The Morphology and Fractal analysis of diesel soot particles
Date Issued
2004
Date
2004
Author(s)
Lai, Yen-Chiu
DOI
zh-TW
Abstract
We use a dynamometer to simulate a diesel engine in order to produce diesel soot particles. Size, morphology, hurst coefficient and fractal dimension of the diesel soot aggregates generated from dynamometer were investigated with scanning electron microscopy (SEM) and fractal model analysis.
The size distribution of primary particles derived from SEM is about 10∼100 nm at engine speed 2900, 1740 and 1160 rpm. The shape of the primary particles is spherical. A lot of aggregates are also observed in the SEM micrographs. These aggregates are formed by condensation or aggregation of primary particles. The SEM images show that the aggregates are irregular in shape.
The characteristics of fractal model were studied in this research. The fractal properties of images were the same when the brightness of them was changed. The hurst coefficients of two SEM images become more closer when the chosen grids of two images are getting more proportional to their image scales. Additionally, the scales of SEM images were adjusted with software. The fractal property of images didn’t change as the images were magnified, but the fractal property changed as the images were minified.
Fractal properties of diesel soot aggregates were determined from SEM images by fractal model. The hurst coefficient of diesel soot aggregates is about 0.194∼0.374 at different engine speed and the mean fractal dimension is 1.716. It indicates that the fractal dimension is independent of the operation conditions of diesel engine.
The particles sampled from two roadsides and one forest were also investigated by SEM and fractal model. The results show that the particles at 10∼100 nm agree well with diesel soot in morphology and fractal dimension. Therefore, it indicates that these particles are possible to be generated from diesel vehicles.
Subjects
碎形維度
顯微影像
黑煙
柴油
聚集體
morphology
diesel
fractal dimension
soot
aggregate
Type
thesis
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