Ignition delay time in a methane–air mixture in the presence of iron particles

Ignition of a stoichiometric methane–air mixture in a piston-driven setup at temperatures of 900–1200 K and pressures of 1–1.2 MPa is experimentally studied. The experiments reveal the emergence of bright points in the duct of the facility. The measurements show that luminescence in the volume appears almost immediately after the end of the compression stage, whereas the methane–air mixture ignites only after 4–5 ms. Presumably, these bright points appear owing to ignition of fine particles. It is experimentally found that ignition of these particles reduces the ignition delay time of the gas mixture. A physicomathematical model of ignition of methane–oxygen–nitrogen/argon mixtures in the presence of fine metal particles is proposed to obtain a theoretical description of this phenomenon. This model takes into account both detailed kinetic mechanisms of chemical conversions in the reacting gas mixture and reduced kinetic mechanisms of oxidation of metal particles. Calculations by this model show that ignition of particles at low temperatures (less than 1100 K) leads to reduction of the ignition delay time of the gas mixture.