摘要
为深入了解废气再循环(EGR)对颗粒的作用机理,分析EGR中不同废气成分(N2、CO2)对颗粒微观结构的影响规律以及形成原因,采用透射电镜以及图像处理软件(Digital Micrograph)对颗粒的微观形貌以及基本碳粒子层面间距、微晶尺寸等结构特征参数进行了分析。结果表明,与通入EGR废气相比,相同EGR率下,只通入CO2时的颗粒主要呈链状结构,基本碳粒子的碳层排列无序性增加,外壳石墨晶体结构含量有所降低,内核与外壳的边界变得模糊;基本碳粒子层面间距有所增大,微晶尺寸有所降低,弯曲度最大,分形维数最小;只通入N2时的颗粒主要呈簇状结构,堆积更加明显,各基本碳粒子之间结合更加紧密,基本碳粒子内核更为明显,外壳的石墨晶体结构有所增加;基本碳粒子层面间距有所减小,微晶尺寸有所增加,弯曲度最小,分形维数最大;说明增加EGR废气成分中的CO2含量有利于提高颗粒自身的氧化能力,使微晶结构的有序性减弱,石墨化程度降低,只通入N2时的颗粒结构更为紧密,只通入CO2时的颗粒结构较为疏松。
Morphology and microstructure of particulates with the application of different gas compositions in EGR were analyzed by using transmission electron microscope and image processing software（ Digital Micrograph）. The results show that the particulates with the application of CO2 mainly have the chain structure. The disorder degree of carbon layer in elementary particulate is higher and the content of graphitic crystalline structure in shell is less than those particulates with the application of EGR. Besides,the fringe separation distance has a significant increase. The average fringe length has a significant decrease; the tortuosity is the biggest and the fractal dimension is the smallest. The particulates with the application of N2 mainly have the stone clusters; the elementary particulate integrated more tightly; the core of elementary particulate is more obvious and the content of graphitic crystalline structure in shell is less than those particulates with the application of EGR. Besides that,the fringe separation distance has a significant decrease; the average fringe length has a significant increase; the tortuosity is the smallest and the fractal dimension is the biggest. Those indicate that the structure of particular with the application of N2 is more tightness than those with the application of CO2,and increasing of the content of CO2 in EGR can improve the oxidation ability of particulate and decrease the disorder degree of carbon layer.
出处
《农业机械学报》
EI
CAS
CSCD
北大核心
2015年第7期280-285,共6页
Transactions of the Chinese Society for Agricultural Machinery
基金
国家自然科学基金资助项目(51376083)
江苏省高校自然科学基金资助项目(13KJA470001)
江苏省2013年度普通高校研究生科研创新计划资助项目(CXZZ13-0672)
江苏省2014年度普通高校研究生科研创新计划资助项目(KYLX-10635)
2011年江苏高校优势学科建设工程资助项目(PAPD)
关键词
柴油机
废气再循环
气体成分
颗粒
结构特征
Diesel engine Exhaust gas recirculation Gas composition Particulates Structural feature
