bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impact of Hydrogen Addition on the Thermoacoustic Instability and Precessing Vortex Core Dynamics in a CH4/H2/air Technically Premixed Combustor
Authors: Datta Anindya , Gupta Saarthak , Hemchandra Santosh , Chterev Ianko , Boxx Isaac 
Published: September 2021

Abstract
We study the impact of H2 enrichment on the unsteady flow dynamics and thermoacoustic instability in the single nozzle PRECCINSTA swirl combustor. We analyze data from two operating modes, premixed (PM) and technically premixed (TPM). The experiments were performed at atmospheric conditions with H2/CH4 fuel mixtures at a global equivalence ratio of 0.65 while maintaining a constant thermal power of 20 kW. We examine the effect of H2 addition on the flow dynamics by analyzing cases with three fuel compositions: 0% H2, 20% H2 and 50% H2 in both operating modes. A new multi resolution modal decomposition method, using a combination of wavelet transforms and proper orthogonal decomposition (WPOD) of the experimental time resolved high speed flow velocity and OH-PLIF measurements is performed. Thermoacoustic oscillations are observed in the TPM operating mode alone. WPOD results for the 0% H2 TPM operating mode case reveals intermittent helical PVC oscillations along with axi-symmetric hydrodynamic flow oscillations due to the thermoacoustic oscillation. These oscillations cause local flame extinction near the nozzle centrebody resulting in liftoff. A precessing vortex core (PVC) oscillation develops in the flow that enables intermittent flame reattachment and results in intermittent thermoacoustic oscillations in this case. In the 0% H2 PM case, the flame remains lifted off of the centrebody despite the presence of PVC oscillations in this case as well. H2 enrichment results in the suppression of flame lift-off and the PVC in both operating modes. We show from flow strain rate statistics and extinction strain rate calculations that the increase of the latter with H2 addition, allows the flame to stabilize in the region near the centrebody where the pure CH4 cases show lift off. The lack of thermoacoustic oscillations in the PM operating mode shows that the primary heat release driving mechanism is due to fuel-air ratio oscillation that the thermoacoustic oscillation generates. The time averaged flow fields and the emergence of the PVC when the flame is lifted off, together suggest that PVC oscillations are caused by the separation between the vortex breakdown bubble and the wake behind the centrebody, as suggested by prior computational studies.
Performance Evaluation of Leading Edge Tubercles Applied to the Blades in a 2-D Compressor Cascade
Authors: Sidhu Satpreet S. , Asghar Asad , Allan William D. E. 
Published: September 2021

Abstract
In the present paper, the performance of compressor blades modified with leading edge tubercles was evaluated and compared with that of a baseline profile at a high subsonic Mach number in a 2-D cascade. Specific tubercle geometries were selected based on an extensive literature survey and a Self-Organizing Map analysis. The compressor blade geometry of a popular aero-engine was reverse-engineered using laser-scanning. Baseline and tubercled compressor blades were 3-D printed and tested. Two sinusoidal tubercle shapes based on different amplitudes and wavelengths and one with a power law profile were selected. A 2-D compressor cascade was designed and commissioned to test these blades at high subsonic Mach number in the transonic wind tunnel at Royal Military College of Canada. Surface flow visualizations were performed with oil for observing and locating compressor blade stall for different sets of blades. Flow direction and the total pressure at the cascade exit were measured using a 5-hole, fast-response, traversing probe. Compressor blade performance was measured and compared with various tubercled blades at various angles of incidence, while maintaining periodicity at the inlet and exit planes. Total pressure loss coefficients were calculated for all 4 blades and compared for 6 positive angle of incidence. Power series tubercled profile resulted in slight improvements in the loss coefficient at 0° incidence and none of tubercled geometry compromized performance at the design point. The baseline blade stalled at 8° and tubercles were capable of delaying stall at this condition. Power series profile outperformed the baseline at all angle of incidence (AOI) with significant improvements at 8° AOI. Power series tubercled profiles performed better than other tubercled geometries at almost all AOI except 10° where sinusoidal tubercled profiles performed better. The presence of smaller valley and broader peaks is attributed with the performance improvement, supported by the flow visualization results.
Carbon and Hydrocarbon Particle Seeding in Air-Breathing Rotating Detonation Engine
Authors: Burke Robert , Rezzag Taha , Ahmed Kareem A. 
Published: September 2021

