Modeling of an Atmospheric Pressure Plasma Jet with Flow Effects

Abstract

In this study, the interaction of a cold atmospheric pressure plasma helium jet with a dielectric surface is investigated. A self-consistent, multiple species, two temperature plasma solver is coupled with a multiple species, compressible Navier-Stokes solver to model the coupled flow and plasma discharge kinetics. The Navier-Stokes solver is used to obtain steady state stagnation flow profiles for a low speed helium jet exhausting into ambient air and impinging against a dielectric surface. The plasma solver is then used to simulate a 150 nanosecond pulse discharge leading to the formation and propagation of a plasma bullet within the helium jet. Initially, the plasma forms within the tube and propagates along the tube surface as a fast ionization wave driven by large induced electric fields produced by space charge and charge trapped on the dielectric surface. When the discharge reaches the gap, it transitions to a constricted fast ionization wave that propagates along the helium-air interface. When the fast ionization wave (plasma bullet) reaches the dielectric surface, charged species are delivered to the surface and the discharge propagates parallel to the wall as a surface driven discharge. The surface driven discharge ceases to propagate once the quantity of air to helium is great enough to quench the hot electrons and prevent further ionization. Due to the low speed of the flow discharge and the short life times of the radical species such as O, most of the radical species delivered to the surface are a result of the surface discharge that forms after the plasma bullet impinges against the surface.