Effect of a DPF and Low Sulfur Lube Oil on PM Physicochemical Characteristics from a Euro 4 Light Duty Diesel Vehicle

This paper studies the effect of a Catalyzed Diesel Particle Filter (CDPF) on the emission profile of a Euro 4 diesel vehicle operated on low sulfur fuel and lubrication oil. The vehicle was tested in its original configuration and with the CDPF retrofitted in place of its main underbody catalyst. Experiments included steady state tests, the certification cycle and real-world high speed transient driving conditions. Measurements included total particle mass collected on Teflon-coated filters, total particle number measured by a condensation particle counter, size distributions determined by a Scanning Mobility Particle Sizer and chemical analysis of the mass collected for elemental and organic carbon, ions, PAHs, and trace elements. Results showed that the vehicle complies with the Euro 4 emission limits when tested over the type-approval NEDC, but it emits more nitrogen oxides and, in some cases, more particulate matter when tested over real-world test cycles. The CDPF reduces PM mass emission up to 90-95% and particle number by 2-3 orders of magnitude. However, nucleation of volatile species may occur under specific conditions of the engine exhaust dilution and sampling system and may mask this reduction. Emissions of chemical elements, elemental and organic carbon were also substantially reduced by the CDPF, while moderate reductions of ionic species and PAHs were observed.