bluuebunny/crossref_metadata_2025_split huggingface dataset:
Film Superposition Characteristics With Laidback Fan-Shaped Holes Under the Influence of Internal Crossflow
Authors: Liu Haoyang , Du Qiang , Xu Qingzong , Xu Jiawei , Xu Guangyao , Li Hongye , Wang Pengfei 
Published: August 2024

Abstract
In the serpentine passage of actual rotor blades, the coolant at the inlet of the film hole has an internal crossflow. The internal crossflow significantly influences the film cooling effectiveness of multi-row film holes. This paper presents a numerical investigation of the superposition characteristics of multiple rows of laidback fan-shaped holes under the influence of internal crossflow. The numerical simulations utilize the RANS method considering the effects of blowing ratio, crossflow velocity ratio, arrangement patterns, and row-to-row spacing of the internal crossflow on the superposition characteristics of film holes. The results indicate that film cooling effectiveness exhibits a distinctly asymmetric distribution under crossflow conditions. At different blowing ratios, there exists an optimal crossflow velocity ratio, at which the laterally averaged film cooling effectiveness is maximized. The crossflow-to-jet velocity ratio (VRi) is utilized to comprehensively evaluate the impact of blowing ratios and crossflow velocity ratios, the range of high area averaged film cooling effectiveness is accurately captured. Regarding the study of arrangement patterns and row-to-row spacings, it has been found that under identical coolant mass flow rates, the staggered arrangement is better than the inline arrangement in both laterally averaged film cooling effectiveness and cooling uniformity. Meanwhile, reducing the row-to-row spacing leads to an improvement in laterally averaged film cooling effectiveness. Finally, an assessment of the Sellers model’s applicability under crossflow conditions revealed that it demonstrates good applicability in cases of staggered arrangement with lower blowing ratios.
Application of Deep Learning for Fan Rotor Blade Performance Prediction in Turbomachinery
Authors: Fesquet Jean , Bauerheim Michael , Rojda Ludovic , Bousquet Yannick , Binder Nicolas 
Published: August 2024

Abstract
Turbomachinery fan optimisation is a complex multidisciplinary process, which forces engineers to rely on strong theoretical assumptions and/or can be very computationally expensive. Additionally, with new constraints arising, such as distorted inflow in boundary layer ingestion cases, it is essential to find surrogate models able to account for the requirements and produce satisfying results, while capitalizing on the computational and experimental data already produced on other (e.g. previously developed) configurations. Towards this objective, the present study aimed at predicting the performance of the rotor of a turbomachine fan stage using Deep Learning (DL) techniques. These approaches have been showing increasingly convincing results in recent times, yet usually applied to toy problems or simplified configurations. Thus, this work evaluates the feasibility of applying DL models to optimise the shape of realistic fan rotor blades. To that end, a pipeline is presented to generate and mesh new geometries, run simulations, and finally train deep neural networks to be used as surrogates for performance prediction. In this framework, a u-net type deep neural network was used to predict 2D wake-flow fields of entropy and two 0D metrics, efficiency and pressure ratio, from the geometry of the blade and its operating conditions. To reduce the complexity of the predictive tasks, a transformative approach is used, by opposition to a fully generative one. For model testing and training, 75 geometries were built through interpolation of pre-existing, parametrised rotor blades. In turn, RANS computations at various operating points were performed. The model was compared to POD-Kriging techniques. Results showed that the neural network was only a slight improvement on an iso-geometry data-set, but widely outperformed the POD-Kriging model on the multigeometry data-set. As a conclusion, it provided a good proof of concept to learn flow field views and global performance metrics on realistic, 3D, fan rotor geometries to be later used for optimisation.
Development of Compact and Hermetic ORC Turbine Generator With Upgraded Cooling Capability
Authors: Tanaka Toshimitsu , Takata Ryo , Hirado Takuma , Kawanami Akira 
Published: August 2024

Abstract
In this paper, a hermetic and oil-free turbine generator for a cryogenic ORC is suggested and investigated. The generator mainly consists of a high-speed generator, a two-stage supersonic turbine, and magnetic bearings. Based on the hermetic design concept, these components are in a common casing. To upgrade the cooling capability of the generator, heat dissipation fins are installed between the 1st and 2nd stage of the turbine. Performance of the turbine generator was preliminarily investigated by CFD calculations. These results show that the turbine efficiency peaks at 16,000rpm under the design pressure ratio condition. Under the same condition, it is also predicted that comparatively high static pressure recovery coefficient and low total pressure loss can be obtained through the flow path with the fins. Moreover, a series of experimental campaign were conducted on an ORC test rig using −96 deg.C liquid nitrogen and 50 deg.C warm water as cold source and heat source, respectively. These results indicate that the target power output was achieved and the installed heat dissipation fins are effective to enhance the cooling capability of the generator. It was also indicated that under comparatively high loaded conditions, the turbine power output can be increased by heat transferred from the generator.
Navigating Technological Risks: an Uncertainty Analysis of Powertrain Technology in Hybrid-Electric Commuter Aircraft
Authors: Diamantidou Dimitra-Eirini , Soibam Jerol , Zaccaria Valentina , Kalfas Anestis 
Published: August 2024

