Understanding the role of flow dynamics in thermoacoustic combustion instability
Understanding the role of flow dynamics in thermoacoustic combustion instability
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DOI：
10.1016/j.proci.2022.07.115
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发表时间：
2022-10
影响因子：
3.4
通讯作者：
J. O’Connor
中科院分区：
文献类型：
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作者：
J. O’Connor
热声燃烧不稳定性是一些高性能、低排放燃烧技术中最具挑战性的操作问题之一，包括燃气轮机、航空发动机、火箭和工业锅炉。在燃烧室声学和火焰热释放率波动之间耦合的驱动下，热声燃烧不稳定会导致可操作性降低、排放增加，在最极端的情况下，还会导致燃烧室部件的灾难性故障。声学和燃烧之间的反馈回路通常由流体力学振荡促进，称为“速度耦合”，即声学振荡驱动流动波动，流动波动反过来又产生火焰波动。这些流体力学振荡的特征高度依赖于流场的结构和流动对外部激励的接受性。燃烧室流场利用流体再循环和剪切等特征来增强火焰保持和减少排放，但这些特征也会使流动容易受到声波激励，甚至驱动自激振荡。在本文中，我们讨论了热声不稳定性的基础，重点讨论了水动力振荡在典型燃烧室流动中的作用。为了便于讨论，我们探讨了几个关键燃烧室单元流动（尾迹，旋转射流等）的水动力不稳定性特征，并说明了流动的水动力稳定性如何成为确定燃烧室热声振荡倾向的重要考虑因素。本文讨论了流体力学和热声学之间耦合的几个例子来说明这一重要环节。本文最后讨论了设计抗热声不稳定流场的潜力，要么通过降低流动的接受度，要么通过非线性耦合机制，自激流动不稳定性可以抑制速度耦合燃烧振荡。
Thermoacoustic combustion instability is one of the most challenging operational issues in several high-performance, low-emissions combustion technologies, including gas turbines, aircraft engines, rockets, and industrial boilers. Driven by the coupling between combustor acoustics and flame heat release rate fluctuations, thermoacoustic combustion instability can lead to reduced operability, increased emissions, and, in the most extreme cases, catastrophic failure of combustor components. The feedback loop between acoustics and combustion is often facilitated by fluid mechanic oscillations, referred to as “velocity coupling,” whereby acoustic oscillations drive flow fluctuations, which in turn create fluctuations in the flame. The character of these fluid mechanic oscillations is highly dependent on the structure of the flow field and the receptivity of the flow to external excitation. Combustor flow fields use features like fluid recirculation and shear to enhance flame holding and reduce emissions, but these are also the same features that can make the flow receptive to acoustic excitation or even drive self-excited oscillations. In this paper, we discuss the basics of thermoacoustic instability with a focus on the role of hydrodynamic oscillations in typical combustor flows. To facilitate this discussion, we explore the hydrodynamic instability characteristics of several key combustor unit flows (wakes, swirling jets, etc.) and show how the hydrodynamic stability of a flow is an important consideration in determining a combustor’s propensity for thermoacoustic oscillations. Several examples of coupling between hydrodynamics and thermoacoustics are discussed to illustrate this important link. The paper concludes by discussing the potential for designing flow fields that are thermoacoustic instability resistant, either through a reduction in the receptivity of the flow or through nonlinear coupling mechanisms by which self-excited flow instabilities can suppress velocity-coupled combustion oscillations.