高塔流固耦合振动特性分析及结构改进研究

发布时间：2018-10-30 16:35

【摘要】：高塔结构是工业生产中的重要设备,近年来高度与直径比很大的塔结构数量逐渐增多,高塔结构的重要载荷是风载荷,风载荷是一种典型的动力载荷,在风载荷与塔结构的流固耦合相互作用下,会使塔结构产生高频的振动和大幅度的变形,所以合理的塔结构对塔的抗风能力有着重要影响。本文以某火力发电厂塔设备为研究对象,针对高塔在强风中的振动问题,对塔设备提出了三种改进结构,采用数值模拟的方法,分析了塔结构周围的风流场,并对塔结构及其改进结构进行了流固耦合振动特性分析,主要研究内容如下:(1)根据某企业的工程应用,基于ANSYS Workbench中Design Modeler模块建立了原塔结构的有限元模型,在原塔结构的基础上提出了三种改进的塔结构,对比分析了原塔结构和改进结构的固有频率和振型,并分析了在静力学风载荷作用下原结构和改进结构的变形和应力。结果表明,改进结构前二阶固有频率和振型与原塔结构接近,并且数值随着加固高度的增加有先增大后减小的趋势,改进结构的后四阶固有频率较原塔结构的大,其数值随着加固高度的增加而增加;在静力学风载荷的作用下,改进结构很好的减小了原塔结构的变形,并且随着加固高度的增加塔的变形逐渐减小。(2)利用Fluent软件对不同重现期风速下的塔周围的流场进行了模拟,得出了塔的升力系数变化曲线,通过Matlab对升力系数曲线对其进行了频率分析,与不同高度处的漩涡的理论脱落频率进行了对比,并分析了塔周围的压力和速度场分布。结果表明,在5m左右高度处对应的升力系数振幅最大,随着高度的增加,漩涡脱落的频率变快,并且风速增大时,对应的升力系数振幅增大,频率增加;在塔的迎风面风压呈对称分布,在塔的背风侧,不同风速下和不同高度处的风压分布不同。(3)基于ANSYS Workbench中的SYTEM COUPLING模块对不同塔结构在不同重现期风速作用下进行了双向流固耦合模拟,对比分析了在不同重现期风速下原塔结构和改进结构的顺风向振动和横风向振动。结果表明,在双向流固耦合计算过程中,改进结构在整个时程内的每个时间步的最大位移和最大应力的振动平均值明显小于原塔结构,改进结构很好地改善了塔的整体振动情况;在不同风速下,改进结构与原塔结构顺风向的振动频率相同,改进结构顺风向的振动幅值要小于原塔结构;在不同风速下,改进结构的横风向振动频率并没有明显的规律高于原塔结构,但是在整体上,改进结构在不同风速下的横向风的振动幅值要小于原塔结构,工程应用中,可以根据当地的风环境选择不同加固高度的改进结构。
[Abstract]:Tower structure is an important equipment in industrial production. In recent years, the number of tower structures with large ratio of height to diameter has gradually increased. The important load of tower structure is wind load, and wind load is a typical dynamic load. Under the interaction of wind load and the fluid-solid coupling of tower structure, the tower structure will produce high frequency vibration and large deformation, so the reasonable tower structure has an important influence on the tower's wind resistance. In this paper, taking the tower equipment of a thermal power plant as the research object, aiming at the vibration problem of the tower in the strong wind, three kinds of improved structures are proposed for the tower equipment. The wind flow field around the tower structure is analyzed by numerical simulation. The characteristics of fluid-solid coupling vibration of tower structure and its improved structure are analyzed. The main contents are as follows: (1) according to the engineering application of a certain enterprise, the finite element model of the original tower structure is established based on the Design Modeler module in ANSYS Workbench. Based on the original tower structure, three improved tower structures are proposed. The natural frequencies and modes of the original tower structure and the improved tower structure are compared and analyzed. The deformation and stress of the original structure and the improved structure under static wind load are analyzed. The results show that the first second order natural frequency and mode shape of the improved structure are close to that of the original tower structure, and the value increases first and then decreases with the increase of the reinforcement height, and the second fourth order natural frequency of the improved structure is larger than that of the original tower structure. Its value increases with the increase of reinforcement height. Under the action of static wind load, the improved structure can reduce the deformation of the original tower structure. And with the increase of reinforcement height, the deformation of tower gradually decreases. (2) the flow field around the tower under different wind speed is simulated by using Fluent software, and the variation curve of tower lift coefficient is obtained. The frequency analysis of the lifting coefficient curve by Matlab is carried out, and the theoretical shedding frequency of vortex at different heights is compared, and the distribution of pressure and velocity field around the tower is analyzed. The results show that the amplitude of lift coefficient is the largest at the height of about 5m, and the frequency of vortex shedding becomes faster with the increase of height, and when the wind speed increases, the amplitude of the corresponding lift coefficient increases and the frequency increases. The wind pressure is symmetrically distributed on the upwind side of the tower, and on the leeward side of the tower, The distribution of wind pressure is different at different wind speeds and different heights. (3) based on the SYTEM COUPLING module in ANSYS Workbench, the two-way fluid-solid coupling simulation of different tower structures under different wind speeds during the recurrence period is carried out. The downwind vibration and crosswind vibration of the original tower structure and the improved structure under different reappearance periods are compared and analyzed. The results show that the average vibration value of the maximum displacement and maximum stress of each time step of the improved structure in the whole time history is obviously smaller than that of the original tower structure in the process of two-way fluid-solid coupling calculation. The improved structure can improve the whole vibration of the tower. Under different wind speed, the vibration frequency of the improved structure is the same as that of the original tower structure, and the amplitude of the improved structure is smaller than that of the original tower structure. Under different wind speed, the vibration frequency of crosswind direction of the improved structure is not obviously higher than that of the original tower structure, but on the whole, the amplitude of transverse wind vibration of the improved structure under different wind speeds is smaller than that of the original tower structure. The improved structures with different reinforcement heights can be selected according to the local wind environment.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ053.5

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