Numerical Simulation Of OH,HO₂ Radicals In Dielectric Barrier Discharge Plasmas

The dielectric barrier discharge has been used for the removal of volatile organic compounds,CO,SO₂,NOx. OH,HO₂ radicals play important for their strong oxidation in the removal of pollutants, so the research about OH and HO₂ are attractive. Study on thecharacters of radicals and their trend under the external conditions are important.This work aims at a simulation on the chemical kinetics of gas streams using atmospheric-pressure cold plasmas generated by DBD. A theoretical model is proposed based upon the elementary reactions involved with the discharge. Electron energy distribution functions are obtained by numerically solving the Boltzmann equation. The electron-molecule reaction coefficients are calculated, using the computed electron energy distribution function. The density of radicals produced and consumed in a series of reactions in the DBD is expressed by stiff ordinary differential equations. The equations could be solved numerically with the FORTRAN subroutine Treanor. Additionally, the simulated results are compared with the experimental data. The simulated results are found to be in a good agreement with the experimental data on the whole.The main results are as follows:1. The evolution of e,OH(X²Î ),OH(A²âˆ‘⁺) produced in the H₂O/He in dielectric barrier discharge plasma as a function of time are studied. The generation and the process of OH(X²Î ),OH(A²âˆ‘⁺) as well as their evolution under the influences of various gas components and discharge conditions are also discussed. It is found that the concentration of OH(X²Î ),OH(A²âˆ‘⁺) increase while H₂O,O₂ or N₂ increase . However , the OH(X²Î ), OH(A²âˆ‘⁺) production decrease at higher H₂O,O₂ or N₂ concentration. The concentration of OH(X²Î ),OH(A²âˆ‘⁺) increase while electron density,voltage and frequency increase. Moreover, the reaction mechanisms and the main physicochemical processes involved are also discussed consequently.2. The evolution of e,OH and HO₂ produced in the N₂/O₂/H₂O/HCHO in dielectric barrier discharge plasma as a function of time are studied. The generation and the process of OH,HO₂ as well as their evolution under the influences of added HCHO,O₂n H₂O are also discussed. The concentration of OH,HO₂ increase as H₂O or O₂ concentration increase initially but deciline with its further increase. With HCHO increasing, the concentration of OH increases but the concentration of HO₂ increases initially and then decreases. In addition, the generation and the process of OH,HO₂ as well as their evolution under the influences of discharge conditions are also discussed. While discharge voltage and frequency increases, the concentration of OH increases but the concentration of HO₂ increases initially and then decreases. Both the concentration of OH,HO₂ increase up to a maxium value at about 4000 Pa. Moreover, the reaction mechanisms and the main physicochemical processes involved are discussed.The characters of radicals and the trends with several parameters are studied by numerical simulation, and these results could provide experiments with theoretic references as well as proofs of validity.