Effects of various nanoparticle additives on the ignition and combustion characteristics of diesel

Nanoparticles exhibit significant potential for optimizing base fuel properties and enhancing engine combustion and emission characteristics. However, their fundamental auto-ignition and flame development behaviors under in-cylinder conditions are not yet fully elucidated. In this context, the spray and combustion characteristics of the resulting nano-diesel were systematically investigated in a constant volume vessel using high-speed imaging and the two-color method. CeO 2 , MoO 3 and MWCNTs with an average particle size of 50 nm were selected as fuel additives to prepare nano-diesel at a blending concentration of 100 mg/L. The results showed that, under an ambient temperature of 800 K, an ambient pressure of 3.5 MPa, and an injection pressure of 60 MPa, the ignition delay periods of Ce100, Mo100, and CNT100 were 28.85 %, 26.92 %, and 24.04 % shorter than that of diesel, respectively. Their ignition locations were also reduced by 29.34 %, 26.90 %, and 23.13 %, respectively. Furthermore, the average apparent flame temperatures of Ce100, Mo100, and CNT100 were higher than that of diesel, with Ce100 showing the largest increase. However, these differences were not statistically significant. Meanwhile, the average apparent KL factor of Ce100 was higher than that of diesel, whereas those of Mo100 and CNT100 were lower. Although these differences were not statistically significant, the average-value trends suggest that CeO 2 tends to increase soot formation, whereas MoO 3 and MWCNTs tend to reduce it. Across different ambient temperatures, the addition of MWCNTs effectively promotes ignition, resulting in shorter ignition delays and ignition locations closer to the nozzle. As the ambient temperature increased from 800 to 850 K, both the apparent average flame temperature and the apparent average KL factor increased for diesel and CNT100. Additionally, CNT100 yields a higher apparent average flame temperature than diesel under the aforementioned conditions, while showing a lower apparent average KL factor.