On the performance of a centrifugal pump under bubble inflow: Effect of gas-liquid distribution in the impeller

Abstract

Abstract: Determining the characteristics of gas-liquid two-phase flow in centrifugal pumps is essential for a better understanding of pump performance. In this study, a visualization investigation was performed to determine the effect of the gas-liquid distribution in the impeller on the performance of a centrifugal pump with a closed impeller. Emphasis was placed on the influences of the inlet gas volume fraction (IGVF), flow rate, and rotational speed on the gas-liquid distribution in the impeller and, thus, on the surging characteristics of the pump. The correlation mechanism between the distribution of the gas-liquid phase in the impeller and the surging characteristics of the pump was revealed. Finally, several surging prediction models were examined. The results show that the gas-liquid two-phase distribution in the impeller has an immediate impact on the pressure increment and efficiency of the pump. The increase in IGVF directly induced pump surging by changing the flow pattern in the impeller. Surging occurred when the flow pattern changed from gas pocket flow to segregated flow. It was also found that pump surging could be eliminated by adjusting the flow rate and increasing the rotational speed, which changed the flow pattern inside the impeller. Compared with the experimental results, the critical IGVF obtained by the existing surging prediction model exhibits some deviation. The surging prediction model dedicated to the volute centrifugal pump requires further investigation. The results reported here can provide better insight into the performance of volute-type centrifugal pumps and provide a reference for developing corresponding surging prediction models.