Performance Degradation of Centrifugal Pump under Single and Variable Speed Operation

Abstract

Centrifugal pumps are widely used in a variety of applications, accounting for approximately 20% of worldwide energy use. Although highly reliable machines, they are not immune to performance degradation over time, experiencing efficiency losses up to 25% by the end of service life. As the pump degrades, operation deviates from the best efficiency point as volumetric, hydraulic and mechanical efficiency decrease. A state-of-the-art experimental setup including a 7.5 kW centrifugal pump rated for a flow rate of 17 L/s and 23 m of head was used. To enable variable speed operation the motor is paired with a variable frequency drive. This thesis investigates and compares the effect of the wear-ring clearance on various operational (head, flow and power) parameters and performance (efficiency and specific speed) parameters under single speed and variable speed operation. The results from this work demonstrates the pump operational reliability under degraded conditions under different control methods.