Synchronisation behaviour between two candle flame oscillators with similar and dissimilar amplitudes of oscillations

Interactions between a couple of flames often lead to their synchronisation. Flame–flame interaction has recently been linked with thermoacoustic instability in combustors. However, synchronisation caused by the interaction of coupled flames is still not fully understood. Furthermore, the interacting flame oscillators in practical situations often have a slight dissimilarity between them. Here, we systematically study the effects of such dissimilarity on the flame–flame interaction with a simple system consisting of two candle flame oscillators (CFO). The interaction is studied with CFOs having similar and dissimilar amplitudes of oscillations. The distance between the CFOs is parametrically varied. The results indicate that the synchronisation phenomena caused by flame–flame interaction have a complex dependence on the distance between the oscillators. Further, we find the flame–flame interaction to be significantly affected by the dissimilarity of the interacting oscillators. In-phase (IP) synchronisation occurs when the interacting oscillators are separated by a low distance and the oscillators have similar or moderately dissimilar amplitudes of oscillations. On the other hand, for large disparities in the amplitudes of oscillations, lag synchronisation (LS) is observed at a low distance between the CFOs. If the interacting oscillators have similar amplitudes of oscillations, the amplitude death (AD) regime persists throughout the operating range except at a low distance between the CFOs. In contrast, if the interacting oscillators have dissimilar amplitudes of oscillations, different rich dynamical states such as lag synchronisation and partial amplitude death are encountered in addition to amplitude death as the distance between the oscillators is varied. This study might be useful to understand synchronisation due to flame–flame interaction in modern multi-burner turbulent combustors where the constituent burners often have inherent dissimilarities.

多股火焰间的相互作用常会引发同步现象。近年来，火焰间相互作用被证实与燃烧室中的热声不稳定性密切相关。然而，耦合火焰相互作用所引发的同步现象仍未被完全阐明。此外，实际工况中的相互作用火焰振子往往存在细微的性能差异。为此，本文采用由两个蜡烛火焰振子（Candle Flame Oscillators, CFO）构成的简易系统，系统性探究此类差异性对火焰间相互作用的影响。实验分别针对振荡振幅相同与相异的CFO展开研究，并对CFO间的间距进行参数化调节。研究结果显示，火焰间相互作用引发的同步现象与振子间距存在复杂的依赖关系，同时相互作用振子的差异性会对火焰间相互作用产生显著影响。当振子间距较小时，若振荡振幅相近或仅存在中等程度差异，则会出现同相（IP）同步；反之，当振荡振幅差异较大时，在CFO间距较小的工况下可观测到滞后同步（LS）。若相互作用振子的振荡振幅一致，则振幅死亡（AD）区域会覆盖整个运行区间，仅在CFO间距较小时例外。与之相对，当相互作用振子的振荡振幅存在差异时，随着振子间距的调节，除振幅死亡现象外，还会观测到滞后同步、部分振幅死亡等多种丰富的动力学状态。本研究可为理解现代多燃烧室湍流燃烧室中的火焰间同步现象提供参考，此类燃烧室的各组成燃烧室往往存在固有的性能差异。