Numerical simulation of the effect of water admixtures on the evolution of a helium/dry air discharge

Abstract

In this study, a 1D plasma fluid model is used to shed light into the evolution of a He/dry air (500 ppm, 79% N2 and 21% O2) dielectric barrier discharge (DBD) under different levels of water admixtures (20 to 2000 ppm). The model considers the analytical chemistry between helium, nitrogen, oxygen and water species and it is verified with experimental results to ensure its correctness. The simulation results show that water admixtures highly affect the discharge characteristics and the dominant ions in the mixture. In particular, it was observed that the increase of water in the mixture up to 600 ppm causes the reduction of the breakdown voltage, while above 600 ppm the breakdown voltage increases. Furthermore, the simulation results show that the most important positive ion in the mixture is H2O+ for 20–100 ppm of water admixtures and for 100–2000 ppm of admixtures. The most abundant negative charged species is found to be electrons for the range of water admixtures considered in this study. To interpret these results and to get an insight into the discharge evolution, the main reaction pathways of ion production are investigated and analyzed.