Aerodynamic Characteristics Analysis And Shape Optimization Design Of Ultra-high Speed Train With Vacuum Pipeline

The vacuum pipeline transportation technology is the most ideal technology to solve the air resistance and improve the train speed.However,restricted by many technical factors,there is still some thin air in the vacuum pipeline.Therefore,the aerodynamic problem of ultra-high speed flight train is still the key problem faced by the vacuum pipeline transportation technology.Although many scientific research organizations in the world have carried out research on related technologies,there are not many references available at present,and the aerodynamic principle is not very clear.In this paper,the aerodynamic characteristics and shape optimization of a high speed train head in the vacuum pipeline are studied.The main research work is as follows.(1)The air flow field characteristics of high speed train running in open line and tunnel are summarized and analyzed,and the air flow field behavior in the vacuum pipe of ultra-high speed flight train is preliminarily discussed.The principle of Smoothed Particle Hydrodynamics(SPH)algorithm and the feasibility of applying it to simulate the highly nonlinear problem of air flow field in vacuum pipe are studied.The coupling method between SPH particles of air and finite element meshes of vehicle head and pipe is analyzed.(2)Based on the running characteristics of the ultra-high speed train in the vacuum pipe,the aerodynamic characteristics of the head of the ultra-high-speed flight train under different vacuum degrees and running speeds are simulated.The effects of the vacuum degree in the pipeline and the train speed on the air flow field distribution around the train head and aerodynamic drag and lift are discussed.The simulation results show that the aerodynamic drag and lift of the train increase linearly with the initial air pressure in the vacuum pipeline,but exponentially increase with the train speed.(3)Taking the high-speed train CRH380 A head as the simulation and optimization prototype,five shape control variables are created by using Hyper Morph module according to the main surface characteristics of the train head.The multi-objective genetic algorithm is used to optimize the aerodynamic shape of the train head in the vacuum pipeline with the aim of reducing the aerodynamic drag and lift force of the train by using Ls-Dyna and Hyper Study software,and the Pareto optimal solution set is obtained.Compared with the aerodynamic drag and lift before and after optimization,it can be seen that the aerodynamic drag and lift of the optimized train head are reduced by 27.61% and 21.97% respectively.At present,Euler method is mostly used in the optimization of high-speed/ultra-high speed train head shape.In this paper,SPH particle meshless method is used to simulate the air flow field.This method describes the flow field behavior through the particle set trace,and can track the trajectory of specific air particles.The research of the paper is to clarify the characteristics of air flow field in the vacuum pipeline when the ultra-high speed flight train is running,and to explore new methods and ideas for flow field analysis and head shape optimization design of ultra-high speed flight train.