bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Automatic Film Cooling Hole Mesh Generation System Based on Matrix Dividing Strategy
Authors: Fan Jiazheng , Jia Xiaotong , Han Chuang , Li Weihong , Duan Penghao 
Published: August 2024

Abstract
Film cooling is one of the essential measures to guarantee the turbine blade’s durability. In the film cooling system design process, it is inevitable for researchers to generate the cooling hole mesh in order to perform the CFD simulation of turbine blades. However, generating hundreds of cooling holes’ mesh is time-consuming and requires plenty of manual operations. In addition, to implement the optimal film cooling hole distribution, there is a need to develop a parametric design methodology to arrange the position of cooling holes reasonably. The present paper develops an automated film cooling hole mesh generation system, which adopts a matrix dividing strategy to parameterize the film cooling system. The geometrical representation of the cooling-hole distribution is parameterized by m × n matrices. The system first splits the existing block based on the matrix parameters, dividing the blade surface into m × n pieces. Then, it uses a parametric system to design the cooling hole geometry and automatically generates cooling hole blocking lines at the pieces of interest. The cylindrical and fan-shaped hole topology can be automatically generated in the parametric system. Finally, the transfinite interpolation method is used to automatically produce the structured mesh from the blocking lines. This system can also use the above technologies to generate the cooling hole mesh on the tip of rotor blades.
The film cooling hole mesh generation system has been integrated into our existing turbine blade design platform (NuFlux), which is designed to implement the fast changing of the 3D blade geometry and automated structured mesh generation. To verify the reliability of the cooling hole meshing system, the computational grids of NASA C3X film-cooled vane and transonic HPT rotor blade with tip cooling injection are produced using the system and examined in the mesh quality check system in NuFlux. The CFD simulation results using the grids are validated against the relevant experimental data. The integration of the cooling hole meshing system makes NuFlux a unique tool which is competent at turbine blade cooling system design optimization.
An Integrated Neural Network and Finite Element Method for Defect Characterization and Strength Prediction of Unidirectional Composites
Authors: Zhang Bo , Liu Changqi , Shi Duoqi , Yang Xiaoguang 
Published: August 2024

Abstract
This study proposes an integrated approach that combines neural networks and finite element analysis for robust defect recognition and accurate prediction of mechanical strength in unidirectional composite materials. ABAQUS is employed for simulating random distributions of fibers and pores, along with variations in mechanical properties. Numerical simulations, based on the Monte Carlo method, provide authentic mechanical performance data as output labels for the neural network. Two methods for recognizing geometric features are employed: 1) Image recognition using a two-point cross-correlation algorithm, refined through techniques like feature selection and principal component analysis for efficient extraction of essential geometric features. 2) Convolutional neural networks with attention mechanisms for improved capturing and recognition of features. Additional descriptors such as kurtosis, skewness, and eccentricity are incorporated for a comprehensive analysis of the influence of pore morphology on mechanical performance. Deep learning techniques reveal concealed patterns, leading to highly precise mechanical property models. This innovative approach for defect characterization in unidirectional composite materials yields rapid and accurate results, with predicted tensile strength errors consistently below 10%.
Compressor Blade Vibrations of Next Generation of Turbocharger With Focus on Damping: Simplified Prediction and AI-Based Evaluation
Authors: Weber Robby , Glatt Matthias 
Published: August 2024

