Properties of nonadiabatic combustion waves in competitive exothermic reactions

Abstract We study the properties of travelling combustion waves in a diffusional thermal model with a two-step competitive exothermic reaction mechanism considering the system in one spatial dimension under nonadiabatic conditions. Based on the notion of the crossover temperature, the model is first examined analytically to predict the behaviour of travelling combustion waves in the limit of large activation energies. It is then studied numerically over a wide range of parameter values, such as those describing the ratios of the enthalpies, pre-exponential factors and activation energies. It is demonstrated that the nonadiabatic flame speed as a function of these parameters is a single-valued monotonic function with two flame regimes identified, each of which represents the region of the parameter values when one reaction dominates the other, while the flame speed as a function of the activation energy of the reaction R2 (the exothermicity parameter) is either a c- or m-shaped. The extinction conditions for these two flame regimes are investigated analytically.