自然通风冷却塔整体稳定性模型实验及有限元分析研究

发布时间：2018-04-26 02:12

本文选题：自然通风冷却塔 + 整体稳定性　；参考：《浙江大学》2017年硕士论文

【摘要】：稳定性问题是自然通风冷却塔设计时必须考虑的主要因素。伴随着冷却塔塔高的不断增加,需对冷却塔结构设计规范中关于整体稳定性经验公式的适用性进行深入研究。鉴于复杂结构整体稳定性问题难以得到相应的解析解,故采用模型实验法及有限元计算方法相结合对冷却塔整体稳定性的基本规律进行研究,为冷却塔结构设计从整体稳定性角度提出合理的意见与建议。本文首先利用3D打印技术制作了三个不同壁厚的缩尺冷却塔模型,于风洞中通过逐步增加风速完成了稳定性实验,并对实验得到的失稳临界载荷进行规律分析。实验结果表明:模型失稳前变形很小且失稳突然发生,表明整体失稳模式为弹性屈曲,其壁厚与喉部半径之比是确定失稳临界载荷一个关键参数,根据模型实验得到的统计分析结果与现有规范要求非常接近。同时采用有限元软件ANSYS对实验模型分别进行线性稳定性、考虑初始缺陷稳定性及考虑非线性稳定性计算,与实验结果进行比较分析可知,计算得到的屈曲模态同模型实验屈曲形态保持一致,而由模型有限元线性稳定性分析得到的系数要大于风洞实验的结果及设计规范值,且冷却塔结构失稳时的临界载荷对初始缺陷非常敏感。对不同塔型的98座实际冷却塔进行了整体稳定性计算分析,讨论了不同塔高、不同喉部深度、不同底部斜率及不同顶部仰角等几何参数对冷却塔整体稳定性的影响。研究表明,所有塔型失稳时临界载荷根据统计分析得到的规律与现有设计规范的经验公式相一致,统计分析得到的系数约是经验公式系数的2倍。由于现有冷却塔设计规范中关于整体稳定性的经验公式已经考虑了初始缺陷等因素的影响,并在实际设计时采用了 5倍的安全因子,因此从整体稳定性角度来看,按现有设计规范所设计的冷却塔是安全的。
[Abstract]:Stability is the main factor that must be considered in the design of natural ventilation cooling tower. With the increasing of tower height, the applicability of empirical formula of overall stability in the structural design code of cooling tower needs to be deeply studied. In view of the difficulty of obtaining the corresponding analytical solution to the whole stability problem of complex structures, the basic law of the overall stability of cooling tower is studied by combining the model experiment method with the finite element method. Reasonable opinions and suggestions for the structural design of cooling tower from the point of view of overall stability are put forward. In this paper, three cooling tower models with different wall thickness are made by using 3D printing technology. The stability experiment is completed by increasing wind speed step by step in wind tunnel, and the critical load of instability obtained from the experiment is analyzed. The experimental results show that the deformation of the model before instability is very small and the instability occurs suddenly, which indicates that the overall instability mode is elastic buckling, and the ratio of wall thickness to throat radius is a key parameter to determine the critical load of instability. The statistical analysis results obtained from the model experiments are very close to the requirements of the existing specifications. At the same time, the finite element software ANSYS is used to calculate the linear stability of the experimental model, the initial defect stability and the nonlinear stability are considered, and the results are compared with the experimental results. The calculated buckling mode is consistent with the buckling shape of the model experiment, and the coefficient obtained from the linear stability analysis of the finite element method is larger than that of the wind tunnel experiment and the design specification. The critical load of cooling tower is sensitive to the initial defect. The overall stability of 98 actual cooling towers with different tower types is calculated and analyzed. The effects of different tower height, different throat depth, different bottom slope and different elevation angle on the overall stability of cooling tower are discussed. The results show that the critical loads obtained by statistical analysis are consistent with the empirical formulas of the existing design codes, and the coefficients obtained by statistical analysis are about twice the coefficients of the empirical formulas. Because the influence of initial defects and other factors have been taken into account in the empirical formula of overall stability in the existing design code of cooling tower, and the safety factor of 5 times is used in the actual design, therefore, from the point of view of overall stability, Cooling towers designed according to existing design specifications are safe.
【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】：TM62

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