Fractal Dimension and Chemical Composition of Suspended Particulates Emitted from Motorcycles
Date Issued
2006
Date
2006
Author(s)
Hsu, Shih-Wei
DOI
zh-TW
Abstract
This study investigated the hurst coefficient and chemical composition of suspended particulates emitted from motorcycles. The engines of the motorcycles were a dynamometer, two two-stroke motorcycles and six four-stroke motorcycles. Two unleaded gasolines (92 and 95) and three speeds of motorcycle engines (3600, 4600 and 5800 rpm) were conducted using the dynamometer. Size, morphology, hurst coefficient and elemental composition of the particles and aggregates generated from dynamometer were investigated with scanning electron microscopy (SEM) and fractal model analysis. Physical and chemical characteristic information of the motorcycle exhaust particles was built to provide valid evidence to identify the pollution sources. Besides, in order to know the present practical motorcycle exhaust condition, this study sampled and analyzed eight motorcycles, and then compared with diesel cars in morphology, hurst coefficient, and elemental composition respectively.
According to the 105 magnification images, the morphology of aggregates generated from the dynamometer is very similar to that generated from the eight motorcycles. Most of the primary particles is spherical, and the size distribution was from 10 to 50 nm. The size distribution of the aggregates is from 100 to 1000 nm. The hurst coefficient of aggregates generated from the dynamometer is about 0.118∼0.366 at different engine speed and the mean hurst coefficient is 0.242. Besides, the mean hurst coefficient of aggregates generated from the eight motorcycles is about 0.222∼0.292. As to the comparison with the hurst coefficient of the aggregates from different motorcycles, we found that the mean hurst coefficient of the aggregates from four-stroke engines was higher than that from two-stroke engines. With the increases of exhaust, the hurst coefficient did not have a significant difference. In contrast, with the decrease of the rotation speed of the engines, the hurst coefficient would be enhanced. The elemental composition of the single particle were analyzed by EDS. This result indicated that the carbon(11.37~53.41%), oxygen, silicon and aluminum were the major elements in all of the chemical components. Besides, we also discovered that potassium and iron were the elements which weight percentage was below 5%. Moreover, there were some minor elements like sodium, magnesium, calcium, sulfur, tin and chromium.
The hurst coefficient of aggregates generated from the diesel cars is very similar to that generated from the motorcycles. The mean hurst coefficient of aggregates generated from the diesel cars is about 0.194~0.374, and that generated from the motorcycles is about 0.118~0.366. There was a significant difference if we used the weight percentage of carbon component to distinguish the emitted sources of particles. The weight percentage of carbon component of particles emitted from motorcycles was 19.13~33.84%, and that emitted from diesel cars was 46.85~63.47%. If we used the hurst coefficient and elemental composition to judge the particle sources, the rate of accuracy in this research is about 50%, and the particles that couldn’t be distinguished is about 30%. We could improve the rate of accuracy if we used the carbon compostion to judge the particle sources.
Subjects
機車
微粒
碎形參數
化學分析
Motorcycles
Particles
Hurst coefficient
Chemical analysis
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-95-R93541126-1.pdf
Size
23.53 KB
Format
Adobe PDF
Checksum
(MD5):5824da939ee35f68703d817a05d29df9