bluuebunny/crossref_metadata_2025_split huggingface dataset:
Large Eddy Simulation of Soot Formation in a Real Aero-Engine Combustor Using Tabulated Chemistry and a Quadrature-Based Method of Moments
Authors: Koob Philipp , Ferraro Federica , Nicolai Hendrik , Eggels Ruud , Staufer Max , Hasse Christian 
Published: September 2023

Abstract
Considering the increasingly stringent targets for aircraft emissions, CFD is becoming a viable tool for improving future aero-engine combustors. However, predicting pollutant formation remains challenging. In particular, directly solving the evolution of soot particles is numerically expensive. To reduce the computational cost but retain detailed physical modeling, quadrature-based moments methods can be efficiently employed to approximate the particle number density function (NDF). An example is the recently developed split-based extended quadrature method of moments (S-EQMOM), which enables a continuous description of the soot particles’ NDF, essential to consider particle oxidation accurately. This model has shown promising results in laminar premixed flames up to turbulent laboratory scale configurations. However, the application to large-scale applications is still scarce. In this work, the S-EQMOM model is applied to the Rolls-Royce BR710 aero-engine combustor to investigate the soot evolution process in practically relevant configurations. For this, the soot model is embedded into a high-fidelity simulation framework, consisting of large eddy simulation for the turbulent flow and mixing and the flamelet generated manifold method for chemistry reduction. An additional transport equation for polycyclic aromatic hydrocarbons is solved to model their slow chemistry and the transition from the gaseous phase to the solid phase. Simulations are performed for different operating conditions (idle, approach, climb, take-off) to validate the model using experimental data. Subsequently, the results are analyzed to provide insights into the complex interactions of hydrodynamics, mixing, chemistry, and soot formation.
Crossflow Minimization for Jet Impingement Cooling Applications
Authors: Salem Abdel Rahman , Soliman Ibrahim , Amano Ryoichi S. 
Published: September 2023

Abstract
Jet impingement is used to efficiently cool gas turbine blades and other engine components. However, jet-to-jet interactions result in the accumulation of crossflow as the spent air migrates downstream, which usually causes a decay in the Nusselt number and reduces the overall cooling performance. In this study, several crossflow mitigation techniques are investigated by attaching small and easy-to-manufactured crossflow diverters to protect jet cores from upstream crossflows and, therefore, enhance heat transfer performance. Three diverter shapes of cylindrical, rectangular, and ribbed type are studied within a 25-jet array under laminar and turbulent flow regimes (Rej of 2,500–10,000). Three-dimensional Navier-Stokes (N-S) equations are solved under the k-ɛ turbulence model following a mesh sensitivity study. Diverter heights of 25%, 50%, and 75%, as a percentage of jet-to-target spacing denoted as quarter-length (QL), half-length (HL), and three-quarter-length (TQL), respectively, are considered with a constant heat flux condition. Results show an increase in average Nusselt number values from 6.6% to 12% achieved by a TQL cylindrical-shaped diverter. However, the associated friction factor is also increased by 9.9%–24.3% on average compared to the baseline model. Nevertheless, the heat transfer performance parameter (η) is introduced to quantify the desired gain in Nu and the cost in the pressure loss. Consequently, results show a net enhancement of up to 5.2%, 3.1%, and 3.8% for cylindrical, rectangular, and ribbed-type diverters, respectively.
CFD Parameter Studies Using an Actuator Disk to Quantify the Interactions on an Airfoil Segment for Distributed Propulsion
Authors: Kirsch Bastian , Friedrichs Jens 
Published: September 2023

