Numerical Procedure for Assessment of Centrifugal Pump Cavitation Erosion

Abstract

Currently the cavitation erosion damage becomes a critical issue that limits the centrifugal pump life cycle extension. Despite of a long history of studying the cavitation erosion phenomenon in centrifugal pumps there are still no reliable assessment methods except semi-empirical formula having rather limited application and accuracy. The paper is presenting a novel method for assessment of centrifugal pump cavitation erosion combining 3D unsteady flow CFD modeling and numerical analysis of cavitation bubbles behavior. The Navier-Stokes equations are solved by a splitting method with the implicit algorithm and high-order numerical scheme for convective transfer terms. The 3D numerical procedure is based on non-staggered Cartesian grid with adaptive local refinement and a sub-grid geometry resolution method for description of curvilinear complex boundaries like blade surfaces. Rotation is accounted with implementation of “sliding-grid” technology. The method considers evolution of the bubble in 3D flow from initial conditions until the disruption moment with determination of the erosion jet power impact. Validation of the method on model feed centrifugal pump stages is completed for two model centrifugal impellers Centrifugal impeller #1 is designed with a goal of through-passed shaft pump flow modeling. There are completed computations of cavitating bubbles’ evolution under non-uniform pressure field that show the non-uniform pressure distribution near the blade surface causes an essential influence on cavitation erosion. Computational prediction of the impeller #1 cavitation erosion damage is confirmed experimentally.