The Supercavitating Pump

Abstract

Cavitation in conventional pumps can cause loss of efficiency and erosion damage. For these reasons speeds and suction pressure are limited to avoid these effects. There are, however, applications where, for technical or economic reasons, these limitations are not acceptable. For these, the supercavitating pump has been developed. Basically it comprises an axial-type impeller with cavities forming over the suction side of the blade and collapsing downstream where they cause no damage. For duties requiring higher pressures, it can be staged in front of a conventional centrifugal pump. The complete development of the supercavitating pump, the theoretical optimization of the geometric parameters to get good or best performance and the theoretical design method based on potential flow cascade data are described. Experimental results are given for a series of impellers of different size, speed, stagger angle and blade shape. Comparison of the experimental results with the design method gives good agreement on the whole. Data are also given on the effects of secondary losses, tip clearance losses, blade thickness and blade rake. Some of the applications and uses of such pumps in the process industry, as boiler feed and aircraft fuel pumps and for water jet propulsion, are discussed.