带排扭矩条件下湿式制动器流体的三维温度场和传热规律分析

3D theoretical distributions of the temperature and heat transfer of ATF in wet brakes applied by drag torque

湿式制动器是重型车辆制动系统的核心部件,对车辆安全具有关键影响.本文以制动摩擦副间隙的冷却液压油(ATF)为研究对象,考虑非制动作业时带排扭矩条件下液体黏性摩擦和稳态层流流动特征,利用积分方法建立了ATF的能量方程,获得了能同时满足轴向和径向边界条件的三维温度和热流密度显式解析表达式,由简化动量方程和三次多项式分布假设还获得了油膜径向速度和压强的理论解.将流体压强和温度的理论模型与以往试验对比,我们发现解析解与试验结果具有较好的一致性.此模型可推广用于液黏离合器和液黏测功机等其他HVD装置中ATF速度和温度场的理论预测.

The wet multi-disk brakes are important braking components of automotive and off-highway drivetrains, which have a crucial influence on the safety of heavy-duty vehicles. The energy equation is proposed in steady laminar flow of the automotive transmission fluid(ATF) through an integral method, considering the disengaged drag torque condition owing to hydroviscous drive(HVD). The closed-form analytical solutions for the three-dimensional(3 D) temperature and convective heat flux fields, together with those of the temperature rises of separator and friction plates, are obtained for ATF, respectively, which can satisfy all the boundary conditions for both radial and axial directions of oil film. The analytical expressions of the radial velocity and pressure of ATF are also obtained based on the simplified Navier-Stokes equations and the approximation of cubic polynomial distribution. By comparing the theoretical model of fluid pressure and temperature with previous experiments, we find that the analytical solution is in good agreement with the experimental results. The analytical methods of 3 D velocity, temperature and heat flux proposed might have the potentials to be extended to predict those of HVD devices such as wet clutches and dynamometers.