Mixing Enhancement in Supersonic Flow by Oscillating Electrical Discharge

Plasma-assisted mixing enhancement has the potential to improve operability limits and efficiency of high-speed airbreathing engines. We demonstrate that improvement of crossflow-jet mixing can be achieved by employing pulse-periodic electrical discharge generated within the injector nozzle. Both C2H4 and N2 jets were injected through a 3.2 mm diameter sonic nozzle into a M=2 airflow with momentum ratios ranging from J=0.65 to 6.48. The pulse-periodic electrical discharge was applied within the fuel injection nozzle at frequencies ranging from f_f=10 to 38.46 kHz, promoting the natural vorticity generated at the jet-crossflow interface. The resulting effect is visualized using a high-frequency (up to 1 MHz) focusing schlieren system and acetone PLIF, after which the images are processed to determine time-averaged penetration depth, cross-sectional area, and dimensionless perimeter deformity ratios, as well as the shear-layer natural frequency band and convection speed. It is shown that the jet YZ cross-section and shear-layer perturbation amplitudes are significantly increased, indicating enhanced diffusive mixing potential. Mechanisms for magnifying this effect will be explored in future work.