MODELING CONCEPTS FOR LARGER CARRON NUMRER ALKANES: A PARTIALLY REDUCED SKELETAL MECHANISM FOR n-DECANE OXIDATION AND PYROLYSIS

摘要

A new, partially reduced skeletal chemical kinetic mechanism for the oxidation and pyrolysis of n-decane was developed. This mechanism was validated against newly obtained n-decane flow reactor data. The proposed model was also compared against n-decane oxidation jet-stirred reactor data and n-decane/air shock tube ignition delay data obtained from the literature. The mechanism is an extension of a similar mechanism developed for n-heptane recently published by this laboratory. The current conceptual approach differs from that in our previous modeling of n-heptane oxidation in that it includes detailed chemistry of n-decane and the five n-decyl radicals, and it incorporates both internal hydrogen isomeri-zation reactions and β-scission pathways for the various system radicals. To include this additional detailed reaction information and simultaneously minimize the number of species present in the model, an important assumption was made regarding the distribution of radical isomers. It was assumed that the different isomers of a given alkyl radical are in equilibrium at each carbon number above the C_4 level, thereby allowing the inclusion of the reaction channels associated with each isomer, without imposing the computational penalty associated with including each isomer as a separate species in the mechanism. As a result, only a single radical is needed to represent all the isomers associated with it. Thus, the new mechanism contains detailed reaction chemistry information, while maintaining the compactness necessary for use in combined fluid mechanical/chemical kinetic computational simulations. In addition to verifying this approach for n-decane, the approach was shown to be compatible with the modeling of n-heptane. The hierarchical nature of this modeling technique should prove amenable for use in developing compact mechanisms for other large n-alkanes, and this partially reduced skeletal model can serve as a validated starting model for developing more compact representations.