Emulsifier-free B50 biodiesel-water-ethanol emulsion fuel: A study on combustion characteristics, fuel performance, and emissions

Biodiesel is a prominent renewable energy alternative; however, its lower calorific value and elevated NOx emissions limit its suitability for high-percentage blends in diesel engines. This study addresses these challenges by introducing a novel approach to emulsifier-free B50 biodiesel emulsions with water and ethanol, prepared using the Mix on Demand Emulsification of Ethanol and Water with Biodiesel Blends (MDEEWB) system. The research aims to evaluate the effects of these emulsions on combustion efficiency, engine performance, and emissions. Experimental testing was conducted on a diesel engine at a constant speed of 2400 rpm across brake power levels of 1 kW, 2 kW, 3 kW, and 4 kW. Four fuels were tested: commercial diesel (D5M), B50 biodiesel (B50), emulsifier-free B50 biodiesel with 5 % water (B50W5), and emulsifier-free B50 biodiesel with 2.5 % water and 2.5 % ethanol (B50WE5). The results demonstrate that B50W5 and B50WE5 achieved superior performance at higher loads, with B50WE5 achieving the highest brake thermal efficiency (BTE) of 27.61 % at 4 kW. Notably, B50WE5 recorded the lowest NOx emissions across all loads, including reductions of 49.61 % at 1 kW and 20.84 % at 2 kW compared to B50. This study highlights the potential of emulsifier-free biodiesel-water-ethanol emulsions as eco-conscious diesel fuel alternatives. The findings provide critical insights into enhancing combustion efficiency, optimising fuel utilisation, and mitigating environmental impact in diesel engines. These contributions support the practical application of sustainable fuel technologies in meeting future energy and environmental demands.