摘要
我国具有丰富的低水头水力资源,且大多分布在中东部对电能需求高的经济发达地区。随着我国高水头水力资源的大力开发利用,可供开发的高水头水力资源所剩不多,因此低水头水力资源的开发日益受到人们的重视。理论与实践证明,贯流式水轮机组是开发低水头水电站最为适合的机组。贯流式水电站厂房是河床式厂房的一种,本身既是发电建筑物,又是挡水建筑物,因此厂房结构的稳定性十分重要。结构与机组的耦联振动问题也一直是研究的重点,水力因素又是非常重要的振源,因此研究水流与结构的相互作用非常有必要。
本文以某贯流式水电站厂房结构为研究对象,利用三维有限元软件ANSYS建立了厂房结构模型,分析了水体对结构自振特性的影响,对结构在静力荷载和动力荷载作用下的受力情况进行了分析。主要研究内容如下:
(1)在水电站厂房结构自振特性的计算中,计算了结构的干模态和湿模态。在湿模态计算中,对流道充水、溢流面充水和两者均过水三种工况分别进行了计算。计算中,首先采用流固耦合的方法,根据流固耦合方法计算的数值和振型图,利用附加质量法不断试算,直到两种方法所得频率值相差不多且振型相同时为止,得到适用于贯流式水电站流道的附加质量公式。
(2)根据计算的厂房结构的自振特性,对引起水电站厂房结构振动的振源进行分析,得到影响厂房结构振动的主要振源。根据规范,对该厂房结构进行共振校核。
(3)对三种工况下的8个剖面进行静力计算,对各个部位的应力情况进行分析。考虑地震对水电站结构的影响,并对这三种工况下8个剖面进行地震响应谱分析,为反映实际情况,将谱分析结果和静力结果进行叠加,分析各个剖面的应力情况。
(4)对贯流式机组支撑结构进行谐响应分析。将基础荷载看作是简谐荷载,计算结构在一定频率范围和额定转频、飞逸转频下的位移响应,得到结构主要受力部位的频率-幅值曲线,并对受力情况做研究分析。
China has a lot of low-head hydropower resources , and most of them are in the eastern part of the high energy demand in economically developed areas. With the rapid exploitation of high-head hydropower resources in China, there are seldom high-head hydropower resources left to be developed, so people have pay an increasing attention on the development of low-head hydropower resources. Theory and practice have proved that tubular turbine is the most suitable units for the development of low-head hydropower. Bulb turbine hydropower station is one type of run-of-river power plants, and the building itself is not only power building but also retaining structures, therefore structural stability of the plant is very important. Structure and unit coupled vibration problem has been the focus of the study, besides, water is also very important factors in the local oscillator, so it is necessary to study the interaction of flow and structure.
Therefore, in this paper, the study is based on a bulb turbine hydropower station, uses ANSYS which is three-dimensional finite element software to build the model of the station, analysis the influence of water on structural vibration characteristics, and analysis the stress condition of the structure under static and dynamic loads. And the main studies are as follows:
(1) In the calculation of the vibration characteristics of the hydropower plant structure, the dry modal and wetting modal is calculated. In the wetting mode calculation, three conditions are calculated, flow channel water-filled, spillway over the water and both of them with water. According to the fluid-solid coupling method to calculate the values, and based on the results and shapes, using the mass added method to calculate the modal again and again, and do not stop the simulation until two methods income similar frequency value and the same vibration mode shape, and then get the mass added formula which is suitable for the bulb turbine hydropower station.
(2) According to the calculation of the vibration characteristics of plant structures, analysis the vibration sources which is lead to the vibration of the hydropower station, and then get the main vibration source. According to the standard, check the resonance of the hydropower station.
(3) This paper calculates the static of the structure with eight sections of three condition, and analysis the press condition of these sections. Considering the influence of earthquake to the hydropower station, calculates the spectrum of the three condition with eight sections. To reflect the actual situation, overlay the spectral analysis results and the results of static, and then analysis the stress of every section.
(4) Calculates the structural support harmonic of the tubular turbine. The foundation loads is regarded as the harmonic loads, and calculates the amplitude when the structure is under a certain frequency , specified frequency and fly to escape frequency, and get the frequency - amplitude curve of the main parts of the force structure, and then study on the stress conditions.
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