Author(s)

A. Nemdili

Abstract

Small centrifugal pumps are largely used for automobile cooling systems. This study presents investigated NPSH-curves of a small centrifugal pump working with a semi-open and a closed impeller. The influence of the impeller blade number, the front clearance and the cover, and the influence of the impeller width on the cavitation are investigated. It was found that: - with decreased blade number, the NPSH-curves have higher values, due to the change of the pressure distribution along the blades. - The cover of the impeller has an unfavorable effect on the cavitation sensitivity. This last increases with increased values of the clearance, due to the variable clearance flows for covered and uncovered impellers. - Narrowed impellers are characterized with higher NPSH-curves, due to the fact that for the smaller flow cross-sections the speed at the inlet of the narrowed impellers is higher than for wider impellers, when the risk of cavitation increases. Keywords: centrifugal pump, semi-open impeller, closed impeller, blade number, front clearance, impeller width, cavitation, NPSH curve. 1 Introduction Small radial pumps over the last few years have become simpler and produced with favorable costs. They are largely used for automobile cooling systems. Small centrifugal pumps with semi-open impellers (i.e. without cover plate or with half shrouding), because of the low exactness production, are operated with greatly different front clearances between 0.2 and 1 mm. These impeller types

Keywords

centrifugal pump, semi-open impeller, closed impeller, blade number, front clearance, impeller width, cavitation, NPSH curve.