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Experimental and kinetic modeling study of NO formation in premixed CH4+O2+N2 flames

Han, Xinlu LU ; Marco, Lubrano Lavadera LU ; Brackmann, Christian LU ; Wang, Zhihua ; He, Yong and Konnov, Alexander A. LU (2021) In Combustion and Flame 223. p.349-360
Abstract

The nitric oxide (NO) formation in methane (CH4) flames has been widely investigated, with quite a few kinetic mechanisms available in the literature. However, studies have shown that there are often discrepancies between the simulations using various mechanisms and the experimental results. To elucidate reactions leading to these discrepancies, experiments were designed to measure the NO formation in the post flame zone of CH4+O2+N2 flames with the oxygen ratio, xO2 = O2/(O2+N2), varying from 0.2 to 0.27. The experiments were carried out on a heat flux burner at atmospheric pressure and 298 K using saturated Laser-induced fluorescence.... (More)

The nitric oxide (NO) formation in methane (CH4) flames has been widely investigated, with quite a few kinetic mechanisms available in the literature. However, studies have shown that there are often discrepancies between the simulations using various mechanisms and the experimental results. To elucidate reactions leading to these discrepancies, experiments were designed to measure the NO formation in the post flame zone of CH4+O2+N2 flames with the oxygen ratio, xO2 = O2/(O2+N2), varying from 0.2 to 0.27. The experiments were carried out on a heat flux burner at atmospheric pressure and 298 K using saturated Laser-induced fluorescence. The equivalence ratio, ϕ, was changed from 0.7 to 1.6. The corresponding laminar burning velocity, SL, for each condition was also measured using the heat flux method. A comparison was made for the present experimental data and simulation results using the Konnov, Glarborg, NOMecha 2.0, and San Diego mechanisms, and none of them well reproduced the new NO experimental data for all investigated conditions. Numerical analyses show that the increment of NO mole fraction in stoichiometric and fuel-lean flames when the xO2increases is mostly defined by the thermal-NO production, which is found to be over-predicted, especially by the Konnov and San Diego mechanisms. The rate constant of reaction NO+N = N2+O was derived as [Formula presented]cm3 / mol s over 225–2400 K temperature range. The rate constants of four reactions controlling CH mole fraction profiles and prompt-NO formation were updated based on the analysis of the literature data that yields an improved performance of the Konnov mechanism.

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author
; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Kinetic mechanism, Laminar burning velocity, LIF, Methane flame, Nitric oxide
in
Combustion and Flame
volume
223
pages
12 pages
publisher
Elsevier
external identifiers
  • scopus:85093660894
ISSN
0010-2180
DOI
10.1016/j.combustflame.2020.10.010
language
English
LU publication?
yes
id
b51266f6-12aa-4082-a9f9-3fd410135a5e
date added to LUP
2020-11-04 08:36:17
date last changed
2020-12-06 04:36:19
@article{b51266f6-12aa-4082-a9f9-3fd410135a5e,
  abstract     = {<p>The nitric oxide (NO) formation in methane (CH<sub>4</sub>) flames has been widely investigated, with quite a few kinetic mechanisms available in the literature. However, studies have shown that there are often discrepancies between the simulations using various mechanisms and the experimental results. To elucidate reactions leading to these discrepancies, experiments were designed to measure the NO formation in the post flame zone of CH<sub>4</sub>+O<sub>2</sub>+N<sub>2</sub> flames with the oxygen ratio, x<sub>O<sub>2</sub></sub> = O<sub>2</sub>/(O<sub>2</sub>+N<sub>2</sub>), varying from 0.2 to 0.27. The experiments were carried out on a heat flux burner at atmospheric pressure and 298 K using saturated Laser-induced fluorescence. The equivalence ratio, ϕ, was changed from 0.7 to 1.6. The corresponding laminar burning velocity, S<sub>L</sub>, for each condition was also measured using the heat flux method. A comparison was made for the present experimental data and simulation results using the Konnov, Glarborg, NOMecha 2.0, and San Diego mechanisms, and none of them well reproduced the new NO experimental data for all investigated conditions. Numerical analyses show that the increment of NO mole fraction in stoichiometric and fuel-lean flames when the x<sub>O<sub>2</sub></sub>increases is mostly defined by the thermal-NO production, which is found to be over-predicted, especially by the Konnov and San Diego mechanisms. The rate constant of reaction NO+N = N<sub>2</sub>+O was derived as [Formula presented]cm<sup>3</sup> / mol s over 225–2400 K temperature range. The rate constants of four reactions controlling CH mole fraction profiles and prompt-NO formation were updated based on the analysis of the literature data that yields an improved performance of the Konnov mechanism.</p>},
  author       = {Han, Xinlu and Marco, Lubrano Lavadera and Brackmann, Christian and Wang, Zhihua and He, Yong and Konnov, Alexander A.},
  issn         = {0010-2180},
  language     = {eng},
  pages        = {349--360},
  publisher    = {Elsevier},
  series       = {Combustion and Flame},
  title        = {Experimental and kinetic modeling study of NO formation in premixed CH<sub>4</sub>+O<sub>2</sub>+N<sub>2</sub> flames},
  url          = {http://dx.doi.org/10.1016/j.combustflame.2020.10.010},
  doi          = {10.1016/j.combustflame.2020.10.010},
  volume       = {223},
  year         = {2021},
}