Effect of clearance of impeller wear-rings on efficiency of low specific speed centrifugal pump

The experiments on different types of impeller are done by changing the clearance of wear-ring to prove that the clearance has no influence on the pump efficiency under various types of impeller.An algorithm for calculating the disc friction loss is developed in terms of energy conservation with consideration of the leakage rate.Based on this algorithm,a formula on the efficiency of a low specific speed centrifugal pump is deduced on the premise that the leakage rate is taken as the independent variable.Combined with formulas of hydraulic efficiency and volume efficiency,the conclusion is drawn that the pump efficiency decreases with the increasing clearances of wear-rings even though the mechanical losses decrease with the increasing of leakage rate.