Multistage canned motor pump - getting deep insights with CFD - simulation, optimization and validation

This paper describes the detailed analysis of a multi-stage canned motor pump by means of CFD (computational fluid dynamics) simulations to find the main losses and show optimization potential of the hydraulic parts. In a first step, the numerical model was successively generated including all details like impellers, guide vanes (GV), return vanes (RV), gaps and pressure relief holes as well as the hydraulically coupled rotor of the drive. Simulations were carried out with the commercial CFD package ANSYS CFX 17.1 in stationary and transient way where mainly structured grids were used with a final model of the existing pump consisting of more than 35 mio. nodes. The behavior of the components was analyzed in detail and additionally the CFD-simulations were validated with model tests. Based on the loss analysis, a 2-stage optimization procedure was performed by combining manual engineering with automated optimization to establish the desired objectives and validated with the full numerical model. The simulations predict a huge efficiency increase from part load up to the best efficiency point (BEP) with respect to all given limitations (identical head curve, suction behavior and dimensions) and were then validated on the test rig where they have proven their high accuracy and reliability.