Optimum Strut-Configuration for Downstream Annular Diffusers With Variable Swirling Inlet Flow

Using three conical wall annular diffusers, geometries of struts mounted at the inlet tube were studied which were suitable for both the swirling inlet flow and the nonswirling inlet flow. Struts with an airfoil section which were installed at a small stagger angle served as a decelerating cascade for the swirling inlet flow, and a pressure rise was achieved across the struts. Furthermore, the residual weak swirl behind the struts improved the performance of downstream diffusers. For nonswirling inlet flow the struts induced a weak swirl which improved the performance of the diffuser. That is, if struts are designed properly, the performance of annular diffusers is improved by struts for a wide variation of swirl angle of inlet flow.