A STUDY ON FLUIDELASTIC VIBRATIONS OF TUBE ARRAYS SUBJECTED TO CROSSFROW IN HEAT EXCHANGERS

关于横掠换热管列的流体弹性振动问题，已有大量的文献发表，但几乎所有的文献都是通过实验获得计算临界流速所需的流体动力系数。本研究旨在利用作者发展的漏流理论，解析地求取水动力系数。主要结果如下：1.对三排管阵列沿流向的压力分布进行了测量，结果表明总压降发生在第一排。这一事实意味着第一排的作用就像冲动式涡轮机中的一排喷嘴。最小压力出现在最小间隙处，然后在最小间隙之后约5-10度处，流体与管壁分离。第二排管接收速度能，压力在最小间隙之前上升，在最小间隙之后再次下降。2.利用泄漏流理论计算了单排管中一根管沿列向振动时的流体力，并与Tanaka的实验结果进行了比较。稳定性分析表明，间隙处速度不稳定是由流体的负阻尼引起的，高间隙速度时出现涡动模态不稳定。后者是由速度平方流体刚度引起的，其中临界速度与质量阻尼参数的根成正比。4.在一定流量范围内，管阵管道内出现沿弦向的共振压力脉动，并伴有较高的声压级。

A vast number of papers have been published on the fluid-elastic vibrations of heat exchanger tube arrys subjected to crossflow, in almost all of which the hydrodymanic coefficients necessary to evaluate critical flow velocities are obtained experimentally. In this study it is aimed at obtaining the hydro-dynamic coefficients analytically by using the leakage-flow theory developed by the author. The results obtained are as follows.1.The measurements of pressure distribution in the streamwise direction in the three-row tube array show that the total pressure drop occurs at the first row. This fact means that the firsst row acts like a row of nozzles in impulse turbines. The minimum pressure occurs at the minimum gap and then the flow separates from the tube walls at about 5-10 degree after the minimum gap. The second row receives velocity energy and the pressure rises just before the minimum gap and then drops again after the minimum gap.2.Fluid forces acting on a tube in one-row tubes when it vibrates in the row direction are calculated by using the leakage-flow theory and compared with the experimental results obtained by Tanaka. Fairly well agreement is obtained, which confirms the validity of applying the leakage-flow theory for gap flow between tubes.3.Stability analysis shows that at gap velocity instability is caused by fluid negative damping, and that at high gap velocity whirling mode instability occurs. The latter is caused by velocity-squared fluid-stiffness, where the critical velocities are proportional to the root of mass damping parameters.4.Resonant pressure pulsations in the stremwise direction occur with high sound level in the duct containing tube array in a certain range of flow rate.