Comparative Study on Various Methods for Measuring Engine Particulate Matter Emissions 2008-01-1748

Studies have shown that there are a significant number of chemical species present in engine exhaust particulate matter emissions. Additionally, the majority of current world-wide regulatory methods for measuring engine particulate emissions are gravimetrically based. As modern engines considerably reduce particulate mass emissions, these methods become less stable and begin to display higher levels of measurement uncertainty.

In this study, a characterization of mass emissions from three heavy-duty diesel engines, with a range of particulate emission levels, was made in order to gain a better understanding of the variability and uncertainty associated with common mass measurement methods, as well as how well these methods compare with each other. Two gravimetric mass measurement methods and a reconstructed mass method were analyzed as part of the present study. The results have shown that each of the mass measurement methods analyzed compare well at higher emission levels, but show significant disparity at the ultra-low emission levels commonly seen from modern diesel engines. Additionally, at ultra-low emissions, the uncertainty in the measurement becomes large, thus reducing confidence in the accuracy of the measurement. Based upon these findings, it would be difficult to justify a comparison between any two gravimetric measurement methods and it may be more appropriate to perform a reconstruction of the particulate mass due to a lower susceptibility to measurement error.