Aerodynamic noise characteristics during evolution of rotating stall in centrifugal fan

Based on the throttle valve function and broadband noise model, the aerodynamic noise characteristics of G4-73 backward centrifugal fan under rotating stall was numerically studied. The noise characteristics of centrifugal fan under four different conditions were analyzed, namely designed condition, the occurrence of stall inception, the development of stall inception and the circumferential propagation of stall cells were analyzed. And the influence of rotating stall on the distribution of aerodynamic noise was revealed. The results show that after the occurrence of stall inception, the high noise areas corresponding to vortex noise near the impeller develop along the radial, circumferential and axial directions, and the number of high noise area turn into 1 from 2. During stall, vortex noise accounts for the major part of fan noise, and the high noise areas propagate circumferentially with the same speed of stall cells. Also, the influence mechanism of stall cells and volute on the aerodynamic noise of centrifugal fan is addressed. The research results have great importance to completing the theory system of rotating stall and predicting the occurrence of stall through monitoring noise.