bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of SiC Fiber Dispersion on the Mechanical Strength of SiCf/SiC Composites
Authors: Kim Soo-Hyun , Kim Seyoung , Han In-Sub , Bang Hyung-Joon , Seong Young-Hoon , Lee Seulhee 
Published: August 2024

Abstract
The present study examines the influence of fiber dispersion on the internal structure and mechanical strength of SiCf/SiC composites fabricated utilizing spread SiC fibers. The fiber volume ratio of specimens incorporating spread SiC fibers decreased by 9 percentage points compared to those without spreading, resulting in smoother impregnation of resin slurry between fibers and, consequently, minimizing matrix porosity. To assess and compare the fiber dispersion in each specimen, a method was proposed for quantifying and evaluating the separation distance between fibers in composite materials. The results revealed a 2.23μm increase in the distance between fibers in the spread specimen relative to the non-spread specimen, corresponding to a notable 42.6% increase in the distance between fiber surfaces. Moreover, a 3-point flexural test showcased a 49.3% higher strength in the spread specimen, coupled with a more uniformly distributed deviation in test data. These findings underscore the substantial impact of SiC fiber dispersion on achieving uniform densification of the SiCf/SiC matrix and enhancing mechanical strength.
Thermal Performance Assessment of High-Temperature Sensible Solid Thermal Energy Storage (SSTES): Various Designs, Storage Materials and Heat Transfer Fluids
Authors: Bangalore Mohankumar Malini , Unger Sebastian , Guille Alexandre , Carro Andres , Chacartegui Ramírez Ricardo , Hampel Uwe 
Published: August 2024

Abstract
Integration of energy storage (ES) into an energy system with wind and solar power plants provides a solution to the problem of power balancing resulting from fluctuating power output. One promising approach are Thermal Energy Storage (TES) systems, particularly Power-to-Heat-to-Power (PHP) systems, which have a low environmental impact compared to, e.g. lithium-ion or lead acid battery storage systems. Solid sensible TES (SSTES) stores excess electricity in the form of sensible heat, the solid medium being heated either directly or indirectly using heat transfer fluids (HTF). The benefit of SSTES systems is their simplicity due to no phase change nor chemical reactions involved, making them cost-effective and easy to maintain. However, applications of SSTES at high temperatures remain relatively unexplored and have limited deployment globally. Nonetheless, the aforementioned advantages make them suitable for high-temperature applications, provided the solid material selected exhibits higher temperature stability.
The paper proposes a concept where an SSTES is charged indirectly using an electrically heated working fluid. In particular, an SSTES coupled with a sCO2 power cycle is considered in this work. Candidates for the storage medium are typical materials being used in high-temperature applications, such as high-temperature concrete, firebricks, as well as novel ceramic waste materials from aluminium production, like ALFERROCK™. As heat transfer fluids (HTF), we consider helium (He) and carbon dioxide (CO2) in this study. The thermal performance of an SSTES was investigated for a storage capacity of 50 MWhth at temperatures up to 800 °C. To conduct the numerical analysis we developed a one-dimensional MATLAB model. The impact of geometry, flow rate, solid material configuration in the storage container, and heat transfer surface area on the heat transfer characteristics and efficiency of the thermal energy storage (TES) system must be considered. Therefore, this research work also includes an assessment of different STES designs. The temperature of the storage material during charging and thermal efficiency are presented based on the results.
Overall, a comprehensive thermal performance assessment based on various factors that influence the STES system was done. The comparative analysis of various materials, heat transfer fluids, and geometries allows for determining their impact on the TES design and operation. These findings are being used to further investigate the system with finer 3D numerical methods.
Advanced Power Management Strategies for Complex Hybrid-Electric Aircraft
Authors: Bermperis Dimitrios , Kavvalos Mavroudis D. , Vouros Stavros , Kyprianidis Konstantinos 
Published: August 2024

