Modeling of atmospheric pressure plasma processing of gases and surfaces

Atmospheric pressure plasma based processes have become indispensable components of numerous industrial applications owing to their high efficiencies and low costs. In this work, we computationally investigate the applications of dielectric barrier discharges (DBDs), one of the commonly used atmospheric pressure plasma devices, to the remediation of nitrogen oxides (NO_x) from diesel exhausts and to the surface treatment of polypropylene (PP) for improved adhesion. We determine the kinetics of these processes in order to develop methods to optimize their energy efficiencies.; Unburned hydrocarbons (UHCs), inevitably present in diesel exhausts, significantly affect the plasma remediation of NO_x by oxidizing NO, the major form of NO_x in the exhaust, into NO₂. The efficiency of NO_x removal increases when a given amount of energy is deposited in a large number of shorter-duration pulses as opposed to in a single pulse.; Soot particles significantly affect the plasma remediation of NO _x by changing the composition of NO and NO₂ in the plasma. In general, NO_x removal improves in the presence of soot. Heterogeneous reactions on soot also result in the production of CO. At high number densities and large diameters, soot particles significantly affect the ionization kinetics in the gas phase. When using repetitively pulsed discharges in the presence of soot, both NO_x removal improves and soot oxidation increases.; Spatial dependencies can affect the energy efficiencies of remediation. Localized energy deposition in the streamer results in production of radicals in confined regions. Consumption of these radicals by UHCs limits their diffusion to outer radii thereby affecting the remediation.; Atmospheric pressure plasma processing of PP in humid air increases the surface densities of alcohol, peroxy, acid, and carbonyl groups. However, significant amounts of O₃ and N_xO_y are generated in the gas phase. Increasing the relative humidity results in decreased production of O₃ and increased concentrations of peroxy and acid groups on the surface. Increasing the gas temperature increases the surface concentration of peroxy radicals and decreases the concentrations of alcohol, carbonyl, and acid groups. For a given energy deposition, increasing the web speed results in decreased surface densities of peroxy, alcohol, carbonyl, and acid groups.