不同后处理装置对柴油车颗粒物减排的影响

Particle Emissions Characteristics of Diesel Bus with Different After-treatments

为研究柴油机氧化催化器(DOC)、催化型颗粒捕集器(CDPF)与DOC+CDPF三种后处理装置对颗粒物的减排性能随行驶里程的变化规律,采用便携式排放测试系统(PEMS)跟踪检测三辆分别加装DOC、CDPF与DOC+CDPF的柴油公交车.结果表明:行驶里程达到7万km时DOC性能劣化,且DOC对核膜态颗粒物减排能力的劣化程度大于凝聚态颗粒物,颗粒物数量(PN)和颗粒物质量(PM)减排率大幅下降至26.29%和7.69%,应进行保养;CDPF有效工作时间短,需要定期进行保养,CDPF对PN的减排率通过及时的高温保养可维持在较稳定水平;DOC+CDPF对颗粒物减排率始终维持在较高水平,且随行驶里程的增加呈先升后降的趋势,对核膜态颗粒物减排能力的劣化程度大于凝聚态颗粒物,至12万km时样车PN和PM减排率下降至82.68%和68.41%.DOC+CDPF对颗粒物有更好且更稳定的减排效果.

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 aftertreatments 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.