The evolution of a single droplet water-in-palm oil derived biodiesel emulsion leading to micro-explosion

Palm oil methyl ester is blended with diesel oil as a commercial diesel product in Malaysia, known as biodiesel B10. Biodiesel mixed with water proved to reduced simultaneously both the particulate matter and NOx during combustion. Emulsified biodiesel also caused a secondary atomization due to micro-explosion of the fuel droplets, which is beneficial in improving combustion efficiency. The main factors and events leading to micro-explosion for palm oil derived biodiesel emulsified fuel has yet to be made available in the open literature. Hence, this study aimed to visualize the droplet evolution to micro-explosion of single droplet when heated. A single droplet was placed on the hot surface of a hotplate maintained at 500 degrees C and the droplet evolution time leading to micro-explosion were capture using a high-speed camera. The study found that all samples of the emulsified fuels produced micro-explosions in four distinct stages. The droplet underwent from a homogenous emulsion, turning from milky color to being transparent during the separation stage, volume expansion during the bubble growth stage, intense coalescence and puffing stage and finally micro-explosion stage. Larger water particles size and higher hydrophilic-lipophilic balance values are the main factors that caused shorter time leading to micro-explosion of droplets. (C) 2021 THE AUTHORS. Published by Elsevier BV on behalf of Faculty of Engineering, Alexandria University.

Automated summary

The study found that all samples of the emulsified fuels produced micro-explosions in four distinct stages. Larger water particles size and higher hydrophilic-lipophilic balance values are the main factors that caused shorter time leading to micro-explosion of droplets.