Chapter III. Specificities of the Mechanism and Energy of Branching Chain Processes

Abstract

It is shown that the features of chain processes are determined mainly by the fact that most of the internal energy of the initial reagents is converted into the energy of free valences of atoms and radicals. This results in high concentrations of active particles, which react with the initial reagents at higher rates, providing intensive self-heating, which additionally accelerates the process. It is noted that, without considering the chain nature of reactions, it is impossible to explain ignition upon heating, since the high activation energies of reactions of only molecular reagents exclude an increase in the rate during heating. Taking into account the chain nature of combustion reactions made it possible to explain ignition upon heating and develop a theory of the phenomenon. An explanation is given to the most important characteristic of gas combustion: the length of reaction chains, which determines the role of the chain mechanism in combustion, and the dependence of kinetics on temperature. A solution to the problems of the third flammability limit, confirmed by kinetic and spectroscopic experiments, was obtained, as well as the evidence of the presence of HO₂ radicals in the flame, their active role in the heterogeneous development of reaction chains and in combustion in general. The possibility of replacing the solution of diffusion differential equations by effective kinetic parameters when describing combustion has been experimentally proven.