Analysis of the Flow Through a Vented Automotive Brake Rotor

Particle image velocimetry (PIV) was used to measure air velocities through a high solidity radial flow fan utilized as an automotive vented brake rotor. A brake rotor is a somewhat unusual fan in that its sole purpose is not to pump air but to dissipate thermal energy, it has no conventional inlet or outlet housing and it has a continuously varying rotational speed. For three typical rotational speeds, the flow characteristics were captured at the inlet and exit of the rotor, as well as internally through the cooling passages. Inlet measurements showed a swirling entry flow condition with significant misalignment of flow onto the vanes. As a result large regions of flow separation were found in the internal vane-to-vane passages on the suction side surfaces, which would lead to poor heat transfer conditions. The main flow exiting the rotor consisted of a series of jets corresponding to the individual rotor passages and were found to be very unstable leading to a rapid decay in velocity.