Abstract
Aircraft electrification for propulsion is a promising way to alleviate the negative environmental impact of conventional carbon-powered aviation. Inclusion of the electrical powertrain aims to enhance design freedom allowing for more efficient power systems and operational schemes. In this work a design space exploration is performed aiming to derive power management guidelines based on aircraft environmental performance. A 19-passenger commuter aircraft employing the series/parallel partial hybrid-electric architecture is examined. Two underwing-mounted turboprop engines are combined with a boundary layer ingestion fan mounted in the aircraft aft and powered by an electrical drive. The primary electrical energy source is a battery system. A multi-disciplinary framework is utilized, comprising modelling approaches for multi-point thermal engine design, physics-based electrical component sizing and performance, aircraft sizing, mission design, and environmental assessment. The investigation revealed that the reference designed hybrid-electric configuration with entry-into-service 2035-assumed technologies yields roughly 18% improvement in block consumption and emissions, but an 8% increase in maximum take-off weight, compared to its 2014 conventional counterpart. The design space exploration for an optimal power management scheme indicated a minimum ratio of 1:1.35 between cruise and design point hybridization power. However, even the optimally operated hybrid aircraft showcases worse environmental performance compared to the conventional design of same entry-into-service date. The investigation has revealed that the complex powertrain and hybrid architecture selected may be more suitable for larger class aircraft, with the accumulated performance benefits reaching the order of 5% for the hybrid designs explored under relaxed top-level constraints.
Comprehensive Analysis of Adiabatic Compressed Air Energy Storage and Gas Turbine Hybrid System With Thermal Integrations
Authors: Kim Hyerim , Kim Tong Seop 
Published: August 2024

Abstract
Combining an adiabatic compressed air energy storage (A-CAES) with a gas turbine (GT) can address any sudden changes in demand, but a comprehensive analysis of the integration effects between A-CAES and GT is needed. This study introduced a regenerative A-CAES-GT hybrid system with two thermal integrations: preheating and regeneration. These integrations resulted in an 11% increase in electric power and a 3%p increase in round-trip efficiency for the hybrid system compared to A-CAES and GT stand-alone systems. In addition, the hybrid system generated thermal power through thermal integrations, leading to a combined heat and power (CHP) round-trip efficiency higher than 60%. Various load control strategies for part load operation of the hybrid system were used and investigated. With a stable control strategy, optimal dispatch for the regenerative A-CAES-GT hybrid system was obtained, considering the environmental and energy-autonomy indices. The hybrid system revealed a 41% lower equivalent carbon dioxide emission factor (CEF) than the optimal dispatch for the A-CAES and GT stand-alone systems. Furthermore, the hybrid system showed a 4%p higher self-sufficiency under a low CEF of the grid and high demand.
The Study of Unsteady Plasma Excitation to Control Vortex Shedding Appears in the Turbine Cascade
Authors: Jianyang Yu , Weixiao Xie , Yining Zhang , Qifan Guo , Jinsong Shen 
Published: August 2024

Abstract
In this work, the flow fields of a T106A turbine cascade under different unsteady excitation conditions are simulated based on large eddy simulation (LES). Moreover, the primary flow patterns and the interactions between induced and original flow structures are analyzed using proper orthogonal decomposition (POD) method and vortex identify method based on triple decomposition of the relative motion near a point (TDM). The numerical results reveal that plasma excitation amplifies large-scale turbulent pulsations, making it locked to the excitation frequency, and effectively suppressing the small-scale turbulence pulsation in other modes. This excitation substantially weakens the vortex structures in the trailing region, which is the primary source of aerodynamic losses, leading to a notable improvement in the spatiotemporal flow field structure. Based on the above study, the improvement of plasma excitation control effect is explored though the influence of excitation frequency (Stδ) and duty cycle (Dtc). When Stδ is set at 0.8, the induced flow field exhibits better coupling with the vortex structures near the trailing edge, resulting in a remarkable 20.96% reduction in the total pressure loss coefficient compared to the baseline. For Dtc greater than 0.5, it enhances the control effect by extending the excitation time. Conversely, for Dtc less than 0.5, a shorter excitation duration results in a lower peak total pressure loss coefficient and an extended recovery time, surpassing the control effect of Dtc = 0.5.
An Enhanced Predictive Method for Large Droplet Breakage Based on the Discrete Particle Model
Authors: Hongyu Ju , Jianqin Suo , Yue Li 
Published: August 2024

