In this experimental study on a laboratory-scale turbulent annular combustor with sixteen swirl-stabilized burners, we study the flame-flame and flame-acoustic interactions during different dynamical states associated with the longitudinal mode of the combustor. We simultaneously measure the acoustic pressure and CH* chemiluminescence emission of the flame using a high-speed camera. Upon increasing the equivalence ratio, the combustor undergoes the following sequence of transition: combustion noise (CN) to low-amplitude longitudinal thermoacoustic instability (TAI) through the state of intermittency, and from low-amplitude to high-amplitude longitudinal TAI through a secondary bifurcation. We report the first evidence of secondary bifurcation from low-amplitude TAI to high-amplitude TAI for a turbulent thermoacoustic system which allows us to test the flame response at two different amplitude of perturbation in a natural setting. TAI arises at the first longitudinal mode of the combined burner tube and combustion chamber. The frequency of oscillations remain the same during the above transition. We find a significant difference in the dynamics of the flame interactions during the periodic part of intermittency and low- and high-amplitude TAI. Specifically, during the periodic part of intermittency, the phase difference between the local heat release rate (HRR) measured from various burners show significant phase slips in time. During low-amplitude TAI, there are fewer phase slips among the HRR response of the burners, which result in a state of weak synchronization among the flames. During high-amplitude TAI, we find that the flames are in perfect synchrony amongst themselves and with the pressure fluctuations. We then quantify the degree of temporal and spatial synchronization between different flames, and flames and pressure fluctuations using the Kuramoto order parameter and the phase-locking value. We show that synchronization theory can be conveniently used to characterize and quantify flame-acoustic interactions in an annular combustor.

在这项对具有 16 个涡流稳定燃烧器的实验室规模的湍流环形燃烧器的实验研究中，我们研究了与燃烧器纵向模式相关的不同动态状态下的火焰-火焰和火焰-声学相互作用。我们使用高速相机同时测量火焰的声压和 CH* 化学发光发射。当当量比增加时，燃烧室经历以下转变序列：燃烧噪声 (CN) 通过间歇状态到低振幅纵向热声不稳定性 (TAI)，从低振幅到高振幅纵向 TAI 通过二次分叉。我们报告了湍流热声系统从低幅度 TAI 到高幅度 TAI 二次分叉的第一个证据，这使我们能够在自然环境中测试两种不同扰动幅度的火焰响应。TAI 出现在燃烧器管和燃烧室组合的第一纵向模式。在上述过渡期间，振荡频率保持不变。我们发现在间歇性和低振幅和高振幅 TAI 的周期性部分中火焰相互作用的动力学存在显着差异。具体而言，在间歇性的周期性部分，从不同燃烧器测量的局部热释放率 (HRR) 之间的相位差显示出明显的时间相位滑移。在低振幅 TAI 期间，燃烧器的 HRR 响应中的相位滑移较少，这导致火焰之间的弱同步状态。在高振幅 TAI 期间，我们发现火焰彼此之间以及与压力波动完美同步。然后，我们使用仓本阶参数和锁相值来量化不同火焰之间的时间和空间同步程度，以及火焰和压力波动。我们表明，同步理论可以方便地用于表征和量化环形燃烧器中的火焰-声学相互作用。以及使用仓本阶参数和锁相值的火焰和压力波动。我们表明，同步理论可以方便地用于表征和量化环形燃烧器中的火焰-声学相互作用。以及使用仓本阶参数和锁相值的火焰和压力波动。我们表明，同步理论可以方便地用于表征和量化环形燃烧器中的火焰-声学相互作用。