bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modelling the Film Cooling of a Modern High-Pressure Turbine Nozzle Guide Vane in 3D CFD
Authors: Müller Michael , Schöffler Robin , Grunwitz Clemens , Morsbach Christian 
Published: August 2024

Abstract
In this paper, a reduced order film cooling model previously investigated on single cylindrical and laid back fan-shaped cooling holes is extended with a model variant for trailing edge cooling slots. The extended model is evaluated on a modern HPT NGV combining these cooling features and paired with either an eddy viscosity model or a differential RSM. To simulate a worst-case scenario during the maximum take-off operating point, a hot streak from the combustion chamber with a maximum temperature of about 2230 K is directly impinging on this NGV. Compared to resolved RANS simulations, the model performs better on the NGV than on single holes. In particular, the grid dependency is significantly reduced. The model error and grid dependence peak at the leading edge and decrease downstream of the showerhead. When an average film cooling efficiency is considered, three cells per cooling hole diameter were sufficient to approach grid convergence. A more accurate turbulence model also reduced the model error of the film cooling model, with an absolute error in the averaged film cooling effectiveness of 0.2 at the leading edge and 0.1 at the suction and pressure sides of the NGV.
A Gas Flow Network Model for Predicting Ring Dynamics and Leakage in Dry-Running Pistons Seals for High-Pressure Hydrogen Storage
Authors: Sassoli Andrea , Raspanti Sandro , Romani Luca , Capanni Alessio , Bassani Simone , Ferrara Giovanni , Balduzzi Francesco 
Published: August 2024

Abstract
High-pressure hydrogen storage is essential for maximizing hydrogen potential as a clean energy carrier. Achieving pressures up to 700 bar is necessary to increase its volumetric energy density and reciprocating compressors are favored for their ability to handle high flow rates. Furthermore, maintaining high purity of compressed gas necessitates the use of oil-free machines. Given the unique challenges posed by low molecular weight gas, high pressures, and the use of dry seals, accurately estimating leakage flows and piston ring wear in compressor cylinders is vital.
This paper presents a gas flow network model aimed at predicting wear and leakage of dry-running piston seals for high-pressure hydrogen storage. The model accounts for the dynamics of the seals and the fluid dynamics of gas leaking through the narrow clearances between the moving piston and the cylinder liner, therefore considering the interaction between gas flow and seal displacement within piston grooves. Each volume of the network constitutes a 0-D system where mass and energy conservation equations are solved. Given the complexity of both physical phenomena and cavity geometry, the choice of 0-D systems represents a suitable trade-off between calculation speed and result accuracy.
This paper proposes a numerical model designed to evaluate the thermodynamic properties of the volumes and to predict the pressure drop distribution across piston seals. It also assesses friction power generated by dry seals and identifies rings vulnerable to premature wear. Moreover, the model shows that optimizing the geometrical design of the seals minimizes the gas blow-by, enhancing compression efficiency and extending the machine lifespan.
Numerical Analysis of a Flow Control System for High-Pressure Turbine Vanes Subject to Highly Oscillating Inflow Conditions
Authors: Gallis Panagiotis , Salvadori Simone , Misul Daniela Anna 
Published: August 2024

Abstract
Under the prism of introducing pioneering technologies in the propulsive field, the Rotating Detonation Engine (RDE) continuously attracts the Gas Turbine (GT) research community. However, how to effectively couple an RDE with High-Pressure Turbine (HPT) stages is still debated. In fact, time-dependent flow conditions from the RDE greatly affect turbine performance, thus reducing the positive impact of Pressure Gain Combustion (PGC) on the overall cycle efficiency. The present numerical work aims at analysing both the impact of a pulsating inflow on the performance of a newly designed high-pressure turbine vane and the effectiveness of a flow control system in governing the oscillations within the vane passage. First, a baseline vane capable to ingest high enthalpy flow at an inlet Mach number of 0.6 is introduced. A total number of 297 samples are generated by varying the 18 geometrical parameters that characterize the vane’s endwalls and airfoil profile with the help of Latin Hypercube sampling method. Then, an optimization strategy is performed using steady inflow conditions allows for minimizing vane’s loss coefficient, thus providing the final geometry of the new vane. In the second part of the work, a flow control system is proposed by placing a series of holes in the endwalls of the vane. Air at constant stagnation conditions is injected upstream of vane’s leading edge. Unsteady calculations with and without flow control, including similar pulsating conditions from the RDE provide an insight to the generation and evolution of the secondary flow structures inside of the passage. The main outcome of this analysis is that the flow control system intensifies the passage vortices providing less oscillating flow at the vane exit section, which is beneficial for the aerodynamic performance of a subsequent blade row.
Comparison of Ingestion of Different Size Hard and Soft Bodies Into a Representative Fan Assembly Model
Authors: Mattar Rashid E. , Sirivolu Dushyanth , D’Souza Kiran 
Published: August 2024

