通过延迟声学自反馈抑制湍流热声系统中的极限环振荡
Mitigation of limit cycle oscillations in a turbulent thermoacoustic system via delayed acoustic self-feedback
AI总结：
本文提出通过延迟声学自反馈抑制钝体稳定湍流燃烧室中的极限环振荡，实验表明耦合管长度为基频声学模态波长3/8时实现振幅死亡，并揭示了同步性破坏与正反馈回路中断的抑制机制。
摘要：
我们报告了在钝体稳定的湍流燃烧室中，通过延迟声学自反馈实现极限环振荡的振幅死亡（AD）。这种反馈控制是通过将燃烧室的声场通过一根连接在声驻波波腹位置附近的单一耦合管耦合到其自身来实现的。我们观察到，随着耦合管长度的增加，极限环振荡的振幅和主频率逐渐减小。当耦合管长度接近燃烧室基频声学模态波长的3/8倍时，观察到这些振荡的完全抑制（AD）。同时，当我们接近这种振幅死亡状态时，声压的动力学行为从极限环振荡状态经由间歇性转变为低振幅混沌振荡。我们还研究了随着耦合管长度的增加，非定常火焰动力学与声场之间耦合性质的变化。我们发现，这些振荡之间的时间同步性从同步周期性状态经由间歇性同步转变为去同步非周期性状态。此外，我们揭示了在最优反馈参数下应用延迟声学自反馈能够完全破坏热声不稳定期间燃烧室中存在的流体动力学、声学和热释放率波动之间的正反馈回路，从而抑制不稳定性。我们预计该方法将成为一种可行且具有成本效益的方案，用于抑制实际推进和动力系统中湍流燃烧系统的热声振荡。
英文摘要：
We report the occurrence of amplitude death (AD) of limit cycle oscillations in a bluff body stabilized turbulent combustor through delayed acoustic self-feedback. Such feedback control is achieved by coupling the acoustic field of the combustor to itself through a single coupling tube attached near the anti-node position of the acoustic standing wave. We observe that the amplitude and dominant frequency of the limit cycle oscillations gradually decrease as the length of the coupling tube is increased. Complete suppression (AD) of these oscillations is observed when the length of the coupling tube is nearly 3/8 times the wavelength of the fundamental acoustic mode of the combustor. Meanwhile, as we approach this state of amplitude death, the dynamical behavior of acoustic pressure changes from the state of limit cycle oscillations to low-amplitude chaotic oscillations via intermittency. We also study the change in the nature of the coupling between the unsteady flame dynamics and the acoustic field as the length of the coupling tube is increased. We find that the temporal synchrony between these oscillations changes from the state of synchronized periodicity to desynchronized aperiodicity through intermittent synchronization. Furthermore, we reveal that the application of delayed acoustic self-feedback with optimum feedback parameters completely disrupts the positive feedback loop between hydrodynamic, acoustic, and heat release rate fluctuations present in the combustor during thermoacoustic instability, thus mitigating instability. We anticipate this method to be a viable and cost-effective option to mitigate thermoacoustic oscillations in turbulent combustion systems used in practical propulsion and power systems.
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