Reduction of Cavitation Damage in a High-Energy Water Injection Pump

Abstract

The conventionally-designed first-stage impeller of a high-energy, two-stage 19MW seawater injection pump, running at 4950 rpm and generating 1500m of head at a flow rate of 1.05 m3/s was seriously damaged by cavitation erosion in the first two months of operation. The impeller was redesigned by reshaping the blades in the region near the leading edges so as to reduce the inception cavitation number. This impeller has been running for more than a year, and the cavitation erosion rate is predicted to be low enough for it to last 40,000 hours. However, a prominent tone at blade passing frequency appeared with the new impeller, which interacts more effectively with the distorted inflow from the side-suction approach passage. Acoustic analysis of both single- and two-phase unsteady RANS CFD solutions corroborate the presence of this tone, which had not been observed when the pump operated with the original, conventional impeller.