IGNITION CHARACTERISTICS OF FUELS AND LUBRICANTS

Hot surface ignition temperature data are presented for n-hexane, n-octane, n-decane, JP-6 jet fuel and aircraft engine oils MIL-L-7808 (0-60-18) and H-1026 in various oxygen-nitrogen atmospheres (2.5 to 100 volume percent oxygen) under stagnant or near-stagnant flow conditions. Minimum ignition temperatures were found to increase with decreasing oxygen concentration. In vessel ignitions, these temperatures increased with decrease in fuel contact time and with increase in surface area/volume ratio. In wire ignitions, the minimum ignition temperatures increased with decrease in wire diameter, length/diameter ratio, and initial mixture temperature. Expressions were developed to define the ignition temperatures as a function of the above pertinent variables. Hot gas ignition temperatures of the above combustibles were also found to vary with the heat source diameter, for 1/8, 3/8 and 1/2-inch diameter jets. In oxidation studies with n-octane vapor air-mixtures, rates of pressure rise were found to vary as the 0.38 power of the fuel concentration (5 to 30 volume percent) and as the 1.4 power of the initial total pressure (0.6 to 13 psia) at temperatures between 428 and 536F. (Author) See also AD-600 002.