A phenomenological understanding of the multimodal low-frequency oscillating combustion of ammonia induced by filamentary plasma discharge

IF 5.8 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame Pub Date : 2024-09-26 DOI:10.1016/j.combustflame.2024.113748

Yu Wang, Chengdong Kong, Juntao Ao, Hongshen Li, Chengyi Wang, Xiaojiang Wu, Zhongxiao Zhang

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引用次数: 0

Abstract

This work finds that with the assistance of filamentary plasma discharge, the ammonia combustion becomes very complicated with multiple modes, especially including a low-frequency (<2 Hz) oscillating combustion mode. This flame oscillation, which is sensitive to the discharge characteristics and the flow/fuel/boundary conditions, can be further categorized as three sub-modes denoted as Mode C1, C2 and C3. Their transitions occur depending on the flow rate (Q_tot), the equivalence ratio (ϕ) and the temperature of the chamber wall. Detailed dynamic characteristics of flame kernels and flow fields during the oscillating process are further acquired to confirm the changing recirculation zone and the Karlovitz (Ka) number. A phenomenological mechanism based on recirculated energy feedback is thus proposed to explain the oscillating flame. In addition, the S-curve is used to elucidate the plasma impacts on the complicated combustion characteristics, especially the oscillating combustion modes and their transitions. It is found that the folded S-curve can be stretched with the help of plasma discharge. By considering the energy feedback effects, the S-curve can become more stretched with the Da number for extinction (i.e.

D a_{E^{'}}

) being larger than that for ignition (i.e.

D a_{I^{'}}

). Meanwhile, the branch with the Da number between

D a_{I^{'}}

and

D a_{E^{'}}

is unstable and the multiple oscillating combustion modes (i.e. Mode C1-C3) can be categorized on the unstable branch of the stretched S-curve.

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从现象学角度理解丝状等离子体放电诱导氨的多模式低频振荡燃烧

这项研究发现，在丝状等离子体放电的帮助下，氨燃烧变得非常复杂，具有多种模式，特别是包括低频（2 赫兹）振荡燃烧模式。这种火焰振荡对放电特性和流量/燃料/边界条件非常敏感，可进一步分为三种子模式，分别称为模式 C1、C2 和 C3。它们的转换取决于流量（Qtot）、等效比（j）和腔壁温度。在振荡过程中，进一步获取了火焰内核和流场的详细动态特性，以确认不断变化的再循环区和卡尔洛维茨（Ka）数。因此，提出了一种基于再循环能量反馈的现象学机制来解释振荡火焰。此外，S 曲线还用于阐明等离子体对复杂燃烧特性的影响，特别是振荡燃烧模式及其转换。研究发现，在等离子体放电的帮助下，折叠的 S 曲线可以被拉伸。考虑到能量反馈效应，S 曲线的拉伸程度越大，熄灭的 Da 值（即 DaE′）就越大于点火的 Da 值（即 DaI′）。同时，Da 数介于 DaI′ 和 DaE′ 之间的分支是不稳定的，多重振荡燃烧模式（即模式 C1-C3）可归类于拉伸 S 曲线的不稳定分支上。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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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.