Characterization of an atmospheric pressure misty plasma discharge *

Misty plasmas are typically defined as plasma containing small liquid droplets and therefore makes it a multiphase system. In an attempt to characterize an atmospheric pressure misty plasma discharge a flat plate dielectric barrier discharge (DBD) is designed that utilizes a stagnation flow field for the introduction of water droplet laden flow. The water droplets in the form of spray are introduced through an annulus from the bottom plate, which also acts as the grounded electrode. The interaction of the liquid spray and the DBD plasma discharge is characterized through measurements of the voltage-current characteristics, optical emission spectrum and discharge visualization. An AC driven power supply having a 22 KHz frequency was utilized to drive the DBD discharge and maintain a peak voltage and current of ~8 kV and ~100 mA respectively. Preliminary results show that the DBD discharge operates in the filamentary mode with  visible emissions typical of an air discharge when no spray is introduced. With the introduction of the spray droplets the filament sizes decrease significantly but increases the emission intensity. The emissions in the range of  ~550 – 750 nm are observed in the presence of water which are typical of water vapor emission lines. These emission lines suggest that the liquid phase water droplets undergo phase transition and interacts in the gas-phase plasma kinetics. Energy deposition measurement suggest that in presence of water droplets the net energy deposition is lower.