Chemical reactions in the low-temperature zone of a laminar rich propane–air flame

The mechanism of chemical reactions in the low-temperature zone of a rich propane–air flame is considered. It is shown that at temperatures of 300–700 K, intense chemical reactions proceed with the formation of end products and that the water concentration reaches an intermediate equilibrium value even at a temperature of 685 K. In this zone of the front, the diffusion of atomic hydrogen from the high-temperature zone plays a determining role and water is formed mainly by the reactions H + O$_2$ + M $\Rightarrow$ HO$_2$ + M, HO$_2$ + HO$_2$ $\Rightarrow$ H$_2$O$_2$ + O$_2$, H$_2$O$_2$ (+M) $\Rightarrow$ 2OH (+M), C$_3$H$_8$ + OH $\Rightarrow$ C$_3$H$_7$ + H$_2$O. Propane reacts with active centers more effectively than molecular hydrogen. Its primary reactions are due to the interaction with OH and HO$_2$ radicals. Arguments are given in favor of the thermal-diffusion nature of the superadiabatic temperature phenomenon in rich propane–air flames.