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

Abstract:

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 (3D) 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 equation 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 3D 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.