Modeling combustion chemistry using C3MechV4.0: An extension to mixtures of hydrogen, ammonia, alkanes, and cycloalkanes

The design of novel renewable fuel mixtures (such as hydrogen, ammonia, methanol, ethanol, and other blends) compatible with existing engine infrastructure can be greatly aided by accurate kinetic modeling of fuel surrogate mixtures. With this objective, a robust kinetic model should accurately describe the kinetics of the pure components and their mixtures at engine-relevant conditions. This work presents the results of the continued work of the Computational Chemistry Consortium (C3) to build a “universal” chemical kinetic mechanism to describe the oxidation of fuel surrogate mixtures. Our previous model, C3MechV3.3, focused on conventional fuel mixtures, i.e., the ignition behavior of $n$-alkanes up to C₁₂, as well as pollutant formation, including polycyclic aromatic hydrocarbons (PAHs) and nitrogen oxides (NO${}_x$). To meet the needs of fast renewable fuel mixture screening, the updated model, C3MechV4.0, now also includes the combustion of carbon-free fuels, including hydrogen and ammonia; dimethyl carbonate, and ethylene carbonate, which are useful to investigate battery fires in hybrid vehicles; cyclopentane, cyclohexane, and xylene, which enrich the palette of useful conventional fuel surrogate components. Each kinetic subset was updated according to the most recent literature findings and, if needed, tuned to improve the prediction of experimental target data. The model was tested against a wide range of experimental data (some of which is new) for fuel mixtures, focusing on hydrogen, methane, and ammonia, proving the model’s predictive capabilities. A hierarchical and modular mechanism structure was enforced, enabling the automatic assembly of smaller subsets of mechanisms, which can accelerate kinetic simulations of fuel mixtures.