Research On Aerodynamic Shape Optimization Of Vacuum Pipeline Ultra High Speed Train Head

With the development of social economy and the progress of science and technology,people put forward higher requirements for the speed of transportation.However,due to the dense atmosphere on the surface,the traditional high-speed train cannot achieve further speed increase due to the huge air resistance.The ultra-high speed train in vacuum pipeline runs in the pipeline with thin gas,which greatly reduces the air resistance of the train.It is the best solution to solve the resistance problem and realize the train speed increase.Therefore,it is very necessary to study the aerodynamic shape of vacuum pipeline ultra-high speed train.In this paper,the aerodynamic shape of a three car high speed train is analyzed and optimizedFirstly,the simplified high-speed train models of duckbill,ellipsoid and shuttle head are established,and the pre-processing work of defining calculation domain,dividing calculation domain grid and setting boundary conditions are carried out for them.The aerodynamic performance of trains with different head types running in vacuum pipeline is simulated and calculated.According to the velocity field,pressure field and turbulence field,the aerodynamic performance of three kinds of train heads in vacuum pipeline is compared It is found that the train with ellipsoidal head has better aerodynamic performance when running in vacuum pipeline.Secondly,using ANSYS Fluent established the three-dimensional fluid simulation analysis model of vacuum pipe,thin air and ellipsoidal head type high-speed train.According to the relevant literature of vacuum pipe type high-speed train,the flow field simulation calculation of ellipsoidal head type ultra-high-speed train under different vacuum pipe blockage ratio,different vacuum degree and different running speed was carried out,and the influence of vacuum pipe blockage ratio,air pressure in vacuum pipe on the flow field was analyzed And the influence of train running speed on train aerodynamic performance.The simulation results show that the aerodynamic resistance of the train increases with the increase of the drag plug ratio when the pressure of the vacuum pipeline and the running speed remain unchanged,and the greater the drag plug ratio is,the greater the rise of the aerodynamic resistance is,and the smaller the drag plug ratio is,the less the impact the aerodynamic performance of the train will have;when the pressure of the pipeline is reduced to 0.01 atmospheric pressure,the pipe pressure will have an impact on the aerodynamic resistance;the running speed of the train will increase There is a linear positive correlation between the degree of freedom and the aerodynamic resistance of the train.Finally,based on Isight optimization platform,the multi-objective optimization with the lowest aerodynamic resistance and the closest aerodynamic lift to zero is carried out.Taking the ellipsoidal head as the initial optimization model,seven groups of optimization variables are selected in the X,y and Z directions of the train head to realize the omni-directional control and adjustment of the train head,and the Latin hypercube method is used to automatically generate the optimal samples The automatic optimization process of ultra-high speed train head shape is realized by combining the finite element software Hyper Mesh,automatic deformation software sculptor and fluid analysis software FLUENT,and the calculation results of aerodynamic resistance and aerodynamic lift of ultra-high speed train are obtained.The response surface relationship and interaction effect between the optimization variables and the target are analyzed,and the optimal solution set of the aerodynamic performance of the ultrahigh speed train is calculated by using the genetic algorithm NSGA-Ⅱ.The aerodynamic drag reduction rate of the optimized train is 36.8%,and the aerodynamic lift drag reduction rate is38.1%.The aerodynamic performance of the optimized train head has been greatly improved.This paper can provide effective basis and information for the head shape design and flow field characteristics of vacuum pipeline ultra-high speed train,and also provide some reference for the multi-objective optimization problem in the similar rarefied gas environment.