Abstract
In this study, CFD parameter variations are performed to investigate propeller-wing interactions. For this purpose, the solver TAU of the German Aerospace Center with the integrated Actuator Disk is used. The 2.5D setup studied consists of a wing segment with constant chord length and an Actuator Disk iterated to a constant thrust in all cases. The parameters to be varied are: Position, rotational speed, installation angle and segment width. Lift and drag coefficients and propeller efficiencies are used as result variables. It can be seen that the position of the propeller, its installation angle and the spanwise distance between the propellers have significant influence on the interactions. The rotational speed has hardly any influence on the interactions in the considered range. Positions above the wing chord benefit from high lift coefficients, but at the same time drag increases. An exception is the position centrally above the wing, which is characterized by a strong drag reduction in all parameter combinations. Positions above the leading and trailing edge of the wing show also strong sensitivities to the installation angle. Reducing the distance between the propellers amplifies the existing trends, so that advantages are higher, but disadvantages are also more pronounced.
Detailed Gaseous and Particulate Emissions of an Allison 250-C20B Turboshaft Engine
Authors: Rohkamp Marius , Rabl Alexander , Gündling Benedikt , Saraji-Bozorgzad Mohammad Reza , Mull Christopher , Bendl Jan , Neukirchen Carsten , Helcig Christian , Adam Thomas , Gümmer Volker , Hupfer Andreas 
Published: September 2023

Abstract
Aviation is known to be one of the most significant contributors to air pollutants. This includes gaseous emissions, like carbon-dioxide (CO2) and nitrogen oxides (NOx), and also particulate matter (PM), especially in the form of soot. This study conducted emission measurements on an Allison 250-C20B turboshaft engine operating on Jet A-1 fuel with a focus on gaseous compounds (e.g. ozone precursors) and PM, regarding their number and mass concentration. The different engine loading points were chosen based on the percentage thrust ratios of the International Civil Aviation Organization (ICAO) Landing and Take-Off-Cycle (LTO-Cycle). A standard FTIR/O2/FID system to measure general combustion compounds e.g. CO2, carbon-monoxide (CO), unburned hydrocarbons (UHC), and NOx, was used for the gaseous measurements. For the investigation of the volatile organic compounds (VOC), which are known to act as ozone precursors, a gas-chromatograph (GC) was applied. Different measurement methods were used to characterize the PM emissions. For the particle size distribution (PSD), we used two types of electrical mobility analyzers (SMPS and DMS500) and an aerodynamic aerosol classifier (AAC). All measurement systems yielded comparable PSD results, indicating reliable results. The particle measurement methods all show increasing aerosol diameter modes (electrical and aerodynamic) with increased engine loading. The aerosol diameter modes were shifting from 29 nm to 65 nm. Furthermore, the size and shape of different individual particles were evaluated with a scanning electron microscope (SEM). In addition, a correlation between the injection system and the particle formation was established. Gaseous turboshaft engine emissions show high CO and UHC values in Ground Idle (GI) level. NOx levels were the highest at Take-Off (TO) conditions. Acetylene and ethylene were the most significant contributors to ozone formation.
A Numerical Test Rig for Turbomachinery Flows Based on Large Eddy Simulations With a High-Order Discontinuous Galerkin Scheme - Part 3: Secondary Flow Effects
Authors: Morsbach Christian , Bergmann Michael , Tosun Adem , Klose Björn F. , Bechlars Patrick , Kügeler Edmund 
Published: September 2023

Abstract
In this final paper of a three-part series, we apply the numerical test rig based on a high-order Discontinuous Galerkin scheme to the MTU T161 low pressure turbine with diverging end walls at off-design Reynolds number of 90,000, Mach number of 0.6 and inflow angle of 41°. The inflow end wall boundary layers are prescribed in accordance with the experiment. Validation of the setup is shown against recent numerical references and the corresponding experimental data. Additionally, we propose and conduct a purely numerical experiment with upstream bar wake generators at a Strouhal number of 1.25, which is well above what was possible in the experiment. We discuss the flow physics at midspan and in the end wall region and highlight the influence of the wakes from the upstream row on the complex secondary flow system using instantaneous flow visualization, phase averages and modal decomposition techniques.
Gas Concentration Maps Within a Turbomachine Combustor Fueled With Jet-A1 or Sustainable Aviation Fuel (SAF)
Authors: Jarin Jean-Baptiste , Champion-Réaud Jean-Louis , Lambert Pierre-Alain , Mendes Carlos , Jeuland Nicolas , May-Carle Jean-Baptiste , Doucet Clarisse , Picard Florent 
Published: September 2023