Abstract
Foreign matter ingestion into a jet engine is a significant hazard to the safety of aircraft. While soft body ingestions (i.e., bird or ice ingestions) have been extensively researched, the threat posed by uncrewed aircraft systems (UASs) is a more recent concern due to their recent rise in popularity and has not been thoroughly studied. To better understand the damage caused by UAS ingestions, it is crucial to examine the resulting ingestion damage in comparison to birds of similar mass. This analysis is an essential initial step in determining how previous knowledge regarding soft body ingestions can relate to this new threat. To properly analyze these ingestions, development of a model that accurately represents a fan assembly is essential. This model should include a fan, as well as representative boundary conditions for the ingestion, such as blade retention systems, nose cone, casing, and shaft. Items that are analyzed during the ingestion include the overall damage to the fan blades, average and peak forces imparted on the retention systems, impact loads with the casing, and transient loads due to impact on the shaft. The foreign object models used were experimentally validated at their nominal sizes to increase confidence in the results. Comparison of the effects of ingestion of UAS and birds of difference mass into the representative fan model are presented and discussed to gain a better understanding of the differences between soft and hard body ingestion.
The Development of Machine Learning Models for Radial Compressor Monitoring With Instability Detection
Authors: Carrattieri Lorenzo , Cravero Carlo , Marsano Davide , Valenti Emiliano , Sishtla Vishnu , Halbe Chaitanya 
Published: August 2024

Abstract
Modern radial compressors are designed to operate with high performance and a wide range of applications while minimizing their environmental impact. It is necessary to study the machine near the stability limit and gain a comprehensive understanding of the fluid dynamic mechanisms that trigger the instability in the system to extend the operating range at high efficiency. Machine learning aids in developing pattern identification models for detecting compressor instability. In a prior study, a two-stage radial compressor for refrigerant gas underwent extensive simulation, capturing unsteady RANS conditions and generating a substantial dataset of pressure signals from multiple probes. Selected signals, coupled with detailed CFD post-processing, revealed fluid-dynamic structures near surge conditions. This study utilizes all pressure signals to assess the stage’s operational state (stable, transient, or unstable/surge). An additional goal is to develop an algorithm predicting flow patterns in different stage sections with minimal pressure signals at the rotor inlet. This is a preliminary step towards the development of a smart monitoring and diagnostic model for the compressor installed in a plant. The developed model consists of three sub-models, trained with CFD results obtained from URANS simulations. The three sub-models are a regression submodule, a classification submodule, and a forecasting algorithm. The regression submodule predicts diffuser static pressure fields, the classification submodule categorizes whether the compressor is in a critical condition or not, and the forecasting algorithm predicts the inducer pressure signals in the future impeller rotations according to the actual operation history. These sub-modules work together to forecast whether the compressor, according to the operation strategy, is going into instability conditions.
Wave Reformer Channel Shape Design for Enhanced Hydrogen Pyrolysis
Authors: Madiot Ghislain , Tüchler Stefan , Akbari Pejman , Copeland Colin D. 
Published: August 2024

Abstract
A wave reformer utilizes shock wave heating resulting from pressure exchange between a driver and a driven (reactant gas) to initiate a thermal decomposition reaction. Although widely applicable to many reactions, this paper will focus on the thermal pyrolysis of methane to produce hydrogen and solid (black) carbon. It uses wave rotor technology that has been applied to other applications but developed specifically here for high-temperature pyrolysis by New Wave Hydrogen Inc. (NWH). This research uses a quasi-two-dimensional (Q2D) model implemented in Ansys Fluent to study the influence of new channel design features on the unsteady flow field and performance characteristics of the wave reformer.
The primary objective of the work is to investigate the impact of variable area channel design on peak temperature (a proxy for thermal pyrolysis), which has received limited attention in existing literature. The model numerically solves the three-dimensional, compressible, and unsteady Navier-Stokes equations, employing the k-ω-SST turbulence model for closure. Additionally, it utilizes a cell-centered approach coupled to multispecies transport equations and a one-step finite-rate chemistry model. The channel’s curvature is controlled with Sigmoid functions to ensure a smooth area transition along the channel.
The Q2D results reveal that as the fluid traverses the converging channel, its temperature increases due to the rising internal energy, necessary for enhancing hydrogen yields. However, an over-reduction in channel cross-section results in a decrease in the driven mass flow rate, subsequently lowering the mass flow ratio. This work shows that, above a given threshold, there is a significant benefit to implementing converging channel designs in wave reformers for enhanced shock heating.
Investigation of Particle Deposition and Erosion Characteristics of Axial Compressor Blades
Authors: Guo Chuanliang , Chen Shaowen , Chen Shuaitong , Zeng Cong 
Published: August 2024

