换热器内弹性管束流体组合诱导振动响应的数值分析

Numerical Analysis on the Combined Flow Induced Vibration Response of Elastic Tube Bundle in Heat Exchanger

为了探讨换热器内弹性管束在流体诱导下的振动特性,采用流固耦合的弱耦合法,研究了弹性管束在不同流速的壳程和管程两场流体组合诱导下的振动响应,并对比分析了壳程流体和管程流体对弹性管束振动响应的影响。研究表明:当壳程和管程流速一定时,弹性管束两监测点各方向的振动主频、谐频大小一致,且振动主要体现为面内振动。壳程流速较低时,监测点沿壳程流速方向的位移曲线存在明显的二倍谐频。壳程流速变化对管束振动响应的影响较大,管程流速变化对管束振动响应的影响较小,说明弹性管束的振动主要由壳程流体引起。由于流体的冲击和管束重力的影响,当壳程流速较低时,管束沿壳程流速方向的振动平衡位置较低,随着流速的增加,管束沿壳程流速方向的振动平衡位置逐渐上移。

The vibration characteristics of the elastic tube bundle in heat exchanger, under the combined induction of shell-side and tube-side cross flows at different inlet water velocities are studied using weak coupling method of fluid-structure interaction. And the influences of shell- side and tube-side cross flows on the vibration responses of the elastic tube bundle are also analyzed comparatively. Numerical results show that the flow-induced dominant and harmonic frequency vibration frequencies, at the two monitor points of the elastic tube bundle and under the same water velocity, are uniform in all directions; and the flow-induced vibration is mainly an in-plane vibration. There is an obvious second harmonic frequency in the shell-side water flow direction at the two monitor points when the water velocity is relatively low. Compared with the change of the shell-side water velocity, the variation of the tube-side inlet flow velocity has less effect on the vibration response. It shows that the vibration is mainly induced by the shell-side cross flow. Furthermore, the vibration balance position of the elastic tube bundle in shell-side water flow direction is also low when the velocity is low, due to the influences of the gravity oftube bundle and the impact force of fluid; and the vibration balance position gradually moves up with the increase of the shell-side water velocity.