Aerodynamic Noise of a Propeller Fan at Maximum Efficiency Point and Off-Design Point

Abstract

In order to clarify the relation between the aerodynamic noise and the flow regime around the impeller of a propeller fan operated in maximum efficiency point and off-design point, the characteristics of the fan with the impeller of the different solidity were analyzed experimentally. In the case of high solidity fan, the narrowband noise due to the wake vortex was generated at the off-design point since the relative velocity in the wake became high. From results of the analysis, it was indicated that the broadband noise of the low solidity fan at the maximum efficiency point is related for the velocity fluctuation not only due to the wake vortex but the unstable tip vortex.