Abstract
In high-speed flows, a single droplet undergoes fragmentation, yielding numerous child droplets. Conventional breakup models usually group these droplets into a single parcel, neglecting the post-breakup spatial distribution. To address this limitation, detailed numerical simulations have been conducted focusing on the bag and bag-stamen breakup modes of 200 μm-diameter droplet at Weber numbers of 15 and 30. The result shows that the largest length of the child droplets cloud can reach up to 29 relative to the original diameter. Importantly, if the grid size is less than 29 times the droplet diameter, traditional models that use a single parcel for child droplets could produce inaccurate results. To overcome this limitation, a disk-like breakup (DLB) model was introduced. With this model, multiple parcels replace the original droplet and are initialized on a virtual disk. Additionally, partitioned breakup modeling was employed for both bag and bag-stamen breakups. Calculations using the DLB model were compared with the TAB, KH-RT and ETAB models. The result indicates that the DLB model is capable of simulating the spatial distribution of the droplet cloud post-breakup, achieving better agreement with the detailed numerical simulations using the VOF method in this paper and experiments in the literature.
Investigation of Viscor and Methanol Spray Dynamics Using Proper Orthogonal Decomposition in Siemens Energy Industrial Atomisers
Authors: Alshahrani Ali , Mohni Izwan , Ajisafe Adesile , Furi Marc , Houde Michel , Sadasivuni Suresh , Engelbrecht Geoffrey , Bulat Ghenadie , Talibi Midhat , Balachandran Ramanarayanan , Ducci Andrea 
Published: August 2024

Abstract
The demand to reduce carbon emissions has prompted research into alternative fuels that can replace conventional fuels like diesel in industrial gas turbines. Among different potential biofuels and e-fuels, methanol emerges as a sustainable and high-performance alternative to diesel for gas turbine applications. It is well established that the fuel physical properties, spray dynamics and degree of atomisation are strongly correlated and affect the engine performance. In this study, Proper Orthogonal Decomposition (POD) was applied on spatio-temporally resolved images to characterise Viscor, here used as diesel surrogate, and methanol sprays of pressure-swirl atomisers employed in Siemens Energy industrial gas turbine (SGT-400) combustors. The methanol experimental results were then compared against Viscor results at analogous operating conditions, including density adjusted atomiser pressure drop and ambient pressures. Results confirmed that the methanol spray cone angle is slightly wider than Viscor at corresponding operating conditions. The POD analysis allowed to identify dominant spatial oscillation modes and characterise them in terms of oscillation amplitude, wavelength and onset distance from the atomiser edge for both fuels. Oscillation wavelengths and maximum amplitudes were found to correlate with Weber number, average SMD and axial jet velocities.
Large Eddy Simulation of Turbulent Reacting Flow in a Pressurized Annular Combustor
Authors: Kamin Manu , Plewacki Nicholas , Koneru Rahul , Bravo Luis , Khare Prashant , Powers Russell , Miki Kenji , Ham Frank , Senga Masayoshi 
Published: August 2024

