bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimization of a Propeller Fan for Noise and Efficiency by Using 3D Inverse Design Method
Authors: Zhang Luying , Dinh Thien Xuan , Kawakita Kenji , Riddell Alfred , Goto Akira , Zangeneh Mehrdad 
Published: August 2024

Abstract
In this work, a methodology for propeller fan optimization using the three-dimensional inverse design method is presented. The workflow is demonstrated through the optimization of a previously designed propeller fan, the performance of which has been numerically and experimentally studied. The vortex distribution, the pressure loading on the blade surface and the stacking were varied during the optimization. The 3D blade geometries were obtained from the inverse design calculation, which can explore a large design space with relatively small amount of input parameters. This leads to some advantages when using a design of experiments (DOE) approach. The aim is to improve the aerodynamic performance of the fan. Meanwhile, the noise level should be kept under control. A multi-objective optimization was carried out based on the DOE results to find the balance between conflicting objectives. An optimum design was picked from the optimization. The performance of the optimized design was then verified by computational fluid dynamics simulations. The results show an increase of peak efficiency and pressure rise. The low flow rate performance is also improved. The flow physics that led to the performance improvement are discussed based on the numerical results. The same optimization workflow and principles can be applied to other types of axial fan as well.
Numerical Assessment of an Aerodynamic Probe to Enable Short Focal Length Laser Diagnostics in High Temperature Supersonic Flows Based on Flow Disturbance
Authors: Lasala Ignacio , McKelvy Aubrey , Braun James , Paniagua Guillermo , Choquet Etienne , André Thierry , Falempin Francois 
Published: August 2024

Abstract
This manuscript evaluates the use of an actively cooled aerodynamic probe body with integrated optics to perform short focal length laser diagnostics within high-temperature, high-supersonic flows. A novel probe with a “ship’s bow” shape and an open cycle cooling scheme ending in a matrix of effusion holes is presented. The flow around the probe is studied numerically using 3D Steady Reynolds-Averaged Navier-Stokes (RANS) simulations at Mach 6, with free stream total conditions of 1700 K and 44.2 bar. The laser trajectory is calculated using the ray propagation equation to ensure that it deviates minimally while going through regions of gradients in refractive index. The location and shape of the detached shock formed ahead of the probe is extracted, and the minimum focal length achievable for measurement of the undisturbed flow-field is determined. The sensitivity of the bow shock shape to changes in cooling pressure between 1.33 and 1.835 bar, and to blocked holes has been computed. Finally, the flow through the effusion system of the probe is tested experimentally, ensuring its proper operation, and checking the consistency of the effusion boundary conditions used in the numerical study.
The Effect of FELTMETAL™ Porous Transport Layer Structure on Performance of Anion Exchange Membrane Water Electrolyzers
Authors: Motyka Elaine , Volpe Erin , Roeseler Stefan , Plessinger Ryan , Noyes Tyler , Li Chenyu , Park Habin , Kohl Paul , Mustain William , Kweder Jonathan 
Published: August 2024

