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Dynamics of atomic oxygen production in an NH3/air flame assisted by a nanosecond pulsed plasma discharge

Sun, Jinguo LU orcid ; Ravelid, Jonas LU ; Bao, Yupan LU ; Nilsson, Sebastian LU ; Konnov, Alexander A LU and Ehn, Andreas LU (2024) In Proceedings of the Combustion Institute 40(1-4).
Abstract
Atomic oxygen (O) is vital in plasma-assisted combustion, but its quantitative measurement is challenging and therefore rarely reported. This work performs femtosecond two-photon-absorption laser-induced fluorescence (fs-TALIF) imaging to quantify the dynamics of atomic oxygen production by a single nanosecond (ns) pulsed plasma discharge in an ammonia/air flame for the first time. First of all, the plasma kinetic enhancement is quantified by the plasma-produced O with a molar fraction of up to 2.8 × 10−3, which is at least one order higher than that in the flame without plasma. Then, the spatial distribution of O demonstrates significant differences between the unburnt and burnt zones, revealing the distinct mechanisms of O production in... (More)
Atomic oxygen (O) is vital in plasma-assisted combustion, but its quantitative measurement is challenging and therefore rarely reported. This work performs femtosecond two-photon-absorption laser-induced fluorescence (fs-TALIF) imaging to quantify the dynamics of atomic oxygen production by a single nanosecond (ns) pulsed plasma discharge in an ammonia/air flame for the first time. First of all, the plasma kinetic enhancement is quantified by the plasma-produced O with a molar fraction of up to 2.8 × 10−3, which is at least one order higher than that in the flame without plasma. Then, the spatial distribution of O demonstrates significant differences between the unburnt and burnt zones, revealing the distinct mechanisms of O production in unburnt and burnt NH3/air mixtures. Specifically, a new O region is formed in the burnt zone of the lean flame, which is probably mainly caused by the pathway of NO dissociation into O by the ns plasma. Furthermore, the temporal dynamics of O in different zones are discussed in-depth. In the unburnt zone, from the continuous increment of O after hundreds of ns following the ns discharge initiation, it can be seen that the relaxation of the excited nitrogen plays an equally important role in O production as the direct electron impact. Subsequently, O atoms in the unburnt zone exhibit an exponential decay, which is attributed to the formation of O3 from O. Whereas, in the burnt zone, a bi-exponential decay of O is found for the first time. Such decay mainly results from the reaction between O and H2O, which importantly, is a reaction to form OH radicals. The transition between decays is due to the formation of the O region in the unburnt zone and the dominance of the combustion kinetics in the post-plasma stage. © 2024 The Author(s) (Less)
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author
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organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Proceedings of the Combustion Institute
volume
40
issue
1-4
article number
105477
pages
7 pages
publisher
Elsevier
external identifiers
  • scopus:85197507041
ISSN
1540-7489
DOI
10.1016/j.proci.2024.105477
language
English
LU publication?
yes
id
faed1916-8a5b-4183-adb1-cb389e35016c
date added to LUP
2024-07-30 10:28:46
date last changed
2024-10-23 13:22:14
@article{faed1916-8a5b-4183-adb1-cb389e35016c,
  abstract     = {{Atomic oxygen (O) is vital in plasma-assisted combustion, but its quantitative measurement is challenging and therefore rarely reported. This work performs femtosecond two-photon-absorption laser-induced fluorescence (fs-TALIF) imaging to quantify the dynamics of atomic oxygen production by a single nanosecond (ns) pulsed plasma discharge in an ammonia/air flame for the first time. First of all, the plasma kinetic enhancement is quantified by the plasma-produced O with a molar fraction of up to 2.8 × 10−3, which is at least one order higher than that in the flame without plasma. Then, the spatial distribution of O demonstrates significant differences between the unburnt and burnt zones, revealing the distinct mechanisms of O production in unburnt and burnt NH3/air mixtures. Specifically, a new O region is formed in the burnt zone of the lean flame, which is probably mainly caused by the pathway of NO dissociation into O by the ns plasma. Furthermore, the temporal dynamics of O in different zones are discussed in-depth. In the unburnt zone, from the continuous increment of O after hundreds of ns following the ns discharge initiation, it can be seen that the relaxation of the excited nitrogen plays an equally important role in O production as the direct electron impact. Subsequently, O atoms in the unburnt zone exhibit an exponential decay, which is attributed to the formation of O3 from O. Whereas, in the burnt zone, a bi-exponential decay of O is found for the first time. Such decay mainly results from the reaction between O and H2O, which importantly, is a reaction to form OH radicals. The transition between decays is due to the formation of the O region in the unburnt zone and the dominance of the combustion kinetics in the post-plasma stage. © 2024 The Author(s)}},
  author       = {{Sun, Jinguo and Ravelid, Jonas and Bao, Yupan and Nilsson, Sebastian and Konnov, Alexander A and Ehn, Andreas}},
  issn         = {{1540-7489}},
  language     = {{eng}},
  number       = {{1-4}},
  publisher    = {{Elsevier}},
  series       = {{Proceedings of the Combustion Institute}},
  title        = {{Dynamics of atomic oxygen production in an NH3/air flame assisted by a nanosecond pulsed plasma discharge}},
  url          = {{http://dx.doi.org/10.1016/j.proci.2024.105477}},
  doi          = {{10.1016/j.proci.2024.105477}},
  volume       = {{40}},
  year         = {{2024}},
}