Investigation of the Impact of Wear-Ring Clearance on Hydraulic Performance and Axial Thrust in Multistage Low-Specific-Speed Centrifugal Pumps

Abstract To address the need for larger wear-ring clearances and the sensitivity of axial forces in novel magnetic levitation pump units, this study investigates the effects and underlying mechanisms of increasing wear-ring clearances on the hydraulic performance and axial thrust of the single-stage impeller-diffuser structure through experimentally validated numerical simulations. The results show that the front wear-ring clearance has a significant impact on the pump's head and efficiency, while the rear wear-ring clearance has only a minimal effect on hydraulic performance. However, both front and rear wear-ring clearances significantly influence the axial force on the impeller. Specifically, as the wear-ring clearance increases from 0.1 mm to 0.6 mm, the axial force increases by 203%. Moreover, as the front and rear wear-ring clearances are increased simultaneously, the axial force increases at a rate of up to 12.5 kN/mm per unit clearance increase. Through a comparative analysis of the velocity and pressure field distributions within the cover plate chamber at different wear-ring clearances, this study elucidates the mechanisms of by which increased wear-ring leakage flow impacts the axial force on the impeller. The findings of this work extend current understanding, which has typically attributed the influence of leakage flow on axial force solely to its effect on the tangential velocity in the chamber cavity. These results provide both theoretical insights and practical guidance for the optimized design of magnetic levitation pump systems and axial load prediction of multistage, low-specific-speed centrifugal pumps. This research also has significant implications for advancing the application of magnetic levitation technology in high-speed rotating machinery.