Abstract
From July to September 2021, a test campaign was performed by Safran Tech and of the university of Pau E2S (Energy & Environment Solutions lab), on a MAKILA 2B turboshaft (rated 2200 shp). For this purpose, the engine was fueled with a 100% Non-Drop In Sustainable Aviation Fuel (SAF) manufactured by TotalEnergies from Used Cooking Oil (UCO) through the Hydro-Esterification of Fatty Acids process (HEFA). The key objective of this test campaign, which was concluded by a 1st flight realized by Airbus Helicopters on Nov. 9th 2021 [1], was to compare the performance and emissions of CAF (Conventional Aviation Fuel, i.e. regular Jet-A1 manufactured from fossil fuel) and a 100% Sustainable Aviation Fuel on a turboshaft which is a reference in the helicopter industry. The results achieved allow to draw a first comparison. The ground tests concluded to the absence of any major differences in terms of engine performances (Power generation, ignition, lubrication, heat exchange, ...) between SAF and CAF. This was later confirmed by Airbus Helicopters during the flight tests. Tests showed reduced CO2 emissions explained by the higher Hydrogen to Carbon ratio (H/C) of the fuel. A significant reduction of the Smoke Number (SN), −60%, is recorded and explained by the lack of aromatics in the fuel. At this stage, it is not possible to conclude that a total lack of aromatics provides the highest reduction of SN and an optimization could be refined, as proposed by Vamsikrishna Undavalli & al. [2]. This will be further investigated in future research projects by Safran and TotalEnergies.
Study on Aerothermal Performance of a High Temperature VG Turbocharger
Authors: Kitamura Tsuyoshi , Yoshida Kazuki , Danmoto Yosuke , Nakagawa Hiroshi , Hoshi Toru 
Published: September 2023

Abstract
This paper is intended as the evaluation of the aerothermal performance of a high temperature VG (Variable Geometry) turbocharger, which is installed in gasoline engines for small passenger vehicles. The turbine performance with thermal energy loss is discussed through CFD and CHT (Conjugate Heat Transfer) calculations for the VG turbocharger. The CHT calculations with detailed modeling of a VG turbocharger were executed to acquire the whole thermal and flow field accurately. Heat flow from the turbine section to the bearing housing with water cooling has also been simulated.
In addition, the bench tests for the VG turbocharger were conducted to validate the CHT calculations. Analytical results provided good agreement with experimental data. Eventually, the performance degradation induced by thermal energy loss has been evaluated.
Computational Fluid Dynamics in a Fan-Drive Gear System of an Aeroengine
Authors: Hashimoto Hironori , Arisawa Hidenori , Kondo Koki , Shinoda Yuji , Tanaka Mitsuaki , Imai Hideyuki , Fujii Isao , Nishida Takunobu 
Published: September 2023

