Thesis
Characterization of a flow tube photoreactor for simulating diesel exhaust photochemistry in the urban atmosphere
Washington State University
Master of Science (MS), Washington State University
2015
Handle:
https://hdl.handle.net/2376/100769
Abstract
Diesel exhaust is becoming a larger contributor to overall vehicular pollution, and has been shown impact atmospheric SOA and O3 formation. In order to better understand diesel exhaust composition and photochemical aging, a 3200L Teflon-lined cylindrical environmental chamber intended to follow plug-flow principles was constructed. After characterizing flow and mixing, and gradients of concentration, UV, and temperature throughout the chamber, it was found that UV intensities were twice as large as those of ambient summertime intensities, and the chamber was well-mixed. Exhaust was diluted with zero air and injected into the chamber via a Venturi system which drew sample directly from the exhaust stream of an APA 5.5kW diesel generator with no filter, or from a 2004 Chevy Silverado with no catalytic converter. The generator was generally run with 0-20 amp (0-50%) electrical load applied. It was hypothesized that a generator run at ½ of its full electrical output capacity reasonably replicates the exhaust outputs of on-road diesel vehicles. The chamber has [HO] ≈ 1.57x107 molecules/cm3 . Gasoline exhaust was far more concentrated in high-volatility VOCs than the diesel exhaust, but diesel exhaust had concentrations of many low-volatility VOCs that were greater than 10 times what was emitted by the gasoline engine. Therefore diesel exhaust likely plays a larger role in atmospheric SOA formation than gasoline exhaust. When oxidized, sample NO:NO2 ratio inverted and O3 formed. The diesel engine had a smaller NO:NO2 ratio than the gasoline engine, resulting in a lower O3 formation potential. The CO:NOx ratio from the generator was much smaller than literature values for on-road diesel vehicles due to increased NOx emissions and decreased CO emissions. VOC emissions were 2-5 times larger and of differing relative abundances than literature values for on-road diesel vehicles. These data indicate that the generator may not accurately represent on-road diesel vehicle emissions. However, compared to literature data for other diesel generators, this generator behaves normally. The best way to simulate on-road vehicle emissions with the generator is to run it at 50% load
Metrics
2 File views/ downloads
15 Record Views
Details
- Title
- Characterization of a flow tube photoreactor for simulating diesel exhaust photochemistry in the urban atmosphere
- Creators
- Madeline Jo Fuchs
- Contributors
- Bertram Thomas Jobson (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Civil and Environmental Engineering, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525106801842
- Language
- English
- Resource Type
- Thesis