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A comprehensive study on dynamics of flames in a nanosecond pulsed discharge. Part II: Plasma-assisted ammonia and methane combustion

Sun, Jinguo LU orcid ; Bao, Yupan LU ; Zhang, Kailun LU ; Konnov, Alexander A. LU ; Richter, Mattias LU ; Kristensson, Elias LU and Ehn, Andreas LU (2025) In Combustion and Flame 275.
Abstract
Understanding the flame dynamics in a nanosecond pulsed discharge (NPD) is imperative for the novel technology of plasma-assisted combustion. We conducted a systematic study on the dynamics of atmospheric NPD-assisted flames in single-pulse mode using Rayleigh scattering combined with structured illumination. The study is divided into two parts. Part I detailed the measurements and CH4/air flame response within the first 500 μs after NPD initiation. In Part II, we extend the study from CH4 to NH3, focusing on the dynamics of both CH4/air and NH3/air flames across different timescales from nanoseconds to milliseconds. Results show that: (1) within the first 50 ns, the discharge is concentrated in the NH3/air flame but more diffused and... (More)
Understanding the flame dynamics in a nanosecond pulsed discharge (NPD) is imperative for the novel technology of plasma-assisted combustion. We conducted a systematic study on the dynamics of atmospheric NPD-assisted flames in single-pulse mode using Rayleigh scattering combined with structured illumination. The study is divided into two parts. Part I detailed the measurements and CH4/air flame response within the first 500 μs after NPD initiation. In Part II, we extend the study from CH4 to NH3, focusing on the dynamics of both CH4/air and NH3/air flames across different timescales from nanoseconds to milliseconds. Results show that: (1) within the first 50 ns, the discharge is concentrated in the NH3/air flame but more diffused and large-volume in the CH4/air flame; (2) during 1–100 μs, for both flames, a shockwave is formed in the unburnt zone. Meanwhile, a heated gas channel causes a temperature rise in the burnt zone, and particularly, generates a flame kernel in the unburnt zone; (3) when t > 100 μs, plasma-induced turbulence and intense flame movement are observed. Furthermore, the essential differences between NH3 and CH4/air flames are revealed in both unburnt and burnt zones. In the unburnt zone, the plasma-induced flame kernel in CH4/air flames lasts until even 20 ms, whilst for NH3/air flames, the kernel extinguishes within 500 μs, suggesting a much weaker performance of NPD pulse on NH3 ignition. In the burnt zone, the temperature rise of the NH3/air flame is much smaller than that of the CH4/air flame, indicating a weaker combustion enhancement. These discrepancies cannot be attributed solely to discharge or fuel properties but rather to the plasma-flame coupling. Combining with the discharge morphologies, it is further revealed that the plasma-flame coupling is weaker in NH3/air flames compared to CH4/air flames, pronouncing the role of CH radicals in the chemi-ionization process of CH4/air mixtures. These findings open a promising avenue for advancing plasma-assisted combustion of NH3 and CH4. (Less)
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author
; ; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Nanosecond pulsed discharge (NPD), Plasma-induced dynamics, Plasma-assisted ignition, Plasma-flame coupling, Rayleigh scattering-structured illumination, High-speed photography
in
Combustion and Flame
volume
275
article number
114076
publisher
Elsevier
external identifiers
  • scopus:85219154181
ISSN
0010-2180
DOI
10.1016/j.combustflame.2025.114076
language
English
LU publication?
yes
id
091a1b86-14c6-4fcd-865f-c54cbbf16e3b
date added to LUP
2025-03-08 10:16:12
date last changed
2025-04-04 14:50:04
@article{091a1b86-14c6-4fcd-865f-c54cbbf16e3b,
  abstract     = {{Understanding the flame dynamics in a nanosecond pulsed discharge (NPD) is imperative for the novel technology of plasma-assisted combustion. We conducted a systematic study on the dynamics of atmospheric NPD-assisted flames in single-pulse mode using Rayleigh scattering combined with structured illumination. The study is divided into two parts. Part I detailed the measurements and CH4/air flame response within the first 500 μs after NPD initiation. In Part II, we extend the study from CH4 to NH3, focusing on the dynamics of both CH4/air and NH3/air flames across different timescales from nanoseconds to milliseconds. Results show that: (1) within the first 50 ns, the discharge is concentrated in the NH3/air flame but more diffused and large-volume in the CH4/air flame; (2) during 1–100 μs, for both flames, a shockwave is formed in the unburnt zone. Meanwhile, a heated gas channel causes a temperature rise in the burnt zone, and particularly, generates a flame kernel in the unburnt zone; (3) when t > 100 μs, plasma-induced turbulence and intense flame movement are observed. Furthermore, the essential differences between NH3 and CH4/air flames are revealed in both unburnt and burnt zones. In the unburnt zone, the plasma-induced flame kernel in CH4/air flames lasts until even 20 ms, whilst for NH3/air flames, the kernel extinguishes within 500 μs, suggesting a much weaker performance of NPD pulse on NH3 ignition. In the burnt zone, the temperature rise of the NH3/air flame is much smaller than that of the CH4/air flame, indicating a weaker combustion enhancement. These discrepancies cannot be attributed solely to discharge or fuel properties but rather to the plasma-flame coupling. Combining with the discharge morphologies, it is further revealed that the plasma-flame coupling is weaker in NH3/air flames compared to CH4/air flames, pronouncing the role of CH radicals in the chemi-ionization process of CH4/air mixtures. These findings open a promising avenue for advancing plasma-assisted combustion of NH3 and CH4.}},
  author       = {{Sun, Jinguo and Bao, Yupan and Zhang, Kailun and Konnov, Alexander A. and Richter, Mattias and Kristensson, Elias and Ehn, Andreas}},
  issn         = {{0010-2180}},
  keywords     = {{Nanosecond pulsed discharge (NPD); Plasma-induced dynamics; Plasma-assisted ignition; Plasma-flame coupling; Rayleigh scattering-structured illumination; High-speed photography}},
  language     = {{eng}},
  publisher    = {{Elsevier}},
  series       = {{Combustion and Flame}},
  title        = {{A comprehensive study on dynamics of flames in a nanosecond pulsed discharge. Part II: Plasma-assisted ammonia and methane combustion}},
  url          = {{http://dx.doi.org/10.1016/j.combustflame.2025.114076}},
  doi          = {{10.1016/j.combustflame.2025.114076}},
  volume       = {{275}},
  year         = {{2025}},
}