Development of a reduced n-butanol/biodiesel mechanism for a dual fuel engine

A reduced chemical kinetic mechanism of the n-butanol/biodiesel blend was developed for dual fuel engine simulations. The reaction flow analysis reduction method was adopted to lump and remove the unimportant species and the related reactions. The reduced mechanism of n-butanol contains 71 species and 349 reactions. The reduced mechanism of n-butanol was merged into a reduced mechanism of biodiesel to construct a combined mechanism of n-butanol/biodiesel with 171 species and 765 reactions. The combined mechanism was validated against the n-butanol experimental data including ignition delays in shock tubes and the mole fractions of species in a jet-stirred reactor. The n-butanol/biodiesel mechanism was further validated against the engine experiments fuelled with the n-butanol/biodiesel dual fuel under multiple operating conditions. The predicted pressure and the heat release rate profiles, as well as CO, HC, NOx, and soot emissions under various conditions agreed well with the experimental data. Analysis of the interaction of n-butanol/biodiesel during the ignition process shows that the biodiesel produces OH radicals at the low in-cylinder temperature, and the produced OH radicals are consumed by n-butanol to produce HO2 radicals after a consecutive reaction. HO2 radicals are then transformed to H2O2, which dissociate to OH radicals at higher in-cylinder temperature. OH radicals in turn facilitate further consumption of n-butanol/biodiesel dual fuel. Analysis of the evolution of oxygen contained in the fuel molecules indicates that the O atom in the n-butanol molecule ends up in CH2O, which is turned into CO and the O atoms in the biodiesel may also give rise to CO2 directly. (c) 2015 Elsevier Ltd. All rights reserved.