Suppression Effects of Stretching Flow on Soot Emission from Laminar Diffusion Flames

The comparison of soot limits of axisymmetrical laminar diffusion flames stabilized in two different flow fields, i.e., stretching and non-stretching (parallel) flow, revealed that soot emission is suppressed more effectively in the former flow. From the experimental results that flame heights were hardly affected by the flow field difference, it was inferred that such an effect of the stretching flow is attributed to the flow acceleration which leads to the shortening of fuel residence time in the soot-forming region and, therefore, to the effective suppression of soot particle growth. Burner scale effects on the soot suppression were also investigated using the stretching flow burners of several sizes and some empirical relations at the soot limit were derived among burner size, air flow rate (stretch rate), and fuel flow rate.