Sound Generation by a Centrifugal Pump at Blade Passing Frequency

This paper reports the results of an experimental study of the pressure pulsations produced by a centrifugal volute pump at its blade passing frequency and their amplification by acoustic resonance in a connected piping system. Detailed measurements were made of the pressure fluctuations in the piping as a function of pump speed and flow rate. A semi-empirical model was used to separate acoustic standing waves from hydraulic pressure fluctuations. The effects of modifying the cut-water geometry were also studied, including the use of flow visualization to observe the flow behavior at the cut-water. The results suggest that the pump may act as an acoustic pressure or velocity source, depending on the flow rate and the cut-water geometry. At conditions of acoustic resonance, the pump acted as an open termination of the piping, i.e., as a node in the acoustic pressure standing waves. Rounding the cut-water had the effect of reducing the amplitude of acoustic resonance, apparently because of the ability of the stagnation point to move and thereby reduce the vorticity generated.