Sonic injection from diamond-shaped orifices into a supersonic crossflow

The plume from a diamond-shaped, sonic injector orifice was studied experimentally in a Mach 3 crossflow. The structure of the plume, as well as the near injector flowfield, were examined by flow visualization techniques, and penetration height growth and maximum concentration decay were evaluated from aerothermodynamic probing measurements at two downstream stations. For the transverse injection, the jet-to-freestream dynamic pressure ratio was varied from 0.3 to 2.0. At lower dynamic pressure ratios, the plume from the diamond-shaped injector penetrated farther across the main flow compared to that from an equivalent circular injector, whereas an increase in the dynamic pressure ratio resulted in a deterioration of the plume's sharpness, and penetration of the plume became comparable to that from the circular injector. Angled injections were applied to the diamond-shaped orifice to enhance the penetration at a high dynamic pressure ratio of 2.0. Giving sweepback angle to the orifice was as effective as the case with circular injectors in enhancing the penetration. Adding a moderate yaw angle to the sweptback, diamond-shaped orifice resulted in greatly enhanced penetration, unlike the case with the circular injector. In all cases, the decay rate of the maximum concentration was almost insensitive to the orifice shape.