Impact of impeller material on acoustic emission in a centrifugal pump

Abstract

This study investigates the effect of impeller material on the acoustic emissions from a centrifugal pump under various operating conditions, including normal operation, the onset of cavitation, and fully developed cavitation. Five different impeller materials—plastic, cast iron, brass, stainless steel, and aluminum—were experimentally tested. Cavitation was determined at the separation point on H-Q curve when the head dropped by 3% and by analyzing the acoustic spectrum. The experimental setup included a centrifugal pump equipped with pressure transducers and a turbine flow meter to measure the suction pressure, outlet pressure, and water volume flow rate. Acoustic measurements were taken using a microphone with bandwidth of 20–20,000 Hz, recorded via a data acquisition system using LabVIEW software. The obtained results indicate that the plastic impeller generates the lowest noise levels under both normal and cavitating conditions, likely due to its lower sound propagation speed. Cavitation-induced noise was quantified with peak frequencies around 3700 Hz for all tested materials. The sound amplitude varies significantly with the impeller material. Under normal conditions (suction pressure of 0.82 bar-absolute), the inlet blade angle deviation from the design value had a negligible effect on the acoustic emissions across all materials. This study presents a novel approach that provides quantitative insights into the acoustic behavior of impeller material, suggesting that a plastic impeller can significantly reduce pump noise and enhance performance in noise-sensitive applications. By using the plastic impeller, the percentage reductions in both minimum and maximum sound levels with respect to standard stainless-steel impeller of the examined pump are 1.5% and 4.43%, respectively, at the suction pressure of 0.82 bar absolute.