NCN concentration and interfering absorption by CH2O, NH and OH in low pressure methane/air flames with and without N2O

Klein-Douwel, Rjh Robert; Konnov, Alexander A.; Dam, NJ Nico; Meulen, ter Jj

doi:10.1016/j.combustflame.2011.04.009

Cited by 3 publications

(2 citation statements)

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“…Briefly, according to Fenimore, 5 NO x formation is initiated by the reaction of small hydrocarbon radicals with molecular nitrogen, which is present in the combustion air. During the last ten years it has been proved that the initiation step yields NCN radicals in the triplet ground state, 3,4,[6][7][8][9][10][11] CH( 2 P) + N 2 ( 1 S + ) -H( 2 S) + NCN ( 3 S À g ),…”

Section: Introductionmentioning

confidence: 99%

Direct measurements of the high temperature rate constants of the reactions NCN + O, NCN + NCN, and NCN + M

Dammeier

Faßheber

Friedrichs

2012

Phys. Chem. Chem. Phys.

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The rate constant of the reaction NCN + O has been directly measured for the first time. According to the revised Fenimore mechanism, which is initiated by the NCN forming reaction CH + N(2)→ NCN + H, this reaction plays a key role for prompt NO(x) formation in flames. NCN radicals and O atoms have been quantitatively generated by the pyrolysis of NCN(3) and N(2)O, respectively. NCN concentration-time profiles have been monitored behind shock waves using narrow-bandwidth laser absorption at a wavelength of λ = 329.1302 nm. Whereas no pressure dependence was discernible at pressures between 709 mbar < p < 1861 mbar, a barely significant temperature dependence corresponding to an activation energy of 5.8 ± 6.0 kJ mol(-1) was found. Overall, at temperatures of 1826 K < T < 2783 K, the rate constant can be expressed as k(NCN + O) = 9.6 × 10(13)× exp(-5.8 kJ mol(-1)/RT) cm(3) mol(-1) s(-1) (±40%). As a requirement for accurate high temperature rate constant measurements, a consistent NCN background mechanism has been derived from pyrolysis experiments of pure NCN(3)/Ar gas mixtures, beforehand. Presumably, the bimolecular secondary reaction NCN + NCN yields CN radicals hence triggering a chain reaction cycle that efficiently removes NCN. A temperature independent value of k(NCN + NCN) = (3.7 ± 1.5) × 10(12) cm(3) mol(-1) s(-1) has been determined from measurements at pressures ranging from 143 mbar to 1884 mbar and temperatures ranging from 966 K to 1900 K. At higher temperatures, the unimolecular decomposition of NCN, NCN + M → C + N(2) + M, prevails. Measurements at temperatures of 2012 K < T < 3248 K and at total pressures of 703 mbar < p < 2204 mbar reveal a unimolecular decomposition close to its low pressure limit. The corresponding rate constants can be expressed as k(NCN + M) = 8.9 × 10(14)× exp(-260 kJ mol(-1)/RT) cm(3) mol(-1) s(-1)(±20%).

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Section: Introductionmentioning

confidence: 99%

Direct measurements of the high temperature rate constants of the reactions NCN + O, NCN + NCN, and NCN + M

Dammeier

Faßheber

Friedrichs

2012

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

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“…NH absorption lines interfere with the NCN spectrum as shown in Fig. 18, thus preventing accurate NCN absorbance measurements [165]. The best compromise up to now was found in an acetylene low-pressure flame [44] where the SNR was as high as 6.…”

Section: Absolute Quantification Of Ncn Lif Signalsmentioning

confidence: 99%