Calculation of extinction limits for premixed laminar flames in a stagnation point flow

Abstract

Conclusions derived from the solution of premixed laminar flames in a stagnation point flow are important in the study of pollutant formation, the determination of chemically controlled extinction limits and in the ability to characterize the combustion processes occurring in turbulent flames. In the neighborhood of the stagnation point produced in these flames, a chemically reacting boundary layer is established. For a given equivalence ratio, the input flow velocity can be varied and solutions can be determined for increasing values of the strain rate. As the strain rate increases, the flame nears extinction. In the vicinity of the extinction point, however, the Jacobian of the system becomes singular. To avoid computational difficulties, we employ numerical bifurcation techniques to generate the approriate steady-state profiles (both physical and nonphysical). The method is applied to study the extinction behavior of a one-step kinetics model of a premixed hydrogen-air and methane-air flame in a counterflow geometry.