bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aerodynamic Design Optimization of Centrifugal Compressor Blade Using Parameterized Free-Form Deformation
Authors: Xu Dongqiang , Yu Jianyang , Shen Jinsong , Li Ning , Song Yanping , Yang Xinlong 
Published: August 2024

Abstract
To address the challenges encountered during a multioperating-point optimization of centrifugal compressor blades, including a large design space, redundant search, limited flexibility, and low optimization efficiency, this paper presents an aerodynamic optimization approach for centrifugal compressor impeller blades based on parameterized free-form deformation (FFD) and deep learning. To realize the parametric control of a compressor blade, a three-dimensional FFD control body is arranged around a blade according to the geometric characteristics. The inverse distance weighting (IDW) mesh deformation algorithm is used to extrapolate the deformation of surface mesh points to volume mesh points. Using this method, the analysis mesh can be directly updated with high quality instead of regenerating the geometry model when design variables are changed during optimization. Based on this and convolutional neural networks, a design optimization framework is established by combining the optimal Latin hypercube sample method and the NSGA-II multi-objective genetic algorithm. An optimization of the centrifugal compressor blade of a micro gas turbine was carried out, and the results showed that the total pressure ratio and isentropic efficiency at the design point was increased by 4.03% and 1.21 percentage points, respectively. The optimization results demonstrate that the developed optimization framework can effectively improve the performance of centrifugal compressors and provide support for compressor design.
Investigation of the Sigma Approximation Technique for the Solution of the Time Spectral Equation System
Authors: Zhu Yuze , Zhang Yuxuan , Zhang Sen , Wang Dingxi 
Published: August 2024

Abstract
The time spectral method is commonly utilized to analyze periodic unsteady flows within turbomachines. However, the time spectral solutions in regions with large temporal and spatial gradients, such as wakes, shocks, and boundary layers, can be plagued with unphysical oscillations, known as the Gibbs phenomenon. This paper presents an investigation into the sigma approximation technique, which is capable of significantly attenuating the Gibbs phenomenon by dampening high-frequency nonlinear components in the time spectral solutions. Central to this technique are three sigma factors: the exponent, the cut-off number, and the number of harmonics, which collectively determine the damping effects for each frequency. However, the optimal combination of them remains to be ascertained considering the trade-off between the accuracy of solutions and the reduction of unphysical oscillations. In this study, numerical simulations are performed to evaluate the efficacy of this technique based on a two-row compressor configuration. It is found that the Gibbs-type unphysical oscillations can be effectively mitigated without notably compromising the solution accuracy through an optimal combination scheme of sigma factors. The NASA Stage 35 case study further verifies the effectiveness of the proposed optimal sigma factor combination in preserving the accuracy of time spectral solutions. Moreover, the von Neumann analysis reveals that the sigma approximation technique can enhance the numerical stability of the time spectral equation system, thereby allowing the use of aggressive numerical parameters to accelerate convergence. The stability analysis results are verified by a two-dimension bump under two different flow conditions and further assessed using a two-row compressor.
Industrial Applications of Transfer Learning Methods for Aircraft Propulsion Systems
Authors: Jacobs Ryan , Krishnan Sandipp , Bhaduri Anindya , Luan Lele , Pandita Piyush , Ghosh Sayan , Wang Liping 
Published: August 2024

