Performance of centrifugal pump over a range of composite wear ring clearance

Abstract

Modern centrifugal pumps are installed with composite wear rings that run under tight clearances to meet the size, weight, and performance demands. Internal leakage flow past the wear ring clearance can significantly degrade the pump's performance and limit its predictability and reliability. In this study, a model-based approach is presented to elucidate the effect of wear ring clearance on the pump's performance for increasing wear ring clearance ranging over two orders of magnitude (0.01–2 mm) and at different levels of eccentricity. It is observed that the leakage flow rate exhibits a nonlinear trend with increasing wear ring clearance, which is characterized by two threshold values. The first threshold clearance beyond which the leakage flow rate increases rapidly, leading to a drop in the pump's pressure head, and the second threshold, beyond which the leakage flow rate becomes constant. The increase in eccentricity ratio amplifies this trend of leakage flowrate and pump head. For a double-suction pump, the effect of different combinations of both the side wear ring clearances is investigated. The result shows that for a fixed value of clearance on one side, the leakage flowrate through that side decreases if the clearance on the other side decreases. Overall, the model-based understanding presented in this study will help to predict the pump's performance over a range of wear ring clearances and hence the severity of internal leakage, as encountered in present-day pumps that are installed with composite wear rings. © 2022, The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering.