Effects of inlet flow velocity on the cavitation inception of centrifugal pumps.

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