Numerical Study On Convective Heat Transfer Characteristics On The Wheel Surface Of Heavy-duty Train

With the continuous development of economy,my country's railway transportation continues to move in the direction of high speed and heavy load.When the heavy-duty train is braked,the tread brake is generally used.During the braking process,the wheels will generate a higher temperature.When a certain heating limit is reached,the wheels will be damaged.A large amount of heat generated in the braking process,most of which are absorbed by the wheel.Therefore,it is of great significance to study the distribution law of temperature and convection heat transfer coefficient of wheels under emergency braking conditions.This paper mainly studies the distribution law of the temperature field and convective heat transfer coefficient of each surface of the wheel when the heavy-duty train performs emergency braking at the initial speed of 120km/h.The main work is as follows: First,build a three-dimensional model of the wheel,import the model into the Geometry module in ANSYS Workbench,create a fluid domain in it,and name the solid model and fluid domain;then mesh it;finally,import the divided mesh into fluent,set the boundary conditions,determine the solution step and the number of solution steps,and then start the calculation.After the calculation,the velocity field,temperature field and convective heat transfer coefficient of the wheel in the braking process are obtained.The conclusions are as follows:(1)In the emergency braking,the highest temperature of the wheel appears in the area where the brake shoe contacts the tread directly,and the temperature of the wheel tread is higher than other areas.(2)The temperature of the wheel tread reaches the maximum value of 478.45 K when the train brakes for 14 s,and then begins to decrease.During the entire braking process,the average temperature of the wheel tread increases first and then decreases with the braking time.(3)The deeper the radial depth from the wheel tread,the lower the temperature value reached,the later the time point at which the maximum temperature occurs,and the smaller the maximum temperature value reached.(4)The convection heat transfer coefficient is larger in the upper part of the windward tread,and the lower part is smaller;At the end of braking,the maximum convective heat transfer coefficient of the wheel tread and both sides of the tread appears in the upper part of the windward tread,and in the lower part of the windward tread,the convective heat transfer coefficient is the smallest.In the other areas of the wheel tread and both sides of the tread,the distribution of the convective heat transfer coefficient is relatively uniform.(5)On the spokes,the convective heat transfer coefficient on the inner side of the wheel is smaller than that on the outer side.(6)In the windward zone and the leeward zone of the axle,there are two zones with large convective heat transfer coefficient,and the distribution of convective heat transfer coefficient on the hub is more uniform than that on the axle;At the end of braking,in the windward area,the convection heat transfer coefficients on the hub and axle are larger,in the leeward area,the convective heat transfer coefficient are smaller and more uniform.(7)With the increase of braking time,the coefficient of convective heat transfer on each surface of the wheel gradually decreases.With the progress of braking,the difference between the coefficient of convective heat transfer on each surface of the wheel becomes smaller and smaller.By the end of braking,the coefficient of convective heat transfer between each surface has basically become the same.