Advances in Green Propulsion Engine and Environmental Pollution Control

A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Environmental and Green Processes".

Deadline for manuscript submissions: 10 June 2024 | Viewed by 7380

Special Issue Editors

Institute for Aero Engine, Tsinghua University, Beijing 100084, China
Interests: swirling flame combustion; thermal stability of kerosene; supercritical fuel heat transfer; air–fuel heat exchanger; fuel-cooling technology

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Guest Editor
Institute for Aero Engine, Tsinghua University, Beijing 100084, China
Interests: ignition and combustion; active thermal protection and fuel cooling technology; fuel characteristics and coking properties; supersonic turbulent combustion

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Guest Editor
Institute for Aero Engine, Tsinghua University, Beijing 100084, China
Interests: gas turbine engine; turbomachinery optimization; aerodynamic stability and aeroelasticity; uncertainty quantification

Special Issue Information

Dear Colleagues,

Fulfilling the ever-increasing energy demands of society and doing so with environmental and climate protections has initiated the process of decarbonization—the removal of net carbon dioxide emissions. Many countries and industries have announced their roadmaps and measures to reach carbon neutrality. The aviation industry can be treated as one of the most carbon-intense sectors and especially contributes to carbon emissions at high-level attitudes. In response to concerns over the global environmental impacts of aviation, new green aviation technology has been proposed to dramatically reduce fuel use, emissions, and noise and to cut emissions from national commercial aircraft fleets by more than 50% while also reducing perceived noise levels near airports to one-half of the levels of the quietest aircrafts flying today. Our goal is to significantly reduce the impact that air transport has on the climate, and our long-term goal is emission-free flight.

To date, intensive efforts have been made to develop an efficient, stable, and green aero-engine. New technologies, including innovative and optimal designs of aero-engines are developed to improve the efficiency and performance of aero-engines. The improvement of aero-engine SFC(Specific Fuel Consumption)is highly beneficial to reduce carbon emissions. Efforts can be made to enahce the efficnecy of engine components. Moreover, the development of advanced thermal cycles is also promising. Hydrogen is also considered to be one of the most promising energy sources and is capable of meeting our rapidly growing energy demands due to its cleanliness, sustainability, zero-carbon, and effectiveness. Topics of interest in green aviation technologies include studies on hydrogen, hydrogen–kerosene blends, the interaction between combustors and turbines, advances in combustion instabilities, combustion chamber design, and combustion strategies and technical solutions, turbine-cooling technology, adavances in fan/compressor design, and the aerodynamic and aeroelastic instabilities of turbomachinery.

Original research articles based on theoretical/experimental studies and critical reviews are highly welcome.

New aviation propulsion technology will usher in new development opportunities. Green and efficient aircraft engines are the core link of the whole aviation industry chain, and every technological innovation of the engine is an important driving force for the development of aviation history.

Dr. Xinyan Pei
Prof. Dr. Lingyun Hou
Dr. Baotong Wang
Guest Editors

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • green gas turbine technologies
  • variable cycle engines in civil aviation
  • advanced aero-engine technologies
  • hydrogen-fuel aero-engine
  • advanced pollutant emission measurements and control techniques
  • advanced thermal cycle technologies
  • aviation carbon emissions and climate change

Published Papers (6 papers)

