Experimental Study on Cavitation in Mixed-Flow Pump Impellers

Abstract

Several mixed-flow pump impellers were tested in a test pump for the purpose of studying the effects of the number of vanes and the inlet edge shapes on their performance and cavitation characteristics. The impact-free-entry flow rates were obtained from the incipient cavitation conditions and inlet flow deviation angles were found, their degree varying with the number of vanes. There was very little effect of the inlet edge shapes on the normal performance, but they proved to be considerably influential on the cavitation characteristics. For the blunt inlet edge cavitation was observed on both sides of the edge simultaneously, while for the sharp inlet edge it occurred on one side. The values of cavitation parameter k_d for the impellers with the blunt inlet edge were about twice as large as those for the ones with the sharp inlet edge when compared at the beginning of the total head drop.