摘要
以一辆国Ⅴ柴油公交车为研究对象,试验研究了该车燃用不同比例废弃油脂制生物柴油‒柴油混合燃料在中国典型城市公交循环(CCBC)下颗粒物质量、颗粒数量、粒径分布与颗粒微观形貌特征。结果表明:随着生物柴油比例的增加,排放的尾气颗粒物质量和固态颗粒数量减小;燃用生物柴油的尾气颗粒典型微观结构与柴油的类似,由多个准球状基本碳粒子堆积而成,呈链状、枝状等不规则结构;与燃用柴油的相比,燃用生物柴油的尾气颗粒基本碳粒子粒径较小,分形维数较大,空间结构更紧密;燃用生物柴油的尾气颗粒在团聚处更易被氧化, 颗粒的分形维数和基本碳粒子直径随着氧化进行而增大;燃用柴油的尾气颗粒的氧化主要以最外壳边界碳层湮灭为主,颗粒分形维数、基本碳粒子直径随着氧化进行而减小。
关键词
机动车排放的一次颗粒物和二次颗粒物占我国重点城市群大气颗粒物的约30
我国柴油公交车保有量约为12.06万辆,占公交车总量的17.4
国内外学者以发动机为研究对象,开展了生物柴油对柴油机尾气颗粒排放特性及微观形貌的影响研究,分析了生物柴油对柴油机尾气颗粒物质量和颗粒数
以车辆为研究对象,开展生物柴油对柴油车尾气颗粒排放特性及微观形貌影响研究,可更好地反映实际行驶过程中车辆的颗粒排放特性, 因此受到国内外学者的关注。例如,楼狄明等分析了生物柴油公交车尾气颗粒数量与粒径分布特
以一辆国Ⅴ柴油公交车为研究对象,在重型底盘测功机上运行中国典型城市公交循环(CCBC),分析燃用柴油、体积比为20%的废弃油脂制生物柴油‒柴油混合燃料以及100%废弃油脂制生物柴油公交车尾气颗粒物质量、颗粒数量、粒径分布与颗粒微观形貌特征,讨论氧化温度对车辆尾气颗粒微观形貌的影响,以综合评价废弃油脂制生物柴油对国Ⅴ柴油公交车尾气颗粒排放特征、微观形貌及氧化特性的影响。
试验样车为一辆满足国Ⅴ排放标准的柴油公交车,安装高压共轨六缸增压中冷柴油机,试验车辆主要技术参数如
试验设备包括MAHA‒AIP重型底盘测功机、Semtech‒Ecostar车载尾气分析仪、 芬兰Dekeati公司的细颗粒取样稀释系统FPS‒4000、美国TSI公司的EEPS3090颗粒物粒径谱仪、管式炉、美国FEI公司的场发射透射电子显微镜。试验装置示意图如

图1 试验测试系统示意图
Fig.1 Schematic diagram of experimental apparatus
试验时将公交车固定在底盘测功机上,根据车辆最大总质量的70%加载,通过滑行确定阻力系数,重复3次。试验循环为CCBC,循环运行时间为1 314 s,行驶里程为5.89 km,平均时速为16.16 m·
燃用B0、B20和BD100国Ⅴ柴油公交车排放的尾气颗粒物质量、23~2 500 nm固态颗粒数量如
由
燃用B0、B20、BD100国Ⅴ柴油公交车的尾气颗粒粒径分布如

图2 燃用B0、B20和BD100国Ⅴ柴油公交车尾气颗粒粒径分布
Fig.2 Size distribution of particles from China Ⅴ diesel bus fueled with B0, B20 and BD100

图3 燃用B0、B20和BD100国Ⅴ柴油公交车尾气颗粒典型微观形貌
Fig.3 Typical microscopic morphology of particles from China Ⅴ diesel bus fueled with B0, B20 and BD100
由
颗粒的分形维数可反映其几何结构的不规则性以及颗粒团聚体中基本碳粒子间疏密程度,分形维数越大,颗粒的结构越紧密,组成颗粒的基本碳粒子之间重叠度越
(1) |
式中:为结构系数;为颗粒回旋半径;为基本碳粒子平均半径;为分形维数;为颗粒中所含基本碳粒子数量。
利用得到的颗粒透射电子显微镜图像,可提取颗粒回旋半径和基本碳粒子数量N
由
燃用B0、B20和BD100国Ⅴ柴油公交车的尾气颗粒基本碳粒子微观结构如

图4 燃用B0、B20和BD100国Ⅴ柴油公交车尾气颗粒基本碳粒子微观结构
Fig.4 Microstructure of basic carbon particles from China Ⅴ diesel bus fueled with B0, B20 and BD100

