Investigation of an axial turbine stage with tangentially curved guide vanes - Part 1: Flow structure in the blade channel

By tangential curvature of the stacking line of the blade profiles guide vanes can be designed, which have on both ends an obtuse angle between suction side and sidewall. This configuration, according to literature, is capable of reducing the secondary loss. This type of vanes, because of the resulting radial components of the blade force, effects a radial displacement of the meridional stream-lines, a modification of the pressure distributions on the profiles and different flow outlet angles. Three-dimensional numerical simulations with the Navier-Stokes-solver NUMECA have been made for a single stage axial turbine with different types of tangentially curved guide vanes. The effects of the blade curvature on the flow field and the blade forces have been investigated systematically and in detail.