Comprehensive experimental and numerical analysis of instability phenomena in pump turbines
Comprehensive experimental and numerical analysis of instability phenomena in pump turbines
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DOI：
10.1088/1755-1315/22/3/032046
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发表时间：
2014-03
期刊：
影响因子：
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通讯作者：
C. Gentner;M. Sallaberger;C. Widmer;B. J. Bobach;H. Jaberg;Jürgen Schiffer;Florian Senn;M. Guggenberger
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文献类型：
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作者：
C. Gentner;M. Sallaberger;C. Widmer;B. J. Bobach;H. Jaberg;Jürgen Schiffer;Florian Senn;M. Guggenberger
电力市场的变化导致水泵水轮机运行要求的变化。公用事业需要在泵送和发电模式之间快速频繁地切换，并且越来越希望在非设计条件下长时间运行。在机器特性的不稳定区域操作装置是不可接受的，可能导致液压系统的自激振动。在水泵水轮机的涡轮机运行中，在接近失控条件的低负荷非设计运行时可能出现不稳定行为（涡轮机特性曲线的S形）。这种类型的不稳定性可能会妨碍机器在涡轮机模式下的同步，从而增加启动和切换时间。在甩负荷的情况下，明显的S形不稳定性也会导致放电显著下降。吸力侧和尾水洞内的低压可能导致水柱危险分离。了解导致水泵水轮机不稳定行为的流动特征是设计能够满足与操作灵活性相关的日益增长的要求的机器的先决条件。由于这些不稳定区的复杂和高度不稳定的流动模式，流动模拟是苛刻的。只有非定常模拟方法才能再现这些操作区域中的控制物理效应。安德里茨水电公司与多所大学合作，通过模拟和测量，对水泵水轮机在涡轮机运行中的稳定性进行了研究。为了验证不稳定工作点的流动模拟结果，格拉兹科技大学（奥地利）进行了详细的实验研究。在长期的研究工作中，利用二维激光粒子图像测速技术（PIV）对几种水泵涡轮机转轮的运行特性进行了测量，并对水泵涡轮机在空载和飞逸状态下的流态进行了研究。在不同导叶位置下，对转轮进口无导叶空间的流场进行了实验观测，并与非定常CFD模拟结果进行了比较。物理现象可视化和洞察流动现象。利用模拟和测量结果的分析，可以得出一个一致的解释流体力学机制导致水泵水轮机的S形不稳定。
The changes in the electricity market have led to changed requirements for the operation of pump turbines. Utilities need to change fast and frequently between pumping and generating modes and increasingly want to operate at off-design conditions for extended periods. Operation of the units in instable areas of the machine characteristic is not acceptable and may lead to self-excited vibration of the hydraulic system. In turbine operation of pump turbines unstable behaviour can occur at low load off-design operation close to runaway conditions (S-shape of the turbine characteristic). This type of instability may impede the synchronization of the machine in turbine mode and thus increase start-up and switch over times. A pronounced S-shaped instability can also lead to significant drop of discharge in the event of load rejection. Low pressure on the suction side and in the tail-race tunnel could cause dangerous separation of the water column. Understanding the flow features that lead to the instable behaviour of pump turbines is a prerequisite to the design of machines that can fulfil the growing requirements relating to operational flexibility. Flow simulation in these instability zones is demanding due to the complex and highly unsteady flow patterns. Only unsteady simulation methods are able to reproduce the governing physical effects in these operating regions. ANDRITZ HYDRO has been investigating the stability behaviour of pump turbines in turbine operation in cooperation with several universities using simulation and measurements. In order to validate the results of flow simulation of unstable operating points, the Graz University of Technology (Austria) performed detailed experimental investigations. Within the scope of a long term research project, the operating characteristics of several pump turbine runners have been measured and flow patterns in the pump turbine at speed no load and runaway have been examined by 2D Laser particle image velocimetry (PIV). For several wicket gate positions, the flow fields in the vane-less space at runner inlet observed in the experiment are compared with the results of unsteady CFD flow simulations. Physical phenomena are visualized and insight to flow phenomena is given. Analyses using both results of simulation and measurement allow deriving a consistent explanation of the fluid mechanical mechanisms leading to the S-shaped instability of pump turbines.