bluuebunny/crossref_metadata_2025_split huggingface dataset:
Scale-Resolving Simulations of Turbulent Flow Retaining The Exact Blade Count With the Time-Inclined Method
Authors: Montiel Miguel , Corral Roque 
Published: August 2024

Abstract
Simulations of the T106 low-pressure turbine linear cascade with incoming wakes have been conducted to demonstrate the suitability of the time-inclined method for retaining the exact blade count in scale-resolving simulations. The time-inclined method has been implemented into a high-order unstructured time-marching code based on the flux-reconstruction method. The pitch ratio between the upstream incoming wakes and the cascade is not a small integer, and the time-inclined method is used to reduce the simulations to a single-passage computational domain. Three-way comparisons have been generated: the solution of the direct periodic full domain, spanning several blade passages, is compared to the single-passage time-inclined solution and to a single-passage solution that approximates the pitch ratio to the nearest integer. Two sets of virtual experiments, which differ in modelling of the incoming perturbations, are reported. Firstly, the immersed boundary approach is used to introduce a cascade of moving bars that act as the trailing edges of the preceding row and generate incoming wakes. The second set of simulations introduces wake-like perturbations at the inlet section of the computational domain. The present work shows that the time-inclined method, retaining the exact blade count, can produce very accurate results for turbulence-resolving simulations. Moreover, the time-inclined method outperforms the standard single-passage methodology in most of the variables of interest and is equivalent in the rest.
Design and Simulation of eVTOL Aircraft Thermal Management System
Authors: Kang Sangkeun , Saias Chana , Roumeliotis Ioannis , Broca Olivier 
Published: August 2024

Abstract
This paper focused on designing a Thermal Management System (TMS) for a parallel hybrid electric XV-15 tiltrotor aircraft used in Urban Air Mobility applications. The TMS is integrated into the aircraft system to assess its impact at aircraft and mission levels. Both liquid cooling and air-cooling TMS, along with using Phase Change Materials (PCMs) for heat storage, were designed and assessed. Two liquid-cooling configurations, series and parallel, were evaluated, with the series configuration proving more effective in the considered test cases. The study compared hover and cruise conditions to determine optimal design point for the liquid-cooling TMS. Designing for hover resulted in about fourfold increase in the TMS penalty in fuel burn during cruise. Designing for cruise, on the other hand, proved infeasible to comply with the thermal management requirements during hover. Two approaches were explored to address this: Approach A involves adding PCMs as a heat storage system, and Approach B entailed redesigning the TMS with the heat load at off-design conditions for the inverter and motor. Both approaches resulted in a 24% and 46% increase in the TMS penalty in fuel burn compared to the design that solely considering cruise condition, respectively. The assessment of the designed aircraft systems, integrating the TMS for the considered test cases, revealed that the liquid-cooling TMS designed at cruise condition with Approach B emerged as the optimal design, showcasing a 42% improvement in fuel burnt per payload compared to the air-cooling TMS at the mission level.
Adjoint Based Shape Optimization for Thermoacoustic Stability of Combustors Using Free Form Deformation
Authors: Ekici Ekrem , Juniper Matthew P. 
Published: August 2024

Abstract
We use the thermoacoustic Helmholtz equation to model thermoacoustic oscillations as an eigenvalue problem. We solve this with a Finite Element method. We parameterize the geometry of an annular combustor geometry using Free Form Deformation (FFD). We then use the FFD geometry, define the system parameters and impose the acoustic boundary conditions to calculate the eigenvalue and eigenvector of the problem using a Helmholtz solver. We then use adjoint methods to calculate the shape derivatives of the unstable eigenvalue with respect to the FFD control points. According to these gradients, we propose modifications to the control points that reduce the growth rate. We first demonstrate the application of this approach on the Rijke tube. Then we extend the method to a simulation of a laboratory combustor and lower the growth rate of the unstable circumferential mode. These findings show how this method could be used to reduce combustion instability in industrial annular combustors through geometric modifications.
Aerodynamic Performance of Partially Variable Geometry High-Pressure Turbine
Authors: You Lyu , Dong Xuezhi , Liu Xiyang , Tan Chunqing 
Published: August 2024

