Sizes, graphitic structures and fractal geometry of light-duty diesel engine particulates
Sizes, graphitic structures and fractal geometry of light-duty diesel engine particulates
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DOI：
10.4271/2003-01-3169
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发表时间：
2003-10
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影响因子：
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通讯作者：
Kyeong-Ook Lee;Jinyu Zhu;S. Ciatti;Ahmet Yozgatligil;M. Choi
中科院分区：
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作者：
Kyeong-Ook Lee;Jinyu Zhu;S. Ciatti;Ahmet Yozgatligil;M. Choi
轻型柴油发动机颗粒物的形态、尺寸、内部微观结构和分形几何特征被表征。采用热泳采样系统直接从 1.7 升涡轮增压共轨直喷柴油发动机的排气歧管收集颗粒物。然后使用高分辨率透射电子显微镜 (TEM) 和图像处理/数据采集系统对在不同发动机运行条件下收集的颗粒样品进行分析。结果显示，在 675 rpm（空转）至 4000 rpm 和 0% 至 100% 负载的整个发动机运行条件下，平均初级粒径 (dp) 和回转半径 (Rg) 范围分别为 19.4 nm 至 32.5 nm 和 77.4 nm 至 134.1 nm。研究还表明，对颗粒形成敏感的其他重要参数，例如废气再循环（EGR）率、当量比和温度，对颗粒尺寸有显着影响。在较高的 EGR 率、较高的当量比（富含燃料）和较低的排气温度下测量到较大的初级颗粒。分形维数 (D{sup f}) 的测量范围为 1.5 - 1.7，小于我们之前研究中重型直喷柴油发动机颗粒物的测量值。这一发现意味着本研究中使用的轻型柴油发动机产生更多拉伸的链状颗粒，而重型柴油发动机排放更多的球形颗粒。在高 TEM 放大倍数下观察柴油颗粒的微观结构，并通过拉曼光谱仪进一步分析。拉曼光谱揭示了在高发动机负载下产生的颗粒的原子结构，这与典型石墨的原子结构相似。« less
The particulate matter of a light-duty diesel engine was characterized in its morphology, sizes, internal microstructures, and fractal geometry. A thermophoretic sampling system was employed to collect particulates directly from the exhaust manifold of a 1.7-liter turbocharged common-rail direct-injection diesel engine. The particulate samples collected at various engine-operating conditions were then analyzed by using a high-resolution transmission electron microscope (TEM) and an image processing/data acquisition system. Results showed that mean primary particle diameters (dp), and radii of gyration (Rg), ranged from 19.4 nm to 32.5 nm and 77.4 nm to 134.1 nm, respectively, through the entire engine-operating conditions of 675 rpm (idling) to 4000 rpm and 0% to 100% loads. It was also revealed that the other important parameters sensitive to the particulate formation, such as exhaust-gas recirculation (EGR) rate, equivalence ratio, and temperature, affected particle sizes significantly. Bigger primary particles were measured at higher EGR rates, higher equivalence ratios (fuel-rich), and lower exhaust temperatures. Fractal dimensions (D{sup f}) were measured at a range of 1.5 - 1.7, which are smaller than those measured for heavy-duty direct-injection diesel engine particulates in our previous study. This finding implies that the light-duty diesel engine used in this study produces more stretched chain-likemore » shape particles, while the heavy-duty diesel engine emits more spherical particles. The microstructures of diesel particulates were observed at high TEM magnifications and further analyzed by a Raman spectroscope. Raman spectra revealed an atomic structure of the particulates produced at high engine loads, which is similar to that of typical graphite.« less