不等频率比转置三角形管束流体弹性失稳试验研究

Experimental study on fluid-elastic instability of rotated triangular tube bundles with unequal frequency ratio

管壳式换热器是最为常用的热交换设备,管束的流致振动问题是设计和制造关注的重点,虽然换热器的设计过程对管束流致振动问题有所要求,但是由于管束的支撑存在不对称性,造成实际工作中的管束振动问题难以准确预测。采用水洞试验,研究了节径比为1.41的不同频率比转置三角形管束的流体弹性失稳特征,对比分析了振幅、频率响应和相图特性。结果表明,当Rf<0.8时,单弹性管模型很难准确预测管束横流向失稳临界流速。随着频率比Rf的减小,横流向失稳前振动形式由混沌形式向双周期振动转化,而顺流向振动形式在失稳后,则由准周期振动向双周期振动形式转化。同时,管束顺流向可能出现超过标准的振幅,在换热器设计和运行过程中应予以关注。

The shell and tube heat exchangers are the most commonly used heat exchange equipment,and the flow induced vibration of the tube bundle is one of the important issues puzzling the design and manufacture of the heat exchanger.Although the flow induced vibration of the tube bundle has been considered during the design process of the heat exchanger,the actual work of the tube bundle vibration problem is difficult to predict due to the asymmetry of the tube bundle support.The fluid-elastic instability of rotated triangular tube bundles with different frequency ratio and pitch diameter ratio of 1.41 was studied by water tunnel experiments.The results show that when R f<0.8,it is difficult for the single tube model to accurately predict the critical velocity of cross-flow instability of the tube bundle.With the decrease of the frequency ratio R f,the vibration form before cross-flow instability is converted from chaotic form to biperiodic vibration,while the in-flow vibration form is converted from quasi-periodic vibration to biperiodic vibration after instability.At the same time,the amplitude of the tube bundle along the flow direction may exceed the requirement of standard,which should be paid attention to during the design and operation of the heat exchanger.