Kinetics of the Species OH(A2Σ+), OH(X2Π and CH(X2Π) in the System C2H2/O/H

Grebe, J.; Homann, K. H.

doi:10.1002/bbpc.19820860702

Cited by 35 publications

(26 citation statements)

References 20 publications

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“…The rate constant for that reaction was derived by Porter et al [18] by correlating measured CH, O 2 and OH* profiles through the flame. Walsh et al [15] reported a rate constant for the OH* formation that was two orders of magnitude greater than the one derived by Porter et al [18], although Grebe and Homann [34], in the same year, reported a rate constant approximately equal to the one derived by Porter et al [18] in their work at a flow reactor. Smith et al [23] proposed a rate constant for OH* formation three times greater than that of Porter et al [18] by measuring absolute excited concentrations of OH* at a flat premixed low-pressure methane-air flame.…”

Section: Geometry and Excited Species Mechanismsmentioning

confidence: 83%

Numerical evaluation of equivalence ratio measurement using OH∗ and CH∗ chemiluminescence in premixed and non-premixed methane–air flames

Panoutsos

Hardalupas

Taylor

2009

Combustion and Flame

240

104

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This work presents results from detailed chemical kinetics calculations of electronically excited OH (A 2 Ȉ, denoted as OH*) and CH (A 2 ǻ, denoted as CH*) chemiluminescent species in laminar premixed and non-premixed counterflow methane-air flames, at atmospheric pressure. Eight different detailed chemistry mechanisms, with added elementary reactions that account for the formation and destruction of the chemiluminescent species OH* and CH*, are studied. The effects of flow strain rate and equivalence ratio on the chemiluminescent intensities of OH*, CH* and their ratio are studied and the results are compared to chemiluminescent intensity ratio measurements from premixed laminar counterflow natural gas-air flames. This is done in order to numerically evaluate the measurement of equivalence ratio using OH* and CH* chemiluminescence, an experimental practice that is used in the literature. The calculations reproduced the experimental observation that there is no effect of strain rate on the chemiluminescent intensity ratio of OH* to CH*, and that the ratio is a monotonic function of equivalence ratio. In contrast, the strain rate was found to have an effect on both the OH* and CH* intensities, in agreement with experiment. The calculated OH*/CH* values showed that only five out of the eight mechanisms studied were within the same order of magnitude with the experimental data. A new mechanism, proposed in this work, gave results that agreed with experiment within 30%. It was found that the location of maximum emitted intensity from the excited species OH* and CH* was displaced by less than 65 and 115 ȝm, respectively, away from the maximum of the heat release rate, in agreement with experiments, which is small relative to the spatial resolution of experimental methods applied to combustion applications, and, therefore, it is expected that intensity from the OH* and CH* excited radicals can be used to identify the location of the reaction zone.Calculations of the OH*/CH* intensity ratio for strained non-premixed counterflow methane-3 air flames showed that the intensity ratio takes different values from those for premixed flames, and therefore has the potential to be used as a criterion to distinguish between premixed and non-premixed reaction in turbulent flames.

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Section: Geometry and Excited Species Mechanismsmentioning

confidence: 83%

Numerical evaluation of equivalence ratio measurement using OH∗ and CH∗ chemiluminescence in premixed and non-premixed methane–air flames

Panoutsos

Hardalupas

Taylor

2009

Combustion and Flame

240

104

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“…OH * emission from hydrogen mixtures has been studied in shock tubes by Belles and Lauver [16], Gutman et al [17], Gardiner et al [18], Hidaka et al [19], Koike and Morinaga [20], and Paul et al [21]. Measurements of OH * formation rates in hydrocarbon mixtures have been reported by Carl et al [22], Grebe and Homann [23], Lichtin et al [24,25], Smith et al [14,15], and Porter et al [26]. Theoretical studies of the collisional quenching of OH * are available as well [27][28][29][30].…”

Section: Introductionmentioning

confidence: 94%

An optimized kinetics model for OH chemiluminescence at high temperatures and atmospheric pressures

