Vehicle brake cooling performance is one of the most important parameter in vehicle design and development phases. There are certain requirements that needs to be met regarding with the maximum design temperatures of components even in the worst case scenarios. Braking system components are selected in the early design phase of vehicle development and there needs to be a robust methodology to estimate disc, pad and brake fluid temperatures before vehicle testing. The high financial impact, the long development time, prototype parts readiness timing and on-road measurement devices' instrumentation difficulties play a leading role for alternative solutions. Automotive industry work on alternative validation methods via computer aided simulations whose development is depending on the power of computers. In this study brake cooling performance is empirically calculated and results are compared with the vehicle test data. Convective heat transfer coefficients (h) are obtained via CFD methods and simulations are performed with Ansys Fluent v18.2. Braking time, vehicle velocity, brake system component geometries, dimensions and materials properties are taken into account for the mathematical model. Steady state simulations are performed on 3D CFD tool for both brake and release scenarios and the mathematical model calculations. This is the crucial to reach exact temperature distribution on the brake system components. In this respect the theoretical calculations is not adequate to estimate convective heat transfer coefficients. The surrounding systems design has to be taken into account for the convective heat transfer coefficient determination. Examples can be accounted as body exterior components (speed lip, wheel arch liner, etc.), wheel rim shape and cover design, brake tubes routing and all other parts packaging around the brake system. Obtained heat transfer coefficients (h) are implemented into 1D mathematical model which comprises disc, rim, pad, pad back plate, piston, brake fluid and calliper. The results of test and 1D tool are well matched. The main target in this study is to predict the peak temperature value on the brake disc, brake pad and brake fluid that can be potentially used for the development of driver assistance systems such as brake temperature warning. Optimized one vehicle design can be tested according to 1D mathematical model. This potentially brings more than % 50 cost reductions during brake cooling system validation testing.
Yasin Koray Hacisalihoglu, Ford Otosan, Product Development, Turkey; Yigit Dalga, Bayrak Akca, Cenk Dinc