Measured and Predicted Secondary Flows in a Centrifugal Impeller

Abstract

The complete velocity distribution, including both primary and secondary velocities, has been measured in passages of centrifugal impellers of simple shape. Comparison is made with theoretically predicted secondary vorticities based on a simple combination of an inviscid primary flow and a streamwise vorticity generation analysis. The measured velocities were obtained in a water-flow impeller rig using a miniature, cylindrical, hot-film probe positioned on the rotating impeller and traversed and controlled remotely through slip rings. The understanding of the complex flow patterns was assisted by a photographic study employing a hydrogen bubble, flow visualization technique.