Observation of Combustion Behavior for Single Droplets of Water-in-Oil Emulsified Fuels. Temperature History of Oil Droplets and Consideration of Ignition Time Lag.

The temperature histories for single droplets of water-in-'A' heavy oil emulsions were measured simultaneously by taking pictures of combustion behavior with a high-speed camera, in order to elucidate the growth mechanism of microexplosions. The occurrence of microexplosions is mainly dominated by the relative ratio of the sizes of water droplets dispersed in the emulsified fuels to the size of the oil droplet, and it is also related to the heat capacity of the oil droplet. The apparent activation energies from the experiments for the ignition time lag reveal that the emulsified fuels have the effects of both retarding the ignition by absorption of the latent heat and conversely, promoting the ignition by flashing the boiling water droplets accompanied by a small amount of oil. Surfactants may be the factor retarding the ignition and suppression of the occurrence of microexplosions for the resultant effect of stabilizing the emulsified fuels.