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A skeletal combustion mechanism with 146 species and 652 reactions of methyl decanoate (MD) as a surrogate for biodiesel fuels was developed for compression ignition engine simulations. The skeletal mechanism of MD was derived by reducing the detailed mechanism based on an integrated reduction method that contains directed relation graph method, sensitivity analysis, and reaction path analysis. A reduced polycyclic aromatic hydrocarbon mechanism was merged into the skeletal combustion mechanism of MD to predict the soot emission. The skeletal mechanism was validated against the experimental data of ignition delays in a shock tube, as well as the mole fractions of the reactants and the intermediate species in a jet-stirred reactor. The skeletal mechanism maintains accuracy with its dramatically reduced size, compared with the detailed mechanism that consists of 2878 species and 8555 reactions. The skeletal mechanism was coupled with the KIVA code for 3-D biodiesel combustion simulation. Compared with the soot measurements in an optical constant volume combustion chamber, the simulation results showed similar soot location and occurrence during the combustion. Engine simulations were conducted with the EGR rate ranging from 0 to 65% at intake temperatures of 25 and 50 °C. The predictions profiles of the pressure and the heat release rate for various conditions agreed well with the experimental data. The skeletal mechanism predicted the emissions, including CO, HC, NO x , and soot accurately.

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Summary A comparative study on ignition delay time and combustion characteristics of four typical oxygenated fuel/air mixtures of dimethyl ether (DME), diethyl ether (DEE), ethanol and E92 ethanol gasoline was conducted through the chemical shock tube. The fuel/air mixtures were measured under the ignition temperature of 1100 to 1800 K, initial pressure of 0.3 MPa and the equivalence ratios of 0.5, 1.0 and 1.5. The experimental results show that the ignition delay time of these four oxygenated fuels satisfies the Arrhenius relation. The reaction H + O2 = OH + O has a high sensitivity in four fuel/air mixtures during high‐temperature ignition, which makes the ignition delay lengthen with the increase of the equivalence ratios. By comparing the ignition delay of four fuels, ether fuels have excellent ignition performance and ether functional group has better ignition promotion than hydroxyl group. Moreover, the carbon chain length also significantly promotes the ignition. Due to the accumulation of a large number of active intermediates and free radicals during the long ignition delay time before ignition, the four fuels all have intense deflagration and generate the highest combustion peak pressure at the relatively low ignition temperature (1150‐1300 K). For DME, DEE and ethanol, due to the high content of oxygen in their molecules, the combustion peak pressure and luminous intensity increased with the equivalence ratio, and the combustion is intense after ignition. E92 ethanol gasoline with low oxygen content has a lower combustion peak pressure and a longer combustion duration than the other three fuels, and its highest combustion peak pressure appears in the stoichiometric ratio. The combustion process of E92 ethanol gasoline is more oxygen‐dependent than the other three fuels.