Abstract The unsteady response of a flame to acoustic or flow perturbations plays a crucial role in thermoacoustic combustion instability. The majority of studies on this subject presents and analyzes flame dynamics in the frequency domain by means of a flame transfer function or a flame describing function. The present review concentrates on work that adopts a time-domain perspective. In such a framework, the linear dynamics of an acoustically compact flame is completely characterized by its impulse response. The concept of distributed time delays emerges as an appropriate description of the convective transport of flow and flame perturbations. A time-domain perspective facilitates the physics-based interpretation of important features of the flame response and supports the development of passive or active means of stability control. The present review first provides mathematical background on linear time-invariant systems and introduces the impulse response as a quantity that fully characterizes the dynamics of such systems. It will then be shown by way of example how typical features of the frequency response of premixed flames can be generated in a very natural, physically intuitive manner from time delay distributions. Analytical results for the impulse response of laminar premixed flames to modulations of velocity or equivalence ratio are presented in a unified framework. The next chapter discusses low-order parametric models, which exploit prior knowledge on the underlying convective processes that govern the flame dynamics, but nevertheless require input from experiment or high-fidelity simulation to fix parameter values. Next, a variety of approaches devised to derive distributed time delay models of flame dynamics from simulation data are reviewed. The most recent developments, which combine large eddy simulation of turbulent combustion with system identification, have demonstrated that it is possible to estimate reduced-order models of flame dynamics that are quantitatively accurate even for complex, swirling flame in geometries of technical interest. The last chapter reviews work on acoustically non-compact flames, strategies for passive control of thermoacoustic instabilities that exploit distributed delays, and the effect of convective dispersion on the time delay distribution and strength of entropy waves.

中文翻译：

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基于分布式时间延迟的预混火焰动力学建模与分析

摘要 火焰对声学或流动扰动的非稳态响应在热声燃烧不稳定性中起着至关重要的作用。大多数关于这个主题的研究通过火焰传递函数或火焰描述函数来呈现和分析频域中的火焰动力学。本次审查集中于采用时域视角的工作。在这样的框架中，声学上紧凑的火焰的线性动力学完全以其脉冲响应为特征。分布式时间延迟的概念是作为对流动和火焰扰动的对流传输的适当描述而出现的。时域视角有助于对火焰响应的重要特征进行基于物理学的解释，并支持开发被动或主动稳定性控制手段。本综述首先提供了线性时不变系统的数学背景，并将脉冲响应作为一个完全表征此类系统动力学的量。然后将举例说明如何从时间延迟分布中以​​非常自然、物理直观的方式生成预混火焰的频率响应的典型特征。层流预混火焰对速度或当量比调制的脉冲响应的分析结果在统一框架中呈现。下一章讨论低阶参数模型，它利用控制火焰动力学的潜在对流过程的先验知识，但仍然需要来自实验或高保真模拟的输入来固定参数值。下一个，回顾了设计用于从模拟数据导出火焰动力学分布式时间延迟模型的各种方法。将湍流燃烧的大涡模拟与系统识别相结合的最新发展表明，即使对于具有技术意义的几何形状中的复杂涡流火焰，也可以估计在定量上准确的火焰动力学的降阶模型。最后一章回顾了声学非致密火焰的工作、利用分布式延迟的热声不稳定性被动控制策略，以及对流色散对时间延迟分布和熵波强度的影响。将湍流燃烧的大涡模拟与系统识别相结合，已经证明可以估计火焰动力学的降阶模型，即使对于技术感兴趣的几何形状中的复杂涡流火焰，该模型也是定量准确的。最后一章回顾了声学非致密火焰的工作、利用分布式延迟的热声不稳定性被动控制策略，以及对流色散对时间延迟分布和熵波强度的影响。将湍流燃烧的大涡模拟与系统识别相结合，已经证明可以估计火焰动力学的降阶模型，即使对于技术感兴趣的几何形状中的复杂涡流火焰，该模型也是定量准确的。最后一章回顾了声学非致密火焰的工作、利用分布式延迟的热声不稳定性被动控制策略，以及对流色散对时间延迟分布和熵波强度的影响。