Abstract
Within the power generation community, the rotating detonation engine (RDE) is only growing in popularity with its increased performance, simple mechanism, and operation. Although significant testing is underway to characterize the RDE for integration with conventional gas turbines, this entire system is still at a relatively low technology readiness level. In the midst of RDE research, there is an initiative to understand solid particle seeding effects in the detonation performance. Under investigation at the University of Central Florida is a Department of Energy (DOE) 6-inch RDE, with a solid particle seeder in parallel with its H2 and air flow lines. Previous work on this system involved carbon particle detonation; however, the tested particles were taken one step further to include more sustainable, greener hydrocarbon particles. Testing of powdered sugar, peanut flour, and cornstarch, along with previous carbon black tests have shown not only successful detonability, but a noticeable effect on the detonation wave dynamics. Side-by-side with a particle burning model being developed, an operational map can be determined for the hydrocarbon particles particularly, which can be tuned with the local flow conditions to achieve peak operability while replacing fuels with sustainable alternatives that could even be grown.
Design and Flow Analysis of a Rim-Driven Hub-Less Axial Flow Fan
Authors: Yang Hanqing , Wang Yijun , Sun Jinju , Wang Bangyi , He Youwei , Song Peng 
Published: September 2021

Abstract
Rim-driven hub-less fans have newly emerged as the most compact type of axial flow fans, which permits flexible configuration arrangements, large relative flow area and low-noise level operation. However, previous publications on rim-driven axial flow fans are rarely found in the open literature, and the flow mechanism and design principle of such promising fans haven’t yet been well-understood and established. This paper has been focused on a preliminary study of the rim-driven axial flow fan design and flow mechanism. A design method of the rim-driven fans is proposed on the basis of the isolated airfoil scheme and the variable circulation rule. It is further incorporated into a FORTRAN code and suited for designing the rim-driven hub-less fans of low-pressure levels.
For validation purpose, a conventional hub-type fan is redesigned with the developed method and its flow behavior and overall performance are investigated numerically. A parametric study on the designed fan is further conducted respectively for the tangential velocity difference at mean span, circulation exponent and sweep angle and their influence on the fan flow characteristics and overall performance are explored and highlighted. On such a basis, the developed design method for the rim-driven axial flow fan is further improved. In comparison with the conventionally designed fan at identical rotating speed, significant comprehensive gains are arising from the redesigned fan of hub-less configuration: the overall pressure rise and static pressure efficiency is enhanced respectively by 6.2% and 11.5%, whereas the diameter of the fan is reduced by 12.5% simultaneously. It is demonstrated that the rim-driven hub-less configuration is promising for the enhancing the fan overall performance with even reduced dimensions.
Fan-Intake Coupling With Conventional and Short Intakes
Authors: Gunn E. J. , Brandvik T. , Wilson M. J. 
Published: September 2021

Abstract
The current trend in civil engine fans towards lower pressure ratio and larger diameter is accompanied by a need to shorten the engine intake length to reduce weight and drag. This paper uses full-annulus, unsteady CFD simulations of two coupled fan-intake configurations to explain the impact of flow field coupling and intake length on fan and intake performance. On-design and off-design operating points are considered at cruise and high angle of attack, respectively.
The fan efficiency at cruise is shown to be determined by a trade-off between two effects. Cruise efficiency is reduced by 0.11% with a short intake due to increased potential flow field distortion, which alters the incidence and diffusion of the rotor. This is partially offset by a reduction in casing boundary layer thickness due to lower intake wetted area.
At high angle of attack conditions, a short intake leads to increased potential flow field distortion and an earlier onset of intake flow separation due to a higher adverse pressure gradient approaching the fan. Both effects combine to reduce the fan thrust at such conditions, although the fan is shown to remain stable at attack angles up to 35°. The reduction in performance is shown to be dominated by flow separations in the rotor, which increase in size and severity for a given attack angle as the intake length is decreased. The fan is also shown to have a stronger influence on the form of the intake flow field in a short intake, suggesting that it is necessary to model the fan in the intake design process for a successful design.
Modal Decomposition and Linear Modeling of Swirl Fluctuations in the Mixing Section of a Model Combustor Based on PIV Data
Authors: Müller Jens Satria , Lückoff Finn , Kaiser Thomas Ludwig , Paschereit Christian Oliver , Oberleithner Kilian 
Published: September 2021

