The diesel engine emits exhaust particles that pose a unique set of measurement requirements. To document the state-of-the-art of measurement technology and to improve measurement quality, the Smoke and Particulate Panel of the Diesel Exhaust Composition group of the Coordinating Research Council reviewed published literature and particulate-sampling data generated by panel members to identify (1) the effects of key sampling parameters on measured particulate mass, (2) the causes of measurement variability, (3) the effects of dilution system design on particulate mass measurement, and (4) promising real-time mass measurement methods.
The panel found greater measurement difficulty associated with particulates than for gaseous pollutants because of engine-produced variations, the sensitivity of measured particulate mass to dilution parameters, and random errors in the independent measurements which comprise a particulate measurement.
Inter-laboratory comparisons showed that measurement variability is influenced by test type, ambient conditions, fuel properties, tailpipe connector design, and dilution system design. Also, greater inter-laboratory measurement variability existed for heavy-duty engines than for light-duty engines. Part of the added variability was due to differences in the dilution techniques used to dilute the high flow rates of the heavy-duty engines.
Two new promising real-time measurement techniques were identified.