Abstract
This study addresses the uncertainties in hybrid-electric powertrain technology for a 19-passenger commuter aircraft, focusing on two future Entry-Into-Service timeframes: 2030 and 2040. The methodology is split into a preliminary optimization of aircraft design based on nominal technology scenarios followed by Monte Carlo simulations to investigate the impact of diverse technology projections and distribution types. Advanced surrogate modeling techniques, leveraging deep neural networks trained on a dataset from an aircraft design framework, are employed.
Key outcomes from this work reveal a marked increase in computational efficiency, with a speed-up factor of approximately 500 times when utilizing surrogate models. The results indicate that the 2040 EIS scenario could achieve larger reductions in fuel and total energy consumption — 20.4% and 15.8% respectively — relative to the 2030 scenario, but with higher uncertainty. Across all scenarios examined, the hybrid-electric model showcased superior performance compared to its conventional counterpart. The battery specific energy density is proved to be a critical parameter of the aircraft’s performance across both timeframes. The findings emphasize the importance of continuous innovation in battery and motor technologies to target towards greater system-level efficiency and reduced environmental impact.
Optimal Part-Load Performance of Supercritical Carbon Dioxide Brayton Cycles During Inventory Control
Authors: Gupta Shrey Sahai , Kumar Pramod 
Published: August 2024

Abstract
Supercritical carbon dioxide (sCO2) cycles are gaining attention for their efficiency and low carbon footprint in power plants. This study focuses on optimizing the performance of a 5 MW simple recuperated sCO2 Brayton loop during inventory control, a recommended strategy for maximum part-load efficiencies. Variable speed operation of turbomachines is explored to enhance part-load efficiency across the operating range, contrasting with the baseline case of constant turbine and compressor speeds. The analysis, which is based on an analytical formulation and validated component models reveals that part-load efficiency can be improved by variable speed operation of the turbomachines. The decoupled shaft systems outperform coupled or single shaft systems. Further, part-load efficiency deterioration in case of constant speeds has been discussed in depth. A unique feature of this study is its modelling methodology. The compressor model is derived by modifying an ideal gas compressor model to account for the behavior of a real gas compressor. Component matching is performed systematically to estimate cycle conditions accurately. This work enhances our understanding of sCO2 cycle operation under part-load conditions, providing valuable insights on control strategy and inventory management system design for fast response and improved efficiency.
The Impact of Inflow Unsteadiness on Loss Prediction
Authors: Przytarski Pawel J. , Lengani Davide , Sandberg Richard 
Published: August 2024

Abstract
Stagnation pressure loss coefficient is still the most commonly used loss metric for performance evaluation and is routinely used to validate simulations. This is because it is easy to measure and readily available from the experiments. However, it was previously shown (GT2023-102767) that the stagnation pressure loss coefficient can become unreliable when high levels of inflow unsteadiness are present.
As the current design trends are moving towards more compact machines and higher work coefficients, the levels of unsteadiness are likely to increase. It is therefore desirable to assess how higher inflow unsteadiness levels affect the performance of new blade designs and what loss metrics should be used to reliably estimate it.
Motivated by the need to understand how performance prediction changes under highly unsteady inflow conditions, we perform a series of high fidelity scale resolving simulations. We use this data to construct energy budgets for a variety of mid-span compressor cases with varying Reynolds numbers and inflow turbulence intensities. This allows us to systematically assess the impact of inflow conditions on loss prediction when using stagnation pressure based loss metrics. Stagnation pressure loss coefficient was found to be least reliable for the high inflow turbulence intensities and at high Reynolds numbers.
Investigating the Impact of Steam Enhancement on Combustion in a Swirl-Assisted Jet-Stabilized Gas Turbine Combustor
Authors: Izadi Saeed , Kislat Oliver , Zanger Jan , Seliger-Ost Hannah , Kutne Peter , Aigner Manfred 
Published: August 2024

