bluuebunny/crossref_metadata_2025_split huggingface dataset:
Creep Lifetime Prediction of Alloy 617 Using Black Box Machine Learning Approach
Authors: Hossain Md Abir , Stewart Calvin M. 
Published: August 2024

Abstract
This study explored the application of black box machine learning (ML) to build high throughput models that predict the creep response of Ni-based Alloy 617. Black Box ML refers to highly complex machine learning algorithms that generate outputs from inputs without an interpretable internal process. The rapid implementation of suitable heat of alloys into targeted service is impeded by the extended qualification process involving chemistry-processing-structure-performance assessment. The ASME B&PV Code III outlines the requirement of 10,000 hours of creep testing before each heat can be qualified for service and 30,000 hours for heats that exhibit metastable phases. There is a critical need to shorten the development-to-deployment timeline for heats of an alloy at specific applications. Recent advancement in ML offers the ability to identify correlations in data which is difficult to elucidate by other approaches. To that end, black box ML is employed to expedite the HEAT qualification of Alloy 617 and predict performance from HEAT chemistry out to an unprecedented timescale.
In this study, creep data for Ni-based alloy 617 — a solid solution strengthened material is gathered from a wide range of data sources. The alloy chemistry, phases, precipitates, and microstructural features are analyzed to obtain the key strengthening mechanism. Service conditions, mechanical properties, chemistry, and chemical ratios are provided as potential input features. The Pearson Correlation Coefficient with a 95% confidence bound is employed for input feature screening where poorly correlated inputs are eliminated to speed up the ML process and prevent under- and/or over-fitting of predictions. In the ML algorithm, the selected input features are regarded as predictors, and rupture is regarded as the response. An algorithm evaluation is performed where 20 ML algorithms are trained with the training set. The 3-layered Neural Network (NN) was observed to be the best algorithm for the given data based on statistical rationale. The NN accurately predicts rupture across a range of isotherms and data sources. The interpolative and extrapolative predictions are in compliance with ECCC V5 guidelines. A post-audit validation exhibits neither under- nor over-fitting and confirms the applicability of NN algorithms to unseen data. The black box ML provides a pathway to predict the performance directly from chemistry and opens avenues to rapid heat qualification.
Application of CFRP Sleeve to Increase Efficiency of Air Compressor for Fuel Cell Electric Vehicle
Authors: Lee Changha , Lee Jongsung , Yang Hyunsup , Lim Jeong Kyu , Ko Young Yoon , Park Jeong Hee , Dong Seung-jin 
Published: August 2024

Abstract
This paper presents the analysis and experimental results of the application of a composite material (CFRP) sleeve to the rotor for enhancing motor efficiency measurements in the highspeed motor of an oil-free air compressor for fuel-cell electric vehicles (FCEVs). Carbon Fiber Reinforced Plastic (CFRP) applies two or more types of materials for better properties: high strength and lower density. The predicted motor loss at the maximum speed of the oil-free air compressor compared the sleeve performance of each sleeve between Inconel718 and CFRP. The eddy current loss of the CFRP sleeve rotor decreased by 90% compared with that of the previously developed rotor. Rotordynamics model predictions of the two types of sleeves manufactured benchmark the test data. The 1st bending natural frequencies of the CFRP sleeve rotor decreased by 15% against the Inconel718 sleeve rotor. In addition, this study compares the analyses of 2D and 3D models. The results show that the CFRP has low isotropy compared Inconel718 sleeve rotor. This trend is the same as that observed in the experiments. The CFRP sleeve was made by the prepreg of T300-class carbon yarn and epoxy resin, which are commonly used, and was molded using autoclave equipment. It satisfies a 1.5 mm thickness through 8Ply rolling. A series of rotor impact tests were conducted to compare the 1st bending natural frequencies of the previously developed sleeve rotors; Inconel718 and CFRP sleeves. The impact test showed that the CFRP sleeve rotor exhibited different 1st bending natural frequencies depending on the high-temperature and room-temperature conditions, and the range of change was larger than the Inconel718 sleeve rotor. The impact test results at room temperature showed a 25% decrease compared to the Inconel718 sleeve rotor. A previously mass-produced compressor was used in this experiment. Our performance evaluation equipment measured the performance and efficiency of the test compressor. A series of compressor performance and saturation tests at 80k and 90k RPM indicate that the CFRP sleeve results in an efficiency increase of 2% and an 8% decrease in the operating temperature. However, the CFRP sleeve rotor needs to be further improved to increase the operation speed (up to 90kRPM) of the high-speed motor of the oil-free air compressor.
Advancements in Wall Film Thickness Measurement Under High Pressure and High Temperature Conditions for Gas Turbine Applications
Authors: Yin Zhiyao , Lammel Oliver , Lückerath Rainer , Ax Holger , Poulios Dennis 
Published: August 2024

