Tip Clearance and Tip Vortex Cavitation in an Axial Flow Pump

Abstract

A combined study of tip clearance and tip vortex cavitations in a pump-type rotating machine is presented. Cavitation patterns are observed and cavitation inception is determined for various gap heights, clearance and blade geometries, and rotor operating conditions. An optimum clearance geometry is seen to eliminate clearance cavitation when the clearance edge is rounded on the blade pressure side. The gap height has a strong effect on clearance cavitation inception, but the trends vary considerably when other parameters are also modified. The gap height and clearance geometry have less influence on tip vortex cavitation but forward and backward blade skew is observed to reduce and increase tip vortex cavitation, respectively, as compared to a blade with no skew.