The impact of Al2O3 nano additives on Jatropha curcas biodiesel-diesel blend on combustion and emission behavior

This research examined the effect of using different Jatropha oil-derived biodiesel-diesel blends on the emissions and combustion behavior of a diesel engine. The experiment was conducted at a constant 80 % load on a single- cylinder, air-cooled, direct injection (DI) diesel engine using diesel (B0) and four biodiesel blends (B5, B10, B20, and B40), with and without 100 ppm of Al2O3 nanoparticles (NPs). Emissions such as unburned hydrocarbons (UHC), carbon monoxide (CO), nitrogen oxides (NOx), and soot opacity were analyzed. The minimum measured CO emission values were 0.20 %V and 0.31 %V for B20 with and without Al2O3 NPs, respectively, at 2900 rpm. Except for B10 at maximum speed, UHC emissions decreased as the proportion of biodiesel in the blends increased. The high cetane number of biodiesel and the oxygen content of biodiesel and Al2O3 NPs tended to reduce emissions by 12.6 %, 11.12 %, 9.9 %, 8.9 %, and 8.1 % for B0, B5, B10, B20, and B40, respectively. Adding Al2O3 NPs significantly reduced NOx emissions by 19.7%, 15.9%, 14.0%, 7.6%, and 12.5% for B0, B5, B10, B20, and B40, respectively. Overall, the addition of Al2O3 NPs improved the combustion properties of the biodiesel blends, enhanced combustion performance, and reduced exhaust emissions. Soot opacity decreased as the proportion of biodiesel in the blends increased, with a maximum reduction of 8 % observed in the speed range of 2100-2500 rpm. The maximum cylinder pressure was 52 bar and 51.4 bar for B5 with and without Al2O3 NPs, respectively. The maximum heat release rate (HRR) was 34.6 J/CA for B5 with Al2O3 NPs and 34 J/ CA for B20 without Al2O3 NPs. Adding NPs also increased cylinder pressure and the net heat release rate (NHRR) for all biodiesel blends, with the highest increase observed for B5 with Al2O3 NPs. Without Al2O3 NPs, the maximum cylinder pressure was achieved for B5, while the highest NHRR was observed for B20. A notable finding was that the engine speed for maximum power and torque shifted from 2400 rpm to 2600 rpm when biodiesel blends with NPs were used, indicating that fuel composition and additives influence the speed at which peak performance is achieved. However, further research on modified injection techniques, including multiple injection events, is recommended to address the still high NOx emissions and achieve optimal engine operation.