Numerical simulation study on the reaction mechanism of atmospheric pressure non-equilibrium CO₂/H₂O plasma discharge

Abstract

This study develops a two-dimensional fluid model for atmospheric pressure non-equilibrium CO₂-H₂O plasma needle-plate configuration, incorporating a comprehensive set of plasma chemical reactions and photoionization effects. It focuses on investigating the influence of the CO₂/H₂O concentration ratio and quenching pressure on plasma streamer initiation and propagation dynamics. Numerical simulations show that increasing initial water vapor content significantly reduces electron energy and density, causing the discharge channel to contract when the reduced electric field is below 200 Td, due to strong dissociative adsorption reactions between electrons and water molecules. At higher reduced electric fields (above 200 Td), variations in water vapor content have minimal impact on primary electron transport parameters, likely because dissociative and ionizing collisions between electrons and CO₂/H₂O molecules become dominant. Increasing the quenching pressure enhances photoionization, but plasma discharge remains primarily sustained by direct electron-impact ionization. Low initial water vapor content and elevated quenching pressure both accelerate streamer propagation, with the concentration ratio exerting a more significant effect. Finally, the primary reaction pathways for key products (CO, OH, and electrons) are analyzed. These findings contribute to a better understanding of how the reactant concentration ratio and quenching pressure regulate the discharge reaction mechanism in atmospheric pressure non-equilibrium CO₂-H₂O plasma.

Graphical abstract

Keywords

plasma discharge / CO₂/H₂O concentration ratio / quenching pressure / reaction pathways

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