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This research investigates the effect of nanoparticle-diesel fuel blends on combustion characteristics, performances and exhaust emissions of a four-stroke single-cylinder diesel engine. Three types of nanoparticles employed in this experiment were aluminium oxide, carbon nanotubes and silicon oxide. The nanoparticles were dispersed in a dosage of 25 ppm, 50 ppm and 100 ppm with pure diesel and were labelled as DA25, DA50, DA100 (aluminium oxide blends), DC25, DC50, DC100 (carbon nanotubes blends) and DS25, DS50, DS100 (silicon oxide blends). The ultraviolet-visible spectrophotometer analysis was done for 200 h to quantify the stability of the nanoparticle-diesel fuel blends. The blended fuels were experimentally tested with YANMAR TF120M diesel engine at engine loads of 0%, 25%, 50%, 75% and 100% at a constant 1800 rpm engine speed. The results revealed that the brake specific fuel consumption reduced by up to 19.8% and brake thermal efficiency enhanced by 18.8%. Silicon oxide blends show better results than aluminium oxide blends in many aspects, such as higher combustion pressure, lower brake specific fuel consumption and lower carbon monoxide emissions. Aluminium oxide and silicon oxide show stable blend conditions with 28.1% and 22.0% absorption ratio at 200 h sedimentation time, while carbon nanotube blends were least stable with absorption ratio reducing to less than 30% after 10 h. Combustion analysis of carbon nanotube blends with diesel show that carbon nanotubes have the potential to be further researched as an additive for diesel fuel due to significant combustion improvement in NOx emissions. However, the issue on the stability of carbon nanotube blends must be resolved before its potential can be fully utilized.

The global diesel fuel stock has been decreasing due to its non-renewable source. Hence, many researchers have focused on an alternative fuel that can reduce the use of fossil fuel. Alternative fuels such as biodiesel, bio-alcohol and other biomass sources have been extensively research to find its potential to be used in internal combustion engines aimed at discovering alternative sources to fossil fuels. The advantage of using biodiesel is that is produces less greenhouse gases overall than fossil fuels when burn and less particulates such as soot and other fine particles. This experiment compared the performance of pure diesel (D), biodiesel (BD) and organic germanium-biodiesel blend (BG5) at five different speeds ranging from 1200 rpm to 2400 rpm. Results showed that BG5 shows a different combustion performance compared to BD. When compared to BD in terms of engine power, no significant changes observed at a low speed (1200 rpm). On the contrary, at higher speeds (1800 rpm and 2400 rpm), BG5 blend fuel showed increased engine power of 12.2 % and 9.2 %, respectively. Similarly, results on torque showed similar findings as engine power, whereby the improvement could be seen at higher speeds (1800 rpm and 2400 rpm) when torque increased by 7.3 % and 2.3 %, respectively. In addition, the emission results indicated that for all speeds, CO2, and NO had reduced at an average of 2.1 % and 177 %, respectively. Meanwhile, CO emission had slightly increased compared to BD at low speeds by 0.04 %. However, the amount of CO released had decreased at an average of 0.03 % as the engine speed increased. Finally, measurement of O2 shows an increment at 16.4 % at all speed range.