Abstract
This paper presents a numerical simulation study of the erosive and depositional effects of sand and dust particle ingestion within the compressors of aircraft engines, utilizing a gas-solid two-phase flow approach. An Euler-Lagrangian framework is adopted to track individual particles within the flow field, with a focus on the impact of particle parameters on component erosion. The investigation delves into the internal characteristics of erosion and deposition in the compressor, informed by the behavior of the particle trajectories. Findings reveal that an increase in particle size correlates with more erratic particle paths and an intensified erosion of the compressor blades. The impact angle remains relatively unchanged across various particle sizes, indicating that the velocity of impact is the predominant erosive force. Deposition primarily occurs on the leading edge and pressure side of the blades, with total deposition volume escalating with particle diameter. Interestingly, the deposition rate decreases as particle size increases. This study provides insights that are critical for the enhancement of aero-engine design and maintenance protocols.
Matching of an Overhung Volute to a Centrifugal Compressor at Varied Operating Conditions
Authors: Thiyagarajan Janakiraman , Fredriksson Carl , Anton Nicholas , Genrup Magnus , Fridh Jens 
Published: August 2024

Abstract
Centrifugal compressors are widely used in turbocharged powertrains for Heavy-Duty applications. The volute of the centrifugal compressors is generally of the overhung type. The design of volutes is often neglected, and the shape of the volute is dictated by the packaging requirements of the engine. However, with the advent of Hydrogen-based propulsion systems, the efficiency of all the components of the centrifugal compressor stage is important in order to achieve a higher efficiency at the stage level and also to understand the contribution of the volute towards stage performance. Measuring static pressure and total pressure inside and at the exit of the volute is a challenging task due to the complex nature of the flow inside an overhung volute. This study involves an experimental campaign to quantify the volute performance using static and total pressure measurements at different locations on the volute.
The total pressure measurements were carried out using calibrated rotating Kiel probes to quantify the flow angles and the corresponding total pressure values. This enabled the measurement of the maximum total pressure value at a location for a given operating condition. These total pressures and static pressures were measured for a variety of operating conditions across the entire compressor map at the inlet and exit of the volute. In addition, two new parameters were introduced, a fictive area ratio and uniformity index that could be used to quantify volute performance and also help match the volute to a given diffuser and impeller configuration.
Prediction of Lean Blowout Limits for Bluff Body Stabilized Flame Using a Gradient Method of Damköhler Number and Temperature
Authors: Jia Xin , Hu Bin , Sui Xiuming , Zeng Wen , Yu Xin , Zhao Qingjun 
Published: August 2024

Abstract
The prediction of the lean blowout for bluff body stabilized flame is of great significance for the design of a combustion chamber. In this paper, a lean blowout experiment was conducted on the bluff body stabilizer, and the CH* chemiluminescence was used to illustrate the impact of different equivalence ratios on the flame structure. The realizable k-ε turbulence model and flamelet generated manifolds combustion model were used to simulate the non-premixed bluff body stabilized flame. The characteristic region was determined based on the CO mass fraction, and the relative change rate of the average Damköhler number and temperature relative to the global equivalence ratio within the characteristic region was used as indicators for predicting lean blowout. The results show that as the equivalence ratio decreases, the flame intensity in the recirculation zone decreases, however, the flame intensity within the shear layer remains almost constant. When the equivalence ratio decreases to near blowout, there is a significant decrease in the flame intensity within the shear layer. CO is an important product in combustion and is directly related to the amount of heat released by combustion. The variation pattern of the characteristic region determined based on CO mass fraction with equivalence ratio is consistent with the actual flame variation. The relative rate of change of Damköhler number and temperature within the characteristic region is used to predict lean blowout. The lean blowout limits predicted by these two indicators are compared with experimental results and showed good consistency at different airflow rates and temperature. In general, within the range of examined parameters, the lean blowout limits predicted by Damköhler number are more accurate than the one based on temperature.
Large Eddy Simulations of a High-Speed Low-Pressure Turbine Cascade at Subsonic and Transonic Mach Numbers
Authors: Tene Hedje Patrick , Bricteux Laurent , Bechane Yacine , Lavagnoli Sergio 
Published: August 2024

