Design of Pump Impellers for Optimum Cavitation Performance

Abstract

Although there is much empirical information on the cavitation performance of centrifugal and other types of pumps, there is very little theoretical basis for their design. Certainly these empirical data have been used to suggest certain fundamental requirements that produce pumps of good performance, but there is no scientific way of assessing the influence of such variables as blade incidence, blade number or shape of blade or passageway. A theory is presented for optimizing the geometric parameters to give the best cavitation performance or alternatively to assess the influences of working away from the design. From this, a theoretical method based on cascade data transformed into the radial plane is used for detail design for given cavitation inception conditions. Following on this, a new method has been developed for predicting cavitation performance breakdown, based on linearized potential flow theory. Comparisons are made between these theoretical predictions and experimental data obtained both at NEL and those quoted in the literature. Agreement is on the whole very good.