贯流式水轮机动静匹配作用下压力脉动特征分解与分析

Decomposition and Analysis of Pressure Pulsation Characteristics of Tubular Turbine under Dynamic and Static Matching Action

低水头贯流式水电站的发展是实现我国“双碳”目标的重要一环。由于其受来水量的影响较大,在运行过程中经常需要根据实际情况对导叶、桨叶的开度进行调节,并且保证二者的开启程度具有较好的匹配关系。本文选取了一贯流式水电站的某型号低水头水轮机,对其在7.22m水头下,导叶开度为60°时,桨叶开度分别选择36.29°以及57.24°下的内部流动情况进行了数值模拟研究。结果表明,36.29°的桨叶在这种情况下与导叶的协联关系较好,机组不仅有着高达93.27%的效率,同时其内部有着较好的压力脉动情况。采用变分模态分解(VMD)方法对得到的压力脉动信号进行了分析,合理地确定了压力脉动的组成成分。机组内的压力脉动主要以一倍叶频主导,尾水管内有着较低强度的低频压力脉动,而在大开度的桨叶下,机组内部有着明显的低频压力脉动成分,尾水管中出现了明显的压力脉动整体不稳定波动。本文提出了一种新的分析机组内压力脉动信号的方法,合理且清晰地展示了压力脉动的组成成分,为压力脉动的分析提供了新的方向指导。

The development of low head tubular hydropower station is an important part to achieve the goals of carbon peaking and carbon neutrality in China.Because this kind of hydropower station is greatly affected by the incoming water,it is necessary to often adjust the opening of guide vanes and blades according to the actual situation in the operation process,and ensure that the opening degree of the two has a good matching relationship.In this paper,a low head turbine of a tubular hydropower station was selected,and its internal flow was numerically simulated under head of 7.22 m,when the guide vane opening is 60°,the blade opening is 36.29°and 57.24°respectively.The results show that the 36.29°blade has a good association with the guide vane in this case.The unit not only has an efficiency of 93.27%,but also has a good internal pressure pulsation.The variational mode decomposition(VMD)method was used to analyse the pressure pulsation,and the components of the pressure pulsation were reasonably determined.The pressure pulsation in the unit is mainly dominated by double blade frequency,and there is a low-frequency pressure pulsation with low intensity in the draft tube.Under the large opening blade,there is an obvious low-frequency pressure pulsation component in the unit,and there is an obvious unstable pressure pulsation in the draft tube as a whole.In this paper,a new method for analysing the pressure pulsation was presented,and the components of the pressure pulsation were demonstrated reasonably and clearly,which provides a new direction for the analysis of pressure pulsation.