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Abstract In this research, a comparative study of combustion characteristics, performance and emissions of a turbocharged diesel engine fueled with diesel and methanol-Fischer-Tropsch (F-T) diesel-biodiesel-diesel blends at various simulated altitudes (0 m, 3500 m and 5500 m) were conducted. The blends were composed of diesel, methanol, F-T diesel and biodiesel at volume fractions of 65%, 15.2%, 15.6% and 4.2%, respectively. Diesel was used as the baseline fuel, methanol, F-T diesel and biodiesel were used to improve the atomization characteristics, cetane number and stability of the blends, respectively. The results indicated that the cylinder pressure, pressure rise rate and heat release rate of the engine fueled with the blends were lower than those of the diesel at an altitude of 0 m, but higher at an altitude of 5500 m. Peak torque values for the test fuels both appeared at 1400 rpm near the sea level and the speeds corresponding to the peak torque values increased with altitudes. The use of the blends improved the engine power and economic performance at low-speed ranges at an altitude of 3500 m but a dramatically reduce was observed at 5500 m. Compared with the diesel, the particulate matter (2.5 (PM 2.5)) for the blends was markedly lower, while a slightly higher in NOx at various altitudes. [ABSTRACT FROM AUTHOR]

Abstract: The diesel soot was extracted from the chamber of a running diesel engine using a total cylinder sampling system. A structural description and size distribution of the soot spherules were performed by means of high-resolution transmission electron microscopy (HRTEM). HRTEM image analysis was carried out to achieve semi-quantitative information about the soot organization. Different nanostructures were found in dependence upon the engine test conditions. A better organization of the graphitic layers occurred for the in-cylinder soot as the expansion stroke developed. The oxygen concentrations at sampling angles and the cylinder pressure were measured. The oxidation rates of the in-cylinder soot during the late combustion phase were calculated according to the differences of spherules size distributions between two consecutive sampling angles. The soot reactivity in dependence on the nanostructure was shown after deducting the effect of oxygen concentration and temperature. The increase of resistance toward oxidation was associated to the increase of the structural order for the in-cylinder soot. The results are a useful database for testing the structure–property relationship between the nanostructure and the reactivity of the in-cylinder diesel soot. [ABSTRACT FROM AUTHOR]