Optimization of a 5-step kinetic scheme for HCCI applications

In this paper a reduced kinetic scheme adapted and optimized for HCCI applications is presented. This kinetic scheme uses three reactions for the low temperature oxidation and two reactions for the high temperature oxidation. In this work, the 5-step kinetic scheme is optimized using a genetic algorithm for two different sets of HCCI conditions: a near stoichiometric combustion with a high amount of exhaust gas recirculation and a lean combustion with no exhaust gas recirculation. The merit function used to perform the optimization is based on the comparison of the ignition delay calculated with the reduced scheme and a detailed kinetic scheme of reference. In this study, twelve parameters of the 5-step kinetic scheme are optimized for the two sets of HCCI conditions chosen. Finally, the reduced kinetic scheme is implemented in the 3D code FIREV8 and a fairly good agreement is obtained with experimental HCCI results. These results were found to be very promising for the future use of this 5-step kinetic model in a 3D code to study easily a large number of HCCI engine parameters.