Quantitative HCN measurements in CH4/N2O/O-2/N-2 flames using mid-infrared polarization spectroscopy

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T1 - Quantitative HCN measurements in CH4/N2O/O-2/N-2 flames using mid-infrared polarization spectroscopy

AU - Sun, Zhiwei

AU - Li, Zhongshan

AU - Konnov, Alexander

AU - Aldén, Marcus

PY - 2011

Y1 - 2011

N2 - Quantitative measurements of hydrogen cyanide (HCN) were nonintrusively performed using mid-infrared polarization spectroscopy (IRPS) in atmospheric pressure flames. The lifted flat, laminar, premixed CH4/N2O/O-2/N-2 flames were stabilized on a 7 cm diameter home-built McKenna-type burner with variable proportion of N2O and O-2. The characteristic spectral structure of HCN molecules was identified in the rotational line-resolved IRPS spectra collected in flames at around 3248 cm(-1). The P20 line belonging to the C-H stretching band was chosen for quantitative measurements and the line-integrated IRPS signal was recorded in a series of fuel-rich CH4/O-2/N2O/N-2 flames with equivalence ratios of 1.2, 1.4 and 1.6. Absolute mole fractions of HCN molecules in these flames were obtained through in situ calibration of the optical system with nonreactive gas flow of N-2 seeded with known amount of HCN on the same burner. Moreover, the experimental results were compared with calculations performed using the Konnov detailed C/H/N/O mechanism, which implements NCN prompt-NO reactions. Generally good agreement was found with some discrepancies indicating the need for further model improvement. (C) 2011 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

AB - Quantitative measurements of hydrogen cyanide (HCN) were nonintrusively performed using mid-infrared polarization spectroscopy (IRPS) in atmospheric pressure flames. The lifted flat, laminar, premixed CH4/N2O/O-2/N-2 flames were stabilized on a 7 cm diameter home-built McKenna-type burner with variable proportion of N2O and O-2. The characteristic spectral structure of HCN molecules was identified in the rotational line-resolved IRPS spectra collected in flames at around 3248 cm(-1). The P20 line belonging to the C-H stretching band was chosen for quantitative measurements and the line-integrated IRPS signal was recorded in a series of fuel-rich CH4/O-2/N2O/N-2 flames with equivalence ratios of 1.2, 1.4 and 1.6. Absolute mole fractions of HCN molecules in these flames were obtained through in situ calibration of the optical system with nonreactive gas flow of N-2 seeded with known amount of HCN on the same burner. Moreover, the experimental results were compared with calculations performed using the Konnov detailed C/H/N/O mechanism, which implements NCN prompt-NO reactions. Generally good agreement was found with some discrepancies indicating the need for further model improvement. (C) 2011 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

KW - HCN

KW - Mid-infrared polarization spectroscopy

KW - Methane flames

U2 - 10.1016/j.combustflame.2011.03.008

DO - 10.1016/j.combustflame.2011.03.008

M3 - Article

VL - 158

SP - 1898

EP - 1904

JO - Combustion and Flame

JF - Combustion and Flame

SN - 0010-2180

IS - 10

ER -