Abstract
In pursuit of quantitative measurements of liquid wall film thickness under high-pressure and -temperature conditions, a novel image processing approach in combination with a standard laser-shadowgraphy setup was developed and demonstrated for the first time at the high-pressure combustion test rig (HBKS). The wall-film extraction technique was validated against a laser triangulation sensor under laboratory conditions for film thicknesses in the range of 100–800 μm. It was then applied to detailed shadow images of liquid fuels (kerosene and light heating oil) and water spray impingement onto a long metal plate in a jet-in-crossflow configuration at 10 bar. After reaching a maximum thickness of about 680 μm, the kerosene film diminished completely prior to reaching the end of the metal plate. In comparison, the water film exhibited a delayed onset on the metal plate but grew steadily and persisted at a thickness of above 600 μm. Injection of kerosene emulsified with water at a 1:1 mass ratio also resulted in a persisting liquid film until the end of the metal plate. In the latter two cases, substantial quantity of liquid exited the spray chamber in the form of film and spray particles.
Performance of Ammonia/Methane Combustion in an RQL Combustor
Authors: Sun Jihao , Zhao Ningbo , Luo Shaowen , Zheng Hongtao 
Published: August 2024

Abstract
To gain a comprehensive understanding of the combustion characteristics of CH4-enhancing NH3 combustion in an industrial RQL gas turbine combustor, a numerical study was conducted using the CFD-CRN method. The study investigated flow and temperature distributions, flame structures, and NOx formation characteristics. Two methods of introducing CH4 were examined: premixing with NH3 before burning, and direct introduction in the inner swirl stage without premixing with NH3. The results revealed that NH3 combustion displayed a longer flame and higher NOx emissions compared to methane combustion. NOx was mainly generated at the flame front and the primary combustion zone. The addition of CH4 was found to increase combustion efficiency without significantly altering the flow and temperature distributions. Direct introduction of CH4 showed higher combustion efficiency compared to the premixing method. Moreover, the addition of CH4 contributed to an increase in NOx emissions. The direct introduction of CH4 in the inner swirl stage demonstrated promising results for NH3 combustion. This approach enhanced combustion efficiency and reduced NOx emissions without requiring fuel premixing systems.
A Comparison of Model Predictive Control Architectures for Application to Electrified Aircraft Propulsion Systems
Authors: Hill Elyse D. , Simon Donald L. , Connolly Joseph W. 
Published: August 2024

Abstract
As electrified aircraft propulsion (EAP) systems continue to mature, more sophisticated hardware and software are being developed to balance operations among electric machines and gas-turbine engines. In hybrid-electric propulsion systems, the increased complexity resulting from integrating turbine-engine shafts with electric machines necessitates control methodologies to account for various physical domains. Ideal controllers for hybrid-electric engines manage systems, subsystems, and their interactions in a coordinated fashion, able to account for safety and performance goals while being computationally efficient. In a previous work, linear model predictive control (MPC) schemes were implemented in centralized and distributed frameworks on a nonlinear turbofan engine model as a proof of concept. However, these schemes were not evaluated for computational complexity, prompting further study. The research presented here develops hierarchical MPC schemes to reduce the computational burden of the previous MPC schemes. A two-tier framework is implemented, where a slower sampling MPC controls electric machines and determines fan-speed tracking goals for a faster sampling controller, which is either a MPC or a proportional-integral (PI) controller. The proposed designs are compared to the centralized MPC investigated previously, and performance is measured via fan speed tracking error, energy storage state-of-charge, and computation time. Results reveal that the hierarchical MPC scheme employing a lower-level PI controller improves computation time while maintaining comparable tracking and state-of-charge regulation to the centralized scheme.
Investigation of Pressure Effects on Combustion Characteristics of Hydrogen Annular Micro-Mixing Nozzles
Authors: Liu Jian , Qiu Penghua , Wang Xiyu , Hu Qiming , Liu Li , Zhang Linyao , Xing Chang 
Published: August 2024

Abstract
In pursuit of achieving near-zero emissions and preventing flashback, micro-mixing combustion technology has been developed and implemented in hydrogen gas turbines. This investigation proposed an annular micro-mixing nozzles comprising seven annular nozzles arranged in a regular hexagonal pattern. Experimental investigations based on OH* Chemiluminescence with OH-PLIF synchronous measurement technique were performed. Results indicate that with increasing pressure, the flames become smaller and shorter, and the interaction between flames weakens compared to atmospheric pressure. At higher pressures, the flames predominantly rely on the bluff bodies of the annular nozzles for stability. This leads to a more concentrated flame reaction zone, increased local heat release, and an exponential increment in NO emissions. However, the experiments reveal that at combustion pressures equal to or below 0.2 MPa., NO emissions under the test conditions remain below 10ppm (@15%O2).
Numerical and Experimental Study on Flow Loss Reduction Effect of Micro-Textured Surface on Compressor Cascade
Authors: Wang Liyue , Wang Cong , Sun Gang , Feng Jinzhang 
Published: August 2024

