Large Eddy simulation of confined turbulent boundary layer flashback of premixed hydrogen-air flames
Large Eddy simulation of confined turbulent boundary layer flashback of premixed hydrogen-air flames
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DOI：
10.1016/j.ijheatfluidflow.2018.06.002
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发表时间：
2018-08-01
影响因子：
2.6
通讯作者：
Sattelmayer, T.
中科院分区：
文献类型：
--
作者：
Endres, A.;Sattelmayer, T.
从燃烧室到上游燃烧器混合段的火焰闪回是与预混燃烧相关的固有威胁。尤其对于含氢燃料，边界层回火(BLF)会对燃烧室造成破坏。因此，开发准确预测BLF发病的方法是很重要的。在这项研究中，研究了大涡模拟(LES)再现实验确定的通道内火焰的回火极限的能力。首先，进行了槽道湍流的惰性大涡模拟。次网格湍流由Smagorinsky湍流模型模拟。然后将惰性模拟得到的非定常速度分布用作反应性大涡模拟的入口边界条件。燃烧过程通过有限速率化学和详细的化学动力学来模拟。通过直接从过滤的组分和温度分布计算组分的反应率，忽略了亚网格尺度的湍流-化学相互作用。在物质输运方程中考虑了微分扩散和Soret扩散。结果表明，采用Smagorinsky湍流模型的大涡模拟能较好地再现槽道流动的湍流特性。在得到正确的非定常入口速度分布的情况下，所选择的燃烧模型能够准确地预测受限边界层的起燃。因此，可以得出结论，所选择的燃烧模型再现了与高炉炉膛有关的所有物理效应。此外，结果还表明，当局部流动分离区的尺寸明显超过火焰的熄灭距离时，BLF就会启动。
Flame flashback from the combustion chamber into the upstream burner mixing section is an inherent threat associated with premixed combustion. Especially for hydrogen-containing fuels, boundary layer flashback (BLF) can occur and damage the combustor. It is thus important to develop methods for the accurate prediction of the onset of BLF. In this study, the ability of large eddy simulations (LES) to reproduce experimentally determined flashback limits of flames confined in a channel is investigated. First, inert LES of turbulent channel flow are conducted. Subgrid turbulence is modelled via the Smagorinsky turbulence model. The unsteady velocity profiles obtained from the inert simulations are then used as inlet boundary conditions for the reactive LES. The combustion process is modelled via finite rate chemistry and detailed chemical kinetics. By directly calculating the species reaction rates from filtered species and temperature distributions, turbulence-chemistry interaction of the subgrid scales is neglected. Differential diffusion and Soret diffusion are included in the species transport equations. It is shown that LES with the Smagorinsky turbulence model is capable of reproducing the turbulence characteristics of the channel flow. With the correct unsteady inlet velocity profile the chosen combustion model is capable of accurately predicting the onset of confined BLF. It can thus be concluded that the chosen combustion model reproduces all physical effects relevant to BLF. Furthermore, it is shown that BLF is initiated when the size of local flow separation regions clearly exceeds the quenching distance of the flame.