水电站变顶高尾水洞瞬变流计算及体型设计

Transient flow calculation for sloping ceiling tailwater tunnels and their body-type design for hydropower stations

对水电站变顶高尾水洞内明满交替流计算方法及变顶高尾水洞体型设计进行了研究,介绍了变顶高尾水洞的工作特点.采用改进狭缝法模型,结合某大型水电站取消尾水调压室方案进行瞬变流计算,提出了明满交替流分界点的处理方法.分别针对具有不同顶坡、底坡和底宽的变顶高尾水洞体型在不利工况下的瞬变流计算成果进行比较分析,结果表明,变顶高尾水洞具有一定的尾水调压室作用,若适当地选取体型参数可不设尾水调压室;顶坡对整个尾水系统的影响非常大,底坡和底宽的影响相对较小.

A study is made on the methods for calculation of the unsteady freesurface pressurized flow in tailwater tunnels with a sloping ceiling and their bodytype design, and an introduction is given to their operational characteristics. Based on the improved slot model, a transient flow calculation is performed to verify the scheme of canceling the tailwater surge tank at a largescale hydropower station, and a separation point treatment method for the unsteady freesurface pressurized flow is proposed. Aiming at tailwater tunnels with different top and base slopes and different bottom widths, a comparative analysis is made on the calculated results under some adverse conditions. The results indicate that, by reasonable selection of the bodytype parameters, the tailwater tunnel with a sloping ceiling can replace the tailwater surge tank, so it is feasible to cancel the surge tank, and that the gradient of the top slope has a great effect on the tailwater system, while the effects of the gradient of the base slope and bottom width are relatively small.