Experimental and numerical study of the role of NCN in prompt-NO formation in low-pressure CH{sub 4}-O{sub 2}-N{sub 2} and C{sub 2}H{sub 2}-O{sub 2}-N{sub 2} flames
- Universite Lille1 Sciences et Technologies, Laboratoire PC2A UMR 8522 CNRS/Lille1, 59655 Villeneuve d'Ascq Cedex (France)
We report an experimental and modeling study on prompt-NO formation in low-pressure (5.3 kPa) premixed flames. Special emphasis is given to the quantitative detection (and prediction) of NCN, whose role in prompt-NO formation has recently been confirmed in alkane flames. Here a rich ({phi} = 1.25) CH{sub 4}-O{sub 2}-N{sub 2} flame and rich ({phi} = 1.25) and stoichiometric C{sub 2}H{sub 2}-O{sub 2}-N{sub 2} flames have been investigated. Absolute concentration profiles of CH and NCN radicals and NO species are obtained by combining laser-induced fluorescence (LIF) and cavity ring-down spectroscopy (CRDS). Temperature profile is determined in each flame using OH and NO-LIF thermometry. Flame modeling is performed to determine the role of NCN in prompt-NO formation and to test the capacity of the present chemical mechanisms to predict some intermediate species involved in prompt-NO formation. The methane flame is modeled using GDFkin registered 3.0{sub N}CN mechanism [El Bakali et al., Fuel 85 (2006), 896-909]. The acetylene flames are modeled using the Lindstedt and Skevis C/H/O mechanism [Lindstedt and Skevis, Proc. Combust. Inst. 28 (2000), 1801-1807], completed by the submechanism issued from GDFkin registered 3.0{sub N}CN for nitrogen chemistry. This submechanism includes the initiation reaction CH + N{sub 2} = NCN + H. Rate constants of NO-sensitive reactions of the submechanism are modified by taking into account the recent literature. In particular, the C{sub 2}O route could be explored thanks to a significant presence of C{sub 2}O in acetylene flames. Globally, the modified submechanism of nitrogen chemistry coupled with the two hydrocarbon mechanisms leads to a satisfying prediction of NCN and NO mole fraction profiles, even though refinements of rate constant determination is still required. The role of NCN in prompt-NO formation in acetylene flames is demonstrated. (author)
- OSTI ID:
- 21350370
- Journal Information:
- Combustion and Flame, Vol. 157, Issue 10; Other Information: Elsevier Ltd. All rights reserved; ISSN 0010-2180
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ACETYLENE
METHANE
NITRIC OXIDE
FLAMES
TEMPERATURE DISTRIBUTION
NITROGEN
NUMERICAL ANALYSIS
COMBUSTION KINETICS
REACTION INTERMEDIATES
SIMULATION
DETECTION
NITROGEN COMPOUNDS
CYANIDES
RADICALS
STOICHIOMETRY
PRESSURE RANGE KILO PA
OXYGEN
Prompt-NO
Cavity ring-down spectroscopy
Laser-induced fluorescence