Emulsification – A promising approach to improve performance and reduce exhaust emissions of a biodiesel fuelled light-duty diesel engine

Abstract

The effectiveness of employing emulsions prepared with water and ethanol to reduce the inherently higher levels of oxides of nitrogen (NOx) emission with biodiesel, whilst improving or maintaining the smoke emission, is investigated in the present work. To facilitate a one-to-one comparison, the water/ethanol to biodiesel ratio for the emulsions was similar at 18% by mass. Experiments were conducted on a light-duty diesel engine at a constant speed and varying loads with diesel, biodiesel, biodiesel-water and biodiesel-ethanol emulsions. A novel surfactant, Poly Glycerol Poly Ricinoleate (PGPR), was used for preparing biodiesel-water emulsion that exhibited no phase separation for over four months. The results obtained with both emulsions were compared with neat biodiesel as the reference fuel. Ignition delay and peak pressure increased for both emulsions. The biodiesel-water emulsion resulted in advanced combustion phasing while it was retarded with ethanol emulsion. The brake thermal efficiency increased with biodiesel-water emulsion up to 7% at 6.3 bar brake mean effective pressure (BMEP) while at 3% with ethanol emulsion. The brake specific fuel consumption (BSFC) was reduced by 20% with biodiesel-water emulsion, while it remained the same as biodiesel with ethanol emulsion. The emulsions simultaneously reduced NOx and smoke emissions; the biodiesel-water emulsion was more effective, resulting in a maximum reduction of 45% and 37% in NOx and smoke emissions, respectively. The biodiesel-water emulsion also significantly reduced carbon monoxide (CO) emissions, with a maximum reduction of 54% at 6.3 bar BMEP. Overall, the emulsification of biodiesel provides considerable benefits in terms of reduced exhaust emissions and improved engine performance.