Modeling Study of Chemical Kinetics and Vibrational Excitation in a Volumetric DBD in Humid Air at Atmospheric Pressure

Abstract

A zero-dimensionl model is developed to study the chemical kinetics of a volumetric dielectric barrier discharge (DBD) reactor operating with humid air at atmospheric pressure. This work focuses on the relation between molecular vibrational excitation, the plasma reactor input power and the number densities of several species that are known to play an important role in biomedical applications (e.g. \(\textrm{O}_{3},\textrm{NO, NO}_{2}\), ...). A preliminary study is carried out to observe the influence of water molecules on the electron energy distribution function for different values of water concentration and reduced electric field. A simplified approach is then adopted to quantify the contribution of vibrationally-excited \(\textrm{O}_{2}\) molecules to \(\textrm{NO}\) formation. The results obtained using our detailed model suggest that for the physical conditions considered in this work \(\textrm{O}_{2}\) vibrational kinetics can be neglected without compromising the overall accuracy of the simulation. Finally, a reaction set is coupled with an equivalent circuit model to simulate the E-I characteristic of a typical DBD reactor. Different simulations were carried out considering different values of the average plasma input power densities. A particular focus was given to the influence of the Zeldovich mechanism on \(\textrm{O}_{3}\) and \(\textrm{NO}_\textrm{X}\) production performing simulations where this reaction is not considered. The obtained results are shown and the role of vibrationally excited \(\textrm{N}_{2}\) molecules is discussed. The simulation results indicate also that \(\textrm{N}_{2}\) vibrational excitation, and more precisely the Zeldovich mechanism, has a larger effect on \(\textrm{O}_{3}\) and \(\textrm{NO}_\textrm{X}\) production at intermediate input power levels.