Hydrodynamic instability and shear layer effects in turbulent premixed combustion
Hydrodynamic instability and shear layer effects in turbulent premixed combustion
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DOI：
10.1063/1.4940161
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发表时间：
2016-01
影响因子：
4.6
通讯作者：
S. Schlimpert;A. Feldhusen;Jerry H. Grimmen;B. Roidl;M. Meinke;W. Schröder
中科院分区：
文献类型：
--
作者：
S. Schlimpert;A. Feldhusen;Jerry H. Grimmen;B. Roidl;M. Meinke;W. Schröder
采用大涡模拟方法对湍流预混平面射流火焰进行了数值模拟。分析表明，当气体膨胀效应较小时，剪切层效应对火焰前缘的扰动有很大影响，导致火焰底部的火焰前缘振幅比高气体膨胀比时大。然而，流体动力学不稳定性的影响，诱导一个不断增加的火焰前锋的振幅，从而产生一个增强的火焰袋产生在火焰尖端。这两种现象通过由贡献系数决定的火焰前缘偏转来影响湍流燃烧面积和燃烧面积率响应的大小。该系数代表火焰和流动之间的相互作用。在低气体膨胀比，总的热释放率谱的contraentflame更广泛的斯特劳哈尔数的主要模式，这是链接到平均火焰高度振荡。因此，在低的气体膨胀比，涡流火焰相互作用是由火焰在涡流可以扰动火焰前锋更强的意义上，阻尼较小。之前在圆形射流火焰中发现的St-2.2的总热释放速率趋势也在现实气体膨胀比下确定为当前的狭缝射流，表明能量从大火焰结构转移到小火焰结构的一般趋势。在高气体膨胀比下，Markstein长度的增加导致了低频范围1 < St < 10内相邻主模态之间的能量转移，燃烧面积率响应对湍流狭缝火焰的总放热率谱变得更加重要，这与层流预混平面火焰的最新研究结果一致。
A turbulent premixed plane jet flame is analyzed by large-eddy simulations. The analysis shows that the flame front wrinkling is strongly influenced by the shear layer effect when the gas expansion effects are small leading to larger flame front amplitudes at the flame base than at high gas expansion ratios. However, the hydrodynamicinstabilityeffect induces a continuously increasing flame front amplitude which yields an enhanced flame pocket generation at the flame tip. Both phenomena influence the magnitude of the turbulent burning area and burning area rate response through the flame front deflections which are determined by the contribution coefficient. This coefficient represents the mutual interaction between the flame and the flow. At low gas expansion ratios, the total heat release rate spectra of the turbulentflame are wider in terms of dominant modes at Strouhal numbers which are linked to the mean flame height oscillations. Thus, at low gas expansion ratios, the vortex-flame interaction is less damped by the flame in the sense that vortices can perturb the flame front stronger. The total heat release rate trend of St−2.2 previously found for a round jet flame is also determined for the current slot jet at realistic gas expansion ratios indicating a general tendency to transfer energy from large to small flame structures. At high gas expansion ratios, an increasing Markstein length leads to an energy transfer between neighboring dominant modes in the low frequency range 1 < St < 10 and the burning area rate response becomes more important for the total heat release rate spectra of the turbulent slot flames which agrees with recent findings for a laminar premixed plane flame.