Abstract
Recently [1], Accelleron announced the X300-L series, marking the beginning of a new concept in turbocharger technology. This innovative platform-based approach simplifies service procedures but also provides adaptability to respond to diverse demands caused by a certain variety of future fuels. The integration of enhanced power densities, standardized components, and a modular design offers fewer frame sizes and variants. Consequently, individual core components (i.e., compressor wheel or turbine impeller) are necessarily not only more compact and more powerful but also extend their utility across a wider range of applications.
Accurate blade vibration analysis is essential to identify potential performance issues, mitigate fatigue and wear, and prevent disastrous failures. The complete variety of numerical and experimental methods that are involved during the modern development process of new turbochargers will easily extend the scope of this contribution. To allow a more detailed insight, this paper presents a comprehensive study on compressor blade vibrations; with a particular focus on damping as one of the most important aspects of high-cycle fatigue.
First, a blade vibration measurement is carried out employing both strain gauges and blade tip timing, two cutting-edge methodologies that demonstrate strong mutual consistency. The dynamic stress of five chosen resonance crossings is investigated to primarily underline the robustness against high-cycle fatigue and show the agreement between strain gauge and tip timing measurements.
Second, a simplified method is adopted to predict critical damping ratios of specific blade vibration resonances. This approach incorporates inputs as modal parameters (like natural frequency and mode shape) and operational conditions (fluid density and speed of sound), all of which are conveniently accessible during the preliminary design phase.
Third, experimental data from several resonance crossings recorded with strain gauges are fed into an AI-driven methodology utilizing Deep Learning, enabling the assessment of genuine damping ratios for these resonances. Subsequently, a comparison is presented, contrasting the new damping evaluation (AI based on strain gauge measurement) with a state-of-the-art solution (SDOF-Fit of tip timing data) as well as the predicted damping ratios of the first part.
In conclusion, this paper not only highlights the good performance of the compressor in terms of HCF strength but also underscores its accelerated development through the use of reliable data from the early design phase. Modern measurement techniques offer remarkable precision, validate numerical predictions, and finally increase the trust in such methods. The proposed AI-based damping estimator validates damping predictions as a practical tool for engineers in the field of turbocharger development, facilitating the development of more reliable and efficient turbocharging systems for future applications.
On the Development of an Efficient Sliding Mesh Interface for the Harmonic Balance Method, Part II: Effects of Casing Treatments on the Aerodynamic Damping of a Compressor Blade
Authors: Hartmann Maximilian , Schlüß Daniel , Geiser Georg , Schwarzenthal Felix , Ashcroft Graham , Herbst Florian 
Published: August 2024

Abstract
In order to enable the Harmonic Balance (HB) method for efficiently capturing the non-linear effects of complicated configurations such as casing treatments, we introduce an algorithm for the coupling of non-conforming mesh topologies across domain boundaries in a series of two papers.
In this second paper, we demonstrate the novel sliding mesh method’s relevance for the design of modern transonic compressor rotors with casing treatments. In order to allow for a flutter assessment of the rotor with the flow solver TRACE a specific mesh topology for the frequency domain approach to connect stationary cavities with the moving rotor domain is introduced. It shows no significant impact on the flow characteristics of interest. HB results are successfully verified by means of time domain simulations (TD) with respect to average flow quantities and unsteady flow characteristics. Both methods clearly illustrate that a casing treatment not only affects the average flow field but also significantly changes the unsteady flow viz. the aerodynamic damping of the rotor. By providing the same prediction quality for more than one order of magnitude less computational resources than the TD approach the novel method enables an efficient industrial design process for such configurations with HB.
Prediction of the Flame Characteristics of an Industrial Gas Turbine Operated With CO2-Diluted Air Through an LES-Based CFD Analysis: A Comparison Between FGM and ATF
Authors: Lemmi Gianmarco , Castellani Simone , Galeotti Sofia , Picchi Alessio , Becchi Riccardo , Andreini Antonio , Babazzi Giulia , Meloni Roberto 
Published: August 2024

