1988-02-01

A Comparison of Exhaust Pipe, Dilution Tunnel and Roadside Diesel Particulate SOF and Gaseous Hydrocarbon Emissions 880351

The solvent organic fraction (SOF) of particulates from the exhaust pipe of a diesel engine, a dilution tunnel and a roadside sample are compared. Three different techniques of SOF analysis are also compared, vacuum oven, solvent extraction and pyroprobe/GC. Gaseous hydrocarbons and the methane contribution were measured in the exhaust pipe throughout the speed and load range of the engine at 185 C and 2 C. The unburnt hydrocarbons decreased with air/fuel ratio for all speeds and there was an overall decrease in emissions with increasing speed. The differential temperature technique showed the maximum mass of hydrocarbon which could condense from the gas phase onto the particulate as the SOF. The method compared well with the actual SOF of the tunnel particulate. Detailed examination of the SOF showed the exhaust pipe particulate SOF was composed of n-alkanes from C16 to C25, the dilution tunnel sample showed condensation of lower molecular weight hydrocarbons from the gas phase onto the particulate. The roadside SOF contained many hydrocarbons in addition to the n-alkanes derived from automotive sources. Comparison of the SOF by solvent extraction and pyroprobe/GC hydrocarbons showed that these were identical for the exhaust pipe and dilution tunnel. Comparison of a diesel fuel sample also showed that the two techniques produced identical results. The roadside samples produced chromatographic profiles which were markedly different. The samples were collected at different sample times when background particulates may have varied. Pyroprobe/GC of other automotive particulates, namely rubber tyres and lubricating oil produced hydrocarbon emissions similar to those found in the roadside environment. The commercially available pyroprobe/GC technique provides a rapid and detailed analysis of the diesel exhaust pipe and dilution tunnel particulate SOF.

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