S P O N T A N E O U S ignition properties of combustible materials, particularly fuels and hydrocarbons, have been an important area of combustion research for over 50 years. This interest in spontaneous ignition is based on the important role which this phenomenon plays in the fire hazard in the handling and storage of combustibles, the performance of various types of combustion engines, and the elucidation of oxidation and combustion mechanisms of fuels, hydrocarbons, and related substances.The spontaneous ignition temperature (SIT) of a substance is defined as that lowest temperature a t which the substance will ignite in air without the aid of a spark or flame. Based on the thermal theory of ignition and on classical reaction-rate theory, spontaneous ignition temperature can be regarded as that temperature to which a combustible mixture must be raised so that the rate of heat evolved by the exothermic oxidation reactions of the system will just overbalance the rate a t which heat is lost to the surroundings. However, the criterion that is usually taken to indicate ignition-i.e., visible and/or audible combustion observed under ordinary laboratory conditions-is quite subjective. Also, the spontaneous ignition temperature of a substance should be a quantity related to some characteristic chemical property of the material, yet its experimentally determined value is markedly dependent on the method and apparatus employed for its determination. I n a recent monograph, Mullins (1 7) reviews this subject, including the importance, definition, and meaning of spontaneous ignition and spontaneous ignition temperature and describes numerous methods for its determination and the factors which influence results.Earlier work on the effects of oxygen concentration ( 2 , 12-14) indicated that it would be of interest to study spontaneous ignition in finer detail using better instrumentation with particular emphasis on preignition behavior. A static system was chosen for its simplicity and to make temperature-time measurements. An inherent fault of such a system is the problem of uniform gas mixing after introducing the hydrocarbon sample. This problem should be minimized by discharging the sample as a fine spray and by a long time delay before ignition occurs.The general purpose of this investigation was to study the influence of chemical structure on the spontaneous ignition processes. Specifically, the influence of chain length, chain branching, unsaturation, and of cyclic and aromatic structures on the preignition processes was examined by measuring internal gas temperature and oxygen consumption.I n addition to minimum ignition temperature in air for cool-or hot-flame ignition, minimum reaction temperature, preignition temperature range, temperature rise, and oxygen consumption a t ignition were useful. A correlation between these values and ease of oxidation and ignition was noted. The findings were as follows: I n general, decreasing chain length, addition of methyl groups, unsaturation, and particularly, chain branchin...

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Fire safety of Navy ships is a matter of continuing concern. The practice in land—based buildings and commercial ships experiencing a serious fire accident is often to abandon the building or ship. For Navy warships in combat, however, it is imperative that the ship's crew be able to control an on—board fire and retain the ship's combat effectiveness. The need for effective and rapid fire—fighting capability aboard naval ships is further dictated by the increased potential of fire hazards characteristic of a warship, such as the high density of fuel and ammunition stores aboard ship, refueling and replenishment at sea, and possible hostile enemy action. Fire casualties aboard Navy ships are briefly reviewed, with emphasis on recent lessons learned in control of fires and fire hazards. Also reviewed are ongoing and planned actions to upgrade fire protection in the ship design process and in the Fleet. Based on these lessons learned, the Navy is initiating a “total systems approach” to shipboard fire safety, and is reorienting R&D thrusts accordingly. The scope of the Navy's ongoing research and development program is reviewed, with a description of selected hardware/software obtained to date from this program for improvements to Fleet fire—fighting and personnel—survival equipment. Finally, the future trends of research and development needs are discussed and projected research program directions indicated.

Various nonequilibrium combustion conditions are examined and evaluated regarding their effect on safety. Tank flammability limits are indicated to depend on the ratio of empty to liquid volume when fuels of different “light ends” content are used. Altitude effects and mist ignitability are discussed as is the effect of volatility on fire spread above a fuel pool. Because information is only available for Jet A and Jet B type fuels, the author offers his estimate of the effect of kerosine flash point reduction on the various properties of importance. If the use of such fuels is to be considered, performance data should be obtained to assess the impact of flash reduction on fuel handling and performance safety.

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