流场分析在地铁车辆踏面制动温度场仿真中的应用

Flow-field Analysis of Temperature Field of Subway Vehicle Tread Braking

针对地铁车辆踏面制动,建立了车轮车轴的轴对称简化几何模型,并且根据温度梯度的分布特点划分了疏密不同的有限元网格。根据车辆的加速启动、匀速运行、减速制动和进站停止4种不同运行状态,建立了车轮车轴的热边界条件。采用均布热源法计算制动过程中输入踏面摩擦接触区的热流密度。利用CFD软件对车辆不同运行速度下的车轮车轴附近流场进行稳态计算,进而获得不同速度下车轮车轴各表面对流换热系数的平均值,并利用最小二乘法拟合出平均对流换热系数与速度的函数关系。最后针对国内某一地铁线路,计算了连续两次紧急制动和经过9个车站的模拟运营制动(纯空气)两种工况下的车轮车轴温度场,得到了最高温度点的温度值随时间的变化曲线。

For the subway vehicle tread braking, a simplified axisymmetric geometric model of the wheel and axle is established. The model is meshed with different element size according to the distribution characteristics of the temperature gradient. Based on the four different running states of the vehicle, including starting, uniform running, braking and parking, the thermal boundary condition of the wheel and axle is set up. The heat flux density entering the friction contact zone of the wheel tread during the braking process is calcu lated using the uniformly distributed heat source method. The steady state flow field near the wheel and axle under different vehicle rumxing speed is calculated using the CFD software, and then the average convective heat transfer coefficient of each surface of the wheel and axle is obtained. Further, the function relationship between the average convective heat transfer coefficient and the vehicle running speed is fitted out using the least square method. Finally, aiming at a domestic subway line, the temperature field of two consecutive emergency braking and simulated operation braking （pure air） of passing through nine stations is calculated, and the changing curve of the temperature with time of the highest temperature point in the model is obtained.