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.

使用有限体积大涡模拟方法求解可压缩 Navier-Stokes 方程和组合 G 方程进展变量方法来模拟火焰，研究了约束对湍流贫预混旋流火焰的影响。几何形状是 Moeck 等人通过实验研究的燃烧器。[燃烧。Flame, 159, 2650-2668 (2012)] 其中发生进动涡核 (PVC) 和自激热声不稳定性。为了分析限制对 M 形火焰的影响，研究了三种配置，即无限制配置、对称限制配置和非对称限制配置。对称受限配置对应于实验燃烧器，数值结果与测量结果非常吻合。由于在受限配置中注射管下游有更明显的 PVC，受限和非受限配置的流场明显不同。数值结果证实了文献中的实验结果，即限制定义了再循环区和旋流射流的湍流强度。此外，目前的结果表明，由于火焰与燃烧室声学四分之一波模式的共振耦合，在受限配置中发生的热声不稳定性的极限循环幅度在非对称受限配置。由动态模式分析 (DMD) 确定的模式描述了声学四分之一波模式对速度场的影响，仅发生在对称受限配置中。因此，由于火焰的热声不稳定性导致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配置的敏感性，并表明它们的振荡幅度对燃烧室中涡流火焰位置的依赖性。