Optimisation of Internal Shape of Disc Brake to Increase Ventilation

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Addis Ababa University


Brake system has always been one of the most critical active safety systems. Brake cooling is further an important aspect to consider for brake disc durability and performance. In railway transport, braking the train without overheating the discs and losing the braking capacity is a matter of safety. In urban railway transport, like AALRT, the speed of trains is confined to the lower limit because it is difficult to decelerate and stop the train within the short distance of the closely spaced stations. During braking, all the kinetic energy of the train is changed into frictional and finally to heat energy which causes the brake to overheat and lose its braking capacity. To prevent the occurrence of brake heating, brake rotor must be designed such that it ensures sufficient heat dissipation. The special structure for ventilation not only increases the surface area of the disc rotor but also enhances airflow around the surface of the disc to achieve a higher convectional heat transfer. In this research a fluid flow CFX, Thermal and Stress analysis is done on three types of disc brakes; a curved vane and two types of pin vented rotors using finite element method. The fluid flow CFX is used to calculate the cooling effect of the moving air relative to the brake rotor. The pin vented rotors have elliptic cross section with different geometric parameters. Pin vented rotor creates turbulence and gives higher heat transfer coefficient. It has been observed that the pin vented disk brake with elliptic cross section pins which has higher eccentricity has good heat dissipation characteristics. Changing the geometry of the pins increasing the eccentricity of the elliptic cross section creates larger surface area to volume ratio and less obstruction to the air flow which enables to have higher convection heat transfer coefficient. After emergency braking of AALRT with maximum track gradient of 3.15 0 and overload condition, a maximum temperature gradient of 334.95 0 C is achieved with one of the pin vented brake which has higher eccentricity while it is 340.93 o C and 346.89 o C for the second type of pin vented brake and the curved vane rotors respectively.



Disc Brake, Ventilation, Brake cooling, AALRT