulo Vitor Ribeiro Plácido1, Henrique Beneduzzi
Mantovani1, Rogério Gonçalves Dos Santos1, Dario Alviso2
Universidade Estadual de Campinas, Brazil, 2Facultad de Ingeniería,
Universidad de Buenos Aires/CONICET, Argentina

1

Numerous studies have explored methods to decrease
particulate emissions from vehicle exhaust gas, significantly contributing to air pollution in urban areas. One
approach with promising potential is supercritical combustion, which involves injecting fuel over its critical temperature and pressure. Supercritical fluids have a lower
viscosity and surface tension than liquids and a higher diffusion rate, leading to a more uniform mixture distributionthat enhances thermal efficiency and reduces particulate
emissions. This study focuses on using supercritical ethanol as a biofuel option, proposing a reduced kinetic mechanism comprised of 71 species and 684 reactions obtained
through directed relation graph error propagation andsensitivity analysis. They validated this mechanism using
Cantera with a cubic Redlich-Kwong and an ideal equationof state for constant-volume auto-ignition delay time andlaminar flame speed simulations for pure ethanol. The IDT
results are consistent with experimental data at 10, 30, 50,
75, and 80 atm in a temperature range of 700 - 1250 K,
showing a satisfactory agreement with LFS experiments at
380 - 400 K, 1 - 4 atm and ($\phi$) of 0.6 - 1.4.
A two-step virtual chemistry optimized mechanism isderived from the developed ethanol mechanism to provide a mechanism suitable for high-fidelity applications.
The real chemistry mechanism was used to create thelearning database and the virtual mechanism to reproduce the evolution of the laminar flame speed and temperature profiles of a one-dimensional freely propagating
laminar premixed flame with the equivalence ratio for theethanol/air flame at 394 K and 1 atm.
Contact: p228244@dac.unicamp.br

A two-step virtual optimized kinetic
mechanism for butanol from a newly
developed detailed mechanism foralcohol fuels

Henrique Beneduzzi Mantovani, Rogério Gonçalves dos
Santos
University of Campinas, Brazil

The efficient use of energy resources and climatechange are important concerns in contemporary society.
So, the search for biomass-based renewable fuels have99

Track02 Kinetics, mechanism reduction

increased. Among the second generation biofuels, alcohol
fuels have many advantages and n-butanol has better
properties when compared to ethanol, such as higher
heating value and lower saturation pressure. To fully understand these fuels, a comprehensive description of thereaction pathways and high fidelity computational studies
are needed. The level of description of detailed mechanisms is usually prohibitive when dealing with high fidelity
simulation. To overcome the computational cost, numerical stability and modelling issues, chemical mechanism reduction techniques must be applied. The virtual chemistry
uses machine learning to derive a virtual mechanism froma detailed database. Using a genetic algorithm, a twostep virtual mechanism composed of a few virtual species
capable of capture the flame structure while mimetizing
mixture-averaged targeted quantities of the real compound is derived from scratch. However, the virtual mechanism does not model real reactions and species and thevirtual reactions and virtual species may be understood asa mathematical tool calibrated to mimetize the targeted
quantities. The present work presents a newly developed
detailed mechanism for alcohol fuels using the demi-decoupling methodology. Furthermore, the detailed mechanism is used to construct the learning database for virtual
chemistry and a two-step virtual mechanism for butanol
is derived. The specific heat capacity at constant pressure
and specific standard enthalpy of formation of the burnt
gases and laminar flame speed and temperature profiles
are defined as target.
Contact: henrique.bmantovani@gmail.com

100

19th International Conference on Numerical CombustionTrack03 Ignition, quenching

Track03 Ignition, quenching
Chair: Debojit Sharma
Thursday, May 9; 09:50 - 12:30; Room C

Numerical investigation of spark ignition
processes of NH3-H2-air mixtures in alaminar strained premixed configuration

Chunkan Yu1, Stefan Essmann2, Jacqueline HöltkemeierHorstmann2, Detlev Markus2, Robert Schießl1, Bo Shu2,
Ulrich Maas1
Karlsruhe Institute of Technology, Germany, 2Physikalisch-Technische
Bundesanstalt, Germany

1

Understanding the ignition properties of ammonia /hydrogen /air mixtures is essential because of their abundance in chemical engineering processes, and their prospective role as fuels in future energy systems. This work
investigates ignition processes of ammonia/hydrogen/air
laminar strained premixed flame configurations by numerical simulations. These track the evolution of ammonia/
hydrogen/air mixtures during and after the deposition ofignition energy, using a detailed treatment of chemical reactions and molecular transport . Studies on the influenceof different parameters on the minimally required ignitionenergy are performed. These are the strain rate, hydrogen content in the fuel, pressure and initial (pre-ignition)
temperature. Analysis of the results supports a knowledge-driven approach to the development of fail-safe
ignition devices and to a reliable prevention of explosion
hazards. The simulations are used for evaluating the ignitability of ammonia and its mixtures with hydrogen.
Contact: chunkan.yu@kit.edu

Numerical Investigation on Quenching
Distance of Laminar Premixed Methane/
Hydrogen-Air FlamesTahsin Berk Kiymaz1, Nijso Beishuizen2, Jeroen van Oijen1
Eindhoven University of Technology, Netherlands, 2Eindhoven Universityof Technology, Bosch Thermotechnology, Netherlands

1

The transition from natural gas to hydrogen has been
escalating in recent years. Fully hydrogen-fuelled burners,both at the industrial and domestic scales, have gained
attention. To facilitate this transition, an understanding of
flashback and quenching behaviour becomes crucial. In
this study, the flashback and quenching behaviour of laminar premixed flames is modelled in two dimensions withdetailed chemistry. Quenching distances are determinedby initially modelling a stable flame and then abruptly
decreasing the inlet speed of the mixture, enabling upstream propagation of the flame in a converging duct. The
quenching distance is defined as diameter at the point
where the flame extinguishes, mainly due to the heat loss
from the flame to the wall. The obtained results for methane and hydrogen-air mixtures at various equivalence
ratios are compared with experiments from the literature,demonstrating good agreement. The effect of premixture inlet speed on quenching diameter is investigated,revealing that the quenching diameter decreases with decreasing inlet speed. The variations in quenching diameter
across different geometries, such as slit, circular duct, or
annular duct, are also discussed in this work. Additionally,
the effect of wall temperature on quenching distance is
explored, revealing that quenching distance decreases
with increasing wall temperature.
Contact: t.b.kiymaz@tue.nl

Effects of Wall Heat Transfer Properties
on Head-on Quenching of Hydrogen/Air
FlamesMinha Baek, Dong-hyuk Shin

Korea Advanced Institute of Science and Technology, Korea

This study explores the impact of wall heat transfer on
the head-on quenching behavior of hydrogen/air flames.
Numerical simulations of one-dimensional laminar flames
were conducted using chtMultiRegionFoam of OpenFOAM v10. The solver uses (i) conjugate heat transfer, (ii)
mixture-averaged diffusion model, and (iii) the Wang-2018
mechanism. In order to quantify the wall heat transfer effects, three wall thermal conditions including (i) adiabatic,(ii) isothermal, and (iii) conjugate heat transfer were considered. For the conjugate heat transfer wall, a wide rangeof thermal conductivity and volumetric heat capacity of
the wall were explored to observe the head-on quenching
distance and heat loss to the wall. The findings indicate

101Track03 Ignition, quenchingthat an increase in thermal conductivity and volumetricheat capacity leads to higher heat loss through the wall
and an extended head-on quenching distance. Future
work aims to identify key relationships that can parameterize the quenching behaviors from adiabatic to isothermal wall conditions. Additionally, a predictive model will
be proposed to quantify the head-on quenching distanceand heat loss based on the thermal properties of the wall.
Contact: minha.baek@kaist.ac.kr

Numerical Study of Hydrogen Enrichment
Effects on Methane/Air Flame
Propagation in Crevices
Vili-Petteri Salomaa1, Mahmoud Gadalla2, Parsa
Tamadonfar1, Ville Vuorinen1, Ossi Kaario1
1

Aalto University, Finland, 2Wärtsilä , Finland

The propagation of premixed flames in narrow channels/enclosures is a typical problem encountered in
combustion devices. In internal combustion gas engines,
it has been speculated in the past that large proportionof the unburned hydrocarbon emissions may originate
from the flow of unburned fuel through the gap between
the piston rings and the cylinder wall. Due to the large
surface-to-volume ratio, a premixed flame may rapidly
quench upon propagating through the crevice and interacting with its walls, hence the accumulation of unburnedhydrocarbons. This scenario could be possibly alleviatedby increasing the mixture burning velocity through hydrogen enrichment. In the present study, we investigate a 2Dmodel problem of a premixed flame approaching a narrow
enclosure with cool walls at different channel heights andmethane/hydrogen ratios at atmospheric conditions. We
utilize direct numerical simulations and a finite rate chemistry solver in the OpenFOAM framework. We observe thatboth adding hydrogen to methane/air mixture up to 60%(molar) percent of the fuel mixture, as well as increasing
the crevice height may both individually promote theflame propagation to the end of the crevice, hence considerable reduction of the unburned hydrocarbons in thesystem.
Contact: vili-petteri.salomaa@aalto.fi102

DNS of forced ignition and flameedge dynamics in turbulent ammonia/
hydrogen/air and methane/air mixing
layersZhuchuan Chang, Haiou Wang, Kun Luo, Jianren Fan
Zhejiang University, China

Ammonia (NH3) is a promising zero-carbon fuel because of its mature manufacture, reliable large-scale storage and convenience in transport. However, the ignitionof ammonia/air mixture in practical combustion engines ischallenging due to the low reactivity of ammonia. Blending ammonia with hydrogen can improve the reactivity of
the fuel mixture, and promote the ignition process. In thepresent work, the ignition and combustion characteristics
of ammonia/hydrogen and the commonly used hydrocarbon fuel, i.e. methane, are investigated. In particular,
forced ignitions in turbulent ammonia/hydrogen/air andmethane/air mixing layers are studied using three-dimensional direct numerical simulation (DNS) with detail chemistry, and the aim is to investigate the ignition process
and flame-edge dynamics of ammonia/hydrogen/air andmethane/air mixtures. The general characteristics of theforced ignition process are analyzed and compared forvarious cases, with a particular focus on the heat release
rate and temperature distributions. The flame edges are
identified. The flame-edge speed and its components arecompared for various cases and the correlation between
the flame-edge speed and scalar dissipation rate is examined.
Contact: wanghaiou@zju.edu.cn

Large-Eddy Simulations for spark-ignitionof lean H2/air mixtures using a stretchadapted Thickened Flame Model
Sandy Poncet, Cédric Mehl, Karine Truffin, Olivier ColinIFP Energies Nouvelles, France

Lean hydrogen-air combustion is gaining interest in
the context of the energy transition towards decarbonizedfuels. Our study aims to simulate the spark ignition of alean H2/air mixture using the Thickened Flame Model(TFM) with adapted flame response to stretch. The TFM isa turbulent combustion model for Large Eddy Simulations(LES) widely used in industrial and academic studies [1]. In
prior studies, the TFM was coupled with Adaptive Mesh
Refinement (AMR) to reduce computational costs while
directly resolving chemical reactions on LES grids [2]. The
TFM ensures the preservation of the laminar flame speed.
However, it is well known that the standard TFM leads
to erroneous modification of flame speed and structure

19th International Conference on Numerical CombustionTrack03 Ignition, quenching

due to stretch effects induced by strain and curvature [3].
Thus, a methodology based on species diffusion adaptation to recover the flame response to low stretch rates,
previously validated on spherical and counter-flow laminar configurations, is here challenged in turbulent cases[4]. Sub-grid flame-turbulence interaction models fromthe literature are assessed for their applicability to a lean
H2/air mixture [5,6]. The impact of diffusion adaptation
for thickened stretched flames is evaluated on a spark-ignition configuration with homogeneous turbulence using
the TFM-AMR-Ignition approach [7].

Large Eddy Simulations framework. The Thickened Flame
Model coupled with an Energy Deposition strategy permits
an accurate prediction of the most significant phenomena involved, validating the employed numerical strategy.
Multiple operating conditions are explored, according to
the experimental setup, allowing to investigate different
ignition dynamics.
Contact: matteo.amerighi@unifi.it[1] O.Colin et al. doi:10.1006/jcph.2000.6538[2] C.Mehl et al. doi:10.1007/s10494-021-00261-2[3] S.Popp et al. doi:10.1016/j.combustflame.2019.04.047[4] S .Poncet et al. 11st European Combustion Meeting(2023), paper 439922[5] F.Charlette et al. doi:10.1016/S0010-2180(02)00401-7[6] G.Wang et al. doi:10.1016/j.combustflame.2011.04.008[7] E.Sandoval et al. doi:10.1016/j.combustflame.2022.112507
Contact: sandy.poncet@ifpen.fr

CFD investigations of the ignition andstabilization processes of bluff-body leanpremixed hydrogen flames
Matteo Amerighi1, Giada Senatori1, Tarik Yahou2, Thierry
Schuller2, James R Dawson3, Antonio Andreini1

1
Department of Industrial Engineering, University of Florence, Florence,
Italy, 2Institut de Mécanique des Fluides de Toulouse, IMFT, Université deToulouse, CNRS, Toulouse, France, 3Department of Energy and Process
Engineering, Norwegian University of Science and Technology, Trondheim
N-7491, Norway

Ignition and altitude relight are critical aspects in thedesign of a new aero-engine combustor, in relation tosafety, reliability and operability. The utilization of hydrogen as fuel offers several advantages in terms of combustion performance and environmental impact although it
is essential to consider the potential tendency to develop
undesirable flame-holding locations and flashback scenarios. These phenomena are related to the higher reactivity
of hydrogen and consequently to the major overpressurethat arises during the ignition phase with respect to conventional jet fuels. Therefore, it is mandatory that thecurrent numerical models can accurately predict transient
processes as ignition and flashback. In this context, theatmospheric test rig installed at the Norwegian Universityof Science and Technology (NTNU) operating with a lean,perfectly premixed, hydrogen-air flame that stabilizes on
a conical bluff body is considered. The complete hydrogen ignition sequence from spark release to full flame
development (second phase) is numerically investigatedwith the pressure based ANSYS Fluent in the high-fidelity103Track04 Turbulent combustion

Track04-1 Turbulent combustion(1)
Chair: TBD
Wednesday, May 8; 10:40 - 12:20; Room A

Direct numerical simulation of asupersonic turbulent boundary layer withhydrogen combustion
Chuhan Wang, Chun-Xiao Xu
Tsinghua University, China

In the aim to guarantee reliable ignition and maintainsustainable combustion within supersonic combustors,
a variety of injection strategies are employed including
injections via steps, cavities, structures, and throttles.
The interaction of flames with the intense shear found innear-wall turbulent flows is a common feature of these
implementations. The goal of the present study is to comprehend the intricate mechanisms of turbulent flow inboundary-layer combustion, through the use of direct numerical simulations. The selected flow model is a non-premixed hydrogen-air flame, ignited within a three-dimensional supersonic turbulent flat-plate boundary layer,
which operates at a Mach number of 2.44 and a friction
Reynolds number of approximately 1000. The simulation
involves a finite-rate model encompassing 9 species and19 chemical reactions. The inlet flow consists of preheated air in the mainstream and a hydrogen film injected in
proximity to the cold wall, inducing turbulent mixing via
the Kelvin-Helmholtz instability and auto-ignition of theflame within the boundary layer. Classical statistical metrics for turbulent closures are assessed. It is found thatthe turbulent Prandtl number and the turbulent Schmidt
numbers for each species tend to unity in the buffer layer
but deviate from unity near the flame front. A spectrum
analysis reveals that the strong Reynolds analogy is notsatisfied near the flame front region due to a scale separation between velocity and temperature fluctuations.
A statistical analysis of elementary reactions at different
distances from the wall is provided, highlighting the dominance of hydrogen atom depletion in the near-wall heatrelease and the prevalence of water vapor production in104



the contribution of heat release near the boundary layer’sedge.
Contact: chuhan_wang@mail.tsinghua.edu.cn

DNS of hydrogen flame stabilization in
multiple jets in cross flow
Zisen Li, Martin Vabre, Bruno Savard
Ecole Polytechnique de Montreal, Canada

Pure hydrogen combustion in gas turbines (GTs) is
extremely challenging due to its unique thermochemical
properties, such as high diffusivity which can lead to flashback, and potentially high combustion temperature, whichleads to NOx formation. “Micromix” combustion technology is a new approach that aims to address these challenges: by injecting hydrogen through an array of miniaturized
jets, it has the potential to produce reliable and safe combustion while minimizing NOx formation. Development of
this approach requires a detailed understanding of flamestabilization mechanism in the multiple jets in cross flow
configuration. In the present work, a direct numerical simulation (DNS) of two non-autoignitive hydrogen jets issued
into an air crossflow is reported. It is found that the flame
along the jet centreline plane features two branches, one
stabilized on the leeward side and one lifted above the jet
trajectory. The windward reaction zone is thinner in thenear field than the leeward one, while the lee-stabilized
branch is found to be more stable due to the larger andstronger recirculation zones created downstream of theinjection point. The results demonstrate that the flamestabilization is significantly affected by the interaction between jets, boundary layer, and the differential diffusion ofhydrogen.
Contact: zisen.li@polymtl.ca

19th International Conference on Numerical CombustionTrack04 Turbulent combustion

Direct numerical simulations of head-on
quenching of statistically planar turbulent
premixed flames on flat and rough walls
Zhaofan Zhu, Haiou Wang, Kun Luo, Jianren Fan
Zhejiang University, China

Rough walls are common in engineering applications.
However, existing understanding of combustion nearrough walls is lacking. In the present work, direct numerical simulations (DNS) of head-on quenching of statisticallyplanar turbulent premixed flames on flat and rough walls
are reported for the first time. Hydrogen is consideredas the fuel because of its high importance in a zero-carbon economy. The wall heat flux and flame quenching
distance statistics for laminar and turbulent premixed
flames head-on quenching on isothermal inert walls withvarying roughness are compared. The alignment quantity
measured the angle between the flame normal vector at
the quenching edge and wall normal vector on various
rough walls are examined. The near-wall behaviors of intermediate species and reactions in head-on quenching
are demonstrated. Finally, the model performances in
the context of the flame surface density (FSD) and scalardissipation rate (SDR) based reaction rate closures on flatand rough walls are explored.
Contact: wanghaiou@zju.edu.cn

Direct Numerical Simulation of turbulent
premixed combustion in a model
turbulent flow with mean shear at Reλ =140 and single reactive scalar Zeldovichrate closure
Aditya Vinod, Tejas Kulkarni, Fabrizio Bisetti
The University of Texas at Austin, United States

Direct Numerical Simulations (DNS) of turbulent premixed flames are employed to study the evolution of theflame surface in the turbulent swirling von Kármán flow,which is characterized by intense shear-driven turbulence.
The combustion closure features a single passive reactive scalar with a source term equal to the Zeldovich ratefunctional. Such a single scalar combustion model coupled with DNS of reactive turbulence is computationallyaffordable, enabling parametric studies at scale. Turbulent
flames are initialized as a spherical kernel of burnt gasesin the center of the device, where turbulent transport byvelocity fluctuations is dominant, and propagate outwards.
The Reynolds number is increased up to Reλ = 140 acrossthree configurations holding the Damköhler number
constant. The flame Surface Density Function is shown toscale in time according to a common function and found

to be self-similar with respect to a similarity distance variable. The peak of the SDF is scaled by a power law of the
Reynolds number with exponent nearly identical to thatreported in recent numerical and experiment studies ofturbulent spherically expanding flames. The form of thescaled and self-similar SDF explains the trends of flame
area with increasing Reynolds number.
Contact: vinoda@utexas.edu

On the occurrence of negative
propagation speeds and negative
divergence in turbulent premixed flames
Fabrizio Bisetti1, Antonio Attili2, Aditya Vinod1, Tejas
Kulkarni1

The University of Texas at Austin, United States, 2University of Edinburgh,
United Kingdom

1

Based on the analysis of data from Direct Numerical
Simulation of turbulent premixed flames with finite ratechemistry, we find that the propagation speed of reactive
fronts in turbulent premixed flames takes instantaneous
values that are negative in sign and large in absolutevalue. The ensuing probability density function of the
propagation speed is complex: the PDF has a positive
mean, is at times bimodal with two local maxima – one atpositive and one at negative values for sufficiently highvalues of the Reynolds number, is skew-positive, and has
a large kurtosis indicating extreme events. Further, negative displacement speeds correlate strongly with negativevalues of the velocity divergence and large values of themost compressive strain eigenvalue. We also find a clear
dependence of the statistics of the rate of strain tensor
on the Karlovitz number, whereby as the Karlovitz number
decreases, the probability that all strain eigenvalues are
positive increases for small values of strain. These results
are fundamentally inconsistent with existing theory that
explains changes to propagation speed with the effect ofstretch. Instead, statistics appear to be closely related toclassical mechanisms of scalar mixing in isothermal turbulence with Reynolds number effects pertaining to smallscale intermittency.
Contact: fbisetti@utexas.edu

105Track04 Turbulent combustion

Track04-2 Turbulent combustion(2)
Chair: TBD
Wednesday, May 8; 10:40 - 12:40; Room B

Relationship between Radial Pressure
Gradient and Flame Macrostructure in
NH3/H2/Air Premixed Swirl Burners
Clifford Goertemiller, William Northrop
University of Minnesota - Twin Cities, United States

This work investigated the influence of radial pressure
gradient on flame macrostructure in NH3/H2/Air fueled
premixed swirl burners operating in rich-lean staged combustion. Five different burner geometries were operated at
equivalence ratios from 0.72 to 1.10, hydrogen mole fractions from 0% to 27%, and jet Reynolds Numbers from500 to 21,000. Type I, II, III and IV flame macrostructures
were identified using OH* and NH2* chemiluminescence.
Measured radial pressure gradient of the fuel-air vortices
was compared against theoretical radial pressure gradients of free and forced vortices. The measured pressure
gradient for type I and II macrostructures corresponds toa pressure gradient typical of free vortices while the measured pressure gradient for type III and IV macrostructures
corresponds to that of a forced vortex. Characterizing
the radial pressure gradient and flame macrostructure
provides a basis for validating LES and DNS simulations.
Understanding the influence of burner operation on flame
macrostructure allows for design of burners with smaller
computational domains, reducing simulation cost. Finally,
the fueling and emissions associated with rich and lean
combustion zones of the swirl burner were investigated toprovide boundary conditions for simulating the lean burnzone as a laminar diffusion flame, further reducing computational cost.
Contact: goert023@umn.edu

Local Curvature and Speed of Turbulent
Premixed Ammonia and Blends with
Methane and Hydrogen Flames in a
Spherically Expanding Configuration
Seif Zitouni, Pierre Brequigny, Christine MounaimRousselle
Université Orleans, France

Ammonia (NH3) appears a promising zero-carbon fuel,however most energy conversion systems require a combustion promoter such as Hydrogen (H2) or Methane (CH4)106

to guarantee start-up, stability and combustion efficiency.
Yet, there remains limited studies for ammonia combustion under relevant turbulent conditions. To that end, theoutwardly propagating flame configuration was employed
to determine turbulent propagation characteristics of various ammonia blends, employing Mie-Scattering tomography coupled with numerical analysis facilitating flame
structure investigation. Three Ammonia based blends
were selected (60%NH3 – 40%H2 φ = 0.8, 70%NH3 –30%H2 φ = 1.0, 40%NH3 – 60%CH4 φ = 1.0), exhibiting
ostensibly similar laminar burning velocities (SL0) but
different flame stretch sensitivities (Lewis Number (Le),Markstein Length (Lb)); allowing to gain insight on theeffect of flame stretch and wrinkling effect at constantturbulent intensity to laminar flame speed ratio (u’/SL0)
and ratio of integral length scale and flame thickness (LT/δG). Enhancement in turbulent flame speed was observed
to increase with decreasing Lewis number and Markstein
Length. This observation was supported by local flame
analysis. With a decrease in Le and Markstein Length, theprobability density function (PDF) of curvature at a fixed
eddy turn over time distinctively spread towards greater
negative curvatures coupled with the appearance of highspeed values on the negative curvature side. Furthermore,
an increase in the stretch factor (I0) was observed withblends containing highest amount of H2, opposite to thetrend in wrinkling ratio. These results in turbulent NH3based flame behaviour are thought to invariably impact
practical combustion systems.
Contact: seif-eddine.zitouni@univ-orleans.fr

Combustion characteristics of NH3/O2
pintle engines
Jun Li, Rui Zhou

Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences,
China

Combustion characteristics of oxidant-centered NH3/O2 pintle engines under different total momentum ratio conditions and different mixing ratio conditions arestudied by a two-dimensional numerical simulation using a detailed 80-step chemical reaction mechanism ofammonia. Results show that high chamber pressure canachieve high combustion efficiency at a mixing ratio of
1.2. The high chamber pressure can promote the mixing
and combustion of the fuel and oxidizer, increasing the
combustion rate, which can release the energy of the fuelmore quickly, improving the combustion efficiency. A mixing ratio of 0.96 and a total momentum ratio of 0.93 havea high combustion efficiency at a chamber pressure of 4.8
MPa. When the mass flow rate of oxygen is close to themass flow rate of ammonia, this means it is at a stoichio-

19th International Conference on Numerical CombustionTrack04 Turbulent combustion

metric ratio, and when the total momentum ratio is close
to unity, it can enhance the mixing, further strengthening
the complete reaction, and thus, improving combustion
efficiency.
Contact: zhourui0331@outlook.com

INVESTIGATION OF AMMONIA (NH3)COMBUSTION WITH DIESEL PILOT
IGNITION
Zainal Abidin

Southwest Research Institute, United States

All transportation sectors are seeking methods to decarbonize their energy sources. For high energy consumption applications (e.g. large marine, locomotives), ammonia
is a potentially attractive carbon-free fuel option, primarily
due to its ~2x volume energy density compared to very
high pressure gaseous hydrogen. With a desire to retain
full diesel capability, one approach to use ammonia as afuel is a dual fuel concept where ammonia is pre-mixed
with air and then ignited by the diesel injection.
This paper considers the mechanisms of ammonia-diesel dual-fuel combustion. The dual fuel combustion
process is complex, relying on the injected diesel fuel toignite and combust the ammonia and air mixture. The
ammonia-diesel, dual-fuel combustion is a mixture ofdiffusion burning, in the case of the diesel pilot, and offlame propagation, in the case of the ammonia not entrained in the diesel jet. The combustion computational
fluid dynamics (CFD) simulation provides insight into theunderstanding of ammonia-diesel dual-fuel combustion,
including limitations on ammonia substitution and methods for reducing ammonia emissions. An ammonia combustion kinetic mechanism was identified in the literatureand merged with the diesel kinetic mechanism to form adual-fuel mechanism for the simulation. The model was
refined to better match the experimental data for thelaminar flame speed of ammonia versus equivalence ratio published in the literature. The simulations identified
multiple mechanisms critical to diesel-ammonia dual fuelcombustion. The dominant mechanism is dependent on
the ratio of ammonia to diesel, the substitution ratio (SR),and the air-ammonia equivalence ratio.
Contact: zainal.abidin@swri.org

Large-eddy simulations of hydrogenenriched natural gas flames in a trapped
vortex combustor

Aritra Roy Choudhury, Nikhil Verma, R. V. Ravikrishna,
Konduri Aditya
Indian Institute of Science, India

The trapped vortex combustor (TVC) is a promisingtechnology for premixed combustion with fuel flexibility.
This combustion configuration promotes better fuel-air
mixing and has the potential to reduce emissions. Depending on the flow configuration, a TVC can operate
in rich burn, quick quench, and lean burn (RQL) mode
which is investigated in the present study. Particularly, we
employ high-fidelity large-eddy simulations (LES) to investigate the flame stabilization mechanism and flow-chemistry interactions. The TVC configuration comprises achannel that expands into a unity aspect-ratio cavity,
which locks the primary vortex and stabilizes the flame.
While a lean premixed mixture is introduced at the inletof the channel, a rich mixture is injected at the bottom of
the cavity. The simulations were conducted using OpenFOAM, an open-source C++ library for computational fluid
dynamics (CFD). The k-equation subgrid model and thepartially stirred reactor (PaSR) model were implemented
for the closure of sub-grid scale terms. To investigate theeffect of the addition of hydrogen, we considered twocases: one with pure methane and the other with a 5050 mixture of hydrogen and methane. The overall equivalence ratio is kept constant at 0.7. The results from thesimulations are compared with experimental OH planar
laser-induced fluorescence (PLIF) data. It is observed thatthe addition of hydrogen inhibits the unsteadiness in the
combustion process and improves the penetration of thecavity flow into the main channel flow, which in turn enhances the pattern factor. A quantitative assessment ofthese aspects will be presented.
Contact: aritraroy@iisc.ac.in

Large Eddy Simulation of Flame Flashback
Phenomenon in a Model Scramjet
Combustor Utilizing a Strut-Cavity Flame
HolderSingeetham Pranaykumar, Amardip Ghosh
Indian Institute of Technology Kharagpur, India

Efficient hypersonic air-breathing propulsion, crucial
for cost-effective payload launches, faces challenges suchas inadequate combustion due to short flow residence
times. The development of efficient scramjets relies on
flame stability. Despite the widely held belief that acous-

107

Track04 Turbulent combustion

tic disturbances cannot propagate in supersonic flowfields, evidence shows instances of flame flashback.
Existing scramjet studies on flashback lack consensus,
necessitating thorough research. Supersonic turbulent
combustion simulations, conducted with the OpenFOAM
solver within a large eddy simulations framework, involved
three-dimensional, transient, and multi-species chemically reacting conditions. We explored a novel strut-cavity
flame holder configuration, confirming simulation accuracy against DLR’s strut design data. Flame lift-off wasobserved in the base case with a strut configuration akinto previous findings. A 9-species, 27-reaction Arrhenius
model investigated hydrogen fuel flame behaviour during
flashback scenarios. RANS simulations fine-tuned flame
holder design parameters. The shear layer, originatingfrom the cavity corner’s leading edge, impinges on thetransverse fuel injection from the rearward step of theoffset cavity. This impingement results in a complex flow
field around the strut-cavity flame holder, characterized
by interactions between shear-layer shock phenomenon,
cavity recirculation zones, and the trajectories of both theshear layer and fuel. LES directly influences fuel and oxidizer mixing, impacting chemical reaction rates and combustion efficiency. LES effectively depicts turbulent flame
dynamics, examining flame structures and their interactions with shocks and the turbulent flow field. This study
aims to understand the intricacies of combustion and thefactors contributing to supersonic flame flashback usinglarge eddy simulation.
Contact: pranaysingeetham007@gmail.com

Track04-3 Turbulent combustion(3)
Chair: Shinji Nakaya
Wednesday, May 8; 13:30 - 15:10; Room A

Study of turbulence back-scatter in alaboratory-scale swirl stabilized aerocombustor using DNS
Bruno S. Soriano, Jacqueline Chen
Sandia National Laboratories, United States

Classical theories of turbulence suggest that the kinetic energy cascade in nonreacting flows has a net transfer
of energy from large to small scales. However, previous
studies demonstrated that the thermal expansion ofpremixed flames can reverse the flux of energy throughthe injection of energy at flame scales into larger scales,
resulting in back-scatter. These observations were confirmed experimentally for a premixed laboratory-scale aero-combustor. However, it is unknown whether backscatter108also occurs in partially-premixed combustion in a swirl-stabilized combustor undergoing localized extinction/reignition near the lean blowoff limit. In this limit, edge flame
propagation is found to exist, and it's structure presents apremixed leading edge that generates large thermal expansion compared to non-premixed flames, acting as a sourceof flame-generated backscatter. Direct numerical simulation (DNS) of a laboratory-scale swirl stabilized aero-combustor is performed for a reacting Jet-A liquid spray flameand backscatter is quantified from the filtered and subgrid
kinetic energy transport equations evaluated in physical coordinates. It is found that edge flames lead to an inversionof the turbulent kinetic energy cascade at scales close to
the flame thermal thickness. The back-scatter occurs within
the flame brush and correlates with dilatation generated
by thermal expansion. The total pressure gradient-velocity
correlation term is also observed to produce kinetic energy
at subgrid scales due to subgrid fluctuations in the pressure
field caused by turbulent combustion. Hence, aero-combustors undergoing blow-off are more prone to back-scatter due to the development of edge flames that propagate
to reignite previously extinguished regions.
Contact: bsouzas@sandia.gov

A study of the relation among flame
surface geometry, flow and heat onpremixed turbulent flames using DNS
Kazuya Tsuboi, Takao Matsuka
Okayama University, JapanThe surface geometry of premixed turbulent flame
interacts with flow and heat. This study focuses on therelation among the flame surface geometry based upon
flame curvature, local flow and heat on premixed turbulent flames using DNS (Direct numerical simulation). This
analysis is performed by using DNS data of premixed turbulent flames (Nishiki et al., CTM 10 (2006), Tsuboi et al.,JTST 3 (2008)). The flame surface geometry is consideredby mean flame curvature and Gauss curvature on theprescribed iso-surface of the reaction progress variable
defined by temperature. The flame surface geometry
based upon the aforementioned curvatures varies withthe reaction progress variable even though the premixed
turbulent flames on the DNS data is located near theboundary between the wrinkled flamelets regime and thecorrugated flamelets regime on the diagram of premixed
turbulent combustion. This study makes a detailed analysis of the relation among the flame curvatures, local flow
and heat with the different iso-surfaces of the reaction
progress variable.
Contact: tsuboi@okayama-u.ac.jp

19th International Conference on Numerical CombustionTrack04 Turbulent combustion

DNS of multi-stage ignition in a simplified
gas turbine premixer
Martin Vabre1, Zisen Li1, Sandeep Jella2, Philippe
Versailles1, Gilles Bourque2, Marc Day3, Bruno Savard1

1
Polytechnique Montréal, Canada, 2Siemens Energy Canada Limited,
Canada, 3National Renewable Energy Laboratory, United States

With the increasing need for fuel-flexibility, mitigationof auto-ignition inside gas turbine (GT) premixers has
become crucial. GT premixers must be designed to ensure sufficient fuel-air mixing while avoiding the potential
occurrence of auto-ignition, a challenge that requires adetailed understanding of turbulent mixing and chemistry interaction. Here, direct numerical simulations of adownscaled and simplified version of a GT premixer arepresented. The configuration consists of multiple hot air
jets in a fuel-rich crossflow (Rej=4000) at high pressure.
A fuel blend of methane and dimethyl ether (DME) is
chosen with a recent reduced chemical kinetics model
validated in GT conditions. The addition of DME drasticallyincreases the explosivity of the fuel mixture and causes
a multi-stage ignition to occur, each stage resulting in acorresponding flame. For each stage we track the temporal evolution of individual ignition kernels in both physicaland phase-space, and assess their propagation modethrough chemical explosive mode analysis. The observed
ignition events differ for the different stages, with large
ignition patches for low temperature ignition and quickly
growing small kernels for high temperature ignition. In allcases, both diffusion and auto-ignition contribute significantly to the subsequent flame stabilization.
Contact: martin.vabre@polymtl.ca

Direct Numerical Simulation of LowEmission Staged Ammonia Combustion
Martin Rieth1, Andrea Gruber2, Evatt R. Hawkes3,
Jacqueline H. Chen1

Sandia National Laboratories, United States, 2SINTEF Energy Research,
Norway, 3University of New South Wales, Australia

1Ammonia is a potential carbon-free alternative to natural gas in dispatchable power generation. However, burning ammonia in typical lean premixed gas turbine combustors leads to high levels of nitrogen oxide emissions.
A promising strategy to mitigate such emissions is thestaged rich-quench-lean (RQL) approach. With the RQL
approach, an ammonia fuel-rich flame is stabilized in the
primary combustion zone (PCZ), where fuel-bound nitrogen is converted in an oxygen-depleted environment, minimizing nitrogen oxide emissions. A secondary combustion zone (SCZ) comprises injection of air leading to theconsumption of hydrogen that is present in the productsfrom the PCZ. We present Direct Numerical Simulation(DNS) of a simplified SCZ configuration, namely transverse
injection of cold dilution air into a cross-flow of hot hydrogen-containing pyrolyzed ammonia combustion products
at equilibrium, at thermochemical conditions comparable
to those of a heavy duty stationary turbine. The DNS shedlight on the turbulent combustion and flame stabilization
process of the SCZ, as well as emission formation in the
SCZ and further downstream of the air injection. Threecross-flow equivalence ratios (1.1, 1.2 and 1.3) are simulated to study the impact of different air split ratios. An
additional DNS is presented where a small amount of ammonia slip is present in the boundary regions of the flow,
illustrating the detrimental effect ammonia slip can haveon the performance of the RQL strategy.
Contact: mrieth@sandia.gov

A DNS study of ignition characteristics of
NH3/H2/air mixtures under RCCI marine
engine conditions with hydrogen injection
strategy
Yijun Hou, Chun Sang Yoo

Ulsan National Institute of Science and Technology, Korea

Ammonia (NH3) is gaining interest as a carbon-neutral
alternative in transportation applications, especially in themaritime sector. Nevertheless, using NH3 as the primaryfuel for engines encounters challenges due to its low
reactivity and flame speed. Hydrogen (H2) emerges as apromising additive to address the reluctance to combustof NH3. Two-dimensional direct numerical simulations(DNS) are employed to elucidate the effects of H2 injection on the ignition characteristics of NH3/H2/air mixtures
under medium-speed marine engine conditions. NH3 isinjected as port fuel, with an initial H2 injection occurring
early to enhance the reactivity of NH3 and a subsequent
H2 injection near the top dead center (TDC) to induce reactivity stratification. A compression heating model is incorporated into the DNSs to simulate the rise in pressure
resulting from the piston motion. Accounting for the cooling effect attributed to the second H2 injection, a pseudo
H2 species is introduced. Chemical Explosive Mode Analysis (CEMA) investigates the intricate interaction among
reactivity stratification, cooling effects, and turbulence
intensity. Comparative analysis with a single H2 injection
reveals that the split injection strategy can defer early ignition by generating stratified combustion. Conversely, thesplit injection strategy accelerates the ignition process forlate ignition scenarios.
Contact: houyijun0403@unist.ac.kr

109

Track04 Turbulent combustion

Track04-4 Turbulent
combustion (4)Chair: Andreas Kempf
Thursday, May 9; 09:50 - 12:30; Room A

Physics-constrained neural-network subgrid-scale model for a flame in isotropic
turbulence
Seung Won Suh1, Jonathan MacArt2, Luke Olson1,
Jonathan Freund1

University of Illinois Urbana-Champaign, United States, 2University ofNotre Dame, United States

1

A neural-network sub-grid-scale model for large-eddy
simulation (LES) of turbulent reacting flows is developed.
A key aspect is that the closure model is trained a posteriori—on a model-predicted observable. This is more robust
than the a priori approach, where the objective function
would be based on the model itself. Our approach requires the end-to-end sensitivity of the observable withrespect to the parameters of the model, which is computed using a discrete-exact adjoint solver. It is demonstrated
on a statistically planar premixed flame in isotropic turbulence with one-step single-species irreversible chemistry
in a thin-reaction-zone regime. The model is constrained
to preserve Galilean invariance and local conservation,
and also not to introduce spurious oscillations in scalar
fields. We first train the model so its short-time prediction on the instantaneous field matches that of a direct
numerical simulation. The trained model is then applied
for a longer-time LES. Finally, the model is evaluated interms of turbulent energy spectra and the turbulent flame
speed.
Contact: suh29@illinois.edu

Filtered turbulent flame model: numericalprinciple and performance
Lipo Wang

Shanghai Jiao Tong University, China

Modelling the interaction between flame and turbulence under the resolved scale depends on the closure
reasonability. Physically, the flamelet assumptions remain
reasonable in typical combustion simulations. Therefore
species mass fractions and temperature can be mapped
onto the mixture fraction, scalar dissipation and otherrelevant quantities. However, critical modeling closure
problems do exist, especially the assumed joint probability
density functions (PDFs) to calculate the filtered or mean

110field quantities. Aiming for such challenge issues, a newly
proposed filtered turbulent flame model is implemented
in the framework of large eddy simulations for non-premixed turbulent combustion. The general principles ofmodel realization are developed, including the structure
and physics of the filtered flame, tabulation setup, andthe numerical algorithm. Because of the involved modeling parameters for tabulation can be directly calculated
from either the resolved or subgrid model quantities, thefiltered turbulent flame model is in principle favorable toimprove the numerical predictability. Tentative numericaltests and comparisons with other models justify this modeling idea. Possibilities for further improvements and thenumerical principles are also addressed.
Contact: Lipo.wang@sjtu.edu.cn

Direct moment closure model coupledwith acceleration algorithm for LES of
turbulent partially premixed dimethyl
ether jet flame

Runzhi Liu, Yicun Wang, Kun Luo, Tai Jin, Jiangkuan Xing,
Jianren Fan
Zhejiang University, China

The development of a turbulent combustion model
for partially premixed flames remains a significant challenge due to the coexistence of premixed and non-premixed modes. In this study, the Direct Moment Closure(DMC) model, known for its methodological applicability
to various combustion regimes, has been extended tomulti-reactant reactions with closure of higher-order moments. The DMC model has been applied to simulate abenchmark flame of a piloted partially premixed dimethyl
ether jet flame in the TNF Workshop. The Large Eddy
Simulation with DMC model (LES-DMC) results have been
compared with experimental data and results from theliterature. Remarkably, the DMC model exhibits excellent
performance in predicting the spatial distribution and mixture fraction-conditional average of velocity, temperature,
mixture fraction, and mole fraction of major and minor
species. The accuracy and efficiency of the acceleration
algorithms, coupled with LES-DMC, have been thoroughly
assessed. As a result, the overall computational cost of
LES-DMC-TDAC is significantly reduced to 45%. The simulation results have facilitated a detailed analysis of thecharacteristics of the partially premixed dimethyl ether
flame.
Contact: ringsliu@zju.edu.cn

19th International Conference on Numerical CombustionTrack04 Turbulent combustion

On Flamelet calculation methods toincorporate effect of flow strain inpresence of large heat loss in turbulent
flame propagation models
Sandeep Lamba1, Krishnakant Agrawal2

Indian Institute of Technology (IIT) Delhi, India, 2Indian Institute ofTechnology (IIT) Delhi, India

1

Incorporating effects of heat loss and flow strain on
the turbulent flame propagation is of wide interest for
capturing flame shape and instabilities in practical combustion chambers. For lean-premixed combustion systems, a canonical laminar counterflow premixed flame isused to tabulate the laminar flame speed variation withvarying strain rate and heat loss through enthalpy defect- chemical or sensible. The laminar flame speed becomesa factor in turbulent flame propagation speed models,thereby incorporating heat loss and strain effects in actual flame propagation. However, correlation of strain rate(local or global) obtained from the canonical flames withthat obtained for turbulent flows in combustion chamberusing CFD (mostly Large Eddy Simulations) is somewhat
qualitative. Also, large heat losses necessarily require
use of chemical enthalpy defect, which can interfere withsome assumptions needed to capture the strain rate effect, such as using ‘fresh against burnt’ counterflow setup
and not the ‘reactant against reactant’ or the ‘twin flame’.
Such details are not immediately obvious to practicing
CFD engineers and may lead to erroneous modelling. This
presentation discusses details of calculation methods ofcanonical laminar flames to capture the effect of strain inpresence of high heat loss for a practical turbulent flame.
Results are presented in terms of flame stabilization nearwalls with large heat loss for a tangential inlet swirl premixed burner case from literature and compared with experimental data to highlight modelling recommendations.
Contact: kkant@mech.iitd.ac.in

DEVELOPMENT OF A VIRTUAL
CHEMISTRY REACTION MECHANISM
FOR H2/CH4 TURBULENT COMBUSTIONMODELLING
Simone Castellani1, Roberto Meloni2, Antonio Andreini11

Università di Firenze, Italy, 2Baker & Hughes, Italy

The species transport models are one of the most
attractive solutions to capture complex phenomena suchas differential diffusion stretch and heat loss on the flame
front. One of the biggest drawbacks of these combustion
models is the high computational cost that can become
prohibitive when higher-order hydrocarbons have to beincluded in the fuel mixture. The need to reduce the number of species to be transported and the complexity of thereaction mechanism raises the need to develop “ultralight”
kinetics schemes.
In this work, a virtual reaction mechanism has been
proposed and derived for the investigation of H2/CH4
combustion. Since the differential diffusion is expected toplay a pivotal role in high H2 content mixtures in lean conditions, the proposed model accounts for the differential
diffusion of the fictitious species. The predictivity of thevirtual chemistry model has been validated on a turbulent
combustion test case at atmospheric pressure. In the LES
simulations, the Thickened Flame Model has been adopted for modelling the turbulence chemistry interaction. The
numerical results are compared with OH* chemiluminescence measurements to assess the prediction capabilityof the virtual chemistry reaction model in reproducing theflame shape detected in the experimental campaign.
Contact: simone.castellani@unifi.it

Numerical Modelling of Local Extinction
in Sydney Swirling Non-Premixed Flames
using LES/FGM

Nicholoy Pestheruwe1, Lin Ma2, Derek Ingham2, Ruoyang
Yuan2
University of Sheffield, United Kingdom, 2University of Sheffield, United
Kingdom

1

Flame extinction emerges as a fundamental exploration within combustion theory and contemporary combustor design for gas turbines, particularly near lean blowout.
Employing Large Eddy Simulation (LES) and Flamelet
Generated Manifold (FGM) methods, the study simulates
the Sydney swirl-stabilized non-premixed methane flames,
exhibiting varying degrees of local extinction. The FGM
framework demarcates chemistry through mixture fraction
and reaction progress, constructing the manifold via 1D
counter flow flamelets. Examining statistics encompassing
velocity, mixture fraction, and major species mass fractions in physical and mixture fraction space reveals goodalignment with experimental measurements. The level of
local extinction with increased fuel bulk velocity velocities is reasonably captured, revealing its manifestation
through a very low heat release rate, reduced OH massfraction and temperature, and relatively high scalar dissipation. In contrast to conventional indicators, the findings
emphasize the significance of considering multiple factors
to identify local extinction events accurately.
Contact: nlcpestheruweliyanaralalage1@sheffield.ac.uk

111

Track04 Turbulent combustion

Clipping-free fine structure's massfraction region for low turbulence Eddy
Dissipation Concept model
Agnieszka A Ciesielska , Adam Klimanek , Michal T
Lewandowski2, Nilanjan Chakraborty3, Hazem Awad4
1

1

Silesian University of Technology, Poland, Norwegian University of
Science and Technology, Norway, 3Newcastle University, United Kingdom,
4
Cambridge University, United Kingdom
1

2

To predict strong turbulence-chemistry interactions
as in Moderate or Intense Low oxygen Dilution (MILD)
combustion regime, the Eddy Dissipation Concept (EDC)
model has been successfully applied using Reynolds- Averaged Navier-Stokes (RANS) or Large-Eddy Simulations(LES) modeling. However, several studies of the Jet in Hot
Co-flow (JHC) configurations have shown that in its standard formulation it overpredicts the maximum temperaturelevel in MILD regimes, due to overestimated overall reaction rate. It is assumed that the reactions take place in theregions of the flow where the dissipation of turbulencekinetic energy takes place. The mass fraction of the finestructures γλ is provided by an energy cascade model. In
various numerical codes, an upper limit for γλ is 0.7 - 0.9
for low Reynolds (Re) numbers. To avoid misunderstanding and trivial γλ limit, and based on the Direct Numerical
Simulations (DNS) normalized reaction rate values comparison, three formulations (velocity- and length scalebased) were selected and validated, using Ansys Fluent,against the Delft JHC burner (low turbu- lence), and Sandia
Flame C and D (high turbulence), to ensure alignment
with the developed original EDC model assuming highturbulence. The results show a reduction in temperaturepeaks by implementing new revised pos- tulates. In thecase of Sandia D, two low turbulence postulates lead tothe flame extinction (unscaled); for Sandia C only one, as
expected, due to low γλ values at low Re. They exhibit
similar performance to the original EDC downstream of
the flame, with some underpredictions near the burner
nozzle, when scaled (to converge with the original EDC athigh Re) or blended for a moderate turbulence transitionzone and the original EDC formulation for high Re (shrinking cascade model: 1-, 2-, or 3-level energy cascade). The
research is ongoing, and we look forward to sharing our
finalized results and insights during the conference involving variable reacting fraction χ implementation, resultswith additional Re blending limits (to achieve broader
spectrum of Re), and eventually run a priori DNS test of
the hybrid (blended) model.

