Prediction of Outlet Flow Characteristics of Centrifugal Impellers : 1st Report, Consideration of Velocity Distortion

Abstract

The analytical method for predicting the flow characteristics at the outlet of centrifugal impellers is presented taking into account the influence of velocity distortion in both the peripheral and the hub-to-shroud directions and its effectiveness was confirmed with the flow measurements around pump impellers. The results show that the increase of wall friction due to a mixing of flow just after the impeller exit should be adequately considered for successful prediction, and the influence of velocity distortion in the hub-to-shroud direction should also be considered for the case of the parallel-walled diffuser width being larger than the impeller exit width, while it is negligible in the case of the diffuser width being equal to the latter. It is pointed out that the peripheral velocity component of the outlet flow used for the determination of slip factor and the theoretical head should be defined by the mass-averaged value of the section.