Particle size distribution, number, and mass emissions from the exhaust of a 92 kW 1999 Isuzu 6BG1 nonroad naturally aspirated diesel engine were measured. The engine exhaust was equipped with a Dry System Technologies® (DST) auxiliary emission control device that included an oxidation catalyst, a heat exchanger, and a disposable paper particulate filter. Particle measurement was taken during the ISO 8178 8-mode test for engine out and engine with the DST using a scanning mobility particle sizer (SMPS) in parallel to the standard filter method (SFM), specified in 40 CFR, Part 89.
The DST efficiency of removing particles was about 99.9 percent based on particle number, 99.99 percent based on particle mass derived from number and size. However, the efficiency based on mass derived from the SFM was much lower on the order of 90 to 93 percent. This discrepancy in particle mass efficiency between the two methods was mainly due to poor correlation between the mass derived from number and size and the mass measured using the SFM. This poor correlation was obtained for the DST out particulate matter (PM) emission and not for engine out. For DST out PM, the SFM tends to exaggerate the mass emissions of particles due to the condensation/adsorption of gas phase non aerosol volatile compounds on the PalflexT60A20 filters used for particle mass measurement, thus resulting in a lower efficiency of particle removal.
If the health effect of particles is due to the mass and number of their physical characteristics, particle measurement using the SFM may need rethinking, particularly if the nature of the measured product is dominated by volatile rather than soot.