FLAME SPREAD IN LAMINAR MIXING LAYERS - THE TRIPLE FLAME

In the present paper we investigate flame spread in laminar mixing lay ers both experimentally and numerically. First, a burner has been desi gned and built such that stationary triple flames can be stabilised in a coflowing stream with well defined linear concentration gradients a nd well defined uniform flow velocity at the inlet to the combustion c hamber. The burner itself as well as first experimental results obtain ed with it are presented. Second, a theoretical model is formulated fo r analysis of triple flames in a strained mixing layer generated by di recting a fuel stream and an oxidizer stream towards each other. Here attention is focused on the stagnation region where by means of a simi larity formulation the three-dimensional flow can be described by only two spatial coordinates. To solve the governing equations for the lim iting case in which a thermal-diffusional model results, a numerical s olution procedure based on self-adaptive mesh refinement is developed. For the thermal-diffusional model, the structure of the triple flame and its propagation velocity are obtained by solving numerically the g overning similarity equations for a wide range of strain rates.