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本文采用合成涡方法生成湍流进口条件,对非受限强旋流甲烷/空气贫燃预混火焰进行了大涡模拟研究。模拟结果和实验以及DNS数据符合良好。基于此模拟方法,本文对甲烷火焰掺混氢气和水蒸气,进行了比较研究。研究发现,掺混氢气提高了火焰抗拉伸灭火能力,火焰在外剪切层强湍流作用下形成较厚火焰刷。掺混水蒸气,火焰降温明显,流场轴向速度加速较小,形成较大的当地旋流数。因而,相比于掺混氢气,其回流区更强、更宽。相比于掺混水蒸气,流场轴向速度加速较大的掺氢火焰,其轴向脉动在更强的Kelvin-Helmholtz不稳定性作用下,下游剪切层双峰结构得到了保持并增强。
In this paper, the synthetic vortex method to generate turbulent inlet conditions, non-limited strong swirling methane / air lean combustion premixed large eddy simulation. Simulation results and experiments as well as DNS data are in good agreement. Based on this simulation method, a comparative study was conducted on the methane flame blending of hydrogen and water vapor. It was found that the blending of hydrogen increased the fire resistance of the flame against stretching and the flame formed a thick flame brush under the strong turbulence of the outer shear layer. Admix water vapor, the flame cooling is obvious, the axial acceleration of the flow field is smaller, forming a larger number of local swirl. Thus, the reflow zone is stronger and wider than the hydrogen blended. Compared with the mixed water vapor, the axial velocity of the flow field accelerates greatly, and the bimodal structure of the downstream shear layer is maintained and enhanced under the effect of stronger Kelvin-Helmholtz instability in the axial pulsation. .