Multiple speeds of flame edge propagation for Lewis numbers above one

Edges of diffusion flames in a counterflow burner are examined numerically for Lewis numbers greater than unity. When the speed of propagation is plotted against Damköhler number for a range of Lewis numbers a fold bifurcation is observed. It is shown that there exist stable positively and negatively propagating edges for some Damköhler number and Lewis number pairs. It is further shown that changed local conditions can lead to a transition from positive (advancing into the unburnt gasses) to negative (receding) propagation. © 2005 Taylor & Francis.