图5 燃用B0、B20和BD100国Ⅴ柴油公交车尾气颗粒基本碳粒子粒径分布
Fig.5 Size distribution of basic carbon particles from China Ⅴ diesel bus fueled with B0, B20 and BD100
由
柴油公交车颗粒氧化过程中,其分形维数、基本碳粒子结构等特征发生变化。

图6 不同氧化温度下燃用B0、B20和BD100国Ⅴ柴油公交车尾气颗粒分形维数
Fig.6 Fractal dimension of particls from China Ⅴ diesel bus fueled with B0, B20 and BD100 at different oxidation temperatures
在氧化过程中颗粒的结构变化主要是由基本碳粒子的碰撞凝结、表面生长以及氧化湮灭共同作用

图7 不同氧化温度下燃用B0、B20和BD100国Ⅴ柴油公交车尾气颗粒基本碳粒子微观结构
Fig.7 Microstructure of basic carbon particles from China Ⅴ diesel bus fueled with B0, B20 and BD100 at different oxidation temperatures
由
综合
燃用B0、B20和BD100国Ⅴ柴油公交车尾气颗粒基本碳粒子不同氧化温度下的平均粒径如

图8 不同氧化温度下燃用B0、B20和BD100国Ⅴ柴油公交车尾气颗粒基本碳粒子平均粒径
Fig.8 Average size of basic carbon particles from China Ⅴ diesel bus fueled with B0, B20 and BD100 at different oxidation temperatures
(1)随着生物柴油混合比例增加,国Ⅴ柴油公交车排放的尾气颗粒中核膜态颗粒数量增大,积聚态颗粒数量减少,颗粒物质量及固态颗粒排放数量降低。
(2)燃用生物柴油国Ⅴ柴油公交车尾气颗粒典型微观结构与燃用柴油的类似,由多个准球状的基本碳粒子组成,主要为链状、枝状等不规则结构;燃用生物柴油的尾气颗粒更倾向于产生规则的圆球状基本碳粒子,基本碳粒子平均粒径较小,分形维数较大,颗粒几何结构更紧密。
(3)燃用B0国Ⅴ柴油公交车尾气颗粒的氧化主要以外壳边界碳层湮灭为主,燃用BD100的尾气颗粒的氧化主要以衔接处碳层氧化为主。随着氧化温度升高,燃用B0的尾气颗粒分形维数和基本碳粒子平均粒径降低;燃用BD100的尾气颗粒分形维数和基本碳粒子平均粒径增大;燃用B20的尾气颗粒分形维数和基本碳粒子随氧化温度的升高呈先增大后减小的变化趋势。
作者贡献声明
胡志远:制定研究方案,指导试验人员开展试验。
罗 军:试验操作,试验数据分析。
林骠骑:试验操作。
谭丕强:论文修改。
楼狄明:论文修改。
王 忠:论文修改。
参考文献
李佳璇.浅析机动车尾气与煤炭燃烧对我国雾霾的影响[J].广州化工,2020,48(14):120. [百度学术]
LI Jiaxuan. Influence of motor vehicle exhaust and coal combustion on Chinese haze[J]. Guangzhou Chemical Industry,2020,48(14):120. [百度学术]
张方娟,杨东红,许颖,等.汽车尾气排放与雾霾天气的相关性研究[J].河南科技,2020(5):146. [百度学术]
ZHANG Fangjuan, YANG Donghong, XU Ying, et al. Research on the correlation between automobile exhaust emission and haze weather[J]. Journal of Henan Science and Technology,2020(5):146. [百度学术]
中华人民共和国生态环境部. 2019中国环境状况公报[EB/OL].[2020-06-02]. http://www.mee.gov.cn/hjzl/sthjzk/zghjzkgb/202006/P020200602509464172096.pdf. [百度学术]
Ministry of Ecology and Environment of the People’s Republic of China. China ecological environment status bulletin 2019 [EB/OL]. [2020-06-02]. http://www.mee.gov.cn/hjzl/sthjzk/zghjzkgb/202006 /P020200602509464172096.pdf. [百度学术]
中华人民共和国交通运输部. 2019年交通运输行业发展统计公报[J].交通财会,2020(6):86. [百度学术]
Ministry of Transport of the People’s Republic of China. Statistical bulletin on the development of transportation industry in 2019[J]. Finance & Accounting for Communications,2020(6):86. [百度学术]
涂先库.城市公交柴油化面临的排放问题及对策[J].宁波工程学院学报,2005(4):31. [百度学术]
TU Xianku. Emission problems and controlling measures of urban bus dieselization[J]. Journal of Ningbo University of Technology,2005(4):31. [百度学术]
中华人民共和国生态环境部. 2020年中国移动源环境管理年报:第Ⅰ部分 机动车排放情况[J].环境保护,2020,48(16):47. [百度学术]
Ministry of Ecology and Environment of the People’s Republic of China. China mobile source environmental management annual report in 2020: Part Ⅰ the situation of vehicle emission[J]. Environmental Protection,2020,48(16):47. [百度学术]
赵光辉,佟华芳,李建忠,等.生物柴油产业开发现状及应用前景[J].化工中间体,2013,10(2):6. [百度学术]
ZHAO Guanghui, TONG Huafang, LI Jianzhong, et al. Industrial development status and application prospects of biodiesel[J]. Chemical Intermediate,2013,10(2):6. [百度学术]
TOMPKINS B T, SONG H, BITTLE J, et al. Biodiesel later-phased low temperature combustion ignition and burn rate behavior on engine torque[R]. Detroit: SAE, 2012. [百度学术]
