A Study on Diffuser Stall in a Three-Stage Centrifugal Pump

Abstract

In this study, the effect of rotor axial offset and the balance flow rate on the diffuser rotating stall in a three stage centrifugal pump was experimentally investigated. In our previous research, when the impeller-diffuser gap was widened, the positive slope of head performance curve was observed at low flow rates than 15% of design flow rate. In the flow rate range with the positive slope, the distinct pressure fluctuation with low frequency (approximately 13 % of impeller rotation), measured at the inlet throat of diffuser vane, was observed, which was found to be caused by the diffuser rotating stall with 1 cell. The feature of rotating stall was affected by the rotor axial offset. Especially with the offset to the suction side, the amplitude of pressure fluctuation in the 1^st and 2^nd stage diffusers was weakened.