流体诱发管束振动的流体弹性不稳定性研究

发布时间：2018-04-25 07:18

本文选题：换热器管束 + 振动　；参考：《浙江大学》2017年硕士论文

【摘要】：换热器的管束振动可引起管子的微量磨损和疲劳,维修和更换换热管耗费高昂。至于管子振动的机理,目前比较一致的观点有四种,即:旋涡脱落、湍流抖振、流体弹性不稳定性以及声共振,其中,流体弹性不稳定性是流体诱发管束振动的最危险的诱发因素,极易引起管子的大幅度振动导致其在支撑处被快速磨损。目前,已经存在许多关于流体弹性不稳定性的实验研究,但由于振动机理的复杂性,相关的设计准则在学术界并未给出统一的结论。因此,有关流体弹性不稳定性的研究还需要进一步的展开,为换热器的设计提供更多的理论依据。本文创新设计了可用于单相流和两相流诱发管束振动的实验测试平台。在实验的过程中,研究了和对比了正方形和正三角形排列、节径比为1.28和1.33的四种管束装置的流体弹性不稳定性,并测试了管束在单相流和两相流中的振动特性。同时,本文还采用计算流体力学(CFD)和流固耦合的方法,使用经实验验证的有限元模型对管束振动的流体弹性不稳定性进行了模拟研究,得到了流场和结构场中的信息,并进行分析,补充了实验研究的内容,对深入理解流体弹性不稳定性的机理提供帮助。结果发现:a)无论在单相流还是两相流中,在相同条件下,正方形排列的管束结构比正三角形排列的管束结构更稳定;b)在含气率低于80%的两相横向流中,对于节径比不小于1.28的正三角形和正方形排列管束,推荐正三角形排列管束的不稳定常数K为3.4,正方形排列管束的不稳定常数K为4.0;c)随着节点流速的增大,管束流体弹性不稳定性的主振方向从曳力方向向升力方向转化;d)管束排列方式中,发生流体弹性不稳定性的难易程度依次为:正方形最难,正三角形次之,转置正方形再次之,转置正三角形最容易;e)发现随着节径比的增大,发生流体弹性不稳定性的临界流速也逐渐增大。
[Abstract]:The vibration of tube bundle of heat exchanger can cause slight wear and fatigue of the tube, and it is expensive to repair and replace the heat exchanger tube. As for the mechanism of tube vibration, there are four kinds of views: vortex shedding, turbulent buffeting, fluid elastic instability and acoustic resonance. Fluid elastic instability is the most dangerous factor of fluid induced tube bundle vibration. It is easy to cause the tube vibration to cause rapid wear at the support. At present, there are many experimental studies on fluid elastic instability. However, due to the complexity of vibration mechanism, the relevant design criteria have not come to a unified conclusion in academic circles. Therefore, the study of fluid elastic instability needs to be further developed to provide more theoretical basis for the design of heat exchangers. In this paper, an experimental test platform for the vibration of tube bundle induced by single phase flow and two phase flow is designed. In the course of the experiment, the fluid elastic instability of four kinds of tube bundle devices with square and triangular arrangement, nodal diameter ratio of 1.28 and 1.33 are studied and the vibration characteristics of the tube bundle in single-phase flow and two-phase flow are tested. At the same time, the fluid elastic instability of the tube bundle vibration is simulated by using the finite element model verified by the experiment, and the information in the flow field and the structure field is obtained by using the method of computational fluid dynamics (CFD) and fluid-solid coupling. The analysis is carried out to supplement the content of the experimental study and to provide help for further understanding of the mechanism of fluid elastic instability. The results show that in both single-phase and two-phase flows, the square bundle structure is more stable than the triangular bundle bundle structure under the same conditions) in the two-phase transverse flow, where the gas content is less than 80%. For the square and triangular bundle with nodal diameter ratio of not less than 1.28, it is recommended that the unstable constant K of the triangular bundle is 3.4, and the instability constant K of the square bundle is 4.0 C) with the increase of the flow velocity of the node. The main vibration direction of the fluid elastic instability of the tube bundle is changed from the direction of drag to the direction of lift. In the arrangement of the tube bundle, the order of difficulty of the fluid elastic instability is as follows: the square is the most difficult, the triangle is the second, and the square is transposed again. It is found that the critical velocity of fluid elastic instability increases with the increase of nodal diameter ratio.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ051.5

【参考文献】