Journal ArticleDOI
Laser-Saturated Fluorescence Measurements of OH in Atmospheric Pressure CH4/O2/N2 Flames Under Sooting and Non-Sooting Conditions
TLDR
In this article, the rotational Raman scattering was identified as a potentially significant interference in the fluorescence measurements at low OH concentration levels (down to 5ppm) typical of the rich flames.Abstract:
OH concentration measurements have been performed in rich, atmospheric pressure CH4/O2/N2 flames using laser-saturated fluorescence. Both sooting and non-sooting conditions have been investigated. OH is thought to be an important species in soot chemistry because of its role in the oxidation of soot and soot precursors. In the sooting flame, the centerline axial OH concentration drops sharply 3-4 mm above the burner surface. Visible soot emission begins only after the OH concentration decreases significantly from its peak value in the flame zone. Rotational Raman scattering was identified as a potentially significant interference in the fluorescence measurements at the low OH concentration levels (down to 5 ppm) typical of the rich flames. Laser-saturated fluorescence and optical absorption measurements of OH concentration were also performed in a lean, atmospheric pressure CH4/O2/N2 flame. A combination fluorescence-absorption calibration in the lean flame was used to determine absolute OH numbe...read more
Citations
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Laser Techniques for the Quantitative Detection of Reactive Intermediates
TL;DR: An overview of recent developments in laser diagnostic methods for the quantitative measurement of trace species concentrations and, in conjunction, of temperature in combustion systems is given in this article, where typical applications and discusses advantages and limitations of laser techniques including laser absorption, linear, saturated, predissociative and multi-photon-excited laser-induced fluorescence (LIF), resonanceenhanced multiphoton ionization (REMPI), electronically resonant coherent anti-Stokes Raman scattering (resonance CARS), degenerate four-wave mixing (DFWM) and amplified spontaneous
Journal ArticleDOI
Laser techniques for the quantitative detection of reactive intermediates in combustion systems
TL;DR: An overview of recent developments in laser diagnostic methods for the quantitative measurement of trace species concentrations and, in conjunction, of temperature in combustion systems is given in this article, where typical applications and discusses advantages and limitations of laser techniques including laser absorption, linear, saturated, predissociative and multi-photon-excited laser-induced fluorescence (LIF), resonanceenhanced multiphoton ionization (REMPI), electronically resonant coherent anti-Stokes Raman scattering (resonance CARS), degenerate four-wave mixing (DFWM) and amplified spontaneous
Journal ArticleDOI
The spontaneous raman scattering technique applied to nonpremixed flames of methane
TL;DR: In this paper, spontaneous Raman scattering has been used to measure the temperature of CH 4 turbulent non-premixed flames using the Rayleigh scattered signal, and the remaining "fluorescence" has been corrected for, using correction curves generated from measurements made in a laminar counterflow CH 4 diffusion flame and a diluted CH 4 N 2 = 1 2 (by vol.) Laminar diffusion flame.
Journal ArticleDOI
Degenerate four-wave mixing diagnostics on OH and NH radicals in flames
Thomas Dreier,David J. Rakestraw +1 more
TL;DR: In this paper, a degreenerate four wave mixing (DFWM) is applied as a diagnostic to study OH and NH radicals in flames, which offers the advantages of a highly collimated signal beam permitting efficient rejection of interfering radiation and requiring minimal optical access.
Proceedings ArticleDOI
OH radical imaging in a DI diesel engine and the structure of the early diffusion flame
John E. Dec,Edward B. Coy +1 more
TL;DR: In this paper, planar laser-induced fluorescence (PLIF) imaging of the OH radical has been applied to the reacting fuel jet of a direct-injection diesel engine of the ''heavy-duty`` size class, modified for optical access.
References
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Journal ArticleDOI
Mechanisms of soot nucleation in flames—A critical review
TL;DR: In this article, the authors present a mechanism for soot formation in a premixed laminar flame, where chemiions are assumed to be the precursor on which the free radicals, polyacetylenes, and polycyclic aromatic hydrocarbons repeatedly add in fast ion-molecule reactions.
Journal ArticleDOI
Oxidation of soot by hydroxyl radicals
Journal ArticleDOI
Sooting Behavior of Gaseous Hydrocarbon Diffusion Flames and the Influence of Additives
TL;DR: The sooting behavior of laminar diffusion flames were altered by addition of diluents to the fuel flow as discussed by the authors, and the effect of water vapor, carbon dioxide and sulphur dioxide in reducing the tendency to soot was purely thermal with no observable chemical interaction.
Journal ArticleDOI
Two-dimensional imaging of OH laser-induced fluorescence in a flame.
Mark J. Dyer,David R. Crosley +1 more
TL;DR: A method for obtaining a two-dimensional image of laser-induced fluorescence of a naturally occurring flame radical that holds considerable promise for imaging in time-varying systems, such as reactive turbulent combustion.
Journal ArticleDOI
Collisional quenching of A 2Σ+ OH at elevated temperatures
TL;DR: In this paper, the authors measured the thermal averaged cross sections σQ for collisional quenching of the A 2 ε+ state of the OH molecule near 1100 K. The experimental results have been compared with a theoretical calculation based on multipole attractive forces with a repulsive centrifugal barrier.