Vortex Design of a Diagonal Flow Impeller with High Specific Speed

Abstract

The "vortex design" method applied to an axial flow compressor stage has been extended to a diagonal flow impeller with high specific speed. For a given type of vortex flow, the through flow problem is solved by the streamline curvature method and a blade element is determined on the basis of this solution. However, for any vortex type except free vortex, an exit flow condition changes due to a secondary flow induced by vortices shed form the trailing edges. The given vortex type can be obtained by correcting this effect with a so-called secondary flow theory. The validity of this method has been examined in experiments on three kinds of vortex flows : free vortex type and constant tangential velocity types with or with or correction of the secondary flow effect.