Effects of cryogenic temperature on
turbulent premixed hydrogen/air flames
Chongpeng Chen1, Cheng Chi2, Dominique Thévenin2,
Wang Han1, Lijun Yang1

School of Astronautics, Beihang University, China, 2Lab. of Fluid Dynamics
and Technical Flows, University of Magdeburg ``Otto von Guericke",
Germany, Germany

1

As a carbon-free fuel, hydrogen (H2) is of increasing
importance in the development of low-emission engines.
Due to a low volumetric energy density, H2 is preferably stored at cryogenic temperatures (Tu≤100 K). In thiscontext, it is indispensable to investigate the combustion
behavior of hydrogen at such low temperatures. Althoughsome studies focused on the ignition and detonation ofhydrogen, investigations about premixed H2/air flame
propagation interacting with turbulence at cryogenic temperatures are rather scarce. In this work, stoichiometricturbulent premixed H2/air flames are studied at cryogenic
temperature (Tu=100 K) and normal temperature (Tu=300
K), using three-dimensional direct numerical simulations
with detailed chemistry and transport. It is found that at
cryogenic temperature, dimensionless turbulent flame
speed and flame surface area increase significantly due
to Darrieus-Landau instability (DLI) induced by a large
expansion ratio. Since the effective Lewis numbers of thetwo cases are close to unity, the diffusive-thermal instability (DTI) is negligible in the cases. Furthermore, it isfound that there are substantial differences in the peaksof HO2 and H2O2 mass fractions between the two cases,
probably due to smaller local flame curvatures at cryogenic temperature. Moreover, the results indicate that theflame response to stretch is not sensitive to the change ofthe initial temperature. A larger fractal inner cutoff scale
is found at Tu=100 K, suggesting that the flame exhibits
more large-scale flame wrinkling than that at Tu=300
K due to the impact of DLI. All these facts lead to theconclusion that cryogenic temperature can significantly
promote large-scale flame wrinkling, increase turbulent
flame speed and flame surface area, and affect intermediate species distribution. This suggests that combustion ofcryogenic H2 may have a high risk of flashback.
Contact: chongpengchen@buaa.edu.cn

Contact: agnieszka.ciesielska@polsl.pl112



19th International Conference on Numerical CombustionTrack04 Turbulent combustion

Track04-5 Turbulent combustion(5)
Chair: Benoît Fiorina
Friday, May 10; 09:50 - 12:10; Room A

Experimental and Numerical Investigationof Lean Blowoff Dynamics in SwirlStabilized Premixed Flame
Vishnu Raj, Chockalingam Prathap

Indian Institute of Space Science and Technology, India

Lean premixed combustion (LPC) holds great potential for reducing NOx emissions; however, it poses thechallenge of increased blowoff risk. This study comprehensively investigates swirl lean-premixed n-butane/
air flames, focusing on the differences between stable
flames and those nearing blowoff. Experiments employing Particle Image Velocimetry (PIV) were conducted
to analyze flow fields, while Detached Eddy Simulation(DES) modelling, incorporating the Flamelet Generated
Manifold (FGM) model and USC-Mech reduced chemicalmechanism, provided further insights. The results reveal
notable distinctions in the near blowoff flames, including alower high-temperature zone, enhanced heat loss due toflame-vortex interaction-induced low-temperature spots,
higher strain rates, and turbulence fluctuations influencing flame attachment, and the emergence of a Processing
Vortex Core (PVC) downstream. These findings highlightthe combined influence of fuel/air mixture ignition, PVC
instability, and flame attachment lift-off in lean blowoff
occurrence. Understanding these mechanisms is vital fordeveloping effective strategies to prevent or manage lean
blowoff, ensuring efficient and low-emission LPC systems.
Contact: rjvishnu15@gmail.com

Performance of flame surface density
and scalar dissipation rate based mean
reaction rate closures for fuel-leanhydrogen-air turbulent premixed flames
Vishnu Mohan, Frederick W Young, Umair Ahmed,
Nilanjan Chakraborty
Newcastle University, United Kingdom

Hydrogen is often identified as one of the future fuels to meet net-zero targets. However, the validity of
conventional mean reaction rate closures, which were
benchmarked for hydrocarbon-air flames with Lewis numbers close to unity, is yet to be assessed for lean H2-air
premixed flames. In the present work, mean reaction rateclosures based on flame surface density (FSD) and scalar dissipation rate (SDR) have been assessed based on
three-dimensional direct numerical simulations (DNS) of
statistically planar turbulent premixed hydrogen-air flamesat equivalence ratios of φ = 0.4 and 0.7 under different
turbulence intensities. It has been found that mixture
fraction dependence of the reaction progress variable hasa significant influence on the performances of FSD and
SDR closures and this effect is particularly strong for φ =0.4. The stronger preferential diffusion effects at smallerequivalence ratios negatively affect the FSD closure predictions, whereas the SDR closure is relatively less sensitive to the variations of equivalence ratio.
Contact: vishnu.mohan@newcastle.ac.uk

Dynamic Tracking of Surface Topology
in Turbulent Premixed Flames using
Machine-Learning
Hassan Farooq Ahmed, R Stewart Cant
University of Cambridge, United Kingdom

In turbulent premixed flames, the topological evolutionof the local flame surface can alter the balance between
flame area generation and destruction which in turn has
a profound influence on global flame propagation. In
this work, local annihilation of flame area resulting fromflame-flame interaction is used to classify the corresponding interaction topology obtained from a DNS datasetof a methane-air turbulent premixed flame. Principal
flame configurations are identified as reactant pocket,
product pocket, tunnel closure and tunnel formation. A
machine-learning classification algorithm is then trained
to map the previous point-based classification to local
surface interaction. With this method, local changes in
the flame surface that alter flame speed may be tracked
dynamically. The classification accuracy for complex
real-world interaction is 77% - while for clean isolated interaction events, the accuracy is near-perfect. Moreover,
the algorithm is shown to recognise key topological features of each principal configuration and works well for arange of turbulent intensities. The main advantage of thismethod is the potential for incorporating and subsequently tracking additional flow properties such as turbulent
straining and local displacement speed. The aim is to develop more robust burning and stretch rate models.
Contact: hfa27@cam.ac.uk

113

Track04 Turbulent combustion

Role of Dilatation in the Injection andRedistribution of Turbulent Kinetic
Energy in Premixed Reacting Flows

Arnab Moitro1, Alan R Kerstein2, Alexei Y Poludnenko1

University of Connecticut, United States, 272 Lomitas Road, Danville, CA
94526, United States

1

The nature of the flame effects on the surrounding
turbulent flow is one of the central open questions in turbulent combustion, as the flame can fundamentally alter
the dynamics of the turbulent cascade. In our prior work,
we have shown the ability of a flame to generate significant turbulent intensities on scales much larger than thecharacteristic flame width even in the absence of external
turbulent energy injection. Such flame-generated turbulence was observed in compressible regimes through theaction of a baroclinic torque. Here we present the first numerical evidence of pronounced turbulence generation by
the flame in low-speed regimes not by baroclinic torque,
but rather through flame-induced dilatation. We first characterize the properties of such turbulence by analyzing
data from DNS. The wavenumber scaling of the dilatation
spectrum is shown to be linked to the fractal dimensionof the flame front. This relation is then used to obtain the
spectrum of the kinetic energy injection rate, which is thenused to explain the observed kinetic energy spectra of
the flame-generated turbulence. The dependence of thestrength of turbulence generation on the flame density
ratio is also examined. Finally, we discuss the implicationsof these results for turbulent combustion modeling.
Contact: arnab.moitro@uconn.edu

On flame displacement speed variation
due to flame-flame interaction

Yuvraj Yuvraj1, Jen Zen Ho2, Mohsen Talei2, Swetaprovo
Chaudhuri1

University of Toronto, Canada, Canada, 2University of Melbourne, Australia,
Australia

1

Enhancement in the local flame displacement speed
due to flame-flame interaction has been reported in theliterature. Recently, models capturing this enhancement
as a function of parameters pertaining to the local flame
structure have been developed. However, these models
have been validated for statistically planar flames in isotropic turbulence. Additionally, local turbulent straining
and flame broadening strongly affects local flame displacement speed at zero local curvature, depending on
effective Lewis and Karlovitz numbers. Considering thatthe local flame displacement speed is a manifestation of
the local statistics, a fundamental question arises: to what
extent do the configuration and additional complexities

114



like shear flows govern the density-weighted local flame
displacement speed? To address this question, the current study investigates two DNS cases of freely propagating turbulent lean premixed hydrogen-air flames in a box
configuration at Lewis numbers 0.5 and 1, and a third DNS
case of turbulent methane-air jet flame at Lewis number
1. The local flame displacement speed was enhanced over
its laminar value at large negative curvatures in all configurations. On average, the flame surfaces are thickened
at the most probable regions (near zero curvature) compared to the strained laminar counterpart. The reasonsand implications of thickening on density-weighted local
flame displacement speed are explored.
Contact: y.yuvraj@mail.utoronto.ca

Differential diffusion modelling for LES
of a hydrogen-fuelled swirled burner withaxial air injection
Gioele Ferrante, Giacomo Abbasciano, Arvind Gangoli
Rao, Ivan Langella
Delft University of Technology, Netherlands

A swirled stabilized combustor with axial air injection(AAI) is analysed by means of large eddy simulation (LES)
with flamelet combustion model and presumed filtereddensity function (FDF) closure. A case employing a fuelblend of 75% CH4 and 25% H2 in volume is simulated togain insight on the reacting flow features and to validate
the model against in house experimental data. The analysis is extended to H2 /air combustion at the same power
setting to evaluate hydrogen effects on emissions andidentify criticality in flame stabilization. Two approaches
to include differential diffusion in the thermochemistrydatabase and at the resolved scales are tested. Results
reveal how fuel/oxidizer mixing plays a predominant rolein flame stabilization, temperature and emissions. In particular, axial air injection is observed to noticeably affectthe swirling flow field in the mixing tube and consequently
the flame-burning conditions. The inclusion of differential
diffusion modelling is observed to enhance mixing andmodify the equivalence ratio distribution at the entranceof the combustion chamber. Additionally, local reaction
rate variations on the flame, coupled with flame front curvature, are observed to influence the flame stabilization
location, local temperature and NOx emissions.
Contact: g.ferrante@tudelft.nl

19th International Conference on Numerical CombustionTrack04 Turbulent combustion

Large eddy simulation of a turbulent jet
ignition process of hydrogen lean mixture
with a super-rich pre-chamber
Haoming Gu, Fangsi Ren, Shinji Nakaya, Mitsuhiro TsueThe University of Tokyo, Japan

A super-rich-burn, quick-mix, lean-burn (SRQL) combustion strategy for hydrogen internal combustion engines using active pre-chamber is proposed to achieve
stable ignition under lean-burn conditions and mitigate
nitrogen oxide emissions resulting from high combustion
temperatures during hydrogen turbulent jet ignition (TJI),
simultaneously. To investigate the ignition and quenchingmechanisms in the strategy above, combustion behaviorsof the super-rich transient turbulent jet ignition process inglobally lean mixtures were simulated by Large Eddy Simulation (LES) using OpenFOAM. Dynamic sub-grid scalemodel and the Partially Stirred Reactor (PaSR) combustion
model were integrated into the simulation. The calculated
results for different nozzle diameters were analyzed andcompared with the experimental results in a Rapid Compression Machine (RCM). Simulation results showed the
reproducibility of the SQRL-TJI process in terms of the auto-ignition of the hot jet and the flame lift-off phenomena.
Based on the simulation results, the mixing process of hotjets was investigated, and the local Damköhler numbers’
behaviors over time were calculated quantitatively.
Contact: haoming.gu97@outlook.com

Track04-6 Turbulent combustion(6)
Chair: Michael E Mueller
Friday, May 10; 13:00 - 15:00; Room A

Manifold-based modeling of supersonicturbulent combustion: Direct inclusion ofhigh-speed effects
John Boerchers1, Hariswaran Sitaraman2, Michael E
Mueller1
Princeton University, United States, 2National Renewable Energy
Laboratory, United States1

the combustion model, these approaches still rely on the
low Mach number formulation of the manifold equations
and do not consider the direct influence of high-speed
effects on the enthalpy and its variation with mixture fraction. In this work, a truly high-speed manifold-based combustion model for nonpremixed combustion that directly
incorporates high-speed effects is proposed. The model
requires closure of the pressure variation and viscousheating terms, and an a priori study is performed using
high-fidelity data from a high-speed turbulent reacting
flow in a scramjet-like geometry to investigate these highspeed terms and their dependence on mixture fraction
and other flow parameters.
Contact: jb5027@princeton.edu

Numerical simulation of CH4/LOx
supercritical flame

Florian Monnier, Guillaume Ribert, Louis Duhem-Duvilla
CNRS & INSA de Rouen, France

The oxi-combustion of methane is studied by high-fidelity simulations in the context of liquid rocket engines.
The pressure thus exceeds the critical pressure of incoming fluids but stays below the critical pressure of water.
Methane and oxygen are injected at cryogenic temperatures in a splitter plate configuration that mimics a smallpart of a co-axial injector. Simulations are performed witha reduced chemistry containing 17 species and 44 reactions, along with a specific treatment for thermodynamics
and transport properties to address real-gas effects. The
resulting flame is stuck between two dense flows that
locally modify the turbulent kinetic energy. Consequently, the flame can split and experience different regimesof combustion: non-premixed, lean, and rich premixed.
Accordingly, species concentration varies with the flame
regime and OH is only found in regions poor in methane,contrary to H2O. For the latter, depending on the local
temperature, a part of it should be in liquid or even solid
phase meaning that additional modeling effort should be
performed in the future. Large-eddy simulations are also
conducted using a no-model assumption or the TFLES
approach for the subgrid species source term.
Contact: guillaume.ribert@insa-rouen.fr

Manifold-based models for turbulent combustion areusually derived in the low Mach number limit where pressure variation and viscous heating are assumed to be negligible. These low Mach approximations result in enthalpy
becoming a conserved scalar that varies linearly withrespect to mixture fraction. While approaches have beendeveloped for high-speed combustion that ensure a consistent thermodynamic state between the flow solver and

115Track04 Turbulent combustion

Study on soot oxidation and leakage in aturbulent non-premixed jet flame

Gandolfo Scialabba1, Antonio Attili2, Francesca Loffredo1,
Heinz Pitsch1

1
RWTH Aachen University, Germany, 2University of Edinburgh, United
Kingdom

Soot particle evolution in turbulent flames is complex
and involves a wide range of timescales, including theslow soot-formation processes and fast consumption
due to oxidation. Accurate modeling of the soot-chemistry-turbulence interactions is fundamental for the accurate prediction of soot emissions, but these interactions
are still not fully understood. Direct Numerical Simulation(DNS) is a key tool for the development of more accurate
predictive models. In this work, a new DNS of a three-dimensional temporally evolving turbulent non-premixed jet
flame is presented. The chosen configuration is specifically designed to study the later stages of soot evolution,
overcoming limitations seen in previous DNS studies ofsooting flames. A particular focus on events of soot leakage in the lean side of the flame (“Soot breakthrough”)
due to incomplete soot oxidation processes is posed. A
characterization of soot breakthrough and its correlation
with the gas-phase quantities, such as mixture fraction
and oxidation-relevant species, is provided. The presented DNS data is then compared with a previous DNS
study with a similar configuration where strong oxidation,
but negligible soot leakage, were obtained. Effects of finite-rate soot oxidation events on the evolution of sootparticles are discussed, together with some implications
for soot subfilter models in Large Eddy Simulations.
Contact: g.scialabba@itv.rwth-aachen.de

Influence of Turbulence on Soot
formation in Iso-octane Outwardly
Propagating Rich Unstable Flames

Takashi Ikeda1, Hiroaki Watanabe1, Ekenechukwu Chijioke
Okafor1, Ryoichi Kurose2, Toshiaki Kitagawa1
1

Kyushu University, Japan, 2Kyoto University, Japan

Soot formation in outwardly propagating iso-octane
rich turbulent flames was investigated by means of two-dimensional numerical simulation at a mixture equivalence
ratio of 1.4. The soot formation in the cusp area of the
turbulent flames was larger compared to that in the area
convex toward the unburned mixture. The soot inception
and surface growth processes at the cusp area were enhanced by an increase in the concentration of C2H2.
The cusp area had a negative flame stretch rate; incontrast, the convex area had a positive flame stretch
rate. Flame temperature in the negatively stretched cusp

116area decreased due to thermo-diffusive effects because
the Lewis number of the rich iso-octane flames was lessthan unity. Larger C2H2 concentration and soot formationin the cusp area were found to be caused by the decreasein the flame temperature due to the negative flame
stretch in this area.
Contact: ikeda.takashi.482@s.kyushu-u.ac.jp

Numerical assessment for turbulent
partially-premixed combustion using
reaction-diffusion manifold based model
reduction “on the fly”
Prashant Shrotriya, Robert Schießl, Chunkan Yu, Ulrich
Maas
Karlsruhe Institute of Technology, Germany

Partially-premixed combustion (PPC) often presentsa challenge for model reduction methods, because ana priori identification of types of combustion is needed.
Here, we use a generalized reaction-diffusion manifold(REDIM)-reduced chemistry approach to investigate such
mixed-mode flames, which overcomes the drawback of
the need of an a priori knowledge. To include the information about the combustion system, gradient estimates areprovided during the generation of REDIM, simultaneousto the solution of the conservation equations. An iterative
methodology is used in this work to provide the gradientestimates for REDIM generation. In this methodology,
reduced calculations are coupled with the generation
process of REDIM itself such that the manifold evolves
automatically according to diffusion-related information
provided by the combustion system. In this way, priorknowledge about the combustion system becomes minimal and no information is needed from a detailed system.
Large eddy simulations for Sydney turbulent PPC withinhomogeneous inlets is performed using the dynamic
thickened flame (DTF)-REDIM model. The good agreement between calculated and measured values for temperature, major and minor species mass fractions showsthat the method can produce realistic reduced models
also for systems with complex interactions of chemical
reaction, molecular transport and flow, like turbulent PPC.
Contact: prashant.shrotriya@kit.edu

19th International Conference on Numerical CombustionTrack04 Turbulent combustion

Controlling the resolved flame thicknessof diffusion flames in LES with filteredtabulated chemistry
Samuel Dillon1, Renaud Mercier2, Benoît Fiorina1
1

EM2C Laboratory, CNRS, CentraleSupélec, Université Paris-Saclay, France,
Safran Tech, Digital Sciences & Technologies Department, France

2

LES of turbulent non-premixed flames remains important for the design of novel combustion chambers.
A fundamental property of non-premixed flames is thatcharacteristic lengths are controlled by strain rates. Consequently, the LES mesh resolution in a turbulent flame
varies as a function of the local strain rate. A novel approach which aims at controlling the filtered reactive layer
size is proposed, irrespective of the local strain rate andmesh size. This approach is developed in the F-TACLES(Filtered tabulated chemistry for LES) framework. To ensure a robust application to diffusion flames, a new gradient-diffusion closure is proposed. A strategy which adapts
the local flame filter size is also proposed to control thereactive flame thickness. A posteriori tests are undertakenon 1-D counterflow diffusion flames and the 3-D turbulent
coaxial HYLON (Hydrogen Low-NOx) injector. Implementation of the gradient-law closure for the mixture fraction
equation proves to be a robust solution in conserving
scalar transport of the resolved mixture fraction. The
new variable filter size approach outperforms traditional
constant filter size cases in predicting the overall flame
shape. Since the variable filter uses an optimal filter size,
the resolved flame wrinkling is also increased.
Contact: samuel.dillon@centralesupelec.fr

Track04-7 Turbulent combustion(7)
Chair: Fabrizio Bisetti
Friday, May 10; 13:00 - 15:00; Room D

A generic multispecies combustion
regime identification for turbulent
nonpremixed flame simulations

Pascale Domingo1, Luc Vervisch2, Florian Kissel2,
Guillaume Ribert3

CNRS, France, 2INSA ROUEN NORMANDY, France, 3INSA ROUENNORMANDY, France

1

posed to the global regime indexes based on the gradientof reactants, and, to the most advanced indexes requiring
the computation of the local chemical explosive modes.
This novel method is based on four quantities examining
every chemical species present in the simulation in termsof their dynamics versus the spatial distributions of theconserved atomic mass fractions, and their chemical equilibrium conditions accounting for differential diffusion. The
atomic-space flame index is grounded on the fact that theatomic concentrations vary much less across premixed
and partially premixed flame fronts than across diffusion
flame-type reaction zones. The proposed methodology isverified in high-pressure triple-flames propagating arounda fuel pocket. The very thin reaction zones under highpressure make the distinction between the combustion
modes more challenging. The results confirm the potential of identifying the combustion regimes in the intimacy
of complex reaction zones with four parameters related tothe conservation of atoms.
Contact: luc.vervisch@insa-rouen.fr

Flame transition in a highly-lifted
premixed jet flame in a hot cross flow
Harikrishna Tummalapalli, Evatt Robert Hawkes
The University of New South Wales, Australia

We present a large-scale direct numerical simulation(DNS), with detailed chemistry, of a highly-lifted premixed
methane-air jet flame in a hot cross flow, which is relevant
to axially staged gas-turbine combustion systems. The
simulation features a jet Reynolds number of ~18,000 anda cross flow Reynolds number of ~29,000. The thermochemical parameters, except for pressure, closely match
those of practical axially staged combustors. In our setup, a premixed methane-air jet with an equivalence ratioof 0.7 is injected into a vitiated crossflow consisting of
combustion products from a methane-air mixture at anequivalence ratio of 0.5, under atmospheric pressure. We
analyse this DNS dataset to show flame transition fromautoignition to premixed flame propagation, and premixed
flame to diffusively supported ignition fronts. While theformer phenomenon is due to the interaction between the
autoignition kernels and counter-rotating vortex pair, thelatter phenomenon is to the accelerated autoignition of
the richer mixtures.
Contact: h.tummalapalli@student.unsw.edu.au

Flame stabilization and pollutant emissions are strongly sensitive to the local combustion regime and methods
have been discussed in the literature to determine, fromnumerical simulations, three-dimensional distributions ofcombustion modes. A complementary approach is pro-

117

Track04 Turbulent combustion

Numerical prediction of blow-out
in bluff-body stabilized turbulent
flames controlled by thermo-diffusive
instabilities

Simulation of attached and lifted swirlstabilised hydrogen–air flames
James C Massey, Nedunchezhian Swaminathan
University of Cambridge, United Kingdom

Andrea Gruber , Jonas T Aannestad , Samuel M Wiseman ,James R Dawson3
1

2

1

SINTEF Energy Research, Norway, 2Norwegian University of Science andTechonology, Norway, 3Norwegian University of Science and Technology,
Norway1

A Large-Eddy Simulation (LES) study of turbulent
flames blow-out taking place in a bluff-body burner is conducted. The present study, utilizing an OpenFOAM-based
standard solver for turbulent reactive flows, attempts topredict the blow-out behavior observed in experimental
investigations of turbulent premixed CH4-air and NH3/
H2/N2-air flames at fuel-lean conditions, and for identicalnominal flame properties [1]. In the experiments it was determined that, despite nominally-identical laminar flame
characterstics, blow-out occurred at burner velocities
differing by an order of magnitude for the different fuels.
Localized de-mixing of fuel and oxidiser, hydrogen enrichment of the leading points and subsequent global flamefront acceleration due to thermo-diffusive instabilities
cause a significantly-increased resilience to extinction of
the NH3/H2/N2-air flames. The physical rate-controlling
processes that lead to the observed order-of-magnitudedifference in blow-out limits are not conventionally taken
into account in turbulent combustion models due to wellknown intrinsic limitations. In the present work, utilizing a
Partially-Stirred Reactor (PaSR) model jointly with standard LES formulation and unity Le-number molecular transport model, it is shown that the selected model combination is able to accurately capture the blow-out limit for
the CH4-air flame but fails to do so for the NH3/H2/N2-air
flame. Furthermore, it is also observed that the LES/PaSR
predictions of blow-out in the hydrogen-enriched flames
can be improved by including a sub-unity Lewis number
formulation in the molecular transport model.
[1] S.M. Wiseman, M. Rieth, A. Gruber, J.R. Dawson and J.H.
Chen, “A comparison of the blow-out behavior of turbulent premixed ammonia/hydrogen/nitrogen-air andmethane–air flames”, Proceedings of the Combustion
Institute, vol. 38, pp. 2869–2876 (2021).
Contact: andrea.gruber@sintef.no118

Hydrogen is gaining significant attention, since it is acarbon free fuel. Hydrogen has different characteristics
compared to conventional hydrocarbon based fuels, ashydrogen is much lighter and this causes increased hydrogen diffusion compared to thermal diffusion. However,combustion systems have significant challenges withperfectly premixed hydrogen combustion, due to theincreased risks of flashback and thermo-acoustic instabilities. Partially premixed combustion is therefore morefeasible, but the method of injection of hydrogen needs tobe carefully considered to mitigate nitrogen oxide based
emissions. A recently developed laboratory scale burnerthat uses co-axial swirlers ensures quick mixing betweenhydrogen and air. Altering the mass flow rates at a constant equivalence ratio also leads to different flame archetypes being observed. This work aims to simulate both
flame configurations and show comparisons for the flow
field and flame shapes with measurements. The interactions between the flow and mixing fields on the flamestabilisation will also be further explored. The flames are
simulated using a presumed joint probability density function approach with tabulated chemistry using OpenFOAM.
Contact: jcm97@cam.ac.uk

Numerical investigation on ignition
characteristics of an igniting underexpanded hydrogen jet
Hesheng Bao, Jeroen van Oijen

Eindhoven University of Technology, Netherlands

The ignition characteristics of an under-expanded hydrogen jet in a hot ambient atmosphere, corresponding todirect-injection compression-ignition engine conditions,
are numerically investigated. Such a hydrogen jet involves
significant preferential diffusion, and raises numericalchallenges. In the current study, a novel Flamelet Generated Manifold (FGM) method, namely the Projected-FGM,
applying an ideal parameterization that spans the local
tangential space of the manifold is adopted for combustion modeling and coupled with large-eddy simulation(LES). As a reference, an LES with direct chemistry integration that discards the subgrid turbulence–chemistry interaction is performed. The resulting combustion evolutionof the under-expanded hydrogen jet is first compared toavailable experimental results (Yip et al. International Journal of Hydrogen Energy 45.56 (2020): 32562-32578), and19th International Conference on Numerical CombustionTrack04 Turbulent combustion

then analyzed in detail using a variety of approaches. The
currently applied Projected-FGM method does not depend
on a specifically optimized linear combination of species
mass fractions as progress variable, but it solves ordinarytransport equations for a few species, which are subsequently projected onto the manifold. It can be applied toany manifold method.
Contact: h.bao@tue.nl

Track04-8 Turbulent combustion(8)
Chair: Andrew Aspden
Friday, May 10; 15:20 - 17:20; Room D

Large-Eddy Simulations of Fuel Jet
Combustion Assisted by the Cylindrical
Hot Surface

Sayop Kim1, Tonghun Lee2, Kenneth S. Kim3, Chol-Bum M.
Kweon3, Je Ir Ryu1
New York University Abu Dhabi, United Arab Emirates, 2University of
Illinois Urbana-Champaign, United States, 3Army Research Laboratory,
United States

1

This study delves into ignition and flame dynamics witha cylindrically structured hot surface impact incorporated. Previous studies focused on the flat-wall hot surface
interacting with fuel spray, but the effects of cylindricalsurfaces on fuel-air mixing and ignition have not been
fully understood. Using high-fidelity large-eddy simulations (LES), this study reveals physiochemical aspects ofreactive mixture elements impinging on an electronically
activated glow plug structure. The analysis investigates
how the structure enhances fuel-air mixing and affects
the low-temperature chemistry of the fuel. To this end,
free spray and non-thermal deposit cases are included toinspect the mixing impact. Three different impacting distance are included to differentiate the mixing intensity byaltering the impinging spray inertia. Five different electric
voltage inputs are also considered to examine the thermally assisted ignition process. Results indicate that thecylindrical structure impedes flow, reducing its inertia andincreasing flow residence time. Also, a meaningful Coandă
effect is also discovered due to the circular wall structure. Such a mixing enhancement potentially serves as aflame-holding mechanism. In addition, varying the input
voltage significantly affects ignition timing. It is an intriguing feature to identify a non-monotonic ignition delay pattern with lower voltages. The detailed analysis discovers
the importance of the negative temperature coefficient(NTC) driven low-temperature chemistry (LTC). The further
detailed analysis uncovers detailed insights into the phys-

iochemical properties of reactive mixture that contributeto the exothermic ignition pocket formation.
Contact: sayop.kim@nyu.edu

High-dimensional FGM/ResNet modelingof turbulent spray combustion: Effectsof evaporation heat loss and combustion
scalar correlation
Dong Wang, Haixiao X. Wang, Min X. Zhang, Ruixin X.
Yang, Zhi X. Chen
Peking Univeristy, China

In the stratified or partially premixed piloted jet flames,
previous experimental and direct numerical simulation(DNS) studies have signified a strong subgrid-scale correlation between mixture fraction and progress variable. In
the framework of large-eddy simulation (LES) and flamelet-generated manifolds (FGM) approach, a general joint
probability density function (PDF) method is proposed
to characterize subgrid correlations. To pave the way forhigh dimensional tabulation modeling, a deep residual
network (ResNet) is trained, dramatically reducing thememory footprint of tabulation. The Message Passing Interface (MPI) shared memory technique is applied to load
the 6-dimensional chemical table during parallel computations. Application of LES to a partially pre-vaporizedethanol spray flame demonstrates good agreement withexperimental results. Consideration of the subgrid correlation results in a noticeable improvement in temperature
prediction. Calculations using ResNet show a notable consistency with those using chemical tables. Visualizationof enthalpy highlights the significance of non-adiabatic
tabulation in modeling liquid fuel combustion. The impactof the source term due to evaporation in the transport
equation of the progress variable is validated. The correlation coefficient significantly influences the chemical reaction rate in the posterior investigation. The subgrid-scaleinteraction between liquid fuel evaporation and subgrid
correlation is elucidated.
Contact: sy1805217@buaa.edu.cn

Large-eddy simulation of high-pressureauto-igniting hydrogen injections using
tabulated chemistry
Alessandro Ballatore, Jeroen van Oijen
Eindhoven University of Technology, Netherlands

Hydrogen has been labeled for a long time as thefuel of the future due to its carbon-free combustion andthe ability to achieve high energy efficiency. The unique119Track04 Turbulent combustion

thermo-physical properties of hydrogen can facilitate thedesign of a highly efficient internal combustion engine(ICE). In particular, direct injection (DI) of hydrogen, aside
from enabling high volumetric efficiency, avoids possibly
undesired combustion-related phenomena such as engine
knock. However, due to its low density, hydrogen requires
high injection pressures to fully penetrate in the cylinder.
In this work, we study the combustion process that
occurs in high-pressure DI of hydrogen by means oflarge-eddy simulation with tabulated chemistry, including
preferential diffusion. First, the modelling is applied tohydrogen jets in hot air environment for validation against
experiments in literature. Then, we investigate different
auto-igniting hydrogen jets in a fixed-volume chamber
under argon-circulated conditions. In particular, we focus
on the effect of ambient temperature and oxygen concentration on ignition delay, heat release rate and flame
dynamics.
Contact: a.ballatore@tue.nl

Flame structure and stabilisation
mechanism of a high-pressure hydrogenmicromix combustor
Thomas Howarth1, Mark Picciani2, Edward Richardson3,
Marcus Day4, Andrew Aspden5

1
RWTH Aachen University, Germany, 2Sunborne Systems Ltd., United
Kingdom, 3University of Southampton, United Kingdom, 4National
Renewable Energy Laboratory, United States, 5Newcastle University, United
Kingdom

A high-pressure hydrogen micromix combustor has
been investigated using direct numerical simulation withdetailed chemistry to examine the flame structure andstabilisation mechanism. The configuration of the combustor was based on a NASA design, using numericalperiodicity to mimic a large square array. A precursor simulation of an opposed jet-in-crossflow was first conducted
to generate appropriate partially-premixed inflow boundary conditions for the subsequent reacting simulation. The
resulting flame can be described as an essentially-lean
inhomogeneously-premixed lifted jet flame. Five mainzones were identified: a jet mixing region, a core flame,a peripheral flame, a recirculation zone, and combustion
products. The core flame, situated over the jet mixing region, was found to burn as a fast thin premixed flame andis responsible for 85% of total fuel consumption, whereas
the peripheral flame shrouded the core flame and burned
at very lean conditions. It was shown that turbulent flame
propagation was an order-of-magnitude too slow to stabilise the flame at these conditions. Stabilisation was identified to be due to ignition events resulting from turbulent
mixing of fuel from the jet into mean recirculation of heat.
Around the location where ignition was first possible, iso-120

lated events were observed, which developed into rapidly
burning flame kernels that were blown downstream by
the bulk flow. Further downstream, near-simultaneous
spatially-distributed ignition events were observed, whichappeared more like ignition sheets.
Contact: t.howarth@itv.rwth-aachen.de

Soret effect modelling in flamelet-based
LES with presumed FDF for lean premixedhydrogen flames
Alessandro Porcarelli, Gioele Ferrante, Ivan Langella
Delft University of Technology, Netherlands

Soret effect modelling is included for the first time in
the framework of turbulent large eddy simulations (LES)
with flamelet-based combustion model and presumed filtered density function (FDF) closure for lean premixed hydrogen flames. Preferential diffusion effects are accounted at the thermochemical level with a constant non-unity
Lewis number approach, and the diffusive transport ofthe controlling variables in the LES is corrected accordingly. Within this framework, Soret effect contribution is
included on both the diffusive transport of species at thethermochemical level and on the diffusive transport correction of the LES controlling variables. The influence ofincluding or excluding thermal diffusion in the modellingis assessed on a turbulent premixed hydrogen flame in aslotted burner configuration, where favourable conditions
for the growth of thermo-diffusive instabilities are established. Results show that, when Soret effect is modelled,
the local equivalence ratio redistribution and its couplingwith flame front curvature due to preferential diffusion
effects are enhanced, and thus a further local increase ofreaction rate is observed in correspondence of resolved
positively-curved flame fronts. This ultimately affects themacroscopic flame topology, as it triggers an overall increase of turbulent flame speed and thus a decrease offlame jet height.
Contact: a.porcarelli@tudelft.nl

Modelling of Spark Ignition Process in
High-speed Turbulent Flows using Large
Eddy Simulation Based on Strained
Flamelet Generated Method
Fangsi Ren, Shinji Nakaya, Mitsuhiro Tsuethe University of Tokyo, JapanDue to environmental concerns, lean combustion technology has been widely implemented in spark-ignited in-19th International Conference on Numerical CombustionTrack04 Turbulent combustion

ternal combustion engines. In order to enhance the flame
propagation under lean conditions, turbulent flows are
introduced into cylinders, which leads to unstable ignition
processes. This study presents a numerical investigationof spark ignition in lean mixtures under turbulent conditions via Large Eddy Simulation, incorporating a spark discharge model to reproduce the discharge channel behaviors from the calculated electric fields. A strained Flamelet
Generated Manifold (FGM) approach was used to reducethe computation cost. Simulations were validated with theresults of experiments on a rapid compression machine.
Approaches to reduce the computation and interpolation
costs in the FGM model were used while considering theaccuracy. Results indicated an accurate representation ofdischarge channel behaviors and motions, including shortcircuits and restrikes aligning with the experimental data.
Flame kernel initiation behaviors, including fragmentationand local quenching effects, were observed and validatedwith OH* chemiluminescence images from the experiments.
Contact: ren-fangsi@g.ecc.u-tokyo.ac.jp

121Track05 Combustion dynamics and instabilities

Track05-1 Combustion dynamics
and instabilities (1)Chair: Abhishek Lakshman Pillai
Wednesday, May 8; 10:40 - 12:40; Room E

Dynamics of hydrodynamically unstablepremixed flames in a gravitational field
Kaname Matsue1, Moshe Matalon2

1
Kyushu University, Japan, 2University of Illinois at Urbana-Champaign,
United States

Dynamics of hydrodynamically unstable premixed
flames with the composite effect of Darrieus-Landau and Rayleigh-Taylor instabilities is investigated.
We study the Sivashinsky equation describing time evolution of flame fronts under the small gas expansion assumption and apply the bifurcation theory to extracting a
global picture of physically (and nonlinearly) stable flame
morphology in various properties of combustible mixture
and gravitational environment.
We will see, in the presence of gravitational parameter,(de)stabilization of flame fronts, as well as rich bifurcation
structure like hysteresis and splitting/merging behavior of
pulsating fronts by means of Hopf bifurcations.
We also investigate the corresponding flame morphology with finite thermal expansion parameter through thehydrodynamic model derived from large activation energy
asymptotics, which will provide physically relevant flame
morphology observed in the Sivashinsky dynamics.
Contact: kmatsue@imi.kyushu-u.ac.jp

Analysis of intrinsic flame instabilities
based on entropy generation mechanisms
Daniya Zhumabayeva, Stewart Cant
University of Cambridge, United Kingdom

Intrinsic flame instabilities, including hydrodynamic andthermodiffusive instabilities, have been analysed based on
the statistics of entropy generation mechanisms obtainedusing Direct Numerical Simulations. The simulations werecarried out for two-dimensional laminar premixed planar
methane-air flames, with varying amounts of hydrogen122addition up to 100% by volume. The mechanisms of entropy generation were analysed based on reversible andirreversible contributions resulting from heat conduction,
viscous dissipation, mass diffusion, and chemical reaction.
Both qualitative and quantitative methods were used to
identify features of the unstable flames. The statisticalrange of the data dispersion in all entropy generation
terms showed periods of growth and reduction, potentially signalling a saturation mechanism. The spatial distribution of all entropy generation terms, except the term
due to viscous dissipation, showed the ability to capture
the flame front evolution, with some terms indicating the
growth and reduction of reactant and product cusps. For
the reversible terms, two distinct regions of positive andnegative entropy generation rates were observed, while
the irreversible terms contributed only positively to thetotal entropy generation rate. The probability distributions
reveal the dominant contribution of the reversible term
due to the flux of entropy diffusion to the total entropy
generation rate.
Contact: dz295@cam.ac.uk

intrinsic instabilities of premixed NH3/H2/
air spherical flames under various gravity
conditions
Jian Zheng, Haiou Wang, Kun Luo, Jianren Fan

ZheJiang University, China

Blending hydrogen into ammonia as a carbon-freefuel has attracted increased attention. However, current
understanding of the intrinsic instabilities in premixed
NH3/H2/air flames is limited. In the present work, premixed NH3/H2/air spherical flames were performed using
direct numerical simulation (DNS). The simulations wereconducted under various gravity conditions for the firsttime to highlight the significant role of Rayleigh-Taylor(RT) instability. A parametric study of spherical flames
was performed for different fuel compositions, from pureammonia to pure hydrogen, equivalence ratios (0.3 to 1.0)
and pressures (1 bar to 10 bar). The temporal evolutionof spherical flame fronts was investigated in this study,
with a particular focus on the flame morphology. The
flame displacement speed and its dependence on flame
stretch were discussed in detail. The interaction between

19th International Conference on Numerical CombustionTrack05 Combustion dynamics and instabilities

Darrieus-Landau (DL) instability, thermal-diffusive (TD)instability and Rayleigh-Taylor (RT) instability was studied
to give a comprehensive understanding of the intrinsic
instabilities in premixed NH3/H2/air flames.
Contact: wanghaiou@zju.edu.cn

A numerical study of premixed laminarammonia/hydrogen/air flames: ananalysis of intrinsic flame instabilities

Ilya Morev, Parsa Tamadonfar, Shervin Karimkashi, Ossi
Kaario, Ville Vuorinen
Aalto University, Finland

Blending ammonia with hydrogen may offer a way tocontrol the combustion properties of such fuel mixtures.
It is well-known that due to the high diffusivity of hydrogen, hydrogen-containing flames are subject to strong
thermo-diffusive instabilities, which results in a significant
increase in flame consumption speed. To assess the susceptibility of ammonia/hydrogen/air mixtures to intrinsic
flame instabilities, linear dispersion analysis is conducted
for a wide range of ammonia/hydrogen blending ratios
and equivalence ratios at atmospheric pressure and temperature of 298 K. It is found that mixtures with almost
equal molar fractions of ammonia and hydrogen exhibit
higher normalized maximum growth rates than purehydrogen at the same equivalence ratios. Following thelinear growth phase, four cases are simulated to reach afully developed flame front for pure hydrogen and 50:50
ammonia/hydrogen blend and equivalence ratios of 0.5
and 0.7. The resulting increase in the consumption speed
compared to the laminar flame speed of the fuel blend
with an equivalence ratio of 0.5 is approximately 4, whereas for pure hydrogen, it is around 2.5. This indicates thatthe overall effect of intrinsic instabilities appears to belarger for this blend, compared to the pure hydrogen case,which also agrees with linear dispersion analysis results.
Contact: ilya.morev@aalto.fi

Numerical Analysis of Thermodiffusive
Instabilities in Fuel-Flexible MethaneHydrogen Industrial Burner Applications

