| With the increasing speed of high-speed trains,the problems of aerodynamics and noise are particularly prominent.When the train exceeds 200km/h,about 70% of its power is used to overcome air resistance.The pantograph is mounted on the top of the train.The pantograph head is the main force component of aerodynamics and the main factor affecting the aerodynamic noise of the pantograph of the whole high-speed train.Therefore,considering the influence of aerodynamics on pantograph,the optimization of pantograph shape structure and aerodynamics is of great significance to the development of high-speed pantograph.In this paper,the pantograph head of high-speed train is taken as the research object,and the aerodynamic characteristics of the pantograph head are modeled by the fluid mechanics calculation software Fluent.Based on the idea of bionics,the structure of pantograph head was optimized,and a new type of pantograph head structure with wavy lower surface was proposed.The influence of the structure of the lower surface of the bow head on the aerodynamic characteristics was explored to achieve the effect of drag reduction and noise reduction.First of all,in order to verify the accuracy of the turbulence model,the flow around a cylinder and a square column were taken as the research objects for model verification.The numerical simulation results are in good agreement with the previous experimental results,indicating that the Transition SST turbulence model can be used for numerical simulation of the 2-D bowhead model.Then,based on the CX-NG pantograph,the traditional square bow head model was established,and the simulation calculation was carried out.Second,its pantograph bow the head surface structure,the retrofit design will be the lower part of its shape optimization for concave and convex wavy,analyze the simulation using Fluent software under different speed,with different speed,the flow field under the cloud will bump type bow bow the head and the traditional square head aerodynamic characteristics of qualitative comparison,analysis the influence of different flow field structure shape.Through comparative analysis,it is found that using the convex pantograph head can achieve the best drag reduction effect.Under the three speeds,the drag coefficient Cd is reduced by 10.26%,11.23%,12.69%,and the drag is reduced by 10.96%,11.63%,12.76%,respectively.Then,the pantograph head models with different length-width ratios were established and compared with the square bow to explore the influence of length-width ratio on the aerodynamic characteristics of the pantograph head.The results show that the drag-reducing effect can be achieved by using a 4.5:1 type bow head with an aspect ratio of 4.5:1,and the inhibition effect of rear trailing vortices is the best,and no trailing vortices can be generated behind the bow head.Finally,the three-dimensional models of the convex pantograph head and the traditional square pantograph head with the best optimized performance are established to carry out noise and aerodynamic simulation.Compared with the two-dimensional simulation results,the aerodynamic and noise characteristics as well as the influence mechanism on the wake vortex are analyzed.It is found that the numerical results of the simulation are larger than that of the two-dimensional simulation results,but the overall variation trend of the results is basically the same as that of the two-dimensional simulation results.At three speeds,using convex structure can reduce noise by 0.73 d B,1.42 d B and 2.37 d B,respectively. |
