A Skeletal Mechanism of a Biodiesel Surrogate Fuel for Compression Ignition Engines

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.