An Upgraded Chemical Kinetic Mechanism for Iso-Octane Oxidation: Prediction of Polyaromatics Formation in Laminar Counterflow Diffusion Flames

Iso-octane is widely recognized as a prominent candidate to represent the oxidation of iso-alkanes within jet fuel and gasoline surrogates. This work evaluated a chemical kinetic mechanism for iso-octane focusing on the model's capability to predict the formation of polycyclic aromatic hydrocarbons (PAHs). As the model is intended to be further coupled with soot models, the chemical kinetic mechanism must supply good predictability of the formation and consumption of PAHs considered as major soot precursors. A first validation of the iso-octane submodel as incorporated within ESTiMatE-Mech, using experimental data from literature, reveals the need to improve the submodel. Considerable deviations were observed in the prediction of the PAHs, although concentration profiles of major species and fundamental combustion properties, here ignition delay time and laminar flame speed, were accurately predicted. Through rate of production and sensitivity analyses of the mechanism, nine reactions were identified to have a strong impact on the (over) prediction of the PAHs. These reactions have been modified based on information gathered from literature resulting in an updated version of the mechanism called ESTiMatE-Mech_mod. Simulation results with this modified mechanism showed that this updated mechanism is now capable of predicting well the targeted PAHs, while retaining the good initial prediction of the major species concentration profiles as well as of laminar flame speeds and ignition delay times.