Effect of electron temperature and concentration on production of hydroxyl radical and nitric oxide in atmospheric pressure low-temperature helium plasma jet: Swarm analysis and global model investigation

Abstract

This work presents a numerical analysis by zero-dimensional global model of the influence of electron temperature and concentration on production of OH and NO for helium plasma jet propagating in the atmosphere of humid air. The calculations are done for the constant electron temperatures (1–4 eV) and concentrations (1010 cm−3 to 1014 cm−3). The mole fractions of air and water vapor vary from 100 to 10,000 ppm. The presented analysis reveals that at low electron temperature and H2O contents, the dissociative electron attachment to O2 dominates over attachment to H2O in production of OH. At higher amount, H2O modifies the high-energy tail of electron distribution function and increases rate coefficients for electron impact processes. Dissociative electron attachment to H2O dominates in the production of OH at 1 eV and remains important at higher energies when processes with O(1D), O(1S), O2(1∆) produce OH. Impact dissociation of H2O dominates over the dissociative attachment at 3 and 4 eV. NO comes mainly from air effluent in the plasma and O + NO2 at 100 ppm of H2O. Above 2 eV, the conversion process between OH and NO dominates in NO production at higher amount of H2O. Regarding dependencies on electron concentration, at low electron temperatures, electron distribution function is affected only at 1014 cm−3. But in the case of higher temperature, electron concentration and water vapor have negligible influence. The best agreement with measured data is obtained for electron concentration 1010 cm−3 and at temperature of 2 eV for OH and 1012 cm−3 and 3 eV for NO.

Keywords

• plasma modeling
• plasma jet
• reactive oxygen and nitrogen species
• global model