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The subject of this study is the comparative analysis of the kinetic mechanisms that proceed in a methane–air mixture when O2 molecules are excited to the electronic state by laser photons with wavelength λI = 762.346 nm and when O2 molecules dissociate due to the absorption of laser radiation with λI = 193.3 nm. The efficiencies of both methods of combustion initiation are compared with each other and against the method of laser-induced thermal ignition. Numerical simulation shows that for methane–air mixture the excitation of O2 molecules to the state is more effective in reducing the induction time and in lowering the ignition temperature than the method of photodissociation of O2 molecules by laser radiation at 193.3 nm wavelength. In order to ignite a stoichiometric CH4–air mixture at identical temperature it is needed to supply twofold greater energy upon photodissociation of O2 molecules than in the case of O2 molecule excitation. However, both the laser-induced excitation of O2 molecules to the state and O2 molecule dissociation by laser photons with λI = 193.3 nm are much more effective in combustion initiation than the method based on heating the mixture by laser radiation.

The extensive analysis of chain mechanism development in the Al–CH4–O2 mixture is conducted on the basis of a novel kinetic model taking into account the latest theoretical data on rate constants of elementary reactions. The physical properties of Al-containing compounds, needed for the calculation of their transport coefficients, are estimated with the use of a quantum-chemical approach. It has been shown that the addition of a small amount of aluminum nanoparticles to the methane–oxygen mixture substantially accelerates the chain mechanism and results in the decrease of the ignition delay and the increase of the laminar flame speed. The higher the concentration of Al in the mixture, the greater the effect of combustion enhancement. The principal reactions responsible for this effect are indicated.

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