Combustion, performance, and emission analysis of diesel engine fueled with water-biodiesel emulsion fuel and nanoadditive

The present study is aimed to analyze the combustion, performance, and emission characteristics of water-emulsified soybean biodiesel fueled diesel engine with alumina nanoadditive and the results compared with conventional diesel fuel (BD). Experiments were conducted in a single-cylinder, four-stroke, variable compression ratio, and natural aspirated diesel engine with an eddy current dynamometer at a constant speed of 1500 rpm. Water-soybean biodiesel emulsion fuel was prepared using a mechanical agitator, in which the water concentration was limited to 10%, whereas soybean biodiesel (SB) and surfactant concentrations were 89% and 1% by volume respectively. Alumina (Al) was chosen as a nanoadditive, and the mass fractions of 50 ppm and 100 ppm were blended with emulsion fuel using ultrasonicator and the physicochemical properties were measured. The physicochemical properties of water-emulsified biodiesel and nanoadditive included emulsified biodiesel are at par with EN14214 limits. The in-cylinder pressure (ICP) and net heat release rate (NHR) values of SB are 5.3% and 7.2% lower than BD respectively, whereas the water inclusion significantly increases the ICP and NHR values by 6.9% and 15.9% compared to SB. Brake-specific fuel consumption (BSFC) of SB is higher than BD, and brake-specific energy consumption (BSEC) is lower than BD. An inclusion of 10% water in SB improves the BSFC and BSEC by 4% and 10.6% respectively compared to SB. The Al nanoparticle inclusion in water-emulsified soybean biodiesel further improves the combustion and performance parameters. The exhaust gas temperature (EGT) of sample fuels seems to be lesser than BD due to efficient combustion. As far as the emission characteristics are concerned, the SB promotes lower level of hydrocarbon (HC), carbon monoxide (CO), and smoke emissions with notable increases in oxides of nitrogen (NOₓ) and carbon dioxide (CO₂) emissions. An inclusion of 10% water in SB reduces the NOₓ, HC, CO, and smoke emission by 21.2%, 16.7%, 16.9%, and 11.8% respectively under peak brake mean effective pressure (BMEP) condition. The addition of Al nanoparticle in biodiesel emulsion fuel further reduce NOₓ, HC, CO, and smoke emissions and marginally increases the CO₂ emission.