Abstract
In order to determine the flame transfer function of a combustion system only based on isothermal flow field data, three governing mechanisms have been identified which need to be modeled: swirl fluctuations, equivalence fluctuations and velocity fluctuations excited by planar acoustic waves. This study focuses on the generation and propagation of swirl fluctuations downstream of a radial swirl combustor under isothermal conditions. Swirl fluctuations are generated experimentally by imposing acoustic perturbations. Time-resolved longitudinal and crosswise PIV measurements are conducted inside the mixing tube and combustion chamber to quantify the evolution of the swirl fluctuations. The measured flow response is decomposed using spectral proper orthogonal decomposition to unravel the contributions of different dynamical modes. In addition a resolvent analysis is conducted based on the linearized Navier-Stokes equations to reveal the intrinsically most amplified flow structures. Both, the data-driven and analytic approach, show that inertial waves are indeed present in the flow response and an inherent flow instability downstream of the swirler, which confirms the recent theoretical work of Albayrak et al. (Journal of Fluid Mechanics, 879). However, the contribution of these inertial waves to the total swirl fluctuations turns out to be very small. This is suggested to be due to the very structured forcing at the swirler and the amplification of shear-driven modes which are expected to be much more influential for this type of swirler. Overall, this work confirms the presence of inertial waves in highly turbulent swirl combustors and evaluates its relevance for industry-related configurations. It further outlines a methodology to analyze and predict their characteristics based on mean fields only, which is applicable for complex geometries of industrial relevance.
Surrogate Models for the Prediction of Damping Ratios in Coupled Acoustoelastic Rotor-Cavity Systems
Authors: Heinrich Christoph Rocky , Unglaube Tina , Beirow Bernd , Brillert Dieter , Steff Klaus , Petry Nico 
Published: September 2021

Abstract
Centrifugal compressors are versatile machines that many industries employ for a wide range of different applications, including the production of highly compressed gases. During the last decades, comprehensive research was conducted on the impact of high-pressure operating conditions on the vibrational behavior of radial compressors. In various studies, acoustic modes building up in the side cavities were found to be a potential source of high cycle fatigue. Nowadays, it is well-known that an increase in gas pressure levels leads to a more pronounced fluid-structure interaction between the side cavities and the impeller resulting in a frequency shift of the acoustic and structural modes. In a recently published paper, the authors presented a generalized model which can predict this behavior. As it is not always possible to avoid operating close to or accelerating through a resonance, it is crucial to know the damping present within the system. Currently, only a few publications concentrate on the damping of radial impellers. Therefore, the authors present measurement data acquired from a test rig at the University of Duisburg-Essen, which reveals the damping behavior of a disk under varying operating conditions. Two surrogate models are proposed to predict the identified damping behavior. The first one is based solely on a one-dimensional piston model and the second approach uses an enhanced version of the generalized method. Finally, the measurement data is used to validate both surrogate systems.
Aerodynamic Optimization of a Turbocharger Unit Based on the Overall Efficiency Enhancement of an Internal Combustion Engine for Stationary Power Production
Authors: Catalani Iacopo , Agnolucci Andrea , Balduzzi Francesco , Bianchini Alessandro , Arnone Andrea , Ferrara Giovanni , Vichi Giovanni , Bellissima Alessandro , Minamino Ryota , Asai Go 
Published: September 2021

