EGR对轻型柴油机超细颗粒排放的影响

基于1台匹配废气再循环(EGR)系统的轻型柴油机,在中低负荷下研究了EGR对发动机超细颗粒排放的影响.研究发现:各工况下,随EGR率的增大,颗粒排放中核模态颗粒数量浓度在各粒径下有所减少,核模态颗粒排放数量速率和质量速率有减少趋势,且在最大扭矩转速的低负荷工况更加明显;积聚态颗粒数量浓度在各粒径下都增加,积聚态颗粒排放数量和质量速率也都增加,且中负荷时更加明显,而积聚态颗粒数量浓度峰值粒径基本没有改变.随EGR率的增大,总的超细颗粒排放数量速率在最大扭矩转速的低负荷工况减小,而其他工况都明显增加.由于积聚态颗粒总质量浓度占超细颗粒总质量浓度比例达99%,所以超细颗粒排放质量速率也都增加,几何平均粒径也都明显增大.在低负荷较低EGR率和中负荷较大EGR率时,过高的喷油压力都将使超细颗粒排放数量速率增加.

Effects of EGR on Ultrafine Particulate Emission of Light-duty Diesel Engine

The effects of EGR on ultrafine particulate emission were researched at medium and low loads on a light-duty diesel engine with EGR .The results show that the number concentration of nuclear mode particulate in each size decreases ,the emis-sion number and mass velocity of nuclear mode particulate have a decrease trend and becomes more obvious at low load of maxi-mum torque with the increase of EGR rate .The number concentration of accumulation mode particulate in each size increases , the emission number and mass velocity of accumulation mode particulate also increase and become more obvious at medium load ,but the corresponding size of number concentration peak keeps the same .In addition ,the total ultrafine particulate emis-sion number velocity decreases at low load of maximum torque speed and obviously increases under other conditions with the in-crease of EGR rate .Due to 99% proportion of total mass for accumulation mode particulate in that of ultrafine particulate ,the emission mass velocity and geometric mean size of ultrafine particulate increase .At lower EGR rate at low load and larger EGR rate at medium load ,the higher injection pressure will lead to the increase of number concentration of ultrafine particulate .