Synergistic Effect of Various Hydrocarbon Fuels Mixing on Soot Formation in Counterflow Diffusion Flames

In order to investigate the effect of fuel mixing on soot formation, methane, ethane, propene, and propane have been mixed in counterflow ethylene diffusion flame with the mixture ratio 5 %. A light extinction/scattering technique has been adopted to measure the volume fraction, number density, and size of soot particles. The experimental results showed that the mixing of ethane, propene and propane in ethylene diffusion flame produces soot more, even though that of methane was decreased the synergistic effect is more significant for ethylene-propane mixtures compare to ethylene-propene mixtures. In particular, the higher soot number density and smaller soot particle size for the mixture flames compared to those for pure ethylene were showed. This result implies that methyle radicals, which can be produced by the thermal decomposition of ethane and propane, plays an important role for soot formation. Numerical simulations showed that calculated C₂H₂ concentrations versus distance from fuel nozzle in mixture flames were lower than those of pure ethylene flameand methyle radicals in the low temperature region for the formation of propargyl are important.