Kinetic analysis of the chemical structure of waves of filtration combustion of gases in fuel-rich compositions

The structure of heat release and the dynamics of formation of radicals and methane oxidation in a wave of filtration combustion of gases in fuel-rich methane–air compositions is studied with the use of skeleton diagrams and sensitivity analysis. Depending on heat release, the wave is divided into a preheating zone, an exothermic zone characterized by partial oxidation of methane in the reaction CH$_4$+0,5O$_2$ = CO +2H$_2$, and an endothermic zone with the conversion processes CO + H$_2$O = CO$_2$ + H$_2$ and CH$_4$ + H$_2$O = CO + 3H$_2$. It is shown that the composition of products in the wave front is essentially nonequilibrium. Several typical regions are also identified from the viewpoint of prevailing reactions of formation of the basic radicals in the wave. Thus, the dominating mechanism of chain branching is the reaction CH$_3$ + O$_2$ = CH$_3$O + O in the “low-temperature” region, H$_2$O$_2$(+M) = 2OH (+ M) и HO$_2$ + CH$_3$ = CH$_3$O + OH in the “transitional” region, and H + O$_2$ = O + OH in the “high-temperature” region. Two former regions correspond to the preheating zone and the latter region corresponds to the exothermic peak of the wave of filtration combustion of gases.