An experimental study of the effect of biodiesel on the ignition and combustion characteristics of single droplets of glycerol

The effect of residual biodiesel on the ignition and combustion characteristics of single droplets of glycerol was experimentally studied. Biodiesel was added into pure glycerol at concentrations ranging from 1 to 3v% to simulate biodiesel residue in glycerol as the by-product of trans-esterification of fatty acids. The single droplets of glycerol with and without biodiesel were suspended on the tip of a silicon carbide fibre and then ignited and combusted in a horizontal tube furnace maintained at 1023K. The ignition and combustion processes of the single droplets were recorded using a high-speed CCD camera. The droplet size, ignition delay time, burnout time, and burning rate were determined by analysing the history of the captured images. Biodiesel preferentially evaporated first, leading to the ignition of the droplet and the formation of a reddish flame. Subsequently, glycerol evaporated and burned with a greenish flame. As the biodiesel concentration increased, ignition delay and burnout times decreased while the burning rate of the droplets increased.