Numerical Analysis of Performance Deterioration of a Centrifugal Pump Operating in Two-Phase Flows

Pumps handling two-phase flows are essential parts of industrial process mainly in oil and gas facilities and power plants. It is known that for centrifugal pumps the presence of gas phase in liquid flow causes the performance to deteriorate. Knowledge improvement of the highly complex internal flow is the way to design more efficient and reliable pumps. The paper describes the results of studies conducted in a centrifugal pump operating in two-phase air/water mixture flows, for performance determination and flow field investigation using numerical simulations. The aim is to provide a new highlight on the performance evolution and to identify the physical mechanism responsible for the deterioration. The work is carried out at design flow rate with varying inlet gas volume fraction. The results show significant performance deterioration compared to single-phase situation. The analysis of flow fields in case of two-phase flows reveals an accumulation of the gas in the impeller passages, causing an alteration of the conventional single-phase flow structure. The effect of interaction with volute is also investigated and it is found to play a key role in changing the flow pattern inside the impeller. At the conclusion of the study, special design features are suggested as concepts for enhancing two-phase pumping behavior of centrifugal pumps.