Abstract
The porous transport layer (PTL), or gas diffusion layer (GDL), is a critical component in the performance of anion exchange membrane water electrolyzers (AEMELs) for hydrogen production and hydrogen supply. This work focuses on how the structure of FELTMETAL™ (FM) affects the critical functions of the oxygen evolution reaction (OER) electrode in an AEMEL. As a sintered-particle material with high levels of open pores, FM has high total porosity which positively affects mass transport of the gas and water from the PTL but increases the electrical resistivity and contact resistance. Due to the nature of the high-aspect ratio particles in FM, it also has high surface area which improves electrical properties and enables high current density during AEMEL operation. However, sintered materials typically have a trade-off between total porosity and pore size which can lead to mass transport issues if the pore size and distribution are too tight. Previous experimental electrolysis work determined that increasing the %-density of FM from 18%-density to 60%-density favorably increased current density at a given applied voltage, but it was likely that mass transport issues related to bubble formation and removal caused variation in performance and a decrease in current density over time. This work ultimately aimed to determine the effect of particle size on the structure of the FM PTL (pore size, total porosity, surface area) on AEMEL performance (current density, applied voltage, voltage stability over time, overpotentials). The study evaluated OER PTL FM with distinctly different %-densities and particle size distributions of Ni-alloy HastelloyX. The structures were characterized by metallography and bubble point testing. The AEMEL performance was characterized by polarization and electrochemical imprudence spectroscopy (EIS). Because the work focuses on the OER PTL structure, other key components of the experimental AEMEL were not varied, using standard commercial materials. It was found that the using a finer particle size distribution had a significant positive effect on polarization responses, specifically voltage at 1A/cm2, steady state voltage, and activation overpotential. The finer particle structure likely has increased total pore number and area-% open pores. It is possible that FM PTL materials comprised of finer fiber can enable performance improvement at a lower %-density, reducing the material required to make the PTL.
Multidisciplinary Design Optimization With Multiple Degrees of Freedom for an Axial Compressor Based on Data-Driven
Authors: Luo Chuwei , Chen Jiang , Liu Yi , Xiang Hang 
Published: August 2024

Abstract
Compressor design represents a multidisciplinary coupling problem encompassing aerodynamics, structure strength, vibration, fatigue, and acoustics. Multidisciplinary design optimization enables a comprehensive consideration of the interconnectedness among these disciplines, reasonably balances the conflicting requirements, and ultimately enhances the performance of products significantly while reducing the development cycle. In this paper, a multidisciplinary optimization system is established based on a data-driven multiobjective evolution algorithm. This algorithm is combined with the directly manipulated free-form deformation method to achieve multi-degree-of-freedom parameterized control. The research focuses on optimizing the aerodynamic and aeroelastic design of a 1.5-stage axial flow compressor in a gas turbine. Maximum efficiency and surge margin are set as the optimization objectives, while the constraint conditions involve flow rate, total pressure ratio, as well as the strength and resonance margin of the rotor blade. To improve the prediction accuracy of surge margin during optimization, a successive approximation method combined with efficiency-based residual convergence determination is utilized. The results show a significant reduction in the stress distribution of blades, with the maximum stress value decreased by 30.6%. Simultaneously, the surge margin of the compressor is increased by 3.36%, and the efficiency at the design point is also slightly improved. The optimization system can not only ensure optimization effectiveness, but also greatly reduce the design variables and evaluation time, which is effectively applicable to the multidisciplinary design optimization of compressors.
Windage Characteristics of a Compressor Stator Well Cavity
Authors: Erdem Erinc , Kahraman Ahmet Cuneyt , Garip Onur , Sal Sinan 
Published: August 2024

Abstract
This article aims at the investigation of a generic compressor stator well cavity flowfield of a high pressure compressor stage. Swirl ratio, static pressure distributions are thoroughly investigated together with windage power for three different engine thrust levels and three different clearance levels at high thrust cases. An experimental test case from Kong et. al [3]–[4] has been selected to validate the numerical method at five rotational speeds and two pressure ratios employing measured/predicted labyrinth seal clearances. One-dimensional cavity solver with three cavity approach is also employed to compare the results with experimental data. Contrary to a rotorstator cavity with radial inflow, stator well cavity flow displays a reduction in swirl ratio throughout the entire well and increase in windage power loss with higher λT, essentially with more flow. This is because well cavities are too shallow and located at high radii with low swirl leakage inflow, where torques dominate and dictate swirl distributions. Upstream cavity on the right hand side of the seal and labyrinth seal cavity are found to determine the windage power loss and associated temperature rise. The effect of downstream cavity located on the left hand side of the labyrinth seal is found to be less important.
Techno-Economic Analysis of the Solid Oxide Semi-Closed CO2 Cycle for Different Plant Sizes
Authors: Martinelli Matteo , Campanari Stefano , Martelli Emanuele 
Published: August 2024

