High-Fidelity Transient Thermal Modeling of a Brake Corner

There is an increasing interest in transient thermal simulations of automotive brake systems. This paper presents a high-fidelity CFD tool for modeling complete braking cycles including both the deceleration and acceleration phases. During braking, this model applies the frictional heat at the interface on the contacting rotor and pad surfaces. Based on the conductive heat fluxes within the surrounding parts, the solver divides the frictional heat into energy fluxes entering the solid volumes of the rotor and the pad. The convective heat transfer between the surfaces of solid parts and the cooling airflow is simulated through conjugate heat transfer, and the discrete ordinates model captures the radiative heat exchange between solid surfaces. It is found that modeling the rotor rotation using the sliding mesh approach provides more realistic results than those obtained with the Multiple Reference Frames method. Because of the significant computational requirements involved, the scope of this paper is limited to a single braking event of a brake subsystem in an environmental chamber. Corresponding dynamometer tests have also been performed to validate the simulation results. It is shown that the agreement between the measured and simulated data is acceptable. The thermal energy partitioning between rotor and pad predicted by the model confirms that almost all of the frictional heat is directed from the friction interface into the rotor. The uneven temperature gradients in the brake rotor are quantified and the sensitivity of the simulation results with respect to key modeling parameters is discussed. The presented simulation model can be implemented in several commercial CFD codes. While Fluent was used in this study, the comparison with other CFD software will be the subject of future work.