bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impact of Ceramic Matrix Composite Topology on Overall Effectiveness
Authors: Edelson Ryan D. , Thole Karen A. 
Published: October 2022

Abstract
Ceramic matrix composites (CMCs) are a material of interest for components in the hot section of gas turbine engines due to their high strength-to-weight ratio and high temperature capabilities. CMCs are a class of material made of macro scale woven ceramic fibers infiltrated with a ceramic matrix making them significantly different than their nickel superalloy counterparts. As CMCs are implemented into gas turbine engines, the effects of the inherent topology of the CMC weave on convective heat transfer must be understood. In this study, film cooling holes were integrated into a representative CMC weave for three test coupons that were printed using additive manufacturing. The three coupons included: one having a weave topology along the surface of the internal channel supplying coolant to the film cooling holes; one having a weave topology along the external film cooled surface; and one having a weave topology on both the coolant supply channel as well as the external film cooled surface. Overall effectiveness levels for the two cases with a weave surface on the external film cooled wall were measured to be lower than levels for the case with the smooth external surface. The external weave significantly increased the mixing of the coolant jet with the hot mainstream resulting in poor cooling.
Experimental Investigation on Heat Transfer Characteristics in an Impingement/Effusion Cooling System of a Ribbed Turbine Casing
Authors: Li Guodong , Guo Tao , Qiu Changbo , Liu Cunliang , Zhu Huiren , Li Jichen 
Published: October 2022

Abstract
The present paper reports an impingement/effusion cooling structure applied to the turbine casing. The structure consists of three rows of jet holes and two rows of effusion holes, both of which are in a staggered arrangement. A high rib exists inside the impinging chamber for structural support, which is connected to the effusion plate and divides the impinging chamber into two interconnected small chambers, one of which is arranged with effusion holes and the other is not. Transient liquid crystal (TLC) experiments were conducted to investigate the influence of the Reynolds number based on the jet hole diameter (ReD), distance between impingement plate and effusion plate (H), hole pith in Y direction (A) and X direction (C), with a parameter range of 1100 ≤ ReD ≤ 5100, 2.5 ≤ H/D ≤ 7.5, 4.0 ≤ A/D ≤ 14.0 and 8.0 ≤ C/D ≤ 14.0, on the heat transfer characteristics of the effusion plate. The results show that the region averaged Nu increases with an increase in ReD for all studied cases and there is a linear relationship between the ReD and the region averaged Nu in the logarithmic coordinate. The change of H/D has an obvious effect on the heat transfer in the 2D-3D region from the stagnation point. As the H/D increases, the entrainment effect that makes the surrounding fluid continuously enter the jet, resulting in the velocity of the jet decreasing, and the enhanced heat transfer at the effusion plate becomes weaker. When 38 &lt; Y/D &lt; 42 and 0 &lt; Y/D &lt; 1, the Nu increases with the increase of H/D due to the weakening of the flow separation of the wall jet. The variation of A/D has little effect on the enhanced heat transfer in Region1 (surface without effusion hole), but for Regions2-4 (surface with effusion holes), decreasing or increasing A/D is unfavorable to the uniformity of the Nu distribution. The heat transfer enhancement is mainly influenced by C/D. As C/D decreases, the proportion occupied by the stagnation region gradually increases, thus the surface Nu increases significantly.
Aerodynamic Design of Cooling Guide for Electrical Machine in Electric Ducted Fan
Authors: Hu Xuanyang , Qian Yuping , Yang Bijie , Dong Chaofan , Zhang Yangjun , Zhuge Weilin 
Published: October 2022

Abstract
Electric ducted fan has newly emerged as the most compact type of propulsion fan for flying cars, because of its flexible configuration arrangement, low noise level and high safety level operation. Typically, an electric ducted fan is composed of a hub-driven fan and a hub-mounted inner rotor electrical machine. The thermal management of the hub-mounted electrical machine is essential because it determines the machine’s continuous output power and reliability, as well as the fan thrust force. The heat transmitted from the stator winding to the cooling fin is dissipated by introducing the air flow at hub region to the cooling fin. Therefore, in order to better improve the thermal performance of the cooling fin, an aerodynamic design of cooling fin is proposed in this paper for better thermal management of stator end-windings. Firstly, for a certain desired power output of electrical machine under temperature constraints of stator winding, lumped thermal network is established to derive the requirement of heat transfer coefficients of the cooling fin. Then, from engineering feasibility, three different cooling fin designs including straight type, arc-shape type and airfoil shape type are tested by computational fluid dynamics. The evaluation of the cooling fin designs includes the flow characteristics, power requirements and thermal characteristics for stator winding cooling purposes. In comparison with the conventionally straight type cooling fin, improvements are gained from the designed arc-shape type and airfoil shape type cooling fin configurations, whereas the fan thrust force remains the same simultaneously. It is verified that the arc-shape type and airfoil shape type cooling fins are promising in enhancing the thermal management performance of the electrical machine stator winding with little power requirement.
Large Eddy Simulation on the Turbulent Heat Transfer of Supercritical Fluid
Authors: Zhang Junqiang , Zou Zhengping 
Published: October 2022

