Abstract:

The detailed chemical kinetic mechanism for high-temperature combustion of methyl heptanoate was systematically reduced via integrated mechanism reduction methods. The skeletal mechanism including 108 species and 547 elementary reactions was derived via two-step directed relation graph method(DRG) combined with the principle component analysis(PCA) method from the detailed mechanism consisting of 1087 species and 4592 elementary reactions. The skeletal mechanism was further reduced through time-scale analysis. The computational singular perturbation method(CSP) was used for the selection of quasi-steady state(QSS) species, and 30 species were chosen as good candidates for QSS species. Finally, based on the quasi-steady state approximation(QSSA) method, a reduced mechanism including 78 species and 74 global reactions was obtained. Both the skeletal mechanism and the 78 species reduced mechanism could reproduce combustion characteristics of the detailed mechanism such as the ignition delay, extinction, and distribution of species concentration over a wide range of simulation conditions. Furthermore, based on the skeletal mechanism, reaction path and elementary reactions which are important for high temperature combustion of methyl heptanoate were clarified. Compared with the detailed mechanism, the skeletal mechanism is able to provide a reliable description on high temperature combustion characteristics of methyl heptanoate, which could be helpful in understanding the combustion process of biodiesel.

Key words: Methyl heptanoate, Mechanism reduction, Directed relation graph, Principle component analysis, Computational singular perturbation method, Quasi steady state approximation