Investigation of the ignition and combustion of n-heptane-oxygen mixtures

Studies have been made of the ignition of n-heptane/O 2 /Ar mixtures behind incident and reflected shock waves for equivalence ratios of 0.5 to 4.0 in the temperature range 1300–2000 K. Chemiluminescence emission from OH (306.4 nm), CH (431.5 nm) and C 2 (516.5 nm) was monitored together with infra-red emission from CO fundamental (4.8 μm), CO 2 (4.3 μm) or species containing bonded C−H (3.4 μm) and also soot emission (680 nm). The most striking feature shown by the emission profiles was the extent of the preflame activity. The parent fuel was rapidly consumed and carbon monoxide was formed immediately behind the shock front. Information is presented on ignition delay times and times to the point of maximum OH ⊙ emission, although the preflame activity made the former sometimes difficult to identify. A computer model has been developed to explain the main features of combustion including the degradation of the fuel and the soot formation.

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