On the quantification of OH*, CH*, and C2* chemiluminescence in flames

Nau, Patrick; Krüger, Julia; Lackner, Alexander; Letzgus, Michael; Brockhinke, Andreas

doi:10.1007/s00340-012-5006-9

Cited by 27 publications

(8 citation statements)

References 32 publications

(44 reference statements)

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“…However, due to recent availability of the quantitative information for two stoichiometries (φ = 1.0 and 1.6) in [32], the excited species intensities are quantified to the absolute values by using a conversion factor from this reference.…”

Section: Methodsmentioning

confidence: 99%

Experimental and numerical study of chemiluminescent species in low-pressure flames

et al. 2012

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Chemiluminescence has been observed since the beginning of spectroscopy, nevertheless, important facts still remain unknown. Especially, reaction pathways leading to chemiluminescent species such as OH * , CH * , C * 2 , and CO * 2 are still under debate and cannot be modeled with standard codes for flame simulation. In several cases, even the source species of spectral features observed in flames are unknown. In recent years, there has been renewed interest in chemiluminescence, since it has been shown that this radiation can be used to determine flame parameters such as stoichiometry and heat release under some conditions. In this work, we present a reaction mechanism which predicts the OH * , CH * (in A-and B-state), and C * 2 emission strength in lean to fuel-rich stoichiometries. Measurements have been performed in a set of low-pressure flames which have already been well characterized by other methods. The flame front is resolved in these measurements, which allows a comparison of shape and position of the observed chemiluminescence with the respective simulated concentrations. To study the effects of varying fuels, methane flame diluted in hydrogen are measured as well. The 14 investigated premixed methane-oxygen-argon and methanehydrogen-oxygen-argon flames span a wide parameter field of fuel stoichiometry (φ = 0.5 to 1.6) and hydrogen content (H 2 vol% = 0 to 50).The relative comparison of measured and simulated excited species concentrations shows good agreement. The detailed and reliable modeling for several chemiluminescent species permits correlating heat release with all of these emissions under a large set of flame conditions. It appears from the present study that the normally used product of formaldehyde and OH concentration may be less well suited for such a prediction in the flames under investigation.

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Section: Methodsmentioning

confidence: 99%

Experimental and numerical study of chemiluminescent species in low-pressure flames

et al. 2012

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“…This is a prerequisite for absolute concentration measurements of these species [43,48,52]. Since it has been reported [10,46] that reabsorption can have a profound impact both on intensity and shape of the OH * chemiluminescence, absorption spectra are measured as well.…”

Section: Introductionmentioning

confidence: 99%

Measurement and simulation of rotationally-resolved chemiluminescence spectra in flames

et al. 2012

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In recent years, there has been renewed interest in chemiluminescence, since it has been shown that these emissions can be used to determine flame parameters such as stoichiometry and heat release under some conditions. Even though the origin of these emissions has been known for a long time, little attention has been paid to the detailed analysis of the spectral structure.In this contribution, we present rotationally-resolved spectra of all important chemiluminescent emissions OH A-X, CH B-X, CH A-X, and C 2 d-a in CH 4 /air flames. A numerical model based on the LASKINν 2 code has been developed that allows, for the first time, to accurately predict the shape of the measured spectra for all of these transitions. Reabsorption of chemiluminescence within the emitting flame is shown to be a major factor, affecting both intensity and structure of OH * spectra. Even in lab-scale flames, it might change the intensity of individual lines by a factor of 5. The shape of chemiluminescence spectra depends on several processes including initial state distribution and rotational and vibrational energy transfer (which, in turn, depend on the collisional environment and the temperature). It is shown that chemical reactions form OH * in highly excited states and that the number of collisions is not sufficient to equilibrate the initial distribution. Therefore, high apparent temperatures are necessary to describe the shape of the measured spectra. In contrast, CH * is formed with less excess energy and the spectral shape is very close to thermal. The rotational structure of C * 2 is close to thermal equilibrium as well. Vibrational temperatures are, however, signif-A. Brockhinke ( ) · J. Krüger · M. Heusing · M. Letzgus icantly higher than the flame temperature. Implications and perspectives for flame measurements are discussed.

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“…At present the LIF method is used for diagnostics of gas flows in the combustion zones of different power systems [5][6][7]. As a fluorescent reporter, both stable molecules and radicals have been employed.…”

Section: Resultsmentioning

confidence: 99%

Gas Flow Visualization Using Laser-induced Fluorescence

Загидуллин

Torbin

Чернышов

et al. 2015

Procedia Engineering

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Laser-induced fluorescence (LIF) is one of the methods for visualization of mixing and velocity field of supersonic flows. The method permits almost nonintrusive study of gas flow dynamics in jet engines with a high temporal and spatial resolution. The nature of supersonic flow implies large pressure, temperature and density gradients which might introduce considerable errors into the interpretation of the images, because LIF intensity strongly depends upon excited particle fluorescence decay lifetime in addition to its number density in the medium. An excited particle quenching rate usually depends on the local gas density and temperature. Therefore, for correct interpretation of the images it is necessary to know the temperature dependence of the quenching rate constants. In this work the method is developed to measure the temperature dependence of the quenching rate constant of the fluorescing particle using LIF.

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On the quantification of OH, CH, and C2* chemiluminescence in flames

Cited by 27 publications

References 32 publications

Experimental and numerical study of chemiluminescent species in low-pressure flames

Experimental and numerical study of chemiluminescent species in low-pressure flames

Measurement and simulation of rotationally-resolved chemiluminescence spectra in flames

Gas Flow Visualization Using Laser-induced Fluorescence

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