Abstract
This work examines the autoignition chemistry of fuel-lean n-heptane oxidizer mixtures. A Rapid Compression Expansion Machine (RCEM) was used to obtain both ignition delay times and study the stable intermediate species time evolution during the induction period. Ignition delay times for premixed fuel-oxidizer mixtures were obtained for compressed pressures between 3.0–5.5 bar and equivalence ratios (ϕ) between 0.20 and 0.50. The compressed temperatures were in the range of 592–763 K and included the onset of the negative temperature coefficient behavior for n-heptane under these test conditions. Trends for both the first-stage and overall ignition delay times as a function of temperature were obtained.Additionally, the identification and quantitation of pre-ignition stable intermediaries were conducted. This was accomplished by rapid quenching of the reactions after the first-stage ignition phase in controlled time increments. A gas chromatograph-mass spectrometer system was used for the identification and quantification of stable intermediates. This work provides fundamental insights into the low-to-intermediate temperature oxidation kinetics of n-heptane using a new generation of electrically actuated and computer programmable RCEM.