Development of a High Fidelity CAE Model for Predicting Brake System Temperatures

In order to specify a brake system that will have robust performance over the entire range of expected vehicle drive cycles it is vital that it has sufficient thermal inertia and dissipation to ensure that component temperatures are kept within acceptable limits. This paper presents a high fidelity CAE (computer aided engineering) technique for predicting the temperature of the front brake and the surrounding suspension components whilst installed on vehicle. To define the boundary conditions the process utilizes a coupled unsteady CFD (computational fluid dynamics) and thermal solver to accurately predict the convective heat transfer coefficients across a range of vehicle speeds. A 1-D model is used to predict the brake energy inputs as well as the vehicle speed-time curves during the drive cycle based on key vehicle parameters including wide-open-throttle performance, drive train losses, rolling resistance, aerodynamic drag etc. The convective heat transfer coefficients are interpolated based on the vehicle speed curve to generate the time varying convective heat transfer coefficients for each component. These boundary conditions are then applied to a transient thermal model consisting of the brake and suspension system. To demonstrate the advantage of using a fully transient method over a steady state cooling and 1-D modeling approach a case study has been performed examining the relative performance of single piece conventional iron rotors and two piece discs fitted to the Jaguar XE saloon car. The results are validated against vehicle test data, showing a much stronger correlation between the predicted and experimental brake disc temperatures for the full transient model compared to the steady state cooling