Abstract
Surface structures with excellent aerodynamic performance can reduce the flow loss of aero-engine caused by the harsh working environment to a certain extent. Inspired by the dentate micro-texture over shark skin, micro-texture surface has been proposed as an emerging and effective means to reduce the flow loss of aero-engine. However, for a realistic compressor cascade configuration with micro-texture, using massive grids to describe the flow within the boundary layer makes the simulation of multi-scale flow field unfeasible. This paper presents an innovative numerical simulation method for compressor cascade with micro-textured surface using a machine learning wall modification model. The wall modification model is trained based on the near-wall microflow data obtained by LBM, which can reproduce the flow effects of micro-textured surface. The mechanism of reducing the total pressure loss of the compressor cascade is that the micro-textured surface structure delays the laminar transition and decreases the intensity of the turbulent region. In addition, wake measurements through experiment are performed to validate the proposed multi-scale numerical simulation method in the high-speed linear cascade wind tunnel. This paper demonstrates the flow loss reduction effect of micro-textured surface on compressor cascade through numerical and experimental study.
Performance of sCO2 Cycles for Waste Heat Recovery and Techno-Economic Perspective As Gas Turbine Bottoming Cycle
Authors: Thielens Vincent , Demeyer Frederiek , De Paepe Ward 
Published: August 2024

Abstract
Supercritical carbon dioxide (sCO2) cycles are compact, cost-effective and widely adaptable to various heat sources, including the waste heat from gas turbine (GT) exhaust gases. While the addition of a steam cycle enhances the typical 40%-efficiency of GTs up to 60%, their substantial investments render them less appealing for smaller GTs. This creates an opportunity for sCO2 cycles, but a comprehensive comparison of their performance with that of steam across a range of applications remains lacking. Moreover, their applicability to various industrial scenarios based on existing installations is missing from a techno-economic standpoint. To address these needs, four promising sCO2 cycles are evaluated and optimized using Aspen, and compared with the simple steam cycle. Their techno-economic performances are then investigated for 20 industrial GTs of different size up to the larger CCGT units incorporating amine-based carbon capture systems. Due to the significant investments required by the carbon capture unit, the implementation of a CC unit is only investigated for the largest CCGT units. The analysis yielded performance maps demonstrating comparable performances for sCO2 and steam cycles, as well as significant techno-economic advantages for sCO2 bottoming cycles for smaller GTs. However, when it comes to larger GTs combined with reheats and expansions steam cycles, sCO2 cannot outperform them in current technological standards. Nevertheless sCO2 cycles offers an attractive alternative, facilitating cogeneration. Among the different approaches designed to integrate the heat requirements of amine-based capture, steam cycles have always proved more suitable because of the thermal stability of amines. In conclusion, the research underscores the cost-effectiveness and adaptability of sCO2 cycles for heat recovery applications, particularly as bottoming cycles for smaller GTs, while larger GTs present a challenge. The work conducted sheds light on the substantial promise of sCO2 cycles, encouraging further exploration and implementation of these systems in the energy sector.
Generalized Method for the Conceptual Design of Compact Heat Exchangers
Authors: Miltén Petter , Jonsson Isak , Lundbladh Anders , Xisto Carlos 
Published: August 2024

Abstract
The paper introduces a novel method for generalized heat exchanger design and evaluation, freeing the process from predefined geometries. It aims to facilitate early-stage conceptual exploration, allowing the designer to make informed decisions. The paper explores heat transfer and fluid friction principles in order to set key parameters for estimating aerothermal performance, introduced by LaHaye. Arguing against a single metric, the paper proposes a custom cost function for evaluating the integrated generalized heat exchanger. A case study applies the method to a particular aircraft engine scenario, using cost functions to evaluate intercooler designs based on pressure loss and heat transfer surface weight. The study determines suitable heat exchanger families for further development, considering factors like finned area, compactness and flow distribution.
Compressor Development for CO2-Based Pumped Thermal Energy Storage (PTES) Systems
Authors: Held Timothy J. , Miller Jason , Sedlacko Kyle , Cameron Joshua , Morris Scott , Kang Jeongseek , Turner Mark 
Published: August 2024

