Extinction behavior of a partially premixed flame and a nonpremixed flame in turbulent counterflow

IF 6.2 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame Pub Date : 2025-06-20 DOI:10.1016/j.combustflame.2025.114268

Fernando M. Pereira , Francesco Carbone , Jonathan H. Frank , Bruno Coriton , Philip Wang , Alessandro Gomez

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Abstract

The present study experimentally investigates non-flamelet behavior leading to extinction in a NonPremixed Flame (NPF) and a Partially Premixed Flame (PPF) in a turbulent counterflow configuration. Both flames at Re_t∼ 900 are indistinguishable in terms of the turbulence properties that are imposed at the cold boundaries and persist up to the mixing layer. For each extinction event, the perturbation that leads to the first breach of the OH layer is tracked back in time in a Lagrangian manner using high-speed stereoscopic PIV and OH-PLIF imaging techniques, allowing the reconstruction of the time sequence of strain rate and vorticity that leads to flame extinction. The NPF is found to be more prone to extinction than the PPF, which is at odds with the computed laminar extinction strain rate, which is 23 % larger in the NPF than in the PPF, implying a greater resistance to strain for the NPF. Extinction appears to be caused by a combination of relatively intense strain rate and/or vorticity pockets interacting with the flame and causing a tear of the OH layer. The maximum strain rate norm exceeds the computed extinction limit in >85 % of the cases for the PPF, whereas it does so in approximately 75 % of the cases for the NPF, revealing a more pronounced strain rate effect on the extinction process for the PPF. Vorticity plays multiple roles in extinction. It manifests itself as: i) a pair of counterrotating vortices approaching the flame from either or both sides, creating a region of high strain rate; ii) a single vortex interacting with the flame by diluting the reactants with inert, thereby, weakening the flame; and iii) a vortex penetrating the oxidizer layer, making it thicker and, possibly, disrupting the laminar flame structure. The last two scenarios may explain extinction without a history of remarkably high strain rates. A 35 % reduction in the overall strain rate of the flames resulted in nearly complete suppression of extinction events in both PPF and NPF.

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紊流逆流中部分预混火焰和非预混火焰的消光行为

本研究通过实验研究了紊流逆流构型中非小火焰在非预混火焰（NPF）和部分预混火焰（PPF）中导致熄灭的非小火焰行为。Ret ~ 900的两种火焰在冷边界处施加的湍流特性方面是难以区分的，并且一直持续到混合层。对于每个消光事件，使用高速立体PIV和OH- plif成像技术，以拉格朗日方式追溯导致OH层首次突破的扰动，从而重建导致火焰消光的应变率和涡度的时间序列。发现NPF比PPF更容易消光，这与计算的层流消光应变率不一致，NPF比PPF大23 %，这意味着NPF对应变的抵抗力更大。消光似乎是由相对强烈的应变率和/或涡量口袋与火焰相互作用并引起OH层撕裂的组合引起的。PPF的最大应变速率范数超过计算的消光极限的情况为>；85 %，而NPF的最大应变速率范数超过计算的消光极限的情况约为75 %，这表明应变速率对PPF的消光过程有更明显的影响。涡度在消光过程中起着多重作用。它表现为：1)一对反向旋转的涡流从一侧或两侧靠近火焰，形成一个高应变率区域；Ii)通过用惰性物质稀释反应物与火焰相互作用的单一涡流，从而减弱火焰；iii)涡流穿透氧化层，使其变厚，并可能破坏层流火焰结构。后两种情况也许可以解释没有高应变率历史的灭绝。火焰的总应变率降低了35% %，导致PPF和NPF几乎完全抑制了熄灭事件。

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.