引水式水电站变顶高尾水洞水力特性和体型优化

考虑引水式水电站常用的有压尾水洞和变顶高尾水洞两类布置型式,采用基于特征线法的有压管道瞬变流分析模型和适用于明满流过渡过程分析的改进狭缝法模型,分别分析系统的过渡过程特性和尾水洞体型参数的敏感性,研究不同的尾水洞型式下尾水系统的水力特性,进一步揭示了变顶高尾水洞的底宽、洞高和顶坡对尾水管进口最小内水压力的影响规律。结果表明,与增大面积的有压尾水洞比较,变顶高尾水洞是一种可行的布置型式,可有效提高尾水管进口的最小内水压力且水锤过程衰减较快;合理增大变顶高尾水洞底宽、洞高或顶坡均可不同程度地改善尾水管进口最小内水压力,其中顶坡的影响相对明显,为体型优化设计提供了参考依据。

Hydraulic Characteristics and Body Type Optimization for Changing Top-altitude Tail Tunnel in Diversion Type Hydropower Station

Considering two commonly used layout types of water diversion hydropower stations: the pressurized tail tunnel and the changing top-altitude tail tunnel, transient analysis model of pressurized pipeline based on the method of characteristics and the improved slot model for analyzing the transition process of mixed free-surface-pressurized flow were adopted. The transient characteristics and the sensitivity analysis of body size parameters of tail tunnel were analyzed, respectively. The hydraulic characteristics of tail system with different tail tunnel types were studied. Furthermore, the impact of bottom width, height and slope of the changing top-altitude tail tunnel on the law of the minimum water pressure at the draft tube inlet was revealed. Compared with the pressurized tail tunnel with enlarged area, the results show that the changing top-altitude tail tunnel is a feasible choice. It can effectively increase the minimum water pressure at the draft tube inlet and make the water hammer process attenuate faster. The minimum water pressure at the draft tube inlet can be improved by increasing bottom width, height or slope of the changing top-altitude tail tunnel, among which the influence of slope is more obvious. It provides a reference basis for body-type optimization design of the changing top-altitude tail tunnel.