Abstract
This work presents a detailed techno-economic evaluation of the SOS-CO2 cycle, a hybrid semi-closed cycle with solid oxide fuel cells developed by Politecnico di Milano. for different plant sizes, ranging from large utility plants (400 MWel) to industrial applications (50 MWel). The analysis includes the design and sizing of all the cycle components, including specific design optimization models for the most critical cycle components such as the regenerative heat exchanger and the turbine. Results are compared with the performance of the Allam cycle, an oxy-combustion cycle with higher technology readiness level. The results show that the SOS-CO2 cycle maintains high efficiency over the whole size range thanks to the modularity of the fuel cell and the regenerator which counterbalances the decrease in turbomachine efficiency at small sizes. For the utility scale plant, despite its higher specific investment cost (3761 €/kW vs. 2490€/kW), the SOS-CO2 cycle appears to be competitive with the Allam cycle in terms of cost of electricity (128.4 €/MWh and 127.8 €/MWh of the Allam cycle) thanks to its higher efficiency (68.9% vs. 53.1%). At smaller sizes, the higher efficiency and the lower dependance on the economies of scale make the SOS-CO2 more economically advantageous: for the 50 MWel plant, the cost of electricity of the SOS-CO2 is 175.8 €/MWh vs. 205.8 €/MWh of the Allam cycle.
The Purdue High-Speed Small Core Turbine Facility
Authors: Bhatnagar Lakshya , Castillo Sauca Antonio , Sanchez de la Rosa Diego , Paniagua Guillermo , Clemens Eugene , Bloxham Matthew 
Published: August 2024

Abstract
Short-duration facilities, with testing time on the order of milliseconds to seconds, offer cost-effective solutions to achieve engine-relevant pressure and temperature ratios. Short-duration facilities have high levels of heat loss that require careful accounting for efficiency calculation[1]. The Purdue Small Turbine Aerothermal Rotating Rig (STARR) was developed to test engine-representative hardware for small core turbine applications. The STARR facility is a two-stage rotating test turbine running at engine-representative Reynolds and Mach numbers capable of fast transients and steady operation for up to 6 hours with the enhanced pressure vessels in development. The facility is purpose-built to test advancements in critical technologies for clean aviation, pushing towards higher OPR engines, hybrid propulsion, and multi-stream engines. The facility is designed to be modular, allowing faster turnaround times for new test articles. This paper presents the design, control, and operation of the facility. Efficiency measurements in engine-representative test rigs are a challenging prospect due to the narrow uncertainty band required, ideally less than 0.5% uncertainty, to detect the incremental improvements achieved by turbine designers. For a small core turbine, accurately quantifying the tip clearance is also critical to assess relative changes in performance. To that end, the instrumentation used for efficiency measurement and resolving unsteady flow phenomenon is presented. The inlet characterization and commissioning of the test section are presented. Uncertainty is quantified on efficiency measurement through a comprehensive framework [2] that includes both precision and absolute level of uncertainty. The uncertainty is propagated from the individual sensor to the final efficiency calculation. The total uncertainty for mechanical efficiency presented is of the order of 0.55%. The challenges faced in the operation of such a facility are highlighted, along with the steps proposed to mitigate them.
Blowoff Characteristics of a Bluff-Body Stabilized, Multi-Element, Lean Premixed Pre-Vaporized Combustor for Supersonic Transport Applications
Authors: Passarelli Mitchell L. , Wonfor Samuel E. , Zheng Andy X. , Mazumdar Yi , Steinberg Adam M. , Bower Hannah , Hong John , Venkatesan Krishna 
Published: August 2024

