STRUCTURE AND STABILITY OF FLAMES WITH TWO SEQUENTIAL REACTIONS*

Abstract. An asymptotic analysis is presented for the structure of steady planar flames, and for their response to nonplanar perturbations, when the reaction mechanism can be modelled by two sequential reactions with the same large value of the activation energies. The analysis is carried out, with the thermal-diffusive approximation, for the distinguished "merged" regime, when the two reaction constants are such that the two reactions occur in a single thin zone. The nonlinear response of the flame can be described by a model involving only three parameters, associated with the Lewis number of the main reactant and the Lewis number and peak concentration, in the reaction zone, of the intermediate species. A linear stability analysis of the planar flame suggests that close to the boundary of the domain of stability one can expect: chaotic response, cellular flames, travelling waves, pulsating flames or an instability associated with unsteady effects in the thin reaction zone. 1. Introduction. We present in this pape