Ignition and combustion characteristics of boron particles with multilayer oxide structures considering knudsen transition effects

IF 6.2 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame Pub Date : 2025-08-12 DOI:10.1016/j.combustflame.2025.114397

Guangyi Li , Te Sun , Baolu Shi , Qiang Li , Majie Zhao , Ningfei Wang

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Abstract

Boron powder is a promising fuel candidate for powder-fueled scramjet engines due to its high energy density. In this study, a semi-empirical model is developed to describe the ignition and combustion behavior of boron particles by accounting for a multilayer oxide structures and Knudsen transition effects. Ignition characteristics are investigated under constant ambient temperature and oxidizer concentration, with emphasis on the effects of pressure (0.1–10 atm) and particle size (1–40 μm). The ignition delay increases exponentially with decreasing pressure. The pressure exponent exhibits a non-monotonic dependence on the Knudsen number (Kn), attributed to the competition among dominant reaction pathways over varying pressure regimes. For combustion, the mode transition diameter (D_tr), defined via the Damköhler number (Da), decreases with increasing pressure and temperature. This trend reflects a shift in the controlling mechanism between kinetic and diffusive processes, influenced by particle size, ambient temperature, and Langmuir-layer temperature.

Novelty and significance statement: This study presents a novel semi-empirical model that integrates multilayer oxide structures and Knudsen transition effects to capture the ignition and combustion behavior of boron particles under various conditions. Unlike existing models, it includes bidirectional diffusion across oxide layers and the shift between heat transfer regimes. The model explains the non-monotonic pressure dependence of ignition characteristics based on mechanistic analysis. A transition diameter (Dₜᵣ) based on the Damköhler number serves as a new criterion to classify combustion modes. The model achieves high predictive accuracy across a wide range of particle sizes and ambient conditions. These results enhance the understanding of boron combustion mechanisms and support the design and optimization of powder-fueled scramjet propulsion systems.

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考虑knudsen转变效应的多层氧化结构硼颗粒点火燃烧特性

硼粉具有较高的能量密度，是粉末燃料超燃冲压发动机的理想燃料。在本研究中，通过考虑多层氧化物结构和Knudsen转变效应，建立了一个半经验模型来描述硼颗粒的点火和燃烧行为。研究了在恒定环境温度和氧化剂浓度条件下的点火特性，重点研究了压力（0.1 ~ 10 atm）和颗粒尺寸（1 ~ 40 μm）对点火特性的影响。点火延迟时间随压力的降低呈指数增长。压力指数表现出非单调依赖于Knudsen数（Kn），这归因于不同压力制度下优势反应途径之间的竞争。对于燃烧，模式转变直径（Dtr），通过Damköhler数（Da）定义，随着压力和温度的增加而减小。这一趋势反映了控制机制在动力学和扩散过程之间的转变，受粒径、环境温度和朗缪尔层温度的影响。新颖性和意义声明：本研究提出了一种新颖的半经验模型，该模型集成了多层氧化物结构和Knudsen转变效应，以捕捉硼颗粒在不同条件下的点火和燃烧行为。与现有的模型不同，它包括氧化物层之间的双向扩散和传热机制之间的转换。该模型在力学分析的基础上解释了点火特性的非单调压力依赖性。基于Damköhler数字的过渡直径（D´´ᵣ）作为分类燃烧模式的新标准。该模型在广泛的颗粒尺寸和环境条件下实现了很高的预测精度。这些结果增强了对硼燃烧机理的认识，并为粉末燃料超燃冲压发动机推进系统的设计和优化提供了支持。

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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.