Abstract
Variable geometry turbine (VGT) technology changes the throat width of turbine guide vane to control the mass flow rate and adjust the operating condition of engine. With the development of variable cycle engine, the demand for VGT technology is getting urgent. In order to overcome the technical difficulties of current VGT technology, including large tip leakage and low adjustment accuracy, the partially variable geometry turbine (partially VGT) is considered as an alternative solution. Based on the original design of the General Electric Energy Efficient Engine (E3) high pressure turbine, this paper introduces a new structure with half vanes fixed and the other half adjustable. Numerical simulation and theoretical analysis are applied to investigate the effect of partially VGT on the aerodynamic performance of the high-pressure turbine. The results show that: 1) Within the required mass flow range, partially VGT can achieve a larger rotation angle of the guide vane. The guide vane throat width is linearly related to the setting angle, ensuring the accuracy of regulation. 2) Partially VGT has no significant variation with VGT in the fluid mechanism and distribution of the outlet section parameters. 3) Partially VGT can also play a role in controlling turbine power distribution. The above conclusions show that the partially VGT analyzed in this paper can replace the conventional VGT, which will provide a reference for the research on VGT technology.
Centrifugal Compressor Design Parameters Assessment for Hydrogen Compression
Authors: Aleksandrov Andrei , Jaatinen-Värri Ahti , Uusitalo Antti , Turunen-Saaresti Teemu 
Published: August 2024

Abstract
In recent years, hydrogen has gained a lot of interest, and it is considered as one part in the transition towards cleaner energy systems. With global hydrogen production increasing, the demand for hydrogen compression for storage and transportation has been increasing as well. The low molar mass of hydrogen creates challenges for compression, requiring higher enthalpy increase for the same pressure ratio compared to heavier gases. This, in turn, increases the required velocity which is limited by the compressor rotor material.
This paper aims to explore the initial design parameters of a hydrogen centrifugal compressor. A 1D design model was used to assess the loss distributions with varying initial design parameters. The most significant losses were analyzed and compared between hydrogen and air as working fluids. The results indicate that the velocity ratio and the de Haller number have more effect on the losses than hub-to-tip diameter ratio, with the de Haller number being the most important. The minimum total losses with hydrogen occur at much lower de Haller numbers than with air, therefore a hydrogen compressor would benefit more from utilizing low de Haller number compared to an air compressor.
Unsteady Flow Development and Reynolds Stress Measurements in a Centrifugal Compressor Vaned Diffuser
Authors: Meier Matthew A. , Gooding William J. , Key Nicole L. 
Published: August 2024

Abstract
Modern aeroengine designers face the challenge of reducing fuel consumption, which is pushing compressor technology into new design spaces. To optimize these design spaces, high-fidelity computational models are crucial to the compressor design process. It is important to validate these models with experimental data. Non-intrusive measurement techniques allow for acquisition of data well suited for this comparison, as they do not lead to local disruptions of the flow field.
This investigation utilized three-component laser Doppler velocimetry to acquire a unique dataset of detailed unsteady velocity measurements in the vaned diffuser of an aeroengine centrifugal compressor. These measurements allowed for a thorough study of the flow development in the vaneless & semi-vaneless space of the diffuser as well as through the diffuser passage. The components of the Reynolds stress tensor were also determined at multiple locations in the diffuser flow field. These data are used to study the jet and wake propagation from the impeller exit flow field into the diffuser passage and the resulting secondary flow structures.
Predictions from unsteady CFD simulations using the SST and BSL-EARSM turbulence models are also compared with these experimental data. Both turbulence models yielded results that qualitatively agreed with the experimental radial velocity profile through the vaneless and semi-vaneless space. With the experimentally determined Reynolds stress tensor, the turbulent kinetic energy (TKE) is calculated at multiple points through the flow field and is compared to the TKE at the same geometric locations in the computational flow field. This comparison highlights the difference in dissipation and production of turbulence between the experimental data and the computational predictions. Investigating the differences in TKE throughout the diffuser helps elucidate the differences in predicted flow structures in the diffuser passage.
Large Eddy Simulation of Ammonia-Hydrogen Non-Premixed Flames Stabilized on a Bluff Body Burner
Authors: Xia Yu , Verma Ishan , Shrivastava Sourabh , Nakod Pravin , Fletcher David F. , Dally Bassam 
Published: August 2024

