| dc.description.abstract | Motorcycle is the most popular transportation tool in Taiwan. Periodic emission test is performed to ensure that all motorcycles conforms to EPA regulations governing emissions. So far, the particulate matter is not included in the emission test. Therefore, the main purpose of the present study is to develop a precise, rapid and stable aerosol sampling and measurement method for motorcycle emission. This study also aims to evaluate the effectiveness of the current motorcycle emission test program.
The motorcycle exhaust exiting the tailpipe is drawn into a sampling train with a PM2.5 separator which is immersed in an iced bath. The cooled exhaust is then either measured directly by gas/PM sensors, or through a diluter if the concentration is too high for the sensors. The gas (CO, HC, CO2, SO2, VOC, NOX, O2) and particulate (opacity, black carbon, particle number, particle mass, size distribution) real-time emissions are evaluated in different driving cycle (acceleration, fixed, idle and urban driving cycle).
The gas pollutants are mainly affected by the rate of acceleration, and show a slight increase in high speed. The particle concentration increases with increasing acceleration rate and speed. The oxygen sensor failure causes unstable air-fuel ratio, and the engine operation apparently is not in closed loop, causing the concentrations of CO, NOX and HC to rise. An increase in the exhaust valve clearance results in higher HC and particulate concentrations, probably due to the leaking of unburned oil and gas. Particle number increases with increasing speed. The black carbon and PM meters show valid measurement values only when the speed is high. Therefore, they might be ideal for screening heavy polluters. The inspection and maintenance items should be re-evaluated to identify the major factors that might cause higher emissions. The higher inspecting frequency of oxygen sensor and valve clearance is recommended. Yet, the emission standards are too loose based on the tests conducted in this work. | en_US |