Aerodynamic and aero-acoustic improvement of electric motor cooling equipment:

A radial flow rotor with radially aligned straight blades, used in electric motor cooling, has been considered as datum fan. The aerodynamic performance and acoustic behaviour of the datum fan have been measured, in order to establish a basis for redesign. As replacement for the datum fan, an axial flow shrouded rotor with skewed blades has iteratively been designed, involving computational fluid dynamics and computational aero-acoustics tools. The aim of redesign was reducing fan noise and moderating motor shaft power absorbed by the fan, while retaining the original cooling performance. Special flow features have been taken into consideration in three-dimensional axial rotor design, such as leakage flow in the axial clearance between the rotor shroud inlet and the perforated cover, and strong radial flow as well as deviation due to the motor shield located close downstream. The axial rotor has been manufactured via rapid prototyping. Measurements on the prototype confirmed the achievement of the redesig...