S. Nerzak, K. Niemietz, M. Vivenzo, L. Berger, T. Lehmann,
M. Gauding, H. Pitsch
RWTH Aachen University, Germany

The high energy and heat demand of many industrial
sectors, e.g., steel production and processing, combinedwith the need for drastic carbon dioxide emission reductions, requires a transition from fossil fuel industrial burn-

ers to novel energy systems in the near future. One widely
discussed approach is the utilization of hydrogen. Sincehydrogen supply is still limited, industrial burners must
be capable of fuel-flexible operation while reducing emissions. However, hydrogen addition to methane strongly
influences flame characteristics due to thermodiffusive
instabilities.
This study investigates how these instabilities affectthe flame in fuel-flexible burners using Large Eddy Simulations (LES). To this end, the model by Regele et al.
(Combust. Flame, 160(2):240–250, 2013) is implemented
in OpenFOAM. The model is extended for methane-hydrogen combustion to account for instabilities at various
operating points including different fractions of hydrogenin the fuel mixture. Subsequently, the model is validated
using laminar and turbulent direct numerical simulations(DNS) and experimental data.
Finally, the combustion model is applied to a fuel-flexible industrial burner with complex geometry. Specific features of the burner are the variable hydrogen content in
the fuel as well as staging within the mixing unit. The aim
is to understand the effect of thermodiffusive instabilities
in a realistic application at different operating conditions.
For this, temperature distributions, NOX emissions, andflame stability limits are analyzed.
Contact: s.nerzak@itv.rwth-aachen.de

Track05-2 Combustion dynamics
and instabilities (2)Chair: Hong Im
Wednesday, May 8; 13:30 - 15:10; Room E

Numerical investigation in canonical flat
V-shape propagative reactive fronts
Zakaria Bazhar, Vincent Robin, Zakaria Bouali
ISAE-ENSMA / Institut Pprime, France

To prevent accidents related to hydrogen utilization, it
is crucial to enhance our understanding of the early stageof reactive front accelerations. In this context, we propose
a canonical numerical setup to investigate the mechanisms involved in the interaction of two reactive fronts,
which may result in sudden accelerations of flames or auto-ignition fronts.
The proposed configuration, designed to facilitate
physical analysis, requires meticulously controlled initialconditions - a challenge often difficult to overcome inpractical experiments.
The investigation focuses on low Mach interactions
and is conducted using the DNS solver – PeleLMeX-,

123Track05 Combustion dynamics and instabilities

which integrates Adaptive Mesh Refinement (AMR). The
initial condition is crafted using a reduced chemical mechanism and the CANTERA library through laminar flame
simulations or a series of homogeneous reactor computations. These preliminary calculations provide the initial
temperature fields yielding a constant propagation speedof reactive fronts.
The studied configuration is 2D, and the two impacting reactive fronts are flat, resulting in a V-shaped front
where the collision angle serves as a crucial parameterin the analysis. As anticipated, the initially flat V-shape ofthe fronts evolves over time due molecular diffusion interactions. The curvature of the front formed at the point of
impact gradually adjusts, in some cases leading to local
accelerations.
This study aims to provide new insights into the effects
of reactive front properties (such as initial propagation
speed, collision angle, etc.) on the propagation dynamics
and accelerations.
Contact: zakaria.bazhar@ensma.fr

Characteristics of transverse flame
describing functions of slot and Bunsen
flames at large amplitudes
Juhoon Son, Dong-hyuk Shin

Korea Advanced Institute of Science and Technology, Korea

In this study, G-equation simulations were conductedto characterize the transverse flame describing functions(FDFs) of slot and Bunsen flames under imposed transverse velocity fluctuations across various frequencies.
The simulations were validated by analytical models at
low amplitude conditions: longitudinal acoustic forcingof Bunsen flames and transverse acoustic forcing in slot
flames. Simulations are conducted with a mean transverse velocity as the transverse FDFs are zero without
the mean transverse velocity due to flame symmetry. For
slot flames, the FDF gains asymptotes to zero at low frequencies and increase right after. Still, the overall envelop of the gains decreases with frequency, illustrating atypical low-pass filter behavior. At large amplitudes, theFDF gains increase with larger than the low amplitudeconditions. Bunsen flames displayed a similar trend butwith notably lesser gain magnitudes. The small gain is
attributed to the different mean flame shapes, which arelinked to heat release fluctuations. Understanding thedifference in gain of FDFs is crucial for comprehending
flame dynamics related to transverse acoustic effects. A
comprehensive FDF modeling including both longitudinal
and transverse forcing are necessary to predict combustion instability.
Contact: Juhoon.son@kaist.ac.kr

124

Effect of central recirculation zone on the
instability growth in a V-shaped swirlingflame
Qiuxiao Wang, Xi Xia, Fei Qi

Shanghai Jiao Tong University, China

This paper presents a numerical and theoretical study
on the instability growth in a V-shaped swirling flame, with
an emphasis on the effect of varying central recirculation
zone (CRZ). First, the basic unsteady flame and flow characteristics are studied using large eddy simulation (LES)
with the flamelet generated manifold (FGM) model. The
resultant velocity profiles, flame structures, and vorticity
distributions show good agreement with the corresponding experimental data, confirming the validity of the numerical approach. Then, a linear spatial stability analysis
is performed based on the simulated mean flow to study
the growth of small disturbances. With the CRZ size varied through tuning the equivalence ratio (φ), the growthrate of axisymmetric disturbance shows a decreasing
trend with increasing CRZ size, whereas the growth rateof asymmetric disturbance increases with the CRZ size.
By further analyzing the source terms in the Reynold-Orr
equation, we find that the growth of axisymmetric disturbance is dominated by the axial velocity shear, whereas
the growth of asymmetric disturbance is governed by the
combined effects of axial and azimuthal velocity shears.
Contact: xiaxiss@sjtu.edu.cn

Vorticity transport of the precessing
vortex core in a premixed swirling flame
Qiuxiao Wang, Xi Xia, Fei Qi

Shanghai Jiao Tong University, China

This work numerically explores the mechanism governing the intensity of the precessing vortex core (PVC)
in a premixed swirling flame of the helical mode. Largeeddy simulation (LES) together with the flamelet generated manifold (FGM) model is employed to understand the
dynamical interaction between the spiral flame surface
and flow field. The validation of the numerical approach is
performed based on comparisons of the simulated velocity field and flame structures with the experimental results.
To quantify the local intensity of the PVC, the circulation,
Γ, is computed in the plane perpendicular to the PVC tube
axis. We find that |Γ| first increases along the PVC winding direction and then decreases upon reaching a peakvalue. To explain the variation trend of |Γ|, vorticity transport analysis is performed within a local control volume
enclosing the PVC element. The results reveal that both
vortex stretching/tilting and baroclinic torque contributeto vorticity growth in the PVC, whereas thermal dilation

19th International Conference on Numerical CombustionTrack05 Combustion dynamics and instabilities

and vorticity diffusion cause the PVC intensity to decay.
This understanding supplements the existing knowledge
regarding the formation and spatial development of PVC
in swirl combustion.
Contact: xiaxiss@sjtu.edu.cn

Track05-3 Combustion dynamics
and instabilities (3)Chair: James Dawson
Wednesday, May 8; 15:30 - 17:10; Room E

The dynamics of a cellular flame
deformation from the head on interaction
with an expansion wave
Hongxia Yang1, Kevin Cheevers2, Andrzej Pekalski3, Matei
Ioan Radulescu2
1

University of Ottawa, Canada, Canada, 2University of Ottawa, Canada,
Shell Global Solutions, United Kingdom

3

We address the problem of cellular flame deformation
after a head-on interaction with an expansion wave. Our
focus is on studying the wrinkling behavior of hydrogen-air flames and examining the influence of the Lewis
number on the dramatic flame deformation resulting fromthe interaction. This problem is addressed numerically bydirect numerical simulations of the reactive Navier-Stokes
equations in 2D, using a single-step Arrhenius law. The
physical mechanism of deformation is established to bethrough the baroclinic vorticity production mechanism,augmented by the gas expansion during deformation. It
is found to be similar to but more efficient than the flame
deformation by the passage of a shock with the same
overpressure (Yang and Radulescu, JFM 2022), due to thelonger residence of the flame in the region of vorticity
deposition. The effect of the lower Lewis number for lean
flames was found to provide an increase in flame deformation and burning rate enhancement as compared to
stoichiometric unity Lewis number flames. This is due tothe higher propensity of curved flames to further deform
through the thermal-diffusion instability mechanism. The
flame deformation dynamics were monitored for different expansion strengths and distances from the flame,
originating from either the burned or unburned side. Nonlinearity, and the competition between pressure gradientmagnitude and residence time were found to play subtle
roles in the deformation dynamics. A model was proposed
to predict the evolution of the flame burning rate for arbitrary expansion wave and flame properties.
Contact: hyang6@uottawa.ca

Influence of numerical damping on
the prediction of high-frequency
thermoacoustics and mitigation strategies
for LESJonas Eigemann1, Christian Beck2, Andreas M. Kempf1
1

University of Duisburg-Essen, Germany, 2Siemens Energy AG, Germany

Thermoacoustic instabilities limit the operating rangeof gas turbine combustors, impeding further efficiency
gains and emission reductions. The prediction of instabilities can be achieved with compressible large-eddy simulations (LES), which considers all physical mechanismsof thermoacoustic processes. Notably, the numericalmethods employed in LES damp the propagation of pressure waves, leading to a non-physical loss in amplitude
over time and space. The numerical damping depends
on the spatial and temporal resolution of the waves,leading to higher damping for higher frequencies. In thiswork, the impact of numerical damping on the predictionof high-frequency thermoacoustics is studied. Highly-resolved compressible, reactive LES of a self-excited
high-frequency atmospheric model combustor are carriedout. The results show that higher numerical damping
reduces the limit-cycle amplitudes significantly, and caneven stabilize the case, resulting in no HFI prediction. The
influence on mode shape and frequency of the unstable
acoustic mode is small for the considered cases, if HFI occurs. The results indicate that the numerical damping acts
as a suppression of HFI. Possible mitigation strategies
to recover the prediction of HFI on meshes with higher
damping are discussed and a method based on the amplification of thermoacoustic flame response is presented.
Contact: jonas.eigemann@uni-due.de

Combustion Characteristic Analysis of theDual Combustion Ramjet Engine
Min-Seon Jo, Bu-Kyeng Sung, Seung-Min Jeong, JeongYeol Choi
Pusan National University, Korea

The investigation of combustion characteristics in theDual Combustion Ramjet (DCR) engine is undertaken
through a numerical study employing a Large-Eddy Simulation (LES) approach, with detailed chemistry and species conservation equations. Two distinctive combustion
modes are discerned under the same inflow condition but
with varying initial conditions. In supersonic shear layer
combustion, the initial condition is given 1,200K air. The
thermally choked mode is observed in 3,200 K air, whichis artificially assumed to have increased the initial temperature due to certain non-ordinary events. These modes

125

Track05 Combustion dynamics and instabilities

Track05-4 Combustion dynamics
and instabilities (4)emerge due to compressibility effects, turbulent motion,pressure waves, and heat addition. The findings imply thatmode control in the DCR is attainable through the strategic introduction of critical heat addition or ignition sources.
Contact: astro0724@pusan.ac.kr

Flamelet modeling of curvature effects
on NOx formation in thermodiffusively
unstable premixed hydrogen flames atelevated-pressure conditions
Xu Wen1, Lukas Berger2, Alessandro Parente3, Heinz
Pitsch2

University of Science and Technology of China, China, 2RWTH Aachen
University, Germany, 3Universite Libre de Bruxelles, Belgium

1

Fuel-lean premixed hydrogen flames are thermodiffusively unstable and burn in cellular structures due tostrong differential diffusion of hydrogen. Pressure promotes the thermodiffusive instabilities due to the increase
in Zeldovich number and the relevant reaction pathways.
As the local stochiometry and temperature correlate withthe thermodiffusive instabilities, the NOx formation mechanism is expected to be complicated in fuel-lean hydrogen flames at elevated-pressure conditions. Furthermore,
the thermodiffusive instabilities correlate with the curvature of the flame front, the NOx formation are expected
to be affected by the curvature. To consider the effectsof curvature, an extended flamelet tabulation method
based on the composition space model (Scholtissek etal., CNF, 2019) is proposed. The performance of the composition space model in predicting the NOx species isevaluated using a posteriori} simulations. The simulation
results obtained with the composition space model will becompared with the reference DNS data and the flamelet
model proposed by Regle et al.~(CNF, 160 (2013) 240-250),
in which the curvature is considered by varying the equivalence ratios. We will focus on thermodiffusively unstablepremixed hydrogen flames at elevated-pressure condition(8\,atm) for different equivalence ratios.
Contact: xu.wen@ustc.edu.cn

Chair: Michael Gauding
Thursday, May 9; 09:50 - 12:30; Room D

Bifurcation dynamics of lean hydrogen
flames in narrow channels
Alba Domínguez-González1, Miguel P. Encinar2, Daniel
Martínez-Ruiz1

Universidad Politécnica de Madrid, Spain, 2Universidad Carlos III de Madrid,
Spain

1

Very lean hydrogen-air mixtures confined in slenderchannels have been recently found to produce bistable
fronts, either circular or double-cell flames. In particular,
these two stable configurations arise for the same combination of controlling parameters (equivalence ratio, channel size and thermal conductivity) in the limit of fuel-lean
mixtures and non-negligible conductive heat losses. In
this study, numerical experiments are performed to detailthe unsteady evolution that forms either one structure or
the other during a particular ignition transient and provide
a satisfactory explanation of their symmetry-breaking dynamics.
We offer causality analyses based on the initial temperature profiles (hot-region distribution and peak value) andsubsequent expansion of the flow field, which prescribe
the early growth of the flame front leading to different
curvatures and sizes of the kernel. These processes control the evolution into each of the canonical structures
owing to the underlying physics. Specifically, differencesin the local convective effects and interactions between
fronts have been identified as the key causes to produce
each of the final-stage bistable fronts.
In fact, frequently found fragmentation of flames cannot ensure the formation of double cells, which require
additional reorientation dynamics of the subdivided partsto achieve their coupling. The reorientation process is
produced through asymmetric seeding of flame fragments
or to the interaction with neighboring structures, which
are particular events very dependent on the ignition configuration.
Contact: daniel.mruiz@upm.es

126

19th International Conference on Numerical CombustionTrack05 Combustion dynamics and instabilities

LES of wet hydrogen combustion in acounter-current nozzle configuration
Agnieszka Wawrzak, Artur Tyliszczak
Czestochowa University of Technology, Poland

Employing Large Eddy Simulations (LES), we investigate nitrogen-diluted hydrogen flames in a counter-current configuration in which a fuel nozzle is embedded in alarger annular nozzle sucking the fluid from the surrounding of the fuel jet. Such an injection system produces acounterflow in the vicinity of the nozzle, which is beneficial for triggering global instability. The research explores
the interactions between global instability phenomenon,
fuel-oxidizer mixing, and flame-stabilization mechanism,crucial for enhancing technical efficiency and environmental sustainability. The flames are ignited through theenergy deposition model. The primary focus is on the impact of spark position, suction strength, and water-vapor
dilution on the flame stabilization mechanism. During thetransition to global instability, toroidal structures and sidejets emerge, enhancing fuel-oxidizer mixing and simultaneously preventing the flame attachment to the nozzle.
The study also highlights the impact of water-vapor dilution on ignition and flame stabilization following the current trend of wet combustion technique. The water-vapor
presence hinders ignition and contributes to lifted flamestabilization. The coexistence of global instability and water-vapor dilution offers novel insights into flame stabilization mechanisms, presenting opportunities for optimizing
combustion systems and advancing safety and efficiency.
Contact: agnieszka.wawrzak@pcz.pl

LES of an excited hydrogen flamestabilised by cylindrical and star-shaped
bluff bodies
Lena Caban, Agnieszka Wawrzak, Artur Tyliszczak
Czestochowa Universiity of Technology, Poland

This research focuses on the dynamics and stability ofa nitrogen-diluted hydrogen flame formed downstream
a bluff body with a cylindrical and star-shaped wall positioned in an oxidiser duct. To intensify the mixing process
an excitation is imposed on an oxidiser mass flow stream.
The study employs the Large Eddy Simulation (LES) method, providing detailed insights into the intricate physics ofunsteady flow. The main goal of the research is to assess
the impact of bluff-body shape and excitation parameters (frequency, amplitude) on the formation of large andsmall-scale vortical structures and to analyse how theiralteration influences flame parameters (flame shape, fuelconsumption, temperature and species distribution). Wefound that in the case of the cylindrical bluff body, themixing process is driven by periodically generated large
toroidal vortices resulting from Kelvin-Helmholtz instability. Applying the excitation enhances the formationof these vortices and leads to an intense transport ofoxidiser into the recirculation zone. On the contrary, thestar-shaped bluff body induces azimuthal disturbancesthat prevent the formation of toroidal vortices. Instead,small high-frequency vortices are generated. They foster
intense small-scale mixing leading to a flame elongation
and a more uniform temperature distribution. Its maximum level is decreased by approximately 200 K, which
may have a significant impact on the thermal reduction of
NOx.
Contact: artur.tyliszczak@pcz.pl

Large-eddy Simulation of flashback oflean-premixed low-swirl hydrogen jet
flame
Maho Kawai, Jun Nagao, Abhishek Lakshman Pillai,
Ryoichi Kurose
Kyoto university, Japan

Lean-premixed hydrogen combustion is currently attracting attention as an eco-friendly strategy for use inaircraft gas turbine engines. This method has the advantage of emitting no CO2 and significantly reducing NOx
emissions by lowering the flame temperature. Despite thisadvantage, flame flashback into the injector is one of theunderlying problems of premixed hydrogen combustion.
As flashback damages the combustor system and harms
the safe operation of the gas turbine engine, investigationof the flashback mechanism is crucial. This study analyzes
the flashback of a lean-premixed swirling hydrogen flamein a low-swirl combustor (LSC) using Large-eddy Simulation employing the dynamic Smagorinsky Model as a subgrid turbulence model. The dynamically thickened flame
model is also applied as a turbulent combustion model
to resolve the flame thickness on the LES computational
grid. The presented results show that flashback is initiatedfrom the center of the injector after the lifted flame attaches itself to the periphery of the injector exit. This typeof flashback is specific to the flow field in LSC, where themean velocity away from the LSC axis is larger than thatat the LSC axis. Flame dynamics and flame propagation
characteristics during flashback are also investigated.
Contact: kawai.maho.35c@st.kyoto-u.ac.jp127Track05 Combustion dynamics and instabilities

A study of dynamic thickened flame
modeling effects on intrinsic instabilities
of premixed hydrogen flames incomparison with direct numericalsimulations

Aleksi Aukusti Rintanen, Ilya Morev, Parsa Tamadonfar,
Shervin Karimkashi, Ville Vuorinen
Aalto University, Finland

Laminar premixed lean hydrogen flames are thermo-diffusively unstable, which leads to significant flame
front wrinkling and faster flame propagation compared tothat of the laminar unstrecthed burning velocity. On theother hand, hydrogen flames have very thin interfaces,
making their modeling challenging. The thickened flame
model targets at manipulation of the governing equations
so that the flame front is artificially thickened without
affecting other characteristics of the flame. This study
explores the effects of artificial flame thickening on intrinsic flame instabilities numerically. The open-source CFD
toolbox OpenFOAM is used together with a dynamic loadbalancing library (DLBFoam), where the dynamic variantof the thickened flame model is implemented. The results
show that similar intrinsic instabilities, observed using
direct numerical simulations (DNS), are obtained when
the thickened flame model is used. However, the lengthand time scales of these instabilities are stretched by the
thickening factor. This leads to slower developments ofthe flame fingers and thus, slower consumption speeds
during the flame front development, compared to the
DNS results, while the final consumption speeds remain
approximately the same.
Contact: aleksi.rintanen@aalto.fi

High-fidelity Large-Eddy Simulations ofignition of lean H2/air flames: Unveilingthe role of hydrogen diffusivity andextinction strain rate on the flame
dynamics

Tarik Yahou1, Nicola Detomaso2, Davide Laera3, Laurent
Selle4, Thierry Poinsot4, Thierry Schuller4, James R
Dawson5
Norwegian University of Science and Technology, Norway, 2CERFACS,
France, 3Polytechnic University of Bari, Italy, 4Institut de M ́ecaniquedes Fluides de Toulouse, France, 5Norwegian University of Science andTechnology, NTNU, Norway
1

High-Fidelity LES are used to unveil the influence ofhydrogen diffusivity on the flame dynamics during ignitionof lean H2/Air flame. The simulations cover a CH4/air mixture with a unity Lewis number and a lean H2/air mixture
with a sub-unity Lewis number. Both mixtures are injected128

at a fixed bulk flow velocity of Ub = 5 m/s, with the equivalence ratio adjusted to match the laminar unstretched
flame speed of S_l= 0.25 m/s. The numerical setup is firstvalidated against isothermal and reactive PIV measurements, as well as OH-PLIF images, showing a very good
agreement. Analysis of the absolute flame speed S_a revealed that despite its lower thermal expansion ratio (ρ_u/ρ_b), the H2/air flame a higher absolute flame comparedto the CH4/air mixture. It was further demonstrated thisdynamic is promoted by the interplay between thermal
expansion and stretch effects evaluated via the stretch
factor I_0. While CH4/air flame has a higher thermal expansion ratio, the H2/air flame displayed higher I_0 values
due to the effects of preferential diffusion. Expanding theexamination into a local analysis of the flame front dynamics during flame expansions that the extent of flame
propagation into the high shear flow regions is governedby the local flame stretch. Excessive stretch values often
result in flame quenching, particularly evident in CH4/air
flames where the critical threshold value is notably lower.
In contrast the high resistance to stretch of H2/air flames
allows the combustion reaction to persist in those region,
facilitating widespread flame expansion throughout theentire domain.
Contact: james.dawson@ntnu.no

Numerical Study on Controlling Factors
Affecting Flow Dynamics of Combustion
Gases in Municipal Solid Waste
Incinerators
Kazuyuki Takase, Kazuaki Kusakabe

Fukushima Prefectural centre for Environmental Creation, JapanAt several municipal solid waste incineration facilities inFukushima Prefecture, the incinerators are operated manually, so waste combustion can be affected by differencesin operating techniques among the incinerator operators.
In particular, the plastic waste, which has been increasing
in recent years, burns with a high calorific value, and there
is concern that a sudden increase in combustion gas temperature may damage the inner walls of the incinerator.
Therefore, as part of a study to minimize the influence of
operating techniques on the incinerator operation andto enable stable operation under transient combustion
conditions, evaluation of combustion behavior in the incinerator through a numerical simulation was considered.
In this study, sensitivity analyses were conducted underconditions that simplified the specifications of the municipal solid waste incinerator in operation in Fukushima
Prefecture, using as parameters the controlling factorsthat affect the combustion gas flow dynamics in the incinerator. The controlling factors were the amount of fuel19th International Conference on Numerical CombustionTrack05 Combustion dynamics and instabilities

waste supplied to the incinerator and the air flow rate
injected into the incinerator to promote combustion. As aresult, the combustion gas flow distribution and combustion gas temperature distribution in the incinerator werequalitatively predicted. The results of the present study
quantitatively clarified operating conditions that can maintain the combustion gas temperature in the municipal
solid incinerator below the upper limit (900-950°C) evenfor transient combustion conditions.
Contact: takase_kazuyuki_01@pref.fukushima.lg.jp

129

Track06 Emissions and pollution

Track06-1 Emissions andpollution (1)Chair: Stelios Rigopoulos
Wednesday, May 8; 15:30 - 17:10; Room L

Manifold modeling for reactive nitrogen
emissions in ammonia-hydrogen-nitrogenturbulent nonpremixed flames
Hernando Maldonado Colmán, Michael E. Mueller
Princeton University, United States

The use of ammonia as an alternative fuel is challenging due to the need to minimize reactive nitrogen (nitrogenoxides and nitrous oxide) emissions. In gas turbine-like
configurations, recirculating flows increase residence
times allowing for the reduction in unrelaxed emissions,which have been recently pointed out as the major contributor of reactive nitrogen emissions. To gain further insight on the impact of residence time on reactive nitrogen
emissions, a laboratory-scale ammonia-hydrogen-nitrogenturbulent nonpremixed bluff body flame is investigatedusing Large Eddy Simulation (LES) employing a manifold
model for nonpremixed combustion. Results are validated
against experimental measurements. Extensive analysis
is carried out to understand the influence of the manifold
model assumptions in predicting reactive nitrogen results.
Unlike in hydrocarbon combustion where the formationof reactive nitrogen emissions is almost always slow andin small concentrations, reactive nitrogen emissions inammonia combustion form and relax over a range ofchemical time scales and can be present in large concentrations. Therefore, a new manifold model formulation
is proposed, termed a partially non-equilibrium manifold
formulation, in which chemical species governed by slow
chemical time scales are solved using a non-equilibrium
manifold formulation, which, to ensure mass consistency,
constrain the chemical species governed by fast timescales and an equilibrium manifold formulation.
Contact: hm2524@princeton.edu

130

Numerical investigation and modelingof NOx emissions during ignition andcombustion of pulverized biomass fuels
Pooria Farmand1, Christian Boehme1, Hendrik Nicolai2,
Francesca Loffredo1, Paulo Eduardo Amaral Debiagi3,
Michael Gauding1, Christian Hasse2, Heinz Pitsch1

RWTH Aachen University, Germany, 2TU Darmstadt, Germany, 3Universityof Nottingham, Canada
1

In order to develop reduced-order models for the correct prediction of NOx emissions in pulverized biomass
flames, NOx formation pathways in biomass combustionin air and oxy-atmospheres are investigated by direct
numerical simulations. Solid biomass fuels contain fuel-bound nitrogen, which contributes to NOx formationand complicates the NOx prediction. The NOx formation
pathways and modeling of NOx emissions in biomass
combustion are not fully understood, necessitating further
investigation through detailed kinetic models. Therefore,
reactive biomass simulations in a hot co-flow configuration in laminar conditions considering the detailed
NOx surrogates are performed. To this end, the detailed
CRECK-S kinetic scheme for the solid-phase and a newly
developed detailed gas-phase kinetic model, including
the NOx formation pathways for biomass combustion, areemployed. NOx formation is very sensitive to several parameters in solid pulverized fuel flames, such as solid fueltype and composition, particle size, particle injection rate,
and ambient conditions. The current study assesses theeffects of these different parameters on the formation ofNOx pollutants. In particular, a detailed pathway analysis
is performed to identify the contributions of fuel-related
NOx and thermal NOx emissions. Finally, based on theanalysis of the NOx formation pathways and the identification of the dominant pathways at different conditions,guidelines for reduced-order modeling approaches forthe correct prediction of NOx pollutants are discussed. To
this end, detailed simulation results are utilized to identify
the suitable parameters to describe the particle-chemistry-pollutant interactions in the context of tabulated
Flamelet models through an optimal estimator analysis.
Contact: p.farmand@itv.rwth-aachen.de

19th International Conference on Numerical CombustionTrack06 Emissions and pollution

Numerical simulation of hydrogen-airsteam flames with NOx production

Quentin Cerutti, Guillaume Ribert, Pascale Domingo
COMPLEXE DE RECHERCHE INTERPROFESSIONNEL ENAÉROTHERMOCHIMIE, France

The use of hydrogen (H2) as an alternative fuel to hydrocarbons constitutes a major challenge to reach carbon
neutrality. However, operating an engine with hydrogenis a difficult task since hydrogen, a molecule with a low
molecular weight, is highly flammable in the air with afast chemical kinetic and high combustion temperature.
This leads to scientific and technological issues such as
pre-ignition and engine knocking, flashback, flame stabilization, transition to detonation as well as polluting
emission of nitrogen oxides (NOx). To overcome the difficulties associated with H2/air combustion, steam dilution
combustion appears as a promising approach to decrease
the flame speed, the adiabatic flame temperature, andthe NOx emission. Understanding and predicting hydrogen-air-steam flame structures are therefore major issues
in the context of high-fidelity simulation which are presently studied through jet flame configurations to highlightthe importance of detailed chemical schemes, preferential
diffusion, exhaust gas recirculation, and flame wrinkling inNOx production. The role of species NNH has been scrutinized since it is a pivotal species for NO creation.
Contact: quentin.cerutti@insa-rouen.fr

A direct numerical simulation study of
wet combustion effects on NOx/N2O
formation pathways in laminar andturbulent premixed ammonia/hydrogen/
air flames
Shervin Karimkashi1, Parsa Tamadonfar1, Alessandro
Stagni2, Ossi Kaario1, Ville Vuorinen1
1

Aalto University, Finland, 2Politecnico di Milano, Italy

While ammonia/hydrogen combustion offers a great
potential to facilitate a smooth transition to clean combustion, NOx/N2O mitigation in such flames is of great
importance. In this work, direct numerical simulationsof planar premixed ammonia/hydrogen/air flames are
conducted under laminar and turbulent conditions in
OpenFOAM using detailed chemistry. First, under laminarconditions, a study utilizing parametric sweeps of theequivalence ratio (φ), steam-to-air ratio (Ω), and ammonia/
hydrogen blending-ratio (α) pinpoints conditions associated with reduced NOx/N2O emissions while ensuring thatflame properties remain pertinent to those observed inhydrocarbon flames. Second, effects of isotropic homo-geneous turbulence in the thin reaction zones regime forthree cases are studied and NO formation pathways arethoroughly investigated. Under both laminar and turbulent conditions, wet combustion (Ω~0.3-0.5) leads to NO
emissions drop by a factor of 2-3 compared to the drycases at similar (φ, α). The main reason for NO mitigation
by adding steam is found to be (i) lower combustion temperature, and (ii) switches in the NO formation pathways,
mainly attributing to the reduced contribution of HNO
pathway in producing NO and the amplified share of N2
and N2O pathways in consuming NO. Moreover, the roleof individual reactions in pathways switches is analyzed.
Contact: shervin.karimkashiarani@aalto.fi

Development and performance analysis
of a novel, energy-efficient PNG porous
burner for cooking applications
Udaybhanu Gadi, Reddy Mahendra Vanteru
Indian Institute of Technology Kharagpur, India

Cooking requires a substantial amount of energy. In
growing countries like India, the primary energy source forcooking applications is liquid petroleum gas (LPG). There
are notable challenges associated with LPG, including therisk of leakage, which can lead to major accidents due toits highly flammable nature, and the need for cylinder refilling when it is drained. In the current investigation, piped
natural gas (PNG) is considered a promising alternativewith continuous fuel supply for cooking applications. It is
recognized as a cleaner-burning fuel that produces lesser
greenhouse gas emissions (CO2, NOx) and particulatematter (soot) during combustion, contributing to a lower environmental impact. Based on the literature, in thepresent study, the porous domain is considered for flamestabilization under fuel lean operating conditions and to
facilitate internal heat recirculation, thereby preventing
local quenching. The numerical study is conducted toanalyze the performance and emission characteristics ofa novel energy-efficient porous burner (NPB) operated
on PNG (95% CH4 and 5% C2H6) for different thermal
inputs (1-3 KW) using the reduced USC Mech_50 species
chemical kinetic mechanism and compared with the conventional LPG burner (CB). The developed novel burnerdemonstrated stable combustion inside the porous domain over entire operating conditions. In comparison to a
CB, a notable increase in thermal efficiency, reaching up
to 3%, along with significant reductions in CO, CxHy, andNOx emissions of an NPB is observed.
Contact: bhanuday1995@gmail.com

131Track06 Emissions and pollution

Track06-2 Emissions andpollution (2)Chair: Nozomu Hashimoto
Friday, May 10; 15:20 - 17:40; Room G

Effect of oxygenates on soot formation
during the combustion of fuel-rich CH4
mixtures
Mustapha Fikri

Institute for Energy and Materials Processes - Reactive Fluids, Universityof Duisburg-Essen, Germany

Polygeneration in internal combustion engines enables
a variable generation of mechanical power and valuable
chemicals based on reactions under fuel-rich conditions
depending on the fuel/air equivalence ratio phi= and thereaction conditions. This may help to mitigate one of
the main challenges of future energy systems – accommodating fluctuations in energy supply and demand. Investments in devices for grid stabilization could be more
economical if they have a second use. For conversion ofultra-rich fuel/air mixtures into potentially useful chemicals in a polygeneration context, oxygenated compounds
are of interest to increase fuel conversion while suppressing soot formation. Thus, the influence of various oxygenates (diethyl ether (DEE), methanol, or dimethoxymethane(DMM)) on soot formation was addressed by studying
the oxidation (phi=5 of gas mixtures using CH4 as basefuel and additives (10 mol% relative to the base fuel) in a
shock tube at 1480–1900 K at around 5 bar. Laser extinction at 633 nm was used to measure soot optical densities
and absorption spectroscopy with mid-IR quantum cascade lasers yielded temperature and CO concentration as
a function of reaction time. Experimental data is comparedto simulations.
Contact: mustapha.fikri@uni-due.de

Effects of Hydrogen and Ammonia
Substitution on Soot Formation in
Turbulent Ethylene/Nitrogen Jet Flames
Tongtong Yan1, Zhiwei Zhao1, Dezhi Zhou2

Shanghai Jiao Tong University, China, 2UM-SJTU Joint Institute, Shanghai
Jiao Tong University, China

1

This study investigates the effects of hydrogen andammonia addition on soot formation in turbulent non-premixed ethylene/nitrogen jet flames. Large Eddy Simulations with the Flamelet/Progress Variable (FPV) model,
considering comprehensive soot-turbulence-chemistry,132are conducted. A detailed chemical mechanism including
heavy PAH like coronene is used to explore the influenceof varying hydrogen and ammonia concentrations on
PAHs. The effects of hydrogen or ammonia doping on
temperature, different species (such as HCN and benzyl
radical), and their impact on soot formation source terms,
including nucleation, surface growth, condensation, andoxidation are explored, revealing the complex interactions that ultimately influence soot formation. It is foundthat consistent with the experimental results, introducing
hydrogen increases soot volume fraction, whereas ammonia doping has the opposite effect. Notably, ammonia
addition significantly suppresses the formation of heavy
Polycyclic Aromatic Hydrocarbons (PAHs). The addition ofammonia substantially impacts the surface growth process, impeding the further growth of soot particles.
Contact: yan_tt@sjtu.edu.cn

Modal analysis of flow dynamics and sootevolution in an aero-engine model
Jinbo Cheng, Yihao Tang, Wang Han, Lijun Yang
BeiHang University, China

Soot formation and evolution are very sensitive to flow
dynamics encountered, especially in confined turbulent
swirling flows where strong shear layers and recirculation
regions will introduce fast time-scale and slow time-scalecomplex coherent patterns. These patterns are frequently
essential to unlock our understanding of soot evolution
and to control soot formation and emission. To this end,large-eddy simulations (LES) of an aero-engine model
combustor with and without dilution jets are conductedwith state-of-the-art soot models. Then, modal analysis offlow and soot dynamics in the combustor is performed using the spectral proper orthogonal decomposition (SPOD)
method with transient LES data. The frequency bands ofboth high-frequency dynamics (HFD, 234.375-468.75 Hz)
and low-frequency dynamics (LFD, 0-156.25 Hz) are identified. It is found that compared to LFD, the HFD has amajor impact on velocity and PAH, while LFD plays a critical role in soot evolution. This is because the impact of
HFD exhibits an energy transfer process, i.e. velocity HFD
affects PAH, and then PAH would transfer modal energy
to soot. However, the evolution of velocity, PAH, and sootare found to be closely coupled with each other within
the LFD frequency band. Furthermore, it is found that forsoot and PAH, the impact of dilution jets on HFD modes isminor and on LFD modes is significant, while the opposite
impact is observed on velocity modes.
Contact: chengjinbo@buaa.edu.cn

19th International Conference on Numerical CombustionTrack06 Emissions and pollution

Numerical Computation of Sooting
Flames with a New Soot Fusing Model

Daniel O'Sullivan1, Russel Bertrum, Jr. Diemer2, Stelios
Rigopoulos1

Imperial College London, United Kingdom, 2University of Delaware, UnitedStates1

The prediction of sooting flames is a formidable challenge due to the need to account for several complex
kinetic processes and their interaction with fluid dynamics.
In this work, we focus on the fusing of soot aggregates,
for which a new model is presented and investigated via
the numerical simulation of a series of laminar co-flow
diffusion (Santoro) flames. To predict the morphology ofaggregates, a coupled two-population balance model thatsolves for the distributions of aggregates and primary particles is employed and integrated within a computational
fluid dynamics (CFD) code. This allows for the inclusion ofa finite-rate timescale for fusing, a process that increases the primary particle size. A new model for the fusing
timescale, derived from carbon black reactor data, ispresented and employed in the context of the two-population balance approach. Simulation results are comparedagainst experimental measurements for three Santoro
flames, namely a non-smoking, an incipient smoking anda smoking flame, as well as against simulations employing
fusing timescales obtained from expressions based on silica and titania models. It is found that the fusing rate hassignificant influence when predicting the quantity of sootescaping the flame as smoke.
Contact: s.rigopoulos@imperial.ac.uk

An LES-PDF-DPBE method for the flow
dynamics and soot formationin in anaero-engine model combustor: an insight
into the soot micromixing requency
Anxiong Liu, Kun Luo
Zhejiang University, China

This work presents the LES-transport pdf-discretised
PBE approach to model fluid dynamics and the evolutionof soot particles in a pressurised swirling-flow aero-engine combustor. This approach considers the interaction
between turbulent reacting flow and soot particles. A
reduced chemical kinetics mechanism including a seriesof PAHs species linked to soot formation is generated
employing the DRGEP approach, and is tested on a perfectly stirred reactor under varying equivalent ratio conditions. The soot kinetics model includes the PAH-based
nucleation and surface condensation, the HACA surface
growth and oxidation mechanism, and the size-dependent

aggregation. The soot morphology considers geometricalproperties for both spherical primary particles and fractal
aggregates. The simulation results show generally good
agreement with experimental measurements in terms ofswirling vortex, flame shape, temperature, OH species, andsoot volume fraction. By increasing the equivalence ratioat the primary injector, the influence of the low frequency
dynamics on soot formation is decreased.
A single micromixing frequency is usually taken forboth particulate soot and gaseous species, which is not
physically correct due to the much smaller molecular
diffusion of soot than gaseous molecules. To investigate
the effect of the soot micromixing, a quantitative analysis
is conducted by reducing the micromixing frequency factor from 1.0 to 0.1. The maximum soot volume fraction isobserved to increase a bit. However, compared with thesoot modelling using different soot kinetics and numericalmethods (like other LES and RANS simulation references),the difference of the soot predictions by varying the sootmicromxing frequency is negligible.
Contact: axliu22@zju.edu.cn

NUMERICAL INVESTIGATION ON THE
FUEL FLEXIBILITY OF A TYPICAL AEROENGINE SWIRL-STABILIZED FLAME

Pierre Vauquelin, Bora Cakir, Christer Fureby, XueSong Bai, Mattias Richter, Arman Ahamed Subash, David
Sanned, Megha Prakash
Lund University, Sweden

In science and industry, swirling flows are found in awide range of applications. In combustion, it is commonlyused to stabilize a flame. It maintains its ignition by recirculating the burnt gases with the incoming fresh air andfuel. Depending on the swirl intensity, residence times
may vary in the hot areas and thus, it tends to limit NOX
formation. In the context of reducing emissions of aviation
gas turbine engines, various sustainable aviation fuels
are being developed with the aim of keeping the existing
infrastructure unchanged. Thus, considering the variety
of fuel alternatives for aeroengines being increased, there
exists a clear demand for characterization of the fuelbehavior and flame interactions with the highly turbulent
flows found inside such combustion chambers.
The Triple Annular Research Swirler (TARS) burner,that mimics aeroengines combustors, has been previously
employed for experimentally studying non-reactive andreactive flows dynamics in open and confined combustion
chamber conditions. Here, combustion Large Eddy Simulations are used to investigate the combustion dynamics of kerosene-based liquid jet fuels such as Jet A but
also test fuels such as C1 and C5. The simulation results133Track06 Emissions and pollution

are analyzed in comparison with the experimental dataacquired during the measurement campaigns, which includes OH* chemiluminescence, OH* planar laser induced
fluorescence (PLIF) and particle image velocimetry (PIV).
Contact: pierre.vauquelin@energy.lth.se

Novel multiscale modeling methodology
for chemical kinetic modeling of fueloxidation using atomistic calculations:Application towards hydrogen
combustion
Bhuvan Raj Maddipati, Aditya Konduri, Phani Sudheer
Motamarri
Indian Institute of Science, Bengaluru, India

Chemical kinetic (CK) models are indispensable forhigh-fidelity continuum-scale combustion simulations,providing detailed insights into flow-chemistry interactions. Contemporary approaches to CK modeling combine
experimental data with theoretical calculations, such astransition theory, to construct a reaction mechanism thatis further validated based on experimentally obtained
flame speeds and ignition delay times. Despite extensive
experimental validation, these highly parameterized CKmodels are only valid for a specific range of temperaturesand pressures and eventually fail at extreme conditions(e.g., thermodynamic non-equilibrium). In contrast, reactive molecular dynamics (RMD) offers a promising solutionthat can incorporate the intricacies of extreme conditions
and provide a necessary CK model. By facilitating ReaxFF-based molecular dynamics, RMD offers a distinctive
advantage, enabling the direct exploration of pathways,
identification of intermediates, and calculation of reaction
rates, surmounting the limitations associated with conventional techniques. Recent studies have explored CKmodeling using the canonical ensemble, which, however,falls short in providing sufficient information and computationally expensive. In this study, the reaction mechanism
and rate constants of the hydrogen-oxygen system arecomputed using microcanonical ensembled RMD trajectories. Arrhenius parameters are fitted for each elementary
reaction by computing the kinetic rates at various temperatures, and a comprehensive CK model is developed forhydrogen oxidation. The accuracy of the MD-derived parameterization is assessed by examining the flame speed
in one-dimensional premixed continuum-scale simulations
and comparing the results to standard values. A consistent agreement in flame speed is observed across various
equivalence ratios, underscoring the robustness of theinformation derived from RMD simulations.
Contact: rajmaddipati@iisc.ac.in134

19th International Conference on Numerical CombustionTrack07 Droplets and sprays

Track07-1 Droplets and sprays (1)Chair: T.-W. Lee
Wednesday, May 8; 10:40 - 12:20; Room C

Numerical study on preferential
evaporation characteristics of ATJ-SPK/
Jet A spray flames in laminar counter-flow
Yanqi Zhang, Zhenhua An, Jiangkuan Xing, Ryoichi
KuroseKyoto University, Japan

Abstract: Sustainable aviation fuels (SAFs) play an important role in the goal of achieving carbon neutrality inthe aviation industry by 2050. Currently, SAFs are allowed
to be used by blending with conventional aviation fuels up
to certain percentages. Understanding the spray flamesof the fuel blends is crucial for their clean and efficientutilization in aircraft engines. In this study, direct numerical simulations of laminar counter-flow spray flames are
performed. The fuel is the 50%-50% blend of ATJ-SPK
and Jet A. The Hychem mechanism is used to account for
the gas phase combustion. The preferential evaporation
behavior is investigated under three droplet sizes (20, 40,
and 70μm) and three strain rates (50, 100, and 200 1/s).
The numerical results indicate that the droplet size andstrain rate determine the droplet penetration into flame
fronts, which ultimately influences the intensity of thepreferential evaporation. Overall, at high Stokes numbers.
strong effects of preferential evaporation can be observedin reaction zones, which can influence the local fuel composition and the subsequent combustion behavior ofspray flames.

Artificial Neural Network Aided VaporLiquid Equilibrium Model for MultiComponent High-Pressure Transcritical
Flows with Phase Change
Navneeth Srinivasan, Hongyuan Zhang, Suo Yang
University of Minnesota, Twin Cities, United States

To enhance efficiency in modern combustors, elevating system operating pressure is common, often leading
to supercritical and transcritical fluid regimes. The firstprincipled Vapor-Liquid Equilibrium (VLE) model for transcritical thermodynamic modeling is computationallyintensive and has encounters robustness challenges. This
study introduces a novel Artificial Neural Network (ANN)-aided VLE model for fully compressible CFD solvers.
The ANN, trained in Python with TensorFlow and optimized for inference using ONNX Run-time, can integrate
seamlessly with any C++-based compressible CFD solver.
This plug-and-play model enables simulations of transcritical processes in high-pressure liquid-fueled propulsion
systems using only open-source packages, eliminating
the need for proprietary VLE model development. The
model’s performance is evaluated in shock-droplet interaction and temporal mixing layer simulations, surpassing
performances of direct evaluation and the in-situ adaptive
tabulation (ISAT) method. Notably, it demonstrates implicit load balancing and robust strong parallel scalability. The
plug-and-play methodology is versatile, as demonstrated
by coupling it with an open-source real-fluid CFD solver tostudy high-pressure droplet evaporation at liquid-fueled
detonation conditions. This approach addresses computational challenges in transcritical thermodynamics while
offering a flexible solution applicable to various compressible and conservative CFD solvers.