Abstract
To reduce fuel consumption of aeroengines, gearing of engines has become a trend. In geared engines, a design based on the elucidation of phenomena is necessary to achieve both high efficiency and reliability. Therefore, computational fluid dynamics (CFD) can contribute effectively to optimize its design. However, to our knowledge, examples of numerical simulation of high-speed gas-liquid two-phase flow in a planetary gear system, including multiple gear meshes and structures for oil capture, are not available in literature.
Therefore, in this study, a numerical simulation method, previously developed by our research team, was used for a planetary gear system. The key feature of our numerical simulation method is that it realizes fast and numerically stable calculations by using the volume of fluid (VOF) method and surface compression scheme for the air-liquid interface, and the porosity method for the object boundary.
To validate the accuracy of the numerical simulation method used, a planetary gear system with specifications equivalent to those of an aeroengine gear system was used. The numerical simulation and experimental test results obtained were then compared for fluid dynamic loss and oil capture flow rate. From this comparison, it was confirmed that the numerical simulation method used has a practically acceptable accuracy.
The effects of the shape of the oil capture structure on the fluid dynamic loss and oil capture flow rate were investigated using our numerical simulation. The relationship between air flow, oil flow, and fluid dynamic loss, as well as the relationship with the oil capture flow rate were then discussed.
Gradient-Free Aerodynamic Optimization With Structural Constraints and Surge Line Control for Radial Compressor Stage
Authors: Schaffrath Robert , Nicke Eberhard , Forsthofer Nicolai , Kunc Oliver , Voß Christian 
Published: September 2023

Abstract
The concept and design of High Temperature Heat Pumps (HTHP) including their components for specific temperature needs is a time consuming and interdisciplinary task. Especially, the design of compressor geometries has a big impact on the overall performance and the initial costs of the system. For this reasoning, in this work an automated aerodynamic gradient-free optimization including structural constraints for the geometry of a radial compressor impeller blade as well as diffusor vane geometry for water steam, that is applied in a reverse Rankine cycle based HTHP, is presented. Objective of the optimization is the isentropic efficiency in the aerodynamic design point (ADP) of the compressor. Constraints for the pressure ratio, mass flow rate and limits for stresses in blade and disk geometry satisfy requirements of the cycle simulation of the whole HTHP system and structural needs. The optimization method is based on evolutionary algorithms and stochastical surrogate models. Additionally, a highly throttled operating point is regarded to achieve an acceptable distance to the surge line. These types of optimization problems are often characterized by lots of unconverged iterations due to unstable computational fluid dynamic simulations (CFD). To encounter this, a study of the optimization process with different surrogate models is presented. The results are discussed with respect to convergence history as well as objective and constraint improvement.
Friction Saturated Limit Cycle Oscillations – Test Rig Design and Validation of Numerical Prediction Methods
Authors: Schwarz Stefan , Reil Johannes , Gross Johann , Hartung Andreas , Rittinger David , Krack Malte 
Published: September 2023

Abstract
In this paper, an experimental test rig for friction saturated limit cycle oscillations is proposed to provide a validation basis for corresponding numerical methods. Having in mind the application of turbine blades, an instrumented beam-like structure equipped with an adjustable velocity feedback loop and dry frictional contacts is designed and investigated. After dimensioning the test rig by means of a simplified one dimensional beam model and time domain simulations, the specific requirements of limit cycle oscillations for the design of the frictional contact, the velocity feedback loop and the excitation system are discussed and possible solutions are presented. Also appropriate measuring principles and evaluation techniques are assessed. After commissioning of the test rig, the influence of the negative damping and the normal contact force on the limit cycle oscillations is measured and the practical stability is investigated. The test rig shows linear dynamics for sticking contact and highly repeatable limit cycles. The measured results are discussed regarding the consistency with theory and compared to the predictions of a three dimensional reduced order model solved in frequency domain by the harmonic balance solver OrAgL. It is demonstrated that the numerical modeling strategy is able to accurately reproduce the measured limit cycle oscillations, which stabilized for different contact normal forces and self-excitation levels.
Wind-Turbine Inspection, Maintenance and Repair Robotic System
Authors: Cieslak Chris , Shah Aksat , Clark Brodie , Childs Peter 
Published: September 2023

