SOUND GENERATION BY A CENTRIFUGAL PUMP AT BLADE PASSING FREQUENCY

This paper reports the results of ail experimental study of the pressu re pulsations produced by a centrifugal volute pump at its blade passi ng frequency and their amplification by acoustic resonance in a connec ted piping system. Detailed measurements were made of the pressure flu ctuations in the piping as a function of pump speed and flow rate, A s emi-empirical model was used to separate acoustic standing waves from hydraulic pressure fluctuations. The effects of modifying the cut-wate r geometry were also studied, including the use of flow visualization to observe the flow behavior at the cut-water. the results suggest tha t the pump may act as an acoustic pressure or velocity source, dependi ng on the flow rate and the cut-water geometry. At conditions of acous tic resonance, the pump acted as an open termination of the piping, i. e., as a node in the acoustic pressure standing eaves. Rounding the cu t-water had the effect of reducing the amplitude of acoustic resonance , apparently because of the ability of the stagnation point to move an d thereby reduce the vorticity generated.