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In order to examine the effect of fuel aromatics on soot processes in diesel flame, nanostructure and morphology of soot particles directly sampled in a diesel flame were investigated via High-Resolution Transmission Electron Microscopy (HRTEM). Three test fuels with different aromatic contents, aromatic-free Fischer-Tropsch Diesel (FTD), naphthalene-added (65,000ppm) FTD and conventional JIS#2 diesel fuels were used. TEM grids were directly exposed to single-shot diesel flames in a constant volume combustion chamber under a diesel-like condition with EGR (1000K, 2.7MPa, 15%O2) to thermophoretically sample soot particles at different axial locations from 40 to 120mm from nozzle. The soot nanostructure such as length, tortuosity and separation of lattice fringes in primary particles and morphology such as primary particle diameter and aggregate gyration radius were analyzed and compared among different fuels and in-flame locations.

In order to examine the effect of aromatic addition to Fischer-Tropsch Diesel (FTD) fuel on formation and oxidation processes of soot particles in diesel spray flame, small amount of naphthalene (0 to 65,000 ppm) was added to the FTD fuel and variation of soot morphology and nanostructure of primary soot particles directly sampled in a diesel spray flame were investigated via High-Resolution Transmission Electron Microscopy (HRTEM). A single-shot diesel spray flame was achieved in a constant volume combustion chamber under a diesel-like condition (Ta=1000K, Pa=2.7MPa) and a grid for HRTEM observation was directly exposed to the spray flame to thermophoretically sample soot particles onto the grid surface. The primary particle diameter, aggregate gyration radius, lattice fringe length, lattice fringe tortuosity and lattice fringe separation of soot particles sampled at different locations (from 60 to 90mm from nozzle tip) in the spray flame were analyzed.