低比速水泵水轮机“S”形特性对尾水管最小压力敏感性研究

Study on the Sensitivity of S-shaped Characteristics of Low Specific Speed Pump-Turbine on the Minimum Pressure of Draft Tube

水泵水轮机“S”形特性对机组的水力过渡过程有着要的影响,“S”形特性的优劣是判定模型转轮研发成功与否的关键指标之一,对低比速水泵水轮机显得更为重要。为更深入研究转轮“S”形特性、模型转轮优化设计、水力过渡过程三者间联系,本文定义一种对“S”特性曲线定点定量的分析方法,利用不同试验特性曲线,通过水力过渡过程仿真分析加以判定,对“S”形曲线量化分析以探索三者之间的内在联系。研究表明全特性曲线中间等开度线“S”区弯曲程度对尾水管最小压力敏感性最强,等开度线在“S”区内单位流量与单位转速的比值越大,同一等开度线上飞逸单位流量越大,对提高尾水管进口最小压力越有利;叶片型式和活动导叶翼型优化设计可在一定程度上改善“S”形特性品质,提高甩负荷时尾水管最小压力值。本研成果在低比速水泵水轮机模型转轮研发和水力过渡过程优化计算方面均具有一定参考意义。

The“S”shaped characteristics of pump-turbines have an important impact on the minimum pressure of draft tube.The quality of the“S”shaped characteristics is one of the key indicators to determine the success of model runner development,and this indicator is particularly important for ultra-low specific speed pump-turbines.In order to delve deeper into the inherent relationship between the S-shaped characteristics of the runner and the optimization design and minimum pressure of draft tube,this article first defines a method for fixed-point quantitative analysis of the“S”shaped characteristic curve.Then,different experimental characteristic curves obtained from multiple optimized designs of the runner are used to calculate the hydraulic transition process.At the same time,the“S”shaped curve is quantitatively analyzed,and the relationship between the three is explored through continuous analysis.The results show that the bending degree of the equal opening lines in the middle at the“S”shape characteristics curves has the greatest influence on the minimum pressure at the draft tube inlet.The greater the ratio of unit flow difference to unit speed difference in the“S”shape characteristics curves of the equal opening line,the greater the runaway unit flow on the same equal opening line,the more favorable it is to increase the minimum pressure at the inlet of the draft tube.The optimal design of blade type and guide vane airfoil can improve the minimum pressure value of draft tube to a certain extent.The conclusions obtained in this paper can be used for reference in the research and development design of low specific speed pump-turbine runner and the optimization calculation of transition.The results have reference significance in both the research and development low-specific-speed pump-turbine model and the optimized calculation of hydraulic transient.