Characterization of a High-Frequency Pulsed-Plasma Jet Actuator for Supersonic Flow Control

Abstract

thepulsed-plasmajet,thejetisinjectednormallyintoaMach3crossflowandthepenetrationdistanceismeasuredby using schlieren imaging. These measurements show that the jet penetrates 1.5 boundary-layer thicknesses into the crossflow andthe jet-to-crossflowmomentum fluxratioisestimated to be0.6.Aseries of experiments wasconducted to determine the characteristics of the pulsed-plasma jet issuing into stagnant air at a pressure of 35 torr. These resultsshowthattypicaljetvelocitiesofabout250 m=scanbeinducedwithdischargeenergiesofabout30mJperjet. Furthermore, the maximum pulsing frequency was found to be about 5 kHz, because above this frequency the jet beginstomisfire.Themisfiringappearstobeduetothe finitetimeittakesforthecavitytoberechargedwithambient air between discharge pulses. The velocity at the exit of the jet is found to be primarily dependent on the discharge current and independent of other discharge parameters such as cavity volume and orifice diameter. Temperature measurementsaremadeusingopticalemissionspectroscopyandrevealthepresenceofconsiderablenonequilibrium between rotational and vibrational modes. The gas heating efficiency was found to be 10% and this parameter is shown to have a direct effect on the plasma jet velocity. These results indicate that the pulsed-plasma jet creates a sufficiently strong flow perturbation that holds great promise as a supersonic flow actuator.