Abstract
High-Speed Low-Pressure Turbines are one key turbomachinery component in ultra-high bypass ratio geared turbofan engines. The High-Speed Low-Pressure Turbine (HS-LPT) typically operates at transonic exit Mach numbers and low Reynolds numbers. These flow regimes are prone to boundary layer instabilities such as separations on the suction side, leading to a significant increase in losses. It is therefore essential to understand the operation of LPTs and, more specifically, the behaviour of the boundary layer on the blades in such environments.
We present a numerical investigation of a high-speed low-Reynolds turbine cascade simulated at nominal and off-design Mach numbers. The study case is the SPLEEN C1 cascade tested in the transonic linear cascade rig S-1/C of the von Karman Institute. The cascade is numerically operated at the nominal test exit Reynolds number Re2,is = 70k, over a range of subsonic and transonic exit Mach numbers: M2,is = 0.70 ; 0.80 ; 0.90 and 0.95. All simulations are performed with the Explicit Compressible Solver of the massively parallel code YALES2, using a Wall Resolved Large-Eddy Simulations (WRLES) approach, and featuring a fourth-order finite volume spatial discretization. This scale-resolving approach allows to capture the turbine flow physics with high accuracy at an acceptable computational cost. The test case offers the possibility to assess the Mach and compressibility effects on the profile aerodynamics of HS-LPT : separation, transition mechanisms, unsteadiness and passage choking as well as trailing edge unsteady flows.
The flow predictions show a substantial agreement with the available high-fidelity experimental data. Furthermore, the calculations suggest that the wake thins, and loss increase with the Mach number. The experiments support this evidence, although discrepancies are observed in peak losses for Mach numbers above 0.70. The root cause is likely found in the laminar inflow used in the LES simulations compared to the free-stream turbulence intensity level of 2.5% of the experimental test case. Compressibility effects are observed. In particular, a weak compression wave stands in the region of the cascade throat for the case M2,is = 0.90, whereas a shock appears for M2,is = 0.95 with the cascade choked. The role of the shock on the separation and transition on the blade suction side is discussed.
The Influence of Inlet Distortion on Combustion Performance in a Recirculation Combustor
Authors: Luo Shaowen , Shi Yunjiao , Zhao Ningbo , Yang Ren , Zheng Hongtao 
Published: August 2024

Abstract
The mismatching phenomenon between compressor and combustor in gas turbines may cause inlet distortion at combustor entrance, which has an influence on combustion performances. An experimental investigation was carried out in the prevent study to reveal the relationship between inlet distortion and combustion performances. During the experimental work, inlet distortions were introduced by locating orifice plates at the combustor inlet, including mid-peak, upper-biased peak, lower-biased peak. The exhaust gas were measured by the outlet thermal-couple and gas analyzer. Results show that the distortion form and operating conditions have a minor impact on combustion efficiency, whereas they significantly affect the total pressure loss coefficient and the outlet temperature distribution factor (OTDF). In particular, under conditions of higher distortion, the total pressure loss coefficient increases significantly. When the inlet non-uniformity increases from 4.15% to 51.37% (upper-biased peak), the total pressure loss coefficient increases by 2.65% (a 63% increase compared to the previous value), and the OTDF increases by 13.3% (a 67.5% increase compared to the previous value). Additionally, the impact of the upper-biased peak distortion on OTDF is greater than that of the lower-biased peak distortion.
Numerical Investigation and Multi-Objective Structure Optimization of Transpiration Cooling on the Leading Edge of Turbine Blade
Authors: Liu Taolue , He Fei , Wu Xiaorong , Zhou Zhizhao , He Yang , Wang Jianhua 
Published: August 2024

Abstract
Transpiration cooling, utilizing the micro-hole channel of the porous matrix, is regarded as highly promising turbine blade cooling applications. This study comprehensively investigates the cooling performance of transpiration cooling on the leading edge of C3X turbine blade. The numerical investigation is conducted by comparing the uniform and gradient porous matrix. Various influence factors such as coolant mass rate, porosity and average pore diameter are taken into discussion. The simulation results suggest that the gradient porous matrix scheme can improve cooling efficiency by altering the permeability distribution and adjusting coolant flow accordingly. Additionally, the average total pressure loss coefficient is primarily influenced by the region directly facing the mainstream and the new structure can also reduce this coefficient. To optimize the transpiration cooling performance with a gradient design, a novel optimization process is proposed, which combines Computational Fluid Dynamics (CFD), Artificial Neural Network (ANN) and Multi-Objective Genetic Algorithm (MOGA). The optimization process is implemented through the coupling simulation of ANSYS FLUENT and MATLAB via Text User Interface (TUI) and User Defined Function (UDF). The configuration parameters of the porous matrix are set as design variables, with the average cooling efficiency and average total pressure loss coefficient serving as optimization objectives. The simulation results demonstrate an improvement in the former (increases by 11.35%) and a reduction in the latter (decreases by 36.23%) respectively compared with the uniform porous matrix. This optimization process provides a straightforward and reliable method for addressing a range of similar structural issues.