Analysis of Important Chemical Pathways of n-Heptane Combustion in Small Skeletal Mechanisms

Reduced mechanisms for n-heptane combustion have been constructed using the novel ACR method, with the complex mechanism from CRECK, including low-temperature chemistry, as a starting point. Tailored mechanisms for each part of the combustion process, ignition, flame propagation, and extinction, were created to identify differences and common trends in mechanism composition. The simulations were carried out for n-heptane/air mixtures for zero-dimensional homogenous reactors, one-dimensional freely propagating flames, and counter-flow diffusion flames at temperature, pressure, and equivalence ratio conditions relevant to engine combustion. The smallest mechanism, 28 species, only targets laminar burning velocity, while the largest single-property mechanism is for ignition over a wide temperature range, with 48 species. A compound mechanism covering all conditions consists of 65 species, this mechanism includes reaction paths describing important subchemistries like the peroxyl radical chemistry governing low-temperature ignition and the C/H/O chemistry of importance to flame propagation. Compared to the CRECK mechanism, all the reduced mechanisms have fewer than 2% of the number of reactions.