Chemical and Physical Properties of Soot as a Function of Fuel Molecular Structure in a Swirl-Stabilized Combustor

Soot samples were extracted from a swirl-stabilized, liquid-fuel fired laboratory combustor to (i) assess the validity of the ASTM smoke point test in predicting the sooting characteristics of fuels in complex combustion systems and (ii) assess the effect of fuel molecular structure and smoke suppressant additives on the physical and chemical properties of soot. Fuels utilized were shale JP-8, iso-octane, and blends of iso-octane with either decalin, toluene, tetralin, or 1-methylnaphthalene such that smoke points similar to JP-8 were achieved. Each fuel was separately blended with 0.05 percent (by weight) ferrocene smoke suppressant. The results indicate that the ASTM test can be misleading, increased fuel molecular complexity increases soot content of higher molecular weight polycyclic aromatics, and ferrocene additive reduces small particle number density but not necessarily the soot mass loading.