Fuel-rich oxidation of gasoline surrogate components in an atmospheric flow reactor

Fuel-rich oxidation of three typical gasoline surrogate components, toluene, isooctane, and n-heptane, was investigated in an atmospheric-pressure flow reactor at mean gas temperatures from 1050 to 1350 K, equivalence ratio of 9.0, and residence times of 0.45 and 1.2 s. Not only polycyclic aromatic hydrocarbons (PAHs) up to 3 ring structure but also small intermediate products from C 1 to C 5 were quantified by a gas chromatograph mass spectrometry coupled with photon ionization and gas chromatograph with flame ionization detector, respectively. The kinetic model recently developed by Lawrence Livermore Na-tional Laboratory was revised to reflect the results of many recent investigations. Basically, the updated model could satisfactorily reproduce the experimental mole fractions of many species. The experimental and simulated results showed that PAH mole fractions produced were in the order of toluene, isooctane, and n-heptane. The kinetic analysis using the model was carried out to explore PAH formation pathways, especially focusing on naphthalene, acenaphthylene, and phenanthrene. Through rate of production anal-ysis, it was found that the main formation pathways of many PAHs were affected by the fuels. Although resonantly stabilized radicals, such as benzyl and fulvenallenyl radicals, played a crucial role in the forma-tion pathways of many PAHs in every fuel, they were produced through hydrogen elimination of toluene in toluene fuel, while they were formed from small intermediate products in isooctane and n-heptane fuels. Sensitivity analysis revealed the difference and similarity of the reactions with large positive coeffi-cients according to the fuels studied here. The molecular growth reactions of aromatic species were influ-ential in PAH production in every fuel, whereas the ring formation reactions from small species and the reactions involving toluene had large positive sensitivity coefficients in isooctane/n-heptane and toluene fuels, respectively.(c) 2023 The Combustion Institute. Published by Elsevier Inc. All rights reserved.