This paper presents a large eddy simulation (LES) of a generic sequential combustor that was operated at atmospheric pressure and that features a thermoacoustic instability at 145 Hz. The full test rig consisting of a first stage plenum, burner and combustion chamber, of an air dilution section and of a sequential stage combustor was modeled. A compressible reactive 3-D LES was performed with semi-detailed chemistry accounting for different combustion modes which are all involved in the sequential combustor flame dynamics. These modes are flame propagation at ambient and elevated temperatures, and autoignition. The simulation is compared to experiments that featured hydroxide planar laser-induced fluorescence (OH-PLIF), OH* chemiluminescence optical diagnostics, and acoustic pressure measurements. Both flames show strong oscillatory dynamics that are remarkably well captured by the LES. The mode shape of the self-excited instability extracted from the LES pressure signals is also in very good agreement with the experiment. An analysis of the LES sequential flame dynamics shows that autoignition lengths in the mixing section are strongly modulated due to self-sustained out-of-phase oscillations of mixing temperature and axial velocity, which lead to strong oscillations of the reaction zone location.

本文介绍了一个通用的顺序燃烧器的大涡模拟（LES），该燃烧器在大气压下运行，并具有145 Hz的热声不稳定性。对由第一级气室，燃烧器和燃烧室，空气稀释段和顺序燃烧室组成的完整测试装置进行了建模。进行了可压缩的反应性3-D LES，采用半详细化学说明了不同的燃烧模式，这些燃烧模式都与顺序燃烧器的火焰动力学有关。这些模式是环境温度和高温下的火焰传播以及自燃。将模拟与以氢氧化物平面激光诱导的荧光（OH-PLIF），OH *化学发光光学诊断和声压测量为特色的实验进行了比较。两种火焰都显示出强烈的振荡动力学，LES很好地捕获了这些动力学。从LES压力信号中提取的自激不稳定性的模态形状也与实验非常吻合。对LES顺序火焰动力学的分析表明，由于混合温度和轴向速度的自持异相振荡，混合区中的自燃长度受到强烈调节，从而导致反应区位置的强烈振荡。