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

Abstract

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 sub-model as incorporated within ESTiMatE-Mech, using experimental data from literature, reveals the need to improve the sub-model. Considerable deviations were observed in the prediction of the PAHs, although concentration profiles of major species and fundamental combustion properties such as 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 influence in 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.

Large Eddy Simulation of Soot Formation in a Real Aero-Engine Combustor Using Tabulated Chemistry and a Quadrature-Based Method of Moments

“…The kerosene fuel (Jet-A1) is represented by a surrogate consisting of 52 vol-% dodecane (C 12 H 26 ), 15.8 vol-% iso-octane (C 8 H 18 ), 12.1 vol-% cyclohexane (C 6 H 12 ), and 20.1 vol-% trimethylbenzene (C 9 H 12 ). The chemical kinetics are modeled with a recently developed mechanism for kerosene surrogates specialized for soot formation [38,39], which is based on a multicomponent reaction mechanism [40]. Subsequently, the calculated flamelets are parameterized by the mixture fraction 𝑍 and the progress variable 𝑌 𝐶 and stored in a manifold.…”