Characteristics of Transient Flow and Pressure Fluctuation in Impeller for Centrifugal Pump

Transient flow analyses in centrifugal pump are focused mainly on the volute, while little attention is paid on the rotating impeller. The transient flows for different operating conditions in centrifugal pump are numerically investigated using RNG k-e turbulence model and moving mesh. The computational results of pump head and efficiency show good agreement with the experimental data. Three monitor points are positioned on the blade pressure and suction surfaces. The pressure fluctuations on monitor points are analyzed and discussed. For design flow rate, the dominant frequencies on blade surface are 1 or 2 times rotating frequency. The dominant frequency equals the rotating frequency for both small and large flow rates. The amplitudes of pressure fluctuation increase gradually from the impeller inlet to outlet. The maximum amplitude of pressure fluctuation for small rate is about 5 times than that for design flow rate at the same monitor point. The relative velocity distributions in impeller are analyzed for small flow rate. The results show that the vortexes evolving with time at the impeller outlet near the pressure surface give rise to the flow non-uniformity, inducing low operating efficiency and large pressure fluctuation for centrifugal pump.