Abstract
The demand for carbon-free fuels such as ammonia (NH3) and hydrogen (H2) has been growing rapidly due to stricter environmental policies on carbon emissions. Since ammonia is easier to store and transport, it is considered the leading alternative fuel for marine, aviation, and gas turbine industries. However, the narrow flammability, low reactivity, and potential emissions of nitrogen oxides (NOx) are important challenges that need to be overcome if ammonia is to be used as a practical fuel for industrial use. Recent works have provided important experimental data on the characteristics of NH3 flames under premixed and non-premixed combustion modes, focusing on flame speed, turbulence-chemistry interaction, and especially the dissociation/cracking of NH3 into H2 and N2. These measurements have encouraged the use of Computational Fluid Dynamics (CFD) for the simulation and scaling of practical ammonia systems, evaluating the performance of different numerical models for NH3 combustion. In this study, Large Eddy Simulation (LES) is utilized to predict a series of NH3/H2/N2 non-premixed flames stabilized on a bluff body burner. The accuracy of the Flamelet Generated Manifold (FGM) combustion model combined with LES has been examined, using a commercial CFD solver. The different cracking levels of NH3 into H2 and N2 lead to simulation cases ranging from an H2/N2 flame (i.e., “fully cracked”), to a flame with 50% NH3 (i.e., “half cracked”). The different flame shapes, temperature distributions, NOx and unburnt NH3 emissions have all been simulated, generally matching well the available experimental data. The developed model settings and numerical workflows may be applied to simulating more complex combustors which use NH3 as a fuel.
Prediction Method of Off-Design Aerodynamic Parameter Radial Distributions Between Blade Rows in a Multi-Stage Turbine Based on Stage Similarity Characteristics
Authors: Wang Xinggao , Zhao Wei , Sui Xiuming , Pu Jian , Zhao Qingjun , Xu Jianzhong 
Published: August 2024

Abstract
A method for predicting aerodynamic parameters radial distribution between blade rows in a multi-stage turbine under different operating conditions is proposed. The primary objective is to efficiently obtain the needed parameters, which are derived from the assessment of on-design and off-design conditions conducted during the design process of the turbine’s main flow path. This method is based on the stage similarity characteristics and radial balance of the turbine. By analyzing the flow characteristics, expansion ratio, and efficiency of each stage, as well as the total pressure recovery coefficient of each stage’s guide vanes, and the Mach number and flow angle of each axial clearance between blade rows, it is possible to determine the average velocity and density between blade rows under different operating conditions. The distribution of velocity and density between blade rows under various operating conditions can be estimated based on the circumferentially-averaged flow field at the design point. Additionally, the distribution of static pressure can be calculated using the radial-equilibrium equation. These distribution results enable the calculation of the turbine blade’s axial force and provide boundary conditions for secondary air system analysis. To validate the proposed method, a three-stage axial turbine is used as a case study. The results demonstrate that, for most operating conditions above idle, the predicted pressure exhibits a comparatively high level of accuracy, with a maximum error of less than 5%. Furthermore, the predicted axial blade forces have a maximum error of less than 5%. The validation demonstrates that the proposed method satisfactorily fulfills engineering requirements.
Methodology for Modeling Non Linear Thermomechanical Response With Wear at High-Speed Interactions: Application to a Pin-Disk Configuration
Authors: Pontonnier Soufiane , Quaegebeur Samuel , Thouverez Fabrice , Almeida Patricio 
Published: August 2024

