【作者】 冯永祥；

【导师】 练继建；

【作者基本信息】 天津大学 ， 水利水电工程， 2008， 硕士

【摘要】 二滩水电站是中国在二十世纪建成的最大水电站,电站设有2条龙抬头式泄洪洞,单洞最大泄洪流量为3800m3/s,设计最大流速为45m/s。龙抬头式泄洪洞在水利水电工程中应用十分普遍,大型龙抬头泄洪洞反弧段下游一般均具有流速高、单宽流量大、佛氏数低、底坡小的特点,为了减免泄洪洞的空蚀破坏,一般采用底部进气的掺气设施。通过设置掺气设施,大多数龙抬头泄洪洞都较好地防止了空蚀破坏。然而,二滩1号泄洪洞在采用常规的掺气设施后,虽然有效地减免了反弧段本身及反弧段下游底板的空蚀破坏,但反弧段下游侧墙仍出现了空蚀破坏,严重影响工程的安全运行。通过大比尺的模型试验,研究了多种掺气减蚀方法,提出了解决高流速、大流量泄洪洞侧墙掺气减蚀方案。2005年,采用反弧末端上游侧墙突缩(侧墙贴角)加凸型跌坎的三维掺气坎方案,对二滩1号泄洪洞2号掺气坎体型进行了改造。随后的水力学原型观测表明,2号掺气坎区域水流掺气浓度增加,底板和侧墙脉动压力和空化噪声测值平稳,且在合理范围之内。通过连续2个汛期的运行试验和现场检查,改造后的2号掺气坎体型结构完好,下游未发现明显的空化气蚀现象,成功地解决了侧墙空蚀问题。本文在总结前人研究成果的基础上,结合大比尺的水力学模型试验成果,分析了采用常规掺气减蚀设施后,大型龙抬头泄洪洞反弧段下游侧墙仍可能出现空蚀破坏的原因;针对已运行工程的特点,介绍了几种可能的解决泄洪侧墙空蚀破坏的掺气减蚀方案;对比分析了二滩泄洪洞原设计体型和改造体型的模型试验及原型观测情况,介绍了研究成果在二滩工程中的应用情况。更多还原

【Abstract】 Ertan Hydropower Station is the China’s largest hydropower project completed in the 20th century. The power station is equipped with 2 spillway tunnels with inlet raised. The maximum flood discharge of each spillway tunnel is 3800m3/s and the design maximum velocity is 45m/s. The dragon-raise-head spillway tunnel is widely applied in water conservancy and hydroelectric projects. The representative flow characteristics of the anti-arc bottom of the dragon-raise-head spillway tunnel are high velocity, large-unit discharge, low Froude and small bottom slop. Forced aeration device on soleplate is usually introduced to prevent cavitation damage of hydraulic structures in engineering. The cavitation damage is prevented effectively in many spillway dragon-raise-head tunnels by aeration facility. However, when conventional aeration facility was introduced in spillway tunnel No.1 of Ertan, the anti-arc and its downstream bottom were protected, but the cavitation damage still happened on the sidewalls downstream of anti-arc and it gave bad influence on the safety of the project. Large-scale model tests were performed to study the effectivity of many methods of aeration in cavitation-protection for the sidewalls, and the plan was given for spillway tunnel with large discharge and high velocity flow. The shape of 2nd aerator was renovated at the spillway tunnel No.1 of Ertan hydropower station according the research result in 2005 and a new-style three-dimensional aerator of contracting sidewalls (lateral deflector aerator) with heaving bucket was used. The following prototype observation and inspection indicate that the fluctuating water pressures and the cavitaion noise characteristics are smooth and in reasonable ranges. The shape and structure of 2nd aerator is in good condition and the cavitation is protected. The cavitation of sidewalls is resolved successfully.Basing on previous research and large-scale hydraulic model tests, the cause of cavitation damage to sidewalls in the anti-arc bottom of the large dragon-raise-head spillway tunnel, adopting conventional aeration in cavitation-protection, is investigated. In view of characteristics of running project, several plans of aeration in cavitation-protection to prevent cavitation damage are commended. Model tests and prototype observation for plan and modification shape are compared, the application achievements are introduced that research results applying in Ertan hydropower station.更多还原