A wide range kinetic modeling study of PAH formation from liquid transportation fuels combustion

A new detailed chemical kinetic mechanism was herein developed to describe accurately the combustion of liquid transportation fuels (gasoline, jet-A1 and diesel fuel) as well as laboratory fuels (single components) over an extended range of equivalence ratios, temperatures, pressures and dilution levels. This mechanism is able to simultaneously reproduce PAH mole fraction profiles, ignition delay times and flame speeds for a variety of fuels. Three surrogate mixtures of n-decane, iso-octane and n-propylbenzene in different amounts were formulated to represent the above-mentioned commercial fuels based on their derived cetane numbers and threshold sooting indexes. Based on this mechanism, the impacts of fuel composition (ethylene vs. jet-A1 fuel) and reaction progress (height above the burner) on the respective importance of benzene and naphthalene formation pathways were characterized. In addition to HACA mechanism, naphthalene was found to be formed mainly from phenyl+vinylacetylene and benzyl+propargyl pathways for jet A-1 flames. A path involving dibenzofuran oxidation was also found to play a key role in naphthalene production in jet-A1 flame, highlighting the significant contribution of oxygenated compounds to PAH production.