Stationary stall phenomenon and pressure fluctuation in a centrifugal pump at partial load condition

Abstract

Stall is a common flow phenomenon in the rotating machinery under partial load conditions. The stall phenomenon can seriously affect the operation efficiency and stability of the machinery. In the present research, the stall phenomenon in a centrifugal pump is numerically studied using the SST k-ω turbulence model. In the present work, four different flow rates (1.0 Qd, 0.7 Qd, 0.5 Qd and 0.3 Qd, where Qd is the design flow rate) are investigated, and results reveal that with the decreasing of flow rate, the stall can be divided into the preliminary stall and stationary stall according to the flow structure. When the flow rate decreases to 0.5, the vortexes become strong, but not occupy the whole passage, which is defined as the preliminary stall. When the flow rate further decreases to 0.3 Qd, a fully developed stationary stall appears. Under this condition, the periodic process of stationary stall can be classified into four stages: incepting stage, developing stage, shedding stage and decaying stage. The dominant frequencies of pressure fluctuations under stationary stall conditions are fi, and the maximum amplitudes of pressure fluctuations of PS4 and PS5 at 0.3 Qd are about 5 times that at 1.0 Qd due to the trailing edge vortexes at the blade outlet.