引用本文:赵洋,许广举,李铭迪,陈庆樟,王忠,等.柴油机EGR氛围颗粒的空间结构与表面形态分析[J].环境科学研究,2016,29(11):1672-1678.
ZHAO Yang,XU Guangju,LI Mingdi,CHEN Qingzhang,WANG Zhong,et al.Spatial Structure and Surface Morphology of Particles from Diesel Engines Equipped with EGR[J].Reserrch of Environmental Science,2016,29(11):1672-1678.]
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柴油机EGR氛围颗粒的空间结构与表面形态分析
赵 洋1, 许广举1, 李铭迪1, 陈庆樟1, 王 忠2
1.常熟理工学院汽车工程学院, 江苏 常熟 215500 ;2.江苏大学汽车与交通工程学院, 江苏 镇江 212013
摘要:
为揭示EGR(废气再循环)对柴油机颗粒表面形态以及空间结构的影响,针对不同EGR率下产生的柴油机颗粒,采用颗粒粒径分析仪以及X射线小角散射等分析手段,研究了EGR对柴油机排气颗粒粒径、数浓度和质量浓度的影响,分析了颗粒团聚程度、团粒间隙尺寸以及表面形态等参数随EGR率的变化规律.结果表明:随着EGR率从10%增至30%,颗粒数浓度峰值粒径向大粒径方向偏移,粒径在10~50 nm的核模态颗粒数浓度分别降低了14.7%和29.4%;粒径在50~500 nm的积聚态颗粒数浓度分别增加了17.1%和139.4%;总颗粒数浓度也有较大幅度增加,分别增加了4.5%和72.1%.采用EGR后,颗粒的质量分形维数和表面分形维数分别增加了12.1%和18.2%,表明EGR会使颗粒的质量分布不均匀,表面粗糙程度增加.随着EGR率的增加,颗粒的团粒间隙分布有明显差异,EGR率为0时的团粒间隙尺寸主要分布在8~11 nm,EGR率为30%时的团粒间隙尺寸主要分布在4~6 nm,表明EGR可在总体上降低团粒间隙尺寸和数浓度,增加了颗粒的团聚程度和空间结构的紧密程度.研究结果对于拓宽EGR的工况使用范围、提高DPF等后处理装置的工作效率、进一步降低柴油机的NOx和颗粒排放具有重要意义.
关键词:  柴油机  颗粒  废气再循环  颗粒结构
DOI:
分类号:
基金项目:国家自然科学基金项目(51506011);江苏省高校自然科学研究面上项目(15KJB470001);苏州市应用基础研究项目(SYG201515)
Spatial Structure and Surface Morphology of Particles from Diesel Engines Equipped with EGR
ZHAO Yang1, XU Guangju1, LI Mingdi1, CHEN Qingzhang1, WANG Zhong2
1.Department of Automobile Engineering, Changshu Institute of Technology, Changshu 215500, China ;2.School of Automobile and Traffic Engineering, Jiangsu University, Zhenjiang 212013, China
Abstract:
Abstract: By reintroducing the exhaust gas into the cylinder, exhaust gas recirculation(EGR) reduces the oxygen concentration of the gas mixture, the maximum combustion temperature and the amount of NOx emissions.However, EGR has an adverse impact on particle emissions from diesel engines. To understand the effects of exhaust gas recirculation(EGR) on the spatial structure and surface morphology of diesel particles, an engine exhaust particle sizer and small-angle X-ray scattering were used to analyze particles collected under different EGR rates(0%,10% and 30%). The results showed that the size distribution of particle number shifted to the right, and the value of the nucleation mode(10-50 nm) peak significantly decreased with the EGR rate increased by 14.7% and 29.4%, respectively.However, the value of the accumulation mode(50-500 nm) peak increased by 17.1% and 139.4% respectively, and the total particle number concentration also increased by 4.5% and 72.1%. The results of small-angle X-ray scattering showed that the quality fractal dimension and surface fractal dimension of the particles all increase with EGR rate increase, which increased by 12.1% and 18.2% and indicated that the distribution of particle quality was more uneven and the surfaces were rougher. Besides, with EGR rate increasing, the distribution of the particle aggregate gap was obviously different. The size of the aggregate gap was mainly distributed between 8-11 nm when EGR rate was 0%, while the size of the aggregate gap decreased to 4-6 nm when EGR rate increased to 30%, which indicated that with EGR rate increasing, the number and size of aggregate gap both had a significant decrease, the particle from diesel engines with exhaust gas inhaled had a higher reunite degree, and the space structure was more compact. The results about the spatial structure and surface morphology of particle have important meaning for broadening the scope of EGR conditions and improving the work efficiency of aftertreatment equipment(DPF,DOC and POC). In addition, the results provide relevant basic data and new reference for the further reduction of particle emissions from diesel engines.
Key words:  diesel engine  particle  exhaust gas recirculation  particle structure