A TRF–iso–Butanol kinetic mechanism for the prediction of pollutant with validation against novel rich atmospheric flame experiments
Abstract
Light-duty vehicles are increasingly powered by direct-injection gasoline engines, which reduce fuel consumption. However, this type of engine leads to the formation of liquid films of fuel at the wall of the combustion chamber, which then burn in fuel-rich flames, producing nano soot. This issue is a topic of focus in the combustion research community, especially for blends of gasoline with new alcohol biofuels, e.g. iso-butanol. To model these phenomena, a high-temperature combustion model of a toluene reference fuel (TRF) blended with iso-butanol (B) has been developed as a surrogate of a gasoline. The new TRF-B model was built by comparing the performance of recent mechanisms for reproducing a very large number of auto-ignition delay times and experimental speciations for pure fuels and binary and ternary mixtures. The performance and size of mechanisms in the literature led to the final model being built by merging TRF and alkylbenzene mechanisms from LLNL with a sub-mechanism for iso-butanol from MIT. The model was validated by the simulation of the structure of a new premixed laminar flame of the TRF-B blend, which is a surrogate of a RON 95 gasoline, under atmospheric pressure and fuel-rich conditions (Φ=1.72). Reactants, products and numerous intermediates sampled by microprobe were quantified by on-line gas chromatography. Temperature profiles were obtained by thermocouple and NO-LIF thermometry. The main products of the oxidation of each of the reactants are well reproduced by the model, such as propene, iso-butene and benzene, as well as oxygenate compounds characteristic of iso-butanol oxidation such as propanal. The model reproduces well the formation of unsaturated soot-precursors and will be extended to the formation of heavier PAHs.