Experimental characterization of a pulsed plasma jet

An experimental investigation was conducted to characterize the performance of a pulsed plasma jet actuator to determine its potential as an active supersonic flow control device. Electro-thermal heating from an electric discharge heats and pressurizes gas in a small cavity (183 mm³) which is exhausted through a circular orifice (0.83 mm diameter) into quiescent air. The electric discharge is facilitated by a two-circuit, three-electrode configuration. A high-voltage (∼3.6 kV) / low-current trigger produces sufficient ionization in an air gap to cause electric breakdown between an anode connected to a capacitor and a grounded cathode with a potential difference of approximately 570 V. The resulting jet structure, velocity, and duration are found to be greatly dependent on capacitor size. Three capacitor sizes were tested in this study: 0.25, 2, and 25 μF depositing electrical energies of 41 mJ, 330 mJ, and 4.0 J, respectively. Voltage measurements, phase-locked and high-speed schlieren imaging, and particle image velocimetry measurements were used to describe the electric requirements and flow field produced by this actuator for single pulse operation. For the 0.25 and 2 μF capacitors, the jet exhausts as a train of ring vortices with peak jet velocities of 130 and 320 m/s, respectively. The 25 μF capacitor-driven jet behaves more conventionally with a sustained exhaust and a peak velocity near 500 m/s. High jet velocities, coherent vortical structures, and large penetration depths suggest the feasibility of this pulsed plasma jet actuator to influence supersonic flows.