Contact: zhang.yanqi.56j@st.kyoto-u.ac.jp

Contact: srini237@umn.edu

Multi-component evaporation for spraycombustion
Giuseppe Indelicato, Ambrus Both, Daniel Mira
Barcelona Supercomputing Center, Spain

Liquid spray combustion plays an important role inmany practical devices, such as aircraft engines, liquidrocket and internal combustion motors. The understand-

135

Track07 Droplets and sprays

ing of such flames is of key importance for design andoptimization of such devices, especially given the complex
and multi-disciplinary phenomena involved. To mentiona few, the occurrence of preferential evaporation effects
due to different volatiles of multi-component realistic
fuels and the simultaneous existence of multiple combustion regimes. In order to singularly analyze these effects,
canonical configurations of spray flames are commonly
employed. In particular, counterflow spray flames havebeen widely employed using different strategies to inject
fuel droplets. Parametric analysis have then been performed based on droplet diameter, global equivalence
ratio or strain rate, in order to asses their effect on theensuing flame structure.
In this work we present a numerical framework coupling multi-component evaporation with a finite-ratechemistry solver. The mentioned framework is applied
to the simulation of a paradigmatic counterflow flame
configuration to investigate preferential evaporation andcombustion characteristics on realistic aviation fuels.
Contact: giuseppe.indelicato@bsc.es

Numerical simulation of heat transfer andevaporation of a sessile droplet on a hot
wall
Kenya Kitada, Tianyi Wei, Abhishek Lakshman Pillai,
Ryoichi Kurose
Kyoto University, Japan

A good understanding of the heat transfer mechanism
between impinging spray and the combustion chamber
wall in compression ignition engines is needed to reduce
the heat loss through the wall and improve their thermal
efficiencies. This study investigates the effect of the wall
wettability on the heat transfer and evaporation of a sessile droplet on a hot wall in a uniform flow by applying
three-dimensional numerical simulations accounting forevaporation from the gas-liquid interface. The wettability
is considered by applying a contact angle based on heightfunction methodology. The gas-liquid interface is captured using the volume of fluid method. The results showthat after a droplet passes over the wall, the wall is cooled
under all wettability conditions. Additionally, the droplet isheated by the heat transfer from the wall and cooled on
the windward side due to the latent heat of evaporation
which is active there. Furthermore, decreasing wettability
enhances the formation of the circulating flow inside thedroplet, which significantly affects the temperature distribution there and the wall heat transfer characteristics.
Contact: kitada.kenya.87c@st.kyoto-u.ac.jp136Mechanism of the trans-critical phasechange process for binary methanolheptane droplets

Zhanyuan Wang1, Lei Zhou1, Haiqiao Wei2, Gequn Shu3,
Lijia Zhong1
1

Tianjin University, China, 2Shenyang Aerospace University, China,
University of Science and Technology of China, China

3

The trans-critical transition process of fluids refers to
its thermodynamic trajectory from the sub-critical state
to the supercritical state. In current study, the trans-critical phase change of binary alkane-methanol droplets isinvestigated by the molecular dynamic methods in different ambient temperature and pressures, and in different
blending ratios of the blends. Using a new approach fromthe perspective of analyzing the atomic pair entropy fingerprints, we quantitatively distinguish different stages inthe trans-critical process of binary alkane-methanol droplets based on the degree of fuel molecular disorder within
the fluids near the droplet surface, and identify the transition of phase-change from the subcritical-like evaporation
mode to the supercritical-like diffusion-dominated mode.
It is discovered that the azeotropy and preferential evaporation phenomena are inhibited at high ambient pressures. The findings also indicate that with the increasing
proportion of methanol in the binary droplets, the phasechange mode tends to show more subcritical-like featureowing to the introduction of higher critical pressure andhydrogen bonding effect. Finally, the influence of ambient
temperatures and pressures on the mode transition oftrans-critical phase change is discussed systematically.
Contact: 759235360@qq.com

Track07-2 Droplets and sprays(2)
Chair: Jiangkuan Xing
Wednesday, May 8; 13:30 - 14:50; Room C

Turbulent spray combustion modellingbased on similarity mapping
Lipo Wang

Shanghai Jiao Tong University, China

For the purpose of design and application, reliablepredictions of turbulent spray combustion are of particular importance. However, there are modelling challenges
which are still not well resolved, e.g. coupling between
liquid vaporization and chemical reaction. Recently, asimilarity mapping approach has been developed andimplemented to case tests. With some reasonable sim-

19th International Conference on Numerical CombustionTrack07 Droplets and sprays

plification, the two phase governing equations can bereformulated as equations in the single gas phase withreconstructed spray-related source terms. Solutions ina laminar counterflow configuration assume interesting
similarity features, such as the (almost) independence ofthe evaporation path after mapping onto a newly definedquantity R, constructed from sensible enthalpy and mixture fraction. In this regard, the flamelet tabulation dimensionality can be hopefully reduced, which then provides
a different scenario to understand the spray combustion
physics. Upon the conventional flamelet/progress variable
model, the flamelet library is constructed from a seriesof quasi one-dimensional spray counterflow solutions,
integrated with the multiple solution modes. Test cases,
including the laminar spray counterflow flame and Sydneyspray turbulent flame, indicate that this newly proposedmodel is in principle favorable to improve the numericalpredictability with acceptable computational cost.
Contact: Lipo.wang@sjtu.edu.cn

Large eddy simulation of a swirling spray
flame using the two-phase spray flamelet
model

Yicun Wang1, Changxiao Shao2, Tai Jin1, Jiangkuan Xing3,
Kun Luo1, Jianren Fan1

1
Zhejiang University, China, 2Harbin Institute of Technology, China, 3Kyoto
University, Japan

Turbulent spray combustion widely exists in a variety ofenergy power systems, and the strong turbulence-chemistry interactions (TCI) lead to the demand for accurate
combustion models. Our recently developed two-phasespray flamelet/ progress variable (TSFPV) model has
shown sound performance in spray combustion modelingbecause it can consider the effect of droplet evaporation on the flamelet structure. The previous validationof the TSFPV model focused on simple configurationsof non-swirling jet spray flames. In this work, the TSFPV
model is further applied to the complicated configurationof the Cambridge swirling spray flame. The M-shaped
flame is correctly reproduced by comparing the contour
plots with experimental images. Quantitative statistics ofthe liquid phase achieve a good agreement with the experimental measurements in terms of droplet diametersand velocities. The complex flame structure is further
analyzed, with an emphasis on the inner flame in the twophase spray combustion regime. Some droplets penetrate
the flame and the evaporation source term cannot beignored in the flame region, representing the significant
droplets/ flame interactions. Scatter plots of droplet axial velocity illustrate the droplet dynamics with different
sizes. The droplets with smaller diameters achieve a ve-locity balance with the surrounding gas, while the larger
droplets penetrate the inner recirculation zone (IRZ) andthe inner flame zone. In conclusion, the TSFPV model
is well-validated on the Cambridge swirl burner, and theflame analyses deepen the understanding of the twophase spray flame structure.
Contact: wangyicun@zju.edu.cn

Combustion of Suspended Droplets inNormal Gravity Conditions
Edoardo Cipriano, Alberto Cuoci
Politecnico di Milano, Italy

In the last few years, several models for the simulationof phase change using multiphase CFD have been proposed. Most of these models assume constant physicalproperties, which limits their applicability to benchmark
phase change simulations. In this work, we extend a VOFbased phase change model to simulate combustion of realistic droplets, suspended on a solid fiber in normal gravity conditions. This configuration has been widely studied
in experimental works, but no numerical models that areable to combine: i) interface-resolved evaporation; ii) suspension by the action of the surface tension force; iii) variable physical properties; iv) combustion chemistry, havebeen proposed. This work combines these features resulting in a generic model which describes the combustionof multidimensional droplets, including buoyancy effects,
thermal expansion, and complex kinetics. The results
obtained using this model are in good agreement with experimental data, and they reveal interesting flow featuresthat cannot be resolved using more widespread spherically symmetric models. The implementation is based on the
Basilisk code; the code and the simulation setup are freely
available on the Basilisk sandbox.
Contact: edoardo.cipriano@polimi.it

Analysis of Evaporation Rate in
Detonation Induced Break-Up of a
DropletRal John Bielawski, Venkat Raman
University of Michigan, United States

Detonation based propulsion has the potential toachieve improved performance as well as offering asmaller lighter combustors. There is particular interest in
using denotative propulsion for hypersonic applications
due to the rapid rate of combustion within a detonation
allowing for shorter combustors and lower inlet compression. Practical detonative propulsion systems will137

Track07 Droplets and sprays

utilize liquid fuels resulting in a detonation propagating
through a mist of liquid droplets. It is currently unknown
if the detonation can break-up and evaporate in time tosupport the detonation directly. To better understand thisprocess high fidelity simulations of a droplet being struck
by a detonation wave will be performed and the breakup and evaporation of the droplet will be investigated.
These studies will be conducted using an diffuse interface
approach with thermo-chemical relaxation to capture theevaporation and cavitation. The analysis will focus on thedroplet evaporation rate to better estimate the amount ofvapor released near the detonation compared to evaporation after the detonation passes. This will provide insight
into how liquid fueled detonation engines operate and thepercentage of mass consumed by the passing detonationand fuel vapor remaining behind the detonation.
Contact: rbielaw@umich.edu

Track07-3 Droplets and sprays(3)
Chair: Junji Shinjo
Wednesday, May 8; 15:30 - 16:50; Room C

A Computational Simulation Method forSpray Flows with a Generalized PrimaryAtomization Module
Jungeun Park, T.-W. Lee

Arizona State University, United States

In prior works, we have developed an analytical framework based on integral form of the conservation equations, which leads to an expression for the Sauter mean
diameter as a function of the injection and fluid parameters. This has been validated for a range of injection
geometries. Since this analysis works for control volumes
drawn from the injector exit to any points in the flow field,
it can be adapted in a computational fluid dynamic (CFD)
framework. CFD is quite effective in determining thecontinuous liquid velocity field and also discrete droplet
motion, but becomes very costly at the droplet formation scales due to high spatial and temporal resolutions
required. Thus, the primary atomization process can beboxed into the control volume analysis, and linked as thedrop size calculation algorithm, along with a strain-rate
Weber number. These aspects of the computational procedure will be discussed, along with application examples
in some injection geometries such as pressure-atomized
sprays, liquid jets in cross flow, and flat spray nozzle flows.
Contact: attwl@asu.edu

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Numerical comparison of single- andmulti-hole marine-sized injectors
Andrea Di Matteo

Eindhoven University of Technology, Netherlands

Present work provides a comparison of the reacting
performance of a single- and a multi-hole diesel injector ina marine-sized constant volume chamber using tabulated
combustion model and RANS framework in OpenFOAM.
Given the dimensions involved, both in terms of nozzle(~1mm) and chamber diameter (500mm), a tabulated combustion model such as the Flamelet Generated Manifold isa convenient choice to keep the computational time low
with reliable results. After validating the mesh in termsof liquid length and spray penetration, the reacting cases
are compared with experimental results in terms of Ignition Delay Time (IDT), Lift-Off Length (LOL) and Ignition
Location (IL), both in single- and multi-nozzle configuration. Moreover, the performance of a two-equation sootmodel is tested in the multi-nozzle configuration, whererecent experiments provided new insights in the emission
production. Then, given the amount of fuel injected withlarge and multiple nozzles, the effectiveness of the specific enthalpy as an additional control variable for the FGM
manifold in capturing the heat exchange, without phasechanging, between droplets and surrounding gas is assessed.
Contact: a.di.matteo@tue.nl

Numerical Modelling of Liquid Ammonia
Injection
Paolo Guida, William Lafayette Roberts

King Abdullah University of Science and Technology, Saudi Arabia

Ammonia is one of the major candidates as an energy
vector of the future because of several characteristics
that facilitate its operation, such as the absence of carbon
emissions associated with its combustion. Ammonia is
generally vaporized before utilization, but liquid injection
is an attractive alternative. Liquid ammonia experiences
flash boiling when depressurized upon entering the combustion chamber. Numerical modelling of liquid ammonia
atomization is a formidable task given the complexity ofphase change and atomization co-occurring. One of themain challenges consists of predicting and eventuallyquantifying the occurrence of nucleation.
The method proposed in this work consists of adopting
a phase-field approach to model phase change without
relying on sub-models. The model is based on an extension of the nonconvex bulk Helmholtz free energy
accounting for interfacial energy following the Van der

19th International Conference on Numerical CombustionTrack07 Droplets and sprays

Waals theory of liquid-vapour phase change. The physicaldescription ultimately requires the solution of the non-isothermal Navier-Stokes-Korteweg equations.
The system of PDEs was solved by adding a relaxation
term to the equation with the scope to make it hyperbolic.
The numerical model was validated against benchmark
cases before being applied to ammonia injection. Spontaneous nucleation was observed in the case tested.
Contact: paolo.guida@kaust.edu.sa139

Track09 Heterogeneous combustion

Track09-1 Heterogeneous
combustion (1)Chair: TBD
Wednesday, May 8; 10:40 - 12:40; Room L

A PBE-CFD approach for investigating
the asymmetric envelope flame around aburning aluminum particle
Jannis Finke, Fabian Sewerin

Otto von Guericke University Magdeburg, Germany

In support of our transition towards a sustainable
and carbon-free energy economy, metals are currently
investigated as potential recyclable energy carriers thatcan be exothermally burned in air. A major challenge forthe recovery of the metal oxide combustion products isthe formation of nano-sized oxide smoke fines. Following
metal evaporation and gas phase oxidation, oxide smoke
droplets nucleate from gaseous precursors and grow bycondensation and coagulation. In order to predict the size
distribution of the oxide smoke droplets and investigate
their propensity to deposit on a burning aluminum particle, we present a comprehensive and kinetically detailed
single particle combustion model in which the particle’s
reactive boundary layer is spatially and temporally resolved. The dynamics of the smoke’s size distribution aregoverned by a population balance equation (PBE) that issolved in conjunction with a reactive flow solver (CFD).
Although the model is tailored to the combustion of aluminum, it may readily be adapted also to other metals. A
particular novelty of our contribution lies with the incorporation of a time-varying fuel particle morphology, permitting an analysis of how morphological changes influence
the shape of the envelope flame and the migration ofsmoke towards the particle. Following a validation basedon experimentally measured burning times and residue
sizes, we instrument the model to assess the cumulative
pollutant charge emitted from a particle over the courseof its lifetime.
Contact: jannis.finke@ovgu.de140

On the limiting mechanism of single ironparticle combustion
Leon Thijs, XiaoCheng Mi, Jeroen van Oijen, Philip deGoey
Eindhoven University of Technology, Netherlands

Iron powder is considered as a promising metal fuelsince it is inherently carbon-free, recyclable, compact,cheap and widely available. To design and improve real-world iron-fuel burners, an in-depth understanding of
the fundamentals underlying the combustion of single
iron particles is required. Since iron burns in a heterogenous way, it was believed that no iron was lost throughevaporation during the combustion process. However,
our research has demonstrated that, despite the particle
temperature remaining below its boiling point, a small
but non-negligible mass loss occurs through evaporation.
Furthermore, for iron particle combustion, it has been
hypothesized that the oxidation rate of an iron droplet isthe result of an interplay among three mechanisms: (1)External diffusion of O_2 from the ambient gas to particle surface, (2) surface chemisorption of, and (3) internaltransport of Fe and O atoms. In this study, we explore
these limiting mechanisms through the utilization of various numerical methodologies, including boundary-layer
resolved models, zero-dimensional models, and molecular
dynamics simulations.
Contact: l.c.thijs@tue.nl

Modeling single aluminum particle
combustion in various oxidizers

Hongchao Chu1, Shibam Bose1, Mahsa Salehi Mobarakeh2,
Pooria Farmand1, Reza Kholghy2, Heinz Pitsch1
Institute for Combustion Technology, RWTH Aachen University, Germany,
Department of Mechanical and Aerospace Engineering, Carleton
University, Canada

1

2

Aluminum particles exhibit high energy density, making aluminum a promising carbon-free energy carrier for
future energy systems. Aluminum can react with various
oxidizers, including O2, CO2, and H2O. The combustion ofaluminum particles is intricate and challenging to model.
In particular, at elevated particle temperatures, solid aluminum may melt into liquid and evaporate, resulting in

19th International Conference on Numerical CombustionTrack09 Heterogeneous combustiona diffusion flame in the surrounding gas. On the particle
surface, both evaporation of liquid aluminum and heterogeneous reactions of liquid aluminum with oxidizer may
occur, which is not considered in existing models in theliterature. In simulations of practical applications involving a large number of particles, resolving the boundary
layer around individual particles becomes infeasible. Instead, point particle approximation without resolving theboundary layer is typically employed. This study proposesa single-particle combustion model for the point particle
approach, considering simultaneously the evaporationand heterogeneous surface reactions. Simulation results
are compared with experiments on single aluminum particle combustion in different oxidizers, covering conditions
where heterogeneous surface reactions and evaporation
are of various importance. Additionally, the proposedmodel is compared with existing models in the literaturethat involve different assumptions and simplifications.
Contact: h.chu@itv.rwth-aachen.de

Carrier-Phase DNS of Metal Particle
Combustion in a Turbulent Shear Layer

Mohammad Parsa Ghofrani Maab1, Tien Duc Luu2, Oliver
Stein3, Andreas Kempf1
Duisburg-Essen University, Germany, 2Karlsruhe Institute of Technology,
Germany, 3Karlsruhe Institute of Technology, Germany

1

A carrier-phase DNS (CP-DNS) of iron particle combustion in a turbulent mixing layer is presented. The
upper stream of the mixing layer features iron particles
suspended in cold air, while the lower stream provides
hot air moving in the opposite direction. All scales of thegas phase are resolved by DNS in the Eulerian framework,
while the solid particles are described in the Lagrangianframework. The combustion of iron particles is describedby an already existing sub-model implemented in thedispersed phase which interacts with the carrier phaseby means of momentum, mass and heat exchange. Additionally, the dispersed phase is considered to be dilute;
therefore, no direct particle-to-particle interaction is taken
into account. In this work, the previous simulations in thiscontext are cross-validated, extended by focusing on theeffect of particle size, and further analysis is presented.
This analysis explores the interactions between the gas
and particle phases, as well as the effects of turbulent
structures on the particle combustion behavior, including
ignition time and mode of heterogeneous combustion (kinetic/diffusion limit). Additionally, heat transfer is studied
in detail by investigating the effects of radiation and temperature distributions in both phases.
Contact: parsa.ghofrani@uni-due.deTrack09-2 Heterogeneous
combustion (2)Chair: Kazuki Tainaka
Wednesday, May 8; 13:30 - 15:10; Room L

NOx emissions of iron aerosol flames

Thijs Hazenberg, Catharina E.A.G. van Gool, Jeroen A. van
Oijen, Laurentius P.H. de Goey
Eindhoven University of Technology, Netherlands

In recent years, metal fuels have gained significant
attention as an alternative carbon-free energy carrier.
Iron is particularly interesting, as the boiling point of ironis above the stoichiometric adiabatic flame temperature,i.e., the products are mostly solid micron-sized particles.
While carbon-based emissions (CO, CO2, soot, etc) are
not a concern, iron nanoparticles and nitrogen oxides
are, because: The combustion occurs below the boilingpoint of iron, however, a small fraction can evaporate andas high temperatures are involved, nitrogen oxides (NO)are formed. In this presentation, freely propagating ironaerosol flames are utilized to study emissions. In lean iron
dust flames, the particle temperature can significantly
exceed the adiabatic flame temperature, which raises concerns about NO formation in the boundary layer. Usinga posteriori analysis, we show that these boundary layer
emissions can be neglected. In the bulk gas phase, thekey mechanism of nitrogen oxide emissions is identified.
As expected, avoiding high temperatures is useful for the
reduction of emissions.
Contact: t.hazenberg@tue.nl

Flame characteristics of iron dust
counter-flow flames

Catharina E.A.G. van Gool, Thijs Hazenberg, Jeroen A.
van Oijen, Laurentius P.H. de Goey
Eindhoven University of Technology, Netherlands

The need for alternative carbon-free energy sources
has led to extensive research on metal dust as a fuel. Iron
powder in particular has some promising characteristics:
the particles do not exceed the boiling temperature ofiron(-oxides) upon combustion and (volumetric) energy
densities are comparable to those of hydrocarbons. For
gaseous flames, it is well understood that flame characteristics can be modified by stretch effects. For ironflames, stretch effects are at least as important. Additional complexity due to the inertia of the particles asks fora new model to describe the particle flow strain. In this141

Track09 Heterogeneous combustion

study, iron dust counter-flow flames are utilized to investigate the impact of particle strain on the flame structure.
Two major effects are identified: preferential diffusion due
to the infinite Lewis number of iron powder, and an inertia
effect. The inertia of the particles leads to a particle flow
strain lower than the gas flow strain, causing an increasein powder concentration. The extent of this effect is particle size dependent.
Contact: c.e.a.g.v.gool@tue.nl

Flame structure and burning velocity ofhybrid methane-iron air flames

Aravind Ravi1, Thijs Hazenberg2, Mark Hulsbos2, Giel
Ramaekers2, Roy Hermanns2, Philip de Goey2, Jeroen van
Oijen2
1

Eindhoven University of technology, Netherlands, 2TUe, Netherlands

The burning velocity of micron-sized iron powder in air
is slow; therefore, iron flames are difficult to stabilize inan experimental setup and industrial burners. A support
fuel can be used to stabilize iron flames in experiments byenhancing the burning velocity. We performed numericalsimulations using methane as a support fuel, as the combustion characteristics of methane burning in air are wellknown. Numerical simulations are used to investigate theaddition of iron powder to methane-air flames, exploring
various particle sizes and concentrations while maintaining a constant equivalence ratio of the methane-air
mixture. The burning behavior of iron powder is found to
be influenced by factors such as particle size, equivalence
ratio and concentration. A critical concentration is identified, at which a sudden change in the flame structure isobserved. Below this critical concentration, iron particles
burned individually without forming a flame front, while
above this concentration, a flame front is observed withcomplete conversion of iron particles. The laminar burning
velocities obtained from the simulations are compared toexperimental results.
Contact: a.ravi@tue.nl

Reductive Activation of Commercial
Iron Ore Materials using H2 and NH3 forAmmonia Synthesis and Decomposition
Shihyuan Chen1, Li-Yu Wang2, Takahisa Mochizuki3,
Chia-min Yang4

National Institute of Advanced Industrial Science and Technology, Japan,
National Tsing Hua University, Taiwan, 3Energy Catalyst Technology
Group, Research Institute of Energy Frontier (RIEF), National Institute ofAdvanced Industrial Scien, Taiwan, 4Department of Chemistry, National
Tsing Hua University, Taiwan

1

2

The reduction behavior of commercial iron ore materials (Sigma-Aldrich), comprising crystalline Fe2O3
and Fe3O4 along with minor impurities like silicate andaluminate, was studied using temperature-programmed
methods with utilization of H2 and NH3 as potential green
energy carriers. It revealed that the reduction of iron ore
to metallic iron is more efficient in H2 than in NH3. The
latter potentially resulted in a mixture of iron (major) andiron nitride (minor). However, both H2- and NH3-reducediron samples exhibit activity in subsequent NH3 synthesis
and decomposition applications, representing typical reactions for the production and extraction of a hydrogen
carrier. More importantly, the reduced iron samples showa high ability to entirely decompose NH3 at temperatures
below 600 ºC and ambient pressure, approaching the performance of conventional Ru catalysts, albeit at a higher
cost. This research provides new insights into the production and utilization of green H2, with a particular focus on
green NH3, using economically viable, commercially available iron ore materials.
Contact: sy-chen@aist.go.jp

Track09-3 Heterogeneous
combustion (3)Chair: Oliver Stein
Thursday, May 9; 09:50 - 12:30; Room L

3D CFD particle-resolved simulationsof heterogeneous combustion of nonporous char in a fixed-bed reactor

Andrés Ignacio Arriagada Romero1, Mario Toledo
Torres2, Robert Hayes3, Petr Nikrityuk3

University of Alberta - Universidad Técnica Federico Santa María, Canada,
Universidad Técnica Federico Santa María, Chile, 3University of Alberta,
Canada12This work aims to numerically study a 3D chemicallyreacting fixed-bed for non-porous char under gasificationand flow regime conditions. Particle-resolved simulations

142

19th International Conference on Numerical CombustionTrack09 Heterogeneous combustion

were performed using the commercial software Ansys
Fluent, implementing a six semi-global kinetic scheme,
consisting of carbon monoxide combustion, forward andbackward water-gas-shift reaction, Boudouard reaction,and two other heterogeneous reactions. The fixed-bed
was composed of 85 spherical particles with a 5.6 mm
diameter, located in the bed zone and subsequently
placed in a stationary position. Several Reynolds numbers, inflow gas temperatures, and inlet mass fractions ofoxygen (YO2,in) were assessed. Experimental tests wereconducted to contrast numerical results. Mass fractionof species showed consistency when describing heterogeneous combustion, where the Boudouard reaction
and carbon monoxide oxidation were dominant among
heterogeneous and homogeneous reactions, respectively.
The inflow gas temperature was a critical parameter toassess since the kinetic scheme is notably activated from1300 K. Moreover, the highest temperature and carbon
dioxide concentration difference between particle surface
and gaseous phase were 0.39% and 29.70%, respectively.
A linear dependency for species concentration and temperature at low YO2,in was observed. This study may beconsidered as a benchmark case for validation of 1D and
2D models.
Contact: arriagad@ualberta.ca

Numerical study of the mechanisms of
convective burning of black powder
Pavel Utkin1, Petr Chuprov2

Harbin Institute of Technology, China, 2Institute for Computer Aided
Design of the Russian Academy of Sciences, Russian Federation

1

The work addresses the clarification of the mechanisms of convective burning of an extended black powdercharge. The hyperbolic Baer-Nunziato-type model is used.
Although the Baer-Nunziato equations have been used
for the simulations of combustion and detonation of heterogeneous explosives for a long time, there are only a
few works in which this model is used for gun powders.
The model takes into account the compaction effects ofthe gun powder as well as mass, momentum, and energy
interphase exchange between powder and gas. The numerical algorithm is based on the Harten-Lax-van Leer or
Godunov method with the pressure relaxation procedure.
Intergranular stresses in the phase of particles are taken
into account. The statement of the problem corresponds
to the full-scale experiment of B.S. Ermolaev with co-authors (Semenov Institute of Chemical Physics of RAS). The
correct wave pattern is obtained in the simulations, namely, the leading compaction wave, the combustion wavethat follows the previous one, and the waves reflectedfrom the side walls of the channel at the latter stages ofthe process. The explanation of the pressure curves at thetransducers along the channel is given. The comparisonof the simulation results with the experimental data andsimulations of B.S. Ermolaev is carried out.
Contact: utkin@hit.edu.cn

Heterogeneous Combustion of AP/HTPB/RDX Propellants with Detailed Kinetics
Pierre Bernigaud1, Dmitry Davidenko1, Laurent Catoire2
1

ONERA, France, 2ENSTA Paris, France

Composite solid propellants include as main constituents a binder, producing combustible gases by its pyrolysis, and particulate components, which generate oxidizing
gases. Ammonium perchlorate (AP) is a widely used ingredient for solid propellants, together with a polymeric binder such as the hydroxyl-terminated polybutadiene (HTPB).
These so-called AP/HTPB composite propellants havebeen extensively studied in the past. Next-generation propellants may include nitramine (RDX or HMX) particles asa partial replacement for AP for some specific purposes.
This study proposes a detailed kinetic model for the
combustion of the AP/HTPB/RDX ternary system. It isshown that the model reproduces the main combustion
characteristics of the studied ingredients. The reactions
mechanisms for the considered materials have been validated with respect to fundamental experiments.
Employing this combustion model, a flame above an
AP/HTPB/RDX composite propellant is simulated. The
considered 2D axisymmetric configuration represents
an RDX particle surrounded by a homogenized binder
composed of fine AP particles and HTPB. To the authors'knowledge, this is the first simulation of such a flame inthe literature. A study on the effect of pressure and RDX
particle diameter is conducted. It is shown that for each
RDX particle size, a pressure limit exists, below which
the RDX particle combustion becomes slow with a flame
typical for the so-called dark zone, . Reducing the RDX
particle diameter hence decreases the overall regression
rate. This behaviour is opposed to the one observed withconventional AP/HTPB propellants.
Contact: pierre.bernigaud@onera.fr

143

Track09 Heterogeneous combustion

Numerical approach to understandfactors affecting catalytic decompositionof methane

Vivek Kumar1, Sourabh Shrivastava1, Pravin Nakod1,
Krishna Kishore Chavan2, Shruti Pradeep Chavan2
1

Ansys INC, India, 2Cummins college of engineering for women, India

As the world looks for cleaner and more sustainableenergy, there's a growing need to find better ways to
produce hydrogen. Turquoise hydrogen, made by mixing
methane in a special way that captures carbon emissions,is a better way to make hydrogen without adding morecarbon to the atmosphere.
This research employs Computational Fluid Dynamics(CFD) simulations to scrutinize and enhance the turquoisehydrogen production process. The simulation model is intricately designed to capture the reactor system's fluid dynamics and chemical reactions during turquoise hydrogenproduction. The model's geometry incorporates a porous
cylindrical region and a fluidized bed reactor, with thedomain extending at the top and bottom to observe reactions and catalyst deactivation. The catalyst employed inthis study is Ni-Al2O3.
To optimize production efficiency, the model is simulated under various inlet conditions, specifically different
mass flow rates of methane (20, 50, and 100 ml/min) anddifferent concentrations of catalyst viz 65 wt.% Ni-Al2O3,
90 wt.% Ni-Al2O3 at varying wall temperatures (550, 650,
and 700 degrees Celsius). Additionally, the model undergoes simulations at different operating pressures, ranging
from 1 to 5 bar. The CFD simulations comprehensively
consider heat, mass, and momentum transport phenomena, coupled with detailed reaction kinetics. This approachprovides a thorough understanding of the intricate interactions within the system, contributing to optimizing turquoise hydrogen production.
Contact: vivek.kumar@ansys.com

Parametric study on optimal operation ofburning-off process for the removal of
deposited carbon in a coke oven
Keh-Chin Chang, Yi-Da Chung

National Cheng Kung University, Taiwan

Removal of deposited carbon in coke oven is a regulartask in the coking-making operation, either by traditional manual removal during maintenance downtime or byburning them off with air injected through the charging
holes before recharging coal into the coke oven. Numerical study for the burning-off carbon deposits with
air-injection process exists in literature but not many. The

144

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chemical reactions that are involved in the burning carbon deposits include heterogeneous and homogeneous
reactions over the heated wall surfaces in oven. It wasnoticed that the first near-wall grids in the computationalmesh should be placed within the viscous sublayer of thewall boundary layer for accurate calculation of the heterogeneous reaction rate. A typical coke-oven battery iscomposed of the oven chamber with an ascension pipeand four coal charging holes at the top of the chamber.
Carbon deposits generally accumulate on the upper sidewalls and the rooftop of the chamber and the goosenecksof the charging holes. A series of parametric study on theoperational conditions, including which charging hole withhow much air injection rate and how deep the air blowing
lance should be inserted into the chamber, will be conducted using a developed numerical model to search forthe optimal operation in question.
Contact: kcchang@ncku.edu.tw

A priori analysis on an extended flamelet/
progress variable model for coal/ammonia co-firing flame
Xue Qing Qing Qing Qing Qing Qing, Xing Jiang Kuan
Xing Jiang Kuan, Tang Xin Zhou Tang Xin Zhou, Luo Kun
Luo Kun, Fan Jian Ren Fan Jian Ren
Zhejiang University, China

Ammonia/coal co-firing is considered a promisingtechnology for reducing CO2 emissions, but the presenceof multiple fuel streams and nitrogen sources makes
accurate and efficient modeling of combustion and NO
formation challenging. In this study, a point-particle direct
numerical simulation (PP-DNS) work with detailed chemistry for coal/ammonia co-firing flame was carried out, andan extended flamelet/progress variable was developed toaccount for the multiple fuel streams and reacting stages. The extended model was then evaluated through apriori analyses with the PP-DNS solution as benchmarks
to assess its performance, demonstrating its capability toaccurately replicate the gas temperature, major species,
and CO profiles derived from DNS. The formation of NO
occurs with the same-order time scale as that of the major species in this flame, allowing for acceptable prediction by directly extracting data from the flamelet tables.
Interestingly, including NO in the progress variable did not
improve the prediction for NO and instead decreased theaccuracy of temperature and major species predictions.
The main deviations of NO prediction can be attributed toignoring the multi-dimensional effect.
Contact: 22127076@zju.edu.cn

19th International Conference on Numerical CombustionTrack09 Heterogeneous combustion

Numerical Analysis of MILD Combustionof Pulverized Biomass-Coal Flame
Ali Cemal Benim, Cansu Deniz Canal

Düsseldorf University of Applied Sciences, Germany

Combustion continues to play an important role in thearea of renewable energies. Besides the role of hydrogen,this is due to the role of biomass, which is increasingly
attracting the attention of researchers. For high thermal
powers, where solid fuels are burnt in pulverized form,
biomass is quite often fired in combination with the fossil
fuel, coal, i.e. in the co-firing mode, which is the subject ofthe present work.
MILD combustion is considered as a promising combustion mode due to its advantages of cleanliness andhigh efficiency. It has a wide range of fuel flexibility andcan remarkably diminish the NO emissions. In pulverizedbiomass-coal co-firing, the combustion is likely to be
driven by biomass, due to its comparably higher volatility
and ignition characteristics. The ignition time and mode of
biomass and pulverized coal are different like their burnout times, as the faster burning biomass can “rob” oxygenfrom coal. These interactions have not yet exhaustively
explored for MILD pulverized co-firing of biomass andcoal.
For throwing more light onto the above-mentioned
issues, experiments were performed by Fu et al. [1-3] in apilot-scale furnace, quite recently.
In the present work, the MILD pulverized biomass-coalflames measured by Fu et al. [1-3] are numerically analysed, to assess the prediction capability of different
computational approaches and mathematical models forthis type of combustion. In general, there is a rather highuncertainty in the pyrolysis rate of biomass. Applying different suggestions, the effect of this uncertainty on the
results is assessed. Beyond model validation, the complex
processes of MILD co-firing will be analysed.
[1] Hu, F. et al. Energy & Fuels 2019, 33, 12791-12800.
[2] Hu, F. et al.. Fuel Proc. Techn. 2022, 230, 107222.
[3] Hu, F. et al. Fuel 2023, 342, 127768.
Contact: alicemal@prof-benim.com

145

Track10 Detonation, explosions

Track10-1 Detonation, explosions(1)
Chair: Hiroshi Terashima
Wednesday, May 8; 13:30 - 15:10; Room B

Numerical Analysis of Exhaust Jet
Characteristics from Annular RDEs with
Various Outlet Geometries

Junichi Tahara1, Akiko Matsuo1, Eiji Shima1, Noboru
Itouyama2, Akira Kawasaki3, Ken Matsuoka2, Jiro Kasahara2
Keio university, Japan, 2Nagoya University, Japan, 3Shizuoka University,
Japan

1

Large Eddy Simulation of Rotating
Detonation Rocket Engines at Three
Operating Conditions

Matthew Harvazinski1, Mathias Ross1, Armani Batista2

United States Air Force Research Laboratory, United States, 2Jacobs Inc.,
United States1

In this study we examine three high-fidelity large
eddy simulation of rotating detonation rocket engines
to understand how to quantify the performance of thedevice from simulation data. The nature of the rotating
detonation engine makes geometric simplification difficult, as a result the full 360-degree geometry must be
included in the simulation. This large simulation domain
greatly increases the simulation cost. Simulations are runusing an in-house finite volume CFD solver with finite ratechemistry. A novel grid stitching system is used to buildup the complex geometry in the multi-block framework.
This framework allows different non-conformal meshes tobe joined together to construct the large geometry. Threedifferent operating conditions are simulated to examine
the effect of mass flow rate and overall equivalence ratio has on the devices behavior. The results show thatthe mass flow rate has a strong effect on the operatingpressure and strength of the detonation waves observed
inside the chamber. To elucidate the behavior, a numberof post-processing techniques have been developed tobetter understand the dynamics inside the engine. These
include the ability to separate how much of the combustion is tightly coupled with the detonation mode and how
much is instead deflagration. These tools will be used toquantify the performance of the device at the different
operating points.
Contact: matthew.harvazinski.1@us.af.mil

146The behavior of exhaust gases from the outlet of theannular rotating detonation engine (RDE) with which theoutlet geometry is changed and the interference withsupersonic airflow were investigated to examine the feasibility of operating a traditional rocket type RDE in a rocket-air breathing hybrid mode. The analysis was performedon an annular RDE with its outer wall curved into several
shapes, and on the area downstream of the combustor
outlet. The mainstream air was regarded as supersonic air
flowing into a combustor, and the propellant for the RDE
was premixed hydrogen-air gases under fuel-rich condition. As a result, the different behavior of the exhaust jet
was observed compared to that of the case using an RDE
with a normal outer wall shape. The mixing with supersonic airflow was also confirmed when it was considered toflowing outside the RDE, which indicating that altering theouter wall geometry of the combustor is one of the effective way for operating an orthodox rocket mode annular
RDE in the air breathing mode. At last, comparison of thethrust of the combustor in rocket mode and hybrid mode
operations was considered.
Contact: thrj0919nit@keio.jp

The mechanism of a resonant
amplification of pulsations behind adetonation wave propagating in a nonuniform mixture
Alexander Lopato1, Pavel Utkin2

Institute for Computer Aided Design of the Russian Academy of Sciences,
Russian Federation, 2Harbin Institute of Technology, China
1

Propagation of detonation waves in non-uniform gaseous mixtures has become a matter of interest over the
past several years due to the development of rotating
detonation engines. We developed an algorithm for thesimulation of detonation propagation in a non-uniform

19th International Conference on Numerical CombustionTrack10 Detonation, explosions

medium in a shock-attached frame of reference. One-dimensional reactive Euler equations with single-step Arrhenius kinetics were solved. Using the developed algorithm,
a numerical study of the propagation of a stable detonation in a medium with variable density was carried out. We
carried out a series of simulations, varying the wavelengthof the disturbances. As a result, several different modes of
pulsations of the detonation wave speed were obtained.
We got a nonlinear dependence of the amplitude of these
pulsations on the wavelength of disturbances with resonant amplification of pulsations for a certain range of
wavelengths. The effect is explained using the characteristic analysis in the x-t diagram.
Contact: utkin@hit.edu.cn

Simulation of Pulsating and Cellular
Detonation in Gases with Small Heat
ReleaseMark Short, Stephen Voelkel, Carlos Chiquete
Los Alamos National Laboratory, United States

We consider the nature of both pulsating and cellulardetonation in gases modeled with a one-step Arrhenius
chemical reaction for small heat release. With the onestep model, regimes of stable two-dimensional detonations can be found for small activation energies provided
the heat release remains moderate. As the activationenergy is increased, the magnitude of the heat release required for stable two-dimensional flow decreases rapidly.
For large activation energies only very small amounts ofheat release generate stable two-dimensional flow. Moreover, only small increments in heat release are needed todrive the flow first above the neutral stability boundary
for two-dimensional cellular instability, and then above
the stability boundary for one-dimensional pulsating flow.
We examine, numerically, the structure of pulsating andcellular Chapman-Jouguet detonation in gases with smallheat release using an inviscid, reactive Euler equations
framework. Due to the small amounts of heat release,such simulations required careful treatment of numericaldissipative effects. Additionally, we use a shock-fitted,
shock-attached frame that treats the detonation shock as
a leading boundary of the flow.
Contact: short1@lanl.gov



Numerical simulation of detonation
initiation over obstacles using the AMReX
library
Shun Matsuzono1, Edyta Dzieminska1, Youhi Morii2
1

Sophia University, Japan, 2Tohoku University, Japan

In this research detailed detonation analysis supports
complex geometries, and can be calculated using a supercomputer. In particular, the Adaptive Mesh Refinement(AMR) and Embedded Boundary (EB) methods provided
by the AMReX library are expected to make a significant
contribution to the generation of complex geometries
required in detonation analysis and to the reduction of
calculation costs. In addition, the MACKS method adopted
in the chemical reaction calculations can significantly reduce the computational cost and provide more accurate
calculations than the conventional methods. The aim of
this study is focused on the validation of the developed
CFD code and the confirmation of the effectiveness of the
AMR and EB methods for detonation analysis. The initial
validation was carried out for the shock tube problem and
now we compare numerical analysis with experimental
results. In detonation analysis, AMR can contribute to efficient and detailed detonation analysis due to the different
mesh resolutions required for the detonation, flame, unburnt, and obstacle areas.
Contact: edyta.d@sophia.ac.jp

Track10-2 Detonation,
explosions (2)Chair: TBD
Wednesday, May 8; 15:30 - 17:10; Room B

A detailed numerical investigation of thedetonation-bow shock interaction
Ashwath Sethu Venkataraman, Elaine Oran
Texas A&M University, United States

The interaction of a detonation with the bow shock
generated by objects moving at supersonic speeds has
applications in the fields of industrial safety and in thetransportation, storage of gaseous fuels such as hydrogenand natural gas. Numerical simulations and investigations
into accidents causing vapor cloud explosions (VCEs) haveshown that obstacles such as process equipment or otherdebris can accelerate flames and result in transition todetonation, causing huge economic and material losses.
Preliminary investigations of the interaction (ASV and ESO,
SciTech 2023) showed that detonation diffraction into the147Track10 Detonation, explosions

wake of the object weakens the cellular structure. Analysisof the vorticity budgets (ASV and ESO, 13th USNCM 2023)
showed that the baroclinic term and the flow divergenceterm were important in the diffraction. Here, we perform adetailed investigation of the interaction using two-dimensional reacting and non-reacting numerical simulations.
The speed, characteristic size of the obstacle are varied
and the interaction with a nonreacting shock, ZND detonation, and a cellular detonation are studied. The compressible flow phenomena such as shock-shock, shockflame interactions, detonation diffraction, shock-vortex,
and flame-vortex interactions are studied by looking at
the changes in the state variables and their contribution
to the vorticity budget terms. We intend to quantify the effects of combustion heat release and the transverse wave
structure on the vorticity budget terms. This investigation
is expected to guide full three-dimensional studies of theinteraction in the future.
Contact: ashwathsv@tamu.edu

Numerical simulation of detonation onset
from H2-air flame-shock interaction
Pascale Domingo1, Emilie Yhuel1, Guillaume Ribert2,
Nabiha Chaumeix1, Anthony Roque1
1

CNRS, France, 2INSA de Rouen, France

The interaction between a flame and a shock is examined in a numerical set-up representative of an experimental set-up based on a centimetric shock tube. A mixture of hydrogen and air at an equivalence ratio of 0.8 isfirst ignited at the end of the tube which leads to the development of a finger-glove flame toward which a shock isthen sent. Realistic mechanisms for the chemistry are employed along with an accurate description of the diffusion
including the Soret effect. Gravity is also included. The
wall temperature is fixed at 300 K which might appear
as a very stringent condition but is better justified thanadiabatic condition. The impact of the description of thegeometry (1D, 2D, and 3D) on the apparition of a transition
to detonation is studied for two values of the incident
shock Mach number. Depending on this Mach number,
two different types of DDT are observed: one related toshock focusing occurring close to the axis of symmetry of
the tube and a second type occurring in the vicinity of thereactive boundary layer. A comparison with experimental
results confirms the capacity of the numerical simulation
to capture the details of the flame/shock interaction andthe necessity of a 3D realistic geometry.
Contact: domingo@coria.fr

148



The structure of triple shock reflections
using the 10-moment method

William Morin, Fabien Giroux, Matei I. Radulescu, James G.
McDonald
University of Ottawa, Canada

The structure of a triple-shock configuration andits reflection, characteristic of the cellular structure ofdetonations, is solved numerically in two dimensions
using the 10-moment maximum-entropy model of gas
dynamics for diatomic gases. The results are comparedto the analoguous problem of single shock reflections
on a ramp, demonstrating the equivalence between thetwo problems. This study demonstrates the potential of
maximum-entropy based moment closures as an accurate alternative to traditional hydrodynamic models. The
10-moment model, derived from gas-kinetic theory, is thesecond member of the maximum-entropy moment closure hierarchy. These moment models are based on anassumed form of the distribution function describing thephase-space probability distribution of gas particles. The
10-moment model for diatomic gas yields a set of eleven
hyperbolic first-order balance laws capable of predicting
adiabatic viscous flow in both the continuum and rarefied
regimes. Its first-order nature provides numerical advantages such as a decreased sensitivity to mesh quality
and irregularities. The requirement for the evaluation of
only first derivatives also offers the possibility for an extra
order of spacial accuracy for a given stencil. The source
term used to model the inter-particle collisions is the
BGK relaxation-time collision operator. All calculations
are computed using a discontinuous-Galerkin-Hancock
scheme ensuring third-order accuracy in both space andtime. The simulations are run in parallel using adaptive
mesh refinement to accurately capture the solutions’structure.
Contact: wmori104@uottawa.ca

A molecular view of shocks and triple
points: implication on gas-phasedetonations
Amitesh S Jayaraman, Ethan S Genter, Hai Wang
Stanford University, United States

Hydrodynamics around triple point collisions are central to detonation cellular structure. From direct numericalsimulations, it has been observed that the vorticity generated at triple points and transported to behind the Machstem produces a high-speed jet that drives the Machstem. Although computational fluid dynamics shed lighton the dynamics within detonation cells, high-resolution

