Stable Biodiesel-Water Emulsions with a Novel Surfactant to Improve Performance and Reduce Exhaust Emissions of a Light-duty Diesel Engine 2022-01-1090

Emulsification of biodiesel with water aids in reducing oxides of nitrogen (NO_x) and smoke emissions simultaneously whilst improving the engine performance. However, widespread commercial applications of biodiesel-water emulsions require cost-effective surfactants that result in stable emulsions to avoid the corrosive effects of water at high temperatures prevailing in the engine combustion systems. The current investigation explored the effect of adding water to biodiesel at 6 and 12% by weight. A novel, cost-effective surfactant Polyglycerol Polyricinoleate (PGPR), was used to stabilize the emulsions. A magnetic stirrer with a heating facility was utilized to prepare biodiesel-water emulsions that were stable for over five months. The experiments were carried out on a light-duty diesel engine at a constant rated speed and varying load conditions. The results obtained with the emulsions were compared with neat biodiesel as the reference fuel. The ignition delay increased for 6% and 12% emulsions by 9.5 and 14%, respectively, at 6.3 bar BMEP. Peak pressure increased by 4% for both the emulsions. At maximum load, the engine brake thermal efficiency improved by 5 and 7% with the 6 and 12% emulsions, whereas the fuel consumption improved by 4.5 and 13%, respectively. NO_x emissions were reduced by 19 and 27%, respectively, for the 6 and 12% emulsions, whereas smoke was decreased by 10 and 23% for the respective emulsions at rated load conditions. The carbon monoxide (CO) emissions were reduced by 46 and 54%, respectively, with 6 and 12% emulsions. The study demonstrates the effectiveness of moderate water emulsions in mitigating engine emissions whilst simultaneously improving engine performance. A novel surfactant also provides impetus to develop further emulsifiers tailored for use with biodiesel fuel.