Abstract
In light of the global commitment to decarbonize industrial processes, Carbon Capture and Storage (CCS) plays a pivotal role in mitigating greenhouse gas emissions from Gas Turbine (GT) power generation processes. Achieving an efficient GT-CCS coupling requires the employment of high percentages of Exhaust Gas Recirculation (EGR) to maximize the CO2 content at the CCS inlet. Nevertheless, such operating conditions pose critical challenges for conventional combustion systems due to reduced oxygen levels associated with higher EGR, limiting engine operability. To address this challenge, the development of innovative technical solutions is essential to extend the combustor operational capabilities at high EGR rates. For this goal, a significant number of Computational Fluid Dynamics (CFD) simulations are required to identify the flame stability limits across various EGR levels and burner designs. It is imperative, in this context, to minimize computational costs while maintaining high accuracy. In this work, a comprehensive comparative study of an extended version of the Flamelet Generated Manifolds (FGM) and the Artificially Thickened Flame (ATF) model is performed through a Large Eddy Simulation (LES) based CFD analysis. The investigation is performed within the context of an industrial lean premixed burner manufactured by Baker Hughes, operating with Natural Gas and CO2-diluted air at atmospheric pressure. While the extended-FGM has been previously presented by the authors in a study on the same test rig under standard air conditions, the current work aims to extend its application to critical oxygen-depleted conditions, where near-blow-out phenomena such as flame lift-off and length elongation may become significantly pronounced. Numerical validation is carried out through a direct comparison of the computed averaged heat-release, representing the flame topology, with detailed OH* chemiluminescence images from a test campaign conducted by the THT Lab of the University of Florence. The experimental data will serve as the primary benchmark for assessing the models’ effectiveness in capturing the main dynamics of such critical operating conditions. Furthermore, potential disparities in both thermal and flow fields at the burner exit region between the two models will be discussed.
Effect of Dilution Hole Diameter on the Outlet Temperature Distribution in a Centrally Staged Combustor
Authors: Pang Liyao , Xu Honghao , Zhao Ningbo , Li Zongfu , Zheng Hongtao 
Published: August 2024

Abstract
Temperature distribution at combustor outlet is pivotal for lifetime and operational reliability of a turbine, wherein dilution hole diameter emerges as a significant design parameter influencing it. In the present work, numerical simulations of five schemes of a single-sector centrally staged combustor with different dilution hole diameters are conducted. The influence of dilution hole diameters ranging from 8 to 16 mm onflow characteristics inside combustors is explored, while the morphology and development of both high-temperature region and flame, as well as the formation process of hot streaks at outlet are analyzed. The results indicate that, with a constant inlet mass flow rate, the dilution hole diameter affects jet penetration depth and axial length of the primary recirculation zone (PRZ). As dilution hole diameter increases, equivalence ratio in the main combustion zone gradually approaches or even exceeds the stoichiometric ratio, resulting in a transition from lean to rich fuel therein, and an expansion of the high-temperature region. Under smaller dilution hole size, two obvious flame fronts form at the PRZ and the interface between the dilution hole jet and the shear layer. As the hole diameter increases to 16 mm, flame fronts are separated by the shear, leading to a reduction of obvious flame fronts to a single location in the PRZ after separation. As hole diameter increases from 8 to 16 mm, total pressure loss decreases from 3.5% to 2.6%, and combustion efficiency drops from 99.97% to 99.79%. Both pattern factor and radial pattern factor initially rise and subsequently reduce. The combustor exhibits optimal performance when dilution hole diameter is 14 mm.
Advanced Methods for Assessing Flow Physics of the TU Darmstadt Compressor Stage: Part 1 – Transitional Delayed Detached-Eddy Simulation
Authors: Möller Felix M. , Tucker Paul G. , Wang Zhong-Nan , Bode Christoph , Morsbach Christian , Matha Marcel , Sivel Pierre 
Published: August 2024

