Search Results

In order to better understand in-flame diesel soot oxidation processes, soot particles at the oxidation-dominant periphery of diesel spray flame were sampled by a newly developed “suck” type soot sampler employing a high-speed solenoid valve and their morphology and nanostructure were observed via high-resolution transmission electron microscopy (HR-TEM). A single-shot diesel spray flame for the soot sampling experiment was achieved in a constant-volume vessel under a diesel-like condition. The sampler instantaneously sucks out a small portion of soot laden gases from the flame. A TEM grid holds inside the flow passage close to its entrance is immediately exposed to the gas flow induced by the suction at the upstream of the solenoid valve, so that the quick thermophoretic soot deposition onto the grid surface can effectively freeze morphology variation of soot particles during the sampling processes.

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.