Experimental Comparison of Hydrodynamic Behavior Under Partial Flowrates and Cavitation in Three Configurations of a Centrifugal Pump With Inducer and Impeller

Abstract

This study aims at experimentally investigating the hydrodynamic behavior of a centrifugal pump, both with and without cavitation. The pump consists of an axial inducer, a centrifugal impeller, and a volute. Three assembly configurations are examined: the inducer alone, the impeller alone, and the combined inducer and impeller. Particular attention is given to cavitating conditions—low suction pressure—at four partial flowrates (4% ϕref, 16% ϕref, 39% ϕref, and 78% ϕref), where ϕref is defined as the flow coefficient for which the inducer has been designed. The hydromechanical performance is analyzed and compared across these configurations, with cavitation formation captured using high-speed digital imaging. A spectral analysis of pressure signals is also conducted in operational regimes where instabilities were observed. The results indicate that the inducer mitigates the impact of cavitation on hydromechanical performance as the flowrate approaches the design point ϕref. However, at partial flowrates, the inducer negatively impacts pump performance by increasing the critical cavitation number threshold beyond which a head drop occurs. Cavitation-induced instabilities were observed in partial flow regimes and under low suction pressure conditions in configurations involving the inducer. These instabilities, characterized by a very low-frequency signature, result in significant pressure and flow fluctuations, leading to vibrations within the system. Furthermore, these instabilities exhibit a clear dependency on flowrate.