Leading edge dynamics of lean premixed flames stabilized on a bluff body
Leading edge dynamics of lean premixed flames stabilized on a bluff body
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DOI：
10.1016/j.combustflame.2017.12.020
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发表时间：
2018-05
影响因子：
4.4
通讯作者：
D. Michaels;A. Ghoniem
中科院分区：
文献类型：
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作者：
D. Michaels;A. Ghoniem
本文研究了稳定在通道海崖体上的甲烷/空气层流预混火焰前缘的动力学特性。利用谐波脉动和阶跃速度变化模拟了火焰对声振荡的响应，这在热声不稳定性研究中是至关重要的。我们使用一个完全解决非定常二维代码与详细的化学和物种运输，耦合传热的海崖体。计算进行了不同的当量比，身体的材料，稳态进口速度阶跃或谐波扰动。结果表明，火焰前缘动力学在St = 0.5附近显示出峰值响应，这表明前缘运动主要是由于适当的点火条件的平流作为尾流再循环流的激励的结果。火焰前缘的运动是流动与火焰相互作用的结果，火焰褶皱的增加是相当可观的。此外，我们表明，锚定平均进一步上游的火焰导致更强的阻尼的剪切层涡，从而削弱涡火焰的相互作用和热释放波动。因此，我们确定了两种不同的机制，火焰前缘的位置和振荡幅度的影响热释放波动。这项研究表明，一个更强的依赖性的整体火焰燃烧和放热波动的火焰前缘动态比以前认识到的潜在作用，它在燃烧动力学。
This paper examines the dynamics of the flame leading edge in a laminar premixed CH4/air flame stabilized on a bluff body in a channel. Harmonic fluctuations and step velocity change are used to simulate the flame response to acoustic oscillations, which are of primary importance in the study of thermo-acoustic instabilities. We use a fully resolved unsteady two-dimensional code with detailed chemistry and species transport, with coupled heat transfer to the bluff body. Calculations were conducted with different equivalence ratios, body materials, and steady state inlet velocity with step or harmonic perturbations. Results reveal that the flame leading edge dynamics displays a peak response around St = 0.5 suggesting that the leading edge motion is mainly due to the advection of appropriate ignition conditions as a result of the excitement of the wake recirculating flow. There is considerable augmentation of the flame wrinkles generated by the flame leading edge motion as result of the flow–flame interaction. Additionally, we show that a flame that anchors on average further upstream leads to stronger damping of the shear layer vortices and thus weaker vortex-flame interaction and heat release fluctuations. Hence, we identify two different mechanisms by which the flame leading edge location and oscillation amplitude impact heat release fluctuations. The study suggests a stronger dependence of the overall flame wrinkling and heat release fluctuations on the flame leading edge dynamics than recognized previously and the potential role it plays in combustion dynamics.