One of the major concerns in the operability of power generation systems is their susceptibility to combustion instabilities. In this work, we explore whether a heat exchanger, an integral component of a domestic boiler, can be made to act as a passive controller that suppresses combustion instabilities. The combustor is modelled as a quarter-wave resonator (1-D, open at one end, closed at the other) with a compact heat source inside, which is modelled by a time-lag law. The heat exchanger is modelled as an array of tubes with bias flow and is placed near the closed end of the resonator, causing it to behave like a cavity-backed slit plate: an effective acoustic absorber. For simplicity and ease of analysis, we treat the physical processes of heat transfer and acoustic scattering occurring at the heat exchanger as two individual processes separated by an infinitesimal distance. The aeroacoustic response of the tube array is modelled using a quasi-steady approach and the heat transfer across the heat exchanger is modelled by assuming it to be a heat sink. Unsteady numerical simulations were carried out to obtain the heat exchanger transfer function, which is the response of the heat transfer at heat exchanger to upstream velocity perturbations. Combining the aeroacoustic response and the heat exchanger transfer function, in the limit of the distance between these processes tending to zero, gives the net influence of the heat exchanger. Other parameters of interest are the heat source location and the cavity length (the distance between the tube array and the closed end). We then construct stability maps for the first resonant mode of the aforementioned combustor configuration, for various parameter combinations. Our model predicts that stability can be achieved for a wide range of parameters.

中文翻译：

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带有热交换器的燃烧系统不稳定性的被动控制

发电系统可操作性的主要关注之一是其对燃烧不稳定性的敏感性。在这项工作中，我们探讨了热交换器（家用锅炉的组成部分）是否可以用作抑制燃烧不稳定性的被动控制器。燃烧室被建模为四分之一波长谐振器（1-D，一端打开，另一端关闭），内部具有紧凑的热源，并通过时滞定律进行建模。换热器被建模为带有偏置流的一系列管子，并放置在谐振器的封闭端附近，从而使其表现得像背腔的缝隙板：一种有效的吸声器。为了简化分析，我们将换热器中发生的传热和声散射的物理过程视为两个独立的过程，它们之间的距离为无穷小。使用准稳态方法对管阵列的空气声响应进行建模，并通过将其作为散热器来模拟跨热交换器的传热。进行了非稳态数值模拟以获得换热器传递函数，该函数是换热器处的传热对上游速度扰动的响应。在这些过程之间的距离趋于零的极限中，将空气声学响应和热交换器传递函数结合起来，就可以得出热交换器的净影响。感兴趣的其他参数是热源位置和腔体长度（管阵列和封闭端之间的距离）。然后，针对各种参数组合，我们为上述燃烧器配置的第一共振模式构造了稳定性图。我们的模型预测，可以针对各种参数实现稳定性。