Unsteady pressure distributions and forces on the impeller blades of a centrifugal pump

Fluctuations of pressure in the impeller caused by the interactions between a centrifugal impeller and a volute casing were examined experimentally. By using a Fourier analysis, the phase-lock averaged pressure was found to have its maximum amplitude of fluctuation on the pressure surface of the midpoint of the impeller passage and have different phase angles between the pressure and suction sides of a blade. The resultant force exerted on a blade at every circumferential position was calculated from the pressure distribution on the blade and was found to undergo a drastic change at off-design operating flow rate when the trailing edge of the blade passed by the volute tongue.