Numerical study on jet-wake flow and its evolution in a centrifugal pump with alternating stall

Abstract

Stall and jet-wake flow are two typical forms of unstable flow phenomena in centrifugal pumps, significantly affecting their stability. This paper investigates the interaction mechanisms between stall and jet-wake flow in a centrifugal impeller under different working conditions. The unsteady numerical study utilizes the partially averaged Navier–Stokes (PANS) model with a new dynamic fk expression derived from the rotation-corrected energy spectrum. The results reveal four stages in the flow field evolution of the centrifugal pump under different working conditions. In stage I, no stall vortices are present, and the jet-wake flow occurs. The velocity distribution at the impeller outlet depends on the pressure difference distribution between the pressure and suction sides within the flow passage. As the flow rate decreases, the pressure difference between the two sides increases, intensifying the jet-wake phenomenon. Under part-load conditions (stages II, III, and IV), the presence of stall vortices becomes the main factor affecting the jet-wake flow. These stall vortices influence the local and downstream flow fields, thus altering the distribution of the jet-wake. When the stall vortex is on the pressure side, it reduces the velocity near the pressure side, weakening the intensity of the jet-wake. On the other hand, when the stall vortex is on the suction side, it reduces the velocity near the suction side, enhancing the intensity of the jet-wake.