Abstract
Large eddy simulations (LES) are becoming increasingly popular in engineering to predict complex physical interactions governed by the temporal dynamics of the flow. In the context of propulsion systems with realistic combustors, LES is the ideal choice for modeling complex processes involving multiphase transport, vaporization, and reacting flow physics that span a wide range of scales. However, simulations of a full annular combustor have historically remained out of reach due to the steep cost associated with resolving the energetic scales in systems with such exceedingly complex geometries. Fortunately, with recent advances in supercomputing capabilities, such simulations are now possible and can be used to understand the underpinnings of combustion physics at scales that are often unavailable to experiments. Thus, the objective of this study is to investigate the ability of LES to predict turbulent combustion subject to system-level effects by considering a 360-degree annular combustor from the Energy Efficient Engine (EEE) program. In addition to showcasing LES calculations of the annular combustor, this study investigates the effects of incorporating a complex geometry on predicting self-sustaining oscillatory flows and its impact on combustion. To accomplish this, the massively parallel LES solver, CharLES, is employed, which utilizes a fully compressible Navier-Stokes Equation (NSE) solver and a flamelet progress variable approach on unstructured Voronoi-based cells. Due to the importance of estimating adequate grid size, the effect of mesh resolution is investigated by computing results on three grids and comparing results in terms of mean and fluctuating fields. A non-reacting analysis is first conducted to understand the unsteady fluid dynamics arising from the central recirculation zone, which plays an important role inflame stabilization. Next, the progress variable method is utilized to generate a combustion model coupled with Lagrangian particle tracking models for fuel spray breakup, vaporization, and ignition. The results, when compared to combustor exit temperature measurements from experiments, as well as previous LES simulations in the literature, show good agreement. Further analysis is conducted showing the onset of self-sustained oscillatory flow, owing to the azimuthal coupling, and proper orthogonal decomposition (POD) analysis shows the most energetic modes. Overall, the results are promising and present a novel tool for guiding the development of stable and reliable systems. This work is conducted in support of the DoD High Performance Computing Modernization Program (HPCMP) Frontier program at ARL and NAVAIR in collaboration with the University of Cincinnati, Cadence Design Systems, and Pratt & Whitney.
Design, Analysis, and Experimental Testing of Hydrogen Lean Direct Injection Nozzles at Elevated Pressure
Authors: Overbaugh Malcolm , McDonell Vincent , Buelow Philip , Ryon Jason , Williams Brandon , DeBeni Ottavio 
Published: August 2024

Abstract
There are many challenges of commissioning a hydrogen combustor into future gas turbine engines; especially regarding achieving emissions goals. Previously, Escudero et al. and Tran et al. conducted a study to adapt the liquid fuel Lean Direct Injection (LDI) concept from Jet-A to gaseous natural gas-hydrogen blends and pure hydrogen [1], [2]. Experimental data was collected at atmospheric conditions using a Box Behnken design of experiments. The design of experiments suggested that biasing the air split in favor of the inner air circuit and increasing the swirl strength of this inner air passage resulted in improved NOx emissions, while the inverse was true for stability, which was quantified by studying the lean blowoff point (LBO) [1], [2]. The trends revealed by the original experiment [1], [2] provided a design direction for further iterations of the experimental hardware. The study presented herein describes the further investigation of such LDI injectors through experimental methods and computational fluid dynamic (CFD) simulations at atmospheric conditions, which were used to identify potential flow behaviors driving enhanced emissions performance. Further evaluation of select injectors from both studies was then conducted at elevated pressures up to 6 atmospheres. The results from both experiments are presented in this study, which include flame observations, emissions measurements, and operational challenges. NOx emissions results are reported on a volume basis in ppmvd corrected to 15% O2 and corrected for fuel. A predictive model for relating NOx emissions to test conditions at atmospheric conditions show high significance to adiabatic flame temperature while little to no significance to fuel composition for the best performing configurations. The results illustrate the connection between atmospheric testing and testing elevated pressures. The design direction indicated by the initial tests and CFD results in promising configurations for implementation into a Multi-point LDI array.
DNS of Turbine Vanes Subjected to Inlet Temperature Variations and Robust Quantification of Aerothermal Flow Irreversibilities
Authors: Nardini Massimiliano , Kozul Melissa , Sandberg Richard D. 
Published: August 2024

