Initiation of combustion of a CH4-O2 mixture in a supersonic flow with excitation of O2 molecules by an electric discharge

Abstract

The possibility of intensification of ignition of a methane-oxygen mixture in a supersonic flow behind the front of an oblique shock wave by means of excitation of O2 molecules to the states a1Δg and b1Σg+ in an electric discharge is discussed. Through numerical simulations, activation of O2 molecules by an electric discharge is demonstrated to speed up chain reactions in the CH4-O2 mixture and to reduce the induction-zone length. Even a small amount of energy input to O2 molecules in the discharge (≈3·0−2 J/cm3) can reduce the ignition-delay length by a factor of hundreds and initiate combustion at distances of ≈1 m from the discharge zone at comparatively low temperatures of the gas behind the front (≈1000 K) and moderate pressures (≈105 Pa). Excitation of O2 molecules by an electric discharge is much more efficient than simple heating of the mixture.