Numerical Investigation on Impeller-Volute Interaction in the Centrifugal Pump With Radial Gap and Tongue Profile Variation

Numerical simulations on impeller-volute interactions in a low specific speed centrifugal pump equipped with three different outlet diameter impellers and variable tongue profiles were carried out using a commercial code CFX-10. The numerical results indicated that the maximum efficiency point is shifted along the lower flow rate direction with the increasing of impeller-volute radial gap. There is no linear relation between the radial gap variation and the pressure amplitude and it is possible to get an optimum value of the radial gap, which can improve notably the pressure pulsating characteristic while the head dropping of the pump is very small. The effects of three different tongue profiles on the flow field indicated that the influence of the different tongue profiles on the performance and operation stability of the centrifugal pump is very remarkable. The high-efficiency range of the centrifugal pump can be widened to some extent while the profile of the tongue is replaced from sharp tongue to middle tongue, and the maximum efficiency point is shifted along the higher flow rate direction. The operation stability of the centrifugal pump may be influenced while the fluid flows in the diffuser of the centrifugal pump with short tongue. The amplitude of pressure fluctuation in the tongue zone drops notably while the pump equipping with the middle tongue or the short one is in running.