Recombination Mechanism of Heating of Admixture Microparticles in Initiation of Low-Temperature Ignition

The contribution from the recombination of radicals on the surface of an admixture microparticle in a reacting hydrogen/oxygen/argon or propane/oxygen/argon combustible mixture, to the heating of a microparticle, has been analyzed. An estimation has been made of possible ignition acceleration from a hotspot in the form of heated microparticle, at temperatures of 800-1100 K, under conditions when a decrease in ignition delays is observed in experiments in shock tubes and fast compression machines. It is shown that, depending on microparticle size and concentration of radicals in mixture, the recombination heating of the microparticle can range from tens to hundreds of degrees in the early stages of combustion. This can lead to a decrease in the ignition delay by several times. The proposed mechanism can be considered as one of the possibilities to eliminate the discrepancy between the experimentally observed ignition delays and those calculated using detailed kinetic mechanism, under the specified conditions.