19th International Conference on Numerical CombustionTrack10 Detonation, explosions

simulations show that the vortex generation occurs at
length scales that can be comparable to the shock thickness, and hence approaches the realm of the molecularscale. In this work, we undertake a molecular dynamics
study of the shock and triple point regions of a nitrogenshock that undergoes Mach reflection off a wedge. We
observe a region of collision enhancement ahead of theshock and a 'hotspot' in the triple point region, and assess
their implications on gas dynamics and chemical kinetics.
Furthermore, we investigate the generation of vorticity
near the triple point region. The results of this study provide a better understanding of triple point structure that isuseful to numerical simulations of detonations.
Contact: amiteshs@stanford.edu

Shocks in n-dodecane/nitrogen mixtures:a molecular dynamics study
Ethan Samuel Genter, Amitesh Sivaraman Jayaraman,
Hai Wang
Stanford University, United States

Understanding the transport of long-chain hydrocarbons through shocks is relevant to spray detonation.
Shock interaction with aerosolized hydrocarbons in adiluent determines the ignition characteristics of the detonation, and by extension, the structure and stability of the
wave. The current study uses molecular dynamics simulations to investigate the molecular transport of n-dodecane in a N2 shock. The large temperature and density
gradients within the shock give rise to a thermophoretic
and pycnophoretic force, respectively, on the n-dodecane
molecules that could preferentially concentrate themahead of the shock front. Furthermore, n-dodecane molecules also tend to align in the direction of convective flow
within the shock, thereby perturbing the molecular diffusivity, and such diffusivity can be anisotropic. We observe
the phoretic transport and flow alignment in n-dodecane
molecules over a range of pre-shock gas conditions andshock strengths.
Contact: egenter@stanford.edu

Track10-3 Detonation,
explosions (3)Chair: Pascale Domingo
Friday, May 10; 09:50 - 11:50; Room B

Numerical simulations of the run-up
distance to detonation in hydrogenmethane blendsMilin Martin, Elaine S Oran, Ashwath Sethu
Venkataraman
Texas A&M University, College Station, United States

In this presentation, we show selected results fromusing the multidimensional reactive Navier-Stokes equations (RNSE) to simulate Deflagration-to-Detonation(DDT) in an obstacle-laden channel filled with stoichiometric hydrogen-methane fuel blends in air initially atatmospheric conditions. The new AMRFCT code is used
to solve the RNSE using the fourth-order Flux-CorrectedTransport (FCT) algorithm with appropriate source terms
on an adaptively refined Cartesian mesh. New multifuelChemical-Diffusive Models (CDMs) are used in the RNSE
to represent the chemical reactions leading to conversion
from fuel to product, related heat release, and physicaldiffusion processes. Each new CDM generates an optimized set of parameters that, when inserted in the RNSE,
reproduce critical flame and detonation properties of aparticular hydrogen-methane blend in air. We discuss how
these parameters are obtained for different blends. Of
particular interest here is a comparison of the run-up distance to detonation of these mixtures ranging from purehydrogen in air to pure methane in air.
Contact: milin333martin@tamu.edu

Revisiting the issue of deflagration-todetonation transition in an unconfinedsystem via highly-resolved 2D
axisymmetric simulations
Kazuya Iwata, Sho Wada, Ryoichi Kurose
Kyoto University, Japan

In most previous studies on deflagration-to-detonationtransition (DDT), a wall-confined system has been primarily considered since the reflected shocks and boundary
layer take substantial roles in accelerating flame to the
Chapman-Jouguet deflagration as the pre-initiation stage.
Discussion on DDT in an unconfined system has notreached a consensus yet with only a few relatively weaker experimental evidences. Even though there are few149Track10 Detonation, explosions

continuing efforts to evaluate its possibility, it is widelybelieved that DDT in an unconfined system is not feasible,
regardless of strong evidence such as Type Ia supernovae, whose observational outcomes are explained well by
DDT in unconfined media.
The authors perform 2D axisymmetric simulations
fully resolving the flame structure of unconfined H2/O2
mixtures. Equivalence ratios of premixed H2/O2 mixtures
are chosen to be 0.5 and 0.8 to reproduce the conditions explored by Kiverin et al. 2022 and Zel’dovich et al.
1947, respectively. Flame acceleration to Mach numbersof 0.3-0.35 at the radius of 2 cm, where the DDT wasdemonstrated in Zel’dovich et al. 1947, is observed in both
equivalence ratios, but DDT is never evidenced, whereasrougher-resolution studies succeed in DDT and direct initiation. These results pose a challenge to previous numerical studies where rougher resolutions were applied. The
effects of the intrusive ignition method in Zel’dovich et al.
1947 should be quantified in the future. Three-dimensional
resolved simulations are also being planned to capture
the flame dynamics quantitatively by applying an adaptive
mesh refinement (AMR) technique.
Contact: iwata.kazuya.6f@kyoto-u.ac.jp

Transition from autoignitive reaction
wave to detonation under transonicconditions for methane mixture

Haru Okada, Youhi Morii, Akira Tsunoda, Keisuke Akita,
Kaoru Maruta
Institute of Fluid Science, Tohoku University, Japan

A one-dimensional system where unburned premixed
gas enters from the inlet boundary and burned gas exits
from the outlet boundary is considered. A steady-statesolution is obtained when the inlet velocity is equal to
the laminar burning velocity under subsonic conditions orequal to the Chapman-Jouguet detonation velocity under
supersonic conditions. However, other steady-state solutions could exist, especially if auto-ignition occurs in thesystem as the inlet temperature increases. Such a reaction
waves, which stand at positions where residence times arevery close to ignition delay times, are termed as “autoignitive reaction wave.” While “autoignitive reaction wave” canbe obtained as steady-state solutions over a wide range
of inlet velocity conditions under high inlet temperaturesin the subsonic regime, it is not clear what solutions canbe obtained around the transonic regime. In this study,
1D transient reactive flow simulations were performed forthree inlet velocity conditions such as two subsonic andone transonic conditions using methane fuel. As a result,the detonation transition was confirmed when the spontaneous ignition front speed (inverse of the spatial gradi-150

ent of ignition delay time) exceeded the speed of sound.
This suggests that the detonation transition boundaryof “autoignitive reaction wave” is determined not only by
the shock transition in the transonic regime but also by
the relationship between the spontaneous ignition front
speed and the sound speed.
Contact: okada.haru.q6@dc.tohoku.ac.jp

Semi-Confined Reaction Zone Effects in
Gaseous Detonations
Stephen Voelkel, Mark Short, Carlos Chiquete
Los Alamos National Laboratory, United States

Motivated by rotating detonation engines (or RDEs),
we consider a continuous detonation in a channel geometry wherein the ambient state has two distinct zones:(1) a region of fresh reactant gases below some standoff
distance from the bottom of the channel, and (2) a region of inert product gases above the standoff distance.
The resulting flow is characterized by a detonation front
connected to an oblique shock, with a shear layer acting
as partial confiner between the reacting flow and postshock product gases. In this work, we will utilize a novel
shock-fitted, shock-attached frame to isolate and analyze
this system by treating the detonation front and oblique
shock as boundary condition of the flow field. Streamlinereflection and outflow conditions are utilized for the otherboundaries as needed. This work expands upon our previous studies by introducing an ambient state with two
distinct regions, thus allowing us to directly simulate theshear layer between the two flow regions. With this implementation, we will assess the effect of standoff distanceand confinement via the shear layer with regard to thedetonation propagation and stability.
Contact: svoelkel01@gmail.com

Detailed Numerical Simulations of
Explosive Post-Detonation Afterburning
Ryan Houim, Anthony Egeln
University of Florida, United States

Numerical simulations were performed in 3D Cartesian
coordinates to examine the post-detonation processes
produced by the detonation of hemispherical explosive
charges in air. The explosive charges considered were
PETN, which is nearly soot free, and TNT, which is very
sooty. The simulations captured air dissociation by theMach 20+ shock, chemical equilibration, afterburning using finite-rate chemical kinetics with a detailed chemical
reaction mechanism. Soot was modeled using an Euleri-

19th International Conference on Numerical CombustionTrack10 Detonation, explosions

an multiphase that considered combustion, sublimation,
agglomeration, and thermal radiation. The Becker-Kistiakowsky-Wilson real-gas equation of state was used forthe gas-phase. A simplified programmed burn model wasused to seamlessly couple the detonation propagation
through the explosive charge to the post-detonation reaction processes inside the fireball. The computed blast,shock structures, and chemical composition within thefireball agree with literature and companion experimental
measurements. The evolution of the flow at early times
is shown to be gas dynamic driven. At later times, theRayleigh-Taylor and Richtmeyer-Meshkov instabilities
promote mixing and produce a non-premixed turbulent
fireball between the fuel-rich detonation products andshock-heated air. A mixing layer and Damkohler number
analysis study revealed that the afterburning processes ofsmall bench-top scale charges is in a finite-rate reaction
regime while larger charges transition to a mixing-limited
regime. These results indicate that afterburning experiments utilizing small bench-top scale charges need to be
used with caution when scaling to larger-sized charges.
Contact: rhouim@ufl.edu

Track10-4 Detonation,
explosions (4)Chair: Kazuya Iwata
Friday, May 10; 13:00 - 15:00; Room E

Continuum Modeling of Steady 1-D and
2-D Detonation Wave Propagation in
Porous High Explosives
Joshua Garno, Mark Short, Carlos Chiquete, Stephen
VoelkelLos Alamos National Laboratory, United States

Structural irregularity in high explosive (HE) molding
powders results in granular resistance to compaction during pressing. Consequently, pressed HE contains residual
porosity which typically occupies about 1-3% of the HE volume. Thermal and mechanical damage can also lead to significant additional porosity in HE materials. It is well-known
that HE detonation performance properties are sensitive
to the initial HE density, or equivalently, initial porosity.
However, the driving physical mechanisms through whichporosity affects HE detonation phenomena have yet to be
described or modeled in detail. In this work, a continuum
modeling approach is used to examine the mechanisms bywhich porosity affects steady detonation wave propagation
in initially porous HEs. Finite-rate compaction of the porous
HE material is captured with an evolution equation for thesolid volume fraction. The initial porosity and compaction
viscosity of the HE are varied to explore their effects on
steady 1-D and 2-D detonation wave propagation. Resultsof 2-D flow computations, performed in an axisymmetric,
shock-attached, moving frame of reference, are compiled
to produce size effect curves parameterized by the initial
HE porosity and compaction viscosity.
Contact: jgarno@lanl.gov

Dynamics of Jet-Stabilized Detonation
Waves

Calvin Colby, Alexei Poludnenko, Sai Sandeep Dammati
University of Connecticut, United States

Supersonic jets play an important role in a wide range
of aerospace systems. The structure and behavior of inert supersonic jets, both over- and under-expanded, hasbeen studied extensively over the years theoretically andexperimentally. At the same time, reacting supersonic jets
have received far less attention. Under the appropriate
conditions, ignition can occur behind the Mach disk of ahighly under-expanded premixed jet, which can result in
the formation of a detonation wave. While conclusive experimental observation of such jet-stabilized detonation
waves (JSDW) is presently lacking in the literature, several
prior numerical studies have suggested the possibility of
their existence. At the same time, no comprehensive understanding of JSDW presently exists, including conditions
for their formation, as well as their structure and dynamics. Here, we describe a detailed theoretical frameworkfor predicting the conditions of the onset of a JSDW in a
2D slot jet with a single-step Arrhenius kinetics. We alsopresent a large suite of numerical simulations demonstrating the accuracy of this framework and exploring thestructure, dynamics, and stability of such JSDW. Finally, we
discuss future extensions of this model and its potential
relevance both for the fundamental detonation studies
and novel propulsion designs.
Contact: calvin.colby@uconn.edu

Flow characteristics of oblique detonation
wave/boundary layer interactions under ahypersonic reactive flow
Jie Sun1, Pengfei Yang2, Zheng Chen1

1
Peking University, China, 2Institute of Mechanics, Chinese Academy of
Sciences, China

Due to the high thermal cycle efficiency and compact combustor, oblique detonation engines hold great
promise in the field of hypersonic propulsion. Previous

151

Track10 Detonation, explosions

numerical simulations of oblique detonation waves havepredominantly solved the inviscid Euler equations, disregarding the influence of viscosity and boundary layers.
However, in real combustion chambers, the interaction
between oblique detonation waves and boundary layers
significantly alters the flow structure and diminishes engine efficiency. Therefore, this study conducts numericalsimulations considering detailed chemical mechanism andthe viscosity of the mixture to investigate the interaction
between oblique detonation waves and boundary layers
within combustion chambers. The results indicate thatthe wedge-induced oblique detonation wave generates
a strong adverse pressure gradient upon impacting theupper wall, leading to boundary layer separation. The separation zone subsequently induces an oblique shock wave
near the upper wall. While an increase in wedge angle
will cause the transition of oblique shock wave to obliquedetonation wave. Besides, the formation of the separation
zone reduces the actual flow area within the combustion
chamber, leading to a decrease in throat height. When thethroat height is small enough, flow chokes, causing theoblique detonation combustion to fail. The polar curve
analysis is employed to theoretically explain the formation
mechanism of the wave structure under different parameter conditions. The theoretical predictions closely alignwith the results in simulations. The findings of this study
provide new insights into the investigation of the influenceof viscosity and boundary layer effects on the structure of
oblique detonation waves.
Contact: 1901111626@pku.edu.cn

Detonation Cell Size Prediction with
Artificial Neural Networks and NonDimensional Features
Georgios Bakalis, Hoi Dick Ng
Concordia University, Canada

In gaseous detonations the cell size λ is commonlyused as the characteristic length to quantify the sensitivityof a detonation or to scale different dynamic parameters.
In this work we show how this cell size can be predictedusing Artificial Neural Network (ANN) models with different number and combination of input features. Thesemodels are trained and tested using experimental cellsize data for a wide range of reactive mixtures at different
initial conditions, combined with the corresponding chemical kinetics parameters, calculated using the steady ZND
model. Unlike our previous work, only non-dimensional
input features are used, which are created using the ZND
parameters. The cell size, which is the ANN prediction target, has also been non-dimensionalized with the induction
length (λ/Δi ). This approach leads to the development of152

slightly improved ANN models with a lower mean prediction error (19-23%) compared to the previously developed
dimensional ANN models. The predictions of these models appear to be more consistent when different input features are considered, requiring just 2 input features for agood cell size prediction and just 1 for an acceptable one.
Contact: georgios.bakalis@concordia.ca

Modulation of the Unstable Cellular
Detonation Structure with Microplates

Georgios Bakalis1, Chian Yan1, Kelsey Tang-Yuk2, Hoi Dick
Ng1, XiaoCheng Mi3
Concordia University, Canada, 2McGill University, Canada, 3Eindhoven
University of Technology, Netherlands

1

A detonation commonly exhibits an unstable cellular
frontal structure, which affects its propagation and dynamics at critical phenomena. In this numerical work weinvestigate the modulation of this frontal structure using aseries of thin, staggered micro-plates that are embeddedin the combustible mixture. Continuing on our previous
work, we now take viscous, thermal and momentum diffusion terms into consideration, meaning that the flow
is governed by the reactive Navier-Stokes equations,coupled with a two-step induction-reaction Arrhenius
chemical kinetics model. The results once again showthat a detonation with a regular cellular structure can beobtained from an irregular one that propagates throughspecific obstacle configurations, without significant velocity deficit. The modulated detonation shows a one-dimensional reaction rate profile that is closer to the ideal ZND,
and a burn mechanism mainly by shock compression.
Contact: georgios.bakalis@concordia.ca

What controls the cell size in gaseous
detonations?

Abeetath Ghosh, Sandeep Dammati, Alexei Poludnenko
University of Connecticut, United States

Detonation cell size is one of the central characteristics of a detonation wave due to its empirical correlation
with several key detonation properties, including minimum
channel size, critical tube diameter, etc. It is unclear if
modern multi-dimensional numerical simulations can predict accurately the detonation cell size for practical fuels.
Prior studies have reported a discrepancy for hydrogen-air
mixtures between the experimental measurements andcell size values computed using complex multi-step kinetics. Here we show that even larger disagreement
exists for a wide range of hydrocarbon fuels, including

19th International Conference on Numerical CombustionTrack10 Detonation, explosions

methane, acetylene, ethylene, and JP-10. Both the causeof this disagreement, as well as the fundamental mechanisms controlling the cell size, remain unclear. To help address these open questions, here we systemically analyse
the effect of activation energy and gas compressibilityon the detonation cell size in the context of single-stepkinetics. In particular, we explore the cell size dependence
on the induction length and thermal width, with the focus
on the relative importance of different shock over-drives,
which are present in a multi-dimensional detonation front.
Finally, we use these results to discuss potential limitations of the existing physicochemical models, which canlimit the accuracy of the predicted detonation cell sizes.
Contact: abeetath.ghosh@uconn.edu

Track10-5 Detonation,
explosions (5)Chair: TBD
Friday, May 10; 15:20 - 17:20; Room E

Influence of SGS combustion models in
LES of methane-air deflagration

Mahesh Somasani1, Vagesh D. Narasimhamurthy1, Trygve
Skjold2
Indian Institute of Technology Madras, India, 2UNIVERSITY OF BERGEN,
Norway1

Accidental gas explosions in fuel processing industries
are devastating. To understand the phenomenon at anindustrial scale, investigations are often performed on
small-scale geometries that may represent industrial-scaleconfigurations. In this study, a large eddy simulation (LES)
of methane-air deflagration in a semi-confined explosion
chamber was performed. The chamber includes threeobstacles sequentially placed at equal pitch. The sub-gridscale combustion models by Charlette et al. (Combust.
Flame, 2002) and Colin et al. (Phys. Fluids, 2000) were
implemented and assessed using the XiFoam (a premixed
turbulent combustion solver in OpenFOAM). XiFoam uses
the flame surface density (FSD) approach to model combustion. The predicted flame speed and the overpressure
time history were compared against the experimental
data by Patel et al. (Proc. Combust. Inst, 2002). Both models were able to reproduce the flame's accelerating anddecelerating behavior across the obstacles. The modelof Charlette et al. performs better in predicting the flame
speed than the model of Colin et al. Further, the predictedpeak overpressure by both models is in close agreementwith the experimental data. However, the time of occurrence of the peak is well captured by the model of Char-

lette et al.
Contact: am21d013@smail.iitm.ac.in

Numerical Modeling a Polymer-bonded
Explosive Frictionally Heated by an
Ultrasonic Horn
Kibaek Lee1, Alberto Hernández2, D. Scott Stewart3

Florida Institute of Technology, United States, 2Torch Technologies,
United States, 3University of Florida, United States

1

We present the numerical modeling of a polymer-bonded explosive which is frictionally heated by an ultrasonichorn. This experiment was conducted by the Dlott-groupat the University of Illinois (Men et al., J. Phys. Chem. C,2018). They observed a two-stage reaction of the explosive: The first stage occurred at the condensed-phase andthe second stage was due to the confined reactive gases
from the previous condensed-phase combustion. We examine the reaction path of frictionally heated explosives
by focusing on the first stage of the reaction. A 0.5 mm
length explosive surrounded by an inert polymer subjected to the ultrasonic horn is modeled. The two-component
Wide-Ranging equation of states (EOS) is used to model
the explosive materials while the Mie-Grüneisen EOS isused for the inert polymer. A harmonic boundary condition is applied to mimic the behavior of the ultrasonichorn in the experiment. The interaction between the explosive and the harmonic waves are mainly discussed.
Contact: klee@fit.edu

DDT as a Hopf bifurcation

Luc Bauwens1, Josue Melguizo-Gavilanes2
1

University of Calgary, Canada, 2Shell, Netherlands

There is evidence that the DDT process may be quitesensitive to apparent details in the kinetic scheme. Overly
simple schemes may not be truly meaningful. Complex
schemes claim realism, but they may not reproduce
experimental detonation results. While stiff integration
schemes ensure absolute stability, they do not actually resolve steps too fast to be resolved. Their complexity also
may stand in the way of a proper physical interpretation.
To gain understanding on the role of kinetics, we consider
a range of increasingly complex simplified schemes, up to
five steps, with two parallel chemical paths. A one-dimensional simulation follows a methodology relying on experimental flame acceleration data. This allows us to focus
upon and resolve the DDT process.
One might expect that when DDT occurs, one eigenvalue of the chemical Jacobian matrix, initially all nega-153

Track10 Detonation, explosions

tive, becoming positive. For both our three and five step
schemes, the independent term in the characteristic equation is positive definite, so that no eigenvalue is ever zero.
Instead, a Hopf bifurcation occurs: a complex pair sees its
real part go through zero. However, the independent term
being small, complex eigenvalues occur over a range sonarrow that it is mostly not noticeable in the results.
Contact: bauwens@ucalgary.ca

Effects of vitiation and thermal boundary
conditions on flame acceleration in
microchannels: A numerical study
Suryanarayan Ramachandran1, Navneeth Srinivasan1,
Zhiyan Wang2, Arsam Behkish2, Suo Yang1
University of Minnesota, Twin Cities, United States, 2ExxonMobil
Technology and Engineering Company, United States

1

Premixed hydrogen/air flame acceleration (FA) and thesubsequent deflagration-to-detonation transition (DDT) of
pure and vitiated fuel/oxidizer mixtures in a microchannel
at two extreme wall thermal conditions — an adiabatic wall
and a hot, preheated isothermal wall were numericallyinvestigated. We employed AMReX-Combustion PeleC, an
exascale compressible reacting flow solver that leverages
load-balanced block-structured adaptive mesh refinement(AMR) to enable high-fidelity direct numerical simulation(DNS). We found that the FA rate and hence the DDT runup distance to be strongly limited by the flame speeds ofthe unreacted mixture. Addition of water (i.e., vitiation) to
the unreacted mixture leads to a significant reduction in
the flame speed, thereby slowing down the FA process
and subsequent DDT. With isothermal preheated walls,
the pure fuel cases preferentially propagate along the wallafter an auto-ignition event, leading to the formation of a“secondary” finger-flame which subsequently undergoes
transverse expansion. The vitiated fuel cases also exhibit
a similar behavior, nonetheless exhibit much longer timescales of auto-ignition and propagation.

to resolve. In numerical simulations, the required time
step is dictated by the stiffness of the chemical model.
In this study, we examine 11 different hydrogen chemical
models using Computational Singular Perturbation (CSP)
technique to identify their smallest time scales (τ_min),with constant volume reactor. The conditions employedin the CSP analyses are determined from the postshock (von Neumann states) of Zel'dovich von Neumann
Döring (ZND) simulations relevant to H2-O2-3.76Ar. Grid
convergence analyses of unsteady one-dimensional (1D)
simulations, conducted with our in-house OpenFOAM
solver in shock-attached frame of reference, reveal thatthe required grid resolution is inversely correlated withthe smallest time scales identified in the CSP analysis.
Simulations conducted with Mével 2017’s and Burke 2012’s
chemical models, for which τ_min ~ 1 ns, are grid-independent when 48 points per induction zone length (pts/∆i)are employed, while at least 200 pts/∆i are required with
Mével 2023’s chemical model (for which τ_min ~ 0.05 ns).
Due to the close agreement of Mével 2023’s model withrecent experimental measurements of ∆i, grid convergence analysis is conducted with Mével 2023’s model in
two-dimensional (2D) simulations. In agreement with the
1D results, significantly finer grid resolutions, as comparedto the typical 20 pts/∆i, are required to obtain a grid-independent solution with such stiff detailed chemical model.
Such findings are relevant for the numerical simulationsof detonations with any chemical system for which stiff
chemical models are employed.
Contact: vigneshwaran.sankar@kaust.edu.sa

Contact: ramac106@umn.edu

A computational singular perturbationbased assessment of chemical models for
two-dimensional hydrogen detonation
simulations
Vigneshwaran Sankar1, Karl P Chatelain1, Rémy Mével2,
Deanna A Lacoste1
1

King Abdullah Unibersity of Science and Technology, Saudi Arabia,
Tsinghua University, China

2

Detonation simulations are challenging due to thewide spectrum of characteristic length and time scales154

19th International Conference on Numerical CombustionTrack11 Gas turbines, engines and furnaces

Track11-1 Gas turbines, engines
and furnaces (1)Chair: Masayasu Shimura
Wednesday, May 8; 13:30 - 15:10; Room M

Numerical investigation of effects ofammonia energy fraction and equivalence
ratio on emission characteristics ofammonia/diesel dual fuel engine

Azusa Fuse1, Yusuke Imamori1, Tomohiro Takahashi1,
Hiroyuki Ueda1, Takafumi Tanaka2, Ryosuke Kogure2,
Satoshi Yamada1

Mitsubishi Heavy Industries, Ltd., Japan, 2Mitsubishi Heavy Industries
Engine & Turbocharger, Ltd., Japan

1

Emission characteristics of ammonia/diesel dual fuelengine is studied by LES with detailed chemical kinetic
solver. Otomo mechanism for ammonia and ERCv2 forn-heptane are used in this study. LES is operated under
several conditions with different ammonia energy fraction
up to 94% and equivalence ratio conditions up to 0.91.
The simulation results show that unburnt ammonia
and N2O are reduced simultaneously with increasing
ammonia fraction, while NO is increased. Vice versa withdecreasing equivalence ratio.
As for the higher ammonia energy fraction condition,
conditional mean statistic show that a rise of adiabatic
flame temperature due to the increase of ammonia equivalence ratio enhances (i) consumption of ammonia whichis released from narrow space such as crevice of piston
top ring while expansion stroke, (ii) decomposition of N2O
in burnt region by reaction N2O(+M)=N2+O(+M) which
has higher temperature dependence among N2O related
major reactions, and (iii) production of NO in burnt region
while NO in reaction zone is almost the same as the lower
ammonia energy fraction condition.
The comparison between simulation results and actual engine test results showed that the simulation reconstructs the tendency of aforementioned exhaust gaschange, which suggest the validity of the simulation.
Contact: azusa.fuse.f3@mhi.com

Exploring the Physical Significance ofRobust Wiebe Function Parameters
Through the Application of Artificial
Neural Networks to Enhance the Analysis
of Combustion in Internal Combustion
Engines
Kartikkumar Thakkar, Sheshadri Sreedhara
Indian Institute of Technology Bombay, India

In the present study, the artificial neural network (ANN)
has been utilized to combine the CFD (3D) and 0D models
by training the neurons through the results obtained fromthe validated CFD model to estimate the parameters of amodified Wiebe function. The new and robust triple Wiebe
function used in the present study is modified to exclude
the assumption of arbitrarily selecting the value of efficiency parameters. The value of the correlation coefficient(R) for the training, testing, and validation is obtained as>0.99 for the estimation of Wiebe function parameters foreach of the three combustion stages, which justifies thepredictability of the present model. The physical interpretations of Wiebe function parameters corresponding toengine operation parameters (load, speed, compression
ratio, fuel injection timing, and fuel spray angle) have also
been studied. The results suggest that the present robust
Wiebe function parameters can be satisfactorily used tomap the engine operating parameters as well as performance parameters; therefore, the trained ANN model canbe effectively used to optimize the engine performanceparameters.
Contact: thakkarkartikc@yahoo.in

Low Carbon Industry: Electrificationof industrial processes involving hightemperatures
Jetnis Jetnis Avdijaj

Université libre de Bruxelles, Belgium

Industries are responsible of 26\% of the global CO2
emissions in the world in 2022 [1]. Therefore, this sector
must reduce that figure to reach our sustainability goals
by 2050. One possible path of decarbonization could
be electrification of some fossil fuel intensive processes.

155

Track11 Gas turbines, engines and furnaces

However, electrification cannot match the temperature
requirement in all processes. Here the slab reheating furnaces used in the steel industry are considered.
The parameters that define the quality of the final
product exiting these furnaces, used for thermal treatment, are the atmosphere composition and slab temperature. Therefore, reheating furnaces have a final low
power zone, the soaking zone, to control the parameters
mentioned before. This work studies the influences ofthe electrification of the soaking zone on the atmospherecomposition and slab temperature. It investigates the useof electric heating elements instead of natural gas burners in the soaking zone. This has been done by comparing
experimentally validated CFD results of a conventionalslab reheating furnace model with CFD results of the hybrid furnace model where electrification goes up to 5MW
in the soaking zone. Results show that the crucial process
linked parameters remain similar (maximum 2\% variation) to the conventional process.
[1] IEA (2023), CO2 Emissions in 2022, IEA, Paris https://www.iea.org/reports/co2-emissions-in-2022, License:
CC BY 4.0
Contact: jetnis.avdijaj@ulb.be

Identification of recirculation zones fromexperimental images of trapped vortex
combustors using deep learning
Tanaya Mallik, Priyabrat Dash, Nikhil Verma, R. V.
Ravikrishna, Konduri Aditya
Indian Institute of Science, Bengaluru, India

Trapped vortex combustors (TVCs), with potential applications in stationary gas turbine engines and compact
aero-engines, exhibit a steady and locked primary recirculation zone (PRZ) in the cavity. It functions as a continuous source of enthalpy and radicals for combustion, contributing to enhanced combustion efficiency. Identifying
the PRZ is critical for studying the combustion dynamics
of such devices, an exercise typically conducted using
particle image velocimetry (PIV) data. However, using tracer particles seeded into the fluid flow for measurements
might introduce inaccuracies, especially in reacting flows.
The consequences include the smearing of high-temperature gradients and the seed particles clogging the nozzles,
thereby altering the effective inlet velocity of the fluid. To
mitigate this, we investigate coupling a non-invasive diagnostic technique like OH chemiluminescence with deeplearning to estimate the velocity components of large
scales concerning the PRZ. After training and validating
the model on datasets from large eddy simulations, wetest it on snapshots obtained from simultaneous PIV and

156



PLIF measurements. A satisfactory agreement between
network outputs and ground truth has been observed interms of the mean squared error and PDFs. Such models
lay the foundation for intelligent data assimilation fromexperiments and simulations.
Contact: tanayamallik@iisc.ac.inTrack11-2 Gas turbines, engines
and furnaces (2)Chair: Matthias Ihme
Wednesday, May 8; 15:30 - 17:10; Room M

Impact of excess air factors as a
combustion parameter on NOx emissions
in a 207 MW model industrial furnace
Mansur Aliyu

King Fahd University of Petroleum & Minerals, Saudi Arabia

The environmental impact of NOx emissions is substantial, leading to various adverse effects. NOx, comprising primarily nitrogen dioxide (NO2) and nitric oxide (NO),emerges as pollutants from combustion processes in
power plants, vehicles, and industrial facilities. Recognizing the detrimental influence of NOx on the environment,
the implementation of specific emission control technologies becomes imperative to mitigate its harmful effects.
This study investigated the impact of operational parameters, specifically the excess air factor (α), on the NOx
emissions from a 207 MW model industrial furnace used
for steam generation in a boiler. The numerical approach
employed for this investigation utilized ANSYS-Fluent. The
study focused on a blended fuel composed of a mixtureof methane and hydrogen. The governing equations, developed based on physical principles and assumptions,were solved using various models, including turbulentk-ε, species transport with the eddy dissipation concept
for chemistry, and a NOx formation model. The findingsof the study revealed robust correlations between α,
temperature, and NO emissions. An increase in α led toa decrease in both the average furnace temperature andaverage NO emissions at the exit. Specifically, a 27% increase in α resulted in approximately a 55% reduction in
NO emissions.
Contact: mansur.aliyu@kfupm.edu.sa

19th International Conference on Numerical CombustionTrack11 Gas turbines, engines and furnaces

Elucidation of heat transfer
characteristics and NOx reduction
phenomenon of elliptical radiant tube
Tomoyuki Kawashima1, Akihiro Kobayashi1, Hiroaki
Watanabe2
1

JFE Steel Corporation, Japan, 2Kyusyu University, JapanThe radiant tube is an indirect heating device whichtransfers the heat of combustion inside the tube to thesteel plate by radiation from the outer surface of the tube.
The radiant tube is easy to maintain in the non-oxidizing or the reducing atmosphere around the object to beheated, so many industrial furnaces adapt to the radianttube. On the other hand, since the heat of combustionis generated in the closed space in the tube, the tube
often is creep-deformed at high thermal load. As a countermeasure against this deformation, the rigidity in the
deformation direction is enhanced by making the shapeof the radiant tube elliptical. In addition, the elliptical radiant tube having the same short diameter as diameter ofthe circular radiant tube increases the surface area andimproves the heat transfer efficiency compared with thecircular radiant tube. In this study, combustion characteristics and heat transfer characteristics of elliptical radianttube were investigated using three-dimensional numericalsimulation. As a result, the elliptical radiant tube obtains
the same or higher thermal efficiency compared with thecircular radiant tube. In addition, in the elliptical radianttube, NOx emission is lowered in comparison with theconventional circular radiant tube.
Contact: tom-kawashima@jfe-steel.co.jp

Development of a DEM-CFD coupling
simulation for the stoker type waste
incinerator

Ryusei Hayatomo, Tomohiro Denda, Takashi Nakayama,
Takahiro Matsumoto
JFE Engineering Corporation, Japan

In our company, we have analyzed the combustion of astoker type waste incinerators using Computational Fluid
Dynamics (CFD) simulations and utilized the results to improve furnace design and operation.
Recently, the performance requirements for incinerators, such as increased combustion stability and power
generation efficiency, have become more advanced,
therefore more detailed and accurate simulation of furnace phenomena is needed. In response to this, we aredeveloping on the combustion simulation technology that
coupling CFD and Discrete Element Method (DEM).
DEM is a method used for discrete calculations of parti-cle behavior, and has been attracting attention to analysis
techniques coupling with CFD because the computational
cost has been greatly reduced by recent improvements incomputer performances. When applying DEM to simulate
the combustion in stoker type waste incinerators, we simulate the transport behavior of waste within the furnace
by representing the waste as particles, and we also calculate the evaporation, volatilization, and solid combustionof the waste. By coupling these calculation results withthe gas combustion results obtained from CFD, our final
goal is to obtain a more detailed and accurate simulation
results of overall furnace combustion phenomena. In thispresentation, we will report on the status of our development.
Contact: hayatomo-ryusei@jfe-eng.co.jp

Numerical Investigation of CH4/O2/CO2
premixed flames stabilized over a dual
annular counter-rotating swirl burner
Mohammed El Adawy1, Medhat A. Nemitallaha2

King Fahd University of Petroleum and Minerals, Saudi Arabia, 2 King Fahd
University of Petroleum and Minerals, Saudi Arabia

1

Abstract: This study investigates oxy-methane (CH4/
CO2/O2) premixed flames within a dual annular counter-rotating swirl (DACRS) burner using numerical simulations. The burner structure comprises two concentric
tubes: an inner tube for primary gas flow and an outerannular area for secondary gas flow. Maintaining a constant oxygen fraction (OF) of 34 vol % in both primary andsecondary streams, the primary gas stream velocity is set
at 5 m/s, while three secondary velocities (1.289, 1.667, and
2.2 m/s) are explored to analyze flow-flame interactions at
different velocity ratios (3.878, 3, and 2.27). The Ansys-Fluent 2022-R1 software utilizes the partially premixed combustion model to simulate the reaction kinetics of the produced stratified flames within a three-dimensional periodic
domain. Thermochemical properties and reaction rates
are averaged using a probability density function (PDF)
model. Validation against experimental data includes axial
and radial temperature profiles and OH* concentration
maps corresponding to visual flame appearances. The
findings underscore highly effective interactions between
the flame and airflow, yielding thorough combustion andnotably diminished emissions within the DACRS stratified
flames.
Contact: mohammed.eladawy@kfupm.edu.sa157

Track11 Gas turbines, engines and furnaces

Track11-3 Gas turbines, engines
and furnaces (3)Chair: Reo Kai
Thursday, May 9; 09:50 - 12:30; Room I

Hydrogen combustion and NOx
generation characteristics for a scaledhydrogen-fueled gas turbine combustor
for aircraft propulsion
Junji Shinjo1, Keiichi Okai2

1

Evaluation of Preferential Diffusion in
RANS Simulation of H2-Air Turbulent
Flames with FGM Model

Alex M Garcia1, E. M. Fortes2, E. J. Perez-Sanchez2, D. Mira2,
M. Vivenzo1, M. Gauding1, Heinz Pitsch1, Nico Schmitz1,
Herbert Pfeifer1

1
RWTH Aachen University, Germany, 2Barcelona Supercomputing Center,
Spain

The use of hydrogen as a fuel has gained significant attention for reducing CO2 emissions in high-temperature industries such as steel and aluminum production. However,hydrogen exhibits special combustion characteristics thatdiffer from conventional hydrocarbon fuels, such as high reactivity and diffusivity. Therefore, the utilization of pure hydrogen as fuel requires significant modifications to existing
combustion systems. In this context, Computational Fluid
Dynamics (CFD) simulation is an essential tool for understanding, designing, and optimizing technologies operatingwith hydrogen. Reynolds-Averaged Navier-Stokes (RANS)RANS simulations are generally preferred for engineering
applications involving complex and large-scale geometries
due to the lower computational cost. Accurately modelinghydrogen combustion is challenging, particularly within the
RANS simulations framework, since combustion models aremainly developed assuming unity Lewis number, ignoring
effects such as preferential diffusion.
This paper presents a preliminary assessment of theeffect of non-unity Lewis numbers in RANS simulations of
H2-air turbulent flames by utilizing a recently developed
version of the Flamelet Generated Manifolds (FGM) model that includes preferential diffusion. This FGM modelaccounts for mixture-averaged transport in the flamelets
computed to construct the manifold and introduces additional diffusion terms to the transport equations of thecontrolling variables. Numerical simulations of hydrogenturbulent flames are conducted with and without considering preferential diffusion to observe its effect on
the mean flame fields. Furthermore, a comparison withdetailed chemical Direct Numerical Simulation (DNS) enables us to examine whether using a β-shape Probability
Density Function (PDF) to model the turbulence-chemistry interaction is adequate for lean premixed hydrogen
flames, where synergistic interactions of thermodiffusive
instabilities and turbulence are present.
Contact: garcia-vergara@iob.rwth-aachen.de158



Shimane University, Japan, 2Japan Aerospace Exploration Agency, Japan

Hydrogen combustion is one of the promising combustion methods for gas turbines to achieve carbon
neutrality. Hydrogen has several particular combustion
characteristics such as high flame speed and high flame
temperature, and thus its behavior should be well understood for applications in aircraft engines. In this study,
combustion and NOx generation dynamics of hydrogen
flame is investigated in the LES framework. The thickened
flame model is used to characterize the chemistry. The
target combustor is JAXA’s mode combustor which has
multiple small-scale swirl-stabilized injectors, which quickly mixes hydrogen and air in the upstream region. The
ambient pressure and equivalence ratio are varied to see
the effect on exit temperature and NOx generation. Dueto recirculation, a stable flame is formed and NOx generation occurs after some resident time. The pressure effecton the exit temperature is not strong and NOx generation
is mostly correlated to local temperature. The effect of
reducing the flow temperature by modulating the equivalence ratio on NOx generation is also discussed.
Contact: jshinjo@ecs.shimane-u.ac.jp

Combustion and emission characteristicsof oxy-syngas O2-CH4/H2/CO flames
in a swirl premixed model gas turbine
combustor
Medhat Ahmed Nemitallahking fahd university of petrolum and minerals, Saudi Arabia

This study investigates numerically the combustionand emission characteristics of CH4/H2/CO syngas
flames in a swirl premixed model gas turbine combustor
under oxy-combustion conditions for ease of exhaust CO2
capture. Simulations were performed over wide range ofsyngas composition at fixed inlet velocity of 6 m/s, equivalence ratio of 0.42, and oxygen fraction (OF) of 60%.
The model was validated against the experimental data
recorded on the same physical combustor setup. The
results showed that increasing the hydrogen fraction (HF)from 0 to 80% of the syngas while keeping the remaining
percentage of the syngas mixture equally divided between
CO and CH4, a decrease in thermal power (TP) from 4.0
to 3.7 Kw, a rise in adiabatic flame temperature (AFT) from2312 to 2388 K, a rise in laminar flame speed (LFS) from
0.53 to 1.32 m/s, and a decrease in power density (PD)19th International Conference on Numerical CombustionTrack11 Gas turbines, engines and furnaces

from 2854 to 2672 kw/m3 are observed. Excluding CH4, adecrease in AFT from 2447 to 2560 K, a decrease in LFS
from 2.01 to 0.46 m/s, an increase in TP from 3.64 to 4.1
Kw, and increase in PD from 2620 to 2923 kw/m3 wereobtained when decreasing HF from 90% to 10%.
Contact: medhatahmed@kfupm.edu.sa

Turbulent combustion model sensitivity
in LES of model gas-turbine combustor
Alessandro Ercole1, Daniel Lörstad2, Christer Fureby1
1

Lund University, Sweden, 2Siemens Energy AB, Sweden

In this study, a model gas turbine combustor featuringa premixed swirl-stabilized flame is simulated with finite
rate chemistry Large Eddy Simulation (LES). The design,originating from the Swedish National Center for Combustion Science and Technology (CECOST), aims to replicate
the flow and flame features of an industrial gas turbine
combustor under atmospheric conditions. A 10.5 million
cells hexahedral grid with local refinement in critical regions is used. The simulations, performed in OpenFOAM,
target a lean, stable, methane-air flame. Using the pathway centric 42 step reaction mechanism of Zettervall
et al. together with the Eddy Dissipation Concept (EDC),
Partially Stirred Reactor (PaSR), and Quasi Laminar (QL),
combustion models we assess the influence against experimental data, through OH- and CH2O-PLIF, as well
as PIV measurements. Good qualitative and quantitative
agreement is obtained but differences between models
are also observed in temperature and species distributions, impacting flame characteristics and dynamics. Notably, the EDC displays a more intense, more compact flamewith effective stabilization, while PaSR exhibits complex
dynamic phenomena involving large-scale fluctuationsof the flame front. Findings emphasize the sensitivity oflean methane-air flame simulations to combustion model
selection, with implications for broader applications wheremodel differences may rival those from distinct alternative
fuels, or operating conditions.
Contact: alessandro.ercole@energy.lth.se

LES of spray combustion in a lean direct
injection combustor using a novel
subgrid-scale stress model

Yicun Wang1, Kun Luo1, Hualin Xiao1, Tai Jin1, Jiangkuan
Xing2, Jianren Fan1
1

Zhejiang University, China, 2Kyoto University, Japan

Large eddy simulation (LES) of spray combustion is an
important tool for developing and designing new-gener-ation aero-engine combustors, and various subgrid-scale(SGS) closure models for LES have been developed.
Turbulent combustion, accompanied by strong turbulence-combustion interactions, plays an important role inaero-engine combustors. However, the influence of combustion on turbulence is rarely considered in previous SGS
turbulence modeling. In the present work, we develop anovel SGS closure model considering combustion effects
and name it the flame surface and k-equation based gradient model (FKGM). LES of spray combustion in the NASA
Lean Direct Injection (LDI) combustor is conducted tovalidate the FKGM model and analyze the complex spray
flame structure. The FKGM model achieves better agreement with the experimental measurements comparedwith the dynamic Smagorinsky model (DSM) in terms ofgas mean and fluctuating velocities, which indicates themodel's accuracy. Radial profiles of temperature, major
combustion products, and droplet diameters are also well
reproduced in the current simulation. The inner recirculation zone (IRZ), small outer recirculation zones, and threemain flame zones are well captured. The flame index is
introduced to identify different combustion regimes in thecomplex spray flame where both premixed and diffusion
regimes coexist. Quantitative statistics related to the heatrelease rate show that the heat release intensity of thepremixed flame regime is higher than that of the diffusion
regime.
Contact: wangyicun@zju.edu.cn

Large eddy simulations for investigating
combustor-turbine interaction: a machinelearning approach to reduce discrepancies
between single-component and multicomponent simulations
Jingke Su, Anxiong Liu, Kun Luo, Jianren Fan
Zhejiang University, China

The aerodynamic and combustion interaction acrossthe combustor and axial turbine in a micro gas-turbine
engine is studied by a high-fidelity 360 degree azimuthal
large-eddy simulation. By comparing with the standalone
combustor or turbine cases, the fully coupled combustor-turbine simulation shows a significantly different flow
field. Coupling with the axial turbine downstream, temperature uniformity (OTDF) near the combustor exit increases, which causes severe hot streaks on the turbine blades.
Next, we apply the distribution of total temperature andpressure obtained from the interface of coupled combustor-turbine simulation to the outflow/inflow boundariesof the standalone combustor/turbine cases. The results
thereby show the aerodynamic and combustion predictions of standalone cases now switch to be consistent159

Track11 Gas turbines, engines and furnaces

with the coupled combustor-turbine results.
As multi-component simulations are not very effective in the engineering field, people are used to conduct
single-component simulations for research and design.
In this work, we propose a machine learning method toapproximate single-component results to the multi-component simulation. A convolutional neural networks (CNN)
approach to train the trivial outflow/inflow boundary conditions of standalone combustor/turbine cases, to obtain
the interface distributions of the multi-component simulations in a range of operation conditions (different mass
flow rates and pressures) and varying installation angleof the turbine stator blades. The CNN predicted interface
can thus be applied as new outflow/inflow boundary conditions for the standalone combustor/turbine cases toapproximate the multi-component simulation results withan excellent generalisation.
Contact: sujingke@zju.edu.cn

Effects of Detailed Chemistry andMolecular Differential Diffusion on a
Reacting Jet in Cross-Flow

Gihun Shim1, Navneeth Srinivasan1, Taaresh Sanjeev
Taneja1, Vishal Acharya2, Suo Yang1

University of Minnesota, United States, 2Georgia Institute of Technology,
United States

1

Significance of a jet in cross-flow (JICF) lies in practicalapplications in combustion systems, like gas turbines,
emission controls of pollutants resulting from incomplete
mixing, and aircraft engine performance for higher thrustcapabilities. In this study, we simulate three distinct JICF
scenarios: non-reacting (NR) and two reacting cases (R1and R2). In the R1 case, the flame exists external to thejet shear layer, while in the R2 case, the flame resides
within the jet shear layer. To achieve this, we employ our
in-house reacting flow solver developed based on OpenFOAM and Cantera, to investigate the impacts of detailed
chemistry, mixture-averaged transport models, and vorticity structures within cases. Specifically, we demonstrate
the following: (i) A single-step chemistry model demonstrates reduced jet velocity, resulting in notably weaker
shear layer vorticity formations and the presence ofnarrow, high-endothermic lines. Conversely, the detailed
chemistry setting portrays wider endothermic areas without a flame on the windward side. (ii) Detailed mixture-averaged transport models can exhibit an attached flame forR1 and R2 cases, consistent with experimental results. (iii)
The vorticity structure analysis shows shear layer vorticity,horseshoe vorticity, and counter-rotating vortex pairs depending on a ratio of the crossflow and jet flow velocities.
Contact: shim0228@umn.edu

160Track11-4 Gas turbines, engines
and furnaces (4)Chair: TBD
Friday, May 10; 09:50 - 11:50; Room I

Prediction of heat release and wall heattransfer in a scramjet combustor via
Pareto-efficient combustion modeling
Matthew Bonanni1, Andrew Norris2, Matthias Ihme1

Stanford University, United States, 2NASA Langley Research Center, UnitedStates1Modeling supersonic combustion presents significant
challenges for tabulated chemistry approaches, leading
to inaccurate reconstruction of the thermochemical state,chemical species, and heat release rate. Furthermore, tabulated chemistry models perform poorly near walls, where
nonadiabatic conditions and recombination reactions
cause inaccurate heat flux predictions. We extend the Pareto-efficient combustion (PEC) model to supersonic combustion and simulate the RC19 scramjet combustor. Sensitivity analysis is performed to determine chemical species
most strongly impacting the heat release prediction. By
appropriate selection of the parameters of the PEC model,
we show that accurate predictions of total heat release
and wall heat transfer may be recovered via application offinite-rate chemistry to less than 15% of the computational domain.
Contact: mbonanni@stanford.edu

Numerical modelling of combustion
stability prediction in a dual mode ramjetwith a cavity flameholder

Mehdi Riis, Alessandro Piscopo, Alessandro Parente, Axel
Coussement
Université libre de Bruxelles, Belgium

The renewed interest of the aeronautics industry in
hypersonic propulsion systems led to new experimental
studies of dual mode ramjets (DMR). Still, the transition
from supersonic to hypersonic regime could show an oscillating behavior as the combustion shifts from subsonicto supersonic. However, experimental data is still scare in
the literature. Computational Fluid Dynamics (CFD) represents a viable alternative to study the behavior of suchengines. Where cold flow simulations could be considered
as predictive, the combustion process and stabilization
is more complex to capture. In this context, the Partially
Stirred Reactor (PaSR) model is evaluated in the DMR
context.