Abstract
In this first paper of the two-part series, we analyze the predictive quality of transitional Delayed Detached-Eddy Simulation (DDES) for the transonic TU Darmstadt (TUDa) compressor stage. Initially, we validate the DDES in a translational configuration of the compressor at reduced rotational speed. Here we compare DDES results with previously published Large-Eddy Simulation (LES), steady and unsteady Reynolds-averaged Navier-Stokes (RANS) simulations. As the application of the DDES shows noticeable improvements for the shock boundary layer interaction (SBLI) and resulting laminar-to-turbulent transition, we continue analyzing the fully 3D setup. For this configuration, two operating conditions (aerodynamic design point (ADP) and near stall) are considered. We show DDES results and compare them to steady and unsteady RANS simulations, and experiments where available. Although the DDES indicates some improvements at the ADP, RANS is also able of predicting integral turbomachinery performance quantities. However, steady and unsteady RANS fail to predict the flow field with satisfying accuracy at near stall conditions. Especially in separated regions, DDES proves its strength by resolving relevant turbulent structures, which yields noticeably improved results. We discuss reasons for that and highlight the potential of transitional DDES.
Study on Dynamic Characteristics of Single-Span Rotor Under Cross-Coupling Stiffness Control on Non-Drive End
Authors: Ma Yuhang , Li Qihang , Yang Bowen , Zhang Rui , Wang Weimin , Yao Jianfei 
Published: August 2024

Abstract
The sealing-induced cross-coupling stiffness (CCS) often decreases the rotordynamic stability of turbomachinery. In our previous study, an active negative CCS control strategy applied between two bearings in the middle of the rotor was validated to enhance the stability of the rotor system. In this paper, a different approach was taken by applying both positive and negative CCS control strategies to the non-drive end, aiming to investigate their effects on rotordynamic stability using a rotordynamic model. The model represented a single-span centrifugal compressor rotor with CCS at the seal node. The logarithmic decrements and unbalance response of the rotor system were compared under different CCS applications at the non-drive end and in the span. The results demonstrate that applying both positive and negative CCS at the non-drive end can improve system stability, but the positive CCS stragety has limitations, and its applicability is not as extensive as negative CCS. A “critical stiffness” phenomenon emerges when the rotor system is actively stabilized at the non-drive end, resembling critical resonance. Furthermore, when components like seals introduce cross-coupling stiffness out of the span, they contribute to system stabilization. These findings provide valuable insights into actively enhancing the stability of rotor systems.
Computationally Lightweight Method for Campbell Diagram Plotting in High-Speed Electric Machines
Authors: Kurvinen Emil , Khadim Qasim , Ikäheimo Eero , Choudhury Tuhin , Jastrzebski Rafal 
Published: August 2024

Abstract
Campbell diagram is plotted from calculation results to identify a rotating object’s critical speeds. The Campbell diagram is formed by calculating the supported natural frequencies in a defined operation speed range. It is an important step when designing rotating machines, e.g., an integrated high-speed electric motor that can be sensitive to the rotor’s dynamical behavior. Currently, minimizing unnecessary calculation points is important for rapid design iterations and utilization of physics-based models with artificial intelligence. In cases where large variants of rotor geometry or using high-fidelity models, the calculation burden becomes high. In the research, a methodology based on a minimum number of calculation points and a second-order fitting equation is proposed, i.e., instead of using a high number of fixed calculation intervals, a three-point calculation methodology is proposed. The proposed methodology can be applied with neural network-based methods or implemented with high-fidelity models such as solid element models where the physics-based models can be used to create sensitivity to model parameters and study their influence with the traditional rotordynamics Campbell diagram tool. In the results, a comparison of two case studies is shown, and the computational cost is compared.
Transient Shutdown Cooling Simulation of a Gas Turbine Test Rig Configuration Under Ventilated Natural Convection
Authors: Sun Zixiang , Amirante Dario , Barnes Chris , Hills Nick , Fahy Daniel 
Published: August 2024

