Process model for nitrogen oxidation in onset streamers in air

Abstract

A theoretical explanation is presented for the recent observation of a maximum in the production of NO2 in onset streamers in (positive) point-to-plane gaps in air at atmospheric pressure. The observed NO2 yield was an order of magnitude higher than in the steady corona obtained by increasing the gap voltage. In the exemplary case considered, the gap voltage was 7.0 kV, the mean current 1.43 mu A, the average time between consecutive streamers 0.64 ms, the height of the streamers 9.5 mm, the loss of energy about 390 eV/molecule and the yield of NO2 was 1.0*1011 molecules per streamer. According to the proposed model, the NO synthesis occurs mainly via the oxidation of vibrationally excited N2. The small diameter of streamers and the diffusion are crucial in the suppression of reverse reactions. The theoretical results are sensitive to uncertainties in input data, for example, in the cross sections for vibrational excitation and for electron-ion recombination. The analytical method with closed-form expressions was adequate for the calculations. An auxiliary series of experiments aimed at maximising the ozone yield; the least expenditure of energy was 42 eV per ozone molecule.

Modelling of plasma chemical processes in pulsed corona discharges

“…Note that in discharges in air another process of N atom and nitrogen oxide generation may take place: the reaction of O atoms with vibrationally excited N 2 molecules. The role of this process and the corresponding value of G NO grow with an increase of relative concentrations of radicals and excited molecules (with increase of the energy input) [10]. The measured values of G NO [10], as G N [9], do not depend on the energy input (on the applied voltage).…”

“…The role of this process and the corresponding value of G NO grow with an increase of relative concentrations of radicals and excited molecules (with increase of the energy input) [10]. The measured values of G NO [10], as G N [9], do not depend on the energy input (on the applied voltage). The lack of such dependence and the closeness of the values G NO [10] and G N [9] confirm the assumption that reaction ( 1 Note that calculated values of G O for positive streamers are about an order of magnitude greater than obtained in [2] for the glow regime of a positive corona discharge.…”

“…If streamer parameters in air and nitrogen are assumed to be identical, then recalculation of this Gvalue to air gives G N air ≈ 0.8 G N nitrogen = 0.34. In [10] the value G NO = 0.26 for nitrogen oxides production by positive streamers in air in point-plane gaps has been obtained. Nitrogen oxides NO, NO 2 , NO 3 are formed in a chain of reactions, the first link of which is reaction (1).…”

An experimental comparison between electrode shapes for NOxtreatment using a dielectric barrier discharge

“…The negative value means that NO x is generated in the plasma reactor. This may be caused by a chemical reaction between NO and O 3 producing NO 2 [12]. By our previous report, ozone could be detected only after the concentration of NO drops to a low level [7].…”

Modelling of plasma chemical processes in stable corona discharges at thin wires

“…At fixed R there is an optimum rl, where 5is minimal. The typical values of 5are nearly the same as in a streamer regime of positive coronas [3] and two to three times higher than in dielectric barrier discharges [20]. In a steady positive corona the values of 5, are an order of magnitude higher than in a negative one.…”