原型可逆式水泵水轮机在水轮机工况下压力脉动特性的试验研究及分析

发布时间：2018-08-30 10:13

【摘要】：可逆式水泵水轮机集合了水泵与水轮机两种功能,并广泛应用于抽水蓄能电站。由于水泵水轮机启停迅速和工况变换灵活等优点使得抽水蓄能电站能快速反应与追踪电网负荷变化,并对其进行高效率的削峰填谷,进而维持电力系统稳定运行。近些年随着大容量、高水头水泵水轮机的出现,机组启停事故、厂房振动、并网困难、噪声、叶片纹裂等一系列问题频发。根据文献调研发现在诸多问题起因中,压力脉动是主要原因之一。因此有必要对可逆式机组过流通道内的压力脉动的传播机制和幅频特性进行深入的分析研究,为水泵水轮机的安全运行和水力设计提供可靠参考。为了研究国内某抽水蓄能电站水泵水轮机组的水力特性和厂房的振动规律,对该电站原型机组在水轮机工况下进行了两次变负荷试验。其中,第一次试验平均毛水头为326.01m,第二次试验平均毛水头为316.23m。试验过程中在过流通道内的蜗壳进口(1个)、顶盖(2个)和无叶区(2个)三个位置安置了四个压力脉动测点,并用压力传感器搜集了机组运行过程中产生的压力脉动信号。本文以压力脉动信号分析为主,内容如下。首先,对第一次试验中的压力信号进行时域分析,着重对比了不同测点位置压力脉动的强弱及其随负荷的变化情况。分析结果如下:无叶区测点处的压力脉动幅值最大,压力信号沿着流道向上游传播,并且延伸距离越远,幅值越小;随着机组负荷的提升,各个测点的压力脉动幅值呈现先减小后增大的趋势,且无量纲负荷为0.8时达到最小值,此时流态相对最好,运行最为安全稳定。第二,对第一次试验中的压力信号利用进行FFT变换,并分析压力脉动的频域特性。分析结果如下:压力脉动信号中9倍叶轮转频和18倍叶轮转频成分占主导,且均产生于无叶区,同时这两个特征频率下的压力脉动是造成厂房振动的主要原因;随着负荷的提升,以上两中成分的压力脉动呈现出不同的变化规律,9倍叶轮转频下的压力脉动幅值随着负荷的提升逐渐减小,而18倍叶轮转频下的压力脉动幅值随着负荷的提升先减小后增大。第三,对第二次试验中的压力脉动信号进行如上幅频特性分析,并与第一次试验数据进行对比,探讨压力脉动与机组运行水头的关系。分析结果如下:在高水头工况下,蜗壳进口和顶盖区域的压力脉动幅值相对较小,内部流动相对较稳定;在低水头工况下,无叶区2个测点处的压力脉动幅值相对较小,内部流动相对较稳定;值得注意的是,压力信号的频率不会因为水头的变动而产生变化。
[Abstract]:Reversible pump turbine has two functions: pump and turbine, and it is widely used in pumped storage power station. Due to the advantages of quick start and stop of pump turbine and flexible change of working conditions, pumped storage power station can quickly respond and track the change of power network load, and carry out high efficiency peak cutting and valley filling so as to maintain the stable operation of power system. In recent years, with the emergence of large capacity, high head water pump turbine, unit start and stop accident, plant vibration, grid-connection difficulty, noise, blade crack and a series of problems occurred frequently. According to literature investigation, it is found that pressure fluctuation is one of the main causes of many problems. Therefore it is necessary to analyze the propagation mechanism and amplitude-frequency characteristics of pressure pulsation in the flow passage of reversible generating units in order to provide reliable reference for the safe operation and hydraulic design of pump turbines. In order to study the hydraulic characteristics of the pump turbine unit and the vibration law of the workshop in a domestic pumped storage power station, two variable load tests were carried out on the prototype unit of the power station under the working conditions of the turbine. The average water head of the first experiment was 326.01 m, and that of the second experiment was 316.23 m. During the test, four pressure pulsation measuring points were placed at the inlet of the volute (1), the top (2) and the leafless zone (2) in the flow passage, and the pressure pulsation signals produced during the operation of the unit were collected by the pressure sensor. In this paper, the pressure pulsation signal analysis is the main, the content is as follows. Firstly, the pressure signal in the first test is analyzed in time domain, and the pressure fluctuation at different measuring points and its variation with load are compared. The results are as follows: the amplitude of pressure pulsation is the largest at the measuring point in the leafless area, and the pressure signal propagates upstream along the channel, and the farther the distance is, the smaller the amplitude is; with the increase of the unit load, The pressure fluctuation amplitude of each measuring point decreases first and then increases, and reaches the minimum value when the dimensionless load is 0.8, the flow state is relatively best and the operation is the most safe and stable. Secondly, the pressure signal in the first test is transformed by FFT, and the frequency characteristic of pressure fluctuation is analyzed. The results are as follows: in the pressure pulsation signal, 9 times impeller rotation frequency and 18 times impeller rotation frequency component are dominant, and both of them are produced in the leafless region, and the pressure pulsation at these two characteristic frequencies is the main cause of the powerhouse vibration. With the increase of load, the pressure pulsation of the above two components presents different variation laws, and the amplitude of pressure pulsation decreases gradually with the increase of load, and the amplitude of pressure pulsation decreases with the increase of load. However, the amplitude of pressure pulsation decreases first and then increases with the increase of load at the rotating frequency of 18 times impeller. Thirdly, the pressure pulsation signal in the second test is analyzed such as amplitude and frequency characteristic, and compared with the data of the first test, the relationship between the pressure pulsation and the running water head of the unit is discussed. The results are as follows: under the condition of high water head, the amplitude of pressure pulsation is relatively small and the internal flow is relatively stable at the inlet of volute and the top cover, and the amplitude of pressure pulsation is relatively small at the two measuring points in the leafless zone under the condition of low head. The internal flow is relatively stable; it is worth noting that the frequency of pressure signals does not change with the change of water head.
【学位授予单位】：华北电力大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV734.1

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