Effects of Inlet Flow Pattern on Cavitation Inception of Centrifugal Pumps

Abstract

Flow patterns near the inlet portion of an impeller and cavitation inception were examined experimentally using a centrifugal pump with 3, 7 and 9 blade impellers. At low flow rates, velocities at the inlet of seven and nine blade impellers have non-uniform distributions inbetween hub and shroud, which cause a large drop of pressure on the suction surface of the blades near the shroud. In the impeller with three blades, a large vortex was created near the suction side of its inlet and this prevents severe drop in the pressure as seen in the seven blade impeller. Three kinds of cavitation were observed in the impeller passages according to the pressure distribution on the blade surface.