Particle Emissions Characteristics of Diesel Bus with Different After-treatments

Abstract:

To assess the change of particle emissions characteristics of diesel oxidation catalyst convertor(DOC), catalyzed diesel particulate filter(CDPF), and catalyzed continuously regeneration trap(DOC+CDPF) with the increase of mileage, diesel particle number and mass emissions of three heavy-duty diesel buses have been measured: one equipped with a DOC, one equipped with a CDPF, and another equipped with an integration of DOC and CDPF. The emission measurement was conducted using a portable emissions measurement system (PEMS). Results show that the operating lifetime of DOC is around 70,000 km where the decreasing amplitudes of particle number (PN) and particle mass (PM) decrease to 26.29% and 7.69%; and the deterioration degree of the nucleation-mode concentration is bigger than accumulation-mode. The operating lifetime of CDPF is comparatively short; so, periodic maintenance with high temperature is necessary. The decreasing amplitude of PN can be kept at a steady level by maintaining timely. The combination of DOC and CDPF has a better impact on particle emission, with higher decreasing amplitudes of both PN and PM, and smaller fluctuations compared to other after-treatments used in this study. As the mileage increases, the particles increase firstly and then decrease; and the deterioration degree of the nucleation-mode concentration is bigger than accumulation-mode. The decreasing amplitudes of PN and PM obtained after 120 000 km have shown 82.68% and 68.41% degradation of the performance of DOC+CDPF; so, it should be maintained at this moment. The combination of DOC and CDPF has stable performance.