Rotational Noise Reduction for Axial Flow Fans : 1st Report

Abstract

Noise emitted from an axial fan is classiffied into two types of noise, that is, rotational and turbulent noise. The former is due to the radiator fan, which is one of the major components of noise generated in an engine compartment, and consists of many efforts have been made to reduce it. In this paper the mechanism of the rotational noise of an axial fan having blades of unequal pitch angles is studied experimentally. By adjusting the attack angle of each blade with the blade pitch and accelerating the flow in narrower passages, the rotational noise was found to be decreased.