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中文摘要：
通过混流式水轮机全流道的定常流动数值模拟,研究混流式水轮机内部尤其是尾水管在不同工况下的流动特点,目的在于探明引起混流式水轮机内部流动不稳定的真正原因。计算结果表明,引水部件的流动,蜗壳鼻端处压力波动均较为剧烈,周向分布不均匀,但是经过固定导叶和活动导叶的过滤后周向分布基本对称。转动部分的流动,小开度低单位转速时,较小的导叶出流角,使转轮叶片头部受到撞击,叶片上横向流动和背面的叶道涡严重,转轮出口靠上冠处有回流和横向流动,泄水锥下方回流严重;大开度时,转轮进出口流态都得到改善。尾水管内,小开度时,锥管中心回流严重,大部分水流流向外缘,受肘管的影响,锥管和肘管内部形成两个涡流区,主流流经支墩左侧,右侧较为紊乱;最优开度时,尾水管内部水流流线顺畅,支墩两侧水流平稳性基本一致;大开度时,尾水管主流向锥管中心聚拢,经过肘管的转弯时,出现很多局部的旋涡流动,支墩右侧水流相对平稳,而左侧较为紊乱。研究结果为压力脉动测量位置的选择提供理论依据。
英文摘要：
The flow features in the interior of in Francis turbine, especially in the draft tube are studied. The main aim is to find the cause of inducing the hydraulic instability in Francis turbine. The flow features in each flow passage are shown. In inducer components, pressure fluctuations of nose of spiral case are anomalous and pressure distributions of spiral case outlet are asymmetric on different openings at the same unit speed. But circumferential pressure distributions are symmetrical at stay vane outlet and guide vane outlet. Under the small opening and low unit speed, due to minor guide vane outlet angle, the impinging streams at the head of blade are severe. And there is the flow pattern of cross-flow from hub to shroud at blade inlet. Interblade vortex can also be visible. And there are big back flow regions and cross-flow at blade outlet near crown. When the opening becomes bigger, the flow conditions at runner outlet near crown and inlet are improved. In draft tube, with small opening, there are also serious back flows in the center of conical tube and main flow is located at regions near the wall. Due to the effect of elbow tube, the two vortex regions are formed in conical and elbow tube. It will augment the intensity of vortex in conical tube and back flow below the runner cone. And then the runner outlet flow will be disturbed. The mainstream flows through the left side of pier and the flow state on the right side of pier is disordered. With optimal opening, the flow state at runner outlet and in draft tube is good. And the flow flieds on both sides of pier is identical. And with bigger opening, the flow flieds at runner outlet are improved and the main stream is located at the center of conical tube. Some local vortexes appear on account of the turn effect of elbow tube. They impede the upstream flow. And the flow flied at the right side of pier is good and the flow state on the left side of pier is disordered. The effect of pier is also distinct. This results provide theoretical basis for the select
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