Flow-Sound Interaction Mechanisms and Control Strategies

* * 流激声共振是许多工程应用中的一个设计问题，例如热交换器、锅炉厂、蒸汽机和管道系统中的管束。它发生在海崖体（如圆柱体）周围的流动以共振方式振动时。这通常导致产生严重的噪声问题和/或过度振动。由于声学共振现象尚未完全了解，它可能是危险的不可预测的，并可能导致灾难性的故障。随着对能源需求的不断增长，现有电厂的扩建项目正在成为普遍的做法。这意味着构造具有比目前使用的更高流速的更大的热交换器管束，这反过来将使热交换器更容易受到噪声和振动问题的影响。考虑到现有的知识水平的流声相互作用的换热器管束，它是非常复杂的预测发生声共振在设计阶段。* 由于管束中流声相互作用机理的复杂性，已对各种布置的孤立圆柱体的简化情况进行了详细研究。然而，这些知识不能直接应用于管束的情况。此外，翅片管被广泛应用于换热器管束中，以提高传热效率。在这方面，以前的实验表明，添加鳍柱可以增强的过程中的旋涡脱落，因此可以增加的敏感性声共振激发。然而，申请人的研究确定，在横流中的单个翅片圆柱体的情况下的声共振取决于其纵横比。虽然圆柱体的长宽比不是裸圆柱体声共振激发机制中的一个因素，但它是研究翅片管束声共振激发时应考虑的一个重要参数。*因此，本研究计划的主要目标是调查流声相互作用的基本机制，管束与裸柱和翅片的完整阵列，并开发实用的控制策略，以减轻声共振的发生。这项研究的结果将导致可靠的设计准则，可用于预测，控制和避免发生声共振的换热器管束的发展。这种重要的指导方针目前还没有在文献中。这不仅将减少由于热交换器管束的潜在灾难性故障而导致的发电厂的计划外停机，而且还将允许建造更大和更高效的热交换器。提高这些设备的效率、安全性和可靠性将直接有利于加拿大经济。

* * * *Flow-excited acoustic resonance is a design concern in many engineering applications such as tube bundles in heat exchangers, boiler plants, turbomachines, and piping systems. It occurs when the flow surrounding a bluff body, such as a circular cylinder, vibrates in a resonant manner. This often leads to the generation of acute noise problems and/or excessive vibrations. Since the acoustic resonance phenomenon is not yet fully understood, it can be dangerously unpredictable and may cause catastrophic failures. With the ever increasing demand on energy, expansion projects of existing power plants are becoming common practice. This means the construction of larger heat exchangers tube bundles with higher flow rates than what are currently used which, in turn, would make the heat exchangers more susceptible to noise and vibration problems. Considering the existing level of knowledge of flow-sound interaction in heat exchangers tube bundles it is extremely complex to predict the occurrence of acoustic resonance during the design stage. ***Due to the complexity of the flow-sound interaction mechanisms in tube bundles, the simplified cases of isolated cylinders in various arrangements have been investigated in some detail. However, this knowledge cannot be directly applied to the case of tube bundles. In addition, finned cylinders are widely used in heat exchangers tube bundles to increase the heat transfer rates. In this respect, previous experiments showed that adding fins to cylinders may enhance the process of vortex shedding, and therefore may increase the susceptibility to acoustic resonance excitation. However, the applicant's research established that the acoustic resonance for the case of a single finned cylinder in cross-flow depends on its aspect ratio. Although the cylinder's aspect ratio is not a factor in the excitation mechanism of acoustic resonance from bare cylinders, it is an important parameter that should be considered when investigating acoustic resonance excitation in finned tube bundles.***Therefore, the main objective of this research program is to investigate the fundamental mechanisms of flow-sound interaction in tube bundles with full arrays of both bare and finned cylinders, and develop practical control strategies to alleviate the occurrence of acoustic resonance. The findings of this research will lead to the development of reliable design guidelines that can be used to predict, control and avoid the occurrence of acoustic resonance in heat exchanger tube bundles. Such significant guidelines are currently not available in the literature. This will not only reduce unplanned shutdowns of power plants due to potential catastrophic failures of heat exchanger tube bundles but also will allow for the construction of larger and more efficient heat exchangers. Increasing the efficiency, safety and reliability of such equipment will directly benefit the Canadian economy.***