富氢预混燃烧上游火焰传播的参数研究：旋流、几何形状和预混度的影响
Parametric study of upstream flame propagation in hydrogen-enriched premixed combustion: effects of swirl, geometry and premixedness
摘要：
采用大涡模拟（LES）和增稠火焰（TF）模型研究了旋流、预混度和几何形状对富氢预混火焰的影响。通过改变旋流强度，研究了旋流对大气条件下预混燃烧室火焰特性的影响。此外，还改变了预混合度和几何形状的水平，以研究这些量对火焰行为的作用。采用TF模型对湍流场和化学反应进行耦合。在LES-TF方法中，火焰前锋通过人工加厚在计算网格上求解，并且使用Arkenius化学指定的反应速率直接求解单个物质传输方程。良好的协议时，发现与公布的实验数据，包括预测RMS波动的预测比较。此外，结果表明，较高的旋流强度和预混程度的增加，使系统更容易受到上游火焰运动，由于更高的可燃性的氢，这增加了沿火焰前锋的反应，从而提高了反应区的温度，并导致燃烧诱导的涡流破裂（CIVB）。此外，上游火焰运动总是观察到在较高的旋流强度，无论水平的预混和燃烧器的几何形状，而预混系统表现出稳定的行为，而在低旋流操作。
英文摘要：
The effect of swirl, premixedness and geometry has been investigated for hydrogen enriched premixed flame using Large Eddy Simulation (LES) with a Thickened Flame (TF) model. Swirl strength has been varied to study the effects of swirl on flame behavior in a laboratory-scale premixed combustor operated under atmospheric conditions. In addition, the levels of premixedness and geometry have also been changed to study the role of these quantities on flame behavior. The turbulent flow field and the chemistry are coupled through TF model. In the LES-TF approach, the flame front is resolved on the computational grid through artificial thickening and the individual species transport equations are directly solved with the reaction rates specified using Arrhenius chemistry. Good agreement is found when comparing predictions with the published experimental data including the predicted RMS fluctuations. Also, the results show that higher swirl strength and increase in level of premixedness make the system more susceptible to upstream flame movement due to higher combustibility of hydrogen, which increases the reaction along the flame front, thereby raises temperature in the reaction zone and leads to combustion induced vortex breakdown (CIVB). Moreover, upstream flame movement is always observed at higher swirl strength irrespective of level of premixedness and burner geometry, whereas the premixed systems exhibit stable behavior while operating at low swirl.
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