Numerical analysis of transient flow in centrifugal pump at off-design conditions

In order to investigate internal flow characteristics and the rotor-stator interaction in the flow passage components of pump under off-design conditions, the paper selected a centrifugal pump as computational model whose specific speed is 129. Based on the SST k-w turbulence model, the transient numerical simulation of internal flow through the centrifugal impeller and volute was conducted by using ANSYS-CFX software. The distribution of inner velocity, streamlines, turbulence eddy dissipation and unsteady vortex in internal flow field of centrifugal pump were obtained. And the formation and dissipation of unsteady secondary vortex for the flow passage components of centrifugal pump, which has inlet pipeline and volute cross section, has been analysed in detail by means of regularization helicity at low flow rate. The results shown that under low flow rate condition, the prediction results of unsteady numerical simulation of pump performance are better than that of steady simulation. As the flow rate decreases, there always exists an unsteady flow near the impeller inlet. And the reverse flow, vortex and turbulence eddy dissipation were observed in the impeller passages. Meanwhile, the asymmetry characteristic of vortex exists obviously for the monitoring section of the flow field in the volute. And the amplitude of pressure fluctuation between impeller and volute becomes more obvious. It is important for improving the performance of centrifugal pump at off design condition to study the flow mechanism deeply and explore the effective methods for its prediction and control.