Mechanism for electric breakdown in a chemically nonequilibrium system and the influence of the chain oxidation reaction in an H2-air mixture on the breakdown threshold

Abstract

A mathematical model is developed and a numerical analysis is performed for an electric breakdown in a hydrogen-air mixture with a low concentration of H2. It is shown that, at sufficiently low pressures p<10−2 atm, a small molecular-hydrogen additive (η=5×10−5–5×10−3) decreases the reduced field of an electric breakdown in air by a factor of more than 2 because of the appearance of an additional detachment process associated with the chain hydrogen-oxidation reaction. Detailed calculations are performed for the mean number density of negative oxygen ions [O2−]=103 cm−3 and the hydrogen concentration in air [H2]=0.5, 0.05, and 0.005%. It is found that, for [H2]=0.005%, the breakdown can develop under the action of a geoelectric field of 1.3 V/cm at p≃10−4 atm.