Numerical Investigation on the Effects of Chemical Reactions on the Discharge Characteristics and Energy Balance of a Nanosecond Repetitive Pulsed Dielectric Barrier Discharge

Numerical investigation on a nanosecond repetitively pulsed dielectric barrier discharge (NS-DBD) in air is a temporal and spatial multi-scale problem involving a large number of species and chemical reactions. To know the effects of the species and chemical reactions on the discharge characteristics and energy balance, a high voltage repetitive plane to plane NS-DBD is numerically studied. Four groups of species and the corresponding chemical reactions are adopted in the investigation. The most complex one has 31 species and 99 chemical reactions that contains all reaction types, in particular, the vibrational-translational relaxation reactions, whereas the simplest one has only 4 species and 4 reactions, which represents the main kinetic processes. The others are in between. The discharge energy reaches to a periodic phase equality state after the second pulse in the repetitive pulses, and the present analysis is focused on the 7th pulse. All the N 2 / O 2 mixture reaction models predict almost the same discharge energies, which are qualitatively similar with that in the simplified 4-species model. The prediction of the discharge energy is determined by the electronic excitation and the energy gain by ions, but the vibrational excitation, negative ions, associative ionization, dissociation of nitrogen and oxygen molecules have very weak effects. The gas heating is determined by the exothermic reactions and the ions. The main processes in the fast and slow gas heating are the energy release of ions and the exothermic reactions, respectively. The negative ions, vibrational excitation, and associative ionization have very weak effects on the gas heating during the high voltage pulse, but they have considerable effects at a larger time scale. The magnitudes of the fast gas heating efficiency ( η G H ) are in the range of 41%∼47% in the N 2 / O 2 mixture reduced kinetic models, but η G H is higher in the 4-reaction model.