Initiation of combustion of a methane-air mixture in a supersonic flow behind a shock wave during laser excitation of O2 molecules

Abstract

The possibility of initiating detonation of CH4 + air in a supersonic flow behind an oblique shock wave under the exposure of the mixture to laser radiation with wavelengths λI=1.268 µm and 762 nm is analyzed. It is shown that this irradiation leads to excitation of O2 molecules to the a 1Δg and b 1Σ g + states, which intensifies the chain mechanism of combustion of CH4/O2 (air) mixtures. Even for a small value of the laser radiation energy absorbed by an O2 molecule (∼0.05–0.1 eV), detonation mode of combustion in a poorly inflammable mixture such as CH4/air can be realized at a distance of only 1 m from the primary shock wave front for relatively small values of temperature (∼1100 K) behind the front under atmospheric pressure.