Characteristics of non-premixed edge flames in a slot-jet counterflow

The propagation rates of advancing and retreating nonpremixed edge flames in a slot-jet counterflow were measured as a function strain rate for varying jet spacing, mixture strength, and stoichiometric mixture fractions (Z _st). Methane was tested and nitrogen was used as an inert. As results, we could identify igniting fronts, retreating fronts, two total extinction limits, and short-length edge flames. A burner separation affected to a low extinction limit only, and for CH₄/O₂/N₂ mixtures, regimes for advancing and retreating edges together with total extinction was mapped in terms of normalized flame thickness and heat loss factor. Edge flames for Z_st > 0.5 behaved like a stronger mixture while for Z_st < 0.5 showed deteriorated feature, because of relative locations of a nonpremixed flame and intermediate species such as CO and H₂.