Concerning the Luminosity of Methanol-Hydrocarbon Diffusion Flames

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Abstract
Luminosity of methanol-hydrocarbon diffusion flames was studied as a function of liquid fuel composition. Wick flames were used. Fuel compositions producing low-luminosity and high-luminosity flames are separated by a concentration threshold whose location varies among different hydrocarbon cofuels. Cofuels that burn individually to form large amounts of soot, e.g., xylene, exhibit lower thresholds than confuels that burn forming little soot, e.g., n-hexanol. Luminosity studies of small pool fires were performed. Distillation effects are severe. With solutions of low-boiling hydrocarbons in methanol the hydrocarbons are selectively vaporized out of pool liquid, and burned, during early stages of the pool fire. This produces high initial flame luminosity which later decreases as the residual pool liuqid is enriched in methanol. In contrast, selective methanol vaporization occurs during pool fires involving methanol solutions of high-boiling hydrocarbons; e.g., xylene. Here initial flame luminosity, dominated by methanol vapor, is low. Later stages of these pool fires, governed by residual hydrocarbon, exhibit high luminosity. Infrared imaging was used to study radiation from burning methanol, hydrocarbons, and methanol-hydrocarbon solutions. This method provides a rapid, efficient means of detecting methanol flames under conditions where they are virutally imperceptible to visible light monitoring systems. The total radiation flux (infrared plus visible) from burning methanol was found to be six times less than the flux from burning hydrocarbons.

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