Two-dimensional simulation of fast gas heating in an atmospheric pressure streamer discharge and humidity effects

Gas heating in an atmospheric-pressure streamer discharge was analysed by a two-dimensional streamer discharge simulation model describing internal molecular energy transfer. Our two-dimensional streamer simulation model incorporates concepts from the fast gas heating mechanism proposed by Popov (2011 J. Phys. D: Appl. Phys. 44 285201) and our self-developed state-to-state vibrational kinetics. In dry air, gas heating occurs mainly from electron-impact dissociation reactions of O2 molecules and from quenching processes of electronically excited N2(B 3Πg, C 3Πu) molecules and O(1D) atoms. In humid air, rapid vibration-to-translation transitions of H2O and the exothermicity of the OH formation reactions additionally increase the gas temperature. It is shown that gas heating during the discharge pulse increases with humidity.