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: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=653179
• 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部件，包括发电、石化和制浆造纸。这些装置包含大量排列成阵列的管子。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。大量的能量是以高压和热的形式传输的。如果这种能量的一小部分被转化为振动，这是一种机械能，管道的完整性将受到影响。*流体弹性不稳定(FEI)是最具破坏性的激励机制，其特征是存在一个临界流速，超过这个临界流速就会产生非常大的管子响应。这些巨大的振动将导致毁灭性的故障，需要避免。这些故障表现为疲劳、管子破裂和支承处的微动磨损。微动磨损是管子撞击其支承的结果。*过去，人们认为FEI只在横向(升力)方向占优势。因此，设计指南侧重于抗横向不稳定的设计。所有的核蒸汽发生器都是按照这些准则制造的。流向(阻力)不稳定性从来不被认为是运行蒸汽发生器的重要因素。在最近一些替换的核蒸汽发生器发生毁灭性故障后，这种信念已经破灭，例如圣奥诺弗雷核电站的那些。这些蒸汽发生器的设计寿命为40年，但实际上只持续了11个月。对这些故障的调查证实，管子间的微动磨损和故障造成的损坏是流向(阻力)不稳定性造成的。这些失败的规模在学术界和工业界引起了冲击波。在一家工厂，设备损坏和生产成本损失的价格接近10亿美元。在这些事件发生后，研究界和工业界都做出了很大努力来理解这一现象。*最近的一些研究毫无疑问地证实了流线型FEI可以发生。这一机制尚不完全清楚，也没有可用的分析或数值工具来预测它。因此，迫切需要开发一种模型来预测这一机制的稳定阈值。*所提议的研究将开发一种能够同时捕获横向和流向FEI激励的全面的时间域模型。建立的模型将被用来研究管子与支座之间的间隙、滑动支座摩擦和管子预紧力对支座的影响。该模型将用于通过数值模拟来研究这些影响。这些模拟将被用来评估在役热交换器的结构完整性，并为未来热交换器的设计提供指导。**