Measurements of absolute concentrations of CH in a premixed atmospheric flat flame by cavity ring-down spectroscopy

R. Evertsen, J.A. Oijen, van, R.T.E. Hermanns, L.P.H. Goey, de, J.J. Meulen, ter

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Abstract

Absolute concentrations of CH in a premixed, atmospheric flat flame of CH4 and air have been determined with cavity ring-down spectroscopy (CRDS). CH is excited from the X2¿ to the A2¿ state at 430 nm. Since at atmospheric pressure the CH radical is present only in a very narrow layer at the flame front, specific problems due to the finite size of the laser beam and thermal deflection are encountered. An intensified CCD camera was used as an aid to be able to take these effects into account. Distributions of [CH] were obtained for two different stoichiometries (f = 1.2 and 1.1) in a burner-stabilized flame. Signal-to-noise ratios indicate that [CH] number densities down to 4 × 1011 cm-3, corresponding to 1.5 ppb (S/N = 2) can be detected easily at 1 atm. Flame uniformity was verified with an Abel inversion technique. The rotational flame temperature was derived from Boltzmann distributions. The results were compared to modeling calculations using GRI-Mech 2.11 and 3.0. The predictions for both models show higher maximum [CH] located further away from the burner. The computed maximum [CH] is predicted in both cases at a higher temperature. Analyses of the effect of errors in the experimental settings and direct absorption measurements of [OH] have been used to verify positional differences. The results indicate that the differences may be attributed to reaction mechanisms.
Original languageEnglish
Pages (from-to)34-42
JournalCombustion and Flame
Volume132
Issue number1-2
DOIs
Publication statusPublished - 2003

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Fuel burners
flames
Spectroscopy
methylidyne
cavities
rings
CCD cameras
Stoichiometry
spectroscopy
Atmospheric pressure
Laser beams
Signal to noise ratio
Temperature
burners
Air
flame temperature
Boltzmann distribution
flame propagation
deflection
stoichiometry

Cite this

@article{fc41d2cc0cc24807814bebaec2452936,
title = "Measurements of absolute concentrations of CH in a premixed atmospheric flat flame by cavity ring-down spectroscopy",
abstract = "Absolute concentrations of CH in a premixed, atmospheric flat flame of CH4 and air have been determined with cavity ring-down spectroscopy (CRDS). CH is excited from the X2¿ to the A2¿ state at 430 nm. Since at atmospheric pressure the CH radical is present only in a very narrow layer at the flame front, specific problems due to the finite size of the laser beam and thermal deflection are encountered. An intensified CCD camera was used as an aid to be able to take these effects into account. Distributions of [CH] were obtained for two different stoichiometries (f = 1.2 and 1.1) in a burner-stabilized flame. Signal-to-noise ratios indicate that [CH] number densities down to 4 × 1011 cm-3, corresponding to 1.5 ppb (S/N = 2) can be detected easily at 1 atm. Flame uniformity was verified with an Abel inversion technique. The rotational flame temperature was derived from Boltzmann distributions. The results were compared to modeling calculations using GRI-Mech 2.11 and 3.0. The predictions for both models show higher maximum [CH] located further away from the burner. The computed maximum [CH] is predicted in both cases at a higher temperature. Analyses of the effect of errors in the experimental settings and direct absorption measurements of [OH] have been used to verify positional differences. The results indicate that the differences may be attributed to reaction mechanisms.",
author = "R. Evertsen and {Oijen, van}, J.A. and R.T.E. Hermanns and {Goey, de}, L.P.H. and {Meulen, ter}, J.J.",
year = "2003",
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language = "English",
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Measurements of absolute concentrations of CH in a premixed atmospheric flat flame by cavity ring-down spectroscopy. / Evertsen, R.; Oijen, van, J.A.; Hermanns, R.T.E.; Goey, de, L.P.H.; Meulen, ter, J.J.

In: Combustion and Flame, Vol. 132, No. 1-2, 2003, p. 34-42.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - Measurements of absolute concentrations of CH in a premixed atmospheric flat flame by cavity ring-down spectroscopy

AU - Evertsen, R.

AU - Oijen, van, J.A.

AU - Hermanns, R.T.E.

AU - Goey, de, L.P.H.

AU - Meulen, ter, J.J.

PY - 2003

Y1 - 2003

N2 - Absolute concentrations of CH in a premixed, atmospheric flat flame of CH4 and air have been determined with cavity ring-down spectroscopy (CRDS). CH is excited from the X2¿ to the A2¿ state at 430 nm. Since at atmospheric pressure the CH radical is present only in a very narrow layer at the flame front, specific problems due to the finite size of the laser beam and thermal deflection are encountered. An intensified CCD camera was used as an aid to be able to take these effects into account. Distributions of [CH] were obtained for two different stoichiometries (f = 1.2 and 1.1) in a burner-stabilized flame. Signal-to-noise ratios indicate that [CH] number densities down to 4 × 1011 cm-3, corresponding to 1.5 ppb (S/N = 2) can be detected easily at 1 atm. Flame uniformity was verified with an Abel inversion technique. The rotational flame temperature was derived from Boltzmann distributions. The results were compared to modeling calculations using GRI-Mech 2.11 and 3.0. The predictions for both models show higher maximum [CH] located further away from the burner. The computed maximum [CH] is predicted in both cases at a higher temperature. Analyses of the effect of errors in the experimental settings and direct absorption measurements of [OH] have been used to verify positional differences. The results indicate that the differences may be attributed to reaction mechanisms.

AB - Absolute concentrations of CH in a premixed, atmospheric flat flame of CH4 and air have been determined with cavity ring-down spectroscopy (CRDS). CH is excited from the X2¿ to the A2¿ state at 430 nm. Since at atmospheric pressure the CH radical is present only in a very narrow layer at the flame front, specific problems due to the finite size of the laser beam and thermal deflection are encountered. An intensified CCD camera was used as an aid to be able to take these effects into account. Distributions of [CH] were obtained for two different stoichiometries (f = 1.2 and 1.1) in a burner-stabilized flame. Signal-to-noise ratios indicate that [CH] number densities down to 4 × 1011 cm-3, corresponding to 1.5 ppb (S/N = 2) can be detected easily at 1 atm. Flame uniformity was verified with an Abel inversion technique. The rotational flame temperature was derived from Boltzmann distributions. The results were compared to modeling calculations using GRI-Mech 2.11 and 3.0. The predictions for both models show higher maximum [CH] located further away from the burner. The computed maximum [CH] is predicted in both cases at a higher temperature. Analyses of the effect of errors in the experimental settings and direct absorption measurements of [OH] have been used to verify positional differences. The results indicate that the differences may be attributed to reaction mechanisms.

U2 - 10.1016/S0010-2180(02)00436-4

DO - 10.1016/S0010-2180(02)00436-4

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