| 徐洪泉,王万鹏,廖翠林,赵立策,张驰也.叶道涡危害及机理研究[J].中国水利水电科学研究院学报,2023,21(5):466-475 |
| 叶道涡危害及机理研究 |
| Study on the harm and mechanism of channel vortex |
| 投稿时间：2023-01-14 |
| DOI：10.13244/j.cnki.jiwhr.20230005 |
| 中文关键词: 混流式水轮机 叶道涡 小负荷 类转频压力脉动 叶片裂纹 |
| 英文关键词:Francis turbine channel vortex low-load condition pressure pulsation with quasi-rotating frequency blade crack |
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| 中文摘要: |
| 为弄清混流式水轮机叶道涡是否引起压力脉动及危害、危害机理和程度，本文在模型观测试验的基础上结合电站实际进行了深入研究。本文首先介绍了叶道涡模型试验的方法及结果，结合压力脉动频谱分析及尾水管空化观测结果，指出叶道涡工况出现的频率接近转速频率的压力脉动由叶道涡引起，其频率随单位流量增加而增高，随单位转速增加而降低。叶道涡空腔随水流进入尾水管后，以转轮出口环向流速旋转，空化空腔在转轮叶片出口压力场扰动下产生收缩-膨胀甚至溃灭-生成的循环，衍生出新生压力脉动。叶道涡多发生于低单位转速的低负荷工况及高单位转速的大负荷工况，和水电站实际发生的类转频压力脉动非常一致，其频率覆盖范围也基本重叠，因此可推断类转频压力脉动由叶道涡压力脉动引起。研究还发现，三峡等大型水电站发生过该类型小负荷、类转频强烈压力脉动，由叶道涡引起;天生桥一级、二滩、李家峡等电站发生的转轮叶片出水边裂纹、尾水管锥管进口撕裂等破坏同样由叶道涡压力脉动危害造成。 |
| 英文摘要: |
| In order to find out whether the channel vortex for Francis turbine can cause pressure pulsation and its harm，the mechanism and degree of the harm，this paper conducted in-depth study based on the model observation test combined with the actual power plant.In this paper，the experimental methods and results on channel vortex are introduced firstly，and then combined the spectrum analysis of pressure pulsation and the cavitation observation in the draft tube，it is indicated that the pressure pulsation with a frequency close to the rotational frequency is caused by channel vortex.The frequencies of pressure pulsations increase with the increase of unit discharge and reduces with the increase of unit speed.The channel vortex flows into the draft tube and it rotates at the utlet circumferential velocity of the runner.The cavitation cavity produces a contraction-expansion cycle so much as disappearance-rebirth cycle under the disturbance of the pressure field at the runner outlet，and additional pressure pulsation will be generated.Channel vortex mostly occurs under low-load conditions with low unit speed and high-load conditions with high unit speed，which are very consistent with the conditions when there are pressure pulsations with quasi-rotating frequency.Their frequency range basically overlaps.Therefore，it can be concluded that the pressure pulsations with quasi-rotating frequency is generated by channel vortex.This type of pressure pulsations with quasi-rotating frequency under low-load conditions，which was caused by channel vortex，has occurred in Three Gorges hydropower plant.Cracks at runner blade outlet and avulsion at the inlet of draft tube cone，which appeared at Tianshengqiao first-level，Ertan and Lijiaxia hydropower plants，were also caused by pressure pulsations of channel vortex. |
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