The spontaneous combustion of n-heptane

Abstract

The spontaneous combustion of n -heptane has been studied in a static system between 240 and 428°C. During reaction the changes in both pressure and temperature were followed; the latter proved the more useful method of discriminating between the various modes of combustion. The slow combustion-cool flame and cool flame/two-stage ignition boundaries have been determined in both pyrex and stainless steel vessels for several heptane/oxygen mixtures covering a wide range of composition, and the effect of various inert diluents has also been studied. Chemical analyses were performed at selected stages of the reaction, and these results together with the pressure and temperature measurements show that the slow combustion and cool flame reactions are very similar chemically. Likewise, the first stage of a two-stage ignition is identical with a cool flame, while the second stage is a quite distinct event. In very fuel-rich mixtures true two-stage ignition was not observed, while in stainless steel vessels no multiple cool flames were detected under any of the conditions studied.