19th International Conference on Numerical CombustionTrack11 Gas turbines, engines and furnaces

To this end, 2D and 3D RANS simulations are performed on a cavity-based scramjet. The PaSR model iscompared to both the tabulated chemistry assumption(FGM) and the Eddy Dissipation Concept (EDC) model, another reactor-based model. The results of the simulations
show an improved prediction of both the backpressure
and the flame anchoring locations. Furthermore, 3D effects are investigated together with a sensitivity analysisof the chemical timescale formulation.
Contact: mehdi.riis@ulb.be

NOx Formation Analysis Applying
Clustering Method using Adversarial
Autoencoder to numerical results on
Hydrogen-Rich Ram Combustion with LES
Kotaro Nakayama1, Koichi Omi1, Hideyuki Taguchi2,
Kengo Takizawa1, Shinji Nakaya1, Mitsuhiro Tsue1

1
Department of Aeronautics and Astronautics, The University of Tokyo,
Japan, 2Japan Aerospace Exploration Agency, JapanNOx formation in a hydrogen-fueled model ram-combustor for a Pre-Cooled TurboJet (PCTJ) engine which
operates afterburner in hydrogen-rich conditions wasnumerically investigated with Large Eddy Simulation (LES).
For comparison, analysis in hydrogen-lean conditions was
also conducted. Combustion proceeded faster in rich conditions than in lean conditions due to the larger momentum ratio of fuel jet to mainstream air. The LES results
which are multi-dimensional and large-size data were
mapped to the 2D latent space and classified into 7 classes by Adversarial AutoEncoder (AAE) which is one of the
deep clustering methods using a generative model. The
contributions of the main NOx formation routes in eachclass were calculated. It was shown that almost all NO
was formed by the thermal NO route in reaction zones
and high-temperature air-side diffusion layers. It was also
demonstrated that NO was reduced in hydrogen-richburnt gas and fuel side diffusion layers because there are
H and NH radicals and few O radicals. It was concluded
that hydrogen-rich combustion was advantageous for hydrogen-ram combustors in terms of quick completion of
combustion and NO reduction in burnt gas. Additionally,
it was also confirmed that AAE clustering was effectivein NOx formation investigations in complex combustion
fields.
Contact: nakayama-koutaro327@g.ecc.u-tokyo.ac.jp

Wavelet optical flow velocimetry of ascramjet combustor using high-speed
frame-straddling focusing schlieren
imagesBo ZhouSouthern University Of Science And Technology, China

Velocity field measurement under extreme conditions
such as a scramjet engine presents great challenges, featuring ultra-high-speed turbulent reacting flow, high-temperature with intense luminescence. The present work
demonstrated a seedless velocimetry approach using focusing schlieren images (FSI) of high spatiotemporal resolution in a scramjet engine. Two fuel mass flow rates were
investigated with corresponding global equivalence ratios
of 0.27 and 0.13, respectively. The FSIs enabled by theemployment of a high-speed pulsed LED light source arecharacterized by an effective exposure of 100 ns, and a
500-ns frame-straddling time interval with a full resolution
recorded at 76 kHz. The 100-ns exposure allows for capturing of transient high-speed flow motion without blurring, and the 500-ns time interval ensures an appropriate
spatiotemporal correlation between subsequent schlieren
images for high-speed reacting flows. Wavelet-based optical flow velocimetry (wOFV) algorithm was developed andapplied to the FSIs. In contrast to the correlation-basedalgorithms widely employed in PIV for distinct particles,
wOFV algorithm turns to optimize a penalty function
which suits better FSIs with continuous variation in brightness. The maximal velocities in the main duct of thescramjet combustor were measured to be approximately
550 m/s and 1100 m/s for two cases studied, suggestively
corresponding to subsonic and supersonic combustion
modes, respectively. Velocity inside the cavity is generally
below 200 m/s for both cases. Recirculation regions andtheir dynamic motion inside the cavity were well resolved
from the measured flow field at 38 kHz. In summary, thedevelopment of present velocimetry approach holds great
potentials for applications in extreme flow conditions.
Contact: zhoub3@sustech.edu.cn

A Bayesian optimization framework forthe control of combustion instability of a
bluff-body stabilized combustor
Changxiao Shao

Harbin Institute of Technology, Shenzhen, China

Combustion instability is one of the significant problems affecting safety in modern gas-turbine combustors.
Temperature and pressure peaks due to combustion instability are particularly harmful for the structural damage161

Track11 Gas turbines, engines and furnaces

they can cause as well as for performance degradationand increase of pollutant emissions. Control of combustion instability for a realistic gas-turbine combustor ischallenging. This work aims to establish an efficient numerical framework for optimization to improve the combustion stability of a bluff-body combustor. High-fidelity
large eddy simulations of the spray combustion process inthe combustor are conducted and the experimental measurements are used to evaluate the numerical accuracyof the baseline case. The air preheating temperature, theSauter mean diameter of fuel droplets and the location ofliquid fuel injection are regarded as input variables. The
rms of pressure is regarded as an optimization objective.
The Bayesian optimization framework is proposed that includes the sampling process, surrogate model, acquisition
function and genetic algorithm optimizer processes. It isfound that Prms can be reduced by 86% for the optimized
case compared to the baseline case using only 16 sample
evaluations. The present framework is easy to be extended to multi-objective framework that considers the NOx
emission as an additional objective. This work is promising
as it provides an effective optimization framework for thedevelopment of next-generation gas-turbine combustors.

LES analyses, a computationally less demanding analysis
methods combining an extremely thin 3D geometry model and a simple one-step chemical reaction model wasapplied. As a result, the combination of the appropriate
modeling methods was able to qualitatively reproduce thepressure distribution in the RBCC engine and the mixing
flow behavior inside the flame holder of the scramjet engine.
Contact: moriarty@neptune.kanazawa-it.ac.jp

Contact: shaochangxiao@hit.edu.cn

Investigation of the simple CFD methods
to predict the flame holder flow field of
the hypersonic jet engines
Kotaro Iguchi, Hideki Moriai

Kanazawa Institute of Technology, JapanThe development of hypersonic engines such as
scramjet engines with high enthalpy flow requires largescale test facilities, many hardware fabrication and testingtrials, manpower, and time for these processes. Therefore,
the application of CFD simulation is important to save thehuge development cost and time. However, CFD analysis
of such flow is not only technically challenging and needs
huge amount of computer resources, but also the current
prediction accuracy is not always enough. This makes theapplication to multi-objective optimization needed forspeedy hardware design and development rather difficult.
Therefore, the purpose of this research is to develop
simple simulation methods that can perform supersonic
combustion flow field calculations on a workstation. Since
flame holding inside a hypersonic engine is a difficult andimportant technique, this research focuses on flame holders of the hypersonic engines. In order to accommodate
various flame holder flow fields, two types of hypersonicengines were selected for simulation trial: A Rocket-Based
Combined Cycle (RBCC) engine and a scramjet engine. For
the results of the hypersonic wind tunnel tests and full 3D162

19th International Conference on Numerical CombustionTrack12 Fires

Track12-1 Fires (1)Chair: Sayaka Suzuki
Thursday, May 9; 09:50 - 12:30; Room E

Large-Eddy Simulation of aeronauticalfire certification: coupling strategies for
multi-physics modeling

Roxane Letournel1, Adrien Grenouilloux2, Renaud
Mercier3, Vincent Moureau2
1

SAFRAN Tech, France, 2CORIA, France, 3SAFRAN Tech, France

Fire certification stands as a crucial milestone in the
aeronautical product development cycle. During thisprocess, the component to be tested is exposed to a kerosene burner-induced flame for 5 to 15 minutes. The notable failure rates in fire resistance tests lead to long andcostly development phases. Leveraging numerical simulation holds promise for comprehending the thermal impactof the flame and optimizing material design. These tools
are essential in addressing emerging challenges, including
evolving certification standards, the use of complex materials such as composites and assemblies, and the arrivalof alternative fuels.
To this purpose, we present a methodology forLarge-Eddy Simulation (LES) of certification burners,
encompassing a wide range of multi-physics and multi-scale phenomena: turbulence, fuel injection andatomization, spray combustion, conduction within solid
components, and conjugate heat transfers at the interface. This methodology couples a low-Mach number
combustion solver, a solid solver, and a radiative solver,
relying on the CWIPI library. With appropriate communications, solvers can independently but simultaneously
address reactive processes within the flame, thermal
conduction in a solid material, and radiative heat
fluxes throughout the domain. Recent developments
in numerical, meshing, and coupling strategies havesignificantly reduced the computational time of such
simulations, thus enabling the application of the methodology to well-controlled fire resistance tests undervarious operating conditions and for different burners.
Prediction of heat transfers is validated on a simplified
test case by comparing the temperatures of a well-instrumented metal plate impacted by the flame.

Contact: roxane.letournel@safrangroup.com

Large eddy simulation of turbulent
tandem diffusion flames under crosswind
conditions

Kazui Fukumoto1, Yuhang Chen1, Yanli Miao2, Fei Tang1,
Longhua Hu1
University of Science and Technology of China, China, 2University of
Science and Technology, China

1

The interaction between fire sources and the responseto cross airflow is one of the essential topics in the studyof multiple fire sources. Large eddy simulations (LES) were
performed for turbulent tandem diffusion flames undercrossflow to study flame-flame interaction. The computational code was an in-house version of FireFOAM, a ﬁresimulation solver within OpenFOAM. Turbulent combustion is modelled using the extended eddy dissipation concept for LES published by the authors’ group. The dynamic Smagorinsky model is used for sub-grid scale modellingin LES. The experimental data were taken by one of theauthors. The data were about propane fires from tandem
burners, varying separation distances between fires (3D5D, where D is a burner size of 15 cm) and heat release
rates (17.43-34.86 kW). First, the computational results
were validated using the measured flame width, and further investigation was carried out on the flame behaviourof the turbulent tandem diffusion flames under crossflow.
Specific flame oscillating behaviour in the spanwise direction was observed, especially for a downstream diffusion
flame, which was identical to the experiment. The flow
field heavily influenced the behaviour of the flame and thewake structures behind it.
Contact: kazuifukumoto@ustc.edu.cn

163

Track12 Fires

Large-eddy simulation of a methane
fire plume using steady and unsteady
flamelet models
Xu Wen, Yunxiao Yan

University of Science and Technology of China, China

An accurate prediction of fire dynamics is important for
the assessment of fire safety and the design of fire protection systems. It is challenging to model fire plumes dueto the complex interactions of multi-physics, including thebuoyancy-driven turbulence, chemistry, fluid dynamics,
radiation, and the transient effects of ignition and extinction. In this work, we will conduct large-eddy simulation topredict a one-meter diameter methane fire plume using
steady and unsteady flamelet models, in which the radiation and transient effects are considered. The radiation
effects are considered by solving the transport equation
for the total enthalpy with the radiation source term in theflow solver, while the temperature boundary condition for
the flamelet equations is varied to consider the radiative
heat transfer. In the unsteady flamelet model, the flamelet
solutions obtained from the unsteady flamelet equations
are parameterized as a function of mixture fraction, progress variable, scalar dissipation rate, and total enthalpy.
The turbulence-chemistry interactions are consideredwith proper presumed probability density functions. The
performance of the flamelet models in predicting the poolfire will be evaluated by comparing against the available
experimental data. In particular, the transient effects will
be analyzed in detail.
Contact: xu.wen@ustc.edu.cn

Feasibility of a simple dust-explosion
model to predict limit conditions
Supanat Vichienpattayakom1, Kazunori Kuwana1,
Shigetoshi Yazaki2, Rinrin Saeki3, Wookyung Kim3

1
Tokyo University of Science, Japan, 2Meiji University, Japan, 3Hiroshima
University, Japan

Explosions can occur wherever combustible dust ishandled, and information on limit conditions, such as theminimum explosive concentration (MEC) and the minimum ignition energy (MIE), is crucial for developing safetymeasures. Although extensive experiments have been
conducted to report these data, controlling experimental
parameters, such as particle diameter and dust concentration, is challenging, making numerical predictions attractive alternatives. This study examines the feasibility ofa simple dust-explosion model to predict limit conditions.
The model ignores the gas-phase density variation due to
combustion, as in the constant-density approximation frequently used in analyzing gaseous premixed flame prop-164



agation. This approximation, along with the assumptionof point heat sources, enables the use of fundamental
solutions, significantly reducing the computational cost.
Predicted burning velocities and the minimum explosive
concentration are compared with available experimental
data to test the model’s validity for predicting practicallyuseful information.
Contact: kuwana@rs.tus.ac.jp

Flame retardant effects on non-premixed
boundary layer flames
Raúl Felipe Corrales Flores1, Christoph Möller1, Federica
Ferraro2, Andreas Dreizler1, Arne Scholtissek1
Technical University of Darmstadt, Germany, 2Technical University of
Braunschweig, Germany

1

In fire scenarios, boundary layer flames (BLFs) can develop at flammable, "active" walls and they are fueled byvolatiles released during the thermal degradation of thewall material. In this context, flame retardants (FRs), integrated into materials like polymers, can play a vital role infire mitigation. However, their influence on BLFs dynamics
remains inadequately explored. In this work, we aim to address this gap by numerically investigating BLFs under the
influence of FRs. We first conduct a combined experimental and numerical investigation of non-premixed methane-air flames at an active wall. A novel flame configuration is employed, featuring a primary premixed flame in aside wall quenching configuration, with methane injected
through a secondary wall inlet above the flame's quenching point. The secondary diffusion flame transfers heat to
the wall resulting in a complex thermochemical state. The
latter is analyzed for different mass flows issued from thewall inlet and implications for reduced order modeling/
manifold generation are identified. Furthermore, we examine the influence of phosphorus-based FRs on the structure of the non-premixed BLF and the induced changes
to the thermochemical state. The present work provides
insights into FR-BLF interactions, contributing to the development of more effective fire safety measures.
Contact: corrales@stfs.tu-darmstadt.de

Simulation study of fire dynamics andheat transfer: the effects of wind andslope
Yong Hu, Chenyao Su

University of Science and Technology of China, China

The slope and wind speed are deemed to be the determinant factor driving the eruptive spread of wildfire, which

19th International Conference on Numerical CombustionTrack12 Fires

however has not been fully investigated. A systematic
study is therefore carried out to quantitatively characterize the fire behaviors with varying wind and slope conditions, for which the physics-based numerical simulations
are performed. The rate of spread increases with increasing both slope and wind speed, but an abrupt growthis exhibited when slopes are larger than 20 ˚ . At higher
slope, the fire line also experiences the transition from a
U-shape to a pointed V-shape, along with the appearanceof the stripe burning zones, indicating a faster spread but
incomplete combustion. Conversely, for low wind speed
and slope conditions (≤ 10˚, ≤ 1.0m/s), an interesting deformation of fire front into a W-shape is observed, which is
attributed to the combined action of lateral air entrainment and the backflow in front. It is also revealed that at
high slope conditions, the convergence of incoming windstream and the weakened indraft flow contribute significantly to the eruptive fire spread. Different mechanisms
are identified for the heat transfer ahead of fire front, i.e.,
the radiative heat is mainly affected by the enlarged volume of fire plume, and in contrast, the flame attachment
at high slope (especially for >20 ˚ ) would dominates theconvective heating for the acceleration of fire spread.
Contact: yhu18@ustc.edu.cn

Swift Flame-to-Fuel Heat Transfer
Evaluation in Simulation via Deep
Learning and Fire Images
Caiyi Xiong1, Zilong Wang2, Xinyan Huang21South China University of Technology, Guangzhou, China, 2The Hong Kong
Polytechnic University, Hong Kong

In the realm of numerical fire simulations, the intricate
calculation of thermal feedback from the flame to the solid or liquid fuel surface stands as a pivotal factor, bridging
the gap between gas-phase flame combustion and condensed-phase fuel gasification. However, within CFD firemodeling tools, this computation proves computationallydemanding due to the necessity for a high-resolution gridto compute interface heat transfer. This study introduces
a groundbreaking approach—a real-time prediction offlame-to-fuel heat transfer using computer-vision deeplearning and simulated flame images. The model is trainedusing images from various methanol pool fires, offering
insights into the shift from convective to radiative heattransfer as pool diameters increase from 20 cm to 40
cm. Results showcase the AI algorithm's ability to predictboth convective and radiative heat flux distributions on
the condensed fuel surface in real-time, leveraging flame
morphology captured by a larger grid. This innovative
method, applicable to diverse fire scenarios, goes beyond
empirical correlations to predict non-uniform heat trans-

fer coefficient distributions on the interface. The study
demonstrates the efficacy of AI and computer vision inaccelerating complex numerical fire simulations, enabling
the modeling of intricate fire behaviors with reduced computational expenses.
Contact: zilong.wang@connect.polyu.hk

Track12-2 Fires (2)Chair: Samuel L. ManzelloFriday, May 10; 13:00 - 15:00; Room I

Numerical study of pyrolysis, flaming
and smoldering of wildland fuels using
detailed kinetics coupled with a multiregion single-particle model
Mohamed M Ahmed, Chiara Saggese

Lawrence Livermore National Laboratory, United States

Wildland fires have been responsible for the destruction of vast amounts of infrastructure, thus yielding
massive damage. They are also a major global source ofgreenhouse gas emissions and aerosols, which have significant impacts on air quality and climate. In this context,
a fundamental understanding of the burning processes ofwildland fuels is crucial for the modeling and prediction ofboth fire behavior as well as related emissions. This work
leverages a novel multi-dimensional combustion kinetics
solver to investigate the pyrolysis, flaming and smoldering
combustion of biomass, considered as a common wildland
fuel surrogate. Biomass fuels are represented throughtheir fundamental constituents, such as lignin, cellulose,
hemicellulose, water, and extractives. A detailed reaction
kinetic model is adopted to reproduce the process of
their degradation, including char oxidation. Validation of
the modeling framework with experimental data from literature is performed at various scales, including thermogravimetric experiments and particle-scale experimentsof pyrolysis and combustion. The goal is to evaluate thedependency of emissions on potentially influential parameters, such as flame temperature, atmosphere conditions
and particle size. These results will then be used to construct sub-models for large-scale wildfire applications.
Contact: saggese1@llnl.gov

165

Track12 Fires

A model for fire growth and suppressionof thin melting plastics in FireFOAM
Alex Krisman

FM Global, Australia

Industrial fires may feature thermoplastics with thinconstructions and complex geometries that readily melt
and deform. This behavior is too complex to directly represent in large-scale computational fluid dynamics (CFD)
fire simulations such as those performed in FireFOAM, andso we present a simplified model that captures the leading order physics and provides a computationally tractable implementation. In this approach, we approximate theinitially solid plastic as thin, geometrically 2D surfaces.
Each face on the surface evolves a pseudo-1D conservation of mass and energy equation coupled with the gasphase CFD, Lagrangian parcels for molten plastic (due todripping/impingement) and water (due to sprinkler spray).
The pseudo-1D equations account for: convective andradiative heat transfer from the fire; melting/solidificationand gasification of the initially solid plastic; and drippingand impingement of both molten plastic and water. The
plastic surface is treated in a dynamic manner, allowing
for remeshing where plastic elements have collapsed,reflecting the real-world geometry changes that impact
various heat/mass transfer processes. The fire growthpart of the model has been validated against full-scale experiments and the suppression part is demonstrated here
for the first time.
Contact: Alex.krisman@fmglobal.com

Numerical Simulation of Flame Spreadon an Inclined Thin Paper using the Fire
Dynamics Simulator (FDS)
Shinnosuke Nishiki
Teikyo University, Japan

Understanding the complex mechanisms of fire spreadis crucial for preventing fire damages. Experiments indicate that when paper is inclined, the flame spreads downward over a specific range of slopes. This study showsthat numerical simulation using FDS (Fire Dynamics Simulator) reproduce such of experimental results. Particularly
when incline is 35 degree and gap is 3mm to the bottom
boundary, after igniting in the center of an inclined paper, the flame spread downward in a fan shape. Reaching flames the bottom edge, the top half part is burned
quickly. This situation very well reproduces what wasobserved in experiments. During the fan-shaped flame
spread, the distribution of high temperature and total heat
flux on the paper surface is concentrated near the tip on166

the descending side of the flame propagation. There issufficient heat flowing into the paper to cause thermal
decomposition, and the sufficient of oxygen supplied isalso sufficient, so combustion continues. At that time,
the upper side of an inclined paper, the inflow of heat is
insufficient and the supply of oxygen is also insufficient,resulting in slow combustion. After burning out downward,
the enough oxygen supply prompts the flame to spread
upward. Calculations for different gradient/gap conditions
between paper and ceramics have been run to confirm
that the experiment can be reproduced and to elucidate
the phenomenon.
Contact: nishiki@ics.teikyo-u.ac.jp

Numerical Investigation on the Effects ofChar Oxidation in Near-limit Flame Spreadover a Solid Fuel in Microgravity

Arvind Bharath S R1, Praveen Kumar B2, Kambam
Naresh1, Amit Kumar1

Indian Institute of Technology Madras, India, 2Seimens Technology andServices Pvt Ltd, India, India

1

Experiments have reported that the flame over a solid
fuel breaks into flamelets in a near-extinction microgravity
environment and extends the range of material flammability. However, the role of char oxidation in flamelet behaviour is little known so far. Thus, an elaborate 3D numerical model of one-step, second-order global gas-phasereaction between fuel vapour and oxygen solving mass,
species, momentum and energy conservation equations,with a simultaneous char model consisting of char formation and oxidation, first-order Arrhenius pyrolysis model insolid phase solving mass and energy conservation equations in a the flame-fixed coordinate system with thermalradiation calculated using the Discrete-ordinates method
coupled with a grey model for the radiative properties ofCarbon dioxide and Water used to investigate the effects
of Char Oxidation in near-extinction conditions. The heat
feedback from Char Oxidation is expected to assist in sustaining the flamelets and extending the range of material
flammability.
Contact: ae19d025@smail.iitm.ac.in

19th International Conference on Numerical CombustionTrack12 Fires

Track12-3 Fires (3)Chair: Shinnosuke Nishiki
Friday, May 10; 15:20 - 17:20; Room I

Role of Numerical Combustion for
Improved Understanding of WildlandUrban Interface (WUI) Fires
Samuel L. Manzello1, Sayaka Suzuki2

Tohoku University, Japan and Reax Engineering, USA, Japan, 2Tokyo
Institute of Technology, Japan1

The wildland-urban interface (WUI) fire problem iscontinuing to spread all over the world. Due to continued
changes in global climate, many areas not often associated with a WUI fire problem are now being forced to deal
with this new challenge. The fire research community
have developed computational fluid dynamic (CFD) models that have mainly been validated for fires that occur
inside buildings. The wildland fire community have developed operational models that are being used by fire management personnel to try to make global decisions on fire
spread processes. A broad overview of research-based
and operational models for WUI fires will be presented.
The talk will then move into recent experiments by ourgroup needed to model complex firebrand accumulation
processes, missing from current models. The firebrandgenerator, which has the ability to make a firebrand shower, was used to recreate firebrand accumulation processes
seen in real WUI fires. Detailed analysis was performed tounderstand the complex firebrand accumulation processes.
Contact: manzello@tohoku.ac.jp

CFD analysis of tunnel fire under rainfall
using species-transport and discrete
phase model
Dia Luan1, Jakub Bielawski2, Xinyan Huang3, Chuangang
Fan1

Central South University, China, 2Building Research Institute, Poland, 3 The
Hong Kong Polytechnic University, China
1

The study of fire in a tunnel is crucial for fire safety.
This work underscores the significance of Computational
Fluid Dynamics (CFD) techniques in addressing the interaction between fires and rainfall. The dynamics of a tunnel fire under rainfall have been simulated using FLUENT
software from ANASY Inc. Discrete phase model basedon the Lagrangian approach and the species transportmodel considering chemical reactions are applied to thesimulation of rain and fire, respectively. The computation-al domains, boundary conditions, solution strategy, andsolve setting are outlined. This work focuses on the flow
flow, temperature ﬁelds, and turbulence characteristics,
and simulation results are compared to model-scale tests.
Different turbulence models are discussed and the ability of the Reynolds-Averaged Navier-Stokes (RANS) andLarge Eddy Simulation (LES) turbulence method to predictthe unsteady flow field in unstructured grids is evaluated.
Additionally, thermocouple models play a crucial role inaddressing the prevalent issue of overpredicted temperatures in fire simulations conducted by FLUENT. This work
supports the effectiveness of CFD techniques in simulating fires and provides some recommendations for CFD
modeling of tunnel fires.
Contact: luandie@csu.edu.cn

Accelerating Tunnel Fire Simulation: A
Comprehensive Approach Integrating
CFD and Deep Learning
Yuxin Zhang, Xinyan Huang

The Hong Kong Polytechnic University, Hong Kong

This study pioneers an advanced approach to tunnel
fire simulation by integrating computational fluid dynamics (CFD) and artificial intelligence (AI) using deep learningtechniques. The simulation focuses on crucial fields forhuman behavior in fire, such as temperature, visibility, carbon monoxide (CO), and thermal radiation in tunnel fires.
The research firstly leverages the Fire Dynamics Simulator (FDS) for comprehensive scenario simulations acrossdiverse tunnel and fire conditions. Therewith, the application of deep learning for time series prediction enables
the extraction of dynamic fire development rules fromthe simulated scenarios. The resulting model facilitates
real-time forecasts of the aforementioned fields based on
specific tunnel and fire parameters. This AI-driven timeseries simulation approach offers a sophisticated tool for
emergency responders and tunnel operators, delivering
precise and adaptive insights to optimize evacuation strategies during tunnel fire incidents in real time.
The synergy of numerical simulations and AI applications using deep learning for time series forecasting
represents a cutting-edge contribution to tunnel safety
and emergency response. By harnessing the power ofpredictive analytics, this research not only advances ourunderstanding of tunnel fire dynamics but also provides apractical tool for decision-makers to enhance overall tunnel safety and evacuation preparedness.
Contact: yuxinzhang3409@gmail.com

167

Track12 Fires

AI-based fire smoke simulation forbuildings with complex geometry

Yanfu Zeng, Tianhang Zhang, Zilong Wang, Xinyan
Huang
The Hong Kong Polytechnic University, Hong Kong

Fire-smoke modelling is a common practice for building design to assess the efficiency of proposed fire protection provisions, such as fire compartmentation andsmoke extraction system. However, the current design
process based on computational fluid dynamics (CFD)
modelling is time-consuming and costly. This work aims
to achieve a real-time prediction on the fire-induced
smoke movement for buildings with complex geometries
by applying artificial intelligence (AI) technology. A numerical building fire database containing different building
geometries was first established, which was then trainedby a generative adversarial network (GAN) model to learn
the smoke movement patterns. By inputting the physicalmodel of the building, the pre-training GAN model can
output the soot visibility slices within seconds for 1MW
T-square design fire. The result shows that AI can reproduce the descending process of the smoke layer from theperspective of vertical (X or Y directions) slices across thefire location, and also provide comparable smoke filling
patterns from the view of horizontal (Z direction) slice at
2 m height above the fire. The prediction accuracies forfive testing cases are between 83% to 96% except for one
extremely innovative-designed building. This research verified the feasibility of using AI to predict smoke movement
for complex buildings, which can significantly reduce thedesign cost and enable more cost-effective solutions.

by National Institute of Standards and Technology (NIST),
specifically chosen to encapsulate diverse fire dynamics.
Subsequently, a computer vision-based deep learningmodel is employed to accurately identify and quantify the
HRR associated with different flame morphologies. The
identified HRR values serve as inputs for the FDS, enabling
the numerical simulation to emulate real fire behavior
with heightened accuracy. The efficacy of this approachis demonstrated across a spectrum of fire scenarios,
ranging from growing and decaying fires to instances of
puffing flames induced by buoyancy effects. The results
showcase the capability of the developed image-based
flame identification model to help simulate the real fire
behaviors. This innovative methodology contributes toadvancing numerical fire simulation by incorporating real-world flame characteristics, facilitating a more accurate
and efficient representation of complex fire behaviors.
Contact: zilong.wang@connect.polyu.hk

Contact: yan-fu.zeng@connect.polyu.hk

Linking Real Fires to Numerical
Simulations with Image-Based Flame
Identification
Zilong Wang1, Caiyi Xiong2, Xinyan Huang1

The Hong Kong Polytechnic University, Hong Kong, 2South China
University of Technology, Guangzhou, China, China

1

In real fire scenarios, the Heat Release Rate (HRR) is
often an unknown parameter, presenting a significant
challenge in accurately simulating and replicating fire scenarios. This study introduces a novel approach for bridging the gap between real fire scenarios and numericalsimulations through image-based flame identification. The
primary focus lies in utilizing the identified Heat Release
Rate (HRR) from flame images as a crucial input parameter for the Fire Dynamics Simulator (FDS). The proposed
methodology involves the creation of a comprehensive
image database derived from various fire tests conducted168

19th International Conference on Numerical CombustionTrack14 New combustion technologies

Track14-1 New combustion
technologies (1)Chair: Amir Mardani
Wednesday, May 8; 15:30 - 17:10; Room H

Performance Characteristics of a
Tangential Flow Burner for Ammonia
Combustion
Srinuvasarao Muddada, Reddy Mahendra Vanteru
Indian Institute of Technology Kharagpur, India

Burning ammonia has recently gained considerable attention due to its high hydrogen content and zero carbon
emissions. However, achieving a stable flame with pureammonia is a challenging issue due to its low energy content and flammability limit. From an emissions standpoint,
fuel NOx poses a significant issue with ammonia flames.
In this study, we have developed a tangential swirl-based
two-stage burner to maintain stable pure ammonia flames
while minimizing NOx emissions. The unique burner design integrates both recuperative features and effective
air staging. Experimental assessments were conductedacross various equivalence ratios (0.5–1.2), spanning athermal intensity range of 1.5–4.6 MW/m3. The factors
considered in the burner's development are wall heat-loss
effects, local mixing characteristics, and available ignitionenergy. Consequently, this novel burner achieved thelowest NOx concentration with zero ammonia emissions
compared to those reported in the literature. To delve
deeper into the burner, 3D numerical simulations using
Large Eddy Simulations (LES) were performed to examine
mixing characteristics, ammonia consumption, and NOx
production rates. The findings revealed a well-distributed
temperature profile, with the lowest NO production observed at higher thermal intensities. Notably, a specificNO level of 2.8 PPM/kW was identified at a thermal intensity of 3 MW/m3 and an equivalence ratio of 1.1.
Contact: srinu010896@gmail.com



A numerical study of ammonia cracking
in bluff-body stabilized non-premixed
flamesSuliman Abdelwahid, Mohammad Rafi Malik, Erica
Quadarella, Francisco E. Hern'andez-P'erez, Adamu
Alfazazi, Bassam Dally, Hong G. Im
King Abdullah University of Science and Technology, Saudi Arabia

This study explores a novel in-situ ammonia decomposition approach in the recirculation zone of a newly
designed bluff-body burner at KAUST. The application ofthis method improves flame stability and minimizes emissions. To gain improved fundamental insights, numericalsimulations with Reynolds-Averaged Navier-Stokes (RANS)
and Large Eddy Simulation (LES) reduced-order models,
relying on parameterizations of the thermochemical state
space, were employed, and their predictions are contrasted against recent measurements obtained at KAUST.
Additionally, a potential enhancement of the modelingapproach can be achieved by incorporating finite-ratechemistry (FRC) models. A key discovery of this study is
the identification of two distinct zones within the burner:a lower luminous region characterized by intense burningand an upper flameless region exhibiting vitiated combustion, effectively consuming NO. Such findings highlightthe potential of this approach as a promising avenue for
mitigating environmental impact while enhancing ammonia flame stability.
Contact: suliman.abdelwahid@kaust.edu.sa

Low-order modeling of ammonia
combustion in porous media burners

Thorsten Zirwes1, Guillaume Vignat2, Emeric Boigné2,
Matthias Ihme2
1

University of Stuttgart, Germany, 2Stanford University, United States

Ammonia is becoming an important carbon-free fueldue to its production from renewably generated hydrogen and ease of storage. However, ammonia flames arecharacterized by low flame speeds and high ignition delay times, making it challenging to stabilize flames withhigh power density. One promising approach are porous
media burners (PMBs). In this configuration, the flame
burns within connected pores of ceramic foams. Heat169

Track14 New combustion technologies

recirculation from the solid phase stabilizes the reaction
zone and enables high power density combustion even ofpure ammonia flames. While this has been successfully
demonstrated experimentally, the numerical simulation of
PMBs using low-order one-dimensional models still posesa challenge due to the complex multi-physics given by theinteraction of the gas and solid phase. This includes heat
conduction in the solid, radiation, heat transfer between
the phases and modification of diffusive fluxes by the tortuosity. In this work, we present a 1D open-source solver(https://github.com/IhmeGroup/PMCToolbox) based on
Cantera and extended for PMBs. The code is validated byconsidering the experimentally studied ammonia PMB.
Using effective properties from μCT-scans of the solid
structure, good agreement between simulation and measurement was found in terms of pollutant emissions andflame stabilization characteristics.
Contact: thorsten.zirwes@itv.uni-stuttgart.de

New concept for aerodynamic
stabilization of lifted hydrogen diffusion
flamesJakub Tumidajski, Adam Klimanek
Silesian University of Technology, Poland

Hydrogen oxy-combustion offers a solution with water
vapor as the sole combustion product, addressing emissions concerns. Challenges arise from the high temperature (3600 K) of hydrogen flame in pure oxygen, exceeding commonly used material thermal resistance. This hightemperature gives rise to two problems: contact between
the flame and the burner tip, and contact between theflue gas and the combustion chamber walls. Lifting theflame and introducing cold air mitigate these, but traditional burners risk flame instability, especially with varying
burner power.
To overcome these challenges, a specialized burner is
proposed. Configured for separate reagent delivery, angled oxygen injection forms a barrier, reducing fuel velocity for aerodynamic flame stabilization away from burner
walls. Simultaneously, steam introduction between fueland oxygen inlets ensures targeted intersection for optimal flame occurrence. The elevated temperature of steam
facilitates spontaneous ignition and serves as a diluent for
temperature control.
The study focuses on investigating hydrogen combustion in lifted diffusion flames under diluted conditions forgas turbine applications. Numerical simulations explore
flame stability, considering parameters like dilution ratio,
equivalence ratio, diluting gas inlet temperature, burnergeometry, and dilution agent. Adjusting these parameters
enables control over temperature, flame lift-off height,170



and achieving complete combustion, minimizing unburned
fuel at the combustion chamber outlet. The objective isto provide insights into combustion physics, guiding thedesign and operation of the hydrogen burner for a mixed
gas/steam turbine cycle, aiming at emission reduction andefficiency improvement.
This research was financially supported by the National Science Centre under OPUS research programme,
grant No. 2020/39/B/ST8/02494. The support is herewith
gratefully acknowledged.
Contact: jakub.tumidajski@polsl.pl

Combustion and emission characteristics
of a premixed NH3/O2 jet flame in hot
coflow of N2 versus H2O
Xiangtao Liu1, Guochang Wang2, Jianchun Mi1
1

Peking University, China, 2Taiyuan University of Technology, China

Ammonia is a promising alternative carbon-free fuel,but its conventional combustion is unstable and emits lotsof NOx. Moderate or intense low-oxygen dilution (MILD)
combustion features high stability and ultra-low NOx
emissions, and the addition of H2O can further reduceNOx formation. The present work numerically investigates
the effect of N2/H2O dilution on a premixed NH3/O2 jetflame in hot coflow under MILD condition. Specifically, thetemperature, thermal efficiency, species concentrations,and NOx emissions are analyzed over a wide range ofequivalence ratios (φJ). Moreover, fictitious diluents, FN2
and FH2O, are introduced to quantify the physical andchemical effects. The results indicate that the chemical
effect of N2 dilution is negligible regardless of φJ. As for
H2O dilution, both physical and chemical effects enlarge
the volume of the high-temperature region and reduce
the temperature peak. In addition, the chemical effectof H2O dilution significantly increases the emissionsof unburned NH3, H2, and OH, resulting in a reductionin thermal efficiency by up to 17%. At φJ ≤ 1.0, replacing
N2 with H2O as the diluent reduces the NO emission,
but the effect is opposite at φJ > 1.0. Notably, the HNO
pathway emerges as the most important NO production
pathway, being suppressed by H2O dilution at φJ ≤ 1.0 andenhanced at φJ > 1.0. Additionally, the DeNOx pathway
dominates the NO consumption and is enhanced by H2O
dilution.
Contact: liuxtcoe@stu.pku.edu.cn

19th International Conference on Numerical CombustionTrack14 New combustion technologies

Track14-2 New combustion
technologies (2)Chair: Abhishek Lakshman Pillai
Thursday, May 9; 09:50 - 12:30; Room B

Efficiency analysis of ignition by
Nanosecond Repetitively Pulsed
discharges using a low-order approach
Stéphane Q. E. Wang1, Yacine Bechane2, Nasser
Darabiha1, Benoît Fiorina1
1

Direct numerical simulation ofnanosecond repetitively pulsed
discharges for plasma-assisted flamestabilisation in flowing environments
Daniel Fredrich, Stewart Cant

University of Cambridge, United Kingdom

The plasma-assisted ignition and stabilisation of premixed methane-air flames in moderate to high-velocity
bulk flows is investigated using direct numerical simulation. The approach accounts for the primary thermal andkinetic effects of non-equilibrium plasmas sustained bynanosecond repetitively pulsed discharges. The numerical framework is firstly validated against several experimental and numerical test cases from the literature. It isthen applied to study the spatiotemporal evolution of theflame kernel ignition and growth in a flowing methane-air
mixture with an equivalence ratio of 0.9. For this purpose,a parametric study is performed based on a custom test
case at ambient conditions using discrete discharge energies of 2.8 and 3.2 mJ per pulse, pulse repetition frequencies in the range of 20 to 50 kHz, and bulk flow velocities
between 0 and 100 m/s. It is shown that the inter-pulse
coupling, governed by the relationship between the bulk
flow velocity and the pulse repetition frequency, plays acrucial role in the mixture ignition process. Moreover, fora given discharge energy per pulse, a critical discharge
kernel convection distance can be determined to distinguish between three different operating regimes: (i) no
ignition, (ii) unstable operation, characterised by an oscillating behaviour with periodic flame kernel extinction
and re-ignition, and (iii) a stabilised flame. Simulations inthree-dimensional space are performed to support thefindings and further analyse the dynamics and interactionof consecutive discharge kernels. Finally, the possibility ofextending the flame stabilisation limit by means of mixture preheating is demonstrated.
Contact: df436@cam.ac.uk

Université Paris-Saclay, CNRS, CentraleSupélec, Laboratoire EM2C, France,
Normandie Univ, UNIROUEN, INSA Rouen, CNRS, CORIA, France2

Plasma-assisted combustion is an interesting method
to promote the ignition of a lean reactive mixture insteadof conventional spark plugs. Especially, Nanosecond Repetitively Pulsed (NRP) discharges are an energy-efficient
way to initiate and control combustion processes. Recent
experimental and numerical studies have shown that
ignition success or failure results from the competition
between the discharge energy accumulation, the gas
residence time in the discharge region, and the combustion chemistry. In this work, plasma-assisted ignition ismodeled and analyzed by considering a perfectly-stirred
reactor whose volume represents the one surrounding
the interelectrode region. NRP discharges are applied
inside the reactor using a phenomenological model toinitiate the combustion of the injected fresh mixture. The
approach allows to numerically identify, at a low CPU
cost, a plasma-assisted ignition efficiency map in terms of
the amount of energy per pulse and the pulse repetition
frequency. Moreover, a criterion based on the residencetime, inter-pulse time, and chemical time is introduced to
predict the successful formation of a reactive kernel.
Contact: stephane.wang@centralesupelec.fr

Modeling of turbulent flame
enhancement by Nanosecond Repetitively
Pulsed discharges using a low-orderapproach
Stéphane Q. E. Wang, Nasser Darabiha, Benoît Fiorina

Université Paris-Saclay, CNRS, CentraleSupélec, Laboratoire EM2C, France

Plasma-assisted combustion (PAC) is a promising
method to stabilize turbulent premixed flames in leanregimes, which are prone to instabilities and extinction.
Among the plasma technologies, Nanosecond Repetitively Pulsed (NRP) discharges are an energy-efficient way toenhance and control combustion processes. Recent numerical analyses of a lean bluff-body turbulent premixed
methane-air flame have shown that the heat and theradical O produced by NRP discharges mainly induce OH,
H$_2$, and O$_2$ through the dissociation of burnt gases. Because of their long lifespans and thanks to the bluffbody recirculating zone, they are advected to the flame
front where they are consumed, increasing the chemical

171

Track14 New combustion technologies

reactivity. Subsequently, the local increase in heat release
rate anchors the turbulent flame front, allowing it to develop further downstream and leading to a rise in the total
flame surface and power. In this work, PAC is modeledby considering two perfectly-stirred reactors (PSR) and acounterflow premixed flame. Respectively, they represent
the interelectrode region, recirculating zone, and flame
front. The first PSR employs a phenomenological NRP discharge model, and the second one a temporally evolving
inlet. The approach reproduces the mechanisms of turbulent premixed flame stabilization by NRP discharges at a
low CPU cost.
Contact: stephane.wang@centralesupelec.fr

Effect of micro-mixing on nanoparticle
production in flame-synthesis: a priori
validation of subgrid models for the
Batchelor scale

Yuri Ogata1, Aymeric Vié1, Jean Michel Dupays1, Rodney
O Fox2, Abouelmagd Abdelsamie3, Dominique Thévénin4,
Benedetta Franzelli1

EM2C Laboratory, Université Paris-Saclay, CNRS, CentraleSupélec, France,
Department of Chemical and Biological Engineering, Iowa State University,
United States, 3Lab. of Fluid Dynamics and Technical Flows, University of
Magdeburg “Otto von Guericke” , Germany, 4Lab. of Fluid Dynamics andTechnical Flows, University of Magdeburg “Otto von Guericke”, Germany
1

2

The optimization of nanoparticle flame synthesis to
produce high-quality materials requires a deep understanding of multi-scale interactions between turbulence,
flame, and particles. Direct Numerical Simulations (DNS)
are classically performed to understand the strong coupling between turbulence, combustion, and aerosol processes. However, the low diffusivity of particles leads to acharacteristic Batchelor scale potentially smaller than the
Kolmogorov scale. In this context, the aim of this work is:1) The characterization of micro-mixing effects on particle
size and morphology.
2) T he a priori evaluation of subgrid models to accountfor the aerosol processes at the Batchelor scales whenusing classical DNS grids, where the Kolmogorov scaleis resolved but not the Batchelor nanoparticle scale.
A two-mesh strategy was developed: the gas phase isresolved at the Kolmogorov scale, while the particle phaseis solved on a finer mesh resolved at the Batchelor scale.
An H2/air non-premixed flame interacting with a vortex
will be simulated using a monodisperse three-equations
model. Different initial conditions for the solid phase andmodel parameters will be considered to provide insights
into the role of micro-mixing on nanoparticle prediction
and the capacity of subgrid models to account for them.
Contact: yuri.ogata@centralesupelec.fr

172

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Chemical Evaluation of a Gas Turbine
Model Combustor under Diluted andPreheated Conditions Using LES

Amir Mardani1, Amir Agha Beige1, Kyung Chun Kim2

Sharif University of Technology, Iran, Islamic Republic of, 2Pusan National
University, Korea

1

Large eddy simulation of a Gas Turbine Model Combustor (GTMC) is performed under both normal and diluted/preheated conditions considering a detailed reduced
chemical mechanism through the eddy dissipation concept (EDC) volumetric combustion model. To deliver thesame outlet conditions, about 36% reduction in fuel flowrate in addition to 32% dilution of the incoming air (EGR)
and an air preheat to 730 K are used in the diluted/preheated case. The accuracy of the present simulations is
assessed by comparing the results to the available experimental data. To investigate premixedness, flame indicesbased on CH4 and CO are evaluated, which shows thatfar from the inlet nozzle, the CH4 reactions are sustained
mostly in premixed mode, while the CO reactions mostly
stay in non-premixed mode. Moreover, it is shown that dilution/preheat can lead to higher concentrations of combustion radicals and slow reaction zones at the end of thereactant jet. Finally, slow elementary reactions are shownto have lower sensitivity to the strain rate in the diluted/
preheated case, while dropping in high strain regions forthe normal operation case, which plays an important rolein determining the locations of Formaldehyde formationand heat release.
Contact: Amardani@sharif.edu

Plasma-assisted MILD combustion:
Induced velocity effects

Mohammad Sadegh Talebi1, Amir Mardani1, Kyung Chun
Kim2

Sharif University of Technology, Iran, Islamic Republic of, 2Pusan National
University, Korea

1

Plasma-assisted combustion has been of great interest in the past years to improve the combustion processagainst the drawbacks in terms of engine performance,
flame stability, fuel consumption, and hydrocarbon pollutants. In recent years, the effect of non-equilibrium plasma has been studied experimentally to understand the
dynamic and chemical effects. New observations such asvery dilute combustion, cold flames, flameless combustion, and plasma discharge control have been reported.
In the works carried out, laboratory tools have often beenused to create plasma discharge in the combustion environment and check the mentioned effects. Along withexperimental activities, numerical works using different

19th International Conference on Numerical CombustionTrack14 New combustion technologies

software in one and two dimensions have been of interest.
In these numerical works mostly, the dynamic and thermal effects of plasma are applied as specific parametersin the form of initial and default boundary values. In thepresent work, unlike the aforementioned works, insteadof prejudging the effects of plasma, the dynamic effectsof plasma have been modeled using the Suzen-Huang
model in a mild combustion environment, and the results
have been compared and analyzed with the existing experimental results. It can be seen that the Suzen-Huang
model can simulate the dynamic effects of plasma in the
combustion environment.
Contact: Amardani@sharif.edu

Unveiling the Impact of Magnetic Fields
on Jet Diffusion Flame Flickering

Hetong Gao, Yueming Wang, Minmin Zhou, Lunbo DuanSoutheast University, China

Gradient magnetic fields have been proven to be aneffective approach to modify stability of flames. Observations under a negative gradient field revealed low-frequency oscillations, similar to gravity-induced effects,
attributable to Kelvin-Helmholtz instability vortices. The
variation of frequency and amplitude has been concluded
from experimental observation, but the fluid dynamics behind vortex generation and motion lack detail. This study
presents three-dimensional numerical results detailing the
temporal and spatial evolution of transitional jet diffusion
flame vortices, validated against experimental data. Computational experiments were performed to investigate
the effects of initial momentum, volumetric expansion,buoyancy, and gradient magnetic force on the coherence of the vortex structures. Enhanced magnetic fields
reduce vortex length, increase generating and shedding
frequency, and shift vortex generation position upstream.
In this situation, vortices more easily pinch off the flame,
and under a strong magnetic field, they may even directly
cause blow-out. Due to the relatively low Reynolds number, there are no shear flow vortices generated within the
flame surface, minimizing the impact of initial momentum
and volumetric expansion. Buoyancy and magnetic forcessynergistically influence vortex dynamics, with the role ofbuoyancy diminishing under stronger magnetic fields. This
research elucidates magnetic field-induced flame oscillations and aids in understanding gravity-driven outer vortices, contributing to the in-depth study of flame stability.

