Numerical study of discharge characteristics of an atmospheric pressure plasma jet with a coaxial dual-channel inlet

Abstract

A two-dimensional axisymmetric fluid model was applied to investigate the influence of N2 flow velocity on the discharge characteristics of a He plasma jet with a coaxial dual-channel inlet. Helium working gas flowed in the annular space of a coaxial tube and N2 flowed in a central stainless steel tube powered by a DC voltage. When N2 flow velocity increases from 0 m/s, the jet appears to be stratified, forming the outer side and inner side of the jet, and the electron density on the outside of the jet is much higher than that on the inside. For different N2 flow velocities, the peak densities of He+ and N2(c3π) appear in the jet head, while the peak densities of He* and N2+ both appear at the dielectric nozzle and the jet head. When N2 flow velocity is low, the Penning ionization rate is lower than the electron impact ionization rate, but when N2 flow velocity is high, it is just the opposite, which can increase the concentration of reactive species and contribute to the practical application of the jet. N2 flow velocity not only changes the length and structure of the jet but also controls the uniformity of the distribution of reactive species in the jet, which indicates that there is an optimal N2 flow velocity to make the jet longer and more uniform in space, which will greatly promote the practicality and flexibility of the plasma jet and also provide meaningful insights for optimizing and controlling the characteristics of the plasma jet.