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Research

14 pages, 3960 KiB  
Article
Microscopic Imaging on Diesel Spray and Atomization Process
by Yassine El Marnissi and Joonsik Hwang
Processes 2024, 12(2), 359; https://doi.org/10.3390/pr12020359 - 8 Feb 2024
Viewed by 655
Abstract
Improving diesel engine performance requires a comprehensive understanding of fuel atomization and air–fuel mixing within the combustion chamber. Numerous studies have been conducted to reduce emissions and enhance diesel engines. However, further investigation is required on the detailed diesel spray process. In this [...] Read more.
Improving diesel engine performance requires a comprehensive understanding of fuel atomization and air–fuel mixing within the combustion chamber. Numerous studies have been conducted to reduce emissions and enhance diesel engines. However, further investigation is required on the detailed diesel spray process. In this study, we adopted extinction measurement to analyze the effects of a fuel injection pressure range of 300 to 700 bar on spray morphology. For the extinction imaging setup, we utilized a high-intensity continuous LED source along with a diffuser to ensure uniform light distribution. The high-speed extinction and image processing results indicate that increasing the injection pressure from 300 to 700 bar effectively produced a smaller particulate size (15% reduction) and a better air–fuel mixing process. Especially at the end of injection, our results show smaller liquid ligaments (50% reduction) and droplets around the injector tip with higher injection pressure cases. Full article
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16 pages, 6885 KiB  
Article
Effect of Self-Recirculating Casing Treatment on the Aerodynamic Performance of Ultra-High-Pressure-Ratio Centrifugal Compressors
by Tengbo Fan, Baotong Wang, Chuanxiang Yan, Wenchao Zhang, Zhaoyun Song and Xinqian Zheng
Processes 2023, 11(8), 2439; https://doi.org/10.3390/pr11082439 - 13 Aug 2023
Cited by 1 | Viewed by 984
Abstract
The motivation to design a more efficient and compact aircraft engine leads to a continuous increase in overall pressure ratio and decrease in the stage number in compressors. Compared to the traditional multi-stage compressor, a single-stage ultra-high-pressure-ratio centrifugal compressor with a pressure ratio [...] Read more.
The motivation to design a more efficient and compact aircraft engine leads to a continuous increase in overall pressure ratio and decrease in the stage number in compressors. Compared to the traditional multi-stage compressor, a single-stage ultra-high-pressure-ratio centrifugal compressor with a pressure ratio higher than 10.0 can significantly improve the engine’s power-to-weight ratio and fuel economy with a reduced structure complexity. Thus, it has great potential to be adopted in the compression system of advanced aero engines, such as turboshaft engines, in the future. However, the highly narrow Stable Flow Range (SFR) of ultra-high-pressure-ratio centrifugal compressors is a severe restriction for engineering applications. This research focuses on the aerodynamic performance of a ultra-high-pressure-ratio centrifugal compressor, and three-dimensional simulation is employed to investigate the effect of Self-Recirculating Casing Treatment (SRCT) on the performance and stability of the centrifugal compressor. Firstly, the parametric model of SRCT is established to investigate the effect of geometry parameters (rear slot distance and rear slot width) on the aerodynamic performance of the centrifugal compressor. It is concluded that SRCT improves the compressor’s SFR but deteriorates its efficiency. Also, a non-linear and non-monotone relationship exists between the SFR and rear slot distance or width. Then, the flow mechanism behind the effect of SRCT is explored in detail. By introducing the SRCT, an additional flow path is provided across the blade along the circumferential direction, and the behavior of the shock wave and tip leakage flow is significantly changed, resulting in the obviously different loading distribution along the streamwise direction. As a result, the mixing and flow separation loss are enhanced in the impeller flow passage to deteriorate the efficiency. On the other hand, the blockage effect caused by the mixing of slot recirculation and mainstream flow near the impeller inlet increases the axial velocity and reduces the incidence angle below the 90% spanwise section, which is considered to effectively stabilize the impeller flow field and enhance the stability. Full article
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22 pages, 7495 KiB  
Article
Study of Tangential Effusion Cooling of a Combustor Liner
by Ziwan Li, Pengfu Xie, Qinghua Zeng and Xuanwu Chen
Processes 2023, 11(8), 2433; https://doi.org/10.3390/pr11082433 - 12 Aug 2023
Viewed by 948
Abstract
Tangential effusion cooling of a combustor liner has a large difference from traditional effusion cooling on a plate. In this paper, numerical simulation is carried out to study the flow field, heat transfer characteristics and the factors affecting the cooling effectiveness of tangential [...] Read more.
Tangential effusion cooling of a combustor liner has a large difference from traditional effusion cooling on a plate. In this paper, numerical simulation is carried out to study the flow field, heat transfer characteristics and the factors affecting the cooling effectiveness of tangential effusion cooling of a combustor liner. It is found that the cooling film formed by the tangential jet is distributed in a divergent “horsetail” shape and adheres tightly to the inner wall of the liner, which increases the cooling area and effectiveness. Three different tangential inlet cooling hole arrangements and their cooling efficiencies are studied, and several important parameters that affect the cooling effectiveness are summarized. Then, an improved cooling hole arrangement is proposed, and its cooling efficiency is studied and compared with those of the original three arrangements. The results show that the new arrangement significantly improves the comprehensive cooling efficiency and decreases the wall temperature, thus confirming the effectiveness of the improved strategy and providing a theoretical basis for the subsequent cooling design to improve the cooling efficiency for a combustor liner. Full article
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11 pages, 5844 KiB  
Article
