高速列车转向架区域冰雪堆积仿真研究及防治措施

When high-speed trains operate in cold regions and experience rain and snow weather, ice and snow buildup can occur on the surface of the bogie, which affects the dynamic performance of the suspension components and braking system, thereby affecting the safety of train operation. The formation of ice and snow buildup is due to the train passing through a snowy road or snowfall environment. Under the effect of the train's wind, snow particles will follow the airflow into the bogie area. The flow field structure in the bogie area is complex, with many low-speed and vortex regions, which causes snow particles to be unable to be discharged and have adhesiveness, making it easy to adhere to the surface of the bogie and form snow accumulation. Under the action of the heating components of the bogie, such as the motor and gearbox, snow particles will melt into liquid water, which not only increases the capturing ability of snow particles but also easily condenses into ice in a low-temperature environment. Therefore, in order to study the process of ice and snow buildup in the bogie area and propose corresponding prevention measures, this paper establishes a simulation model of ice and snow buildup, studies the motion characteristics and deposition characteristics of snow particles considering the rotation of snow particles and the shape of snow particles, and explores the influence of different icing parameters on the icing of the bogie. Finally, the effect of active blowing on the ice and snow buildup in the bogie area is studied, and the blowing speed is optimized to provide a reference for preventing ice and snow buildup in the bogie area. The main research contents and conclusions are as follows:

(1) A complex bogie and simplified car body model are established. Based on the unsteady Reynolds averaging algorithm and the discrete phase model coupling method, the airflow and snow flow at the bottom of the train are solved. A custom function is used to determine whether snow particles can stably settle after colliding with the surface of the bogie, and the influence of snow particle rotation on the motion trajectory and deposition characteristics of snow particles is analyzed. The results show that changes in the velocity gradient near the wheelset and uneven pressure distribution in the bogie area will further accelerate the rotation of snow particles, resulting in the generation of Magnus force, which changes the motion trajectory of snow particles and the deposition position. With the increase of train speed and snow particle diameter, the difference in the distribution of snow accumulation caused by snow particle rotation becomes more obvious.

(2) Based on the shape correction theory, different shaped snow particles, such as dendrites, hexahedrons, and tetrahedrons, are customized for their motion equations, and the motion and deposition characteristics of snow particles under different snowfall environments and crosswind environments are analyzed. The results show that considering the irregular shape of snow particles, the resistance of snow particles in the flow field is large, and it is not easy to be discharged from the bogie area with the airflow, so the number of snow particles staying in the bogie area increases, resulting in an increase in snow accumulation. When the amount of snow particle incidence increases or decreases tenfold, the snow accumulation of each part of the bogie decreases or increases tenfold accordingly, so a reasonable amount of snow particle incidence can be chosen for regular research in the case of limited computing resources. Under the crosswind environment, because the airflow can directly impact the bogie, the overall flow velocity in the bogie area is increased, and the wall shear velocity is increased, which reduces the probability of snow particles settling stably, so snow accumulation mainly occurs on the leeward side of the bogie, and there are almost no snow particles settling stably on the windward side.

(3) The snow accumulation on the heating components of the bogie is calculated using the capture criterion and the full capture wall boundary condition. After the calculation time exceeds 2 seconds, the ratio of the snow accumulation on the heating components to the total snow particle flow rate in the bogie area tends to a constant value, and the melting amount of snow particles in the bogie area is hypothesized. The influence of liquid water content, snow particle content, droplet diameter, train speed, and calculation time step on icing is analyzed. The results show that the liquid water content increases the capturing ability of the wall to snow particles, resulting in an increase in icing. The smaller the droplet diameter, the easier it is to enter the bogie area and form a liquid film on the surface of the bogie, which increases the icing rate. The increase in train speed increases the normal velocity of droplets and snow particles colliding with the wall, increases the collection efficiency, and increases the ice growth rate. The single-step icing method cannot update the flow field in real-time and ignores the change in the collection efficiency of droplets and snow particles, so there is a significant difference between the changes in icing amount, icing shape, and aerodynamic force and the multi-step icing method.

(4) Although the arrangement of the deflector plate can slow down the rate of ice and snow buildup in the bogie area, it increases the running resistance of the train. Therefore, a head and 1/2 intermediate car model is established, and the top of the bogie cabin is designed as a blowing port to suppress the uplift of snow particles, thereby reducing the number of snow particles entering the bogie area and achieving the effect of slowing down ice and snow buildup. At the same time, due to the rotation of the wheelset and the obstruction of the bogie components, most of the airflow will directly impact the front wall of the bogie cabin, forming a large positive pressure zone at the front end of the bogie, which increases the pressure difference resistance. Since the direction of action is opposite to the direction of the resistance the train encounters during operation, it reduces the running resistance of the entire train to some extent. In order to reduce the energy loss caused by blowing, the results of different blowing speeds in each bogie area are analyzed, and it is shown that increasing the blowing speed of the front end bogie of the head car can not only achieve a good drag reduction effect, but also discharge most of the snow particles at the bottom of the train to both sides of the track, reducing the number of snow particles entering the subsequent bogie areas and achieving a better effect of preventing ice and snow buildup.