On the segregation of NH3 and H2 within the flame front in premixed turbulent combustion of NH3/H2/N2 blends

IF 6.2 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame Pub Date : 2025-09-05 DOI:10.1016/j.combustflame.2025.114455

Nilanjan Chakraborty , Ruslan Khamedov , Hamid Kavari , Francisco E. Hernández-Pérez , Hong G. Im

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引用次数: 0

Abstract

The study analyses the segregation of NH₃ and H₂ in globally lean premixed turbulent flames of NH₃/H₂ fuel blends using direct numerical simulation (DNS) data of statistically planar turbulent flames. Turbulent premixed flames for two fuel blends, 60%NH₃/25%H₂/15%N₂ and 40%NH₃/45%H₂/15%N₂, with an equivalence ratio of 0.81, were examined in the thin reaction zones regime. Differences in chemical reactivity and differential diffusion between NH₃ and H₂ lead to local variations in equivalence ratio within the flame, significantly affecting species distribution compared to one-dimensional (1D) laminar premixed flames. The equivalence ratio variation within the flame causes locally either stoichiometric or fuel-rich pockets despite the globally lean condition in the cases considered here. This also enables localised diffusion mode burning, which is stronger for H₂ in the 60%NH₃/25%H₂/15%N₂ blend, whereas it is stronger for NH₃ in the case of 40%NH₃/45%/15%N₂ H₂ blend. The transition from lean premixed to non-premixed combustion at the rear end of the flame leads to the misalignment of the normal vectors of NH₃, H₂, and temperature isosurfaces, impacting reaction-diffusion balance. The displacement speeds of H₂ isosurfaces exceed those of NH₃, leading to differences in effective normal strain rates, which along with local equivalence ratio variation, influence the behaviour of the scalar gradient magnitude. These findings suggest that the modelling of premixed combustion of NH₃/H₂ blends must account for variable equivalence ratio combustion and non-premixed burning mode, even for globally lean mixtures.

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NH3/H2/N2共混物预混湍流燃烧中火焰前缘NH3和H2的分离

利用统计平面湍流火焰的直接数值模拟（DNS）数据，分析了NH3/H2燃料混合整体稀薄湍流火焰中NH3和H2的分离。对60%NH3/25%H2/15%N2和40%NH3/45%H2/15%N2两种燃料混合物的湍流预混火焰进行了薄反应区试验，等效比为0.81。与一维（1D）层流预混火焰相比，NH3和H2的化学反应性差异和扩散差异导致火焰内等效比的局部变化，显著影响了物质分布。在这里所考虑的情况下，尽管整体条件稀薄，但火焰内等效比的变化会导致局部化学计量或富燃料口袋。这也使局部扩散模式燃烧成为可能，在60%NH3/25%H2/15%N2混合物中，H2的燃烧更强，而在40%NH3/45%/15%N2 H2混合物中，NH3的燃烧更强。火焰后端由稀预混燃烧过渡到非预混燃烧，导致NH3、H2和温度等面的法向量错位，影响反应扩散平衡。H2等面的位移速度大于NH3等面的位移速度，导致了有效法向应变率的差异，这种差异与局部等效比的变化一起影响了标量梯度大小的行为。这些发现表明，NH3/H2混合物的预混合燃烧模型必须考虑可变当量比燃烧和非预混合燃烧模式，即使是全球稀薄混合物。

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.