Effects of Entrained Air on the Performance of Centrifugal Pumps under Cavitating Conditions

Abstract

With use of radial flow pumps having different numbers of impeller blades, the performance of the pumps under air admitting conditions was examined in various capacities and cavitating conditions. In a pump with normal blade number, the flow pattern in the impeller was not altered by admission of small quantities of air, and the impeller worked normally in both cavitating and non-cavitating conditions. In this case, reduction of the pump performance is caused mainly by an additional hydraulic resistance due to the admitted air. In a pump with a too small blade number, the air admitted may bring about an increase of the pump head both in the non-cavitating and incipient cavitating conditions, which results from an improvement of flow pattern in the impeller due to the occurrence of cavitation.