An Investigation of Particulate Morphology, Microstructures, and Fractal Geometry for ael Diesel Engine-Simulating Combustor

The particulate matter (PM) produced from a diesel engine-simulating combustor was characterized in its morphology, microstructure, and fractal geometry by using a unique thermophoretic sampling and Transmission Electron Microscopy (TEM) system. These results revealed that diesel PM produced from the laboratory-scale burner showed similar morphological characteristics to the particulates produced from diesel engines. The flame air/fuel ratio and the particulate temperature history have significant influences on both particle size and fractal geometry. The primary particle sizes were measured to be 14.7 nm and 14.8 nm under stoichiometric and fuel-rich flame conditions, respectively. These primary particle sizes are smaller than those produced from diesel engines. The radii of gyration for the aggregate particles were 83.8 nm and 47.5 nm under these two flame conditions. These results were compared with particulate mobility diameters measured by using a Scanning Mobility Particle Sizer (SMPS). Fractal dimensions were also measured to standardize the geometry of the particulates collected from both diesel engines and the combustor. The result for combustor soot showed that the fractal geometry of particulates formed at a stoichiometric condition resembles that of heavy-duty diesel particulates and the fractal geometry of particulates at a fuel-rich condition that of light-duty diesel particulates.