Unsteadiness of Pressure Distribution and Cavitation Inception on the Impeller Blades of a Centrifugal Pump

Abstract

Pressure distribution and cavitation inception near the inlet region of an impeller passage of a centrifugal pump were examined experimentally. Both at flow rates lower and higher than normal, the pressures on the blade surface of the impeller fluctuated nearly periodically with its circumferential position due to the non-uniform pressure distribution of the volute and the presence of the dividing ridge of the volute. From the measured pressure distributions on the blade surface at a fixed circumferential position, the pressure fluctuations were also found to be caused, especially at low flow rates, by turbulent fluctuations including the separation of flow from the blade surfaces. The quasi-periodic changes in the pressure distribution caused circumferential non-uniformity of the cavitation occurrence near the cavitation inception and effects of the pressure fluctuations on desinentcavitation number were found to be noticeable at a low flow rate.