Abstract
In the present study, the discretizing and synthesizing random flow generation (DSRFG) technique was used to generate three-dimensional instantaneous inflow turbulence with predefined characteristics according to the real turbulence energy spectrum. A large eddy simulation (LES) was utilized to study the turbulent heat transfer of supercritical methane in a horizontal pipe under forced convection. The results show that the thermo-physical properties of the working fluid change rapidly under high heat flux conditions, which leads to a non-uniform distribution of wall temperature in the circumferential direction. The temperature of the upper wall is higher than that of the lower wall, and the temperature difference increases gradually along the axial. The proper orthogonal decomposition (POD) analysis is conducted here by the snapshot method for the turbulent fields. It is found that there are obvious large-scale flow structures on the lower wall. These large-scale structures are arranged in the spanwise direction alternately as well organized clockwise and counterclockwise streamwise swirling motions, enhancing the heat transfer process in the lower wall region. However, there is no coherent structure of the same order near the upper wall. The buoyancy has different effects in the radial direction. It strengthens the turbulent behavior at the lower wall and inhibits the turbulent behavior at the upper wall to a certain extent, which may be an important reason for the increase of heat transfer at the lower wall and the decrease of heat transfer at the upper wall.
Loss Analysis of Cavity Leakage Flow in a Compressor Cascade
Authors: Deng Hefang , Xia Kailong , Teng Jinfang , Lu Shaopeng , Zhu Mingmin , Qiang Xiaoqing 
Published: October 2022

Abstract
The cavity flow of shrouded stators is quite complex and not yet completely understood, especially for its loss characteristics. In this paper, a matrix of numerical simulations was designed and conducted to investigate the loss characteristics of the cavity flow in a compressor cascade, with a wide range of incidence, two flow coefficients, and three seal clearances. The effect of the skewed boundary layer was introduced to simulate the practical compressor environment as far as possible. The results show that the total pressure loss coefficient is unable of evaluating the cavity leakage loss correctly since it ignores the temperature rise. With the reduction of the flow coefficient, the entropy loss coefficient and thermal entropy generation rate trend to increase, while the change of the viscous entropy generation rate is dependent on the incidence since the high tangential velocity deteriorates the flow of the pressure side at large negative incidence but significantly improves the flow of the suction side as the incidence increases. In addition, there is a significant difference in loss sensitivity to the seal clearance at various incidences. One of the major reasons is the change of pressure difference between the downstream and upstream. And the other major reason is the distribution difference of the high-loss fluid caused by the variation in the passage vortex. These key findings are able to provide insights leading to reducing the compressor loss due to the cavity leakage flow.
Comparative Study of Two Data-Driven Gas Path Fault Quantification Methods for a Single-Shaft Gas Turbine
Authors: Xia Shuocheng , Chi Zhongran , Zang Shusheng 
Published: October 2022

Abstract
According to the types of input parameters, data-driven gas path fault quantification methods for gas turbine engines can be divided into two categories: those based on measured parameters and those based on measurement deviations relative to the healthy state. In this paper, the differences between these two kinds of methods are analyzed based on simulation and experimental data.
Based on the thermodynamic model of a single-shaft gas turbine engine, the above two gas path fault quantification methods are established. Through the test data generated by the model, the accuracy of component fault quantification of the two methods is compared. In addition, two sets of experiments are carried out. One is a steady-state test of new and degraded gas turbines, and the other is a gas path component reassembly test. According to the experimental data, the performance and differences of the two methods are compared from three aspects: (a) fault quantification accuracy, (b) ability to capture performance differences between new and degraded components, and (c) consistency of fault quantification results before and after reassembly.
The results show that the performance of the two methods is similar. However, the method based on measured parameters has advantages in computational cost and complexity because it does not need to use the thermodynamic model to convert the measured parameters to measurement deviations during the diagnosis process. In addition, this kind of method requires less training data to achieve the same accuracy.
Flow Design Using CFD for a Constant-Section Recursive Sequential Combustor
Authors: Hofer Andrea , Paulitsch Nina , Giuliani Fabrice 
Published: October 2022

