In this paper, we investigate the coupled behvior of the acoustic field in the confinement and the unsteady flame dynamics in a laboratory scale spray combustor. We study this interaction during the intermittency route to thermoacoustic instability when the location of the flame is varied inside the combustor. As the flame location is changed, the synchronization properties of the coupled acoustic pressure and heat release rate signals change from desynchronized aperiodicity (combustion noise) to phase synchronized periodicity (thermoacoustic instability) through intermittent phase synchronization (intermittency). We also characterize the collective interaction between the multiple flamelets anchored at the flame holder and the acoustic field in the system, during different dynamical states observed in the combustor operation. When the signals are desynchronized, we notice that the flamelets exhibit a steady combustion without the exhibition of a prominent feedback with the acoustic field. In a state of intermittent phase synchronization, we observe the existence of a short-term coupling between the heat release rate and the acoustic field. We notice that the onset of collective synchronization in the oscillations of multiple flamelets and the acoustic field leads to the simultaneous emergence of periodicity in the global dynamics of the system. This collective periodicity in both the subsystems causes enhancement of oscillations during epochs of amplitude growth in the intermittency signal. On the contrary, the weakening of the coupling induces suppression of periodic oscillations during epochs of amplitude decay in the intermittency signal. During phase synchronization, we notice a sustained synchronized movement of all flamelets with the periodicity of the acoustic cycle in the system.

在本文中，我们研究了在实验室规模的喷雾燃烧器中，声场在封闭环境中的耦合行为以及不稳定的火焰动力学。我们研究了在燃烧室内部火焰位置发生变化的热声不稳定性的间歇性过程中的这种相互作用。随着火焰位置的改变，耦合的声压和放热速率信号的同步特性从不同步的非周期性（燃烧噪声）变为通过间歇性的相位同步（间歇性）而发生的相位同步的周期性（热声不稳定）。我们还表征了在燃烧室运行中观察到的不同动力状态下，固定在火焰支架上的多个小火焰与系统中的声场之间的集体相互作用。当信号不同步时，我们注意到小火焰显示出稳定的燃烧，而没有明显的声场反馈。在间歇性相位同步的状态下，我们观察到放热率和声场之间存在短期耦合。我们注意到，在多个小火焰和声场的振荡中集体同步的出现导致系统全局动力学中周期性的同时出现。两个子系统中的这种集体周期性导致间歇信号振幅增加的时期内振荡的增强。相反，耦合的减弱导致在间歇信号的幅度衰减的时期内周期性振荡的抑制。