Study of energy transfer processes in CH as prerequisite for quantitative minor species concentration measurements

Bülter, Andreas; Rahmann, Ulrich; Kohse‐Höinghaus, Katharina; Brockhinke, Andreas

doi:10.1007/s00340-004-1423-8

Cited by 11 publications

(13 citation statements)

References 45 publications

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“…The role of collisional energy transfer in LIF has been studied extensively for several molecules and radicals relevant for combustion, including OH [4,6], CH [14], and C 2 [7]. We have developed a computer program, LASKINν 2 [40] that has proven to be capable of predicting the resulting fluorescence spectra with high reliability.…”

Section: Laskinν 2 Modelingmentioning

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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Section: Laskinν 2 Modelingmentioning

confidence: 99%

Measurement and simulation of rotationally-resolved chemiluminescence spectra in flames

et al. 2012

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“…7,8 Predissociative LIF and short-pulse strategies, especially for the measurement of OH, have been suggested in the past as techniques to avoid the quenching problem in combustion measurements. [9][10][11][12][13][14] While quench-free OH and CH measurements have been demonstrated in atmospheric-pressure flames using short-pulse lasers, 7,8,15,16 the use of linearly polarized laser radiation in these experiments leads to a preferential excitation of the target molecule, and fluorescence, especially of the directly pumped level, will not be isotropic. Polarization ratios for the collision-free case -which would be ideally encountered at time zero -have been calculated by Doherty and Crosley, 17 and a more general approach has been discussed by Lucht et al 18 This collision-free situation is, however, hardly encountered in typical LIF combustion measurements, where collisions will gradually randomize any preferential orientation.…”

Section: Introductionmentioning

confidence: 99%

Energy transfer in the OH A²Σ⁺state: The role of polarization and of multi-quantum energy transfer

Brockhinke

Lenhard

Bülter

et al. 2005

Phys. Chem. Chem. Phys.

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Energy transfer in the excited state of molecules including quenching, rotational and vibrational energy transfer, and polarization scrambling is one of the major factors which limit the accuracy of laser-induced fluorescence (LIF) measurements. In this contribution, we present time-, wavelength-, and polarization-resolved spectra of OH in a stoichiometric H2/air flame at atmospheric pressure. Emphasis is placed on the investigation of the role of polarization effects and of multi-quantum vibrational energy transfer on fluorescence spectra originating from the OH A2sigma+ state. Results are compared to simulations using a rate-equation model (LASKIN) developed in our group.

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“…The simulated gas composition of the flame combustion products of the stoichiometric methane-air mixture (fuel excess coefficient, Ф = 1) corresponded to the following molar fractions of N2, CO2, H2O and OH: 72%, 9%, 18% and 1%, respectively. The OH fluorescence was numerically simulated at excitation of transitions Q2 (7), Q1(8), R1(14), P1(2) of the band (1-0) of the A 2 Σ + -X 2 Π system.…”

Section: Resultsmentioning

confidence: 99%

“…The present study focuses on the approbation of the thermometry method based on the OH PLIF when the transition A 2 Σ + -X 2 Π (1-0) is excited and the ratio of the fluorescence intensity between the band (2-0) and bands (0-0), (1-1) is recorded. The commercial LASKIN software package was used for computer modelling of OH fluorescence [7]. The method was applied to a swirling premixed methane-air flame directed against a flat cooled surface.…”

Section: Introductionmentioning

confidence: 99%

Temperature measurements in a swirling impinging flame by planar laser-induced fluorescence

Tolstoguzov

2021

J. Phys.: Conf. Ser.

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This article presents the results of approbation of the method for registering temperature distributions based on the planar laser-induced fluorescence of a hydroxyl radical (OH) when the band (1-0) of the A2Σ+–X2Π system is excited. The thermometry is based on the recording the ratio of the radiation intensity of the band (2-0) and the bands (0-0), (1-1). Numerical modelling of fluorescence spectra is performed using the LASKIN program for the most frequent excitation lines Q2(7), Q1(8), R1(14), P1(2). The temperature field of a swirling flame, impinging on a flat cold surface, for H/d = 1, 2 and 3 calibres (where H is the distance between the jet nozzle and the surface, d is the outlet diameter of the nozzle) is obtained. The results of the work demonstrate that when the transition Q1(8) is excited, the ratio of the intensity of fluorescence signals for the band (2-0) and the bands (0-0), (1-1) provides a high sensitivity to temperature and is not significantly affected by fluorescence quenching. The report also concludes that this method can be implemented using single pulsed laser illumination and is effective for the detecting the position of flow recirculation zones and registering hot heat release zones with the combustion products.

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Study of energy transfer processes in CH as prerequisite for quantitative minor species concentration measurements

Cited by 11 publications

References 45 publications

Measurement and simulation of rotationally-resolved chemiluminescence spectra in flames

Measurement and simulation of rotationally-resolved chemiluminescence spectra in flames

Energy transfer in the OH A²Σ⁺state: The role of polarization and of multi-quantum energy transfer

Temperature measurements in a swirling impinging flame by planar laser-induced fluorescence

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Study of energy transfer processes in CH as prerequisite for quantitative minor species concentration measurements

Cited by 11 publications

References 45 publications

Measurement and simulation of rotationally-resolved chemiluminescence spectra in flames

Measurement and simulation of rotationally-resolved chemiluminescence spectra in flames

Energy transfer in the OH A2Σ+state: The role of polarization and of multi-quantum energy transfer

Temperature measurements in a swirling impinging flame by planar laser-induced fluorescence

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Energy transfer in the OH A²Σ⁺state: The role of polarization and of multi-quantum energy transfer