Abstract
An aircraft engine is a complex structure for which some components can come into contact at high speed. Modelling this behaviour is very complex as multiple physics must be considered. State-of-the-art methodologies usually account for permanent contact and thermal modelling. In this paper, a new approach is proposed and embeds various phenomena such as non-regular and non linear contact mechanics, surface rubbing, wear and non linear heat transfer. A non linear version of Moreau-Jean algorithm is employed to compute the transient response of the system and to capture accurately the contact dynamics. Moreover, the full non linear coupling between the dynamics and the heating process is taken into account through both a semi-analytical formulation and the finite-element method. At the contact interface, heat flux is generated by dry rubbing and flows into both interacting bodies. The heat flux partition is evaluated thanks to a coefficient that depends on the material properties of the solids in contact. The proposed method also accounts for the adhesive wear between the solids through an energetic approach. This methodology is applied to an academic, yet realistic, disk connected to a rotor shaft that is free to move axially and to rotate around its revolution axis. Gyroscopic effects and variation of the rotation velocity are included leading to a full non linear mechanical behaviour. The disk undergoes aerodynamic load moving it to contact with a clamped free pin. The rotor shaft and the pin are both modelled as 1D elastic bodies while the rotor disk is assumed to be rigid. Through this example, the developed strategy shows its potential to compute the complete transient highly non linear response of the breaking phenomenon, in an acceptable time simulation.
Flow Variations in Transonic Compressors Tip Flow — An Experimental Perspective Utilizing High Speed PIV
Authors: Klausmann Fabian , Bargon Jonas , Schiffer Heinz-Peter 
Published: August 2024

Abstract
In modern compressor, the demand for highly loaded stages, coupled with lightweight design, necessitates a growing need for high manufacturing accuracy. However, it is challenging to eliminate the underlying sources of uncertainty. Investigating potential factors influencing compressor behaviour has been a crucial area of research. Understanding these influences is essential to enhance design capabilities and drive further advancements in the field.
This study explores flow variations in the tip flow of transonic compressors from an experimental perspective, utilizing high-speed Particle Image Velocimetry synchronized with blade passing frequency. This innovative approach, conducted in a high-speed compressor test rig, allows us to experimentally delve into the full annulus flow field and transient flow behaviour in a unique depth. This paper addresses the challenges encountered in the application of this measurement technique and examines the complete annulus information, focusing specifically on the variation in tip flow from passage to passage. Through the integration of blade tip timing data and 3D white light scan data of the BLISK, this study correlates aerodynamic variations with operational geometric discrepancies arising from manufacturing uncertainties.
The investigations were conducted at a transonic compressor test facility, utilizing a representative high-pressure compressor front stage configuration operated at engine relevant conditions. The experimental findings shed light on the intricate relationship between geometric uncertainties and compressor tip aerodynamics, furthering our understanding and contributing to the advancement of axial compressor technology.
Vaneless Diffuser Modelling for Real Gas Supercritical Carbon Dioxide Flows- Need for a Data Driven Approach
Authors: Seshadri Lakshminarayanan , Kumar Pramod 
Published: August 2024

