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Improving fuel combustion in engines and consequently reducing environmentally-unfavorable emissions is of prominent importance in addressing some of the main challenges of the current century, i.e., global warming and climate change. Fuel additives are considered as efficient way for improving fuel properties and to diminish engine emissions. In line with this, the present research was focused on the simultaneous application of water (3, 5, and 7 wt.%) and cerium oxide nano particles (90 ppm) as metal-based additive into biodiesel/diesel fuel blend (B5) and their impacts on the performance and emission characteristics of a single cylinder four stroke diesel engine were investigated. The findings revealed that the aqueous nano-emulsion of cerium oxide improved the overall combustion quality. More specifically, the brake specific fuel consumption (bsfc) of B5 containing 3% water and 90 ppm cerium oxide (B5W3 m ) was measured 5% and 16% lower than those of neat B5 and neat B5 containing 3% water (B5W3), respectively. Moreover, the B5W3 m fuel blend increased brake thermal efficiency (bte) by over 23 and 11% compared with B5W3 and B5, respectively. B5W3 m also considerably reduced CO, HC, and NO x emissions by 51, 45, and 27% compared with B5W3. To the best of our knowledge, this is the first report exploring the impacts of low-level water containing cerium oxide in B5 on engine performance and emission characteristics. [ABSTRACT FROM AUTHOR]

• Emission and performance parameters of a dual-fuel diesel engine were studied. • The engine operated with high natural gas substitution rates under various loads. • The pilot fuel was diesel/biodiesel emulsions doped with carbon nanoparticles. • The developed fuel blends could ignite well natural gas at high substitution rates. • Pilot fuel composition markedly affected engine emissions and performance. The dual-fuel (DF) combustion process is a promising engineering solution to achieve clean combustion and high thermodynamic efficiency. The composition of pilot fuel (PF) can be considered as one of the effective parameters on the combustion quality of the DF process. In general, employing biodiesel blended fuel samples as PF can reduce brake power (BP) and increase fuel consumption. Therefore, developing fuel formulations harboring additives that are capable of boosting brake power (BP) and reducing fuel consumption of DF diesel engines (DFDEs) while also mitigating their harmful emissions, is highly considered. To this end, the present study was set to investigate emission and performance characteristics of a natural gas (NG) DFDE ignited by water-emulsified (WE) diesel/biodiesel (D/B) blends (5 vol% biodiesel and 3 wt% water) containing 30 and 60 µM aqueous carbon nanoparticle (CNP). Neat diesel and D/B blend containing 5 vol% biodiesel were used as control fuel. The engine was fueled with high NG substitution rates (50–80% of the total fuel energy) at engine loads (25–100% of full load). Overall, emissions and performance characteristics of the engine were significantly affected by engine load and NG substitution rate. On average, the WE D/B blend doped with 30 µM could provide acceptable results in terms of engine emissions and performance. This fuel formulation could mitigate unburned hydrocarbon emissions by about 8 to 40% at different loads, even though increased NOx emissions. The power generation cost of the selected fuel blend was also about 5 to 23% lower than the control fuels. [ABSTRACT FROM AUTHOR]