金属型GPF对GDI发动机颗粒物微观特性的影响

采用高分辨透射电镜(HRTEM)对安装了金属型汽油机颗粒捕集器(GPF)的汽油缸内直喷(GDI)发动机颗粒物进行观察,研究了转速为1500 r/min,负荷分别为25%、50%、75%和100%工况下的GPF前、后端颗粒物微观形貌及微观结构参数变化.结果表明:组成颗粒物的基本粒子均呈近似球形,堆积形成链状、枝状和环状等不规则几何形状,负荷和GPF对颗粒物微观形貌无明显影响;GPF前、后端收集的颗粒物基本粒子绝大多数为“外壳-内核”结构;GPF前、后端颗粒物的微晶尺寸、层间距和曲率均呈单峰分布,其中,GPF前、后端平均微晶尺寸随负荷的增加而增大,而平均层间距、平均曲率的变化规律则相反,说明颗粒物石墨化程度随负荷的增加而增大.负荷和GPF仅对颗粒物微观结构参数的大小有影响,对其分布规律没有影响.

Effect of Metal GPF on Micro Characteristics of Particulate Matters from GDI Engine

A high-resolution transmission electron microscopy(HRTEM)was used to observe the particulate matters emitted from a gasoline direct injection(GDI)engine equipped with a metallic gasoline particulate filter(GPF).Changes of microscopic morphology and micro-structure of the particulate matters before and after the GPF were compared at the engine speed of 1500 r/min and the engine load of 25%,50%,75%and 100%,respectively.The results show that the primary particles constituting the particulate matters are approximately spherical,and agglomerate to form irregular shapes such as chain,branch and ring.The engine load and the GPF have no obvious influence on the microscopic morphology of the soot particles.In addition,the primary particles consisting of the soot particles from pre-and post-GPF are"shell-core"structure and the fringe length,tortuosity and interlayer spacing of the primary particles are monomodal.Among them,the average fringe length increases with the increase of load,while both the average tortuosity and average interlayer spacing take the opposite change.These indicate that the degree of graphitization of particulate matters increases with the increase of engine load.Engine load and GPF only affect the micro-structure parameters of primary particles and have no effect on its distribution.