Experimental Acoustic Analysis of Cavitation in a Centrifugal Pump

Abstract

Cavitation is an unavoidable phenomenon in the operation of centrifugal pumps. Prolonged cavitation can cause significant damage to the components of the flow channel, and in severe cases, it may even interfere with the normal energy exchange processes within the pump. Therefore, effective monitoring of cavitation in centrifugal pumps is crucial. This article presents a study that approaches the issue from an acoustic perspective, using experimental methods to gather and analyze acoustic data at the inlet and outlet of centrifugal pumps across var-ious flow rates, with hydrophones as the primary measuring instruments. Results show that flow rate significantly affects noise levels in both non-cavitation and mild cavitation stages, with noise increasing as the flow rate rises. As the cavitation margin (NPSHa) decreases, inlet and outlet noise trends diverge: inlet noise drops sharply, while outlet noise initially increases before sharply decreasing. Both exhibit a distinct zone of abrupt change, where NPSHa values offer earlier cavitation detection than traditional methods. The noise at the pump's inlet and outlet primarily consists of discrete and broadband noise, with most energy concentrated at discrete frequencies—shaft frequency (24 Hz), blade frequency (144 Hz), and their harmonics. As NPSHa decreases, the inlet's discrete and broadband noise frequencies decline, while they increase at the outlet. Monitoring changes in these spectrum characteristics provides an additional means of predicting cavitation onset.