Effects of swirl intensity on boundary layer flashback in a confined bluff-body swirl burner

IF 6.2 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame Pub Date : 2025-10-07 DOI:10.1016/j.combustflame.2025.114527

Weijie Zhang, Yuncheng Wang, Yuntian Zheng, Hai Wen, Jinhua Wang, Zuohua Huang

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引用次数: 0

Abstract

Swirling bluff-body boundary layer flashback is a critical issue in lean-premixed gas turbine combustors but such flashback processes and the underlying mechanisms have not been well clarified in previous works especially considering different swirl intensities. In this work, effects of swirl intensity on the bluff-body boundary layer flashback of lean-premixed CH₄/air flames were investigated via large eddy simulation (LES) and flamelet-generated manifold (FGM) methods. The numerical results were validated against the flow velocity, flashback speed and flashback mode which were experimentally measured with particle image velocimetry (PIV) and high-speed camera. It is shown that with higher swirl number (SN), the flashback is led by a large-scale flame tongue propagating upstream in the co-swirl direction (Mode I). With lower SN, the counter-swirl flashback is sustainable and dominant to proceed the flashback which is featured with smaller flame bulges propagating upstream against the swirl flow (Mode II). It is found that with lower SN, flashback starts with Mode I but can be transformed to be Mode II and turns back to Mode I again. The reason is revealed to be associated with the different axial and azimuthal components of the swirling velocity, and different flow deflection regions and low-momentum streaks formed upstream the flame tongue, when with different swirl intensity. Meanwhile, the boundary layer flashback with a low SN can be viewed as a non-swirling flashback in channel flows since the flame-induced adverse pressure gradient is examined to cause the velocity deflection during flashback whereas the rotational inertia forces are negligible. In contrast, flashback with a high swirl intensity is dominated by combined effects of the adverse pressure gradient and rotational inertia forces, which can be regarded as non-swirling channel flashback imposed with wall-normal body forces. The results are significant to further deepen understandings of the swirling bluff-body boundary layer flashback and help to improve its theoretical prediction models.

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旋流强度对密闭钝体旋流燃烧器边界层回烧的影响

旋流钝体边界层回闪是稀预混燃气轮机燃烧室的一个关键问题，但以往的研究并未很好地阐明这种回闪过程及其机理，特别是考虑到不同的旋流强度。本文采用大涡模拟（LES）和火焰生成流形（FGM）方法，研究了旋流强度对稀薄预混CH4/空气火焰崖体边界层闪回的影响。数值结果与粒子图像测速（PIV）和高速相机实验测量的流速、闪回速度和闪回模式进行了验证。结果表明，当旋流数（SN）较高时，闪回由同旋流方向上游传播的大规模火焰舌引导（模式I）。当SN较低时，反旋涡闪回持续且占主导地位，其特征是较小的火焰凸起沿旋流上游传播（模式II）。发现当SN较低时，闪回从模式I开始，但可以转换为模式II，然后再转回模式I。其原因与旋流速度的轴向和方位角分量不同、不同旋流强度下火焰舌上游形成不同的流动偏转区和低动量条纹有关。同时，低SN的边界层闪回可以看作是通道流动中的非旋涡闪回，因为在闪回过程中，火焰诱导的逆压梯度会导致速度偏转，而旋转惯性力可以忽略不计。而高旋流强度的闪回主要受逆压梯度和转动惯性力的共同作用，可视为壁面法向力作用下的非旋流通道闪回。研究结果对进一步加深对旋涡型崖体边界层闪回的认识和完善其理论预测模型具有重要意义。

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.