Abstract
Sparse data problems challenge engineers throughout the lifecycle of aircraft propulsion systems. For instance, data from legacy systems may not be applicable to novel high-pressure turbine blade configurations, driving substantial computational and test efforts to design and validate the blade. Once the blade is fielded, some manufacturers implement predictive maintenance approaches to reduce downtime and associated costs of sustaining the fleet. However, after entry-into-service for a new design or re-design, limited field observations are available with which to construct prognostic models for the life of the blade. In this paper we explore transfer learning methods in machine learning to overcome these challenges. The goal is to borrow strength from one setting with abundant data — available for legacy systems that may have different configurations and/or operations — and transfer the embedded knowledge to model new systems in a different setting where fewer data are available. Transfer learning methods have been implemented for a broad range of machine learning approaches, and in this paper we highlight industrial propulsion applications from various phases of the propulsion system life-cycle where transfer learning is applied with three frameworks that GE has developed: Bayesian Hybrid Modeling, Probabilistic Deep Neural Networks, and Physics Discovery. The added benefit of leveraging data from similar contexts is examined for each framework.
Data-Driven Turbulence Modeling for Film Cooling Heat Transport, Part II: Modeling and Evaluation
Authors: Zhang Zhen , Zhang Weiran , Su Xinrong , Yuan Xin 
Published: August 2024

Abstract
In film cooling problems, the turbulent heat transport and the resultant cooling effectiveness distribution are difficult to predict for traditional Reynolds-averaged Navier-Stokes (RANS) methods. In this paper, a data-driven model of the turbulent Prandtl number is built based on the Physics Informed Neural Network (PINN), which trains the turbulence model based on flow data from RANS and temperature data from Large Eddy Simulation (LES). PINN is used as an efficient inverse solver to get turbulence information from the mean flow data such as velocity and temperature and also as a model trainer to train the algebraic turbulence model at the same time. Accelerated by modern GPUs, the PINN method has been a powerful competitor to the adjoint method and the ensemble Kalman filter to solve inverse problems. The obtained data-driven model can adjust the intensity of turbulent heat transport and thus reduce the error of the traditional RANS method. After validation, the model shows good generalization ability when the hole geometry and the blowing ratio vary.
Damping Phenomena in Rotating Machines: A Focus on Rotor Damping With Synchronous and Asynchronous Excitation
Authors: D’Alessandro Francesco , Garnier Florian , Guivarch Damien , Zutshi Amit , Kang Weize , Kunnil Manoj , Narayanan Payyoor , Robinson Mark , Kumar J. S. , Cao Jianming , Rose Ted 
Published: August 2024

Abstract
Accurate modeling of damping in rotors is critical for rotor dynamic analysis of turbo machinery such as aircraft engines. This paper documents the recent work of the ‘Rotordynamics consortium’ with the cooperation of Safran Aircraft Engines, General Electric Aerospace, Hexagon (MSC.Software) and Boeing demonstrating best practices for rotor damping across the solution disciplines of both frequency and transient response as well as complex eigenvalue analysis. Any rotating machine is subject to out of balance loading due to the imperfections associated with manufacturing processes. Out of balance or unbalance loading is always present and is known as a synchronous phenomenon as the frequency of the unbalance excitation is synchronous with the rotation speed of the rotor, leading to vibration causing noise and fatigue issues. In contrast, the frequencies of asynchronous vibrations are unrelated to the rotation speed of the rotor and are typically caused by external aerodynamic loads, bearing properties such as squeeze film dampers and other nonlinearities to name a few. Synchronous excitation tends only to excite forward whirl modes of rotating machines that are axisymmetric, whereas asynchronous excitation may excite any whirl modes of the structure, even those with a rotor that is axisymmetric. With the deep differences in these two families of excitation, it is essential to adapt the simulation procedure to the type of excitation and especially important to represent the frequency dependent damping affecting rotating parts in a faithful manner. Viscous and structural (hysteretic) damping are studied numerically in a rotating shaft under synchronous and asynchronous excitation using the MSC NASTRAN finite element software. A simplified dual-rotor finite element model is used to demonstrate the non-synchronous response of one rotor on the other one, representative of a whole aircraft engine. Credible values of stiffness, damping and mass properties are adopted to give integrity to the work and pave the way to an industrial scale problem.
A Thermal Model for a Hybrid Gas Bearing System in Oil-Free Turbochargers
Authors: Jung Wonbae , Delgado Adolfo , Dudlo Anthony , Kang Sang-Guk , Kweon Chol-Bum M. 
Published: August 2024