Abstract
In this work, a real gas-based Vaneless diffuser (VLD) differential equation model is presented. The model requires the specification of the skin friction coefficient as input. However, the use of standard VLD friction coefficient estimation expressions require a re-examination for sCO2 flows. To establish the skin friction coefficient for real gas sCO2 flows, CFD data is generated using Latin Hypercube Sampling (LHS), with boundary conditions spanning the typical operating conditions of sCO2 centrifugal compressors in the kW to MW scale of power generation. The CFD computations are carried out using ANSYS® CFX software. The corresponding VLD friction coefficient for which the VLD stagnation pressure loss predicted by the 1D differential equation model matches with the 3D CFD result is back calculated for all the LHS designs. This is carried out using a root finding function in MATLAB® software. The existing empirical relation that characterizes the VLD skin friction coefficient using the inlet Reynolds number alone shows a poor correlation (R2 = 0.26), when compared to the CFD data. It is evident that a data driven approach is required to model the sCO2 VLD real gas flow for accurate results. Using the LHS data, the efficacy of an Artificial Neural Network (ANN)-based VLD model is demonstrated. A two hidden layer ANN is developed, which accurately predicts the skin friction coefficient for sCO2 real gas flows (R2 = 0.87). This proposed ANN based VLD model can be easily integrated into existing 1D codes for real gas sCO2 centrifugal compressor rating and sizing.
Control of Secondary Flow Losses in a Turbine Stage via Stator Endwall Fence at a Low Reynolds Number
Authors: Yuan Hang , Lu Xingen , Wu Yunfeng , Zhang Jianshe , Zhang Yanfeng 
Published: August 2024

Abstract
Under the demand for refined design and increase in turbine load, reducing secondary flow losses in the endwall region has become a research focus in the field of low-pressure turbines. To explore refined control methods of secondary flow in the endwall region, endwall fences with different geometric parameters are applied to the stator of a low-speed turbine stage at a low Reynolds number. The numerical results indicate that installing an endwall fence device with reasonable parameters on the stator of turbine stage can increase the stage efficiency by 0.21%. The cross migration of the endwall boundary layer within the stator passage is effectively blocked which makes the strength of counter vortex significantly reduced. Moreover, the uniformity of the flow field at the inlet of rotor blade row has been improved. The interaction between the fence vortex and the passage vortex is affected by the design parameters of the endwall fences. However, the endwall fence will introduce additional friction losses and vortices in the endwall region of stator passage. To achieve more efficient control of secondary flow in the endwall region, the XGBoost model and improved chaotic particle swarm optimization have been applied to the optimization design of an endwall fence with nonuniform height in the streamwise. The potential for secondary flow regulation of endwall fences has been more fully developed, and the isentropic efficiency of the turbine stage has been improved by 0.33%. The key design parameters of endwall fences are elucidated using sensitivity analysis methods.
Numerical and Experimental Investigation of the Inclination Angle Effect on the Cooling Effectiveness in a Liquid Fueled Can Type Combustor
Authors: Gulenc Gamze , Ozogul Hamdullah 
Published: August 2024

Abstract
Combustor liner cooling design has been more and more challenging due to increasing efficiency and output power of modern aircraft engines over the last decades. Therefore, not only improving the cooling performance but also investigating the cooling effectiveness accurately are difficult tasks for engineers. The main purposes of the present work are on one hand to propose a simple methodology of investigation of the metal temperature distribution for an effusion cooled combustor liner, and on the other hand to observe the effect of the inclination angle of effusion holes on cooling performance.
An experimental setup based on a liquid fueled can type combustor with effusion cooled liner and a swirler was built to obtain realistic swirling and reacting flow conditions in atmospheric conditions. Two coupons with different effusion hole’s inclination angles of 25 and 35 degrees were used. In addition, one more test coupon with 25 degrees inclination holes was used with thermal paint coating to obtain the metal temperature distribution through its color change on the cold side. Each coupon was equipped with several thermocouples to measure the liner metal temperature and the inlet air temperature. RANS based Computational Fluid Dynamics (CFD) analysis was performed for the can type combustor. Numerical results for metal temperatures were obtained with 1D and 3D thermal analysis. Heat flux values were deducted from the CFD analysis for the 3D thermal methodology. Thus, the pros and cons of each method were compared in the light of the numerical and experimental results. In addition, the effect of the inclination angle on the cooling effectiveness was investigated.