Effect of Radial Gaps between Impeller and Diffuser Vanes on Pressure Fluctuations Downstream of a Diffuser Pump Impeller

Instantaneous pressures were measured on the casing wall of a guide vane passage and volute casing of a diffuser pump with three different radial gaps between the impeller exit and guide vane inlet. The measured pressure fluctuations were found to decrease with increasing radial gap. Using our method, numerical calculations were performed for the pressure fluctuations, and the calculated pressure fluctuations were found to agree with measured ones. Moreover, the ensemble-averaged pressure data show the effects of the radial gaps on the spatial distribution of unsteady pressures, which causes the rotation of the circumferential pressure mode due to rotor-stator interaction.