Initiation of combustion by laser-induced excitation of molecular vibrations of reactants

Abstract

The features of combustion initiation in H2/air and CH4(C2H2)/air mixtures under laser-induced excitation of the asymmetric mode of ozone molecules added in a small amount to the mixture are analyzed. It was shown that such an approach to supply radiation energy to the combustible mixtures reduces the induction time and decreases the ignition temperature at a small energy of laser radiation delivered to the mixture. These effects are explained mostly by two factors — the intensification of chain reactions due to acceleration of O-atom formation during dissociation of vibrationally excited O3 molecules and the heating of the mixture due to a faster decomposition of O3 molecules. The considered method of ignition/combustion control is much more effective (by a factor of 10–100) than the method based on heating the gas by resonance laser radiation in the case where the characteristic time of highly reactive radical and atom formation does not exceed significantly the relaxation time of the asymmetric mode of the O3 molecule.