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SPATIAL AND TIME RESOLVED STUDY OF TRANSIENT PLASMA INDUCED OH PRODUCTION IN QUISCENT CH4-AIR MIXTURES
by
Charles Cathey
A Dissertation Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(ELECTRICAL ENGINEERING)
December 2007
Copyright 2007 Charles Cathey
Object Description
| Title | Spatial and time resolved study of transient plasma induced oh production in quiscent CH4-air mixtures |
| Author | Cathey, Charles |
| Author email | cathey@usc.edu |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Electrical Engineering |
| School | Viterbi School of Engineering |
| Date defended/completed | 2007-08-06 |
| Date submitted | 2007 |
| Restricted until | Unrestricted |
| Date published | 2007-09-19 |
| Advisor (committee chair) | Gundersen, Martin A. |
| Advisor (committee member) |
Steier, William H. Wang, Hai |
| Abstract | This thesis presents an experimental study into the utility of transient plasma ignition (TPI) of hydrocarbon fuel-air mixtures and the basic physics behind said phenomena. Transient plasma has several advantages over traditional spark ignition, consistently demonstrating reductions in ignition delay and extended lean burn capability. It is postulated that high energy electrons generated during the electrical discharge are responsible for electron impact dissociation, ionization, and fragmentation of molecules in the medium resulting in radical formation that drives the combustion process. The experiments described in this thesis illustrate TPI's effects and attempt to understand the underlying physics by looking at transient plasma induced production of radicals, ignition, and flame propagation.; Using optical diagnostic techniques the ability of a transient plasma to populate a cylindrical discharge volume with the hydroxyl radical (OH) is analyzed during combustion of stoichiometric quiescent CH4-air mixtures. Ground state OH production is analyzed using planar laser induced fluorescence (PLIF). Broadband transitions of OH near 309 and 314 nm were also used to monitor transient plasma production of OH* via optical emission spectroscopy (OES). A high speed camera was used to image ignition and flame propagation in the chamber, providing spatial and temporal resolution over the entire combustion event.; Transient plasma successfully ignited the CH4 - air mixture, populating the discharge volume with radicals. Mean OH number densities produced by the discharge were found to reach ~ 4x10^14 molecules - cm^(-3) and decay within 100 µs of the plasma. Ignition under these conditions was found to occur approximately 1 ms after the discharge along the anode, creating a cylindrically expanding flame front. TPI was found to be a truly volumetric ignition source creating multiple ignition kernels whose proximity to the anode is consistent with the region of highest field and thus maximum radical density. Additionally the rapid decay of the initial OH (as seen by the pump beam) with respect to the time of ignition suggests that the anode itself may have an important role in sustaining and enhancing combustion kinetics. |
| Keyword | transient plasma ignition; pulsed power |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Type | texts |
| Legacy record ID | usctheses-m831 |
| Rights | Cathey, Charles |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | http://www.usc.edu/isd/libraries/services/ask_a_librarian/email/ |
| Filename | etd-Cathey-20070919 |
| Archival file | uscthesesreloadpub_Volume14/etd-Cathey-20070919.pdf |
Description
| Title | Page 1 |
| Full text | SPATIAL AND TIME RESOLVED STUDY OF TRANSIENT PLASMA INDUCED OH PRODUCTION IN QUISCENT CH4-AIR MIXTURES by Charles Cathey A Dissertation Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (ELECTRICAL ENGINEERING) December 2007 Copyright 2007 Charles Cathey |
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