吴刚,江国和,杨智远,等.燃用生物柴油对柴油机颗粒生成和排放特性研究进展[J].环境科学研究,2019,32(11):1809. [百度学术]
WU Gang, JIANG Guohe, YANG Zhiyuan, et al. Particulate matter generation and emission characteristics of diesel engine fueled by biodiesel[J]. Research of Environmental Sciences,2019,32(11):1809. [百度学术]
楼狄明, 孔德立, 强蔷, 等. 国Ⅴ柴油机燃用柴油/生物柴油排放性能试验[J]. 农业机械学报, 2014, 45(9):25. [百度学术]
LOU Diming, KONG Deli, QIANG Qiang, et al. Emission experiment on a Chinese Ⅴ diesel engine fueled with diesel/biodiesel[J]. Transactions of the Chinese Society for Agricultural Machinery, 2014, 45(9):25. [百度学术]
DI I S, MAGNO A, MANCARUSO E, et al. Effect of diesel/RME blend on particle emissions from a diesel engine for quadricycle vehicle[R]. Detroit: SAE, 2014. [百度学术]
CHIATTI G, CHIAVOLA O, PALMIERI F. Impact of waste cooking oil in biodiesel blends on particle size distributions from a city-car engine[J]. Journal of the Energy Institute, 2016, 91:262. [百度学术]
BORHMAN A L, SONG J, ALAM M. Impact of biodiesel blending on diesel soot and the regeneration of particulate filters[J]. Energy & Fuels, 2005,19(5):1857. [百度学术]
张小玉,马志豪,马凡华,等.生物柴油掺混比例对柴油机颗粒排放微观特性的影响[J].汽车安全与节能学报,2012,3(2):179. [百度学术]
ZHANG Xiaoyu, MA Zhihao, MA Fanhua, et al. Influence of biodiesel/diesel blends proportions on emission particle microscopic characteristics of diesel engines[J]. Journal of Automotive Safety and Energy,2012,3(2):179. [百度学术]
周小强. 柴油机燃用调合生物柴油颗粒物排放特性的研究[D]. 镇江:江苏大学, 2017. [百度学术]
ZHOU Xiaoqiang. Study on emission characteristics of particulate matter emitted from diesel engine fueled with blending biodiesel[D]. Zhenjiang: Jiangsu University, 2017. [百度学术]
赵小明. 低掺烧比生物柴油排放及颗粒物理化特性研究[D]. 镇江:江苏大学, 2016. [百度学术]
ZHAO Xiaoming. Experimental studies on emission and the physicochemical characteristics of particulates for diesel engine with low proportion biodiesel[D]. Zhenjiang: Jiangsu University, 2016. [百度学术]
张宇,王忠,李瑞娜,等.柴油机燃用不同燃料颗粒微观形貌与氧化特性分析[J].车用发动机,2019(6):58. [百度学术]
ZHANG Yu, WANG Zhong, LI Ruina, et al. Analysis of on micro-morphology and oxidation characteristics of particles for diesel engine fueled with different fuels[J].Vehicle Engine,2019(6):58. [百度学术]
杜家益,常真真,张登攀,等. EGR对生物柴油颗粒物微观结构及官能团的影响[J].内燃机学报,2020,38(2):140. [百度学术]
DU Jiayi, CHANG Zhenzhen, ZHANG Dengpan, et al. Influence of EGR on microcosmic structure and functional groups of particulate matters out of a diesel-biodiesel blend engines[J]. Transactions of CSICE,2020,38(2):140. [百度学术]
楼狄明,赵成志,徐宁,等.不同排放标准公交车燃用生物柴油颗粒物排放特性[J].环境科学,2017,38(6):2301. [百度学术]
LOU Diming, ZHAO Chengzhi, XU Ning, et al. Emission characteristics of particulate matter from diesel buses meeting different China emission standards fueled with biodiesel[J]. Environmental Science,2017,38(6):2301. [百度学术]
胡志远,章昊晨,谭丕强,等.国Ⅴ公交车燃用生物柴油的颗粒物碳质组分排放特性[J].中国环境科学,2018,38(8):2921. [百度学术]
HU Zhiyuan, ZHANG Haochen, TAN Piqiang, et al. Emission of carbonaceous components from a bus fueled with waste cooking oil based biodiesel blends[J]. China Environmental Science,2018,38(8):2921. [百度学术]
胡志远,章昊晨,谭丕强,等.生物柴油公交车颗粒物可溶有机组分和多环芳烃排放[J].同济大学学报(自然科学版),2019,47(7):1046. [百度学术]
