Production mechanism of reactive species in atmosphere pressure non-equilibrium plasma jet

Highly energetic electrons and reactive species, O and OH for example, in atmospheric non-equilibrium plasmas can react with pollutants and decompose them. Consequently, we numerically and experimentally studied the pulsed DC plasma jet propagation and OH production mechanism in atmospheric pressure. The simulation results reveal that the sheath formed near the dielectric tube inner surface separates the plasma channel from the tube surface. The strong electric field at the edge of dielectric field enhances the ionization in the air mixing layer, therefore, the streamer head changes into the ring shape when the streamer runs out of the tube. Penning ionization will dominate the ionization reactions and will increase the electric conductivity of plasma channel. For the plasma jet in the open air, the dissociation of H2O by electron, the recombination of H2O+ by electrons and dissociation of H2O by O(1D) are the main reactions to produce OH. The contribution of the dissociation of H2O by electron is more than that of the others.The addition of N2, O2 and air to the working gas will slightly increase the OH density, which is attributed to the increased electron density through Penning ionization. Although the addition of H2O increases the OH density inside tube dramatically, because of the air diffusion efficiently in the mixing layer, the limited increase of H2O mole fraction will only result in slightly increase of OH density outside the tube. The pulse number is found to be an efficient way to control the plasma activity. © 2016, High Voltage Engineering Editorial Department of CEPRI. All right reserved.