10th European Conference on Turbomachinery Fluid dynamics & Thermodynamics
In the case of axial flow fan rotors used for electric motor cooling, an axial clearance is present between the rotor shroud inlet and the perforated cover. The effect of axial clearance size on the operation of a case study fan has been investigated. The means of investigation were Computational Fluid Dynamics (CFD) and Computational Aero-Acoustics (CAA). The CFD and CAA results revealed that the axial clearance size is a sensitive parameter in influencing both fan aerodynamics and aero-acoustics, for which the major mechanisms, associated with the leakage flow, were qualitatively identified. The studies suggested the existence of an acoustically unfavourable clearance size for which maximum noise emission can be expected. A semi-empirical model was outlined as a starting point in prediction of cooling flow rate as a function of axial clearance size as well as other parameters.