Fluid Dynamics Characteristics during Stall Inception Process in a Centrifugal Fan

Based on the three-dimensional elliptic governing equations and the throttle model, an unsteady numerical simulation of rotating stall is undertaken in the case of G4-73 type centrifugal fan and the correctness of simulation results is verified by experiments. In this study a new rotating stall inception criterion is put forward, that the inlet flow or outlet back pressure fluctuations gradually increase in the value range. Numerical results show that the stall inception comes in obvious modal waveform, which belongs to the suction side stall caused by the incident angle changes due to the decrease of the flow. The relative velocity distribution of the impeller at different times indicates that the first bottleneck area occurs in the impeller channel near the volute tongue, while the other flow passages get improved and the flow field is unevenly distributed along the circumferential direction.