Gui-Bing Zhao

Optical Emission Study of Nonthermal Plasma Confirms Reaction Mechanisms Involving Neutral Rather than Charged Species

Charge transfer reactions are commonly used to explain NOx conversion in nonthermal plasma. An analysis of optical emission spectra induced by pulsed corona discharge in NOx-containing argon suggests that, in fact, the contribution of charge transfer reactions to NOx conversion in nonthermal plasma is negligible. During electrical discharge in such gas mixtures, NO(B), an electronic excited state of NO formed due to the dissociative recombination reactions of NO2+ and N2O+ and the optical emission of NO(B) could be a proof that cations are responsible for NOx conversion. However, the optical emission of NO(B) is not observed, leading to the conclusion that cations are not involved to any measurable degree. Therefore, charge transfer reactions cannot play a significant role in nonthermal plasma largely because the cations are neutralized with electrons before any charge transfer reactions can occur and concentrations of radicals are far higher than those of cations, which inhibits charged particle reaction...

Effect of CO on NO and N2O conversions in nonthermal argon plasma

200–600ppm of CO inhibit NO conversion in nonthermal Ar plasma, but do not produce N2O. However, 1.01% of CO has no effect on NO conversion, but produces N2O. In general, N2O conversion in Ar plasma decreases with increasing CO concentration. These experimental results cannot be explained by charge transfer reactions of Ar+. Selectivity analysis of all excited states of Ar possibly contributing to NOx conversion without and with CO suggests that only Ar(P23) contributes to NOx conversion and CO dissociation. A kinetic model of 43 reactions is required to model NO conversion or N2O conversion in Ar without CO, whereas 81 reactions are required to model NO conversion and N2O conversion in Ar with CO. At constant gas pressure, a single set of model parameters can predict NO conversion or N2O conversion without and with CO. All experimental results can be explained using a reaction mechanism in which excited neutral states of Ar are the only active species, which supports the conclusion that cations have a ne...

Effects of synchronization of laser induced fluorescence and corona induced fluorescence in a pulsed corona reactor

Corona-induced fluorescence (CIF) of nitric oxide (NO) reveals that NO(A/sup 2//spl Sigma//sup +/) is primarily excited through N/sub 2/(A/sup 3//spl Sigma//sub u//sup +/) produced in a pulsed corona rector (PCR). The charge voltage in PCR, the time delay of the high-voltage pulse applied to the reactor, and its time jitter vary from gas composition to gas composition. This is because the reactor electric equivalent resistance in an OFF state has different values for different gas components. The PCR pulse jitter, typically a few tenths of a microsecond, for the same gas composition, varies with the frequency of high-voltage pulses due to changes in feed composition. A precise time synchronization of CIF with the laser induced fluorescence (LIF), the intensified charge-coupled device (ICCD) detector and the PCR pulse reveals that NO molecules stay in the vibrational levels of the ground state for about 700 /spl mu/s.