A Study of the Flow of Water and Bubbles through Centrifugal Pump Impellers

Abstract

A method to measure the velocity distribution in a centrifugal pump impeller is developed by using two types of stream line photographs ; one is the photograph of the stream line relative to the impeller vanes, and the other is that of the absolute stream line. With the same method, the flow velocities of the bubbles of cavitation which appear in the flow through the impeller are also measured. The results of those measurements have shown that the velocities of bubbles are much larger than those of the water at the same discharge. Thus the cavitating flow of water is assumed to be a kind of compressible fluid mixed with vapour bubbles. By solving the equation of motion of this assumed compressible fluid, the velocity distributions of the bubble flows which are measured in this experiment, and at the same time, the mechanism of cavitation shocks, are explained.