Abstract
This work explores the flame stabilization and blowoff characteristics of a novel lean premixed pre-vaporized (LPP) combustor design for potential commercial supersonic transport (CST) applications. CST operating conditions involve higher combustor inlet temperatures and lower inlet pressures than encountered in conventional subsonic aeroengines. Additionally, the LPP combustor investigated in this work is a multi-element subsonic flow design, with four bluff-body stabilized, annular “main” flames surrounding a central, swirl-stabilized pilot flame. Existing blowoff studies have not explored the combined effects of multi-element flames with varying temperature and pressure simultaneously. This work presents experimental analysis of the conditions that lead to blowoff in such a combustor. The experimental data consists of simultaneous pressure fluctuations, high-speed OH* chemiluminescence imaging and low-speed kerosene planar laser induced fluorescence imaging. The operating conditions for each data set were used to evaluate the Reynolds number (Re) and Damköhler number (Da). Plots of Da versus Re indicate that the Da at blowoff is lower than that reported in literature for flames stabilized on axisymmetric bluff bodies. It is hypothesized that the observed trend is due, in part, to the presence of the central pilot flame which breaks the axisymmetry of the individual main flames and acts as an ignition source for low Da conditions. An investigation of a case with intermittent blowoff reveals the presence and effects of unforeseen hysteresis in the combustor.
Semi-Closed Oxy-Combustion Combined Cycles (SCOC-CC) for Combined Heat and Power Applications
Authors: Zelaschi Andrea , Giostri Andrea , Chiesa Paolo , Martelli Emanuele 
Published: August 2024

Abstract
This study focuses on the design and comparison of three utility-scale combined heat and power (CHP) cycles with carbon capture and storage (CCS): (i) a CHP semi-closed oxy-combustion combined cycle (SCOC-CC), (ii) a CHP natural gas combined cycle (NGCC) with post-combustion CCS, and (iii) a CHP NGCC with post-combustion CCS and supplementary firing. Performance evaluations are conducted at the design point and partial load (gas turbine at 30%) for different exports of high-temperature pressurized steam. The comparison is extended against two reference separate production systems with CCS, one based on post-combustion technologies, and another based on oxy-combustion. Simulations of the H-class gas turbines are performed using GS, a specific in-house validated software, while the heat recovery steam cycle is modelled using Thermoflex. The CO2 capture processes employ validated models in Aspen Plus. The results highlight the suitability of the SCOC-CC for CHP applications, demonstrating superior performance and flexibility compared to CHP post-combustion technologies at both nominal and minimum loads. The SCOC cycle achieves a maximum first-law efficiency of 65.95%, outperforming CCS technologies that generate electricity and heat separately and enabling fuel savings up to 9.2%.
Dynamic Response of a Rotor Supported on Hybrid Bearings in Air, Water, and Liquid Nitrogen: Measurements and Comparisons to Predictions
Authors: Yi Howon , Kim Kyuman , Jung Hyunsung , Ryu Keun 
Published: August 2024

Abstract
Modern liquid rocket engine turbopumps implement hybrid bearings, which combine hydrostatic and hydrodynamic fluid film principles, in compact and lightweight units known for their superior reusability, durability, and reliability. This study aims to provide extensive and reliable test data for the purpose of anchoring and benchmarking predictive tools for these bearings. This paper provides comprehensive dynamic response measurements of a rotor weighing 10.40 kg and approximately 60 mm in diameter at the bearing locations. The test rotor is supported on two hybrid journal bearings with a bearing length to bearing diameter ratio of approximately 0.42 and a bearing radial clearance to rotor radius ratio of around 0.0017. The bearings are tested with air, water, and liquid nitrogen, serving as surrogate test fluids for common propellants in liquid rocket engines. Rotor run-up and speed coast-down tests are conducted to measure shaft motion responses. The results clearly demonstrate that the rotordynamic characteristics of the test rotor supported on the hybrid journal bearings largely rely on properties of the test fluids and their feeding conditions. Notably, when air is pressurized into the test bearings, the shaft motion responses differ markedly from those observed with water and liquid nitrogen, primarily due to significantly lower stiffness and damping coefficients. Furthermore, rotor speed coast-down tests for each test fluid exhibit notable differences in coast-down speed over time characteristics, depending on the test fluid properties. The predicted rotor imbalance responses exhibit excellent correlation with the measurement data. The steady increase of demand and growth of the fluid film bearing technology for reusable rocket engines require accurate bearing design tools, the extensive component testing, and the implementation of the technology. The validated and developed bearing predictive models from previous research demonstrate well the characteristics of bearings under various operating fluids conditions. The findings and database presented in this work contribute not only to comprehending the performance of hybrid bearings but also to understanding and enhancing the dynamic characteristics of rotor systems supported by hybrid bearings.
The Effect of Mixture Variation and Initial Temperature on the NH2* Thickness of Spherically Propagating Laminar Ammonia Flames
Authors: Almarzooq Yousef M. , Hay Matthew , Mathieu Olivier , Kulatilaka Waruna D. , Petersen Eric L. 
Published: August 2024

