Hydrogen oxidation in a stoichiometric hydrogen-air mixture in the fast ionization wave

Abstract

Oxidation of molecular hydrogen in a stoichiometric hydrogen-air mixture in the fast ionization wave (FIW) was studied at total pressures p = 1–8 Torr, and the detailed kinetics of the process has been numerically investigated. The excitation of the gas in FIW and the dynamics of molecular hydrogen concentration were monitored using measurements of absolute H₂ radiation intensity (transition a ³Σ⁺ _g → b ³Σ⁺ _u). A comparison of calculated and experiment results allows one to draw the conclusion that the gas is predominantly excited behind the FIW front in relatively low electric fields E/n ≃ 300–600 Td at electron concentration n _e ≃ (1–2) × 10¹² cm⁻³ for a time of the order of 10 ns and can be described with good accuracy using the two-term approximation of Boltzmann's equation. In the following processes the reactions including electron-excited particles play a dominant role for times up to 100 ns, ion-molecular reactions - for the microsecond time range, reactions including radicals mostly contribute for time intervals of several milliseconds. The most critical processes have been separated for each time interval. The principal role of processes with formation of excited components that support the development of the chain mechanism of oxidation have been shown.