Hall

Petersen

2006

Int J of Chemical Kinetics

153

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Chemiluminescence from the OH(A → X) transition near 307 nm is a commonly used diagnostic in combustion applications such as flame chemistry, shock-tube experiments, and reacting-flow visualization. Although absolute measurements of OH(X) concentrations are well defined, there is no elementary relation between emission from the electronically excited state (OH * ) and its absolute concentration. Thus, to enable quantitative emission measurements, a kinetics model has been assembled and optimized to predict OH * formation and quenching at combustion conditions. Shock-tube experiments were conducted in mixtures of H 2 /O 2 /Ar, CH 4 /O 2 /Ar, and CH 4 /H 2 /O 2 /Ar with high levels of argon dilution (>98%). Elementary reactions to model OH * , along with initial estimates of their rate coefficients, were taken from the literature. The important formation steps follow:Sensitivity analyses were performed to identify experimental conditions under which the shape of the measured OH * profiles and the magnitude of the OH * emission would be sensitive to the formation reactions. A fitting routine was developed to express the formation rate parameters as a function of a single rate, k 1 at the reference temperature (1490 K). With all rates so expressed, H 2 /CH 4 mixtures were designed to uniquely determine the value of k 1 at the reference temperature, from which the remaining rate parameters were calculated. Quenching rates were fixed at their literature values. The new model predicts the experimental data over the range ofCorrespondence to: Joel M. Hall;

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“…For the determination of their absolute concentrations the H-atoms were converted to OH-radicals via the reaction H + NO, + OH + NO (4) by the addition of excess NO, in the absence of CH, and CH,CO. The OH-radicals which were calibrated using reaction (4) with H in excess over NO, were monitored directly with the Imr.…”

Section: Mol/cm3mentioning

confidence: 99%

Direct Determination of the Rate Constant for the Reaction CH₂ + H → CH + H₂

Böhland

Temps

1984

Ber Bunsenges Phys Chem

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Chemical Kinetics / Elementary Reactions / Laser Magnetic Resonance / RadicalsThe reaction CH,(R3Bl) + H(2S) __* CH('l7) + H2('Z) was investigated at room temperature in an isothermal discharge flow reactor with laser magnetic resonance detection of CH, and CH. Direct measurements of the decay of CH, in the presence of an excess of H-atoms yielded a rate constant of k , (298 K) = (1.6 * 0 . 6 ) . 1014 cm3/mol. s .Combined with the known rate constant for the reverse reaction CH + H, -. CH2 + H the heat of formation of CH2 was found to be AH/,,,(CH,) = (381 k 3) kJ/mol .

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Kinetics of the Species OH(A²Σ⁺), OH(X²Π and CH(X²Π) in the System C₂H₂/O/H

Cited by 35 publications

References 20 publications

Numerical evaluation of equivalence ratio measurement using OH∗ and CH∗ chemiluminescence in premixed and non-premixed methane–air flames

Numerical evaluation of equivalence ratio measurement using OH∗ and CH∗ chemiluminescence in premixed and non-premixed methane–air flames

An optimized kinetics model for OH chemiluminescence at high temperatures and atmospheric pressures

Direct Determination of the Rate Constant for the Reaction CH₂ + H → CH + H₂

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Kinetics of the Species OH(A2Σ+), OH(X2Π and CH(X2Π) in the System C2H2/O/H

Cited by 35 publications

References 20 publications

Numerical evaluation of equivalence ratio measurement using OH∗ and CH∗ chemiluminescence in premixed and non-premixed methane–air flames

Numerical evaluation of equivalence ratio measurement using OH∗ and CH∗ chemiluminescence in premixed and non-premixed methane–air flames

An optimized kinetics model for OH chemiluminescence at high temperatures and atmospheric pressures

Direct Determination of the Rate Constant for the Reaction CH2 + H → CH + H2

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Kinetics of the Species OH(A²Σ⁺), OH(X²Π and CH(X²Π) in the System C₂H₂/O/H

Direct Determination of the Rate Constant for the Reaction CH₂ + H → CH + H₂