Reaction analysis of frequency
dependence on ignition delay time of
CH4/Air mixture by repetitive supply ofactive species
Akira Shioyoke, Jun Hayashi, Hiroshi Kawanabe
Kyoto University, Japan

Numerical analysis was conducted to simulate nanosecond pulsed repetitively discharge which is attracting
attention as a method for stable flame kernel formation inlean combustion. The effect of pulse repetition frequency
on the ignition delay time of CH4/air mixture was investigated using reaction analysis. In this report, methane,the lightest hydrocarbon fuel, was focused and comparedwith higher hydrocarbons, which can be ignited throughLow-Temperature Chemistry (LTC) and H2O2 loops. The
nanosecond pulsed discharge was considered as the rapid decomposition of initial chemical species. Zero-dimensional reaction calculations simulating the ignition process
through the repeated supply of active chemical species
were performed using perfectly stirred reactor model
SENKIN. The analysis results, consistent with experimental
findings, demonstrated that the ignition delay time is minimized at a specific frequency, indicating the presence ofcharacteristic times in chemical reactions. The difference
in reaction pathways between the ignition process driven
by the addition of active chemical species and thermal ignition is discussed. Based on the reaction pathway which
input active chemical species are consumed, important
species and reactions influencing the characteristic timeof chemical reactions are discussed. Furthermore, the effect of discharge pulse numbers and input energy on theignition process is examined.
Contact: s.akira2986@gmail.com

Contact: yueming@seu.edu.cn

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Track15 Numerical methods for reacting flows

Track15-1 Numerical methods
for reacting flows (1)Chair: TBD
Wednesday, May 8; 10:40 - 12:20; Room F

Effect of the two-phase flow on the throat
erosion feature of the C/C composite
nozzleZheng Yang, Junwei Li, Wenhao Zhang, Xiang Li, Ningfei
Wang
Beijing Institute of Technology, China

Quantum computing of reacting flows via
Hamiltonian simulation
Zhen Lu, Yue Yang
Peking University, China

We report the quantum computing of reacting flows by
simulating the Hamiltonian dynamics. The scalar transport
equation for reacting flows is transformed into a Hamiltonian system, mapping the dissipative and non-Hermitian
problem in physical space to a Hermitian one in a higher-dimensional space. Using this approach, we develop
the quantum spectral and finite difference methods for
simulating reacting flows in periodic and general conditions, respectively. The present quantum computing algorithms offer a “one-shot” solution for a given time without
temporal discretization, avoiding iterative quantum state
preparation and measurement. We compare computational complexities of the quantum and classical algorithms.
The quantum spectral method exhibits exponential acceleration relative to its classical counterpart, and thequantum finite difference method can achieve exponential
speedup in high-dimensional problems. The quantum algorithms are validated on quantum computing simulatorswith the Qiskit package. The validation cases cover oneand two-dimensional reacting flows with a linear source
term and periodic or inlet-outlet boundary conditions. The
results obtained from the quantum spectral and finite difference methods agree with analytical and classical simulation results. They accurately capture the convection,diffusion, and reaction processes. This demonstrates thepotential of quantum computing as an efficient tool forthe simulation of reactive flows in combustion.
Contact: zhen.lu@pku.edu.cn

For the solid rocket motor C/C composite nozzle, a
two-phase flow calculation model was developed to simulate the erosion process, obtain the rate of change of theerosion rate, and analyze the change of the flow field in
the erosion regime. Calculation results show that the nozzle convergence section and the throat are affected byparticle erosion and thermochemical ablation, while thenozzle divergent section is only affected by thermochemical ablation, the average thermochemical ablation rate of
the nozzle throat is 0.0420mm/s, and the ablation of thethroat leads to the reduction of the gas flow rate, which
decreases the performance of the engine. Finally, thesimulation calculations were validated by erosion tests,
which yielded an average thermochemical ablation rateof 0.0432 mm/s for the throat measured in the test data
and an error of 2.8 percent for the simulation calculations,indicating a good agreement between the two.
Contact: yangzh3211@163.com

Simulation methodology for cryogenic
liquid hydrogen leakage, dispersion
prediction and risk assessment

Leons Antony Lawrence, Sourabh Shrivastava, Vivek
Kumar, Pravin Nakod
Ansys Software Private Ltd, India

As the world is shifting to Hydrogen based energy solutions, there is an increasing need to develop safe modesof storage and transportation of Hydrogen. Currently
Hydrogen is stored and transported in cryogenic liquidstate due to the high energy density that it offers. There isa pressing need to understand the behavior of such systems in case of an accidental leak. In this work we would
like to present a simulation methodology to predict cryogenic hydrogen leakage, dispersion into the atmosphereand the flammability risk associated with it.
A high fidelity and a low fidelity method is proposed.

Track15 Numerical methods for reacting flows• High fidelity model involves detailed two-phase modeling with real gas properties of Hydrogen, expansionof the supersonic jet, and the corresponding phasechange that happens when cryogenic hydrogen mixes with air.
• L ow fidelity model : A notional nozzle based approach was evaluated. It is based on partially expanded single phase gaseous hydrogen, with real gas
properties. It is very quick and easy model to evaluate different design concepts.
The concentration of hydrogen along the jet axis wasevaluated for both the methods and compared with published test data.
Contact: leons.lawrence@ansys.com

A large scale H2-CH4 industrial furnace
Lattice-Boltzmann study taking into
account Radiation Heat Transfer

Jose Luis Andres1, Song Zhao1, Jean Louis Consalvi2, Diego
Calanni3, Patrick Muscat3, Fouad Said3, Pierre Boivin1
1

Laboratoire de Mécanique, Modélisation & Procédés Propres, France,
Laboratoire IUSTI, France, 3Fives Pillard, France

2

Recent developments on Lattice Boltzmann Method(LBM) have established this approach as an alternative
to traditional CFD methods for combustion applications.
However, application to industrial burners remains challenging due to the large range of scales involved, and thegeometry complexity. In this study, we present large-eddy
simulations of a partially premixed H2-CH4-air industrial
burner using a hybrid Lattice-Boltzmann method. Dueto the considerable length of the 6-meters furnace andthe burnt gases content, radiative heat transfer is here
fundamental, and taken into account for the first time inthis framework. To couple Lattice-Boltzmann modellingof reacting flows and radiative heat transfer, the sphericalharmonics method of first order is adopted (P1 approximation). This method transforms the radiative transfer
equation into a set of coupled partial differential equations (PDEs). The Weighted-Sum-of-Gray-Gases approach(WSSG) is used to represent the spectral dependence ofradiative properties. The primary objective of this work
is to study the influence of the H2-CH4 fuel blend composition on the burner characteristics, ranging from puremethane to pure H2. Through our numerical simulations,
we examine the fuel composition impact on flame behaviour, temperature distribution, and pollutant formation.
To validate our simulations, the numerical results will becompared with experimental data.

Track15-2 Numerical methods
for reacting flows (2)Chair: TBD
Wednesday, May 8; 13:30 - 15:10; Room F

Effect of Two-Strut Parallel-Fuel Injection
Scheme on Mode Transition in Scramjet
Combustor
Rajesh Kumar1, Amardip Ghosh1, Suryansh Tiwari2

1
iit Kharagpur, India, 2Department of Aerospace Engineering, Thapar
University, Patiala -147004, India

Mode transition in a two-strut dual-mode Scramjet
combustor is tested numerically. Results are comparedwith mode transitions in a single-strut, dual-mode Scramjet combustor based on the German DLR configuration.
The two-strut configuration allows the manipulation of
two important flow parameters responsible for modetransition. Firstly, it allows fine-tuning the location of the
primary heat release zone between the two struts. Secondly, it allows manipulating the cross-sectional area ofthe supersonic air stream in the vicinity of this primaryheat release zone. Since the tendency of a supersonicair stream to choke thermally is influenced by both heat
addition and cross-sectional area variation, the dual-strut
configuration might provide a way to delay mode transition in a dual-mode scramjet combustor.
Numerical simulations using the commercially available ANSYS-FLUENT software running on an HPC platform
are used to simulate the influence of a dual-strut configuration on heat release and flow cross-section variation.
Two-dimensional, steady-state, k-ω, density-based implicit
solver is used to solve the partial differential equations of
fluid flow.
Results suggest that both the cross-sectional area ofthe outer supersonic flow fields and the location of heat
addition to it can be altered by altering their position andsize and orientation of the two struts, a behaviour which
will be investigated in detail in this study. Effect of suchvariations on the propensity of supersonic combustors toundergo Sudden mode transitions will be reported.
Contact: suryansh287@gmail.com

Contact: jandres723@gmail.com

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Track15 Numerical methods for reacting flows

Mesoscale modeling on the melt layer ofmetalized propellants with surface stressevolution
Hong-Suk Choi, Jack Yoh
Seoul National University, Korea

While progress has been made in the modeling ofburning surface of solid propellants, the intricate interactions within the melt layer involving three distinct phases
and multi-materials remain unresolved and present aformidable challenge. This study aims to present a comprehensive analysis on the combustion characteristics ofmetal-added propellants that considers reactive metal
particles of random size. Three pivotal techniques aredeveloped for 1) tracking the dynamics of two-phaseinterface with deforming material boundaries between
reactive particle and binder, 2) incorporating the full stressfield evolution within each particle, and 3) introducing thephase and composition identifiers to monitor the processof reaction via oxide cap formation, heat transfer between
multi-materials, and agglomeration of metal oxide. The
results on the pressure, temperature, stress, and material phase reveal the emergence and expansion of themelt layer, which includes isolated solid reactants with amulti-phase oxide cap and vaporized binder separated
from the unburnt region. The quantitative weight fraction
analysis provides insights on the three distinct sections,demarcated by predominant shifts in the material phases.
The simulation successfully replicates the visual images
taken from the experiments without the need for introducing phenomenological models.
Contact: jjyoh@snu.ac.kr

Simulations of hydrogen-air detonations
using DSMC
Shrey Trivedi1, Jorge Salinas1, John Harvey2, Alexei
Poludnenko3, Jacqueline H. Chen1

Sandia National Laboratories, Livermore, United States, 2University ofCambridge, United Kingdom, 3University of Connecticut, United States

1

Molecular level simulations of one-dimensional (1-D)
hydrogen-air detonations are performed using the Direct
Simulation Monte Carlo (DSMC) method. DSMC emulates
the motion of real molecules and can solve moleculartransport processes, internal energy relaxation, and chemical reactions directly through molecular collisions. It isa robust tool for fundamental studies of reacting flows
under thermal and chemical non-equilibrium. Hydrogen
flames have been successfully simulated with DSMC
by using both the TCE model, with uses the traditional
Arrhenius based reaction rates, and a QK model, whichmakes direct use of collision data for computing reaction176

probabilities. In this analysis, TCE model is employed for
simulating 1D detonations. Two cases of stoichiometrichydrogen-air mixtures are considered. A preheated caseat an initial temperature equal to 900 K and an initialpressure of 0.3 atm is simulated first. This is followed by asecond case at standard 300 K and 1 atm. The results arecompared with the Zel'dovich-von Neumann-Döring (ZND)
solution obtained from the Shock and Detonation toolbox.
The preheated case results in a robust and steadydetonation structure. The DSMC results for temperature,pressure, flow velocity, density and species mass fractions
for this case show excellent agreement with the ZND
solution. The case at standard conditions results in afluctuating induction zone, and DSMC captures these fluctuations effectively but the 1-D profiles differ slightly fromthe ZND solution. These differences are attributed to theshortcomings in the recombination reaction rate modelling which have received little attention in DSMC. Robust
simulations under non-equilibrium conditions will requireab-initio molecular data from Quasi-classical trajectory
calculations to provide collision cross-sections for relaxation and reaction rates.
Contact: strived@sandia.gov

Fast geometric integration for chemistry
Lorenzo Angelilli, Venkat Raman
University of Michigan, United States

Fast integration of stiff chemical source terms is a critical requirement for improving the computational efficiency of reacting flow solvers. Geometric integrators basedon Lie group methods are a robust solution to maintainthe structural attributes of differential equations, including conservation laws and symmetries. This results insimulations that are both more stable and accurate. The
approach casts the chemical source term in a generalize
Hamiltonian form, which exposes the symplectic natureof the tangent bundle. The evolution of the system is split
into two components, namely elongation and rotation,
which allows Strang-type splitting to be used. The elongation tensor is efficiently integrated using a second-order
Runge-Kutta scheme and the rotation tensor, satisfying
the Special Orthogonal Lie group properties, is integratedusing a second-order Munthe-Kaas-Runge-Kutta scheme.
This technique allows for significantly larger time steps
than explicit schemes, while maintaining the accuracy of
implicit schemes.Performance evaluations across hydrogen/air, ammonia/air, and RP2/air mixtures demonstrated
a speedup of 5-25 compared to traditional stiff integration
schemes, highlighting the efficiency and performance ofthe new approach.

19th International Conference on Numerical CombustionTrack15 Numerical methods for reacting flows

Contact: langelil@umich.edu

Track15-3 Numerical methods
for reacting flows (3)Chair: Raja Banerjee
Wednesday, May 8; 15:30 - 17:10; Room F

Comparative study to asses combustion
models for pure hydrogen bluff bodystabilized flame
Shruti Chavan1, Sourabh Shrivastava2, Pravin Nakod2
1

Cummins College of Engineering For Women, India, Ansys, India
2

Carbon-based fuels pose a significant environmental
threat as their combustion releases substantial amountsof carbon dioxide and other pollutants. This contributes
to global warming, extreme weather events, ocean acidification, and air quality degradation. The continued reliance on these fuels exacerbates the climate crisis, with
far-reaching consequences for ecosystems and humanwell-being. Due to its clean combustion characteristics,
hydrogen fuel and hydrogen-blended fuels are gaining
attention as substitutes for carbon-based fuels.
Designing new combustion systems for industrial applications with high hydrogen content requires a detailed
understanding of flame characteristics. This can be derived by studying flame from simplified concept-level configurations with well-defined boundary conditions and utilizing that information as a base to design more complex
systems. Computational Fluid Dynamics (CFD) simulations
provide detailed insights into the combustion process andcan help integrate and test the information derived fromconcept-level designs to final designs. For conventionalhydrocarbon-based combustion systems, the simulation
methodologies are well established. However, CFD methodologies for hydrogen and hydrogen blended fuels arestill being evaluated and developed by different researchgroups.
To identify the limitations of standard combustion
models and the correct simulation strategy for pure hydrogen bluff body stabilized flame, a series of simulation
studies were performed, and conclusions are reported inthis paper. Models considered for this study are the detailed chemistry finite rate model (FR), Flamelet Generated
Manifold Model (FGM), and Thickened Flame Model (TFM),
along with the combinations of Reynolds Average Navier
Stokes Model (RANS) and Large Eddy Simulation (LES)
turbulence models.
The experimental data used for reference are takenfrom NTNU’s dataset for the turbulent bluff body stabilized flame produced by a lean, fully premixed air/hy-drogen. Bluff body stabilized flames are one of the moststudied configurations due to their similarities with many
combustion systems, enabling detailed study of turbulence-chemistry interactions. The geometry consists ofthe plenum from where the premix enters and expands
for flow conditioning, the injector where the mixture iscompressed, and a conical bluff body at the end of theinjector pipe to generate a recirculation zone where theflame can stabilize in the shear layers.
Contact: sourabh.shrivastava@ansys.com

Scale similarity models for filteredreaction rates
Thommie Nilsson
Lund University, Sweden

One of the long-standing challenges in large eddy simulation of reacting flow is the modelling of the unclosed
chemical reaction rate terms. Here, we explore scale
similarity models (SSM) using some new formulations andgeneralizations. In the few prior studies of SSM for reaction rates found in the literature, the rate is decomposed
into the perfectly stirred reactor (PSR) rate plus a residual
to be determined by scale similarity. Here, we also explore
the alternative decomposition into the PSR rate multipliedby one or more correction factors that are determinedby one or more applications of scale similarity. The accuracy of different formulations are compared for laminarand turbulent premixed flames and laminar counterflow
flames. Sensitivity to fuel is also investigated by comparing methane, ethene, methanol and hydrogen. Results
show that both formulations (added residual or scaling
factor) are viable and can perform better than PSR, andmultiple levels of SSM can improve the results. Scale similarity appears to be most suitable for fine grids. No clear
dependence on fuel or combustion mode was found. Mostof the error in the modelled rates pertain to very few reactions whose reactants are artificially brought together by
the filter operator.
Contact: thommie.nilsson@energy.lth.se

A reduced order numerical model forhigh-pressure hydrogen leak self-ignition
Marc Le Boursicaud1, Song Zhao1, Jean-Louis Consalvi2,
Pierre Boivin1

M2P2 (Aix Marseille Université, CNRS, Centrale Marseille), France, 2IUSTI(Aix Marseille Université, CNRS), France

1

The numerical study of ignition risk in the case ofhigh-pressure hydrogen leakage contains numerous

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Track15 Numerical methods for reacting flows

challenges. The first is to properly resolve the complex
multi-dimensional flow (hemi-spherically expanding shock
and contact discontinuity). The second is to properly resolve the diffusion/reaction interface, which has a verysmall length scale compared to the jet radius [1].
We propose a low-order numerical model for suchflows by first decoupling the flow and the diffusion/
reaction interface into one cold flow and one reaction
interface problem. The flow simulation can be further simplified by assuming the flow in the ambient air is almost
axisymmetrical (for a two-dimensional test case) or spherical, which means that the flow only needs one spacedimension to be solved. Meanwhile, the diffusion interface
is solved with a different space variable to optimize themesh and use the flow results as boundary conditions.
The interface problem is further simplified by using thepassive scalar approach recently developed for hydrogen
ignition prediction [2].
Both the flow and the interface solver are validatedwith simple test cases and full configuration results arecompared to complete multidimensional simulations.
[1] : A.E. Smygalina, A.D. Kiverin, Self-ignition of hydrogenjet due to interaction with obstacle in the obstructed
space. Int. J. Hydrog. Energy, 47 (2022).
[2] : M . Le Boursicaud et al, An improved passive scalarmodel for hydrogen hazardous ignition prediction,
Combust. Flame, 256 (2023).
Contact: marc.le-boursicaud@univ-amu.fr

A MODAL DECOMPOSITION-BASEDPARTIALLY STIRRED REACTOR MODEL
FOR TURBULENT COMBUSTION
CLOSURE: AN A POSTERIORY STUDY

Arthur Péquin , Erica Quadarella , Riccardo Malpica
Galassi3, Salvatore Iavarone1, Hong G. Im2, Alessandro
Parente1
1

2

Université Libre de Bruxelles, Belgium, 2King Abdullah University of
Science and Technology (KAUST), Saudi Arabia, 3Sapienza University,
Rome, Italy

1

Accurately characterizing reactive environments in
combustion is crucial for optimizing efficiency and managing emissions. Turbulent conditions in practical combustion systems necessitate a trade-off between computational cost and accuracy, often addressed through Large
Eddy Simulations or Reynolds Averaged Navier-Stokes.
Closures for the unresolved reaction source terms involve
reducing the scalar transport equations to representative
variables or direct solving for all chemical species andphysical models.
The Partially Stirred Reactor (PaSR) model divides

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computational cells into reactive and non-reactive parts,
showing promise in various combustion regimes. However, accurately estimating characteristic timescales remainsa challenge due to their variability within reactive environments. The uniqueness of the cell reacting fraction has
also been found to be sub-optimal [1].
Quadarella et al. [2] proposed a modal decomposition-based PaSR model (mPaSR) by means of the computational singular perturbation theory, which relates characteristic time scales for chemistry with the eigenvaluesof the Jacobian matrix of the chemical source terms [3].
Although strongly deviating from the original PaSR formulation, abandoning the fine structures concept, a priori results demonstrated the benefits of accounting for multiple
reacting fractions. This work presents an a posteriori investigation of the mPaSR model via unsteady simulationsof flames exhibiting processes with distinctive time scales.
[1] Péquin, A., et al., Physics of Fluids, 2022.
[2] Q uadarella, E., et al., Proceedings of the Combustion
Institute, 2022.
[3] Malpica Galassi, R., et al., Combustion and Flame, 2018.
Contact: arthur.pequin@ulb.be

Track15-4 Numerical methods
for reacting flows (4)Chair: TBD
Friday, May 10; 09:50 - 11:50; Room F

Dual-scale flamelet tabulation using themulti-gate mixture of experts

Xinzhou Tang, Yicun Wang, Jiangkuan Xing, Ruipeng Cai,
Kun Luo, Jianren Fan
Zhejiang University, China

High-dimensional flamelet chemtables are requiredfor describing multiple physics in turbulent combustion.
Representing the flamelet library using artificial neuralnetworks (ANN) can significantly reduce memory consumption. However, it is difficult to fit all the variables accurately based on the simple feedforward neural network(FNN) model due to the multi-scale distributions of thermochemical variables. To accurately and efficiently represent the multi-scale quantities, we develop a dual-scale
tabulation strategy that combines the multi-gate mixtureof experts (MMoE) and flamelet/progress variable (FPV)
model. In this strategy, two progress variables are defined
to represent the time-scale effect. One is the traditional
progress variable defined by major products for representing the mapping of small time-scale variables (e.g.,

19th International Conference on Numerical CombustionTrack15 Numerical methods for reacting flows

main species), while the other is an additional progress
variable defined by minor species for representing the
mapping of large time-scale variables (e.g., NO and PAHs).
The proposed tabulation approach is validated by comparing the predictions with those of the FNN tabulation
method and detailed chemistry in the a priori manner. The
results show that the proposed tabulation approach canbetter reproduce the detailed chemistry predictions thanthe FNN method.
Contact: txz@zju.edu.cn

On the impact of scalar boundedness
in high-order LES of a nonpremixed jet
flame
Ye Wang1, Armin Wehrfritz2, Evatt R. Hawkes1
1

The University of New South Wales, Australia, 2University of Turku, Finland

We carried out large-eddy simulations (LES) of athree-dimensional temporally evolving turbulent nonpremixed jet flame to evaluate the impact of numerical errors
from high-order numerical schemes to discretise convective terms. We focus on the effects of numerical oscillations and scalar unboundedness and compare a newly
proposed scheme against an ad hoc remedy to enforce
scalar boundedness in LES of nonpremixed flames. Suchnumerical issues are commonly encountered in under-resolved simulations like LES, especially when using high-order schemes, but their impact is rarely reported. The
research compares two high-order numerical schemesin LES against direct numerical simulation data. The first,
a high-order central-difference scheme with compact
filtering, generates significant numerical oscillations atunder-resolved scalar interfaces and subsequent massfraction excursions, resulting in an unstable simulation. Ad
hoc trimming of such excursions stabilises the simulation,
but residual oscillations contaminate radicals and heatrelease rate solutions. These inaccuracies accumulate
over time and cause non-physical changes in chemical reactions, leading to pronounced deviations in radical massfractions and reignition flame temperature. In contrast, a
newly proposed high-order bounded scheme avoids these
spurious oscillations and maintains mass fraction boundedness, yielding a stable LES and improved accuracy inflame reignition predictions. These observations demonstrate the detrimental effects of numerical oscillations,mass fraction excursions, and trimming on LES stability
and predictive accuracy. A comparison with other LES inthe literature also suggests that the influence of numerical schemes is comparable to that of combustion models,
highlighting the importance of using accurate high-orderschemes in turbulent flame LES.
Contact: ye.wang7@unsw.edu.auModelling of Turbulent Non-premixed
Blend of NH3/H2/CH4 in a Jet Flame
Using Flamelet Model

Richie Shaji Mathew, Dinesh Prabhakaran, Sayak Banerjee,
Raja Banerjee
Indian Institution of Technology Hyderabad, India

Hydrogen is emerging as a promising solution to mitigate the adverse environmental impacts of fossil fuels.
However, the practical challenges related to its storage
and transportation and the possibility of hydrogen embrittlement have presented significant challenges. Ammonia(NH3) is being actively considered as an alternative carbon neutral fuel. However, its low calorific value and low
flame speed are some of the challenges that needs tobe addressed before it can be widely used in combustion
applications. In this work, a semi-detailed NH3/H2/CH4/
n-C12H26 mechanism consisting of 242 species and 1769
reactions including both nitrogen oxides (NOx) and sootsub-mechanisms have been used to simulate combustion in a jet flame. As ammonia has a poor laminar flame
speed, blending it with methane and hydrogen will significantly improve its flame speed. The effect of NH3-H2-CH4
composition on emission of NOx, soot and unburnt NH3
is investigated at various ambient pressures. Additionally,
the effect of ambient pressure on total greenhouse gas
emission that includes the sum total of CO2 and N2O isinvestigated because production of N2O, which has a very
high greenhouse gas index, will be favored at elevatedpressures.
Contact: rajabanerjee@mae.iith.ac.in

Large-Eddy Simulation of Nanoparticle
Synthesis in Turbulent Spray Flames
Using a Lagrangian FDF Approach withDifferent Mixing Models

Amir Karimi Noughabi, Seung-Jin Baik, Irenäus Wlokas,
Andreas Kempf
University of Duisburg-Essen, Germany

Flames, providing stable thermal conditions, are theprevalent choice for nanoparticle formation, establishingflame-based methods as the standard in nanoparticle
production. While nanoparticle synthesis at the laboratory
scale typically exhibits laminar characteristics with moderate Reynolds numbers and low pressure, replicating these
conditions in pilot-scale operations is challenging, and turbulent flows are anticipated. The resultant nanoparticles
are influenced not only by coagulation and sintering but
also by the impact of turbulence on local particle number
concentration and morphology.
In the present study, the Lagrangian filtered probability

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Track15 Numerical methods for reacting flows

density function (FDF) method within large eddy simulation (LES) is employed to model iron oxide nanoparticle
synthesis in the spray flames. In the transported FDF
approach, no model is required for the source term ofeach nanoparticle section, while the conditional subgrid
diffusion effect needs closure through a turbulent mixing
model. Two classical mixing models, IEM (Interaction by
Exchange with the Mean) and modified Curl, are tested.
Additionally, an advanced approach, the Euclidean Minimum Spanning Tree (EMST) mixing model, is implemented
to assess the impact of localness in composition space. A
comparison of the three mixing models against measurements will be presented at the conference.
Contact: amir.karimi-noughabi@uni-due.de

Robust dynamic stencil construction for
high-order Adaptive Mesh Refinement
in Direct Numerical Simulation of
combustion
Stewart Cant1, Umair Ahmed2

University of Cambridge, United Kingdom, 2Newcastle University, United
Kingdom

1

Adaptive Mesh Refinement (AMR) provides the ability to ensure that mesh resolution is always sufficient inregions of the computational domain where the solution
is varying most strongly. This is especially importantin Direct Numerical Simulation (DNS) of combustion
where high accuracy is essential and flames are often
thin. High-order spatial reconstruction schemes basedon a finite-volume approach offer high accuracy together
with good conservation properties on the locally-adapted
mesh. Such schemes require fairly large and well-configured stencils to ensure accuracy and stability of the solution.
An algorithm has been developed that uses Singular
Value Decomposition of the spatial solution-reconstruction matrix to guide the construction of stencils on-thefly while guaranteeing the stability of the solution. The
algorithm has been implemented in the combustion
DNS code HAMISH which uses a fourth-order spatial reconstruction scheme with pointwise AMR, together withthird-order adaptive Runge-Kutta time-stepping. Results
have been obtained for a range of combustion test casesthat demonstrate the effectiveness and robustness of theapproach.
Contact: rsc10@cam.ac.uk

Track15-5 Numerical methods
for reacting flows (5)Chair: TBD
Friday, May 10; 13:00 - 15:00; Room F

A high-order compressible Eulerianstochastic fields solver based on AMReX
Tin-Hang Un, Salvador Navarro-Martinez
Imperial College London, United Kingdom

This work introduces a high-order compressible Eulerian stochastic fields solver built on the AMReX software
framework, offering a robust and versatile platform forsimulating turbulent reacting flows across all Mach numbers. While the probability density function model has a
successful track record of modelling turbulence-chemistryinteractions, implementation using the Eulerian stochastic
fields approach eliminates the need for coupling between
Lagrangian and grid-based solvers. The present implementation uses a fully coupled joint velocity-scalar-energy formulation, allowing closures of non-linear chemicalsource terms and non-ideal equations of state. The model
does not require LES-type closures and can adapt themesh to satisfy predefined resolved energy criteria. The
solver integrates many of AMReX's capabilities, including
adaptive mesh refinement and portability across various
CPU/GPU architectures. Complex geometries are supported using the embedded boundary method or a novel immersed boundary method. The core solver centres arounda 5th-order WENO/TENO reconstruction while chemical
reaction is powered by the PelePhysics library, supporting
arbitrary detailed chemical mechanisms, and direct or
matrix-free implicit integration. The code demonstrates
its effectiveness in accurately modelling turbulent reacting and non-reacting flows through standard benchmark
cases as well as challenging scenarios such as supersonic
combustion. Verification of the numerical methods andturbulence model will be presented.
Contact: thu17@ic.ac.uk

Bayesian optimization of in-situ adaptive
tabulation for marine diesel engine CFD
simulations
Daniel Virokannas1, Bulut Tekgul2, Èric Lendormy2, Ville
Vuorinen1
1

Aalto University, Finland, 2Wärtsilä Finland, FinlandThis study presents a comprehensive optimization
study of In-situ Adaptive Tabulation (ISAT) control param-180

19th International Conference on Numerical CombustionTrack15 Numerical methods for reacting flows

eters, in the context of enhancing the computational efficiency of reactive marine diesel engine simulations using
computational fluid dynamics (CFD). The methodology
integrates a multi-objective Bayesian optimization framework with the OpenFOAM CFD solver, enabling efficient
exploration of the ISAT parameter space. Standard Gaussian process surrogate models were combined with stateof-the-art acquisition functions, facilitating the discoveryof optimal configurations balancing the trade-offs between simulation accuracy and computational reduction.
The optimization campaign was conducted using a seriesof high-fidelity 3D CFD simulations of a Wärtsilä 20 marine
diesel engine under diesel combustion conditions. The
simulations incorporated detailed chemistry, a moving
computational mesh, and diesel surrogate fuel injection.
The results highlight the criticality of rigorously choosing
ISAT’s configuration parameters. Poor configurations
were shown to crash and stall simulations, resulting in a
net-negative effect on computational efficiency. Despite
this, a wide range of computational reduction was shown
to be possible, with varying effects on simulation accuracy. Finally, guidelines are provided for effective parameterselection in ISAT configurations.
Contact: bulut.tekgul@wartsila.com

Adjoint-based numerical andexperimental data assimilation for shocktube ignition delay predictions
Katherine R Pielemeier, Conrad Delgado, Jonathan
MacArt
University of Notre Dame, United States

Simulations of shock-driven ignition delay are crucial
to the design of airbreathing detonation-based combustors. High sensitivity to kinetic model parameters yields
high uncertainty of numerical calculations relative toexperiments, particularly when detailed kinetic models
are applied far from the conditions used to calibrate theelementary reactions. We present an application of solver-coupled data assimilation to shock-driven ignition delay time (IDT) predictions. The optimization method solves
the adjoint flow equations to calibrate semi-global kinetic
model parameters and additional corrective terms. Target
data are the flow fields obtained from detailed-chemistrycalculations and experimental pressure and temperatureprobes. Predictions for in- and out-of-sample conditions
are shown.
Contact: kpieleme@nd.edu

Development of a New Library in
OpenFOAM for Simulations of Reacting
Flows with Surface Reactions

Danh Nam Nguyen1, Jae Hun Lee1, Hae Won Seo2, Hyung
Jun Ahn2, Chun Sang Yoo1

Ulsan National Institute of Science and Technology, Korea, 2Hydrogen and
Low Carbon Energy R&D Lab, POSCO Holdings, Korea

1

Recently, hydrogen (H2) production has gained significant attention since H2 has emerged as an effective andclean alternative to fossil fuels, especially in the power
generation sector, to meet carbon neutrality by 2050.
While many experimental studies on the H2 production
from catalytic ammonia (NH3) decomposition have been
conducted, the numerical investigation on this field is limited due to lacking sufficient computational fluid dynamics(CFD) package for public use to handle surface reactions
occurring in catalytic processes. In that context, we developed a new surface chemistry library in OpenFOAM (OF)platform, a free and robust open-source CFD package,to provide a sufficient CFD tool for researchers working
on this field and combustion community since there isno such library officially available in OF. The developed
library can handle several types of typical surface reaction
rate models consisting of the basic Arrheninus form, sticking coefficient, and surface coverage dependence models.
It was validated against experimental data and previous
studies by performing two dimensional (2-D) simulationsof fixed packed-bed catalytic reactors. The results showed
a good agreement between predicted and benchmark
data, implying that our implementation is proper, and ourdeveloped library can be used for simulations of catalytic
processes with the utilizations of detailed micro chemical
kinetic models.
Contact: danhnam@unist.ac.kr

Explicit filtering LES of turbulent lifted jet
flames with a multi-regime combustion
model
Anindya Datta, Santosh Hemchandra
Indian Institute of Science, India

Computations of turbulent lifted jet diffusion flames are
performed using explicit filtering large eddy simulations(EFLES). LES solutions are obtained by solving species
transport equations using reduced chemical mechanisms.
A dynamically adapted spatial low pass filter is used limit
flame generated gradients in flow field variables to values that can be resolved by the LES mesh. A flame front
broadening factor is used to scale chemical source terms
to ensure the recovery of nominal 1D premixed flame181

Track15 Numerical methods for reacting flows

speed on resolution of the LES mesh. In a lifted jet flame,
oxygen from the co-flow stream diffuses into the core jetflow ahead of the flame attachment point. This leads toflow regions with both premixed and non-premixed combustion regimes. Therefore, a combustion regime sensor
based on the angle between mixture fraction and progress variable gradients is used to detect premixed andnon-premixed combustion regions and adjust the flame
front broadening factor appropriately based on how therelevant flame length scales compare with the local gridsize. We will compare DNS/experimental results for liftedhydrogen and ethylene jet flames with LES solutions forflame lift-off height, flame brush structure etc. in the final
work.
Contact: anindyadatta@iisc.ac.inTrack15-6 Numerical methods
for reacting flows (6)Chair: Ville Vuorinen
Friday, May 10; 15:20 - 17:00; Room Fmodelling challenges. Due to the very small injection diameter, the jets are laminar at the injection but turbulence
can develop in the free shear layers, which is challenging
for turbulence modelling. The sound speeds in hydrogenand air differ by a factor about four. This leads to a rapid
variation of the local Mach number in the mixing zone,
which can be challenging with respect to compressibility
for the present high-speed jets. The comparably highdiffusion coefficient of hydrogen with respect to the remaining species is a further challenge for combustion
modelling.
Different turbulence models as well as different combustion models utilizing global and detailed reaction
mechanisms will be applied and validated based on theavailable measurements.
[1] Kozlov, V.V. et al. Int. J. Hydrogen Energy 2016, 41, 2024020249.
[2] Kozlov, V.V. et al. Combust. Sci. Technol. 2019, 191, 1219–
1235.
[3] Shmakov, A.G. et al. Int. J. Hydrogen Energy 2017, 42, 1591315924.
Contact: alicemal@prof-benim.com

Numerical Analysis of Hydrogen Microjet
FlamesAli Cemal Benim

Düsseldorf University of Applied Sciences, Germany

Microburners are of interest because of their wide
application potential in engines, power efficient heatsources, compact thermovoltaic converters of energy andfurther devices. The main element of such burners is the
micronozzle supplying the burnable gas. When the latterdoes not contain oxygen, but mixes with air after the injection, a micro-diffusion flame results, which precludes
any danger of flashback. Hydrogen occupies a central rolefor clean and efficient energy supply. The scope of thepresent work is the numerical analysis of diffusion flamesof high-speed hydrogen microjets.
Microjet diffusion flames of hydrogen were investigated experimentally by Kozlov et al. [1,2] and Shmakov et al.
[3]. In those experiments, a quite interesting flame topology was observed, which was named as “bottleneck flame”.
Here, depending on the injection conditions, a compact
spherical/ellipsoidal flame in the burner nearfield wasformed that was followed by rather customary free-jet like
topology.
To the best of the author’s knowledge, such flames
have so far not been investigated computationally. Thus,
the purpose of the present study is the numerical analysis of such flames, to see if the measured flame patterns
can be predicted with sufficient accuracy. There are many

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Application of a reduced chemicalmechanism for combustion in vitiated air
conditions in RANS simulations
Daria Burot

Safran Aircraft Engines, France

In order to better take into account the effects of vitiated air in combustion processes in an after-burner, a new
reduced chemical mechanism called 2S_KERO_M2 [1] hasbeen implemented for reacting transported species RANS
simulations. It consists of two reactions and six transported species (kerosene, O2, N2, CO2, CO, H2O), in which
the pre-exponential constants are adjusted to match premixed flame speeds in rich conditions. The pre-exponential constants depend on both the local equivalence ratio
and the equivalence ratio in the oxidizer stream characterizing the reheat conditions. The implementation of
the scheme is validated against semi-detailed chemistryin 1D laminar flames for several values of the pre-burner
equivalence ratio. The methodology is then applied toa semi-industrial practical case [2], representing a bluffbody stabilized flame in vitiated air. Simulations are basedon the k-epsilon model and the Eddy-Dissipation Concept
for turbulence/combustion interactions. Liquid spray
injections are modeled using the lagrangian framework.
Heat release and equivalence ratio fields are compared tomean experimental data and LES computations and show
good agreement with regards to flame shape and position

19th International Conference on Numerical CombustionTrack15 Numerical methods for reacting flows

at different levels of vitiation.
[1] Mocquard, Clément, et al. "A two-step chemical scheme
for auto-igniting and propagating kerosene flames atreheat conditions." Combustion and Flame 248 (2023):
112558.
[2] Cross, Caleb, et al. "Determination of equivalence ratio
and oscillatory heat release distributions in non-premixed bluff body-stabilized flames using chemiluminescence imaging." Turbo Expo: Power for Land, Sea,
and Air. Vol. 54624. 2011.
Contact: daria.burot@gmail.com

Acceleration of multidimensional
simulations with detailed kinetics via
Chemistry Agglomeration
Alberto Cuoci1, Temistocle Grenga2
1

Politecnico di Milano, Italy, 2University of Southampton, United Kingdom

In this work, we present a numerical technique basedon the concept of Chemistry Agglomeration [1] to accelerate the integration of the chemical step in the context
of operator-splitting methods. The proposed techniqueconsists in splitting on-the-fly the kinetic mechanism into
clusters (or sub-mechanisms) with a smaller number of
species via a partition/clustering algorithm. Once the clusters of species have been identified, the integration of thechemical step, instead to be carried out on the complete
kinetic mechanism, is split into a number of sub-steps
equal to the number of identified clusters. Since the costof chemistry integration increases more than quadraticallywith the number of species, solving a sequence of smaller
sub-mechanisms is computationally less expensive thandirectly solving the entire mechanism.
Two benchmark cases have been considered: i) a laminar, pulsating laminar coflow diffusion flame fueled by a
mixture of C2H4 and N2; ii) a 2D, turbulent, non-premixed
flame burning n-C7H16 subject to decaying isotropic
turbulence. In both cases, a detailed kinetic mechanism
accounting for the formation of soot particles and aggregates was considered. The results are promising, showing
both accuracy and computational efficiency, demonstrating the potential of the methodology for multidimensional
CFD simulations of reactive flows with complex chemistry.

