LAUSR

In this work, a two-dimensional fluid model of the needle-plane discharge plasma has been built to numerically investigate the spatio-temporal evolution characteristics of the electric field intensity and electric potential as well as generating and consuming reaction pathways of various oxygen species in a He–O2 atmospheric pressure plasma jet. Simulation results have indicated that the region of high electric field intensity moves in the direction of the plane electrode with the formation and propagation of an ionization wave. The region of low electric field intensity exists between the needle electrode and the head of the ionization wave, and its area increases continuously. The obvious voltage drop and local electric field enhancement occur between the head of the ionization wave and the plane electrode. Electron attachment reactions e + O2 → O + O− and e + 2O2 → O2− + O2 produce negative ions O− and O2−. More than 80% of the positive ions O2+ and H2O+ come from Penning ionizations between He* and molecules O2 and H2O. e + O2 → e + O + O(1D) is the main pathway to generate O and O(1D). O(1D) + H2O → 2OH and O + H + H2O → OH + H2O produce 69.3% and 39.2% of OH, respectively. 2O2 + O → O3 + O2 is the key generating reaction of O3.