Abstract
The project MOeBIUS stands for MOmentum-Enhanced Blend of the reactants with recIrculated bUrnt gaseS. It is a new combustion concept based on the principle of recursive sequential combustion (RSC), as described in paper GT2021-59592. The aim is to assert the feasibility of a recursive sequential combustor using CFD simulations and to evaluate the most promising flow design for a 3D printed prototype. This paper focuses on the latest developments of the variant called constant section, with a short overview of the geometry’s design iterations. Based on previous simulation results the combustion chamber is torus-shaped with a double-spiral-like cross section. The simulated domain covers a sector of the torus, with interpolated results to augment the data points. Two air inlets and one fuel inlet (currently modelled with Methane) feed the combustion chamber to create a stable, lean, and continuous flame. Flue gas is partly fed back into the combustion process, this recirculation increases lean combustion robustness and decreases the amount of generated nitrogen oxides. The circular combustion chamber and guiding vanes in the in- an outlet pipes generate a flow dynamic that combines a swirling motion necessary to stabilise the flame to a flow circulation along the torus. This flow pattern is driven by the elevated momentum flux at the injection. The air outlet is designed to enforce interaction between outgoing burnt gasses and fresh inlets while facilitating the split of a fraction of the flue gas that follows the torus’ curvature. The simulations confirm the presence of a large swirl in the chambers section, as well as the maintenance of a circulation in the toroidal direction, which is essential to the concept. This is in good agreement with the desired flow design, and the constant section concept is therefore feasible and valid. Ongoing simulations implying fine-tuning of the parameters are carried out in 3D to ensure stable combustion behaviour and meet expectations in terms of functionality.
On the Effect of Side Clearance in the Vaned Diffuser of a Centrifugal Compressor
Authors: Gibson Lee , Spence Stephen , Stuart Charles , Starke Andre , In Kim Sung 
Published: October 2022

Abstract
Environmental and regulatory pressures have prompted original equipment manufacturers (OEMs) to explore highly boosted internal combustion (IC) engines as a means to minimize toxic air pollutants and meet strict legislative targets. The exhaust gas turbocharger is a key technology used to achieve the boost pressures necessary for advanced engines of the future. Centrifugal compressors with vaneless diffusers have been widely implemented in turbochargers for IC engines, particularly passenger vehicles, mainly due to their compact size and ability to deliver high pressure ratios over a wide range of flow rates. Methods to improve compressor efficiency near surge without reducing the surge margin have received considerable interest in the past. In many situations, changes to the impeller blade design and/or diffuser are limited by the need to meet the strict engine rated power target. Such competing demands have encouraged designers to develop variable geometry compressors with the aim of improving near surge performance without sacrificing rated power performance.
The on/off type vaned diffuser is a variable geometry compressor capable of delivering a pressure ratio benefit near surge by utilizing a vaned diffuser rather than a vaneless diffuser. The vanes are retracted prior to the diffuser choking at higher engine speeds to form a vaneless diffuser in order to reach the rated power condition. Diffuser vane shaped clearances in the hub or the shroud end wall, termed side clearances, enable axial sliding variability of the vanes into and out of the diffuser passage. Unfortunately, the clearances manifest themselves as a discontinuity in the flow field which gives rise to an efficiency penalty. It is not yet clear how the side clearance geometry and position affect the compressor performance i.e., efficiency and stability. Hence, a numerical and experimental investigation was carried out to determine the impact of side clearance geometry and end wall position on compressor performance. It was found that a side clearance positioned at the shroud end wall reduced the surge margin of the investigated compressor for both types of clearance geometry considered. In contrast to this, a clearance positioned at the hub end wall improved the compressor surge margin but had the lowest efficiency benefit near surge. An experimentally validated Computational Fluid Dynamics (CFD) model was used to inspect the flow field and to elucidate the reasons behind the changes in compressor performance.
A Numerical Investigation on the Influence of Reynolds Number on the Performance of Volute Stages of Centrifugal Compressors
Authors: Wolbert D. , Schmitt M. , Koenig S. , Wannek M. , Hartmann J. 
Published: October 2022

