Performance characterization of a highly offset diffuser with vortex generator jets

Abstract

The effect of blowing vortex generator jets on the performance of a highly offset (S-duct) diffuser was investigated experimentally (Mi = 0.6, Re^ = 3.46 X 1C). Inlet plane total pressure and Mach number contours were mapped using a pitot probe. Exit plane total pressure recovery, static pressure recovery, and Mach number contours were mapped with blowing on and off, using pitot and static probes. Crosswire anemometry was used to measure the mean velocity and turbulence intensity in three dimensions at three spanwise locations on the exit plane with the blowing on and off. Without blowing, the flow on the lower surface of the diffuser was massively separated. Blowing at 0.50% mass flow ratio through three lower-surface vortex generator jets reduced the size of the separated-flow region and the exit plane boundary-layer thickness, increased pressure recovery, and decreased turbulence intensity. Blowing redistributed momentum within the diffuser and altered the secondary flow structure. However, the exit plane total and static pressure fields were more distorted with blowing than without.