Instability analysis under part-load conditions in centrifugal pump

Abstract

In this study, a centrifugal pump with a specific speed of 39.12 m×min-1×m3s-1 is treated to analyze the flow instability under part-load conditions by numerical simulation and experimental test. For calculations, the RANS method, coupled with the k-ω SST turbulence model, is adopted. Numerical results at different operation points are compared with available experimental data, such as hydraulic performance and flow field information by particle image velocimetry. The numerical and experiment results agree well. The flow simulation indicates a strong reverse flow at the passage upstream impeller inlet, and the energy loss in the impeller is the largest under part-load conditions among all flow components in the pump. In one impeller revolution, one blade-to-blade flow passage is always nearly blocked off by the rotating stall occurring at the impeller inlet for each instant, and the blockage induces a jet flow with large velocity at the next blade-to-blade flow passage along the rotational direction of the impeller. The blockage and the jet flow in the blade-to-blade flow passages will make the flow unstable inside the impeller and cause performance breakdown and pressure vibration under part-load conditions for the pump.