Vibrations of loosely supported tube bundles subjected to Streamwise Fluidelastic Forces

松散支撑管束在流向流体弹性力作用下的振动

• 批准号: RGPIN-2016-03800
• 负责人: Hassan, Marwan
• 金额: $ 2.11万
• 依托单位: University of Guelph
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=707987
• 关键词: Vibrations; loosely; supported; tube; bundles

Heat exchangers are important components in many industries, including power generation, petrochemical, and pulp and paper. These devices contain large numbers of tubes arranged in arrays. The purpose of these devices is to exchange heat between internal and external cooling and heating fluids. A great deal of energy is transported in the form of high pressure and heat. If a fraction of this energy is transformed into vibrations, a form of mechanical energy, the tube integrity will be compromised. Fluidelastic instability (FEI) is the most devastating excitation mechanism, characterized by a critical flow velocity beyond which a very large tube response occurs. These large vibrations will cause devastating failures, and need to be avoided. These failures manifest as fatigue, tube cracking, and fretting wear at the supports. Fretting wear occurs as the result of tubes impacting against their supports. In the past it was thought that FEI prevails only in the transverse (lift) direction. Design guidelines therefore focused on designing against instability in the transverse direction. All nuclear steam generators were made using these guidelines. Streamwise (drag) instability was never considered to be of importance in operating steam generators. This belief has been shattered after recent devastating failures in some replacement nuclear steam generators such as those at SONGS (San Onofre Nuclear Generation Station). These steam generators were designed to last for 40 years and instead, lasted for only 11 months. Investigating these failures has confirmed that streamwise (drag) instability was responsible for the damage caused by tube-to-tube fretting wear and failures. The magnitude of these failures sent shockwaves through the academic and the industrial community. In one plant, the price in terms of equipment damage and lost production costs was close to one billion dollars. In the wake of these incidents, both the research community and industry have made great efforts to understand this phenomenon. A few recent studies have confirmed beyond any doubt that streamwise FEI can occur. This mechanism is not fully understood, and there are no analytical or numerical tools available to predict it. There is therefore a pressing need to develop a model that can predict the stability threshold of this mechanism. The proposed research will develop a comprehensive time domain model that captures both transverse and streamwise FEI excitations. The developed model will then be used to study the effect of tube-to-support clearance, sliding support friction, and tube preload against the supports. This model will be used to study these effects through numerical simulations. These simulations will then be used to assess the structural integrity of in-service heat exchangers, and provide guidelines for the design of future heat exchanger units.

热交换器是许多行业的重要组成部分，包括发电，石化以及纸浆和纸张。 这些设备包含在阵列中排列的大量试管。 这些设备的目的是在内部和外部冷却和加热流体之间交换热量。以高压和热量的形式运输了大量能量。如果将此能量的一部分转化为振动，则一种机械能的形式，则管道完整性将受到损害。 流体弹性不稳定性（FEI）是最具破坏性的激发机制，其特征在于临界流速度之外发生了很大的管子响应。这些大型振动将导致破坏性的故障，需要避免。 这些故障表现为疲劳，管破裂和支撑处的插图磨损。 由于影响其支撑的导管，发生了插图磨损。 过去，人们认为FEI仅在横向（升降）方向上占上风。因此，设计指南的重点是在横向方向上设计反对不稳定性。 所有核蒸汽发生器都是使用这些准则进行的。在操作蒸汽发生器中，流动（阻力）不稳定性从未被认为是重要的。 在最近的一些替代核蒸汽发生器（如歌曲（San Onofre核代电站））中，最近发生了毁灭性的核蒸汽发生器，这种信念被打破了。这些蒸汽发生器的设计可持续40年，而仅持续了11个月。 调查这些故障已经证实，流动性（Drag）不稳定性是导致管子到管螺纹磨损和故障造成的损害。 这些失败的大小通过学术和工业界引发了冲击波。 在一种工厂中，设备损坏和生产成本损失的价格接近10亿美元。在发生这些事件之后，研究社区和行业都竭尽全力理解这一现象。 毫无疑问，最近的一些研究证实了可能发生流媒体FEI。 该机制尚未完全了解，也没有可预测的分析或数值工具。 因此，需要开发一个可以预测该机制稳定阈值的模型。 拟议的研究将开发一个综合的时域模型，该模型同时捕获横向和流向FEI激发。然后，开发的模型将用于研究管子到支撑物间隙，滑动支撑摩擦和针对支撑物预紧力的效果。 该模型将通过数值模拟来研究这些效果。 然后，这些模拟将用于评估服务中热交换器的结构完整性，并为未来的热交换器单元设计提供指南。