Investigation on cellular instabilities of CH₄/H₂/CO₂/O₂ flat flames

The cellular structure of CH₄/H₂/CO₂/O₂ flames on a McKenna flat burner was observed and measured using OH-PLIF techniques. The cellular flame due to intrinsic instability emerged near the lean combustion limit, while the number of cells increased with the increase of equivalence ratio and/or the hydrogen fraction. The quantitative parameters of cellular flame front structure were statically calculated to represent the degree of irregularity, and we found that when the average stand-off distance decreased, the flame tended to be smooth, which attributed to the heat loss to burner surface. Through linear stability analysis, the R-S model were proved to be a good one to predict the variation tendency of instability versus equivalence ratio, but failed to the effect of hydrogen addition. The suppression of the burner surface should not be ignored.