Secondary Flow Control in a Circular S-Duct Diffuser Using Vortex Generator Jets

Abstract

Performance enhancement of a circular S-duct diffuser by secondary flow control using vortex generator jets is the objective of the current experimental investigation. The experiments were performed in uniform inflow conditions at a Reynolds number of 7.8 x 10 and the performance evaluation of the diffusers was carried out in terms of static pressure recovery and quality (flow uniformity) of the exit flow. Detailed measurements including total pressure, velocity distribution, surface static pressure, skin friction and boundary layer measurements were taken and these results are presented here in terms of static pressure rise, distortion coefficient, total pressure loss coefficient and the transverse velocity vectors at the duct exit. The use of vortex generator jets resulted in around 20 percent decrease in total pressure loss and flow distortion coefficients in the diffuser. The mass flow rate of the air injected through the VGJ was about 0.1 percent of the mass flow rate of the main flow. The ability of vortex generator jets to reduce diffuser outflow non uniformity and total pressure loss by effective secondary flow control is demonstrated through the present study.