Abstract
In case of stationary power production, the matching between the turbocharger and the engine can be optimized around a specific operating point, rather than throughout a wide range like in automotive applications. This, in turn, may enable a finer optimization of the aerodynamic efficiency in comparison to existing industrial standards.
The present study then reports a joint research activity aimed at defining an integrated approach to optimize the overall performance of an engine for stationary power production via a dedicated optimization of the turbocharger unit. In further detail, the aerodynamic optimization of the compressor, the turbine and the static parts is carried out by means of high-fidelity CFD simulations, while a 1D model of the powertrain is realized by means of the GT-Power software. An iterative procedure between the two simulation frameworks is established to account for the fluid dynamic connection between the engine and the turbocharger. Even though the selected case study was a “high quality” commercial product, the study shows how notable aerodynamic improvements can be achieved on turbocharger aerodynamics, thanks to the fact that the rangeability can be narrowed. Efficiency increases of 2.4% and of 3.4% have been reached for the compressor and the turbine, respectively. In the selected case study, this reflected into a moderate overall engine improvement (+0.5%), which however is not negligible in case of engine for stationary power production. Anyhow, the results suggest more promising prospects in case the methodology is applied since the early design of the engine.
Accurate Inlet Boundary Conditions to Capture Combustion Chamber and Turbine Coupling With Large-Eddy Simulation
Authors: Martin Benjamin , Duchaine Florent , Gicquel Laurent , Odier Nicolas , Dombard Jérôme 
Published: September 2021

Abstract
The coupling between different components of a turbomachinery is becoming more widely studied especially by use of Computational Fluid Dynamics. Such simulations are of particular interest especially at the interface between a combustion chamber and a turbine, for which the prediction of the migration of hotspots generated in the chamber is of paramount importance for performance and life-duration issues. Despite this need for fully integrated simulations, typical turbomachinery simulations however often only consider isolated components with either time-averaged constant value, radial profile or least frequently 2D maps imposed at their inlet boundaries preventing any accurate two-way coupling. The objective of the present study is to investigate available solutions to perform isolated simulations while taking into account the effect of multi-component coupling. Investigations presented in the paper focus on the FACTOR configuration. The fist step of the proposed method is to record conservative variables solved by the LES code at the interface plane between the chamber and the turbine of a reference simulation. Then, using the Spectral Proper Orthogonal Decomposition (SPOD) method, the recorded data is analysed and can be partially reconstructed using different numbers of frequencies. Using the partial reconstructions, it is then possible to replicate a realistic inlet boundary condition for isolated turbine simulations with both velocity and temperature fluctuations, while reducing the storage cost compared to the initial database. The integrated simulation is then compared to the isolated simulations as well as against simulations making use of averaged quantities with or without synthetic turbulence injection at their inlet. The isolated simulations for which the inlet condition is reconstructed with a large number of frequencies show very good agreement with the fully integrated simulation compared to the typical isolated simulation using average quantities at the inlet. As expected, decreasing the number of frequencies in the reconstructed signal deteriorates the accuracy of the resulting signal compared to the full recorded database. However, isolated simulations with a low number of frequencies still perform better than standard boundary conditions, especially from an aero-thermal point of view.
Optimized Performance and Cost Potential for Indirect Supercritical CO2 Coal Fired Power Plants
Authors: Pidaparti Sandeep R. , White Charles W. , Weiland Nathan T. 
Published: September 2021

