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For a better understanding of soot formation and oxidation processes in conventional diesel and biodiesel spray flames, the morphology, microstructure and sizes of soot particles directly sampled in spray flames fuelled with US#2 diesel and soy-methyl ester were investigated using transmission electron microscopy (TEM). The soot samples were taken at 50mm from the injector nozzle, which corresponds to the peak soot location in the spray flames. The spray flames were generated in a constant-volume combustion chamber under a diesel-like high pressure and high temperature condition (6.7MPa, 1000K). Direct sampling permits a more direct assessment of soot as it is formed and oxidized in the flame, as opposed to exhaust PM measurements. Density of sampled soot particles, diameter of primary particles, size (gyration radius) and compactness (fractal dimension) of soot aggregates were analyzed and compared. No analysis of the soot micro-structure was made.

A study was conducted to investigate the evolution of liquid phase penetration of evaporating sprays under engine-like conditions, with diesel and biodiesel fuel blends. This study has been performed in a facility based on a single cylinder two-stroke direct injection Diesel engine operating at low rotational speed which provides a quiescent thermodynamic environment around TDC, when fuel is injected, realistic for current D.I. Diesel engines. Due to the absence of inlet or exhaust valves, very easy optical access to the combustion chamber can be provided through the cylinder head. Pure nitrogen is supplied to the engine as intake gas, in order to avoid combustion. The injection event is carried out by an electronically controlled common rail system. The injector is equipped with real 8-hole nozzles, with a hole diameter of 0.115 mm. Injection pressures in this study ranged between 30 and 160 MPa and different in-cylinder peak pressure and temperature values were considered.