Abstract
Interest in ammonia (NH3) in combustion has increased in recent years as a carbon-free fuel alternative. Therefore, understanding its combustion characteristics is crucial. One way to increase the knowledge of ammonia combustion is by investigating the flame zone of a laminar flame. Using a high-spatial-resolution flame zone measurement technique developed by the current research group, the flame zone of different NH3-containing mixtures was measured experimentally. Those measurements were achieved by investigating spherically propagating flames using a chemiluminescence imaging diagnostic with the focus on NH2* profiles. The effect of the fuel mixture on the profile shape was investigated by examining two different mixtures. The first was an oxy-ammonia mixture consisting of NH3 + oxygen-enriched oxidizer where the oxygen (O2) concentration was varied from 25% to 40%. The second was a blend of NH3-H2 where the NH3 concentration (XNH3) was varied from 0.5 to 0.8. Additionally, the effect of the initial temperature was investigated by varying it from 293 to 373 K for three different mixtures, namely NH3 + (35% O2 + 65% N2), (0.7 NH3 + 0.3 H2) / air, and (0.45 H2 + 0.4 NH3 + 0.15 N2) / air. In all investigated mixtures, the initial pressure was fixed at 1 atm and the equivalence ratio was fixed at Φ = 1.0. The study revealed that increasing the O2 concentration in the oxy-ammonia mixture produced thinner flames. On the contrary, increasing the XNH3 in the NH3-H2 blend produced slightly thicker flames. Varying the initial temperature has two different responses for the three designated mixtures. In the oxy-ammonia mixture and the NH3-H2 blend, increasing the initial temperature resulted in the flame being thinner. On the other hand, increasing the initial temperature produced a slightly thicker flame for the H2-NH3-N2 blend. The predicted NH2* profile thicknesses from chemical kinetics agree with the measurements except for the H2-NH3-N2 blend, where the kinetics model underpredicted the thickness by a significant difference.
sCO2 Cycle Selection for Waste Heat Recovery From Aircraft Engine
Authors: Vesely Ladislav , Andress William , Paniagua Guillermo , Otto Marcel , Kapat Jayanta , Bury Claire-Phonie 
Published: August 2024

Abstract
The reduction of emissions for any sector, such as aviation, can be done via alternative fuels (i.e., direct approach) and/or utilization of waste heat (i.e., indirect approach). With an indirect approach, waste heat recovery (WHR) systems can provide onboard electrical power and eliminate or reduce the need to produce electrical power with other systems. An engine with a WHR system could potentially produce similar power/thrust with less fuel consumption. WHR systems could have additional benefits for the engine core and bypass flow. This work is focused on the sCO2 power cycle selection for a potential WHR system for an aircraft engine based on a Leap-1B engine using H2 as the working fuel and NH3 as a fuel carrier. Several sCO2 power cycle layouts are investigated for each case, including simple, recuperative, re-compression, precompression, and split expansion. Optimization of the selected cycle layout for the maximum power requirement and heat availability to transfer to the NH3 line or bypass is performed. The results show potential benefits and disadvantages of each cycle layout and demonstrate that the WHR system can meet the 180-kW power generation requirement for the airplane and still provide significant heat to the NH3 line or bypass flow.