Abstract
With little drag friction, gas bearings operate at high rotor speed and high temperature and thus enable long operating life along with material damping for mechanical energy dissipation. However, most computational tools for modeling gas bearings are not accessible to bearing manufacturers or potential endusers, and the models are restricted to specific geometries and operating conditions or are missing important features, thus limiting their utility. This paper presents the thermal energy transport in a hybrid gas bearing for oil-free turbochargers with integrated heat and fluid flow models to produce a comprehensive thermo-hydrodynamic analysis predictive tool, and to design and evaluate air-lubricated gas bearings by predictions and experiments. An efficient algorithm couples the solution of the Reynolds equations and the thermal energy transport equations in the film between the rotor and a pad of the hybrid gas bearing, and updates the temperature-dependent viscosity and film thicknesses during the iterative process. The balance of the bulk-flow thermal energy transport is that the summation of drag power losses plus heat convection into the film equals to the thermal energy advected by the film. The predictions show the film temperature varies along circumferential and axial directions by following the balance of the energy flows, and shows high film temperatures corresponding to the small film thicknesses and thus large film pressures. The predicted result also shows the peak temperature of the film occurs at the exit side of the film near the trailing edge of each pad. Thermocouples installed axially at the leading and trailing edges of each pad measure temperature of the film to validate the thermal module. The test repeats and averaged for each rotor speed from 2 krpm to 22 krpm at intervals of 2 krpm, for supply pressure varying along 25 psi to 100 psi and predicted film temperature matches well with the measured one. The parameters of interest in this analysis include the gas supply condition, bearing configuration, and the gas properties at high altitudes and high rotation speeds. The parametric study results show the density and kinematic viscosity are the most dominant properties of the gas lubrication for the film temperature.
Thermal and Structural-Mechanical Modeling and Optimization of a Transiently Operated Steam Turbine Using the FE Method
Authors: Lange Hendrik , Kostenko Yevgen , Veltmann David 
Published: August 2024

Abstract
Due to the growing share of renewable energy sources, there is increasing volatility in the energy fed into the grid. To cover the load when renewable energy is unavailable, steam turbines in conventional power plants must be operated more flexible and in line with the demand. The increased number of start-up processes after longer standstills results in high lifetime consumption of steam turbine. This mode of operation increases the utilization on components, which results in a reduction in service life.
The Hot Standby process has already been proven itself as a method of Siemens Energy Flex-Power Services for making steam turbine operating processes more flexible. Through targeted heat transfer to the steam turbine components using a trace heating system, a cold start can be avoided, and the operational flexibility of the turbine can be increased. Heat transfer occurs predominantly via thermal radiation, which is particularly difficult to simulate compared to other heat transfer mechanisms.
To simplify heat radiation exchange and still achieve realistic results, various methods and parameter settings are applied.
In this paper the heat transfer via thermal radiation and its influence on heating up of structural turbine components is investigated. At the beginning, different benchmark parameter settings and the associated result variations are presented. These findings are then implemented in the modeling of the SST-3000 turbo set of Siemens Energy and the results of the simulation are discussed. The simulation results are used to determine temperature gradients that are used to design hot standby features used for flexible power plant operations.
Impact of Diluents on Flame Stability With Blends of Natural Gas and Hydrogen
Authors: Rodriguez Camacho Javier , Le Dang , Blust James , O’Connor Jacqueline 
Published: August 2024

