Construction of combustion models for rapeseed methyl ester bio-diesel fuel for internal combustion engine applications

Abstract

Bio-diesel fuels are non-petroleum-based diesel fuels consisting of long chain alkyl esters produced by the transesterification of vegetable oils, that are intended for use (neat or blended with conventional fuels) in unmodified diesel engines. There have been few reports of studies proposing theoretical models for bio-diesel combustion simulations. In this study, we developed combustion models based on ones developed previously. We compiled the liquid fuel properties, and the existing detailed mechanism of methyl butanoate ester (MB, C 5H 10O 2) oxidation was supplemented by sub-mechanisms for two proposed fuel constituent components, C 7H 16 and C 7H 8O (and then, by mp2d, C 4H 6O 2 and propyne, C 3H 4) to represent the combustion model for rapeseed methyl ester described by the chemical formula, C 19H 34O 2 (or C 19H 36O 2). The main fuel vapor thermal properties were taken as those of methyl palmitate C 19H 36O 2 in the NASA polynomial form of the Burcat database. The special global reaction was introduced to “crack” the main fuel into its constituent components. This general reaction included 309 species and 1472 reactions, including soot and NO x formation processes. The detailed combustion mechanism was validated using shock-tube ignition-delay data under diesel engine conditions. For constant volume and diesel engine (Volvo D12C) combustion modeling, this mechanism could be reduced to 88 species participating in 363 reactions.