Experimental investigation of a pump-turbine at off-design operating conditions
Experimental investigation of a pump-turbine at off-design operating conditions
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发表时间：
2009
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通讯作者：
V. Hasmatuchi;M. Farhat;P. Maruzewski;F. Avellan
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作者：
V. Hasmatuchi;M. Farhat;P. Maruzewski;F. Avellan
抽水蓄能电站是开发新的可再生无二氧化碳一次能源和提高电力供应安全的关键组成部分。它们还在当今自由化的电力市场中提供了有趣的商业机会。然而，在泵送和发电模式之间的快速和频繁切换以及在非设计条件下的扩展操作提出了与大的非稳定水动力相关的技术挑战。在本研究中，低比转速径流泵-涡轮机的缩比模型的研究，以确定流动不稳定性的开始和发展。重点研究了飞逸和S形的非设计工况下的发电模式。定子壁压测量是在30个微型压阻传感器的帮助下进行的。当从最佳效率点出发，提高转轮速度时，压力脉动的显著增加主要发生在导叶之间的通道中。频谱分析表明，在失控时，低频分量（约为转轮旋转频率的70%）上升，当接近零排放条件时，低频分量进一步增加。相位分析表明，几个不稳定源，至少有三个，旋转与转轮在亚同步速度。虽然无法描述旋转单元的性质，但认为回流可能在转轮和分配器之间的差距中发展，并在转轮通道的发电和泵送模式之间交替切换。然而，旋转流动分离也可能在转轮通道中发展，导致其堵塞。
Pumped storage power plants are key components for the development of new renewable CO2-free primary energies and the security enhancement of electricity supply. They also offer interesting business opportunities in nowadays liberalized electricity market. However, the fast and frequent switching between pumping and generating modes as well as extended operations at off- design conditions poses technical challenges related to large unsteady hydrodynamic forces. In the present study, a reduced scale model of a low specific speed radial pump- turbine is investigated to identify the onset and development of flow instabilities. The focus is put on the generating mode at off-design conditions involving runaway and “S-shape”. Wall pressure measurements in the stator are performed with the help of 30 miniature piezoresistive sensors. When starting from the best efficiency point and increasing the runner speed, a significant increase of the pressure fluctuation is observed mainly in the channels between wicket gates. The spectral analysis shows a rise of a low frequency component (about 70% of the runner rotational frequency) at runaway, which further increases as the zero discharge condition is approached. Phase analysis reveals that several instability sources, at least three, rotate with runner at sub synchronous speed. Although the nature of the rotating cells could not be described, it is thought that back flow may develop in the gap between runner and distributor with an alternate switch between generating and pumping modes of runner channels. Nevertheless, rotating flow separation may also develop in the runner channels leading to their blockage.