Construction of combusiton models for rapeseed methyl ester bio-diesel fuel for internal combusiton engine aplications

Artikel i vetenskaplig tidskrift, 2009

Bio-diesel fuels refer to non-petroleum based diesel fuels consisting of long chain alkyl esters produced by transesterifcation of vegetable oils, and proposed to be used (as neat or blended with conventional fuels) in unmodified diesel engines. Currently, there are few papers (see e.g. [1,2]) in which theoretical models for bio-diesel (e.g. RME) combustion simulations were reported. The models, developed in this paper, are modifications of those described in [1]. After the compilation of liquid fuel properties, the existing detailed mechanism of methyl butanoate ester, C5H10O2 [2, 3] oxidation was supplemented by sub-mechanisms for two proposed fuel constituent components, C7H16 and C7H8O (and, then, by mp2d and propyne, C3H4) to represent the combustion model of RME described by the chemical formula, C19H34O2 (or C19H36O2). The main fuel vapor thermal properties were taken as those of methyl palmitate C19H36O2 in the NASA polynomial form of the Burcat [4] database. The special global reaction was introduced to “crack” the main fuel into constituent components, which sub-mechanisms were collected in the general (309 species, 1472 reactions) including also soot and NOx formation processes. The detailed combustion mechanism was validated using shock-tube ignition-delay data at diesel engine conditions. For constant volume and diesel engine (Volvo D12C) combustion modeling, this mechanism was reduced to 88 species participating in 363 reactions.