弹性管束动态特性子结构模态综合法

DYNAMIC CHARACTERISTICS OF ELASTIC TUBE BUNDLES WITH COMPONENT MODE SYNTHESIS METHOD

弹性管束换热器利用流体诱导振动强化传热,识别换热元件的模态特性对于了解其运行机理、优化结构设计有重要意义。基于此,运用子结构模态综合法,先推导出弹性管束每个部件的运动方程,然后根据相容性条件进行装配,从而得出弹性管束在模态坐标下的自由振动微分方程。用数值方法求解该方程,得出结构的固有频率和振型,并对模态频率和振型变化进行详细分析。结果表明:弹性管束既有面内振动又有面外振动。在管束内外复杂流场的宽频激励下,弹性管束的振动是各阶振型合成的复杂运动,从而初步解释了其强化传热的机理。

Heat transfer enhancement is achieved by fluid-induced vibration in elastic tube bundles heat exchangers. To understand the vibration mechanism and improve further the performance of elastic tube bundles, it is important to identify its modal property. Equations of motion of each component are derived firstly, and then the components of the system are assembled together according to the compatibility condition of displacements. Thus, the differential equation of free vibration in terms of principal modal coordinates for elastic tube bundles is obtained. The natural fi＇equencies and mode shapes are got by solving the equation of motion with numerical methods. The characteristics of mode shapes are analyzed. The results show that the in-plane vibration co-exists with the out-plane one. The vibration of elastic tube bundles is the combination of vibrations in different directions as a result of complex excitation in actual internal and external fluid field. The mechanism of heat transfer enhancement for elastic tube bundles is investigated elementarily.