Development of an iso-Octane Skeletal Combustion Mechanism based on Primary Sensitive Reactions

In this study, an iso-octane skeletal combustion mechanism was constructed based on the sensitivity and reaction path analysis of the most recent published detailed iso-octane combustion mechanism. The major reactions relevant to the fuel consumption were determined based on sensitivity analysis at 650, 750 and 850 K under pressure of 20 bar for stoichiometric iso-octane/air mixture. Additional reactions were added to balance the reaction species. In particular, two lumped octyl radicals were used to describe the H atom abstraction products of iso-octane due to their distinctly opposite sensitivities on the fuel reactivity. In addition, major reaction equations for the description of fuel molecule consumption were kept as the same as those in the detailed mechanism for the purpose of traceability. The reaction rate constants of most reactions were taken from the detailed mechanism, and were kept unchanged except for a few reactions, of which the reaction rate constants were slightly adjusted. Finally, a slightly modified reduced base reaction mechanism was added to the mechanism to formulate the final iso-octane skeletal mechanism. The iso-octane skeletal mechanism was validated with ignition delay experimental data over various engine relevant conditions, and reasonable agreement was obtained. In addition, the major sensitive reactions that control the fuel reactivity in the iso-octane skeletal mechanism proposed in this study were similar to those in the detailed mechanism.