Spontaneous Ignition Temperature of Liquid Hydrocarbons at Atmospheric Pressure - Effect of Concentration of Fuel Vapor and Oxygen: Fuel Ratio

Ignition Regions of Hydrocarbons.

“…There have been, however, certain practical difficulties to an unqualified acceptance of this relationship; also, although it was early recognized that a limit was set to engine design by critical compression ratios depending on the fuel employed, the part played by pressure other than by raising the working temperature remained obscure, there being no reason to suppose that its influence on ignition points was abnormally great and other than quite progressive. When it was discovered with the higher paraffins that (1) the lower ignition region approximated to the ordinary compression temperatures attained in an engine, (8) ignition occurred abruptly in this region with a minimum time-lag on the attainment of a critical pressure, while at higher temperatures the mixtures were non-ignitible, (3) mixtures rich in combustible ignited at a lower critical pressure than those containing excess of air, (4) not only did ignition occur at progressively lower pressures as the series was ascended but the time-lags were also materially reduced, and (5) the presence of an antiknock raised the pressure necessary for ignition, it became clear that it was to the pressure requisite for ignition in the lower range that the standard knock ratings of fuels were probably related.…”

“…Systematic work on the influence of reaction temperature on the slow combustion of the higher paraffins, etc., in admixture with air was first published in 1929 by Pope, Dykstra, and Edgar (27,2,8) who, working in a flow system, established that, although initial oxidation commenced at 150-200°C., becoming active between 250°C. and 270°C.…”