Growth and Combustion of Soot Particulates in the Exhaust of Diesel Engines 800984

The size and aggregation of soot particulates emitted from a diesel engine have been investigated using a transmission electron microscope, and the chemical composition in soot particulates were analyzed by a gas chromatograph in order to clarify the mechanisms of growth and combustion in the exhaust pipe.

In the present report, the following results have been obtained: (1) When the gas temperature was lowered below 400°C in the exhaust pipe, the soot particle distribution shifted to a larger size, from 50 Å to 100 Å. This tendency was remarkable in the case of lower gas temperatures, (2) In this case, polynuclear aromatic hydrocarbons in the soot particulates exhibited a tendency to increase in the downstream of the exhaust pipe. (3) When hydrocarbons, for instance C₂H₂, C₃H₈, etc., were added to the exhaust gas, the rate of growth of soot particles increased compared with no addition. (4) When the exhaust gas was heated up to above 600°C, it was observed that soot particulates burnt from their surface, and they became smaller or burnt out. In this case, smoke density decreased and soot particle distributions shifted to a smaller size.