Multi-objective Optimization Design Of Locomotive Shape Based On Free Form Deformation

The shape of the train is directly related to its aerodynamic parameters such as aerodynamic drag and aerodynamic noise.With the increasing speed of high-speed trains,their aerodynamic problems are becoming increasingly significant.In order to maintain good aerodynamic characteristics of high-speed trains,this paper adopts the aerodynamic drag,aerodynamic lift and far field aerodynamic noise at the running speed of 250km/h,300km/h,350km/h and 400km/h respectively,and establishes a multi-objective optimization model of high-speed train locomotive to optimize the locomotive shape at each speed.By studying the optimization law of the shape of the locomotive at different speeds,it provides data reference for the combination of the high-speed train locomotive and the intelligent deformation technology,so that the locomotive shape of the high-speed train can automatically change in real time with the speed changes,and always maintain the optimal aerodynamic performance of multiple objectives.The main research contents of this paper are as follows:Firstly,the aerodynamic simulation is analyzed on the high-speed trains.The geometric model of high-speed train with three groups is established,and the flow field computing domain is established by Hyper Mesh software.The Fluent software calculated the steady-state calculation domain of the flow field,analyzed the pressure distribution characteristics and sound power level distribution rules of the front part,and defined the position where the front shape variable should be selected.Then the locomotive surface is calculated as the noise source,analyzes the far field noise rule,to provide a basis for the optimization of high-speed train head.Secondly,combining free form deformation and optimization method to carry out multiobjective optimization design of train head types at different speeds,and study the change law of front shape.The Sculptor software based on free form deformation is used to set the control point of shape variables in the key parts of the front affecting the aerodynamic characteristics.Sculptor and Fluent are integrated with Isight software to establish optimization platforms for sample collection and automatic aerodynamic calculation.The obtained data results are constructed as a Kriging model to obtain nonlinear response relationships between optimization targets and design variables,and the NCGA multi-objective genetic algorithm is used to find the optimal solution of the agent model.In this way,the front aerodynamic shape of the train is optimized when the running speed are 250km/h,300km/h,350km/h and 400km/h respectively.Finally,the intelligent deformation study of the head type is carried out by means of cubic spline interpolation,so that the high-speed train always maintains better aerodynamic performance.The results show that compared with the original train,the aerodynamic lift of the intelligent deformed front train is slightly increased,the aerodynamic drag is reduced by4.41%～6.22%,the far field aerodynamic noise is reduced by 2.99%～4.29%,and the overall aerodynamic performance is better improved.