Abstract
A newly developed gas turbine combustor system based on the swirl-assisted jet-stabilized concept using Jet A-1 and natural gas as reference fuel is tested under wet conditions to evaluate its combustion characteristics in the presence of steam. The effect of steam injection into the gas turbine combustor under both spray and superheated liquid fuel injection conditions is studied experimentally on an atmospheric test rig. The experiments are conducted at atmospheric pressure and an elevated combustion air temperature of 305°C. To evaluate the effect of steam injection on combustion performance, the water-to-gas ratio (WGR) is varied from 0 to 32%. Even at very high WGR levels, the results show virtually no combustion thermoacoustic instability during operation. With increasing WGR = 0 to 16% and at stoichiometric condition, NOx reductions of −82% to −100% were observed during Jet A-1 and natural gas combustion, respectively. It is shown that the reduction of the combustion zone temperature due to the steam acting as a heat sink is the main cause of the NOx decrease. For both wet and dry conditions, CO levels remained fairly similar. Both flame length and flame height above the burner increased with increasing WGR. This is due to the reduced reactivity of the fuel-air mixture. The operating range of the burner remained fairly constant for Jet A-1 until WGR = 20%, while it decreased significantly with increasing WGR for natural gas combustion. While the effect of the WGR on CO was modest, the greatest effect of the WGR was on the heat release zone intensity at a constant air to fuel ratio. In reducing the NOx levels of Jet A-1 and natural gas combustion, both thermal and chemical effects of steam injection were observed. However, steam acting as a heat sink and lowering the flame temperature, thereby reducing the thermal NO formation rate, was the dominant factor in NOx reduction.
Joule Cycle-Based Waste Heat Recovery From Heavy-Duty Truck Engines
Authors: Kenkoh Kesty Yong , Kodaboina Raghu Vamsi , Gubba Sreenivasa Rao , Turner James W. G. 
Published: August 2024

Abstract
Growing global concern over the impact of carbon emissions has spurred many nations to aim to achieve net-zero carbon emissions within the 2030 to 2050 timeframe. A significant contributor to these emissions is the transport sector, responsible for a substantial 23% of total carbon emissions, with heavy-duty (HD) transport accounting for 40% of this cumulative figure. This study explores waste heat recovery (WHR) via the utilization of multiple working fluids in closed and open Joule cycles from the exhaust gas of the Volvo D13 truck engine operating on the European Stationary Cycle (ESC). Furthermore, this paper investigates the potential for recovering heat from the gases in the exhaust gas recirculation (EGR) circuit and examines the impact of pressure drops within the heat exchangers on the WHR process. The design and analysis of these cycles are executed using Aspen Plus, complemented by a one-dimensional D13 engine simulation model in GT-suite to provide the essential exhaust and EGR properties. This study also aims to offer more insight into the viability of pursuing WHR for truck applications using the Joule cycle.
A Numerical and Experimental Study of Five-Hole Probe Calibrations in Low-Speed Flows
Authors: Jeong Dahae , Guimarães Tamara 
Published: August 2024

Abstract
This study aims to establish fundamental steps for developing an optimal methodology to enhance experimental probe calibration. Multi-hole pressure probes have been extensively used to measure the airflow around airfoils, wings, and other surfaces in the field of fluid dynamics. Five-hole probes are broadly used in wind tunnel testing and aerodynamic survey to collect data on velocity, pressure distribution, and flow characteristics. These measurements help in understanding the aerodynamic performance of new aircrafts, planes, and aerospace vehicles to improve the efficiency and lower environmental costs, however, the calibration process for these probes conventionally demands considerable effort, time, and cost. The purpose of this study is to leverage advanced instrumentation and measurement techniques to ensure optimal calibration of probes, thereby minimizing data uncertainty and maximizing accuracy. The automated calibration facility for data acquisition secures outstanding repeatability. A computational study determined an optimal probe placement in a calibration jet to read accurate measurements by investigating the region around the probe surface and nozzle. To shorten the calibration time, experiments for finding an optimized measurement incremental step were implemented and discussed comparatively. Experimental calibration maps were generated using non-dimensional pressure coefficients to describe flow characteristics within predetermined flow conditions. The experimental calibration map was assessed by quantitative comparison, and compared to a high-resolution numerical calibration map. This methodology including research findings is expected to facilitate the study for investigating numerical and experimental calibration in subsonic flows by obtaining great insights into advanced calibration from the present study.
Showerhead Film Cooling Mechanism and Superposition Characteristics of Turbine Blade Leading-Edge
Authors: Li Bing-ran , Liu Cun-liang , Ye Lin , Zhang Fan , Zhou Tian-liang 
Published: August 2024

