Development and Validation of a Reduced Reaction Mechanism for HCCI Engine Simulations

A reduced chemical reaction mechanism is developed and validated in the present study for multi-dimensional diesel HCCI engine combustion simulations. The motivation for the development of the reduced mechanism is to enhance the computational efficiency of engine stimulations. The new reduced mechanism was generated starting from an existing n-heptane mechanism (40 species and 165 reactions). The procedure of generating the reduced mechanism included: using SENKIN to produce the ignition delay data and solution files, using XSENKPLOT to analyze the base mechanism and to identify important reactions and species, eliminating unimportant species and reactions, formulating the new reduced mechanism, using the new mechanism to generate ignition delay data, and finally adjusting kinetic constants in the new mechanism to improve ignition delay and engine combustion predictions to account for diesel fuel cetane number and composition effects. The new reduced mechanism consists of 29 species and 52 reactions and was validated under both constant-volume and engine conditions. The results show that the new reduced mechanism gives predictions similar to those of a comprehensive mechanism (179 species, 1642 reactions). The CPU time of using the current reduced mechanism is 50-70% of that of using the base mechanism and orders of magnitude less than that of the comprehensive mechanism.