柴油机颗粒数量排放特性研究

Particle Number Emission Characteristics of Diesel Engine

采用MEXA-2000SPCS颗粒物计数器测量柴油机排气污染物中的颗粒数量(PN),在不携带后处理催化器的情况下研究了发动机转速、负荷、EGR率以及负荷加载对柴油机PN排放的影响,在携带后处理催化器的情况下研究了氧化催化器(DOC)、催化型柴油颗粒捕集器(CDPF)碳载量以及环境温度对柴油机PN排放的影响。结果表明:在不携带后处理催化器的情况下,柴油机转速增加会直接导致PN排放量增大;随着柴油机负荷增大,PN排放量呈现先降后升的趋势;EGR率的增加会因为缸内燃烧恶化导致PN排放量增大;负荷加载会导致PN短时间大幅增加。DOC能够有效降低颗粒质量(PM),但无法减少颗粒数量(PN)。CDPF碳载量是决定PN排放量的重要因素,在不触发主动再生的前提下,碳载量的增加会降低PN的排放量。环境温度会影响CDPF被动再生速率,相同时间内随着环境温度的降低,CDPF碳载量累积能力越强,PN排放量越低。

The particle number(PN)emission of diesel engine was measured by using MEXA-2000 SPCS.The effects of engine speed,load,EGR rate and load loading on PN emission were studied without post-treatment catalytic converter and the effects of DOC,CDPF carbon load and ambient temperature on PN emission were studied with post-treatment catalytic converter.The results show that PN emission will increase with the increase of speed,will first decrease and then increase with the increase of load,will also increase with the increase of EGR rate due to the in-cylinder combustion deterioration,and will have a rapid and large increase with load loading before using post-treatment catalytic converter.After using post-treatment catalytic converter,DOC can effectively reduce particle mass(PM),but cannot reduce particle number(PN).CDPF carbon load is an important factor of determining PN emission and will reduce PN emission on the premise of non-triggering active regeneration.The passive regeneration rate of CDPF is affected by the ambient temperature and PN emission will become less because the cumulative capacity of CDPF carbon load for the same period becomes stronger due to the decrease of ambient temperature.