Modeling of Plasma-Chemical Processes in a Mixture CO2 : N2 : H2O when Excited by a Pulsed Discharge

Abstract

A computational and theoretical study of the production of various chemical compounds in a mixture of CO₂ : N₂ : H₂O = 5 : 5 : 0.3 has been carried out at atmospheric pressure when exposed to an electric discharge current with a pulse duration of 2.5 μs. Two options for discharge formation are considered: a pulsed discharge with a constant current amplitude and a discharge with an LC circuit. For a discharge with a constant current amplitude, calculations have been performed in two approximations: constant pressure and constant gas temperature. In the discharge with an LC circuit, calculations have been carried out for the case of constant pressure. The dynamics of concentrations of various components has been analyzed both at the discharge pulse stage and at the afterglow stage (up to 10 s). According to the calculations, at the discharge stage, the main processes are the excitation and dissociation of molecules by electron impact. At this stage, O, H, N, and C atoms, CO molecules, and OH radicals are formed. At a subsequent stage, more complex stable molecules are formed as a result of various chemical reactions. It is shown that the concentrations of CO, O₂, H₂, NO, and N₂O are weakly dependent on the approximation used, while the concentrations of products such as HNO₂, HNO₃, and NH₃ turn out to be significantly lower than in the case of constant temperature in the case of constant pressure. Calculations have shown that under the conditions considered, the main positive and negative ions in the discharge plasma are hydrated ions. It has been also established that the exclusion of ion hydration processes leads to a decrease in the magnitude of the reduced electric field and an increase in the gas temperature at the quasi-stationary stage of discharge combustion.