Critical conditions for non-symmetric flame propagation in narrow channels: influence of the flow rate, the thermal expansion, the Lewis number and heat-losses

Abstract

This paper presents a numerical study of the propagation of isobaric premixed flames in narrow channels, focusing primarily on the symmetry of solutions. Because of the complexity of the problem, only few but very important effects such as the thermal expansion, the Lewis number and heat losses are included in the formulation and only a planar channel geometry is investigated. It is demonstrated that symmetric and non-symmetric steady state flames can exist simultaneously, for certain ranges of the parameters. The parametric dependence of the corresponding bifurcation points is also investigated. It is found that both subcritical and supercritical bifurcations are possible for different values of the parameters. The steady-state results are successfully compared with direct time-dependent simulations. These simulations show that, as a general rule, in cases where both types of solutions exist simultaneously, the non-symmetric solutions are stable while the symmetric solutions are unstable.