High-pressure reduced-kinetics mechanism for n-hexadecane autoignition and oxidation at constant pressure

Abstract

In previous work, a local full self similarity (LFS2) was identified between (properly) normalized thermo-kinetic quantities when plotted against a normalized temperature. The local partial self similarity (LPS2), which is the computationally efficient companion of LFS2, was coupled with a simple tabulation scheme and yielded highly-accurate twenty-light-species reduced mechanisms for constant-mass and constant-volume autoignition and oxidation of n-heptane, n-decane, n-dodecane and iso-octane. The LFS2 and LPS2 reduction framework coupled with tabulation were combined into a method here called Local Self Similarity Tabulation (LS2T). The LS2T method is here extended and validated for constructing reduced kinetics mechanisms for the constant-mass autoignition and oxidation of an even heavier hydrocarbon, n-hexadecane, but now at constant pressure conditions for a wide range of initial conditions. The method employs the same twenty light species as species progress variables as in the lighter alkanes previously studied, and tabulates through the LPS2 all information involving any heavy species. The template mechanism used for reduction is the detailed 2115-species kinetics from the Lawrence Livermore National Laboratory. Results are presented for the n-hexadecane autoignition and oxidation at the high pressures encountered during engine operation and for several initial temperatures and equivalence ratios. We show that the utilization of a real-gas equation of state (the Peng–Robinson equation of state with a volume correction) is essential in obtaining accurate results. Reduced-kinetics plots of the temperature and the major species, including the OH temporal evolution, computed with the LS2T method accurately duplicated those obtained with the LLNL detailed mechanism.