A zero-dimensional model is used to study the processes of physical and chemical reactions in atmospheric plasma with different ionization degrees near the ground(0 km). The temporal evolutions of CO, CO2and other main reactants(namely OH and O2), which affect the conversion of CO and CO2, are obtained for afterglow plasma with different initial values. The results show that the consumption rate of CO is largest when the initial electron number density ne0=1012cm-3, i.e. the ionization degree is 0.000004%. The number density of CO2is relatively small when ne0=1016cm-3, i.e. the ionization degree is 0.04%, whereas they are very close under the condition of other ionization degrees. Considering the total number densities of CO and CO2and the consumption rate of CO comprehensively, the best condition is ne0=1013cm-3, i.e. the ionization degree is 0.00004% for reducing the densities of CO and CO2in the atmospheric plasma.The temporal evolutions of N+, Ar+, CO+and CO+2are also shown, and the influences on the temporal evolutions of CO and CO2are analyzed with increasing ionization degree.
The dielectric barrier discharge characteristics in helium at atmospheric pressure are simulated based on a one-dimensional fluid model. Under some discharge conditions, the results show that one discharge pulse per half voltage cycle usually appears when the amplitude of external voltage is low, while a glow-like discharge occurs at high voltage. For the one discharge pulse per half voltage cycle, the maximum of electron density appears near the anode at the beginning of the discharge, which corresponds to a Townsend discharge mode. The maxima of the electron density and the intensity of electric field appear in the vicinity of the cathode when the discharge current increases to some extent, which indicates the formation of a cathode-fall region. Therefore, the discharge has a transition from the Townsend mode to the glow discharge mode during one discharge pulse, which is consistent with previous experimental results.
A plasma column with a length of about 65 cm is generated in the upstream region of a plasma jet using dielectric barrier discharge configurations. The effects of experimental parameters such as the amplitude of the applied voltage and the driving frequency are investigated in aspects of the plasma column by the optical method. Results show that both the plasma length and the propagating velocity, as well as the discharge current, increase with the increase in the applied voltage or its frequency. The discharge mechanism is analysed qualitatively based on streamer theory, where photo-ionization is important. Furthermore, optical emission spectroscopy is used to investigate the electric field intensity of the upstream region.
