Development of an optimized chemical kinetic mechanism for homogeneous charge compression ignition combustion of a fuel blend of n-heptane and natural gas using a genetic algorithm

Homogeneous charge compression ignition (HCCI) is a promising technique for advanced low-temperature combustion strategies that offers a high fuel conversion efficiency and low nitrogen oxide and soot emissions. One of the major problems associated with HCCI combustion engine application is the lack of direct control for combustion timing. A proposed solution for combustion timing control is to use a binary fuel blend in which two fuels with different autoignition characteristics are blended at various ratios on a cycle-by-cycle basis. Because dual-fuel diesel-natural-gas engines have already been used, a fuel blend of n-heptane (diesel-like fuel) and natural gas (mostly methane) is one of the best available options. The objective of this study is to optimize the chemical kinetic mechanisms available for n-heptane and natural gas to be used in a binary-fuel blend scenario. Using the genetic algorithm method, a combined mechanism was optimized and modelling results were verified against experimental results. The agreement between experimental and modelling results was found to be acceptable within the examined conditions. As a result, an optimized chemical kinetic mechanism for an n-heptane-natural-gas blend is presented.