Effect of a pulsed high-current discharge on hydrogen-air mixtures
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Effect of a Pulsed High-Current Discharge on Hydrogen–Air Mixtures N. A. Popov Skobel’tsyn Institute of Nuclear Physics, Moscow State University, Leninskie gory, Moscow, 119899 Russia Received August 20, 2007; in final form, October 23, 2007
Abstract—A self-consistent model describing the influence of a pulsed discharge on H2–air mixtures is developed. The model includes the processes of ionization, dissociation, and excitation of the gas molecules by electron impacts; a set of ion–molecular reactions determining the time evolution of the charged particle densities; the processes involving electronically excited atoms and molecules; and a set of reactions describing the ignition of hydrogen–oxygen mixtures. Results are presented from simulations of the oxidation dynamics of hydrogen molecules in a stoichiometric H2–air mixture and the ignition of such a mixture under the action of a pulsed high-current discharge. The simulation results are compared with available experimental data and calculations performed by other authors. PACS numbers: 52.25Dg, 82.33Xj DOI: 10.1134/S1063780X08050048
1. INTRODUCTION
sity of H2( a Σg ) molecules. In simulating the influence of the discharge, the measured values of the electric field and discharge current were used to calculate the reduced field E/N and the electron density Ne, from which the densities of atoms and excited particles produced during a discharge were determined. The numerical model took into account a change in the mixture composition with increasing number of discharge pulses. An important result of [5] is the conclusion that, for simulations to agree with experimental data, the model must take into account nonequilibrium vibrational kinetics. In [6], a kinetic model was presented that describes the influence of nonequilibrium electric-discharge excitation on the ignition of hydrogen–oxygen mixtures at atmospheric pressure. The simulations were performed at a fixed electron temperature in the range Te = 1.3– 1.6 eV. The production rates of charged and neutral chemically active particles in a discharge were determined using results of [7, 8]. It should be noted, however, that the results of [7] were obtained for N2 : O2 mixtures, while those of [8], for pure hydrogen; therefore, their application to H2 : O2 mixtures may lead to considerable errors. An important conclusion drawn in [6] is that ion– molecular reactions (in particular, reactions involving negative ions) may considerably affect the ignition time of hydrogen–oxygen mixtures. According to calculations [6], the plasma produced in the H2 : O2 = 2 : 1 mixture at P = 1 atm, T0 ≅ 900 ä, and Te ≅ 1.4 eV is an ion– ion plasma. Under these conditions, ion–molecular reactions at a fixed value of Te can significantly affect the electron density and, therefore, the production rates 3 +
In recent years, the problem of fast nonequilibrium ignition of combustible mixtures by gas discharge plasmas [1–4] has attracted considerable attention. Interest in this problem stems from the possibility of using gas d
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