A rapid compression machine investigation of oxidation and auto-ignition of n-Heptane: Measurements and modeling

n-Heptane oxidation and auto-ignition in a rapid compression machine is studied in the low and intermediate temperature regimes at high pressures. Experimental ignition delay times and some phenomenological aspects related to knock in engines are presented, providing additional information at lower temperatures on previously published delays from shock tube experiments. The products of oxidation are identified and time profiles are measured during a two-stage ignition process. Eight C7 heterocycles, heptenes, lower 1-alkenes, aldehydes, and carbon monoxide are the main species. Their origin is discussed in relation to the isomerization and decomposition of heptylperoxy radicals. The high selectivity observed in the formation of lower 1-alkenes is explained by the scission of the β C---C bond of the β-hydroperoxyheptyl radicals weakened by the presence of oxygen atoms. Numerical simulation of the experiments with Warnatzʹs comprehensive chemical mechanism gives satisfactory results for cool flame and total ignition delays, but fails to reproduce the detailed chemistry before auto-ignition.