Study on the mechanism of polycyclic aromatic hydrocarbons and soot formation in ethylene/hydrogen/ammonia laminar diffusion flames

IF 5.8 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame Pub Date : 2025-04-15 DOI:10.1016/j.combustflame.2025.114168

Yang Wang , Ke Liu , Kun Luo , Kunzhuo Chang , Mingyan Gu

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引用次数: 0

Abstract

Ammonia, as an excellent zero-carbon hydrogen storage energy source, presents a significant research focus in the field of combustion regarding how to achieve efficient and clean combustion. The combustion of hydrocarbon fuels with hydrogen-ammonia addition can enhance ammonia combustion performance, reduce carbon emissions from hydrocarbon fuels, and control soot formation; however, the underlying mechanisms remain unclear. This study uses the CoFlame code to simulate the evolution of soot formation in ethylene/hydrogen/ammonia co-flow laminar diffusion flames and analyzes the mechanisms of polycyclic aromatic hydrocarbons formation and growth influenced by hydrogen-ammonia addition. The study found that the predicted soot volume fraction and average primary particle diameter align well with experimental measurements, indicating that the suppressive effect of hydrogen-ammonia addition increases as the hydrogen/ammonia ratio decreases. The addition of hydrogen-ammonia suppresses the nucleation, surface growth, and agglomeration processes of soot in the ethylene flame. The normalization study indicates that the rates of soot nucleation and surface growth align more closely with the evolution of soot volume fraction, making them the primary contributors to the reduction in soot volume fraction. This is identified as the primary reason for the reduction in soot volume fraction. Reaction pathway analysis indicates that the most significant reaction pathway for the gradual formation of pyrene from A₁ under the influence of small molecular components and free radicals in the ethylene/hydrogen/ammonia flame is as follows: A₁→indene→indenyl→A₂R₅→A₂→A₂⁻→A₃⁻→A₄. Quantitative analysis reveals that the chemical effect of hydrogen-ammonia addition effectively suppresses the hydrogen extraction reaction of A₂ by reducing the concentration of hydrogen radicals, thereby decreasing the formation rate of A₄.

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乙烯/氢/氨层流扩散火焰中多环芳烃及烟尘形成机理的研究

氨作为一种优秀的零碳储氢能源，如何实现高效、清洁的燃烧是燃烧领域的重要研究热点。在烃类燃料中添加氢-氨可以提高烃类燃料的氨燃烧性能，降低烃类燃料的碳排放，控制烟灰的形成；然而，潜在的机制仍不清楚。本研究利用CoFlame程序模拟了乙烯/氢/氨共流层流扩散火焰中烟灰形成的演化过程，分析了氢-氨加量对多环芳烃形成和生长的影响机理。研究发现，预测烟尘体积分数和平均初级颗粒直径与实验结果吻合较好，表明氢氨添加的抑制效果随着氢氨比的减小而增强。氨氢的加入抑制了乙烯火焰中烟灰的成核、表面生长和团聚过程。归一化研究表明，煤烟成核速率和表面生长速率与煤烟体积分数的演化更为一致，是煤烟体积分数降低的主要原因。这被认为是降低烟尘体积分数的主要原因。反应途径分析表明，在乙烯/氢/氨火焰中小分子组分和自由基的影响下，由A1逐渐生成芘的最显著的反应途径为：A1→indene→indenyl→A2R5→A2→A2−→A3−→A4。定量分析表明，氨水加氢的化学效应通过降低氢自由基的浓度，有效抑制了A2的提氢反应，从而降低了A4的生成速率。

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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.