Evaluation and Prevention of Brake Drum Freezing by Aerodynamic Measures

The use of drum brakes in Battery Electric Vehicles (BEVs) offers numerous benefits, including energy efficiency, reduced brake dust emissions, and reliable performance under challenging weather conditions. The capability of regenerative braking reduces the friction brake application frequency in BEVs and therefore the brakes can be prone to corrosion and performance degradation especially considering conventional disc brake systems. The closed design of a drum brake prevents corrosion of the friction-components by sealing out water, dirt or snow. A common sealing concept is performed with a labyrinth between the gap of the rotating drum and the axle mounted backplate. A hermetically isolation of water and snow ingress into the drum cannot be achieved with this concept, so additional aerodynamic measures are necessary to deflect the air/water path and protect the inner brake components. Additionally, interfaces like wheel cylinders, electric park brake parts, brake shoe pins, and axle mountings can potentially lead to leaks on the backplate. This study highlights the impact of water/snow ingress on the example of a frozen parking brake during cold climate on road testing. Through scientific investigation using the state-of-the-art fluorescence method, drum leakages were visualized, and the extent of water ingress was measured. Multiple multiphase CFD simulations supported the design phase of the aerodynamic measures. Subsequently, the vehicle was cooled down to -15 °C to simulate the cold climate test conditions. The frozen parking brake situation could be reproduced with this method, and beneficial aerodynamic and sealing measures were extrapolated to avoid the drum brake from freezing. The tests were conducted in the FKFS Thermal Wind Tunnel, a wind tunnel comprising a two-axle-dynamometer and water irrigation systems with UV illumination.