Abstract
Two potential decarbonization pathways for natural gas (NG) fueled gas turbine engines include blending hydrogen (H2) into NG and post-combustion carbon capture. H2 blending changes several combustion properties, including flame speed and stretch sensitivity. The use of post-combustion carbon capture systems is typically facilitated by the implementation of exhaust gas recirculation (EGR), where exhaust gases are injected into the inlet of the engine, increasing carbon dioxide (CO2) concentration at the outlet and, hence, increasing the efficiency of carbon capture technologies. In this work, we explore the impact of H2 blending and EGR on the stability of a swirl-stabilized, central-piloted flame. Mixtures of NG and H2 are tested at a range of different diluent compositions, with oxygen varied from 21% to 15% by volume in the oxidizer. In all cases, a constant adiabatic flame temperature is maintained to mimic the operation of a gas turbine at a given turbine inlet temperature. A variable-length combustor is used for testing, where combustor length is varied to understand the dynamic stability characteristics of the system. Results show that EGR and H2 work in opposition to each other, where higher levels of EGR result in poor flame holding and higher levels of H2 result in better flame holding. Increasing H2 generally increases the amplitude of thermoacoustic instability at each condition, a result of the change in flame position in this particular combustor. Importantly, H2 can be added to NG to improve flame holding without significantly decreasing CO2 levels in the products, showing that H2 blending can be a method for counteracting combustor operability issues that arise from high levels of EGR necessary to improve the efficiency of typical carbon capture systems.
Numerical Study on Combustion of a Novel Micromix Multi-Nozzles for Kerosene/Hydrogen Fuels
Authors: Fu Pengfei , Wang Yafen , Hou Lingyun 
Published: August 2024

Abstract
Hydrogen combustion is emerging as one of the most promising options for future commercial aircraft propulsion. Transition from fossil fuels to hydrogen is expected to take time, and drop-in technologies, such as blending hydrogen with hydrocarbon fuels for combustion, are of significant importance for meeting decarbonization goals in the short term. Liquid kerosene and gaseous hydrogen have significant differences in physical and combustion characteristics. It is a significant challenge to achieve stable combustion of both kerosene and hydrogen simultaneously.
A new micro-mixed coaxial nozzle for kerosene/hydrogen fuels was proposed. The kerosene spray flame is stabilized by a micro swirler, while hydrogen is mixed in a circular microchannel surrounding the swirler and coaxially arranged with the central axis of the spray nozzle. The numerical simulation including a skeletal reaction kinetics model with 54 species and 269 reactions was conducted and validated through comparisons with experimental data. The impact of hydrogen injection parameters, hydrogen blending ratio, swirling intensity, and nozzle distance on the combustion characteristics of the kerosene/hydrogen mixture were investigated. It is shown that the uniformity of hydrogen circumferential distribution in the annular mixing channel results in either individual multi-beam flames or a complete annular flame. Increasing the swirl number reduces the axial lengths of both the hydrogen and kerosene flames, resulting in more compact flame branches. NO emissions are minimized when the hydrogen blending ratio falls within the range of 10%–20%. The merged flame mode and free flame mode are observed for the adjacent hydrogen flames in different nozzle distances. It provides guidance for the design of low-carbon multi-fuel nozzle in gas turbine combustor.
Effects of Mainstream Incidence Angle on the Cooling Performance of the Rotational Turbine Blade Tip
Authors: Wang Xilai , Tao Zhi , Li Haiwang , Zhou Zhiyu , Xie Gang , Meng Long 
Published: August 2024

