Droplet Evolution and Stability of Water-in-Biodiesel Emulsion with Biosurfactant

Use of an alternative water-in-diesel emulsion (WiDE) fuel instead of pure diesel in a diesel engine reduces emissions and environmental pollution. However, as time passes, water from the emulsified fuel separates. Emulsion stability is affected by the amount of water, type of surfactant, and emulsion technique. Since biodiesel and biosurfactants are environmentally friendly as compared to pure diesel and chemical surfactants, biodiesel-emulsified fuel can reduce emissions, improve combustion, and improve engine performance. Water-in-diesel droplets split into tiny droplets during secondary atomization, which is believed to be caused by microexplosions. In this study, the effect of biosurfactant on the stability and microscopic behaviour of water-in-biodiesel emulsion (WiBDE) fuel were examined. A mixture of B10 biodiesel, 5% water, and a mixture of surfactant (63% lecithin and 37% TWEEN 85 (0.5–3%)) was emulsified for 20 minutes by using a magnetic stirrer at 1500 rpm. Six WiBDE fuel samples were observed for 10 days, and the microscopic behaviour of fuel droplets was examined. The evolution of droplets leading to micro-explosions was captured at 200 °C, 300 °C, and 400 °C. WiBDE-5, having a 2.5% surfactant concentration, is highly stable and reduces the time of micro-explosion of droplets, which can improve combustion and engine performance.