Abstract
A transient simulation of shutdown cooling for a gas turbine test rig configuration under ventilated natural convection has been successfully demonstrated using a coupled aero-thermal approach. Large eddy simulation (LES) and finite element analysis (FEA) were employed for fluid domain computational fluid dynamics (CFD) and solid component thermal conduction simulation, respectively. Coupling between LES and FEA was achieved through a plugin communicator. The buoyancy-induced chimney effect under the axially ventilated natural convection is correctly reproduced. The hotter turbulent flow in the upper part of the annular path and the colder laminar-type air movement in the lower part of the annulus are appropriately captured. The heat transfer features in the annular passage are also faithfully replicated, with heat flux of the inner cylinder reaching its maximum and minimum at the bottom dead centre (BDC) and the top dead centre (TDC), respectively. Agreement with experimental measurements is good in terms of both temperature and heat flux, and the result of the transient simulation for the shutdown cooling is encouraging too. In addition, radiation is simulated in the FEA model based on the usual grey body assumptions and Lambert’s law for the coupled computation. It has been shown that at the high power (HP) condition, the radiation for the inner cylinder is approximately 11% of its convective heat flux counterpart. The importance of radiation is thus clearly revealed even for the present rig test case with a scaled-down temperature setup.
Optimisation of Geometric and Operational Conditions of a Flywheel Energy Storage System to Minimise Standby Losses
Authors: Eltaweel Mahmoud , Herfatmanesh Mohammad Reza 
Published: August 2024

Abstract
Flywheel energy storage systems (FESSs) have gained significant attention as a promising technology for effective harvesting, storage and redeployment of energy. This technology is used particularly in renewable energy applications where they help manage the intermittency and variability of energy output from renewable sources such as solar and wind by providing quick response, high power density, and cycling stability without the degradation issues associated with chemical batteries. This paper presents a comprehensive study on the optimisation of geometric and operational conditions of a FESS, with the view to reduce standby losses hence improving the overall efficiency of the system. The effects of the following parameters are investigated; the working fluid, operating pressure and geometrical configuration of the FESS casing, using Computational Fluid Dynamics (CFD) simulations to provide insights into the system performance characteristics. This study investigates the effects of concave and convex casing shapes compared to conventional uniform cylindrical casings. The use of these distinct shapes can lead to lower standby losses. In addition, the effects of the working fluid and the operating pressure are investigated. The effects of different working fluids including air, helium and carbon dioxide, on standby losses are studied at different operating pressures. The findings of this study highlight the significant potential for improving FESS efficiency through the optimisation of FESS casing design and the use of a suitable working fluid at optimal operating pressure. Windage losses can be reduced by 90% compared to the base model, allowing the FESS to function as a medium-duration storage solution rather than a short-duration, which is often a limiting factor when considering FESSs as an alternative solution to battery storage systems.
Sensitivity Analysis of Simplified Labyrinth Seals Model Stability to Flow Hypotheses
Authors: Foschi Giorgia , Thouverez Fabrice , Blanc Laurent , Fiore Giuseppe , Pampolini Giampiero , Girard Patrick 
Published: August 2024

Abstract
Labyrinth seals are a widely used non-contacting mechanical subsystem of space engines turbopumps. Thanks to a sequence of teeth and cavities, they provide to the working flow a tortuous path limiting leakage and recirculation phenomena through rotor/stator gap and they guarantee more efficient engine performances. The high fluctuations of pressure and velocity experienced by the flow running through labyrinth seals, together with the necessity for light structures, make them subject to aeroelastic instabilities. This problem is object of in-depth investigations in order to prevent failures caused by fatigue and provide safer turbopumps. In this work, the analysis of a straight-through one-cavity labyrinth gas seal stability is conducted through the development of a Navier-Stokes one-dimensional fluid model monolithically coupled to an elastic structure model. To this end, a sensitivity study to the variation of different parameters is presented, with a particular focus on the role of the energy equation, the leakage flow formulation and, for a viscous flow, the shear stress model. This study allows to characterize the role that different assumptions and working parameters have on the stable/unstable behaviour of a labyrinth gas seal, under the hypothesis of a strong fluid-structure coupling. The achieved results show how the characteristic of the fluid modelling can be crucial for the accurate representation of the aeroelastic problem and how the choice of the leakage flow and friction coefficient model, together with the sizing of some geometric parameters, can have a decisive impact on the system stability.