Research On Multi-Objective Optimization Of Pantograph Cabin Aerodynamic Performance Of High-Speed Train

The pantograph of the high-speed train is installed on the top of the vehicle,and its main function is to obtain electrical energy from the contact network for train operation.Pantograph is mainly composed of skateboarding,rod upper arm,lower arm lever of thin rod type parts,such as,when the train running at a high speed around the pantograph can form relatively complex turbulent flow field.In order to improve the flow field around the pantograph structure,and extend the service life of pantograph,usually in the pantograph locale streamline guiding device.However,after installing the pantograph guide device,the flow field structure at the pantograph will naturally change to a certain extent.Therefore,in order to study the influence degree of the diversion device on the aerodynamic performance of the pantograph,it is necessary to carry out the shape comparison selection and optimization of the diversion device of the pantograph.Firstly,the structure of the original pantograph cabin of a certain high-speed train is analyzed,and on the basis of it,three comparison schemes of rectangle,bathtub and oval are proposed.For single-vehicle working condition on open line,the train speed is set to 200km/h,250km/h,300km/h and 350km/h respectively,and the simulation calculation of aerodynamic characteristics of four different pantograph cabins is completed.The calculation results show that although there are differences in the aerodynamic lift of the pantograph corresponding to the four pantograph pods when the pantograph is open and closed,the aerodynamic drag corresponding to the original pantograph pod is the least.After comprehensive evaluation,among the four different shapes of pantograph module,the original pantograph module has the best aerodynamic characteristics.In order to further optimize the aerodynamic characteristics of the original pantograph module,it is very important to select a suitable high-precision approximate model.Therefore,the train running speed was set at 350km/h for single-vehicle operating conditions on the open line.The response surface model,radial basis neural network model and Kriging calculation model were established respectively,taking the main structural parameters of the original pantograph cabin as design variables and the aerodynamic drag and lift force of the pantograph opening operation as response targets.The results indicate that the fitting accuracies of the three approximate models for the aerodynamic resistance of the pantograph are 0.932,0.878 and0.903 respectively,and the fitting accuracies of the aerodynamic lift are 0.929,0.916 and 0.871 respectively.Therefore,it is reasonable to select the response surface approximation model with higher accuracy for the subsequent pantograph cabin multi-objective optimization.Finally,on the basis of the response surface approximation model,adopt the NSGA-Ⅱ algorithm on the pantograph tank archetypal pneumatic performance of multi-objective optimization.With structural parameters such as depth,longitudinal length and inclination Angle of the original pantograph cabin as optimization variables,and the absolute value of aerodynamic drag and aerodynamic lift when the pantograph is opened as optimization objectives,six relatively optimal pantograph cabin models are obtained through optimization calculation.The results show that the optimized model obtained after multi-objective optimization can improve the aerodynamic drag and lift absolute value of pantograph to some extent.Among them,the aerodynamic drag corresponding to the optimized model E is the least,which decreases by 4.3% compared with before optimization.The absolute value of the aerodynamic lift of the pantograph corresponding to the optimization model C is the smallest,which is reduced by 10.0% compared with that before optimization.