The particle, liquid and gaseous phase characteristics of PAHs in diesel bus exhaust on dynomometer
| Autor: | Tzu-Chieh Lin, 林資傑 |
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| Rok vydání: | 2008 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 96 Exhaust emission tests of diesel vehicles mostly focus on particulate and gaseous pollutants in Taiwan. Measurements of PAHs from diesel vehicle emissions are not included. Studies on liquid phase PAHs are still lacking. Moreover, application of sampling apparatus is restricted by its large volume, high cost and complexity. A sampling apparatus of diesel vehicle exhaust was designed in this study to achieve the objective of sampling solid, liquid and gaseous phase PAHs in exhaust emissions from diesel buses. Effectiveness assessment and the characteristics of three phases PAHs were investigated as well. One representative apparatus would be culled from the three apparatus designed in this study. The analytical results indicate that the apparatus can collect three phases PAHs in exhaust emissions. Besides, they are portable and their performances are stable. A chassis dynamometer was used in this study to simulate the driving patterns of buses in the sampling procedures. PAHs concentrations in exhaust emissions from buses with catalyst particulate filters were observed to be lower. As discussing the characteristics of three-phase PAHs, 3-ring compounds account for the largest proportion of solid phase PAHs. 2-ring and 3-ring compounds account for the largest proportion of liquid phase PAHs. For gas phase PAHs, 2-ring compounds account for most proportion. Low-molecular-weight PAHs mostly exist as gas phase but high-molecular-weight ones exist as solid phase mainly. The proportion of high-molecular-weight compounds in solid phase PAHs and the proportion of low-molecular-weight compounds in gas phase PAHs exhibit increasing trends with the increase of engine loading. Henry’s Law was applied to investigate the PAHs transfer between liquid and gaseous phases. As bus exhaust just emits, low-molecular-weight PAHs would vaporize into gas phase, then solute in liquid phase and achieve the stabilization finally. However, middle-molecular-weight PAHs would solute in liquid phase immediately and achieve the stabilization slowly. According to emission factors of buses on different driving patterns, they emit the most pollutants at the speed of 20 km/hr with no-loading. Pollutants emit secondly at the speed of 40 km/hr with no-loading and at idle speed. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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