Effects of clearance flow on the characteristics of centrifugal pump under low flow rate

The Reynolds averaged Navier-Stokes equations and the shear stress transport k-w turbulence model are employed to simulate the centrifugal pump with or without clearance flows. The simulation results have been compared with the experimental data and good agreement has been achieved. Results show that clearance flow causes a decrease in the characteristics of the centrifugal pump, particularly in pressure fluctuation. The largest deviation of the amplitude of pressure fluctuation between the centrifugal pump with and without clearance flow is 65.34 %. The numerical results also show that the clearance flow causes collision impact with the mainstream flow and forms a multiple vortex structure at the impeller entrance. Clearance flow greatly affects the pressure distribution in the impeller passage, which is opposite to the volute tongue, especially at the suction side of the blade surface. The wave distribution decreases along the direction of the hub to the shroud, which indicating that the influence of clearance flow weakens along this direction.