Investigation of temporal variation of combustion instability intensity in a back step combustor using LES
Investigation of temporal variation of combustion instability intensity in a back step combustor using LES
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使用 LES 研究后步燃烧器中燃烧不稳定性强度的时间变化
DOI：
10.1299/jtst.2020jtst0036
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发表时间：
2020
影响因子：
1.2
通讯作者：
R. Kurose
中科院分区：
文献类型：
--
作者：
J. Nagao;L. Abhishek;R. Kurose
稀薄燃烧容易产生燃烧不稳定，特别是压力振荡，这对燃烧室造成了严重的损害。为了防止这种情况，许多研究试图阐明这一现象。然而，由于其复杂性，对其物理机制的理解仍然不完整。本文采用大涡模拟（Large Eddy Simulation， LES）研究了稀薄燃料条件下湍流喷雾燃烧的燃烧不稳定性。燃烧室有一个面向后的台阶，煤油燃料滴从台阶的上游垂直喷射。湍流燃烧模型采用动态增厚火焰模型，煤油-空气火焰采用两步全局反应模型。采用压力振荡对燃油雾化性能的影响模型，预测喷射燃油液滴的平均直径随时间的变化。等效比设置为0.6、0.8、1.0。结果表明：燃烧不稳定性随当量比的减小而减小；然而，在最低等效比为0.6时，观察到一个独特的现象。这里的独特现象是压力振荡振幅随时间的变化，其行为在其他一些研究中也有观察到。在此条件下，压力振荡的频率在时间上是恒定的，而放热速率的频率随时间的变化而变化。此外，放热速率的空间分布随时间的变化而变化。它们引起压力与放热率相关性的时间变化，最终导致压力振荡幅度的时间变化。
Lean combustion is susceptible to combustion instabilities, especially pressure oscillation, and this severely damages the combustor. To prevent this, many studies have attempted to elucidate this phenomenon. However, the physical understanding of the mechanism is still incomplete owing to its complexity. In this study, combustion instability in turbulent spray combustion in lean fuel condition is investigated using Large Eddy Simulation (LES). The combustion chamber has a backward facing step, and kerosene fuel droplets are injected vertically just upstream from the step. The dynamic thickened flame model is used as the turbulent combustion model, and a two-step global reaction model is used for kerosene-air flames. The influence of pressure oscillation on fuel atomization behavior is considered using a model, which predicts the Sauter Mean Diameter of injected the fuel droplets with time. The equivalence ratio is set as 0.6, 0.8, and 1.0. The results show that combustion instability is observed in all cases, and the intensity of combustion instability decreases with a decrease in the equivalence ratio; however a unique phenomenon is observed for the lowest equivalence ratio of 0.6. The unique phenomenon here is the time variation of amplitude of pressure oscillation, whose behavior has been also observed in some other studies. At this condition, while the frequency of pressure oscillation is temporally constant, the frequency of heat release rate varies with time, which is investigated with newly proposed index Time Gap. In addition, the spatial distribution of heat release rate temporally changes with varying frequency. They cause the time variations of correlation between pressure and heat release rate, and finally the amplitude of pressure oscillation temporally varies.
影响因子：
2.9
作者：
Gotoda, Hiroshi;Nikimoto, Hiroyuki;Tachibana, Shigeru
通讯作者：
Tachibana, Shigeru