灯泡贯流式水电站厂房流固耦合动力特性研究

发布时间：2018-09-19 10:26

【摘要】：灯泡贯流式水电站一般为河床式,是开发低水头水力资源最合适的方式,由于其水力效率高、有较大的单位流量和较高的单位转速、土建工程量少、投资小见效快等优点,在国内外实际工程中得到了广泛应用。灯泡贯流式水电站厂房多为挡水厂房,本身作为枢纽挡水建筑物的一部分,且机组流道尺寸巨大,水体与结构的相互作用对厂房结构特性影响很大。水电站在运行过程中,厂房结构在地震荷载及脉动压力等作用下的动力特性一直是厂房研究关注的重点。因此,本文选择对某实际灯泡贯流式水电站厂房结构进行研究,基于流固耦合分析水体对结构自振特性以及地震响应等的影响,并对结构在脉动压力作用下的动力响应进行了计算。论文主要研究内容包括:(1)建立考虑厂房结构—地基—水体在内的流固耦合三维有限元模型,研究水体对厂房结构自振特性的影响。结果表明水体使厂房结构各阶频率值降低,附加质量法考虑水体作用计算得到的频率值相比流固耦合法考虑水体作用计算得到的频率值略有减小,且各阶振型也有所变化;进行厂房结构共振校核时需考虑水体作用,附加质量法和流固耦合法得到的结果差异不大。(2)以流固耦合方式考虑水体计算得到了机组流道结构在地震过程中的动水压力分布,发现上游流道内动水压力大于下游尾水管的动水压力。对比厂房结构在不考虑水体、附加质量法考虑水体作用及流固耦合法模拟水体三种方案下的地震响应,发现水体对厂房结构大部分区域的动力响应影响以增大为主,总体上附加质量法产生的增幅要大于流固耦合法,此规律在位移和应力两个响应量中表现较明显,而在速度与加速度响应中不够明显;水体对结构速度与加速度响应影响更复杂,对厂房结构进行抗震分析时需合理考虑水体作用。(3)分析水轮机流道CFD计算得到的流道脉动压力分布规律,结合多个断面的各测点的脉动压力精确模拟整个流道脉动压力场,采用时程法研究厂房在设计水头不同机组出力工况下振动响应的差异性。研究表明:随着机组出力的减小,流道脉动压力增大,厂房的振动位移、振动速度及振动加速度等响应值也增大,但各响应值均小于厂房振动标准的建议值;转轮叶片频率是引起厂房振动的主要频率。(4)结合流道内脉动压力的分布,采用谐响应法对流道进行分区加载,对比最大出力工况下各响应量与时程法的差异。结果表明谐响应法计算得到的副厂房楼板各响应均方根值大于时程法得到的结果,导叶与转轮间区域及尾水管区域的脉动压力在引起副厂房楼板振动响应中占据了绝大部分作用。
[Abstract]:Bulb tubular hydropower station is generally river bed type, which is the most suitable way to develop low head hydraulic resources. Because of its high hydraulic efficiency, larger unit flow rate and higher unit rotational speed, small amount of civil engineering and quick investment, etc. It has been widely used in practical engineering at home and abroad. The power house of bulb tubular hydropower station is mostly a water-retaining powerhouse, which itself is a part of the water retaining structure of the hub, and the size of the runner of the unit is huge. The interaction between water and structure has a great influence on the structural characteristics of the powerhouse. During the operation of hydropower station, the dynamic characteristics of powerhouse structure under the action of seismic load and pulsating pressure have been the focus of attention. Therefore, this paper chooses to study the structure of a practical bulb tubular hydropower station powerhouse, based on fluid-solid coupling analysis of the impact of water on the natural vibration characteristics of the structure and seismic response, etc. The dynamic response of the structure under pulsating pressure is calculated. The main contents of this paper are as follows: (1) the fluid-solid coupling three-dimensional finite element model considering powerhouse structure, foundation and water body is established to study the influence of water body on the natural vibration characteristics of powerhouse structure. The results show that the frequency values of the powerhouse structure are reduced by water, and the frequencies calculated by the additional mass method considering the interaction of water body are slightly smaller than those calculated by the fluid-solid coupling method, and the vibration modes of each order are also changed. The effect of water body should be taken into account in the resonance checking of powerhouse structure, but there is no difference between the additional mass method and fluid-structure coupling method. (2) the hydrodynamic pressure distribution of unit runner structure during earthquake is obtained by considering the water body in fluid-solid coupling mode. It is found that the hydrodynamic pressure in the upstream channel is greater than that in the downstream draft pipe. Comparing the seismic response of the powerhouse structure under the three schemes without considering the water body, the additional mass method and the fluid-solid coupling method, it is found that the effect of water body on the dynamic response of most areas of the powerhouse structure is mainly increased. On the whole, the increase of the additional mass method is larger than that of the fluid-solid coupling method, which is obvious in the displacement and stress response, but not obvious in the velocity and acceleration response. The influence of water on structural velocity and acceleration response is more complex, so the water body action should be considered reasonably in seismic analysis of powerhouse structure. (3) the distribution law of fluctuating pressure of runner obtained by CFD calculation of hydraulic turbine runner is analyzed. The pulsating pressure field of the whole channel is accurately simulated by the pulsating pressure at various measuring points of several sections. The difference of vibration response of the powerhouse under different unit output conditions with different design head is studied by time-process method. The results show that with the decrease of generating force, the pulsating pressure of the runner increases, and the vibration displacement, velocity and acceleration of the powerhouse also increase, but each response value is less than the suggested value of the vibration standard of the powerhouse. The frequency of runner blade is the main frequency that causes the vibration of the powerhouse. (4) combined with the distribution of pulsating pressure in the channel, the harmonic response method is used to load the runner in different zones, and the difference between the response and the time-history method under the maximum output condition is compared. The results show that the root mean square (RMS) values of each response obtained by the harmonic response method are larger than those obtained by the time-history method. The pulsating pressure between the guide vane and the runner and the draft tube area plays an important role in the vibration response of the auxiliary workshop floor.
【学位授予单位】：武汉大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV731

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