【作者】 刘涛；

【导师】 杜小泽； 张宇宁；

【作者基本信息】 华北电力大学(北京) ， 热能工程， 2017， 硕士

【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。更多还原

【Abstract】 The reversible pump-turbine has two functions of pump and turbine at the same time and been in a wide range of applications in pumped storage power station.Because of the starting and stopping quickly and changing working conditions flexibly of the pump-turbine,the pumped storage power station can make rapid response and tracking the load change,and can play an efficient role in peak load shifting and ensuring the stability of the power system operation and so on.In recent years,with the emergence of the pump-turbine of large capacity and high head,a series of problems occur frequently such as start and stop accident of the unit,workshop vibration,noise,network difficulties,blade crack and so on.According to the literature research we can know that the pressure fluctuation is one of the main reasons these problems.Therefore,it is necessary to study the amplitude frequency characteristics and propagation mechanism of pressure fluctuation in the flow passage of the pump turbine unit,and provide a reliable reference for the hydraulic design and safe operation of the pump turbine.In order to study the vibration law of pump-turbine and workshop of a pumped storage power station in our country,we have carried out two times variable load experiments in the turbine working condition,with the average water head is 326.01 m and 316.23 m.During the experiments,four pressure pulse measurement points were arranged,one in the spiral case inlet,one in the top cover and two in the vaneless space.Subsequently,the pressure fluctuation signals were collected by the pressure sensor.This paper mainly analyzes the characteristics of pressure fluctuation,and the contents are as follows.Firstly,we analyzed the pressure signal in time domain of the first experiment,compared the difference of pressure fluctuation at different measuring points with the increasing of the load.The analysis results are as follows: The maximum relative amplitude of pressure fluctuation appears in the vaneless space,and along the channel extending to upstream the farther the distance,the smaller the amplitude;the relative amplitude of pressure fluctuation at each measuring point decreased firstly and then increased with the increasing of the load,and the minimum value appears when it reaches 80% of rated load where the flow is relatively good and the operation is relatively safe and stable.Secondly,we performed Fast Fourier Transform(FFT)on the pressure signal of first experiment,and analyzed its frequency domain characteristics.The analysis results are as follows: 9 times and 18 times of rotating frequency component of pressure fluctuation signals are in the dominant,which producing in vaneless space,and at the same time the two pressure pulsation frequency is the main cause for the unit and building vibration;with the improvement of the load,the two component above have different features,the pressure fluctuation with 9 times of the rotating frequency decreases constantly with the increasing of the load and the other pressure fluctuation decreases firstly decreases and then increases with the improvement of the load.Thirdly,we analyzed the amplitude and frequency characteristics of the pressure fluctuation signal of the second experiment and then compared them with the first data.Subsequently we discussed the relationship between the pressure fluctuation and the operating head of the pump-turbine.The analysis results are as follows: the relative amplitude of pressure fluctuation at the spiral case inlet and top cover is smaller under the operating conditions of higher water head,in which the internal flow is relatively good;the relative amplitude of fluctuation at vaneless space is smaller under the operating conditions of lower water head,in which the internal flow is relatively good;it is worth noting that The frequency of pressure fluctuation is not affected by the change of head.更多还原