Abstract
Indirect-fired supercritical CO2 (sCO2) power cycles are being explored as an attractive alternative to steam Rankine cycles for a variety of heat sources including fossil, concentrated solar power (CSP), nuclear, waste heat etc. Therefore, understanding their performance and cost potential is important for commercialization of the technology. This study presents the techno-economic global optimization results of coal-fired utility scale power plants based on indirect sCO2 power cycles with and without carbon capture and storage (CCS). Four power cycle configurations are considered for optimization – recompression cycle (RC) with and without turbine reheat and partial cooling cycle (PCC) with and without turbine reheat. Several design variables are identified for each power cycle configuration and these design variables are optimized to minimize the levelized cost of electricity (LCOE) for each plant. The optimization design variables included parameters such as turbine inlet temperatures and pressure, sCO2 cooler outlet temperatures, recuperator approach temperatures and pressure drops etc. The optimization is conducted using automated derivative free optimization algorithms available under NETL’s Framework for Optimization and Quantification of Uncertainty and Sensitivity (FOQUS) platform.
For sCO2 power plants both with and without CCS, recompression cycle with reheat (RC with reheat) has the highest plant efficiency and lowest LCOE among the considered power cycle configurations. For plants with CCS, the RC with reheat configuration offered 8 percentage points higher plant efficiency (HHV basis) and 14.6% lower LCOE compared to a state-of-the-art (SOA) PC-fired supercritical steam Rankine plant with CCS. For plants without CCS, the RC with reheat configuration offered 4.7 percentage points higher plant efficiency and 7% lower LCOE compared to a SOA PC-fired supercritical steam Rankine plant without CCS.
Laminar Flame Speed Measurements of Hydrogen/Natural Gas Mixtures for Gas Turbine Applications
Authors: Kim Gihun , Ghorpade Ritesh , Vasu Subith S. 
Published: September 2021

Abstract
Due to the increasingly challenging carbon emission reduction targets, hydrogen-containing fuel combustion is gaining the energy community’s attention, as highlighted recently in the U.S. Department of Energy’s (DOE) Hydrogen Program Plan [1]. Though fundamental and applied research of hydrogen-containing fuels has been a topic of research for several decades, there are knowledge-gaps and unexplored fuel blend combustion characteristics at conditions relevant to modern gas turbine combustors. Hydrogen will be burned directly or as mixtures with natural gas (NG) and/or ammonia (NH3) in these devices. Fundamental research on the combustion of hydrogen (H2) containing fuels is still essential, especially to overcome or accurately predict challenges such as nitrogen oxides (NOx) reduction and flashback and develop fuel flexible combustors for a prosperous hydrogen economy. We focused our investigation on a natural gas and hydrogen mixture. Measurements of laminar burning velocity (LBV) are necessary for these fuels to understand their applicability in the turbines and other engines. In this study, the maximum rate of pressure rise and LBV of methane (CH4), CH4/H2, natural gas, and natural gas/H2 mixture were measured in synthetic air. The experimental conditions were at an initial pressure of 1 atm and an initial temperature of 300 K. A realistic natural gas composition from the field was used in this study and consisted of CH4 and other alkanes. The experimental data were compared with simulations carried out with detailed chemical kinetic mechanisms.
Unsteady Film Cooling Performance on the High Pressure Turbine Shroud Under Rotor-Stator Interaction for an Aero-Engine
Authors: Bao Zihao , Kou Zhihai , Han Bo , Li Guangchao 
Published: September 2021

Abstract
The turbine rotor inlet temperature of modern aero-engines has continuously increased in order to achieve higher thrust-to-weight ratio and thermal efficiency, which requires higher cooling effectiveness for turbine components. The turbine shroud is exposed to the blade tip leakage flow, and has become a common limiting factor for the turbine stage of advanced aero-engines. The three-dimensional numerical simulation on the unsteady film cooling characteristics of the high-pressure turbine shroud for an aero-engine under the rotor-stator interaction and the high blade rotation speed was conducted. The sliding grid technology was used to realize the relative movement between the turbine blade and the turbine shroud, and the rotor-stator interaction. Effects of the blade rotation, blowing ratios and the film jet direction on the unsteady film cooling performance of the high-pressure turbine shroud were revealed. It is found that the film cooling characteristics of the turbine shroud present an unsteady and periodic phenomenon. The blade tip clearance leakage flow, leakage vortex and mainstream suppression have important effects on the film cooling performance of the high-pressure turbine shroud. More attention should be paid to the insufficient cooling margin of the front row film holes due to coolant jet liftoff from the shroud surface under the high blowing ratio.