Detailed Chemical Composition and Particle Size Assessment of Diesel Engine Exhaust

A dilution source sampling system has been incorporated into the exhaust measurement system of a research single-cylinder diesel engine. To allow more detailed assessment of the individual chemical components of the diesel particulate matter (PM) the exhaust dilution system includes a residence time chamber (RTC) to allow for residence times of 30 to 60 seconds in the second stage of dilution before sampling.

Samples are collected on a range of different filters where mass loading, elemental and organic carbon (ECOC), trace metals, sulfate ions (SO₄), particle-phase organic compounds, and semi-volatile organic compounds are evaluated. In addition, particle size distributions have been determined using a scanning mobility particle sizer (SMPS).

Results show that the chemical composition of the particulate matter is highly dependent on the engine operating conditions. There is a dramatic shift in the ratio of elemental carbon to organic compounds and in the sulfate ions (SO₄) and trace metals when the engine is traversed across a load and speed range. Similarly there is a shift in the particle size range for which there is virtually no impact on the mass loading.