Sooting limit of various gaseous hydrocarbon fuels in counterflow diffusion flames

Sooting limit in counterflow diffusion flames, defined as the critical fuel and oxygen mole fractions at which soot starts to appear, were measured for various gaseous hydrocarbons using an elastic light scattering technique. The effects of dilution and strain rate were also examined. Maximum flame temperatures at the measured sooting limits were calculated using detailed chemical mechanisms to help interpret experimental results. Appreciable difference was observed between soot formation (SF) and soot formation oxidation (SFO) flames. In SF flames, for a specified fuel maximum flame temperature at sooting limits seems to be constant over a wide dilution levels indicating the existence of limiting temperature for soot to form, which depended on fuel type and strain rate. In SFO flames, critical oxygen concentration was shown to exhibit an Arrehnius relationship with flame temperature for all the fuels tested. Increase in strain rate was shown in general to decrease the sooting tendency of fuel and its sensitivity to strain rate varies with fuel type.