Analysis of S Characteristics and Pressure Pulsations in a Pump-Turbine With Misaligned Guide Vanes.
Analysis of S Characteristics and Pressure Pulsations in a Pump-Turbine With Misaligned Guide Vanes.
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DOI：
10.1115/1.4023647
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发表时间：
2013-05
期刊：
影响因子：
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通讯作者：
Hui Sun;R. Xiao;Weichao Liu;Fujun Wang
中科院分区：
文献类型：
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作者：
Hui Sun;R. Xiao;Weichao Liu;Fujun Wang
日益增长的环境问题以及对更好的功率平衡和频率控制的需求，使得人们对可再生能源的关注度不断提高，例如可逆式水泵水轮机，它既能发电又能储能。水泵水轮机沿S形曲线运行可能会导致在甩负荷过程中出现困难，水压异常升高，进而导致机器振动。压力波动是水泵水轮机运行不稳定的主要原因。错位导叶（MGVs）被广泛用于控制S区域的稳定性。已经对具有对齐导叶和错位导叶的比例模型进行了实验研究和计算流体动力学（CFD）模拟，并对S曲线特性以及在飞逸工况下频率和时频域的压力脉动进行了频谱分析。S特性曲线的走向与离心力以及低流量条件下的大入射角有关，在导叶和叶片进口之间形成大涡旋以及在无叶空间内强烈的回流是导致S形特性的主要因素。预先打开一些导叶可使水泵水轮机避免S特性的影响。然而，飞逸过程中流量的增加破坏了转轮内的流动对称性，导致转轮上出现不对称力，从而引起液压系统振荡。错位导叶技术还会增加尾水管中的压力波动，并对机组的稳定运行产生负面影响。
Growing environmental concerns and the need for better power balancing and frequency control have increased attention in renewable energy sources such as the reversible pump-turbine which can provide both power generation and energy storage. Pump-turbine operation along the S-shaped curve can lead to difficulties in loading the rejection process with unusual increases in water pressure, which lead to machine vibrations. Pressure fluctuations are the primary reason for unstable operation of pump-turbines. Misaligned guide vanes (MGVs) are widely used to control the stability in the S region. There have been experimental investigations and computational fluid dynamics (CFD) simulations of scale models with aligned guide vanes and MGVs with spectral analyses of the S curve characteristics and the pressure pulsations in the frequency and time-frequency domains at runaway conditions. The course of the S characteristic is related to the centrifugal force and the large incident angle at low flow conditions with large vortices forming between the guide vanes and the blade inlets and strong flow recirculation inside the vaneless space as the main factors that lead to the S-shaped characteristics. Preopening some of the guide vanes enables the pump-turbine to avoid the influence of the S characteristic. However, the increase of the flow during runaway destroys the flow symmetry in the runner leading to all asymmetry forces on the runner that leads to hydraulic system oscillations. The MGV technique also increases the pressure fluctuations in the draft tube and has a negative impact on stable operation of the unit.