铁基燃油添加剂对柴油机排气颗粒物理化特性的影响

Effects of Fe-Based Fuel Additives on Physical and Chemical Properties of Diesel Engine Emission Particulates

在国Ⅴ标准0~#车用柴油中分别添加质量分数为150μg/g、300μg/g的铁基添加剂(Fe-FBC),制备Fe150和Fe300两种燃油,并基于发动机台架试验,采用颗粒采样分析仪进行排气颗粒采集。运用热重分析仪和扫描电镜研究颗粒物热解性质与微观形貌结构,采用傅里叶红外光谱仪和光电子能谱仪对颗粒表面官能团进行半定量分析。结果表明:在发动机额定工况下,加入Fe-FBC后排气颗粒干碳烟质量分数降低,氧化温度与表观活化能均有显著下降;相比于纯柴油燃烧颗粒物的积聚体形态,Fe300燃烧颗粒物的团聚程度变弱,存在较多的链状结构;颗粒表面官能团拥有较多的—OH键与C—H键,C—H键为饱和烃CH_3结构;颗粒微晶边缘碳原子更加混乱,石墨化程度降低,容易被氧化;Fe300燃烧颗粒物中C元素含量降低,O元素含量增加,Fe元素价态为+2和+3价,颗粒表面吸附有更多能与Fe元素相结合的含氧基团。

Fe-based additives (Fe-FBC) were added to 0 # diesel (China Ⅴ) with Fe mass fraction of 150 μg/g and 300 μg/g respectively to prepare two blended fuels,which were named as Fe150 and Fe300 correspondingly.On a test bench,AVL Smart Sampler was used to collect exhaust particles at the rated power of the test engine.Thermogravimetric Analysis and Scanning Electron Microscopy were employed to study the micro-morphology of the particles.Fourier Transform Infrared Spectrometer and X-ray Photoelectron Spectrometer were used to analyze the surface functional groups of the particles.The experimental results show that the mass fraction of dry soot decreases with the addition of Fe-FBC,and it was also found both the oxidation temperature and activation energy of the above dry soot decrease significantly.Compared with the agglomeration morphology of particles from normal diesel,particles from Fe300 have less aggregation degree and more chain structures.In addition,for particles from Fe300,their surface functional groups have more -OH and C-H chemical bonds,and C-H bonds are saturated CH 3 structures.For particles from Fe300,it also can be observed that carbon atoms at the edge of granular microcrystalline are more chaotic and the graphitization degree decreases.All the above characteristics indicate that the emission particulates from Fe300 are much easier to be oxidized.Compared with emission particles from normal diesel,there are less carbon contents but more oxygen contents for Fe300 emission particles,in which the valences of most Fe are +2 and +3.As well,more oxygen-containing groups are combined with Fe on the surface of Fe300 emission particles.