Laminar Smoke Points of Candle Flames
Allan, Kathryn M
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An experimental investigation of laminar smoke points of candle flames is presented. A smoke point is the flame length just before the onset of visible smoke release. Adjustable wicks with diameters of 2 - 7.6 mm were used to measure smoke points in quiescent air for 14 different waxes. The measured smoke points varied from 36 - 89 mm and increased with wick diameter. Smoke points fitted to a wick diameter of 4 mm increased from consumer-grade waxes (candelilla, carnauba, beeswax, paraffin) to alkanes (hexatriacontane, octacosane, tetracosane) to alcohols (octadecanol, docosanol, hexadecanol) to acids (stearic, palmitic, lauric, myristic). Within each wax family, a decrease in carbon number yielded an increased smoke point. Soot emission was not possible for any fuel when the wick diameter was below 1.8 mm or when wick length was below 6 mm. The results suggest new ways of producing cleaner burning candles.