On the Relevance of Inviscid Subsonic Flow Calculations to Real Centrifugal Impellers Flow

Abstract

The results of a fully three-dimensional inviscid compressible calculation technique for the flow field inside centrifugal impellers are compared to optical measurements in an open, radial exit impeller. It is concluded from this comparison that as long as viscous influence, including its displacement effects (manifested mainly in the jetwake flow structure), are not too big, the inviscid method applied can be used with confidence. When the viscous influence is such that it distorts the flow field in certain regions but displacement effects are still insignificant, the inviscid method can be used outside regions of viscous dominance. This situation occurs about halfway downstream, through the impeller. Only when displacement effects resulting from viscous flow field distortions, become big and the jet-wake profile becomes fully developed, does the inviscid method fail to predict the correct flow field. This happens at the exit of the impeller investigated here.