Upstream interactions between planar symmetric laminar methane premixed flames

Unsteady upstream interactive combustion of two stoichiometric planar methane premixed flames that propagate towards each other as they consume the finite slab of combustible gas in between them is numerically investigated. The onset of hydrodynamic, thermal, and diffusional interactions between the merging flames that is governed by the relative magnitude of the diffusivity for momentum, heat, and mass are discussed in terms of the dimensionless groups Prandtl, Lewis, and Schmidt numbers. The average propagation velocity of laminar methane flames is found to first increase from 40.5 to 41.9 cm/s during their thermodiffusive interactions and subsequently to 282 cm/s during the chemical interactions associated with the merging of the reaction zones. The influence of the Lewis number of the fuel and the oxidizer on the nature of upstream flame-flame interactions is determined. The results show that under appropriate values of the transport coefficients the sharing of reactive radical species may lead into local homogeneous explosion of the reactive mixture.