Research of the vibration induced by cavitation in a centrifugal pump under part load condition

Abstract

Cavitation and the corresponding induced vibration characteristics in a centrifugal pump under part load (0.4Qd, Qd is rated flow) conditions were investigated by combining numerical simulation and experimental analysis to determine the internal flow characteristics and vibration signals under different cavitation conditions. Under part load conditions, cavitation is initiated at the inlet of blades close to the tongue. Expansion of a low-pressure region increases the size of vortex in the flow passages, which increases the severity of the flow instability in the pump during severe cavitation. As cavitation develops, the random generation and rapid collapse of cavitation bubbles produce unstable vibration of the pump system. The high-frequency and broadband pulsation of vibrations distributed in the frequency band of 4–10 kHz can be regarded as typical signals induced by cavitation in the pump at 0.4Qd. The net positive suction head available of the cavitation incipient point is determined to be 9 m at 0.4Qd. The rotor–stator interaction between the impeller and volute affects the vibration signals at individual measurement points, which exhibit clear shaft-frequency characteristics in the frequency band of 0–600 Hz.