Elimination Of Cavitation-Related Instabilities And Damage In High-Energy Pump Impellers

Abstract

The suction-stage impeller of a large crude oil pipeline pump was designed by combining quasi-three dimensional flow analysis with current theories to generate an impeller geometry, which was evaluated in a half-size model test pump. The model impeller was compared to a reference impeller designed in accordance with principles derived from correlations of field data to resist cavitation erosion for 40,000 hours. Flow visualization testing showed the model impeller to be free bubbles and other cavities from 80 percent to 120 percent of rated flow and to have substantially less two-phase flow activity that the reference impeller over the required flow rate range from 50 percent to 135 percent. Measurements of pressure pulsations, cavitation noise level and soft coating removal, in addition to the visual observations, demonstrated that the model impeller design has not only greater erosion resistance than the reference impeller, but that the design also produces significantly less mechanical response of the pump and surrounding structures to cavity oscillations in the flow passages.