Stabilization mechanism of turbulent premixed flames in strongly swirled flows
Stabilization mechanism of turbulent premixed flames in strongly swirled flows
复制标题
强旋流中湍流预混火焰的稳定机制
DOI：
10.1080/13647830500448347
复制
发表时间：
2006
影响因子：
1.3
通讯作者：
F. Biagioli
中科院分区：
文献类型：
--
作者：
F. Biagioli
采用简单的一维边界层模型和计算流体力学方法，主要在大涡模拟水平上，研究了ALSTOM En-Vironmental（EV）双锥燃烧器在强旋流中发生涡破裂时湍流预混火焰的稳定性。分析表明，由于火焰曲率效应，燃烧室轴线上的火焰速度比湍流燃烧速率低2 D t/RF，其中D t为特征湍流扩散系数，RF为火焰曲率半径。用一维模型解释了实验中观察到的负速度火焰传播现象，即火焰完全嵌入对称轴上的中心回流区，这是由于因子2 D t/RF大于特征湍流燃烧速率所致。一个特殊的突然位移的火焰锚定位置深入到燃烧器，这发生在实验上的当量比的临界值，但是不能解释与目前的一维方法，由于建模假设。在这种情况下，大涡模拟可以准确地再现整个操作范围内的火焰行为，支持数学分析。最后表明，稳定RANS方法不能科普的问题，由于他们无法正确地预测该燃烧器的速度流场。
The stabilization of turbulent premixed flames in strongly swirled flows undergoing vortex breakdown is studied in the case of the ALSTOM En-Vironmental (EV) double cone burner using a simple one-dimensional boundary layer type model and computational fluid dynamics, mainly at the level of large-eddy simulation. The analysis shows that, due to flame curvature effects, the flame speed on the combustor axis is 2 D t/R F lower than the turbulent burning rate, where D t is a characteristic turbulent diffusion coefficient and R F the flame radius of curvature. Flame propagation with negative speed observed in the experiments, i.e. the flame completely embedded in the central recirculation zone on the symmetry axis, is explained with the one-dimensional model as caused by the factor 2 D t/R F being larger than the characteristic turbulent burning rate. A peculiar sudden displacement of the flame anchoring location deep into the burner, which takes place experimentally at a critical value of the equivalence ratio, cannot however be explained with the present one-dimensional approach due to the modelling assumptions. The mathematical analysis is supported in this case with large-eddy simulation which can accurately reproduce the flame behaviour across the full operating range. It is finally shown that steady RANS methods cannot cope with the problem due to their inability to correctly predict the velocity flowfield in this burner.