Improving curved subsonic diffuser performance with vortex generators

The objective of this research was to use vortex generators to reduce total pressure distortion (i.e., total pressure nonuniformity) and improve total pressure recovery within a curved subsonic diffuser. In this study more than 20 configurations of both co- and counter-rotating arrays of vortex generators were tested in a diffusing S duct. Surface static pressure, surface flow visualization, and exit plane total pressure and transverse velocity data were acquired. The aerodynamic performance of each configuration was assessed by calculating total pressure recovery and spatial distortion elements. The best configuration tested reduced distortion by more than 50% while improving total pressure recovery by 0.5%. The results indicate that the mechanism responsible for improved aerodynamic performance is not boundary-layer re-energization from shed axial vortices but rather the suppression of detrimental secondary flows by redirecting the flow.