Mechanical Behavior and Low-Cycle Fatigue Performance of a Carburized Steel for GTF Engines
by Juan Cao and Junjie Yang
Processes 2023, 11(4), 1275; https://doi.org/10.3390/pr11041275 - 20 Apr 2023
Viewed by 1021
Abstract
Using nanoindentation technology to analyze the hardness and elastic modulus distributions of the local microzones within materials, it can be determined that the case-carburized specimen is a composite of the carburized case and the pseudo-carburized material in the core. The overall mechanical behavior [...] Read more.
Using nanoindentation technology to analyze the hardness and elastic modulus distributions of the local microzones within materials, it can be determined that the case-carburized specimen is a composite of the carburized case and the pseudo-carburized material in the core. The overall mechanical behavior of the case-carburized material is much closer to that of the completely carburized material, indicating that the carburized case dominates the case-carburized material. Stress fatigue tests conducted on carburized tubular specimens, pseudo-carburized solid specimens, and case-carburized solid specimens showed that the fatigue performance of the completely carburized material is slightly lower than that of the pseudo-carburized specimens due to lower plasticity. However, the fatigue performance of the case-carburized specimens is significantly better than that of the two homogeneous materials. This could be attributed to the graded material behavior and the larger compressive residual stress in the carburized case, which are the primary positive factors for improving the fatigue life of case-carburized materials. SEM fractographs revealed that the fatigue nucleation in the case-carburized specimen initiates from the transition zone rather than from the surface of the specimens as observed in the homogeneous materials. Low-cycle fatigue evaluation of ultra-high-power gear transmission systems should focus on the influences of the carburized case. Full article
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20 pages, 812 KiB  
Article
Transient Modeling and Performance Analysis of Hydrogen-Fueled Aero Engines
by Xiting Wang, Ai He and Zhongzhi Hu
Processes 2023, 11(2), 423; https://doi.org/10.3390/pr11020423 - 31 Jan 2023
Cited by 2 | Viewed by 2042
Abstract
With the combustor burning hydrogen, as well as the strongly coupled fuel and cooling system, the configuration of a hydrogen-fueled aero engine is more complex than that of a conventional aero engine. The performance, and especially the dynamic behavior of a hydrogen-fueled aero [...] Read more.
With the combustor burning hydrogen, as well as the strongly coupled fuel and cooling system, the configuration of a hydrogen-fueled aero engine is more complex than that of a conventional aero engine. The performance, and especially the dynamic behavior of a hydrogen-fueled aero engine, need to be fully understood for engine system design and optimization. In this paper, both the transient modeling and performance analysis of hydrogen-fueled engines are presented. Firstly, the models specific to the hydrogen-fueled engine components and systems, including the hydrogen-fueled combustor, the steam injection system, a simplified model for a quick NOx emission assessment, and the heat exchangers, are developed and then integrated to a conventional engine models. The simulations with both Simulink and Speedgoat-based hardware in the loop system are carried out. Secondly, the performance analysis is performed for a typical turbofan engine configuration, CF6, and for the two hydrogen-fueled engine configurations, ENABLEH2 and HySIITE, which are currently under research and development by the European Union and Pratt & Whitney, respectively. At last, the simulation results demonstrate that the developed transient models can effectively reflect the characteristics of hydrogen burning, heat exchanging, and NOx emission for hydrogen-fueled engines. In most cases, the hydrogen-fueled engines show lower specific fuel consumption, lower turbine entry temperature, and less NOx emissions compared with conventional engines. For example, at max thrust state, the advanced hydrogen-fueled engine can reduce the parameters mentioned above by about 68.5%, 3.7%, and 12.7%, respectively (a mean value of two configurations). Full article
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15 pages, 7251 KiB  
Article
A Novel Design towards Reducing Leakage Loss for Variable Geometry Turbines
by Kai Zhou and Xinqian Zheng
Processes 2023, 11(1), 21; https://doi.org/10.3390/pr11010021 - 22 Dec 2022
Viewed by 1114
Abstract
To accommodate the next generation of adaptive/variable cycle engines and gas turbine power, the variable geometry turbine (VTG) is widely acknowledged as a most essential component. VGT consists of an adjustable vane to address the combined goals of high dry thrust and low [...] Read more.
To accommodate the next generation of adaptive/variable cycle engines and gas turbine power, the variable geometry turbine (VTG) is widely acknowledged as a most essential component. VGT consists of an adjustable vane to address the combined goals of high dry thrust and low specific fuel consumption (SFC) at subsonic cruises for aero-engines. This concept allows an engine to operate at a constant bypass ratio over a wide range of pressure ratios. To avoid scraping during rotation for guide vanes, a typical gap is deliberately left, which leads to significant leakage loss. In this research work, a novel spherical convex plat with a pivot shaft is proposed, which can be obtained by additive manufacturing. The plat is sophisticatedly designed according to the aggressive tip/hub pressure gradient. This design naturally generates a blockage for the gas from the pressure side towards the suction side. As a result, the most aggressive pressure gradient is removed, and maximum leakage flow is eliminated. The overall leakage loss is reduced. This simple rotating structure design can improve the efficiency by 0.4–3.0% within the wide range considered. Based on the understanding of the loss mechanism, a radially restacked vane is designed and another extra 0.2% improvement is achieved. This universal design philosophy is also verified on different loading blade profiles, i.e., front-, middle- and aft-loaded turbine vane. The improved aerodynamic performance is achieved with this novel idea. Full article
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