Flame base structures of micro-jet hydrogen/methane diffusion flames
Flame base structures of micro-jet hydrogen/methane diffusion flames
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DOI：
10.1016/j.proci.2016.08.034
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
Jian Gao;Akter Hossain;Y. Nakamura
中科院分区：
文献类型：
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作者：
Jian Gao;Akter Hossain;Y. Nakamura
在这项研究中，氢/甲烷-空气扩散火焰的火焰基础结构形成的微小射流进行了数值比较的等温和热传导燃烧器的条件下，以澄清燃料依赖的火焰稳定机制。研究发现，与甲烷火焰不同，氢火焰的火焰底部总是附着在燃烧器上。分析表明，占主导地位的中间消耗步骤具有显着较低的活化能的氢火焰相比，甲烷火焰。更重要的是，其中一个HO 2生成反应（R43 f：H + O2+ M → HO 2 + M），它在维持火焰底部的反应性方面具有主导作用，显示出负的温度依赖性，导致火焰底部核心的热释放速率随着燃烧器壁温的降低而增加。利用导热燃烧器（热导率为16 W/m-K）在宽范围的燃料射流速度（0.5-4.0 m/s）上，发现燃烧器尖端由于其独特的稳定机制而被氢火焰加热到显著更高的温度。然后考虑氢和甲烷的混合效应。研究发现，在燃料流中加入甲烷可以降低燃烧器顶端的温度。这是因为，根据对氢/甲烷射流扩散火焰的结构的研究，R43 f的反应速率由于所包含的中间体（例如，CH 3、CH 2 O）的消耗步骤。期望与火焰基部结构相关联的火焰附着特征可以通过混合氢气和甲烷而容易地控制，使得可以预先控制燃烧器尖端温度。
In this study, a comparison of flame base structures of hydrogen/methane–air diffusion flames formed over a tiny-jet is made numerically for both isothermal and thermal conductive burner conditions, in order to clarify the fuel dependent flame stabilization mechanisms. It is found that, unlike a methane flame, the flame base of a hydrogen flame always attaches to the burner. The analyses indicate that the dominant intermediate-consumption steps have significantly lower activation energies for the hydrogen flame as compared to a methane flame. More importantly, one of the HO2production reactions (R43f: H + O2+ M → HO2+ M), which has a dominant role in sustaining reactivity at the flame base, shows a negative temperature dependence, causing the heat release rate in the flame base kernel to increase as the burner wall temperature decreases. With a thermal conductive burner (thermal conductivity of 16 W/m-K) over a wide range of fuel jet velocities (0.5–4.0 m/s), it is found that the burner tip is heated to a significantly higher temperature by a hydrogen flame due to its unique stabilization mechanism. The mixing effects of hydrogen and methane are then considered. It is found that the burner tip temperature can be reduced by adding methane into the fuel flow. This is because, according to the investigation of the structures of the hydrogen/methane jet diffusion flames, the reaction rate of R43f is suppressed due to the included intermediates (e.g., CH3, CH2O) consumption steps of methane. It is expected that the flame attachment feature associated with the flame base structure can be easily controlled by mixing hydrogen and methane, making it possible to control the burner tip temperature in advance.