Abstract
The most dominant secondary flow generated in an axial turbine cascade is the passage vortex. An enhancement of turbine blade loading by the increase of blade turning angle makes the passage vortex stronger. On the other hand, a flow acceleration by the convergent channel as in a reaction turbine cascade suppresses the development of passage vortex by reducing the boundary layer development on the passage walls. In the present study, flows in the curvature duct, which is considered to be a basic model for the generation of passage vortex, were analyzed numerically in order to examine the influences of the curved angle and the changing rate of channel width on the passage vortex and the associated loss generation. The computed results showed that the increase of curved angle promoted the development of passage vortex, and the increase of changing rate of channel width suppressed the developments of the passage vortex as well as the boundary layer by the reduction of the pressure difference between the inner and the outer walls.