Abstract
Pumped thermal energy storage (PTES) offers a cost-effective means to store electrical energy for long duration by utilizing a heat pump cycle to transfer thermal energy from a low temperature reservoir (LTR) to a high temperature reservoir (HTR). A key component of the PTES system is the heat pump compressor, which represents a significant driver to the cost, performance and operating characteristics of the PTES system. At the power rating of the charging process (&gt; 100 MW), traditional compressor scaling charts indicate that the operating conditions needed would be best served by a multistage axial compressor. While frame gas turbine compressors at these power ratings exist and operate at higher pressure ratios than needed for the CO2 PTES system, the inlet pressure and fluid density of this application exceeds experience values. The conceptual design of a large-scale CO2 axial compressor was completed, including mean-line estimates of the compressor performance at full power conditions. At steady state, full power operation, the isentropic efficiency and mechanical efficiency of the compressor have significant impact on the cycle design and round trip efficiency of the PTES system. The results of the conceptual design were used to refine the PTES cycle design, and updated operating conditions provided for further aero design optimization. An important characteristic of the PTES system is its ability to charge at variable rate, which provides significant challenges on compressor operability, especially for a compressor that will be coupled to a fixed-speed synchronous motor. Cycle studies of variable charging rate processes have been conducted, and the impact of compressor operating map characteristics explored. Based on initial modeling studies, single compressor operation can be achieved down to at least 50% of rated power, with further reductions possible depending on the characteristics of the compressor map speedlines.
Comprehensive Experimental Assessment of Unsteady Pressure and Heat Flux in a Small-Core Turbine Over-Tip Shroud
Authors: Castillo Sauca Antonio , Bhatnagar Lakshya , Inhestern Lukas Benjamin , Paniagua Guillermo 
Published: August 2024

Abstract
For novel high-speed small core turbines, with tip clearance below 0.5mm, even small blade-to-blade tip clearance variation is significant. The assessment of these complex flows is pertinent to the design of the next generation of small-core turbines. This manuscript provides a thorough experimental analysis of the shroud’s unsteady heat flux and static pressure in a small-core squealer-tip blade turbine. Atomic Layer Thermopile sensors (ALTP) and fast response pressure transducers were used to perform high-frequency acquisition at 2MHz around the 51% axial blade chord on the shroud. Measurements were taken at engine-representative conditions at several operational conditions and tip clearances. The signals were phase-locked averaged over the revolution period and synchronized to identify individual blade and row signature. The linear relationship between the rotational tip Reynolds and the static pressure ratio across the blade tip reveals the transition point to reverse over-tip flows. Total heat flux is decomposed into the different steady and unsteady heat flux contributions. It is demonstrated that the adiabatic wall temperature governs the unsteady heat flux and contributes to one third of the total surface heat flux. A linear trend was observed between the unsteady heat flux and the tip clearance measured at the pressure and suction side rims. Similar trends were observed between the local heat flux and the pressure ratio across the tip. A comparison with CFD predictions highlights some limitations on resolving the detached and secondary flows, evidencing the necessity of complementary experimental data.
Multirow Film-Cooling Effectiveness of Vertically Oriented Slot Cross-Section Diffusion Holes on a Turbine Nozzle Guide Vane Suction Surface
Authors: Hu Jia-Jun , An Bai-Tao 
Published: August 2024

Abstract
In this paper, a multirow film cooling effectiveness experiment was conducted on a turbine nozzle guide vane suction surface using the pressure-sensitive paint (PSP) measurement technique. Five rows of film holes were designed at the suction side with a streamwise staggered arrangement and a 6D spanwise hole spacing. Two diffusion holes constructed based on a vertically oriented slot cross-section with 14 deg and 20 deg exit expansion angles were tested. A fan-shaped hole and a horizontally oriented slot cross-section diffusion hole were chosen as the baselines, and both had a 14 deg exit expansion angle. The experiment was carried out in a linear cascade with a mainstream Renolds number of 62000, a mainstream turbulence intensity of 3.7%, and a coolant-to-mainstream density ratio of 1.5. The four averaged blowing ratios ranged from 0.5 to 2.0. The results showed that, regardless of the blowing ratio, under intense multirow film interactions, the vertically oriented slot cross-section diffusion holes can always produce uniform and consistent film coverage on the vane suction surface. The vertically oriented slot cross-section widens the distance between the up- and downstream walls and narrows the lateral width, thereby weakening the influence of the entrance “jetting effect”. The resulting flow pattern can adapt to a larger exit expansion angle. In addition to the smaller difference under a low blowing ratio, two vertically oriented slot cross-section diffusion holes yield prominently greater multirow effectiveness than do the horizontally oriented slot cross-section diffusion hole and conventional fan-shaped hole, in which the case with a 20 deg expansion angle performs better.