Comparisons of Completeness of Combustion for Alcohol and Alkane Laminar Wall Fires

Steady, fully burning wall fires were studied using alkanes (n-pentane, n-hexane, and n-heptane) burning in air. Completeness of combustion was characterized and evaluated for the three alkanes studied and was compared with results previously obtained for alcohols (methanol, I-propanol, and I-butanol) burning in air. When the alkanes were burred, with CO and CO 2 the principal carbon-containing products, less than 15% of fuel carbon was converted to product CO as opposed to CO 2 . Accounting for incomplete combustion in a numerical model that employs a one-step overall reaction led to less than a 5% decrease in burning rates and a drop in peak temperatures of less than 50 K. By contrast, when alcohols are burned, more than 30% of fuel carbon is found in product CO. Slightly lower temperatures in the free-convection boundary layers of the alcohols might account for some of this when the reactions concerning the conversion of CO to CO 2 are considered. However, reaction mechanisms currently favored for the combustion of methanol under fuel-rich conditions would account for a large part of the differences in amounts of CO formed by the alcohols and the alkanes.