Burning characteristics of coconut oil vapor-air mixtures at premixed combustion

Burning characteristics of coconut oil vapor-air premixed combustion has been studied experimentally. This study was conducted using Hele-Shaw cell of 50cm × 20cm × 1cm. Coconut oil in this study has the composisiton of 12% glycerol and 88% fatty acid (consisting of 18.77% caprylic acid, 15.15% capric acid, 41.78% lauric acid, and 11.86% myristic). The combustion propagation direction was varied by igniting from top or from bottom. Flame propagation was observed at various equivalent ratios (φ) of 2.73; 2.57; 2.34; 2.19; 2.03; 1.93 and 1.78. The results show that coconut oil tends to be degraded into fat and glycerol because of hydrolysis reaction. Fatty acid is burned before glycerol. Fatty acid tends to produce separated flames of different boiling points and molecule weights. The process of energy release from glycerol needs high rate of combustion process and it tends to slow flame propagation and causes micro explosions. The flame propagating downward at φ = 2.73; 2.57 and 2.34 show orange flames that cause moderate micro-explosions. At φ = 2.19; 2.03 and 1.93, the flames are blue-green, causing strong microexplosions. At φ = 1.78 the flames are dark purple, causing weak micro-explosions. For flame propagating upward, only at φ = 2.03, the micro explosions can be seen clearly since the thermal expansion is high and the flame propagates fastest.