Abstract
World-wide wind energy capacity continues to grow with 1870 TW h in 2021, with annual additions of 113 GW in 2020 and 59 GW in 2019 with over 90% of the growth as a result of offshore wind farm installations. To attain 2050 net zero targets annual capacity additions of 250 GW are expected. Wind turbine assets require regular inspection and maintenance to ensure performance, compliance to standards and insurance requirements. A range of approaches are used in inspection and maintenance including airborne and platform mounted technologies, robots, as well as accessing the blades directly with rope assisted technicians. In addition to reviewing the merits and challenges associated with a range of approaches to offshore horizontal axis wind turbine maintenance this paper describes the design, trialling and in-service operation of a hexapod robot, along with options for its deployment. The robot is capable of deploying a wide range of measuring equipment and maintenance tools. The hexapod gait employed enables the chassis to be an end-effector, avoiding the use of traditional robot arms and the multiple degrees of freedom associated with the robot legs enable the robot to walk on both convex and concave surfaces as well as straddle a leading-edge profile on a wind turbine aerofoil. The robots have demonstrated functionality through multiple blade walks and tasks such as lightning protection system verification, inspections and blade surface treatments. The robot has the capability to work independently or alongside rope-assisted technicians.
Evaluation of Cooling Requirements for Rotating Detonation Combustors
Authors: Sandri Umberto , Ramanagar Sridhara Shreyas , Andreini Antonio , Bohon Myles D. , Picchi Alessio , Facchini Bruno 
Published: September 2023

Abstract
In the last decade, the Rotating Detonation Combustor (RDC) has received growing attention among the different Pressure Gain Combustion concepts due to the simplicity of the design and the potential ease of integration in gas turbines. However, multiple technological challenges are still associated with its development. Researchers have pointed out concerns related to the heat loads determined by the high temperature and the complex flow field occurring in this kind of combustion chamber based on a small but meaningful set of experimental and numerical results. An investigation of the open literature has shown a strong sensitivity of the heat loads with multiple designs and operational parameters. The aim of this work is to provide a fundamental review of the primary drivers affecting heat load in a typical RDC in order to define basic cooling requirements for possible actual design of the combustor. Along with this, a simplified approach has been implemented for the estimation of the requirements for cold side convection cooling with respect to different heat load scenarios, shedding light on the compatibility of pure convection cooling for Rotating Detonation Combustors. Finally, the results are used to determine guidelines for the design of a cooled and efficient RDC.
Aerodynamics and Aeroacoustics of Leading Edge Serration in Low-Speed Axial Fans With Forward Skewed Blades
Authors: Tieghi Lorenzo , Czwielong Felix , Barnabei Valerio F. , Ocker Cristof , Delibra Giovanni , Becker Stefan , Corsini Alessandro 
Published: September 2023

Abstract
Low-speed axial fans must comply with a wide number of standards and normative restrictions, often related to the maximum noise emission levels. Among the noise control techniques in axial fans, skewed fan blades and leading edge (LE) serrations have been found to be effective in LE noise control, which represents one of the dominant phenomena in axial fan broadband emissions. However, these solutions are usually applied separately, and literture is scarce on systematic studies on the coupling of the two modifications. In this work, a campaign of experimental measurements was conducted on unskewed and forward-skewed axial fan blades with and without leading-edge serrtions. The tests were performed in undisturbed inflow conditions. The flow field and the turbulence characteristics were measured using 3D hot-wire anemometry. The suction-side sound radiation of the fans was measured with microphones in an anechoic chamber. In addition, the rotating beamforming method was used to localize the sound sources at the axial fans. It was found that, regardless of the blade skew, the leading edge serrations lead to a reduction of the sound pressure level, whereby the aerodynamic properties of the fan decrease. At the same operating points, which were achieved by adjusting the rotational speed, the sound radiation through the leading edge serrations could be reduced at high-volume flows. This effect was more pronounced with the unskewed rotor, which indicates that the positive effect of the serrations is reduced by the already optimized shape of the forward skewed fan blade. Based on the experimental results, the four geometries were further considered for numerical investigations to understand how the serrations affect the fan operations and the overall aerodynamics of the rotor. All four geometries were simulated with RANS approach at the duty point to derive a flow survey and better understand the dynamics driven by serrations and blade skewing.