柴油和生物柴油喷雾射流反应流中碳烟颗粒的采样诊断研究

Vehicle particulate emission is becoming more and more serious due to the rapid increase in on-road vehicles in China, thus requiring a complete understanding of the particulate formation mechanism. In this project, by using a constant-volume bomb, the experimental sampling investigation of particulate matter (PM) formed in reacting fuel spray (diesel and biodiesel) under high temperature and pressure conditions will be performed. Firstly, the fuel spray behavior and the successive combustion process in the constant-volume bomb will be investigated to elucidate the effect of flame structure and lift-off length on the formation and spatial distribution of PM formed in the reacting spray. And then, the PM generated in the reacting spray will be sampled and then analyzed with the help of various particle characterization techniques in order to reveal the particle physicochemical characteristics as well as the evolution history of the nanostructure and morphology of the PM sample. Then, to clarify the forces between individual soot particles and their contribution to the agglomeration mechanism of soot, an experimental investigation into the agglomeration mechanism and the intrinsic mechanical properties of the PM sample will be done. At last, polycyclic aromatic hydrocarbon (PAH) adsorbed in the PM sample surface will be extracted and analyzed to elucidate the mechanism of PAH formation and the evolution history of PAH during the combustion process. The results of the current study is helpful to the development of the advanced low temperature combustion concepts and of the technical approaches which can reduce diesel PM emissions. This study has theoretical significance and also practical use for the development of advanced diesel combustion concepts, and also for the exploration of technical approaches which can reduce the PM emission efficiently.

随着我国机动车保有量的不断增加，机动车颗粒物的排放污染问题愈发严重，这就需要对颗粒物生成的内在机制有更深入的了解。本研究借助定容燃烧弹，对高环境温度和压力下柴油和生物柴油喷雾反应流中颗粒物进行采样研究。本课题首先对两种燃料的喷雾燃烧特性进行研究，以求揭示出火焰结构和火焰浮起长度对碳烟生成及空间分布的影响。在此基础上对燃烧喷雾中的颗粒进行采样并对样品进行理化分析表征，从而进一步阐明燃油喷雾射流中碳烟颗粒的纳观结构、表观形貌的演化发展历程及其理化属性。为了澄清颗粒间相互作用力对颗粒凝结团聚机制的贡献及其影响因素，本课题对碳烟凝聚态絮状颗粒物团聚机制及力学属性进行了实验研究。 最后，通过对采样颗粒物挥发性有机成分中多环芳香烃的提取及分析检测，揭示采样碳烟颗粒吸附的多环芳香烃的生成特性及其随燃烧过程发展的演化规律。本研究对发展柴油机低温燃烧理论，探索降低颗粒排放的技术途径有重要价值。

随着我国机动车保有量的不断增加，机动车颗粒物的排放污染问题愈发严重，这就需要对颗粒物生成的内在机制有更深入的了解。本研究借助定容燃烧弹，对高环境温度和压力下柴油喷雾反应流中颗粒物进行采样研究。本课题首先对柴油的喷雾燃烧特性进行研究，以揭示出火焰结构和火焰浮起长度对碳烟生成及空间分布的影响。在此基础上对燃烧喷雾中的颗粒进行采样并对样品进行理化分析表征，从而进一步阐明燃油喷雾射流中碳烟颗粒的纳观结构、表观形貌的演化发展历程及其理化属性。为了澄清颗粒间相互作用力对颗粒凝结团聚机制的贡献及其影响因素，本课题对碳烟凝聚态絮状颗粒物团聚机制及力学属性进行了实验研究。 本研究对发展柴油机低温燃烧理论，探索降低颗粒排放的技术途径有重要价值。.本研究的重要成果之一是对实验室已有的定容燃烧弹进行了改造，在定容燃烧弹的金属堵头上加开了螺纹孔，以便于采样探针的安装与固定。接着在此基础上设计制作了定容燃烧弹专用的采样探针。采样探针分为两种，一种为电镜铜网专用采样探针，另一种为硅片专用采样探针。电镜铜网采样探针适用于低油量下对喷雾燃烧射流火焰中碳烟颗粒的采集，硅片专用采样探针适用于高油量下对碳烟颗粒的采集。以此搭建了可以适用于高温高压火焰中生成碳烟颗粒的采样系统。在碳烟颗粒图像的处理方面，利用MATLAB软件编写了实用的图片处理程序。图像处理过程分为6个步骤：图像规格化处理、求取方向图、图像分割、图像增强、图像二值化和图像细化。图像规格化是将指纹图像的灰度变化调 整到一个统一的标准，从而使后续处理具有相同的标准；求取方向图是后续工作必不可少的一步；图像分割是将图像的前景区域和背景区域区分开，使后续处理能够集中于有效区域；图像增强是指按特定的需要突出图像中的某些信息，同时削弱或去除某些不需要的信息；二值化是将形貌图像由纹理灰度变化的图像变成黑白两色的图像；图像细化是将二值化后的图像进行细化，以获取微粒的微晶碳层。