Abstract
This paper presents the results of a numerical investigation on the influence of Reynolds number on the performance of a single stage centrifugal compressor with an outward wound volute with circular cross section. The main objectives of the presented work were to gain further knowledge on the flow behavior inside the volute with regard to Reynolds number and operating point (surge, best efficiency point and choke) and to compare the numerical results with an existing Reynolds number correction method. The investigation was carried out with steady state simulations and the industry standard SST turbulence model with enabled Reattachment Modification, in which the Reynolds number was systematically varied, and its influence evaluated by a thorough performance and flow analysis. Despite identical stage inlet conditions, a moderate variation of volute inflow conditions was observed with the variation of Reynolds number, which led to a significant impact on the volute efficiency. Therefore, the numerical approach was extended to ensure identical volute inlet conditions which enabled a scientific evaluation of the Reynolds number’s influence on the volute performance. As a result, the expected influence of the Reynolds number on the volute performance was clearly observable, with a decrease of the skin friction losses with increasing Reynolds number. Furthermore, a good agreement with the tested Reynolds number correction method was observed.
Design Methodology and Mission Assessment of Parallel Hybrid Electric Propulsion Systems
Authors: Ghelani Raj , Roumeliotis Ioannis , Saias Chana Anna , Mourouzidis Christos , Pachidis Vassilios , Norman Justin , Bacic Marko 
Published: October 2022

Abstract
An integrated engine cycle design methodology and mission assessment for parallel hybrid electric propulsion architectures are presented in this paper. The aircraft case study considered is inspired by Fokker 100, boosted by an electric motor on the low-pressure shaft of the gas turbine. The fuel burn benefits arising from boosting the low-pressure shaft are discussed for two different baseline engine technologies.
A three-point engine cycle design method is developed to redesign the engine cycle according to the degree of hybridization. The integrated cycle design and power management optimization method is employed to identify potential fuel burn benefits from hybridization for multiple mission ranges. Genetic algorithm-based optimizer has been used to identify optimal power management strategies. The sensitivity of these mission results has also been analyzed for different assumptions on the electric powertrain.
With 1 MW motor power and a battery pack of 2307 kg, a maximum of 3% fuel burn benefit can be obtained by retrofitting the gas turbine for 400 nm mission range. Optimizing the power management strategy can improve this fuel burn benefit by 0.2–0.3%. Redesigning the gas turbine and optimizing the power management strategy, finally provides a maximum fuel benefit of 4.2% on 400 nm.
The results suggest that a high hybridization by power, low hybridization by energy, and ranges below 700 nm are the only cases where the redesigned hybrid electric aircraft has benefits in fuel burn and energy consumption relative to the baseline aircraft.
Finally, it is found that the percentage of fuel burn benefits from the hybrid electric configuration increases with the improvement in engine technology.
Computation of Intrinsic Instability and Sound Generation From Autoignition Fronts
Authors: Gopalakrishnan Harish Subramanian , Gruber Andrea , Moeck Jonas 
Published: October 2022

Abstract
Burning carbon-free fuels such as hydrogen in gas turbines promises power generation with minimal emissions of greenhouse gases. A two-stage sequential combustor architecture with a propagation-stabilized flame in the first stage and an autoignition-stabilized flame in the second stage allows for efficient combustion of hydrogen fuels. However, interactions between the autoignition-stabilized flame and the acoustic modes of the combustor may result in self-sustained thermoacoustic oscillations, which severely affect the stable operation of the combustor. In this paper, we study an ‘intrinsic’ thermoacoustic feedback mechanism in which acoustic waves generated by unsteady heat release rate oscillations of the autoignition front propagate upstream and induce flow perturbations in the incoming reactant mixture, which, in turn, act as a disturbance source for the ignition front. We first perform detailed reactive Navier-Stokes (DNS) and Euler computations of an autoignition front in a one-dimensional setting to demonstrate the occurrence of intrinsic instability. Self-excited ignition front oscillations are observed at a characteristic frequency and tend to become more unstable as the acoustic reflection from the boundaries is increased. The Euler computations yield identical unsteady ignition front behaviour as the DNS computations, suggesting that inviscid mechanisms control the instability. In the second part of this work we present a simplified framework based on the linearized Euler equations (LEE) to compute the sound field generated by an unsteady autoignition front. Unsteady autoignition fronts create sources of sound due to local fluctuations in gas properties, in addition to heat release oscillations, which must be accounted for. The LEE predictions of the fluctuating pressure field in the combustor agree well with the DNS data. The findings of the present work are essential for understanding and modeling thermoacoustic instabilities in reheat combustors with autoignition-stabilized flames.