Lean flame dynamics through a 2D lattice of alkane droplets in air

Flame propagation along a 1-D array or through a 2D-lattice of fuel droplets has long been suggested to schematize spray-flames spreading in a two-phase premixture. The present numerical work considers the fresh aerosol as a system of individual alkane droplets initially located at the nodes of a face-centred 2D-lattice, surrounded by a variable mixture of alkane and air, in which the droplets can move. The main parameters of the study are s , the lattice path and L φ , the liquid loading, which are both varied, whereas T φ , the overall equivalence ratio, is maintained lean ( 85 . 0 = T φ ). Main results are: a) for large lattice path (or when the droplets are large enough), spreading occurs as resulting from two stages : a short time of combustion followed by a long time lag of vaporization; a classical triple flame (with a very short rich wing) spreads around the droplets; b) spray-flame speed decreases as liquid loading increases; c) an elementary model invoking both propagation stages allows us to interpret flame speed as a function of the sole parameter L s φ × ; d) when the lattice path shortens, the spray-flame exhibits a pattern that continuously goes from this situation to the plane flame front;