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中文摘要：
通过混流式水轮机定常和非定常流动计算,研究混流式水轮机在不同开度下的流动特点,阐述非定常流动分析结果。非定常流动计算结果表明：开度a12时,转轮出口靠近上冠处压力脉动不显著,中间流线和下环处脉动较为强烈;尾水管中涡带主要集中于直锥段,呈螺旋型,在肘管处逐渐变小消失。尾水管内部压力脉动主要集中在直锥段和肘管,频率为低频,是转频的0.233倍;其中直锥段脉动幅值较大,内外两侧压力脉动频率基本一致。开度a24时,转轮出口靠近上冠处没有回流,脉动小,中间流线和下环处压力脉动更为剧烈,脉动频率为转轮频率与叶片数乘积的倍数;尾水管涡带在直锥段水流形成的呈柱状涡,在肘管变成较小的螺旋型涡带,其结果是长的涡带在尾部形成像钻机式的切削作用,对水轮机效率和稳定性产生严重的影响,涡带的长度为研究混流式水轮机尾水管深度和优化设计提供理论依据。
英文摘要：
The flow features are presented on different openings in Francis turbine by unsteady numerical simulation. The unsteady flow results are as follows： when the opening is 12 mm, pressure fluctuation at runner outlet near hub is not obvious and pressure fluctuation amplitudes near midstream and shroud are bigger. Helical vortex is situated on conical tube on opening 12 ram. It will disappear at the elbow tube. Pressure fluctuation of low frequency in draft tube is mainly located at conical and elbow tube. The frequency of helical vortex is low and is about 0.233 times that of runner frequency. And pressure fluctuation amplitudes in conical tube is higher. Frequencies of two points on the same measurement section are almost equivalent. But when the opening is 24 mm, there is no back flow region at runner outlet near hub and pressure fluctuation amplitude is smaller. And the ones near midstream and shroud are greatly higher. The frequency is several times that of product of runner frequency and blade number. The columnar vortex formed in conical tube will become small helical vortex in the elbow tube. The result is that the long vortex rope forms the cutting effect like drilling rig on the empennage. It will have serious effect on the tubine efficiency and stability. The length of vortex rope provides the theoretical basis for studying the depth of Francis turbine draft tube and optimization design.
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