Impact of non-symmetric confinement on the flame dynamics of a lean-premixed swirl flame
Impact of non-symmetric confinement on the flame dynamics of a lean-premixed swirl flame
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DOI：
10.1016/j.combustflame.2021.111701
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发表时间：
2021-09
影响因子：
4.4
通讯作者：
S. Herff;K. Pausch;S. Loosen;W. Schröder
中科院分区：
文献类型：
--
作者：
S. Herff;K. Pausch;S. Loosen;W. Schröder
采用有限体积大涡模拟方法求解可压缩Navier-Stokes方程，结合G方程过程变量法模拟火焰，研究了约束对湍流贫油预混旋流火焰的影响。几何形状是由Moeck等人[Combust. Flame，159，2650-2668（2012）]，其中发生旋进涡核（PVC）和自激热声不稳定性。为了分析约束对M形火焰的影响，研究了三种构型，即，无约束构型、对称约束构型和非对称约束构型。计算结果与实验结果吻合较好。受限和非受限配置的流场显著不同，这是由于受限配置中注射管下游的PVC更明显。数值结果证实了文献中的实验结果，即，该限制限定了旋流射流的回流区和湍流强度。此外，目前的研究结果表明，极限环振幅的热声不稳定性，这发生在受限配置由于共振耦合的火焰与声学四分之一波模式的燃烧室，显着减少在非对称的受限配置。由描述声学四分之一波模式对速度场的影响的动态模式分析（DMD）确定的模式仅发生在对称受限配置中。因此，由于热声不稳定性与火焰的声振荡的较低耦合是明显的。结果强调了热声不稳定性对约束结构的敏感性，并表明其振荡幅度对燃烧室中旋流火焰位置的依赖性。
The impact of confinement on a turbulent lean premixed swirl flame is investigated using a finite-volume large-eddy simulation method to solve the compressible Navier-Stokes equations and a combined G-equation progress variable approach to model the flame. The geometry is an experimentally investigated burner by Moeck et al. [Combust. Flame, 159, 2650-2668 (2012)] in which a precessing vortex core (PVC) and a self-excited thermoacoustic instability occur. To analyze the effect of confinement on the M-shaped flame, three configurations are investigated, i.e., an unconfined configuration, a symmetric confined configuration, and a non-symmetric confined configuration. The symmetric confined configuration corresponds to the experimental burner and the numerical results are in good agreement with the measurements. The flow fields of the confined and unconfined configurations differ significantly due to a more pronounced PVC downstream of the injection tube in the confined configurations. The numerical results confirm experimental findings from the literature, i.e., the confinement defines the recirculation zones and the turbulence intensity of the swirling jets. Furthermore, the present results show that the limit-cycle amplitude of the thermoacoustic instability, which occurs in the confined configurations due to a resonant coupling of the flame with the acoustic quarter-wave mode of the combustion chamber, is significantly reduced in the non-symmetric confined configuration. The mode determined by a dynamic mode analysis (DMD) that describes the impact of the acoustic quarter-wave mode on the velocity field only occurs in the symmetric confined configuration. Consequently, a lower coupling of the acoustic oscillations due to the thermoacoustic instability with the flame is evident. The results emphasize the sensitivity of the thermoacoustic instabilities on the confinement configuration and indicate the dependence of their oscillation amplitudes on the location of the swirl flame in the combustion chamber.