Preferential vaporization effects on multicomponent n-dodecane/iso-octane non-premixed spray cool flames

IF 6.2 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame Pub Date : 2025-09-04 DOI:10.1016/j.combustflame.2025.114453

Wenbin Xu , Bowen Mei , Ziyu Wang , Martin A. Erinin , Andy Thawko , Luc Deike , Yiguang Ju

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引用次数: 0

Abstract

Experimental and numerical studies are performed on the non-premixed n-dodecane/iso-octane spray flames to investigate the effects of preferential vaporization on cool flame extinction and the repetitive autoignition-extinction instability. A well-defined counterflow burner is employed for cool flame studies. Inline holography is used to measure the spray size distribution and the mean droplet diameter, where d₃₂ is 167 μm. Gas chromatography is used to measure the vaporized fuel concentrations. The preferential vaporization is demonstrated by the increased n-dodecane to iso-octane ratio along the centerline from the spray nozzle. The extinction limits of cool flames are examined with three n-dodecane/iso-octane blending ratios at two temperatures respectively below and above the fuel boiling points. It is shown that at the lower temperature of 450 K, the increased preferential vaporization of iso-octane weakens more the low-temperature reactivity of the n-dodecane vapor mixture and leads to a greater decrease in the extinction limits with the increase of the blending ratio compared to pre-vaporized gas cool flames. The repetitive autoignition-extinction instability is examined by measuring the frequency distribution of spray cool flame stabilization time at a near-limit strain rate of 100 s^-1 for the pure n-dodecane and the blended fuel. The temperature rise on the fuel side promotes the preferential vaporization, causing more iso-octane released in the early gasification, which amplifies the instability at higher temperature. One-dimensional monodisperse spray cool flame simulations are performed across a wide range of spray sizes under the measured boundary conditions. With preferential vaporization, most iso-octane vaporizes outside the flame region and the subsequently released n-dodecane vapor is concentrated in the reaction zone for the droplets below 100 μm. For large droplets over 150 μm, more iso-octane is introduced to the reaction zone and the n-dodecane vapor is more dispersed along the droplet trajectory. The present results demonstrate the significant impacts of preferential vaporization on the low-temperature combustion of multicomponent spray. These results will contribute to the advancement of low-temperature combustion technologies with practical liquid fuels.

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多组分正十二烷/异辛烷非预混喷雾冷却火焰的优先汽化效应

对非预混正十二烷/异辛烷喷雾火焰进行了实验和数值研究，探讨了优先汽化对冷却火焰熄灭和重复自燃-熄灭不稳定性的影响。一种定义明确的逆流燃烧器用于冷焰研究。采用在线全息技术测量了喷雾尺寸分布和平均液滴直径，其中d32为167 μm。气相色谱法用于测量汽化燃料的浓度。正十二烷与异辛烷的比值从喷嘴沿中心线升高，证明了优先汽化。在低于和高于燃料沸点的两种温度下，用三种正十二烷/异辛烷混合比考察了冷火焰的熄灭极限。结果表明，在较低的450 K温度下，异辛烷优先汽化的增加使正十二烷蒸汽混合物的低温反应性更弱，与预汽化的气体冷却火焰相比，随着掺比的增加，消光极限的降低幅度更大。通过测量纯正十二烷和混合燃料在近极限应变速率为100 s-1时的喷雾冷却稳定时间的频率分布，考察了重复自燃-熄灭不稳定性。燃料侧温度的升高促进了优先汽化，使异辛烷在气化初期释放更多，从而放大了高温下的不稳定性。在测量的边界条件下，在大范围的喷雾尺寸下进行了一维单分散喷雾冷却火焰模拟。随着优先汽化，大部分异辛烷汽化在火焰区域外，随后释放的正十二烷蒸汽在低于100 μm的液滴内集中在反应区。对于大于150 μm的大液滴，更多的异辛烷被引入反应区，正十二烷蒸汽沿液滴轨迹更分散。研究结果表明，优先汽化对多组分喷雾的低温燃烧有重要影响。这些结果将有助于推进实用液体燃料的低温燃烧技术。

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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.