Abstract
The aim of the present work is to investigate the aerothermal characteristics of high-pressure turbine (HPT) vanes subjected to burner-like mean inlet temperature and velocity variations. A systematic numerical investigation is carried out by means of Direct Numerical Simulation (DNS). A total of five cases are simulated: two non-uniform pitchwise inlet temperature distributions (hot streaks) with different clocking positions, one impinging on the blade leading edge and the other aligned with the mid-passage, two equivalent non-uniform pitchwise temperature and velocity distributions (hot jets), and a baseline with uniform inlet conditions. In all cases, large-scale turbulent fluctuations are superposed onto the mean inlet profiles. A robust methodology to correctly quantify viscous and thermal irreversibility production mechanisms based on an alternative formulation of the entropy transport equation is introduced. This ensures a correct representation of the turbulent dissipation and of the irreversible turbulent heat flux in the presence of incident fluctuations and thermal gradients. The critical role of turbulent dissipation and its sensitivity to the grid resolution due to small-scale turbulent fluctuations are discussed. The role of inlet conditions on the vanes’ aerothermal properties is investigated by analyzing the surface temperature distributions and the characteristics of the boundary layers. The temperature streak clocking positions are shown to directly affect the blade surface temperature distributions, and have an impact on the shock waves position and on the boundary layer transition characteristics via local modifications of the fluid viscosity and Mach number. The novel entropy framework is carefully validated and it is employed to investigate the role of viscous and thermal irreversibilities and their dependency on inlet conditions. Furthermore, an in-depth analysis of the mean and turbulent physical mechanisms of entropy generation associated with distinct regions of the flow such as boundary layers, wakes and passage is conducted and the results are discussed.
Generative Deep Learning on Images of Thermo-Mechanical Simulation Results
Authors: Nasti Adele , Voutchkov Ivan , Keane Andy 
Published: August 2024

Abstract
This paper presents a novel methodology that combines engineering simulation and machine learning for the thermomechanical design of a secondary air system double-sided seal in an aero engine turbine subassembly. Secondary air system seals are crucial in aero engine design as they have a direct impact on specific fuel consumption.
The study uses an automated analysis workflow to generate a large dataset of images embedding key design and performance attributes for the seals, such as running clearances at key operating conditions. These images are used to train a conditional Generative Adversarial Network (cGAN), which can then be used for design exploration or optimisation. The paper introduces a unique approach to encoding and decoding these images, enabling automatic quality monitoring of the generated images and training processes, as well as extraction of targeted results.
The predictability of the Deep Learning models is assessed, demonstrating how this methodology can generate designs in targeted categories and can support decision making both in the preliminary design phase, to enable classification of ‘good’ and ‘bad’ designs, and in the detailed design phase, to support optimisation and robust design. Beyond design, these methods can also be used to support the implementation of the Digital Twin.
An Optimal Design of Aircraft Hybrid Powertrain Based on a Coupled Method
Authors: Qiang Xuankai , Qian Yuping , Li Weifeng , Jiang Hongsheng , Zhuge Weilin , Zhang Yangjun 
Published: August 2024

Abstract
Hybrid aircraft can better meet the future needs of green aviation. The range and payload of battery electric aircraft are limited by the low energy density of the battery. Gas turbine hybrid systems can reduce the battery weight and increase the range and payload. In the engineering design aspect, how to select the optimal gas turbine power at design point and determine suitable off-design output power characteristics at different flight phases based on a specific mission profile is a worthy research topic.
This paper presents a coupled optimization method for hybrid powertrain. Firstly, a component model of the gas turbine generator system and a battery model based on test data are established. Secondly, A design point power optimization method based on the bisection method is proposed. Further, an off-design output power optimization method based on the particle swarm optimization algorithm is also established. Based on the maximum and minimum output power capability of the gas turbine, a general table of numerical results of the non-linear equations is generated to accelerate the calculation of the off-design points based on the flight mission. Finally, based on the mission profile of NASA-X57, this paper designs the corresponding hybrid power system and compares its performance with the battery electric system, and the results show that the aircraft with optimized hybrid powertrain could increase the efficient payload (people and cargo) by 25%, the specific transportation cost (RMB/kg/km) is increased by 19%. The method proposed in this paper could provide a fast optimal design and performance evaluation of the hybrid powertrain based on a certain flight mission profile, which could provide the aircraft and powertrain manufacturers an efficient design tool.