下阶段排放法规趋于引入基于冷起动与热稳运行阶段分段考核的PEMS试验方法，深入探究各阶段PN排放的关键影响因素具有重要意义。基于发动机台架模拟PEMS试验的方法，研究了不同碳载量下冷起动与热稳运行两个阶段的PN排放特性。研究结果表明：在冷起动阶段，因初始滤饼层厚度对DPF物理过滤效率的决定性影响，PN排放随碳载量增加呈现先急剧下降后小幅回升的趋势；在热稳运行阶段，受高温下碳烟被动再生引发二次颗粒生成的影响，PN排放随碳载量增加显著提高。基于上述规律，进一步识别出可实现全工况最优PN排放平衡的DPF碳载量窗口。

With the impending introduction of a new PEMS test methodology in future emission standards, which segments  evaluation into cold-start and thermally stable operation phases, a thorough investigation into the key factors influencing PN emissions at each stage is of significant importance. The PN emission characteristics during both cold-start and thermally stable operation phases under different soot loading conditions were investigated by utilizing an engine bench simulation method for PEMS test. The results indicate that PN emissions exhibit a trend of initial sharp decline followed by a slight rebound with the increase of soot loading during the cold-start phase, attributable to the decisive influence of initial soot cake layer thickness on the physical filtration efficiency of DPF. During the thermally stable operation phase, PN emissions increase significantly with the rise of soot loading, primarily due to the secondary particle generation triggered by soot passive regeneration under high temperatures. Based on the observed patterns, an optimal DPF soot loading window capable of achieving the best balanced PN emissions across the entire operating cycle is further identified.