高水头混流式水泵水轮机无叶区压力特征分析

发布时间：2018-03-14 07:03

本文选题：水泵水轮机　切入点：数值模拟　出处：《哈尔滨工业大学》2014年硕士论文　论文类型：学位论文

【摘要】：近年来为满足用电需求新建了一批大型火电、核电机组。大容量机组的投产使用对电网的稳定性以及快速响应特性提出了更高的要求，必须建立与之配套的调节系统，抽水蓄能电站凭借其良好的调频调峰能力成为电网调节的首选，水泵水轮机的稳定性问题也因此成为关注的焦点。在诸多影响稳定运行的因素中，无叶区强烈的动静干涉及复杂的压力脉动是导致运行不稳定的主要原因之一，严重时会引发机组振动、噪声甚至叶片裂纹，因此有必要对无叶区压力特性及脉动机理进行深入的研究，为水泵水轮机的设计及稳定运行提供参考。为研究无叶区的压力特性，本文采用CFD技术对国内某抽水蓄能电站水轮机工况下模型和真机同一单位转速，不同导叶开度以及模型导叶摆动过程进行了数值模拟，对无叶区压力脉动进行了详细的分析，本文主要内容如下：（1）根据真机实际运行工况点，选取模型6个不同开度进行数值计算，获得了外特性及压力脉动幅值随开度变化的曲线，并与试验数据进行了对比。随后给出了无叶区压力脉动频率的理论预测并通过数值模拟进行验证，详细分析了最优工况无叶区压力脉动特性及上下游传播规律，并对模型无叶区压力脉动随导叶开度变化的规律进行了简要分析。（2）选取真机50%负荷，最优开度以及满负荷等3个工况进行数值计算，分别与模型对应的相似工况进行了详细的对比分析，研究模型与真机无叶区压力脉动频率成分及幅值大小的异同，探究模型与真机之间的换算关系。（3）对模型采用动网格方法计算，以18°作为起始开度，模拟导叶左右摆动1°过程中无叶区压力脉动特性，，对导叶不同转动状态下无叶区压力脉动幅值大小，时域以及频域特性进行了研究，最后对比分析了导叶整个摆动过程与导叶定开度过程无叶区压力脉动的异同。研究结果表明，无叶区压力脉动主要频率是转轮叶片通过频率及其谐波频率，此外还存在来自于转轮和尾水管的频率成分。无叶区压力脉动更容易向上游传播，但不同频率分量幅值衰减不一。不同导叶开度对无叶区压力脉动特性有显著影响。相似工况下真机与模型频率成分基本一致，但幅值大小差异较大且没有明显的换算关系。导叶摆动过程无叶区9倍频以下频率成分丰富，相对定开度峰峰值明显增大。
[Abstract]:In recent years, in order to meet the demand for electricity, a new batch of large thermal power and nuclear power units and large capacity units have been built up and put forward higher requirements for the stability of the power network and the characteristics of rapid response. It is necessary to establish a matching regulation system. Pumped-storage power station has become the first choice of power network regulation by virtue of its good capacity of frequency modulation and peak-shaving, and the stability of pump turbine has become the focus of attention. Among the factors that affect the stable operation of pumped-storage power station, One of the main causes of unstable operation is the strong dynamic and static interference and complex pressure fluctuation in the leafless area, which can lead to vibration, noise and even blade cracks in severe cases. Therefore, it is necessary to deeply study the pressure characteristics and pulsation mechanism in the leafless region to provide a reference for the design and stable operation of the pump turbine. In order to study the pressure characteristics in the vaneless region, a numerical simulation was carried out by using CFD technique to simulate the model and the actual unit rotating speed, the different guide vane opening degree and the model guide vane swing process under the same unit speed and the same unit speed of the turbine in a domestic pumped storage power station. The pressure fluctuation in the leafless region is analyzed in detail. The main contents of this paper are as follows:. 1) according to the actual operating conditions of the real machine, six different openings of the model are selected for numerical calculation, and the curves of the external characteristics and the amplitude of pressure pulsation with the opening degree are obtained. The theoretical prediction of pressure pulsation frequency in vaneless region is given and verified by numerical simulation. The characteristics of pressure fluctuation and the propagation law of upstream and downstream in the optimal condition are analyzed in detail. The variation of pressure pulsation with the opening of the guide vane is analyzed briefly. 2) selecting the 50% load, optimal opening and full load of the real machine to carry out numerical calculation, and comparing and analyzing in detail with the similar working conditions corresponding to the model. The differences and similarities of pressure pulsation frequency components and amplitudes between the model and the real machine are studied, and the conversion relationship between the model and the real machine is discussed. The dynamic grid method is used to calculate the model. With 18 掳as the initial opening, the characteristics of the pressure pulsation in the vaneless region during the 1 掳swing of the guide vane are simulated, and the amplitude of the pressure pulsation in the vaneless region under different rotating conditions of the guide vane is studied. The characteristics in time domain and frequency domain are studied. Finally, the differences and similarities of the pressure pulsation in the vaneless region between the whole swing process of the guide vane and the opening process of the guide vane are compared and analyzed. The results show that the main frequency of pressure pulsation in the leafless region is the frequency and harmonic frequency of the runner blade, in addition, there are frequency components from the runner and the draft tube, and the pressure pulsation in the leafless zone is more easily propagated upstream. However, the amplitude attenuation of different frequency components is different. The pressure pulsation characteristics in the vaneless region are significantly affected by the different guide vane openings. The frequency components of the real machine and the model are basically the same under similar operating conditions. However, the amplitude varies greatly and there is no obvious conversion relationship. The frequency components below 9 times frequency in the leafless region of the guide vane swing process are rich, and the peak value of the relative opening degree increases obviously.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TK730

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