Effects of radiation- and combustor-wallboundary condition on LES of turbulent
combustion
Björn Jarfors, Alessandro Ercole, Christer Fureby
Lund University, Sweden

Numerical simulations of turbulent combustion ischallenging due to the combined complexities of turbulent flow and combustion chemistry. High fidelity simulation models such as Large Eddy Simulations (LES) withfinite rate chemistry effects and small detailed reaction
mechanisms, whereby the combustion chemistry is explicitly solved for, have in spite of its high cost, provided
increased understanding and predictive capabilities. Two
aspects of such simulations that often are neglected because of their added complexity and information deficit
are thermal radiation and the influence of the thermal
combustor wall boundary conditions. Thermal radiation
can be included in combustion simulations using models
such as the P1 or Discrete Ordinates (DO) models but additional terms due to the filtering in LES occur and mustbe treated. Information regarding the actual benefits ofradiation modeling is scares, and here we aim to provide
qualitative and quantitative data for a few selected swirland bluff-body- stabilized flames for which experimental
data is available. For confined turbulent flames the issueof thermal combustor wall boundary conditions is equallyor even more important. Due to lack of information fromexperiments it is challenging to infer sufficiently accurate
thermal boundary conditions. Here, we will investigate thesensitivity to different combustor wall boundary conditions
and their effects of the turbulent flame and its dynamics.
Contact: bjorn.jarfors@energy.lth.se

References[1] Wang J.H., Pan S., Hu X.Y., Adams N.A., A species-clusteredsplitting scheme for the integration of large-scale chemical kinetics using detailed mechanisms, Combustion and
Flame 205, p. 41-54 (2019)
Contact: alberto.cuoci@polimi.it

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Track17 High-performance computing for
combustion applications

Track17-1 High-performancecomputing for combustion
applications (1)senting subsequent mixing and ignition accurately.

Chair: TBD
Wednesday, May 8; 10:40 - 12:20; Room H

The Effect of Combustion-Induced
Instabilities on Shock-trains in a Scramjet
Isolator

Simulation of low-temperature plasma
ignition of ethylene/air mixtures atscramjet cavity conditions with highfidelity models for non-equilibrium
plasma discharge, acoustic and vibrational
relaxation, hydrodynamic mixing, andmixture ignition
Alfredo Jose Duarte Gomez1, Nicholas Deak2, Lucas
Esclapez2, Marcus Day2, Fabrizio Bisetti1

University of Texas at Austin, United States, 2National Renewable Energy
Laboratory, United States1

A comprehensive framework based on the AMReX
library and associated reactive flow solvers is assembled
to simulate the ignition of ethylene/air mixtures at 0.5
atm and 600 K, corresponding to conditions in the cavityof scramjets. The modeling framework features a plasma
solver capable of simulating streamer propagation andenergy deposition over time scales of 100 ns using chemical plasma fluid models and physics-based closures. Following isochoric energy, which creates a large populationof molecules in electronic and vibrational non-equilibrium,
the reactive compressible flow solver PeleC is used tosimulate the outward propagation of shock waves during
the expansion of hot gases in the plasma channel up to
10-50 us. Next, the solver PeleLMeX integrates the lowMach restriction of the Navier-Stokes equations for up
to 1-10 ms, capturing the ignition of a flame kernel. The
framework is computationally efficient, enabling the simulation of multiple nanosecond voltage pulses at practicalrepetition frequencies with high-fidelity models void ofcommon simplifying assumptions used in previous work.
Based on our large-scale simulations, a complex interplay
between energy deposition, hydrodynamic mixing, andignition emerges, whereby the first-principles simulationof plasma discharges over multiple pulses is key to repre-

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Contact: aduarteg@utexas.edu

Jagmohan Singh, Shivank Sharma, Venkat Raman
University of Michigan, United States

The isolator plays a vital role in the operation of ascramjet engine, providing air compression through asequence of shocks known as the 'shock-train'. The development of the boundary layer along the isolator walland the instabilities due to the combustion downstreamof the isolator are known to affect the shock-train dynamics and, consequently, the overall performance of thescramjet. This study investigates this complex dynamics
of shock-trains using Embedded-boundary (EB) method
and adaptive mesh refinement (AMR). The main goal is tounderstand how combustion instabilities downstream of
the isolator affect the shock-train dynamics. The computational model is axisymmetric and includes a cavity combustor downstream of the isolator. Ethylene is used forthe fuel which is injected to the air upstream of the combustor. The EB method is used for modeling the geometry
which avoids the need for a complex geometry-conforming mesh whereas AMR provides finer grid resolution in
the regions of interest keeping the computational cost
tangible. A precursor simulation is used for generating
turbulent inflow conditions which allows to study the interplay between combustion and shock-trains for various
inflow conditions. The results of shock-train behavior withand without combustion are discussed.
Contact: jagmohan@umich.edu

19th International Conference on Numerical CombustionTrack17 High-performance computing for combustion applications

GPU-based DNS enables dissection of
cracking, turbulent mixing, and oxidation
processes in NH3/H2 jet flames
Driss Kaddar1, Hendrik Nicolai1, Christos Emmanouil
Frouzakis2, Mathis Bode3, Christian Hasse1

TU Darmstadt, Germany, 2ETH Zurich, Greece, 3Jülich Supercomputing
Centre, Germany

1

Ammonia-hydrogen blends will play a pivotal role for
future carbon-free combustion systems. To minimize
remaining emissions in ammonia combustion, staged
combustion systems, such as rich-quench-lean technologies, are proposed. However, the combustion behavior of
turbulent rich ammonia-hydrogen mixtures lack comprehensive understanding. In particular, the quantification ofcomplex phenomena like partial cracking, hydrogen slip,
and post-flame stratification and their interaction withflame structures and pollutant formation remains insufficient.
This is a major scientific barrier hindering the realization of NH3/H2 blends for carbon-free combustion.
Recent HPC advancements, particularly in GPU-based
systems, enable combustion DNS beyond academic configurations.
Utilizing nekCRF, a new GPU-based spectral element
solver based on nekRS, we perform finite-rate chemistry
DNS of a rich, turbulent premixed jet flame. This uniquedata set provides fundamental insights into the intricate
interaction of reactions and turbulence that are crucial fordeveloping future models. The analysis focuses on NH3/
H2 interaction, revealing residual H2, minimized NH3 slip,
and enhanced heat release through turbulent mixing. Byleveraging GPU acceleration and employing a novel spectral element solver, this research not only advances ourunderstanding of ammonia combustion but also showcases a paradigm shift in computational efficiency, offering apromising avenue for developing sustainable energy solutions.
Contact: nicolai@stfs.tu-darmstadt.de

Fuel-specific code generation forthermochemistry and transport properties
for CPU- and GPU-based solvers
Bogdan Andrei Danciu1, Stefan Kerkemeier2, Christos
Emmanouil Frouzakis1
Swiss Federal Institute of Technology Zürich, Switzerland, 2Micodat
Computer GmbH, Germany

1

The transition to green energy requires the adaptationof combustion applications to carbon-free fuels such ashydrogen and ammonia. Achieving this objective is notpossible without highly accurate direct numerical simula-tions (DNS) to elucidate the complex physical phenomena. In turbulent combustion DNS, a significant fractionof the total simulation time is spent on the evaluation ofchemical source terms, thermodynamic properties andtransport coefficients. In this work, we present a software
package that automatically generates efficient fuel-specific kernels for these quantities. The starting point is
a Cantera yaml file containing the reaction mechanism
and the data required for the calculation of the thermodynamic and transport properties, which is processed togenerate the fuel-specific kernels. Different strategies
are used to optimize the kernels for CPUs and GPUs, withthe latter being further optimized for the respective GPUarchitecture. The accuracy of the generated kernels is automatically checked against reference values for species
production rates, thermodynamic properties and transport coefficients calculated using Cantera and stored forcomparison. The kernels' performance is evaluated on thelatest CPU and GPU architectures from Nvidia, AMD andIntel.
Contact: danciub@ethz.ch

Track17-2 High-performancecomputing for combustion
applications (2)Chair: TBD
Wednesday, May 8; 13:30 - 15:10; Room H

Multistep high-order time adaptive
coupling of black-box solvers for
multiphysics simulations
Laurent Francois1, Marc Massot2
1

ONERA, France, 2CMAP - École Polytechnique, France

Multiphysics simulations are paramount in many applications and often occur through the coupling of various
physics in different physical domains coupled throughlower-dimensional surfaces. Relying on code heritage,
it is desirable to design a coupling strategy that allows
to reuse existing model-specific solvers with minimal
modifications. However, in most existing numerical coupling strategies, the design of such strategy comes with
low-order accuracy in time and difficulties with regard tocontrolling the errors related to the coupling strategy. In
this contribution, we introduce a novel strategy that ensures adaptive, accurate and stable coupled simulations.
The principle is a multistep coupling scheme, which relieson the history of the exchanged quantities to enable ahigh-order accurate coupling with time adaptation anderror control. Explicit and implicit variants are discussed.

185

Track17 High-performance computing for combustion applications

Numerical experiments conducted with an open-source
demonstrator on a conjugate heat transfer problem
show that high-order convergence can be reached, andthat stability is favourable compared to other classicalapproaches. We propose some insight on the numericalanalysis of the proposed strategy, and extensions to simulations in combustion as well as the case of volume coupling are discussed.
Contact: laurent.francois@onera.fr

AATE: Advanced Analysis Tool forEnginesHeikki Kahila1, Bulut Tekgul1, Karri Keskinen1, Mahmoud
Gadalla1, Èric Lendormy1, Henry Weller2
1

Wärtsilä Finland, Finland, 2 CFD Direct Limited, United Kingdom

In this study, we introduce an open-source platform forsimulation, analysis, and post-processing of internal combustion engines (ICE) in the OpenFOAM framework—AATE((/ˈɑːte X/), the Advanced Analysis Tool for Engines. We
introduce a set of developments that enables the user toachieve full-cycle engine simulations within OpenFOAM.
The developments consist of a new, robust and flexible
mesh deformation method which is seamlessly coupledwith run-time MPI-parallelised volume mesh-to-meshmapping and arbitrary non-conformal sliding interface
techniques. To ensure consistency, efficiency, and extensibility, the implementation is carried out in collaboration
with the core developers of OpenFOAM from CFD-Direct
Limited. With these developments, any user can execute
an engine simulation with moving valves and piston overunlimited cycles. The functionalities and performance of
AATE is demonstrated on a publicly available, non-proprietary engine case, TCC-III from University of Michigan. To
make the benchmark case useful for the engine community, we demonstrate an automated meshing solution andprovide examples of efficient reactive simulation setup
and post-processing in engine context. The core engine
solver will be available in future OpenFOAM-dev releases,
while the TCC-III case will be available online separately.
Contact: bulut.tekgul@wartsila.com

Shared Memory based Hybrid In-Situ
Adaptive Tabulation of Vapor-Liquid
Equilibrium Solutions and Detailed
Chemistry

Hongyuan Zhang, Navneeth Srinivasan, Suo Yang
University of Minnesota, Twin Cities, United States

Vapor-Liquid Equilibrium (VLE) model, a family of186



first-principled thermodynamic models for transcriticalmultiphase flows, faces computational challenges in
multi-component systems. To address this, a novel ISATVLE method is developed, leveraging the in-situ adaptive
tabulation (ISAT) technique to enhance computational
efficiency and reduce memory usage by the tabulation.
However, parallelizing ISAT-based CFD simulations encounters performance degradation as the number ofcores increases due to the local to core nature of the ISAT
table. To overcome this, a novel shared memory ISAT
formulation using MPI-3 for CFD simulations is introduced,
along with a hybrid ISAT retrieval algorithm incorporating
both local and shared ISAT tables for optimal computational performance, efficient memory management, andpredictive accuracy. A load-balancing algorithm within theshared memory architecture is also introduced to improve
the parallel scaling of the ISAT model. Rigorous testing in
high-pressure transcritical two-phase simulations demonstrates a significant speed-up factor (10 to 60) and controlled ISAT errors within 1%, showcasing commendable
accuracy. The model is also extended to combustion simulations, integrating a shared ISAT-based tabulated dynamic chemistry model (TDAC), introducing an advanced
and versatile approach for enhancing computational efficiency and accuracy.
Contact: srini237@umn.edu

Development of high-order solver for
ML-accelerated reacting flow simulations
Kai Wen Beverley Yeo, Matthias Ihme
Stanford University, United States

Recent advances in high-performance computing andartificial intelligence have enabled opportunities for theadvancement of combustion engineering. One such possibility is the integration of machine learning (ML) withhigh-fidelity reacting-flow simulations for reliable predictions. However, ML for combustion is still limited by slow
data transfer speeds between the CPU and GPU andlegacy software. Therefore, we propose a new Discontinuous Galerkin (DG) solver built using the JAX library forhigh-performance simulations on CPUs, GPUs, and TPUs.
The current work has two main advantages: Firstly, mostnumerical schemes for simulation of combustion problems employ lower-order finite volume discretization
techniques, which may not sufficiently capture smallscale flow structures and reacting zones. In contrast, theDG method offers high-order accuracy on unstructured
meshes with good dispersion and dissipation properties, with a high arithmetic intensity and lower memory
requirements. Secondly, the use of JAX, a framework
designed for ML applications, allows for a direct coupling

19th International Conference on Numerical CombustionTrack17 High-performance computing for combustion applications

between the flow simulation and any ML applications.
The resulting simulation framework will be demonstrated
in application to online-learning of a transient flame configuration.
Contact: yeokwb@stanford.edu

Population-based optimization ofcomplex reacting flows: Pilot study
Kazuki Maeda

Purdue University, United States

Optimization of complex reacting flows involving multi-component and multiphase flow phenomena is often
challenging due to the unsteady and multi-scale nature of
the flows. In this study, we present a computational strategy for model-free, population-based optimization of suchflows. In the method, to optimize a set of flow parameters
for targeted objectives, groups of simulation samples are
distributed and iteratively search a parameter space untilconvergence. We evaluate the efficiency and accuracy ofthis method using canonical model problems. The method is implemented in an in-house compressible flow code
to demonstrate optimization of three-dimensional highspeed reacting flows on multiple GPUs in a scalable fashion.
Contact: kmaeda@purdue.edu

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Track18 Simulations with AI technologies

Track18-1 Simulations with AI
technologies (1)Chair: TBD
Wednesday, May 8; 10:40 - 12:20; Room K

Machine Learning Tabulation of
Thermochemistry of Polycyclic Aromatic
Hydrocarbon (PAHs) and Application to
Turbulent Sooting Flames: An approach
Combining DRGEP and HFRD-MMLP
Anxiong Liu

Zhejiang University, China

This work applies a machine learning tabulation
methodology for the thermochemistry of combustion
containing polycyclic aromatic hydrcarbons (PAHs), toaccelerate the real-time computation of the large-size
PAH mechanism in turbulent sooting combustion. Thisapproach firstly uses DRGEP method to select a certain
number of species from the PAH mechanism, and thenproposes the hybrid flamelet/random data and multiple
multilayer perceptrons (HFRD-MMLP) method to evaluate
the concentration changes of selected species at every
time step. The essence of the HFRD method lies in thegeneration of training data, which enhances the capacity of generalization for the reactive composition spaceencountered in practical turbulent combustion by using
the random process to expand the training dataset fromlaminar flamelets. The MMLP artificial neural networks(ANNs) are then trained to predict different composition states, to improve the ANN prediction accuracy. To
validate the effectiveness of the ANNs, they are initiallytested on laminar flamelet simulations with varying strain
rates and then on 1-D laminar premixed flames with varying equivalence ratio. Subsequently, tests are conductedon the Santoro laminar diffusion sooting flame and the
DLR turbulent lifted sooting flame. The results regarding
species mole fractions, temperature, PAHs and soot volume fraction show overall excellent agreement with thedirect integration method. The proposed DRGEP-HFRDMMLP method achieves speed-up factors of over 52 forthe reaction step, in the LES-PDF simulation with the PAH
mechanism in this work, surpassing the speed-up factors
of approximately 12–14 and 16.2 in previous works on the
GRI-1.2 mechanism for CH4/H2 combustion, and the DME

188mechanism, respectively. This indicates that the proposedmachine learing method is highly effective for large size
mechanisms in reducing the computational cost by replacing a significant number of highly stiff ordinary differential equations (ODEs) integration.
Contact: axliu22@zju.edu.cn

Mitigating chemical stiffness in turbulent
reacting flow simulations via an adaptive
reduced-order model with timedependent bases
Ki Sung Jung1, Hessam Babaee2, Jacqueline H Chen1,
Cristian E Lacey1

Sandia National Laboratories, United States, 2University of Pittsburgh,
United States1

Direct Numerical Simulation (DNS) of turbulent reacting flows is often prohibitively expensive for practicalengineering problems due to the large number of transport equations involved and the wide range of length andtime scales associated with turbulence and combustion.
Reduced-order models (ROMs) can dramatically reduce
the number of transport equations, mitigating the cost of
high-fidelity simulations with a minimal sacrifice in accuracy. However, identifying low-dimensional representationsof the high-dimensional thermochemical state often depends on offline training, restricting such ROMS to conditions similar to that of expensive, pre-existing high-fidelity
training datasets. Recently, a novel ROM approach named
time-dependent bases with CUR decomposition (TDBCUR) was proposed that adaptively constructs and updates a ROM in time by leveraging physics and the instantaneous thermochemical information instead of expensive
training data. Though promising, the initial formulationof TDB-CUR does not directly reduce the computational
cost associated with stringent time step requirements
imposed by stiff chemical systems. The present work aims
to further reduce the computational cost of TDB-CUR by
increasing the allowable time step. Present improvements
are benchmarked against canonical turbulent reacting
flows, demonstrating as much as an order of magnitude
reduction in computational cost as compared to the original TDB-CUR formulation.
Contact: celacey@sandia.gov

19th International Conference on Numerical CombustionTrack18 Simulations with AI technologies

Optimizing Mesoscale Combustor
Power using Taguchi Orthogonal Array,
Computational Fluid Dynamics andMachine Learning
Vinay Sankar, Sudipto Mukhopadhyay
Indian Institute of Technology Jodhpur, India

With technological advancement, there is an increasing
shift towards miniaturizing engineering systems . Ensuring
electric power to these miniature systems using compact power sources is a concern. Compared to batteries,
mesoscale combustors offer better energy density andcan provide instantaneous power through combustion.
Designing a compact combustor with maximum power
output plays a critical role in developing this kind of powersystem. Stepped combustors are suited for better flamestability under varying power output . The different geometric parameters of the step combustor, such as step
length and step diameter, impact the combustor's performance and power output. Designing a stepped combustor
with optimum geometric parameters to achieve maximum
power output is tedious using conventional numericalor experimental methodologies. Machine learning (ML)techniques can be utilized to arrive at an optimal design
with fewer design iterations. This work optimizes the combustor geometry to achieve maximum radiation powerfrom the combustor walls for a Thermophotovoltaic (TPV)system. The proposed methodology utilizes the Taguchi
method, Computational Fluid Dynamics (CFD), and neuralnetworks. The number of CFD simulations used to train
the neural network is reduced using the Taguchi orthogonal array method. Next, the premixed H2/air combustion
simulations are carried out for the design space obtained
from Taguchi method. Finally, using the simulation data,a Back Propagation Neural Network (BPNN) technique isused to achieve the optimal step diameters . The method
significantly reduces the design space and time to obtainthe configuration with maximum radiative power.
Contact: sankar.2@iitj.ac.in

React-DeepONet: A Combustion
Chemistry Acceleration Framework for
CFD
Anuj Kumar, Tarek Echekki

North Carolina State University, United States

A combustion chemistry acceleration scheme for implementation in reacting flow simulations is developed
based on deep operator nets (DeepONets). The scheme
is based on a mapping of a subset of the thermochemical
scalars' vector between incremental and adaptive time

steps. The subset corresponds to variables that are adequate to represent the evolution of the chemical system.
The DeepONet-based scheme also relies on a mapping of
the solution of this subset onto a corresponding solution
at an adaptive time increment to overcome the restrictive requirements of integrating such solutions with stiff
chemistry. Training for the DeepONet is also implementeddifferently from previous approaches to the solution of
PDEs with DeepONets. Instead of constructing solutions
from their initial to their final states using DeepONets, thetraining relies on prescribed short-horizon time windows
for training where intermediate solutions also serve as
initial states for training. An additional framework of latent-space kinetics identification with modified DeepONet
is proposed, which enhances the computational efficiency
and widens the applicability of the proposed scheme. The
scheme is demonstrated on the ``simple'' chemical kinetics
of hydrogen oxidation and the more complex chemical
kinetics of n-dodecane high- and low-temperatures. The
proposed framework accurately learns the chemical kinetics and efficiently reproduces species and temperature
temporal profiles. Moreover, a very large speed-up witha good extrapolation capability is also observed with theproposed scheme. Measures of enforcing element/massconservation as well as integration of the framework within a CFD code are implemented showing important speed
up and memory saving with a CFD simulation.
Contact: techekk@ncsu.edu

Track18-2 Simulations with AI
technologies (2)Chair: Michael E Mueller
Co-Chair: Hiroshi Gotoda
Wednesday, May 8; 13:30 - 15:10; Room K

Surrogate modeling of the methane
diffusion combustion field using thepseudo-time stepping-based physicsinformed neural networks

Zhen Cao, Kun Luo, Kai Liu, Yuzhou Cheng, Liang Jiang,
Zhentao Pang, Jianren Fanzhejiang university, China

The physics-informed neural networks (PINNs) has
emerged as a popular deep learning framework extensively applied in the field of computational science, particularly in computational fluid dynamics (CFD). In thisstudy, we propose a novel PINNs framework based on theconcept of pseudo-time stepping (PTS-PINNs), inspired by
the traditional approach in CFD. The proposed framework

189Track18 Simulations with AI technologies

is validated through experimental investigations of thetwo-dimensional steady-state methane laminar diffusion
combustion. The results demonstrate that the conventional PINNs framework encounters difficulties in training
the methane combustion process and requires the initialization of a high-temperature field to ensure the correctconvergence path. In contrast, the pseudo-time stepping-based PINNs exhibits the ability to rapidly converge
from a random initial field to the final stable combustion
state, with a relative error of less than 10% compared tothe traditional CFD numerical solution. The effectivenessof PTS-PINNs in solving the combustion system can be
attributed to its convergence path aligning with the physical evolution direction. In contrast, traditional PINNs tend
to converge towards the direction of minimizing the loss
function, which may not necessarily align with the laws ofphysics. In summary, the PTS-PINNs framework presents
a promising avenue for neural network solutions in combustion systems.
Contact: 12227126@zju.edu.cn

Prediction of laminar burning velocity forpremixed ternary ammonia/hydrogen/methane-air flames using ensemble
learning

Cihat Emre Ustun1, Sven Eckart2, Agustin Valera-Medina3,
Amin Paykani1
Queen Mary University of London, United Kingdom, 2Technische
Universität Bergakademie Freiberg, Germany, 3Cardiff University, United
Kingdom1

Zero-carbon fuels, such as hydrogen and ammonia,
play a crucial role in the energy transition by providing
cleaner alternatives to natural gas (methane), particularly in industrial combustion systems. Binary and ternary
blends of these fuels offer a transitional, low-carbon solution in the near future. Laminar burning velocity (LBV),a fundamental combustion property, varies significantly
for ammonia, hydrogen, and methane. While the LBV ofbinary blends of these fuels has been extensively studied,research on ternary blends is limited. This study aims toutilise ensemble learning approach to predict the LBVof ternary ammonia/hydrogen/methane-air mixtures fora large parameter range. The training dataset comprises experimental data from numerous publications (>90
papers) and synthetic data generated through 1D freely
propagating premixed flame simulations in Cantera, using
a detailed chemical kinetic mechanism. Three machinelearning (ML) algorithms −artificial neural networks (ANN),
Gaussian process regression (GPR), and extreme gradient boosting trees (XGBoost)− are trained, validated andoptimised. Subsequently, a simple ensemble averaging

190



method is employed to mitigate overfitting and enhancerobustness. The ensemble model achieves a R2 of 0.991,
with an inference time approximately 8,000 times fasterthan the 1D simulation run time. The final ensemble model
offers efficient and accurate predictions LBVs for ammonia/hydrogen/methane-air mixtures at T = [295−756K], P =[1−10bar], φ = [0.5−1.8] and all possible blending ratios, enabling discovery of conditions that have not been studied
experimentally.
Contact: exy068@qmul.ac.uk

Three-dimensional Convolutional Neural
Networks for Enhanced Turbulence
Modeling in Large-eddy Simulations ofPartially Premixed Swirl Flames

Zhentao Pang1, Kai Liu2, Kun Luo1, Jianren Fan1, Zhen Cao1,
Liang Jiang1, Yuzhou Cheng2, Anxiong Liu2

1
State Key Laboratory of Clean Energy Utilization, Zhejiang University,
China, 2Shanghai Institute for Advanced Study of Zhejiang University, China

Three-dimensional convolutional neural networks forenhanced turbulence modeling in large-eddy simulationsof partially premixed swirl flames subgrid-scale (SGS)
phenomena in reacting flows, such as partially premixed
swirl flames. These flows exhibits challenges like pressure
expansion, abrupt density reduction, and stiff viscosity
increase, which are not adequately captured by standard eddy-viscosity models or conventional data-driven
approaches like fully connected neural networks (FCN).
This study introduces an advanced three-dimensional
convolutional neural network (3D-CNN) designed to accurately model SGS stresses and scalar fluxes. This model,
leveraging spatial inputs of first-order velocity and scalar
gradients across local and adjacent grid points, effectively
captures the SGS dynamics of turbulent combustion without relying on eddy-viscosity assumptions. In a-priori tests
comparing the proposed 3D-CNN with traditional models
such as the Smagorinsky model (SM), velocity gradientmodel (VGM), and FCN, the 3D-CNN demonstrates superior performance in predicting SGS variables, evidenced byhigher correlation coefficients. Additional posteriori tests
confirm the model's applicability and effectiveness in LES
codes. This research underscores the value of integrating
spatial inputs and 3D convolutional networks in enhancing
the accuracy and generalizability of SGS turbulence models for turbulent combustion LES.
Contact: 12227097@zju.edu.cn

19th International Conference on Numerical CombustionTrack18 Simulations with AI technologies

Deep learning for sub-filter density
function prediction in turbulent
combustion
Hanying Yang, Nedunchezhian Swaminathan
University of Cambridge, United Kingdom

Presumed filtered density function (FDF) approaches
are widely used in sub-grid scale (SGS) modelling for turbulent combustion simulation. However, this numericalapproach brings challenges for several conditions ofinterest, such as combustion with extinction and reignition and multi-regime burners. Many recent studies havedemonstrated that the artificial neural network (ANN) is asuitable candidate. On the other hand, the FDF prediction
highly depends on the training dataset due to the ANN’s
limitations in extrapolation, which limits the application of
the ANN in practice.
Concurrently, generative models have exhibited improved predictive ability in language and vision with highgenerality and have been leveraged in biology and materials engineering. This work develops a diffusion model togenerate the joint FDF of the progress variable and mixture fraction by inputting the first and second moments ofthese two key variables. Through the training with limited
data of MILD (Moderate, Intense and Low Dilution) combustion, this model illustrates an improved performance
than the conventional ANN for a variety of conditions,
including MILD combustion at different dilution levels (notused in the training sets), various filter sizes and otherflame cases. The detailed results and analysis will be discussed during the presentation.
Contact: hy345@cam.ac.uk

Simulation of supercritical CH4/O2 flamewith hybrid data-physics based machinelearning method

Yuqing Cai1, Ruixin Yang2, Hu Wang1, Jiayang Xu3, Zhi.X
Chen2

Tianjin University, China, 2Peking University, China, 3AI for Science Institute,
Beijing, China

1

We developed a highly accurate thermodynamic property and reaction source term surrogate model using a
hybrid canonical and random data sampling method. The
thermodynamic network is an MLP model with three hidden layers and ODE network is a multi-segment network.
Depending on Chemical Explosion Mode Analysis (CEMA)
theory, the first stage identified the combustion modes(explosive mode, decaying mode, etc.). The explosivemode needs to enter the second stage which is used to
predict reaction source terms. And the remaining modesare assumed to be inert and skip the chemical computation. These models are applied to supercritical CH4/
O2 flame with Homogeneous Isotropic Turbulence (HIT).
A neural network with 40,000 neurons and 5.6 million
training data achieves good agreement in major thermodynamic properties such as density, viscosity etc. For the
ODE surrogate model, we found that the average reaction
rate in the inert region does not change significantly,
which are redundant noise points for the chemical network. Filtering out inert zone data reduces the MAE andtraining epochs of networks with the same parameter by
50% and the predictions for major and minor components
exhibit good consistency. The average computation time
for thermodynamic property and reaction source terms
is reduced by a factor of 10, and memory consumption is
only within 20MB.
Contact: yuqing_cai@tju.edu.cn

Track18-3 Simulations with AI
technologies (3)Chair: Hiroshi Gotoda
Thursday, May 9; 09:50 - 12:30; Room F

Hybrid LES-CFD modeling with machinedlearning methodology on TangentiallyFired Coal Combustion System
Siyi Huang1, Min-min Zhou1, Wojciech Adamczyk2, Lunbo
Duan1, Philip J. Smith3
1

SouthEast University, China, 2Silesian University of Technology, Poland,
University of Utah, United States

3

High-fidelity modeling is a valuable tool for investigating complex multi-scale multi-physics mechanisms in industrial-scale coal combustion. However, deploying thesemodels for industrial applications requires additional steps
to enhance accuracy. This work introduces a hybrid LESCFD model with a machine learning approach to improvepredictive capabilities by quantifying uncertainty from prediction results and experimental data. The analysis builds
on high-fidelity LES-CFD simulations for industrial-scalecoal combustion. The newly proposed machine-learningmodel integrates Bayesian-based and Bound-to-Boundmodels, defining predictivity through statistical inference
from information propagated from models and experiments.
This research successfully applies the hybrid methodology to coal combustion in a GE-Alstom’s pilot-scale BSF.
The outcomes advance model prediction accuracy for
key quantities of interest (QoI’s): heat flux to the wall, gas
temperature, and oxygen concentration. Machine learning

191

Track18 Simulations with AI technologies

expands the parameter space, ultimately finding consistency between simulation and experiment. Predictions arebound with quantified uncertainty, providing informative
insights for industrial applications. The analysis informs
modelers and experimentalists of allowable ranges for
simulation input parameters, ensuring useful predictions.
The predictivity produced by this method directly
informs the optimization of industrial combustion system operations, bridging high-fidelity modeling with lab
results to real engineering applications. Moreover, thisresearch exemplifies the power of the hybrid approach,combining high-fidelity simulation with machine learning
methodology, applicable to a wide range of complex
emerging problems.
Contact: huangsiyi2001@gmail.com

Detailed simulation of LOX/GCH4 flamevortex interaction in supercritical TaylorGreen flows with machine learning
Jiayang Xu1, Yifan Xu2, Zifeng Weng3, Yuqing Cai4, Runze
Mao2, Ruixin Yang2, Zhi Chen51
AI for Science Institute, Beijing, China, 2Peking University, China, 3Tsinghua
University, China, 4Tianjin University, China, 5State Key Laboratory of
Turbulence and Complex Systems, Aeronautics and Astronautics, College
of Engineering, Peking University, China

This study introduces detailed computational analysesof liquid oxygen and methane (LOX/GCH4) combustion
in a Taylor-Green vortex (TGV) configuration, under supercritical conditions—significant for the development ofrocket engines, industrial powertrains, and modern gas
turbines. We adapt the classical three-dimensional TGV
test case, incorporating real fluid behaviour, to explore
the dynamics of reactive flows at extreme pressures andtemperatures. The simulation contrasts the conventional
ideal gas approximation with the Peng-Robinson (PR)cubic state equation, highlighting the pronounced effectsof substantial density variations inherent in real gases on
flame behaviour and vortex dynamics. Enhanced flame
stretching and quenching are observed with real fluids, as
opposed to their ideal counterparts. To mitigate the highcomputational demands of calculating real-gas thermophysical properties, we employ a deep learning frameworkwith deep neural networks (DNNs). This novel approach isvalidated against the reactive TGV configuration, showing
high predictive fidelity and a 13-time increase in computational efficiency compared to traditional methods.
This research not only sets a reference point for subsequent investigations into three-dimensional supercriticalflame-vortex interaction but also suggests that leveraging
machine learning could substantially advance the high-fidelity simulation of supercritical combustion.
Contact: jx278@cantab.ac.uk

192

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Reducing memory requirements of In-Situ
Adaptive Manifolds using neural network
coupled binary trees
Stephen Trevor Fush, Israel J Bonilla, Michael E Mueller
Princeton University, United States

Manifold-based combustion models can decrease thecost of turbulent combustion simulations by projecting
the thermochemical state onto a lower-dimensional manifold, allowing the thermochemical state to be computed
separately from the flow solver. Solutions for the manifold equations have been traditionally precomputed andpretabulated, resulting in large memory requirements andsignificant precomputation cost even for simple problems.
In-Situ Adaptive Manifolds (ISAM) allows for solutions to
the manifold equations to be computed as the simulation progresses and stored using binary trees with In-Situ
Adaptive Tabulation (ISAT), allowing for the use of moregeneral models. While ISAT has helped reduce the memory requirements from previous pretabulation approaches,as the model complexity grows, the memory requirementsof ISAT will eventually become too large. In this work,neural networks are used to replace portions of the binary
tree within ISAT to decrease the memory requirementsof the ISAT database. Analysis of the trade-off between
fewer, larger, more global neural networks each replacing
more leaves and more, smaller, more local neural networks each replacing fewer leaves is explored in detailincluding both memory and retrieval time. Data from a
Large Eddy Simulation of a canonical turbulent flame isused to analyze this trade-off.
Contact: sf5201@princeton.edu

High-resolution three-dimensional
reconstruction of velocity for turbulent
flames with physics-informed neuralnetworks
Shiyu Liu, Haiou Wang, Kun Luo, Jianren Fan
Zhejiang University, China

In the field of combustion diagnostics, the simultaneous measurement of velocity and temperature in three
dimensions is desirable for gaining fundamental insights
into the turbulent flames and developing numerical predictive tools. However, such measurements often facechallenges due to the high cost of optical devices, complex calibration procedures, and data acquisition. In thepresent work, for the first time, a novel physics-informed
neural networks (PINNs) framework is established toalleviate the measurement challenges. This framework
enables three-dimensional high-resolution reconstructionof turbulent combustion for velocity, based on two-dimen19th International Conference on Numerical CombustionTrack18 Simulations with AI technologies

sional velocity planes and available three-dimensionaltemperature fields. The performance of the PINNs is evaluated on two different configurations of turbulent flames
without and with a mean shear, including freely propagating planar premixed combustion and swirling combustion.
The reconstructed fields of velocity are compared withthe high-fidelity direct numerical simulation (DNS) data,
and both qualitative and quantitative analyses are performed for the model performance evaluation. This study
highlights the potential of PINNs as a complement for
combustion diagnostics and provide new insights for thedevelopment of physics-informed machine learning methods in combustion research.
Contact: wanghaiou@zju.edu.cn

Multi-Component Temporal Clustering
Analysis in Reaction Phase Space for
Hydrogen Jet Flames
Vansh Sharma1, Shivam Barwey2, Venkat Raman1

University of Michigan, United States, 2Argonne National Laboratory,
United States

1

Worldwide push towards clean energy requires newtechnological pathway and energy carriers. Hydrogen is an
ideal candidate given its high calorific value and reduced
emissions; however, the operational risks are heightened
due to phenomenon like flashback. Detailed numericalinvestigations have revealed complex interaction between
strain effects, caused due to varying flow structures, andflame reaction zones affecting flame stabilization. A data-driven approach to classify different flame branches inreaction phase space for strained hydrogen jet flames is
implemented, and identification of ignition-extinction cyclic pathways on this classification is demonstrated. The
dataset is generated from a reactive jet-in-crossflow simulation, with experimental validation. Each temporal snapshot contains multiple fields like OH, progress variable,
reaction source term etc. Clustering procedure is applied
to the time-evolving dataset and the resulting time-axis
modes are embedded with dynamically similar field variations defined over the selected time interval. Spatially, themodes are discrete and non-overlapping, and a uniquedynamical pattern can be isolated. This presents a clear
interpretation of dominant spatial length-scales and correlations as a function of the isolated dynamical patternrepresented by the corresponding phase space centroid.
The approach improves understanding of localized source
terms under varying strain effects and the associatedflame dynamics.
Contact: vanshs@umich.edu

Unveiling Flame Characteristics for
Combustion Process of Ammonia Blends
using Machine Learning
Aswitha Tadepalli, Richie Shaji Mathew, Raja Banerjee,
Kishalay Mitra
Indian Institute of Technology Hyderabad, India

Direct combustion of ammonia is being actively considered as a carbon neutral fuel. However, due to its low
laminar flame speed and propensity to produce high NOx
emissions, it is generally blended with natural gas andhydrogen to improve its combustion characteristics. Developing a viable combustor using physics-based models
like Computational Fluid Dynamics (CFD) is computationally expensive and finding its optimal operating parameters using such tools is difficult. Therefore, this paper
demonstrates the efficacy of replicating important CFD
results from a surrogate model built using Artificial Neural Network (ANN) based Machine Learning tools. This
CFD model was based on a semi-detailed NH3/H2/CH4/
n-C12H26 mechanism consisting of 242 species and 1769
reactions including both nitrogen oxides (NOx) and sootsub-mechanisms. CFD simulations were performed in theparameter space of blend ratios, operating pressures andmass flux ratios of a jet flame at limited discrete points
following a SOBOL sequence and flame responses are estimated. ANN is utilized to build a surrogate model among
the aforementioned parameters and response variables,
which in turn can predict the frame characteristics for several other unknown operating conditions. This quasi-random low-discrepancy SOBOL sequence not only helps
represent the parameter space uniformly and thereby
requires a minimum number of CFD simulations to identify
the space but also preserves sampling points where simulations have been already performed while creating new
sample points.
Contact: kishalay@che.iith.ac.in

Machine learning implemented large eddy
simulation of turbulent premixed flamesby an AI-assisted fractal dynamic sub-gridscale (FDSGS) model
Yuka Suga, Haruya Shimamoto, Hironobu Minami, Ye
Wang, Mamoru Tanahashi
Tokyo Institute of Technology, Japan

Large eddy simulation (LES) of turbulent premixed
flames which is implemented with machine learning has
been realized with an AI-assisted sub-grid scale (SGS)
combustion model. The AI-assisted SGS combustion
model adopted in this research is developed based on thefractal dynamic SGS (FDSGS) model which was developed193

Track18 Simulations with AI technologies

in our previous research. In the FDSGS model, a model
parameter related to local Kolmogorov length scale isincluded. In the present study, by using fully connectedneural network or fully convolutional network (FCN), it
was shown that local Kolmogorov scale is estimated withhigher accuracy by the machine learning and the prediction of SGS burning velocity is improved through static
tests. The static tests are conducted using direct numerical simulation (DNS) data of freely propagating turbulent premixed flames, turbulent jet premixed flames andturbulent V-shape flames. This AI-assisted FDSGS modelis then implemented on our LES code, realizing the possibility of local Kolmogorov scale estimation with different
combustion configurations such as flame shapes or filter
widths. A dynamic test of the AI-assisted FDSGS model isconducted by LES with machine learning implementation
for turbulent jet premixed flame. It was shown that theprediction of flame surface area and average temperature
distribution by the AI-assisted model is more accurate
than that by conventional SGS combustion models including the non-AI-assisted FDSGS model.

ulation using a 217 reaction model. By leveraging thelarge dimensional compression efficiency of the active
subspace method, offloading the gradient sampling onto
the laminar flamelet simulations, and accelerating computation via a specifically designed neural network, weestimated the uncertain temperature profiles in this turbulent flame with strong 70-85% accuracy using just sevenperturbed solutions. The subspace is identified within the
flamelet table and does not scale in cost with the complexity of the combustion model, indicating promise for
future application to larger-scale and more complex turbulent combustion applications.
Contact: bckoenig@mit.edu

Jacobian-Informed Clustering for SamplePartitioning Adaptive Reduced Chemistry
Methods
Pietro Pagani1, Riccardo Malpica Galassi2, Alessandro
Parente3, Francesco Contino1

Université Catholique de Louvain, Belgium, 2La Sapienza, Italy, 3Université
Libre de Bruxelles, Belgium

1

Contact: iryu.yu03@gmail.com

Track18-4 Simulations with AI
technologies (4)Chair: TBD
Friday, May 10; 09:50 - 11:50; Room D

Kinetic reduction for efficient turbulent
combustion kinetic uncertainty
quantification via active subspace enabled
by neural network
Benjamin Koenig, Sili Deng

Massachusetts Institute of Technology, United States

Propagating uncertainties in kinetic models throughcombustion simulations provides important reliability andaccuracy metrics, but remains challenging and costly especially for large kinetic models and expensive turbulent
simulations. Surrogate model and dimension reduction
techniques were previously applied to facilitate such analysis, but these are often limited to low-dimensional, simple cases with scalar solution targets. Here, we developed
a neural network-accelerated framework for identifying
a low-dimensional active kinetic subspace that can capture the mixture fraction and strain rate effects of kinetic
uncertainty across the entire temperature solution spaceof a flamelet table. We demonstrated the computationalsavings enabled by this framework with a flamelet-based
application in a Reynolds-averaged Sandia Flame D sim-

194

Unsupervised learning methods are gaining prominence in the combustion modeling community for theirability to identify important data patterns, enhancing theefficiency of Reduced Order Models. Traditionally, clustering algorithms rely on the minimization of statisticalmeasures like Euclidean distance or Local PCA-based
reconstruction error (VQPCA), potentially leading to suboptimal solutions for combustion applications.
This study emphasizes the importance of guiding thesolution toward more physics-grounded clusters in thecontext of Adaptive Chemistry Simulations, where identifying locally homogeneous zones is crucial for the model’s
performance. For this aim, we adopt the Jacobian Scaled
K-means clustering formulation (JSK-means) within theeSPARC methodology framework. This clustering algorithm seeks to minimize an objective function modified byscaling matrix cast as the chemical Jacobian at the cluster’s centroid. Such matrix, acting as a linear transformation on the distance vector, ensures that two points, thatare near in the composition space, share similar dynamical characteristics (i.e., similar chemical source terms).
Results show that JSK-means allocates more clusters in
the active thermochemical regions, with respect to VQPCA, to better highlight the source term variations. As aconsequence, the chemistry reduction generates a libraryof more compact local mechanisms resulting in a smaller
average number of species to be solved in CFD.
Contact: pietro.pagani@uclouvain.be

19th International Conference on Numerical CombustionTrack18 Simulations with AI technologies

Deep learning-based chemical kinetic
surrogate model with strictly enforced
conservation laws
Tinghao Wang1, Tianhan Zhang2, Zhi-Qin John Xu3,
Yuxiao Yi3, Junjie Yao3, Zheng Chen1

1
Peking University, China, 2Southern University of Science and Technology,
China, 3Shanghai Jiao Tong University, China

In combustion simulations, the stochastic nature ofartificial neural network (ANN) presents a notable obstacle in upholding physical principles, casting a shadow
over the reliability of data-driven methods. To address
this limitation, we introduce a novel approach called the
Physics-Constrained Neural Network (PCNN) as surrogate
models for chemical source terms. This method strictly enforces predictions to preserve conservation laws,
including mass, energy, and element conservation. The
performance of PCNN with both the original ANN andthe popular physics-informed neural network (PINN) arecompared across various combustion scenarios, including
zero-dimensional autoignition, one-dimensional premixed
laminar flame, two-dimensional triple flame, and outwardly expanding turbulent spherical flame. Our results revealthat small errors of ANN predictions can lead to severe
violations of physical principles because ANN’s statisticaldescription does not contain physical information. Sucherror accumulation in continuous evolutions accounts
for ANN’s non-physical predictions. In contrast, PINN
and PCNN exhibit superior robustness compared to ANN
by incorporating conservation laws. Particularly, PCNN
demonstrates effectiveness in providing stable and accurate predictions by suppressing error accumulation, while
maintaining high computational efficiency. Our study
underscores the critical role of fundamental physical principles in the development and applications of machinelearning based methods.

ics. Despite these efforts, a persistent challenge remains:striking a balance between achieving high-fidelity results
and maintaining low computational costs, especially incases where combustion models involve direct solvingof finite-rate chemistry. This study addresses this challenge by integrating a deep neural network (DNN) intoa GPU-based solver. The focus is primarily on assessing
the effectiveness of the proposed GPU/DNN approachthrough two large eddy simulations of swirling flames. The
simulation outcomes reveal a commendable agreementin flow and flame structures between the GPU/DNN approach and the conventional CPU-based solver with direct
integration (DI). This comparison suggests that the GPU/DNN approach can attain the same level of accuracy as
the conventional CPU/DI solver. Furthermore, the overall
speed-up factor achieved by the GPU/DNN approachexceeds two orders of magnitude. This investigation establishes a potential foundation for fully resolved laboratory-scale flame simulations based on detailed chemistry,offering a considerably more cost-effective computational
solution.
Contact: xwzm@pku.edu.cn

Contact: wth_lk7490@pku.edu.cn

Large eddy simulation of swirling flames:
GPU/DNN-accelerated finite ratechemistry
Min Zhang, Runze Mao, Han Li, Ruixin Yang, Zhi X. Chen
Peking University, China

Swirling flow, renowned for its ability to stabilize leanpremixed turbulent flames, has found extensive application in gas turbines to meet increasingly stringent
low-emission constraints. Numerous numerical simulations, employing various combustion models and meshresolutions, have been undertaken on laboratory-scale
flames to gain deeper insights into swirling flame dynam-195