Brake Duty Cycle Simulation for Thermal Design of Vehicle Braking System 2013-36-0015
Successive braking of the vehicle, hereinafter referred as brake duty cycle, can elevate the temperature of the brake disc to a very high level. Such high temperatures reached in brake discs can lead to vaporization of the brake fluid if the vehicle is at rest after the brake duty cycle. Excessive temperature operation of the brake disc can also lead to thermal cracks, judder, brake fade, wear and reduce braking effectiveness. Simulation tools can be used to predict the excessive temperature reached during successive braking event. After visualizing the complex flow field over the brake system and analyzing the heat transfer from brake system, simulations can be employed at the early design stage to optimize the design for more airflow over brake discs thus reducing the high temperatures and associated brake fade.
In this paper, a CFD model of the vehicle with brake system is coupled with a thermal solver at braking and acceleration velocities. Heat input due to conversion of Kinetic Energy of the vehicle is calculated from the velocity fluctuations during braking and acceleration events. Calculated heat input along with heat transfer coefficients (HTC) variation due to speed changes are used in a standalone thermal simulation to predict the temperature of entire brake system including brake disc after each braking event in a ten brake stop brake duty cycle. Use of solid mesh for brake disc and neighboring parts such as hub and rim, further enhances the temperature prediction by modeling the conduction during heat up and cooldown event precisely. Multiple design iterations can be executed in a rapid turn-around time to analyze and improve the brake cooling performance.