Abstract
The rotation fluctuation or the mainstream unsteadiness could cause the variation of the incoming incidence angle, affecting the cooling performance of the turbine blade. Most literature concentrates on the effects of incidence angle in the mid-pitch region, leaving the tip region less concerned. Considering that the complicated flow field in the tip region could sometimes worsen cooling effectiveness, this paper investigates the effects of mainstream incidence angle on the cooling performance of the rotational blade tip. The first stage of GE-E3 high pressure turbine blade with full composite cooling structure is used in this study and conjugate heat transfer numerical simulations are conducted on ANSYS CFX 2019R3 to calculate both the flow field and the solid temperature field. SST k-w turbulence model is adopted to enclose the RANS methods after multiple validations. Three rotational speeds, namely, 90%, 100% and 110% of the design point (13287 rpm), are simulated in three coolant mass flow rates (1.65%, 3.3% and 4.95% of the main flow rate) and three tip clearance ratios (0.5%, 1% and 1.5% of the total blade pitch). According to the results, the pressure side rim consistently gets cooler as the incidence angle changes from positive to negative because less leakage gets over the pressure rim. But in comparison, the trends of the suction side are complex. At the positive incidence angle, the large pressure difference forces nearly all coolant to exhaust over the suction rim, facilitating the coolant coverage there. At zero incidence angle, the leakage over the suction rim could raise the temperature in the thickest area. But as the incidence angle turns negative, the larger mainstream leakage over the suction rim could form an anti-rotating vortex. With large coolant flow rate or small tip clearance, the mainstream invasion would increase the temperature whereas with small coolant flow rate or large tip clearance, the vortex entrainment could decrease the temperature.
The Effect of Acoustic Boundary Conditions on the Oscillation Mode Transition of Combustion System
Authors: Lu Yudi , Jin Ming , Ge Bing , Zang Shusheng 
Published: August 2024

Abstract
The lean premixed combustion technology makes thermoacoustic oscillation possible to occur in gas turbine combustor. With the change of operating condition, the amplitude and frequency of thermoacoustic oscillation also change. The oscillation mode can even change suddenly. This mode transition is closely related to the acoustic boundary conditions of the system. This paper investigates the impact of the acoustic boundary conditions of the outlet of the combustion system on the oscillation modes. By varying the equivalence ratio, the system is made to oscillate in different modes. The acoustic reflection coefficient and impedance of the system outlet are measured through double-sound-transducer method, and numerical simulations are conducted to investigate their impact on the growth rates of the oscillation modes. The results indicate that under different equivalence ratios, the combustion system exhibits three distinct oscillation modes. As the equivalence ratio in the combustor increases, the low-frequency mode gradually disappears and even undergoes a sudden transition to a high-frequency mode. The phase of the outlet acoustic reflection coefficient and impedance of the three modes are significantly different, which can reach up to 180°. There are two different principles for the mode disappearance. One is due to the acoustic reflectivity exceeding the critical value, while the other is due to the gradual decrease of it. Numerical simulations of oscillation modes are conducted based on the acoustic impedance measured. The simulated modes with the highest growth rate agree well with the experimental results, with an error within 1.94%. This study provides experimental and numerical methods for accurately obtaining growth rates of oscillation modes. Accurate boundary acoustic impedance is crucial for predicting oscillations. The reflectivity and the phase of boundary acoustic impedance are the primary reasons for mode transitions.
Effect of Film Hole Configuration on the Impingement-Film Composite Cooling Performance of a Simulated Turbine Blade Leading Edge
Authors: Chen Xinnan , Bai Bo , Li Zhigang , Li Jun 
Published: August 2024

Abstract
Eight film hole configurations were implemented on a simulated turbine blade leading edge to serve as the showerhead. Both adiabatic and conjugate heat transfer analyses were conducted. The effect of film hole configuration on flow resistance, heat transfer characteristics, film coverage, and composite cooling performance of the leading edge were all investigated. Additionally, the influence of coolant mass flowrate across a wide range was also considered. The results indicate that all expansion holes effectively increased the discharge coefficient, especially at relatively higher coolant mass flowrate. The amplified hole and double-jet hole also reduced the flow resistance under high coolant mass flowrates, but caused severe gas ingestion at low mass flowrates. Furthermore, impingement cooling demonstrated continuous improvement in heat transfer intensity with increasing coolant mass flowrate, while the effect of expansion holes on it was nearly negligible. Moreover, the composite cooling performance of expansion holes was highly correlated with both forward and lateral expansion angles, which played a more critical role than hole shape designs in determining the cooling performance. In comparison to conventional showerhead designs, the two novel holes exhibited significantly improved composite cooling performance, especially the effusion hole. However, it should be noted that the incorporation of effusion hole also resulted in serious pressure loss of coolant.