挑流阶梯消能工水力特性研究

Stepped energy dissipator has been widely used in water conservancy and hydropower projects due to its simple structure and high energy dissipation. But, it is greatly restricted because cavitation damage may occur and energy dissipation may decrease since the flow depth increases and the inception location of air entrainment to the flow moves downstream, then the air entrainment into the flow is not adequate under the conditions of large unit discharge. In the present research project, a kind of ski-jump-step energy dissipator is developed, which supplies the adequate air into the flow in order to overcome the restrictions mentioned above by means of ski-jump bucket (and air entrainment basin). Meanwhile, the atomization resulted from flood discharge could be avoided due to small water head for only ski-jump. The object of this research project is to make the unit discharge achieve 160m3/s.m from the conventional 60m3/s.m under the conditions of high energy dissipation and of safe structural forms. On the basis of theoretical analysis and physical model experiments, the works includes: (1) the principle and structures of the ski-jump-step energy dissipator: to investigate the relationship of air concentration and cavitation number of the flow, the energy dissipation, pressure (and pulsating pressure), and precipitation to the geometric and hydraulic parameters; (2) the hydraulic characteristics of ski-jump (including air entraiment basin): to determine their geometric forms presenting adequate air to the flow on the stepped spillway; (3) the hydraulic performance and classification of the stepped spillway: to keep high energy dissipation and safe structures in the flow with large unit discharge. This study is interesting in theory and application for water conservancy and hydropower projects.

阶梯消能工由于结构简单、消能率高在水利水电工程中有良好的应用。但是，在大单宽流量下，阶梯消能工水深加大，掺气起始点大大下移，不足的掺气将使其消能率大为下降，更严重的是掺气不足将引起结构严重的空蚀破坏。本项申请提出一种挑流阶梯消能工，利用挑流空中掺气和掺气池掺气，使阶梯消能工上的流动充分掺气，拓宽阶梯消能工在大单宽流量下应用。本项申请的目标是：在高效消能条件下，使阶梯消能工安全运行的单宽流量从传统的60m3/s.m提高到160m3/s.m。本项申请的主要内容和方法为：运用理论分析和模型试验，1）提出流动掺气浓度、水流空化数、消能率、脉动压力和降雨量等与挑流阶梯消能工结构参数和水力参数等的理论表达式；2）挑流段（包括掺气池）水力特性研究，提出为阶梯消能工提供充分掺气的挑流坎和掺气池结构体型；3）阶梯消能工水力特性研究，提出高效消能的结构体型和分级等。本研究对工程建设有良好的理论意义和应用价值。

阶梯溢洪道（消能工）由于结构简单、消能率高在水利水电工程中有广泛的应用。然而，在大单宽流量下，阶梯溢洪道流动水深加大，掺气起始点大大下移，不足的掺气使其消能率大为下降，更严重的是掺气不足将引起结构严重的空蚀破坏。本项研究提出了一种挑流阶梯溢洪道，利用挑流空中掺气和掺气池掺气，使阶梯溢洪道的流动充分掺气，拓宽阶梯溢洪道在大单宽流量下应用。项目研究主要内容和重要结果包括：（1）挑流阶梯溢洪道基本水力特性研究，结果表明：在原型单宽流量达到118.0 m2/s的大单宽流量下，消能率远高于传统的阶梯溢洪道，阶梯消能段有良好的掺气浓度，掺气池和阶梯溢洪道段压力分布合理。在高效消能和有效减免空蚀风险的基础上，将传统阶梯溢洪道的单宽流量上限提高了近一倍。（2）挑流阶梯溢洪道前置掺气结构的水力特性研究，结果表明：前置掺气具有全断面掺气和掺气效果随单宽流量增大而提高的特征，消除潜在的掺气盲区。（3）以挑流阶梯溢洪道在滑行水流状态为研究对象，在其水力特性研究的基础上，提出消能面积的概念，针对水平阶梯、尾坎阶梯和反坡阶梯等阶梯结构，给出统一的滑行水流的出流余能估算方法，进一步论证挑流阶梯溢洪道在消能方面的优势。此外，新增内容（4）提出了一种水跃阶梯溢洪道，进行其水力特性的研究，在大单宽流量下，可以获得高效的消能和有效减免空蚀的风险。拓宽了研究范围，丰富了研究内容。.本项研究全面完成项目的研究内容，并有所超额。成果在国际著名行业期刊（SCI收录，第一标注）已公开发表论文7篇，中文核心一篇，授权发明专利2项，IAHR组织的国际会议宣讲论文4篇；培养硕士研究生一名，博士研究生2名，并有一名博士研究生在IAHR组织的全球肯尼迪学生论文竞赛中入选半决赛。.本项研究丰富了阶梯溢洪道（消能工）的理论基础，在高坝泄水建筑物的泄洪消能方面有良好的应用前景。