Experimental investigation on the effect of carbon chain length to the droplet combustion characteristic of fatty acid methyl ester

Biodiesel which produces from vegetable oil consists of various fatty acids as fatty acid methyl ester constituent. Each fatty acid has a specific combustion characteristic due to the difference in physicochemical characteristics. This study was done with a single fatty acid methyl ester from various saturated fatty acids to analyze the effects of carbon chain length on the droplet combustion during the evaporation and combustion stages in ambient temperature and atmospheric pressure. Results show that the ignition delay time increase with the longer carbon chain due to the higher viscosity and boiling point. The higher oxygen content in the fatty acid methyl ester molecule promotes the faster combustion, gives a higher burning rate, and cause the flame dimension shorter. Furthermore, oxygen content results in higher radiation caused a brighter flame. The high droplet temperature occurs in the long carbon chain due to the higher of combustible matter gives an increase to the heating value. Low radiation heat loss in a long carbon chain which indicates by the flameless bright also causes the droplet temperature higher. The higher droplet temperature gives the lower gas density which causes the flame dimension higher due to the natural convection.