柴油机燃用Ce基FBC燃油颗粒物微观结构与化学分析

Microstructure and Chemical Properties of Particulate from Diesel Engine Fueled with Ce-based FBC Fuel

以环烷酸铈溶液作为燃油添加剂(FBC),依次按Ce元素质量比为50、100、150、300 mg/kg添加到柴油中,分别配制出F50、F100、F150和F300燃油。对共轨柴油机燃用铈基FBC燃油的燃烧颗粒,采用热重分析、气相色谱-质谱联用仪、扫描电镜和粒径分级采样的方法,研究了FBC燃油颗粒的氧化特性、可溶有机物组分(SOF)、粒径分布及微观结构。结果表明:随FBC掺混比的提高,颗粒物的氧化反应向着低温区域移动,含铈元素150 mg/kg时为最佳掺混比;与纯柴油颗粒相比,FBC颗粒的SOF中高碳原子数目下降,多环芳烃含量减少了49.2%;FBC颗粒粒径向着小粒径方向移动,核模态颗粒的数量浓度峰值增加了8.9%,而质量浓度峰值降低了14.5%;FBC颗粒物含有Ce元素质量分数为1.23%,其形貌为疏松多孔的海绵状,粘结程度明显降低。

In order to remove the deposited particles inside diesel particulate filter（ DPF） and realize the DPF regeneration,fuel borne catalyst（ FBC） additive is thought to promote diesel particle combustion with the active metal component in fuel. FBC can reduce the particulate ignition temperature,and also decrease the peak temperature of regeneration process. Naphthenic acid cerium solution was selected as FBC,which was blended with diesel by the ratios of 50 mg / kg,100 mg / kg,150 mg / kg and 300 mg / kg（ Ce mass fraction） and marked as F50, F100, F150 and F300, respectively. The particulate physicochemical properties of a common rail engine fueled with Ce-based FBC were studied by using thermosgravimetric analysis, gas chromatography / mass spectrometry（ GC-MS）, scanning electron microscopy（ SEM） and staged sampling particulate system methods. The variations of oxidation susceptibility,soluble organic fraction（ SOF） components, size distribution and microstructure of particulate with and without FBC were studied. Results showed that the oxidation reaction of particulate matter（ PM） was moved to the low temperature area with the increase of FBC ratio,and the mass fraction of 150 mg / kg for Ce was the optimal blending ratio. The ignition temperatures of PM combustion were reduced by 94℃,131℃,150℃ and 152℃,and the peak temperatures were reduced by 61℃,123℃,146℃ and 161℃ with the four FBC fuels. Before and after adding FBC,the mass fraction of SOF in PM sample were 29. 6% and 24. 1%,respectively. Compared with pure diesel PM sample,the high number of carbon atoms in SOF was decreased, and the polycyclic aromatic hydrocarbons（ PAHs） were decreased by 49. 2%. For FBC particle sample the particle sizes were moved towards small size direction,the peak number concentration of accumulation modal particle was decreased by 14. 4%,the peak number concentration of nuclear modal particle was increased by 8. 9%,and the peak mass concentration was decreased by 14. 5%. FBC particle sample,which had porous sponge morphology and low bonding degree,contained 1. 23% of Ce element.