Modeling simulation of reactive species distribution from compact air plasma jet in N2/O2 system using COMSOL multiphysics software

Abstract

This thesis signifies the development of a comprehensive map illustrating the distribution of reactive oxygen species. This was accomplished through the integration of the Quantemol global model with COMSOL Multiphysics software. The first model is established by including 8 species and 80 neutral chemical reactions, focusing on H2 plasma and O2 plasma within the effluence region of the apparatus. Within the domain of 0D modeling, the concentrations of reactive species resulting from H2 plasma and O2 plasma, coupled with minute humidity content (0.01%) were predicted. Notably, O2 plasma exhibited a heightened capability to generate diverse reactive oxygen species in comparison to H2 plasma. This distinction was confirmed by the eminence emission intensity of atomic oxygen (O) detected through optical emission spectroscopy of O2 plasma, contrasting with the preeminence of atomic hydrogen (H) emissions in H2 plasma. Employing a 10 ms simulation timeframe in a 2D model, the evolution of the distribution of reactive oxygen species originating from H2 plasma was predominantly concentrated around the central agar surface, while the distribution from O2 plasma encompassed the entire agar surface. In the context of N2/O2 plasma, experimental inquiries unveiled that the mean density of nitric oxide (NO) dwindled from 10 ppm to 2 ppm as airflow intensified, concurrently with an elevation in ozone (O3) density from 0 ppm to 0.8 ppm. Notably, the density of NO exhibited an upward trajectory as the pulse count increased, whereas the density of O3 exhibited a decline with a heightened pulse count. However, the upper threshold of ozone density consistently remained below 1 ppm. Through 0D simulations, we attained analogous orders of magnitude for NO density and flow rate correlations through domain size reduction and the inclusion of humidity-related reactions. Nevertheless, the mismatch in O3 density between modeling and the experimental results still persisted. Our exploration harnessed a 2D modeling approach to investigate the dispersion of reactive species. This simulation illuminated the penetration of nitric oxide (NO) into the affluent region, gradually diminishing within the initial 0.5 cm, while ozone (O3) dispersed radially, culminating at the target surface. Further examination of NO and O3 density distributions at a 20 ms time interval unveiled that the peak O3 density approached 2.0 mol/m3 (49000 ppm) in close proximity to the plasma cavity, while NO density attained its zenith at 2.5x10-3 mol/m3 (61 ppm) within the plasma volume. With the passage of time on the surface target, the O3 density progressively subsided to 1.5 mol/m3 (37 ppm), diffusing radially. Through the incorporation of humidity-related reactions, an augmented model showcased NO reaching the target surface through radial dispersion, while O3 entered the affluent domain, subsiding within the initial 0.5 cm. By incorporating moisture-related reactions, supplementary models show that nitric oxide reaches the target surface and can spread radially. while ozone decreases within 0.5 cm. At a 20 ms interval, O3 density surged to 3.5x10-2 mol/m3 (860 ppm), whereas NO density was measured at 8.0x10-4 mol/m3 (20 ppm) at the core of the afterglow region, gradually diminishing to 7.0x10-4 mol/m3 (17 ppm) at a distance of 0.5 cm. These revelations contribute to a more profound comprehension of the intricate dynamics governing the distribution of reactive species within the N2/O2 plasma environment.