Characterizing the influence of thermodiffusive effects on turbulent burning velocity of lean hydrogen/air mixtures using critically stretched laminar flames

IF 5.8 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame Pub Date : 2025-06-30 DOI:10.1016/j.combustflame.2025.114306

Yiqing Wang , Andrei N. Lipatnikov , Zheng Chen

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引用次数: 0

Abstract

This work focuses on characterizing the influence of thermodiffusive effects on turbulent burning velocity (

S_{T}

) of lean hydrogen/air mixtures, employing the so-called leading point concept. To this end, the flame characteristics of 1-D critically stretched laminar flames, including the flame consumption velocity and flame thickness, are extracted from two flame configurations: counter-flow twin premixed flames and spherically expanding flames. The former configuration is solely subject to strain-related stretch, whereas the latter configuration is subject to both strain-related and curvature-related stretches. Lean hydrogen/air mixtures are considered at a wide range of temperatures and pressures, addressed in recent direct numerical simulations (DNS) of turbulent, premixed, lean hydrogen/air flames (Wang et al., 2024). It is found that the critically stretched flame consumption velocities obtained from these two configurations are closely aligned, while the flame thickness obtained from the spherically expanding flames is substantially greater than that from the counter-flow twin premixed flames. Capabilities of these flame characteristics for capturing the thermodiffusive effects on

S_{T}

are demonstrated by incorporating these characteristics into fits to

S_{T}

dataset obtained from the aforementioned DNS study. Various definitions of flame thickness are also examined, with the thickness of fuel consumption zone showing the best performance. These findings support the leading point concept and imply that both critically strained planar flames and highly curved spherically expanding flames could be used to characterize the local burning state at the leading edges of turbulent lean premixed hydrogen flames.

Novelty and Significance Statement

The novelty of this research consists of comparing characteristics of critically stretched laminar flames, extracted from two flame configurations, i.e., twin planar counterflow flames and highly curved spherical flames. The results show that flame consumption velocities are approximately equal in these two extreme cases if complex chemistry of lean hydrogen burning is taken into account. Furthermore, for the first time to the authors’ knowledge, the results (i) validate the leading point concept under conditions of fixed Karlovitz and Damköhler numbers, but different pressures and temperatures, (ii) indicate utility of characteristics of highly curved spherically expanding flames within the framework of this concept, and (iii) imply that the width of fuel consumption zone is better suited for evaluating thicknesses of critically stretched laminar flames (again within the framework of this concept). It is significant because prediction of high turbulent burning velocities, well documented in lean hydrogen/air mixtures, challenges the combustion community from the fundamental perspective and is of critical importance for the design and development of hydrogen-fueled engines.

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用临界拉伸层流火焰表征热扩散效应对稀薄氢/空气混合物湍流燃烧速度的影响

本工作着重于表征热扩散效应对贫氢/空气混合物湍流燃烧速度（ST）的影响，采用所谓的先导点概念。为此，从逆流双预混火焰和球膨胀火焰两种火焰形态中提取一维临界拉伸层流火焰的火焰特性，包括火焰消耗速度和火焰厚度。前一种构型仅受应变相关拉伸，而后一种构型同时受应变相关拉伸和曲率相关拉伸。在最近的湍流、预混、贫氢/空气火焰的直接数值模拟（DNS）中，考虑了在广泛的温度和压力范围内的贫氢/空气混合物（Wang et al., 2024）。结果表明，两种结构的临界拉伸火焰消耗速度基本一致，而球形膨胀火焰的火焰厚度明显大于逆流双预混火焰。通过将这些特征整合到从上述DNS研究中获得的ST数据集的拟合中，证明了这些火焰特征捕获热扩散效应的能力。对火焰厚度的各种定义也进行了考察，其中燃油消耗区的厚度表现出最好的性能。这些发现支持了先导点概念，并暗示临界应变平面火焰和高弯曲球扩张火焰都可以用来表征湍流贫预混氢火焰前缘的局部燃烧状态。新颖性和意义声明本研究的新颖性在于比较了从两种火焰构型中提取的临界拉伸层流火焰的特性，即双平面逆流火焰和高弯曲球形火焰。结果表明，考虑贫氢燃烧的复杂化学过程，两种极端情况下的火焰消耗速度基本相等。此外，据作者所知，结果(i)在固定Karlovitz和Damköhler数但不同压力和温度的条件下验证了引点概念，（ii）表明了在该概念框架内高弯曲球膨胀火焰特性的有效性。并且（iii）意味着燃料消耗区的宽度更适合于评估临界拉伸层流火焰的厚度（再次在此概念的框架内）。这是非常重要的，因为在稀薄的氢/空气混合物中，高湍流燃烧速度的预测从基本的角度挑战了燃烧界，对氢燃料发动机的设计和开发至关重要。

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.