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为了获得水电站水轮机技术改造中混流式转轮上冠型线变化时水轮机水力性能的变化规律,本文以某混流式水轮机模型转轮为研究对象,在原转轮上冠型线的基础上,提出了四种改型的上冠型线方案,采用CFD方法对不同上冠型线的转轮内部流动特性、能量特性、空化性能及过流能力进行了数值模拟和对比分析。结果表明:上冠型线的适当上抬可以增大转轮的过流能力,并且改善转轮在大流量工况下的能量特性和空化性能;但过高的上冠型线对小流量工况下的叶道涡的位置和强度有负面影响;与原转轮相比,方案4的效率略有提高;小流量工况时,上冠型线越高,叶道涡的位置越靠近叶片头部,且涡的强度越大,从而使转轮效率降低;大流量工况时,上冠型线上抬可能导致叶片进口靠上冠部分出现回流,进而导致压力分布不均匀;上冠型线的改变对最优工况下转轮效率和内部流动特性影响较小;可以为水轮机技术改造中转轮的改型设计与性能预估提供必要的参考。
In order to obtain the variation regularity of the hydraulic performance of the turbine when the crown line of the Francis turbine changes in the technological transformation of the hydropower station, this paper takes a Francis turbine as the research object. Based on the crown line of the original runner, Four kinds of retrofit top crown schemes were used to simulate and compare the flow characteristics, energy characteristics, cavitation performance and overcurrent capability of the runners with different crown lines by CFD method. The results show that proper lifting of the upper crown line can increase the overcurrent capacity of the runner and improve the energy performance and cavitation performance of the runner at high flow rate. However, The efficiency and efficiency of program 4 are slightly higher than that of the original runner. In the case of small flow rate, the higher the crowning line, the closer the position of leaf vortex vortex Blade head, and the greater the strength of the vortex, thus reducing the efficiency of the runner; large flow conditions, the crown on the lift may lead to the upper part of the blade inlet reflux, resulting in uneven pressure distribution; the crown The change of profile line has less influence on the wheel efficiency and internal flow characteristics under the optimal conditions; it can provide the necessary reference for the retrofit design and performance prediction of the wheel in the technical transformation of turbine.