Mixing enhancement of ethylene secondary jet injected into supersonic cross-flow using curved pylon

Abstract

Mixing of ethylene secondary jet injected behind a curved pylon in supersonic cross-flow at a Mach number of 1.65 has been studied numerically with experimental validation. For the validation of numerical results, Schlieren, wall pressure measurements, particle image velocimetry, and planar laser-induced fluorescence experiments were performed. Ethylene fuel was used for the simulation, and air was used as a substitute fuel in the experiments. In this study, the curved pylon with different curvatures has been studied at 3.5 bar and 7 bar secondary injection pressures. The results are compared with the standard pylon and conventional transverse injection cases. The results showed improvements in mixing parameters when curved pylons were used. Results indicated that complete mixing was achieved in pylon cases at a much shorter distance than in the transverse injection. The complete mixing distance for the pylon cases was observed around z/dj = 50 and z/dj = 80 for 3.5 bar and 7 bar injection cases, respectively. Even though the mixing efficiencies were similar for all the pylon cases, the flammable plume area and total pressure loss differed. Changes in the bottom curvature angle at the trailing edge of the pylon caused different streamwise vortex structures, which affected the flammable plume area. A considerable difference was found in the penetration height among pylons at 3.5 bar injection pressure, and the difference became minimal at 7 bar injection pressure. Penetration height was greatly affected by the interaction of the secondary jet with the low-pressure region and the momentum flux ratio of the secondary jet. At least a 1 % reduction in total pressure loss was found for curved pylon cases when compared with the standard pylon.