DescriptionThe combustion of hydrocarbon is a main energy resource for transportation. It is easy to start but very hard to understand and simulate. There have been several efforts to build detailed kinetic mechanisms from elementary reactions. Although they are highly accurate and well capture the complicated chemistry of combustion process, it is expensive to model with detailed mechanisms because their size is too large. Furthermore, it is not effective to apply detailed mechanism while there are only some of species and reactions involved in a typical condition. Therefore, a suitable reduced mechanism for such considered condition is a hot requirement. Recently, Petzold et al., and Androulakis suggested an automatic mechanism reduction based on the mathematical programming method. Following their approach, Banerjee et al. applied GA search to generate reduced mechanisms. The fruit of that work is a reduced mechanism library, which can govern combustion of air -- methane mixture with high accuracy. Nevertheless, the GA reduction method is hard to directly apply to the complex chemistry whose solution space is large. It, therefore, needs a first step of reduction, which can condense the search space of complex combustion mechanisms. Androulakis provided a method based on flux analysis to build a reduced mechanism with a suitable cut-off value of element flux accumulation. Although his method is flexible and very fast, the obtained mechanism can contain some species, which can be further eliminated. In this work, the two approaches mentioned above were combined to form a two-step reduction procedure on n-pentane and n-heptane mechanism. The flux analysis reduction was used first to obtain a skeleton reduced mechanism. Then the GA reduction considered the obtained mechanism as a detailed mechanism for parallel GA search. Nine conditions of n-pentane and nine conditions of n-heptane oxidation were investigated. Although the size of the final reduced mechanisms is much smaller than that of detailed mechanisms, they well estimate the oxidation process.