PM Emissions from Light-Duty Diesel Vehicles Retrofitted with Diesel Particulate Filters

Two Euro 4 light-duty diesel vehicles were retrofitted with Diesel Particulate Filters (DPF). One was retrofitted with a low efficiency flow-through DPF. And, the other was retrofitted with a high efficiency wall-flow DPF. PM emissions from both vehicles were evaluated under the new European drive cycle (NEDC) on a chassis dynamometer. Several instruments were used to measure particulate matter (PM) emissions simultaneously from different aspects for two retrofitted vehicles.

The PM mass emission from the vehicle retrofitted with the low efficiency DPF is close to 5.0 mg/km Euro 5 mass emission standard. However, the solid particle number emission is about 30 times higher than the Euro 5 solid particle number emission standard. Mass and number emissions from the vehicle retrofitted with the high efficiency DPF are well below Euro 5 emission standards. A small amount of soot (about 90 mg) loaded on the wall-flow DPF makes the DPF filtration efficiency which is calculated from the solid particle number emission to increase roughly from 90% to 99%. This may imply that more soot loaded on the DPF may not increase too much on the filtration efficiency, but mainly increase the pressure drop over the DPF.