HU Zhiyuan, ZHANG Haochen, TAN Piqiang, et al. Emission characteristics of soluble organic fraction and polycyclic aromatic hydrocarbons from a diesel bus fueled with waste cooking oil-based biodiesel blends[J]. Journal of Tongji University(Natural Science),2019,47(7):1046. [百度学术]
高章. 基于底盘测功机的公交车整车排放和油耗测试研究[D].武汉:武汉理工大学,2011. [百度学术]
GAO Zhang. Research of the test for complete-vehicle emission and fuel consumption of the bus by chassis-dynamometer[D].Wuhan: Wuhan University of Technology, 2011. [百度学术]
UTLU Z,KOCAK M S. The effect of biodiesel fuel obtained from waste frying oil on direct injection diesel engine performance and exhaust emissions[J]. Renew Energy,2008, 33(8): 1936. [百度学术]
赵杰,韩维维,胡志远.燃用生物柴油公交车的颗粒物排放特性[J].内燃机与配件,2019(22):36. [百度学术]
ZHAO Jie, HAN Weiwei, HU Zhiyuan. Emission characteristics of particulate matter from buses fueled with biodiesel [J]. Internal Combustion Engine & Parts, 2019(22):36. [百度学术]
夏群,杜家益,张登攀,等.调合生物柴油发动机颗粒物氧化特性研究[J].广西大学学报(自然科学版),2016,41(6):1824. [百度学术]
XIA Qun,DU Jiayi,ZHANG Dengpan, et al. Research on oxidative characteristics of particulate matter emitted from diesel/biodiesel engine[J]. Journal of Guangxi University (Natural Science Edition),2016,41(6):1824. [百度学术]
李铭迪, 赵琛, 许广举, 等. 柴油/碳酸二甲酯燃烧颗粒的微观结构和分形特征[J]. 环境科学研究, 2016, 29(6):900. [百度学术]
LI Mingdi, ZHAO Chen, XU Guangju, et al. Microstructure and fractal characteristic analysis of particulate matter from diesel/DMC combustion[J]. Research of Environmental Sciences,2016,29(6): 900. [百度学术]
SAVIC N, RAHMAN M M, MILJEVIC B, et al. Influence of biodiesel fuel composition on the morphology and microstructure of particles emitted from diesel engines[J]. Carbon, 2016, 104:179. [百度学术]
KOEYLE U, XING Y, ROSNER D E. Fractal morphology analysis of combustion-generated aggregates using angular light scattering and electron microscope images[J]. Langmuir, 1995, 11/12:4848. [百度学术]
瞿磊, 王忠, 李瑞娜, 等.甲醇/生物柴油燃烧颗粒的结构特征研究[J]. 西安交通大学学报, 2016, 50(5):81. [百度学术]
QU Lei, WANG Zhong, LI Ruina, et al. Structural characteristics of methanol/biodiesel combustion particles[J]. Journal of Xi’an Jiaotong University, 2016, 50(5):81. [百度学术]
ZHU J, LEE K O, YOZGATLIGIL A, et al. Effects of engine operating conditions on morphology, microstructure, and fractal geometry of light-duty diesel engine particulates[J]. Proceedings of the Combustion Institute, 2005, 30(2):2781. [百度学术]
HURT R H, CRAWFORD G P, SHIM H S. Equilibrium nanostructure of primary soot particles[J]. Proceedings of the Combustion Institute, 2000, 28(2):2539. [百度学术]
郝斌. 不同燃料对柴油机排气颗粒物的影响研究[D]. 天津:天津大学, 2014. [百度学术]
HAO Bin. Effect of fuel identity on the exhaust particles from diesel engine[D]. Tianjin: Tianjin University, 2014. [百度学术]
LAPUERTA M, MARTOS F J, HERREROS J M. Effect of engine operating conditions on the size of primary particles composing diesel soot agglomerates[J]. Journal of Aerosol Science, 2007, 38(4):455. [百度学术]
WANG H. Formation of nascent soot and other condensed-phase materials in flames[J]. Proceedings of the Combustion Institute, 2011, 33(1):41. [百度学术]
WAL R L V, TOMAESK A J. Soot nanostructure: dependence upon synthesis conditions[J]. Combustion & Flame, 2004, 136(2):129. [百度学术]