Ionic wind of a needle-to-plate dielectric barrier discharge

Abstract

The present study aims at investigating the ionic wind produced by a dielectric barrier discharge ignited between a needle and a grounded plate electrode covered by a dielectric material. The needle is powered by a sine high voltage vAC(t) and the electrode gap is equal to 15 mm. Preliminary measurements of the discharge current highlighted that two different discharges take place during one voltage cycle. During the positive going-cycle, there is a positive corona discharge composed of streamers, their frequency (close to 5 kHz) and magnitude (a few mA) increasing with the magnitude of the applied voltage. During the negative-going cycle, a negative corona discharge occurs, its current highlighting the presence of Trichel pulses whose the frequency varies between 100 kHz and 500 kHz.Then we investigated the ionic wind produced by the DBD with the help of a 20 kHz PIV system (particle image velocimetry) in order to access to time-averaged and time-resolved data. First, we charaterized the effect of the magnitude of vAC(t) and its frequency value fAC on the time-averaged ionic wind. Secondly, we investigated the temporal behavior of the ionic wind as a funtion of the high voltage frequency. Two main behaviors have been highlighted. At low frequency (up to 200 Hz), the sine high voltage results in a pulsed ionic wind, with a velocity peak at each half cycle: there is a first flow acceleration due to the positive corona discharge and a second one during the negative corona, the velocity during the positive discharge being higher than the one measured during the negative discharge. At higher frequency (from 500 Hz up to 1000 Hz), the positive ionic wind takes over the negative one and the velocity peak due to the negative discharge is very weak. At 2000 Hz, there is only one single flow acceleration per voltage cycle, because the ionic wind produced by the positive corona discharge takes totally over the ionic wind produced by the negative corona because it is more intense and faster.