Numerical investigations of brake cooling performance
Examensarbete för masterexamen
Automotive engineering (MPAUT), MSc
In the modern world, tough legislation on lowered emissions, leads the manufacturers to apply innovative strategies which involve aerodynamic improvements, such as covered rims. A covered rim is a good solution from an aerodynamics point of view, but poses serious constraints on the cooling performances of the brake discs, as it somewhat a ects the cooling ability of the brake discs. To prevent critical situations that could lead to safety issues, such as decreased friction coefficients, brake hot-judder, increased wear, thermal cracking or even brake uid boiling, the heat must be dissipated and hence, there is a demand for efficient cooling of brakes. Traditionally, brake performance investigations were performed experimentally. However, with the computational power available today, these experiments can be simulated to save physical test time and resources. CAE simulations have shown good correlation with experimental results and can aid in incorporation of design changes at early stages of development. At Volvo Cars, these simulations are carried out using co-simulation where the aerodynamic and thermal solutions are calculated in parallel to get an estimate of the cooling performance. This work examines the possibility to run mono-simulations using the CFD tool Star-CCM+ to test different approaches and investigate important parameters for brake disc cooling performance. During the project, investigations were carried out pertaining to: Various factors affecting the cooling performance Applicability of different Heat Transfer Coefficient definitions Effects of changes in brake disc design and rotation direction Influence of parts around the brake disc Approaches for brake cooling simulations using Star-CCM+ Some important observations made during the course of the project suggests that: the Virtual Local Heat Transfer Coefficient can be used for early comparison investigations which saves simulation time, the performance behavior due to rotational velocity variation can be predicted by linearization of the Heat Transfer Coefficient and there is an optimal point in variation of the design parameters where the best cooling performance of a brake disc type is achieved. This work was carried out at Chalmers University and with the support and valuable feedback from the brakes department at Volvo Cars.
Strömningsmekanik och akustik , Hållbar utveckling , Transport , Fluid Mechanics and Acoustics , Sustainable Development , Transport