Relationship Between Unsteady Flow, Pressure Fluctuations, and Noise in a Centrifugal Pump—Part A: Use of PDV Data to Compute the Pressure Field

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Abstract
Velocity distributions determined by using Particle Displacement Velocimetry are used for computing the pressure field within the volute of a centrifugal pump. It is shown that blade-tongue interactions and nonuniform outflux from the impeller are primary contributors to local pressure fluctuations and far field noise. Consequently, a slight increase in the space between the impeller and the tongue causes significant changes in flow structure and reductions in the resulting noise. The impact is significant as long as the tongue-impeller gap is less than 20 percent of the impeller radius. It is also shown that the vorticity distributions, particularly the large vortex trains associated with the jet/wake phenomenon, dominate variations in the total pressure. Thus, it is unlikely that a potential flow model can provide any realistic description of the flow structure.