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Influence of ground effect on flow field structure and aerodynamic noise of high-speed trains

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2024年第2期25卷 147-160页

作者： Xiaoming TAN Linli GONG Xiaohong ZHANG Zhigang YANG Key Laboratory of Intelligent Manufacturing and Service Performance Optimization of Laser and Grinding in Mechanical Industry Hunan Institute of Science and TechnologyYueyang414000China Key Laboratory of Traffic Safety on Track(Central South University) Ministry of EducationSchool of Traffic&Transportation EngineeringCentral South UniversityChangsha410075China

The simulation of the ground effect has always been a technical difficulty in wind tunnel tests of high-speed trains.In this paper,large eddy simulation and the curl acoustic integral equation were used to simulate the flow-acoustic field results of high-speed trains under four ground simulation systems(GSSs):“moving ground+rotating wheel”,“stationary ground+rotating wheel”,“moving ground+stationary wheel”,and“stationary ground+stationary wheel”.By comparing the fluid-acoustic field results of the four GSSs,the influence laws of different GSSs on the flow field structure,aero-acoustic source,and far-field radiation noise characteristics were investigated,providing guidance for the acoustic wind tunnel testing of high-speed trains.The calculation results of the aerodynamic noise of a 350 km/h high-speed train show that the moving ground and rotating wheel affect mainly the aero-acoustic performance under the train bottom.The influence of the rotating wheel on the equivalent sound source power of the whole vehicle was not more than 5%,but that of the moving ground slip was more than 15%.The average influence of the rotating wheel on the sound pressure level radiated by the whole vehicle was 0.3 dBA,while that of the moving ground was 1.8 dBA.

关键词： High-speed train Aero-acoustics flow field structure Large eddy simulation Moving ground condition Rotating wheel

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Effects of Pilot Fuel Ratio on Combustion Process:flow field structure and Pollutant Emissions

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Journal of Thermal Science 2023年第6期32卷 2321-2335页

作者： ZONG Chao JI Chenzhen CHENG Jiaying ZHU Tong Postdoctoral Station of Mechanical Engineering Tongji UniversityShanghai201804China School of Mechanical Engineering Tongji UniversityShanghai201804China

As the only controllable means of a micro gas turbine(MGT)combustor during unit operation,pilot fuel ratio(PFR)is the key to achieving stable combustion and low pollutant emission.This paper discusses the influence of PFR on the inner flow field structure and pollutant emissions.The steady-state three-dimensional RANS method with a 40-step reduced methane-air kinetics mechanism is used to study the reaction flow field and species field with PFR of 9.0%,12.7%,15.2%and 17.6%.Results show that,with the decrease in PFR,the axial velocity and temperature near the central axis of the combustion chamber show a tendency to decrease.A similar separation phenomenon occurred in the core pyrolysis reaction zone(measured by HCO)and oxidation zone(measured by OH),which is more conducive to promoting the oxidation of CO.The quantitative effect of the pilot flame on nitrogen oxides(NO_(x))was separated by using inert gas instead of nitrogen in combustion air.It was found that the NOx produced by the pilot flame under the operation condition with a PFR of 9.0%was 3.2×10^(−6),accounting for 17.4%of the total NOx emission,which was twice that of PFR.

关键词： micro gas turbine pilot fuel ratio flow field structure carbon monoxide nitrogen oxide

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Detached eddy simulation on the structure of swirling jet flow field

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Petroleum Exploration and Development 2022年第4期49卷 929-941页

作者： CHEN Jianxiang YANG Ruiyue HUANG Zhongwei LI Gensheng QIN Xiaozhou LI Jingbin WU Xiaoguang State Key Laboratory of Oil and Gas Resources and Exploration Beijing 102249China China University of Petroleum(Beijing) Beijing 102249China

The improved delayed detached eddy simulation method with shear stress transport model was used to analyze the evolution of vortex structure,velocity and pressure fields of swirling jet.The influence of nozzle pressure drop on vortex structure development and turbulence pulsation was investigated.The development of vortex structure could be divided into three stages:Kelvin-Helmholtz(K-H)instability,transition stage and swirling flow instability.Swirling flow could significantly enhance radial turbulence pulsation and increase diffusion angle.At the downstream of the jet flow,turbulence pulsation dissipation was the main reason for jet velocity attenuation.With the increase of pressure drop,the jet velocity,pulsation amplitude and the symmetry of velocity distribution increased correspondingly.Meanwhile the pressure pulsation along with the axis and vortex transport intensity also increased significantly.When the jet distance exceeded about 9 times the dimensionless jet distance,the impact distance of swirling jet could not be improved effectively by increasing the pressure drop.However,it could effectively increase the swirl intensity and jet diffusion angle.The swirling jet is more suitable for radial horizontal drilling with large hole size,coalbed methane horizontal well cavity completion and roadway drilling and pressure relief,etc.

关键词： swirling jet flow field structure detached eddy vortex evolution turbulence pulsation jet velocity jet diffusion angle

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