Study on Internal Flow and External Performance of a Semi-open Impeller Centrifugal Pump with Different Tip Clearances

To study the influence of tip clearance on internal flow characteristics and external performance of a prototype centrifugal pump with a semi-open impeller, the unsteady numerical simulation and performance experiments are carried out in this paper. The evolution process of leakage vortex with time t, the flow characteristics and the magnitude of leakage rate in tip clearance are obtained in details. The results indicate that the H-Q curve hump of centrifugal pump shows a weakened trend with the increasing of tip clearance Delta c. Meanwhile, the leakage rate Delta Q and the ratio of leakage rate to discharge flow rate (Psi) gradually increase. At the same tip clearance, the leakage rate Delta Q increases, while the ratio of leakage rate to discharge flow rate (Psi) decreases with the increasing of discharge flow rate Q. It is found that higher volumetric loss account for a higher percentage of the total loss at small flow rate condition. There easily exist strong leakage vortexes in the impeller inlet, impeller passage and impeller outlet. The pressure difference between suction side and pressure side makes the fluid pass through the tip clearance layer to form a lower pressure region and leakage vortex.