Unsteady aerodynamic characteristics and dynamic performance of the high-speed train in plate braking under a crosswind

Abstract

Abstract As one of the key technologies of the train, the braking system plays a vital role in ensuring the safe operation of the train. Plate braking has the characteristics that the higher the train speed, the better the braking effect, and it can be used as one of the options for emergency braking of the high-speed train. The dynamic grid technology is used to realize the plate movement, and the unsteady aerodynamic characteristic simulation of the train in plate braking process is realized based on the IDDES with SST k-w turbulence model. The formation and evolution of the flow field in the process of plate braking are analyzed by the visualization technology, and the influence law of plate opening on the aerodynamic forces of each car under the crosswind is explored. By loading the aerodynamic forces into the vehicle system dynamics model for calculation, the safety indexes (derailment coefficient and wheel load reduction rate) of the plate braking train under crosswind with different speeds are obtained. The results show that the rapid opening of the plate provides a large braking force for the train, but it destroys the stability of the flow field around the train, especially the flow field above the train, and the above phenomenon further aggravated by crosswind. The aerodynamic force distribution of each car in the train was significantly changed by crosswind, the proportion of the lateral force of the head car in the train is significantly increased, and the aerodynamic forces of each car were further increased by the opening of the plate. From the perspective of vehicle dynamics performance, with the increase of crosswind speed, the derailment coefficient and wheel load reduction rate of each car increase obviously, and even derailment and overturn occur. Under the crosswind, the dynamic performance of the head car is the worst, and it was further deteriorated by opening of the plate. The impact of the tail car is relatively small, and the dynamic performance of the head car can be used to evaluate the safety of the train. It is recommended to avoid opening the plate of the head car in strong crosswind.