Influence Of Wind Resistance Braking Forms On Braking Performance Of High Speed Train

With the continuous improvement of the running flow velocity of high-flow velocity trains in China,safe and reliable braking plays an important role in the safe operation of trains.The wind resistance braking is to use the differential pressure before and after the wind resistance plate to provide braking force.The higher the train flow velocity,the more obvious the braking effect of the wind resistance braking device.It has the characteristics of reducing wheel-rail loss,simple structure and green environmental protection.Therefore,it is of great significance to improve the braking performance of high-flow velocity trains by studying the braking performance of different wind resistance braking forms and selecting the appropriate wind resistance braking form according to the flow velocity.In the present thesis,the braking characteristics of three different braking forms affected by train wind at different flow velocitys are studied.Firstly,the influence of the three braking forms of ’ butterfly ’,’ gill ’ and ’ combined ’ on the braking force of high-flow velocity trains at different flow velocitys is studied with the increase of the number of brake plates,and the braking performance of the three braking forms at different flow velocitys is compared and analyzed.Secondly,the time domain characteristics of aerodynamic parameters under different vehicle flow velocitys,braking forms and number of brake plates are discussed.The vortex street phenomenon and inter-plate interference phenomenon are understood by analyzing the external flow field,and the turbulent kinetic energy under different conditions is analyzed.Finally,the shape of the brake plate is optimized,and the aerodynamic characteristics and braking characteristics of the brake plate before and after optimization are compared.The reasons for the increase of flow field characteristics and braking force before and after optimization are analyzed,and the feasible suggestions for the structural optimization of the wind resistance brake plate are put forward.The results show that :(1)The braking force of the three braking forms is proportional to the speed of the vehicle.The vorticity of the flow field is analyzed,indicating that the vortex street is generated when the airflow hits the brake plate.The braking force of butterfly and gill brake reaches 35.26 k N and 57.66 k N when the number of brake plates reaches five groups,while the braking force of combined brake reaches 68.71 k N when each vehicle is installed with three sides-2 and five groups of brake plates,almost no longer changing.(2)If you want the wind resistance braking performance to achieve the desired effect,when the train speed is300km/h,the gill brake form is adopted,and three sets of brake plates are installed on each vehicle.When the combined brake form is adopted,each vehicle installs two sides-1 on the three sets of brake plates.At 350 km/h,if the butterfly brake is adopted,two sets of brake plates are most suitable for each vehicle.If the gill brake is adopted,one set of brake plates is most suitable for each vehicle.At 400km/h,the butterfly braking form is selected,and a set of brake plates can be installed on each vehicle to meet the braking requirements.(3)With the change of the rotation angle of the wind resistance plate,based on the Q criterion,the vortex structure at 0 ° is compared.When the combined brake plate rotates 12 ° counterclockwise,the vortex structure generated by the two brake plates on both sides is almost not interfered with the vortex structure of the upper brake plate.(4)The butterfly and gill type reach the maximum turbulent kinetic energy difference at 11 m and 10.5 m from the nose tip of the head.The maximum turbulent kinetic energy difference between the upper and both sides of the brake plate of the combined brake reaches the maximum turbulent kinetic energy difference at 17.3m and 11 m from the nose tip of the head.(5)Compared with the rectangular brake plate,the total braking force of the scallop brake plate increases by 2.5%,and the braking effect of the brake plate is better.