Abstract
The cellular structure of methane-air lean premixed flames on a flat burner was studied by the planar laser-induced fluorescence (PLIF) of CH radicals and by the time series analysis on light emission for reconstructed attractors. We treated two types of mixtures, i.e. CH_4/Air (Type-1) and CH_4/O_2/CO_2 (Type-2) mixtures. As the equivalence ratio became lower, the cell size and depth increased, which was due to diffusive-thermal instability. In addition, the cell size and depth in Type-2 mixtures were large compared with Type-1 mixtures. To study the characteristics of the unstable behavior of premixed flames, we obtained the reconstructed attractors. The attractors had a doughnut shape, which indicated that the behavior was quasi-periodic. As the equivalence ratio became lower, the attractor became larger and the trajectory became more unstable.
