NACA-RM-L54G21

Abstract

Data obtained in a program to determine the performance improvements attainable through the use of boundary-layer controls in annular diffusers applicable to turbo jet afterburners are summarized for five diffusers tested with end without vortex-generator controls. The center-body length are emphasized. The diffusers varied in length from an abrupt dump to a length corresponding to an equivalent cone angle of 15⁰. All diffusers had a constant outer-body diameter of 21 inches, a ratio of outer-body diameter to center-body diameter at the inlet of 1.45, and an area ratio of 1.9 to 1.0. Inlet flow conditions corresponded to a maximum thickness of fully developed turbulent boundary layer, inlet Mach numbers up to 0.4, and both axial flow and 20.60 of whirling flow. <br>With axial or whirling inlet flow, reductions in diffuser length produced appreciable losses in performance, with or without vortex generators. Vortex generators improved the performance of all diffusers except the abrupt dumps. A diffuser with an outer-body length equivalent to that of the 15⁰ diffuser and a center body about half that length produced slightly less static-pressure rise and somewhat better velocity distributions than the 15⁰ diffuser, with or without vortex generators. With whirling inlet flow, it was necessary to use straighteners to remove most of the whirl in order to avoid large performance penalties.