Abstract
Based on the turbine blade model, the film cooling effectiveness data of single rows of holes at different positions were obtained through numerical simulation, and the superposition characteristics of multiple rows of holes under different average blowing ratios were studied. The applicability of the Sellers superposition formula to the blade leading-edge is discussed. The showerhead film cooling effectiveness distribution of the leading-edge was studied through pressure sensitive paint (PSP) experimental measurement, and the numerical simulation method was verified. The results show that the Sellers superposition formula accurately predicts the average film cooling effectiveness on the leading-edge surface under small and medium blowing ratios. Under large blowing ratios, the prediction accuracy of the superposition formula is significantly reduced. The strong interference of the mainstream and secondary jet flow and the formation of a vortex tube between multiple rows of holes are the main reasons for the failure of the two-dimensional superposition formula and the formation of a sheet-shaped high-film cooling effectiveness area under a large blowing ratio. Changes in the row-of-holes layout have an impact on the film cooling effectiveness distribution but have little effect on the prediction of the area average by the Sellers superposition formula. The experimental measurement data of film cooling effectiveness at large blowing ratios combined with the Sellers superposition formula constitute a reference for designing leading-edge showerhead film cooling structures, which have important application value for engineering design.
The Impact of Friction in Lube Oil Feed Grooves on Power Loss in High-Speed Journal Bearings
Authors: Vetter Daniel , Hagemann Thomas , Schwarze Hubert 
Published: August 2024

Abstract
The contribution of internal friction in the boundary layer flow of lube oil feed grooves to the power loss of high-speed journal bearings is a function of the rotor speed and the flow regime in which the bearing operates. The literature shows that the portion of power loss in the groove region can exceed 30% of the overall power loss. This paper investigates the impact of gas phases in the feed groove region on the reduction of the internal friction in the lubricant. For this purpose, existing measurement data for two fixed-pad bearings with different bore geometries is evaluated for different lubrication conditions including flooded lubrication of all grooves and a deactivation of the oil supply in one groove. The latter configuration involves a significant reduction of measured power loss with increasing bearing unit load. Comparisons with thermo-elasto-hydrodynamic (TEHD) calculations indicate that the partial filling of deactivated lube oil feed grooves leads to a significant reduction of frictional power loss. Different approaches for the theoretical approximation of the impact of the gas phase in the groove region are investigated and validated with the test data to provide improved understanding of friction in high-speed bearings.
Combustor Traverse Optimization to Lower High-Pressure Turbine Rotor Temperatures
Authors: Carta Mario , Ghisu Tiziano , Shahpar Shahrokh 
Published: August 2024

Abstract
As turbine entry temperatures of modern jet engines continue to increase, additional thermal stresses are introduced on the high-pressure turbine rotors, which are already burdened by substantial levels of centrifugal and gas loads. Usually, for modern turbofan engines, the temperature distribution upstream of the high-pressure stator is characterized by a series of high-temperature regions, determined by the circumferential arrangement of the combustor burners. The position of these high-temperature regions, both radially and circumferentially in relation to the high-pressure stator arrangement, can have a strong impact on their subsequent migration through the high-pressure stage. Therefore, for a given amount of thermal power entering the turbine, a significant reduction in maximum rotor temperatures can be achieved by adjusting the inlet temperature distribution. This paper is aimed at mitigating the maximum surface temperatures on a high-pressure turbine rotor from a modern commercial turbofan engine, by conducting a parametric analysis and optimization of the inlet temperature field. The parameters considered for this study are the circumferential position of the high-temperature spots, and the overall bias of the temperature distribution in the radial direction. High-fidelity unsteady (phase-lag) and conjugate heat transfer simulations are performed to evaluate the effects of inlet clocking and radial bias on rotor metal temperatures.
The EPA Proposed Greenhouse Gas Standards: A Gas Turbine Fleet Impact Analysis
Authors: Perullo Christopher , Harper James , Caravaggio Michael , Noble David , Emerson Benjamin , Lieuwen Tim 
Published: August 2024

Abstract
The EPA previously proposed new CO2 standards for both new and existing stationary combustion turbines under Section 111 of the Clean Air Act. At the time of writing, these standards would have had a have significant implications on the operation, capacity factor, reliability, availability, and performance of the gas turbine fleet within the U.S. power grid. The standards would impact the costs of operating the fleet which will impact fleet owners and operators and the public. The proposed standards limit CO2 emissions from new and existing sources and are justified with associated Best System of Emission Reductions (BSER) using Hydrogen-blended fuels or Carbon Capture and Storage. The paper shows that the BSER used to justify the proposed limits are insufficient (i.e., levels of Hydrogen and CCS required for rule compliance are beyond what is stated as BSER justification). Analysis is presented to consider the impact of the rules on the existing gas turbine fleet as operated including assessments of the amount of hydrogen required, number of plants that would be impacted, and projections of the required renewable generation required to replace non-compliant or curtailed gas turbines. The authors also discuss potential unintended incentivized actions based on the rules, such as early retirement of critical generation capacity, and minimizing plant capacity factors at the expense of total CO2 emissions. The methodology to assess the economy-wide impact of technology depends on the analysis’s assumptions. Therefore, this analysis does not predict specific outcomes but offers insights into potential impacts under certain assumed conditions.