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

IF 5.8 2区工程技术 Q2 ENERGY & FUELS Combustion and Flame Pub Date : 2025-03-03 DOI:10.1016/j.combustflame.2025.114076

Jinguo Sun, Yupan Bao, Kailun Zhang, Alexander A. Konnov, Mattias Richter, Elias Kristensson, Andreas Ehn

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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.

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来源期刊

Combustion and Flame 工程技术-工程：化工

CiteScore

9.50

自引率

20.50%

发文量

631

审稿时长

3.8 months

期刊介绍： The mission of the journal is to publish high quality work from experimental, theoretical, and computational investigations on the fundamentals of combustion phenomena and closely allied matters. While submissions in all pertinent areas are welcomed, past and recent focus of the journal has been on: Development and validation of reaction kinetics, reduction of reaction mechanisms and modeling of combustion systems, including: Conventional, alternative and surrogate fuels; Pollutants; Particulate and aerosol formation and abatement; Heterogeneous processes. Experimental, theoretical, and computational studies of laminar and turbulent combustion phenomena, including: Premixed and non-premixed flames; Ignition and extinction phenomena; Flame propagation; Flame structure; Instabilities and swirl; Flame spread; Multi-phase reactants. Advances in diagnostic and computational methods in combustion, including: Measurement and simulation of scalar and vector properties; Novel techniques; State-of-the art applications. Fundamental investigations of combustion technologies and systems, including: Internal combustion engines; Gas turbines; Small- and large-scale stationary combustion and power generation; Catalytic combustion; Combustion synthesis; Combustion under extreme conditions; New concepts.