Thermal and chemical structures formed in the micro burner of miniaturized hydrogen-air jet flames
Thermal and chemical structures formed in the micro burner of miniaturized hydrogen-air jet flames
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DOI：
10.1016/j.proci.2014.08.008
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
Akter Hossain;Y. Nakamura
中科院分区：
文献类型：
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作者：
Akter Hossain;Y. Nakamura
通过数值模拟研究了微型燃烧器中形成的热结构和化学结构，这些结构可能导致微型射流扩散火焰通过燃烧器壁的过量热再循环的独特稳定机制。气相中考虑二维轴对称的含化学反应的热质输运过程，固相中考虑热输运过程。燃烧器的材料和燃料喷射速度被认为是主要的数值参数，以检查燃烧器的燃烧器内的热和化学结构的作用。骨架反应机理包括12步化学反应和9种物质被用来考虑自由基的产生/消耗，以及它们在燃烧器中的传输。结果表明，采用低导热率燃烧器时，即使在通常会发生熄火的非常小的雷诺数下，微小火焰也能稳定。这是由于有效地利用了从火焰传递到燃烧器的热量，以提高稳定性，这是由于（1）预热进入的燃料，（2）从火焰朝向燃烧器尖端的最小热损失，以及（3）提高了燃烧器内部的反应性。在具有低传导燃烧器的这种低雷诺数射流中，环境空气可以容易地扩散回到燃烧器中，并且然后促进燃烧器尖端附近的氧化反应。因此，火焰结构沿着轴线被显著地改变，超出了典型的1-D火焰。建议通过考虑燃烧器内表面处的催化反应或使用含氧燃料（如乙醇或醚）来促进在实质加热的微燃烧器中的进一步化学过程。
The thermal and chemical structure formed in the micro burner potentially leading to the unique stability mechanism of miniaturized jet diffusion flame via excess heat recirculation through the burner wall, is studied numerically. 2-D axis-symmetric heat and mass transport processes with chemical reactions are considered in gas phase, while the heat transport process is considered in solid phase. The burner materials and fuel ejecting velocities are considered as the main numerical parameters in order to examine the role of the burner on the thermal and chemical structure inside the burner. A skeletal reaction mechanism consists of twelve steps chemical reactions and nine species is applied to consider the radical generation/consumption, and their transport in the burner. It is found that the tiny flame is stabilized even with extra-ordinary small Reynolds number, at which an extinction is generally experienced, when the low conductivity burner is adopted. This is due to the effective usage of the transferred heat from the flame to the burner to improve the stability owing to (1) preheating the incoming fuel, (2) the least heat loss from the flame toward the burner tip, and (3) enhancing the reactivity inside the burner. In such low Reynolds number jet flow with the low conductive burner, ambient air can easily diffuse back into the burner and oxidative reactions at the vicinity of the burner tip is then promoted. Accordingly, the flame structure along the axis is dramatically modified beyond the typical 1-D flame. It is suggested that the further chemical process could be promoted in the substantially-heated micro burner by considering the catalytic reaction at the inner burner surface or using oxygenated fuel likely alcohol or ether.