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首页> 外文期刊>Experimental Thermal and Fluid Science: International Journal of Experimental Heat Transfer, Thermodynamics, and Fluid Mechanics >Influence of flow field scaling on flashback of swirl flames
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Influence of flow field scaling on flashback of swirl flames

机译：流场尺度对旋流火焰回火的影响

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摘要

In this paper, the effect of geometrical scaling on the onset of flashback into a cylindrical premixing zone of a swirl flame is investigated. We discriminate two types of flashback. In the first type of flashback the flame propagates upstream inside an already present axial recirculation zone. This flashback is caused by turbulent burning along the vortex axis (TBVA1) and is controlled by flame extinction inside the recirculation zone. The second type of flashback is caused by combustion induced vortex breakdown (CIVB2). This type of flashback is characterised by the aerodynamic influence of the combustion heat release that leads to propagation of the axial recirculation zone and the flame in upstream direction. To study the effects of geometrical scaling on the flow fields and the two types of flashback, the operation of two geometrically scaled burners are compared at equal Reynolds number. By this method it is possible to observe the flashback phenomena in similar swirl flow fields but with different turbulent scales affecting the combustion process. To check flow field similarity and to indentify the flashback type, the non-reacting and reacting flow fields have been examined by planar particle imaging velocimetry and simultaneous recording of the flame luminescence. It is shown that geometrical scaling of the burner shifts the equivalence ratio at which flashback occurs and that this shift is different for the two types of flashback. Consistency and inconsistency with known scaling and stability criterions is discussed. Analysing the fluid dynamics and turbulent combustion gives a first explanation of why CIVB and TBVA are affected differently by geometrical scaling at constant Reynolds number which is in good agreement with the experimental observations.
机译：在本文中，研究了几何比例缩放对回旋火焰进入旋流火焰的圆柱形预混合区开始的影响。我们区分两种类型的闪回。在第一类型的逆燃中，火焰在已经存在的轴向再循环区域内向上游传播。这种回火是由沿涡轴（TBVA1）的湍流燃烧引起的，并由再循环区内的火焰熄灭控制。第二种类型的反冲是由燃烧引起的涡旋破坏（CIVB2）引起的。这种类型的回火的特征在于燃烧放热的空气动力学影响，导致轴向再循环区和火焰沿上游方向传播。为了研究几何比例缩放对流场和两种回火类型的影响，比较了两个几何比例燃烧器在相同雷诺数下的操作。通过这种方法，可以在相似的旋流流场中观察到反燃现象，但是不同的湍流尺度会影响燃烧过程。为了检查流场的相似性并确定闪回类型，已通过平面粒子成像测速仪和火焰发光的同时记录检查了非反应流场和反应流场。结果表明，燃烧器的几何比例变化使发生回火的当量比发生偏移，并且对于两种类型的回火，该偏移是不同的。讨论了与已知缩放和稳定性标准的一致性和不一致性。分析流体动力学和湍流燃烧，首先解释了为什么CIVB和TBVA在恒定雷诺数下受几何比例变化的影响不同，这与实验观察结果非常吻合。

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