Abstract: Unsteady excitation induced by cavitating flow is one of the main factors causing the vibration and noise of the pump. In order to study the characteristics of unsteady excitation, the unsteady numerical simulation of the cavitating flow in the flow-passage of a centrifugal pumps is carried out by using the full cavitation model and the mixed two-phase flow model. Simulation results indicates that the cavitation bubbles generate at the suction side of blades near the leading edge, the region of bubbles extends with the reduction of inlet total pressure. When cavitation becomes serious, low-speed vortex is observed in the flow-passage. The frequency of the pressure fluctuations has the obvious discrete characteristics and the blade passing frequency dominates the pressure fluctuations. Along with the development of cavitation, cavitating flow can induce the increase of pressure fluctuation amplitude in the flow-passage, and there is a corresponding relationship between them. The cavitation can also induce the increase of unsteady radial force fluctuation amplitude and substantial increase of axial force. So cavitation affects operation stability and reliability of pumps.

Key words: centrifugal pump;cavitating flow;unsteady excitation;pressure pulsations;radial force