Spatial Distributions of Chemical Species in a Pin-to-plate Dry Air Corona Discharge

The reactive oxygen and nitrogen species generated by plasma have demonstrated consequential effects on diverse commercial applications. Hence, studying the chemistry and spatial distribution of reactive species in plasma is imperative for understanding the influence of plasma in various applications. This study aims to systematically explore the plasma chemistry of a pin-to-plate negative direct current (DC) corona discharge in dry air, using simulations based on a two dimensional (2D) axisymmetric fluid model. The model encompasses a comprehensive set of chemical reactions involving 33 biomedically active species (ROS and RNS). This study entails a rigorous evaluation of the 2D spatial distribution of all chemical species, detailing their minimum and maximum values, at a needle voltage of −10 kV. To enhance visualization and enable comparisons, we integrate contour lines into the density distributions to indicate the average density of each species. \({\text{N}}_{2}\left({\text{A}}^{3}\sum\right)\) among nitrogen species, O₃ and \({\text{O}}_{2}\left({\text{a}}^{1}\Delta\right)\) among oxygen species, and N₂O among NOx species exhibit the highest average density in the simulation domain. Furthermore, key reactions involved in the production and consumption of each species are thoroughly discussed. Additionally, the research examines the influence of needle voltage, ranging from −5 to −12.5 kV, on the peak and average densities of all species investigated. Lastly, to validate the simulation model, an experimental study of the pin-to-plate negative DC corona discharge is conducted, during which the voltage-current characteristics and optical emission spectrometry (OES) profiles are measured. The simulation results are in good agreement with the experimental data.