柴油机后处理装置的颗粒排放物拉曼光谱研究

Raman Spectroscopy Research of Particulate Emissions from Diesel Engine with After-treatment Device

摘要:

为研究发动机排放颗粒物经氧化催化转化器（DOC）以及柴油颗粒捕集器（DPF）后结构和化学组成的变化规律，在一台配备后处理装置的电控高压共轨增压中冷柴油机上进行颗粒物取样，采用激光拉曼光谱仪测取拉曼光谱，比较了不同测点位置颗粒物的拉曼光谱特征。结果表明：颗粒物的拉曼光谱均由5个峰组成，且峰位在一个较小的范围内变化，描述颗粒物结构和组成的各特征参数随测点位置的不同而变化，即ID1 /IG 随测点后移而减小，ID2 /IG 逐渐增大，而ID3 /IG 、ID4 /IG 和IALL /IG 均表现为先减小后增大的趋势，说明经过DOC和DOC+DPF时颗粒物发生了物理和化学变化，从而使颗粒结构和成分发生变化。代表颗粒物石墨化程度的ID1 /IG 值随测点的后移而增加，但是DPF后颗粒的有机物成分所占比例最大。

Abstract:

In order to investigate the evolution law of structure and chemical components of diesel engine particulates during passing through diesel oxidation catalyst (DOC) and diesel particulate filter (DPF), particulates samples emitted from an electronic control high pressure common rail, turbocharged, inter-cooler diesel engine with exhaust after-treatment device were collected on the glass fiber filters. Raman spectrums at different points were measured, and characterizations of the spectrums were compared. The results showed that the Raman spectrum of engine particulates was composed of five peaks and the Raman shift of the peaks changed within a very small range. Every characterization parameter describing the structure and components of particulates varied with the different measuring points, i. e. as the measuring point shifted backward, the ID1 /IG decreased, ID2 /IG increased, ID3 /IG ,ID4 /IG and IALL /IG had the trend of first increase and then decrease, which indicated that the changing process of structure and components of the particulates was not only a physical process but also a chemical one. On behalf of the degree of graphitization of the particulates of ID1 /IG increased with the backward shift of the measuring point, but the organic fractions in the particulates reached maximum.