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Dissertation
Development of a sensitive and selective laser diagnostic technique for measuring paramagnetic species
Doctor of Philosophy (Ph.D.), Drexel University
Jun 2012
DOI:
https://doi.org/10.17918/etd-3797
Abstract
Design of advance combustion systems that are efficient and environmentally friendly increasingly incorporate numerical simulations of the reaction progress, simulations that require chemical kinetic models applicable over the entire range of reaction conditions. A deficiency of these models is in the low and intermediate temperature regime that is controlled by the hydroperoxy radical (HO2), alkyl peroxy radical (RO2), and hydroxyl radical (OH). Fundamental understanding of the underlying fuel oxidation chemistry in this regime is required to extend and improve these combustion models. A complication in making such measurements in combustion systems is the large number of strongly absorbing stable species, such as CO₂ and H₂O, that mask the absorption features of HO2 and RO2 radicals. Therefore, quantitative measurement of the small peroxy radicals requires the implementation of powerful diagnostics that are sensitive and selective enough for application in complex reacting environments. This study focuses on the development of a new laser diagnostic technique Cavity Enhanced Magneto-Optic Rotation (CEMOR) for the application of sensitive and selective measurements of paramagnetic species in combustion systems, particularly HO2 and RO2 radicals. CEMOR merges the selective ability of Magneto-Optic Rotation (MOR) spectroscopy with the sensitivity of Cavity Ringdown Spectroscopy (CRDS). CRDS in conjunction with Laser Induced Fluorescence (LIF) spectroscopy has been applied to calibrate the axial concentration profiles of OH radicals in an atmospheric pressure methane/air flame. This has allowed MOR and CEMOR to be evaluated in a combustion system. CEMOR has demonstrated an enhancement in MOR sensitivity, displaying a detection limit similar to CRDS. Assessment of the unique temporal signal behavior of CEMOR has demonstrated a power series relationship with radical concentration. The results demonstrate the potential in the diagnostics for measuring HO2 and RO2 in combustion systems. Additionally, a flash photolysis facility has been designed and developed for generating HO2 and RO2 radicals to allow diagnostic analysis using CRDS and CEMOR. Diagnostic measurements of HO2 and H₂O in the flash photolysis system have been presented.
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Details
- Title
- Development of a sensitive and selective laser diagnostic technique for measuring paramagnetic species
- Creators
- Jamie Lee Lane - DU
- Contributors
- Nicholas Peter Cernansky (Advisor) - Drexel University (1970-)David Leslie Miller (Advisor) - Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- College of Engineering (1970-2026); Mechanical Engineering (and Mechanics) [Historical]; Drexel University
- Other Identifier
- 3797; 991014632681604721