Abstract
The aim of the investigation is to find the ways of maximising heat dissipation from commercial vehicle brakes in an operationally acceptable and economically viable way. All three modes of heat dissipation have been analysed in great depth and different methods have been tried in order to improve brake cooling. The design features of the disc, carrier and wheel and their interfaces have also been analysed. Furthermore, a special Spin Rig has been constructed and used for the experimental work. It proved to be very valuable equipment, very sensitive in detecting the changes in heat dissipation due to small modifications of the brake and/or wheel assembly design. The influence of brake cooling parameters on the disc temperature was investigated by finite element modelling of a long drag brake application.
It was shown that an aluminium gasket or a high thermal conductivity paste applied at the disc/wheel carrier contact surface drastically reduce thermal contact resistance. However, despite the wheel carrier being of substantial thermal capacity, no significant increase in conductive heat dissipation could be achieved. Only the aluminium carrier, which was modelled to be of the same thermal capacity as the cast iron carrier, provides somewhat improved heat dissipation by conduction.
Measured convective cooling showed only relatively small differences between four considered types of ventilated discs. However, substantial improvement in convective heat dissipation can be achieved by exposing the disc to the cross flow. A wheel carrier with holes is one such solution. In order to achieve the full benefits of improved convective cooling, the flow optimisation of the whole wheel assembly (disc-carrier-wheel) is necessary. The potentials are substantial and the modelled drag braking showed a relatively large reduction in disc temperatures for modest increases in the cross flow velocity.
Radiative heat dissipation is particularly difficult to improve. The analyses have shown the potential in improving radiative cooling by increasing the radiative heat transmission between the disc and vehicle components in its proximity.