向家坝水电站右岸变顶高尾水洞的水力计算

向家坝水电站尾水下接金沙江，江水位变幅大，尾水隧洞选用变顶高尾水洞方案时可不建尾水调压室，但洞内压力和明满交界面会随水流过渡过程变化。经建立包含引水系统、机组和调速器在内的计算机仿真程序的水力过渡过程计算表明，变顶高尾水隧洞方案在明满交替流工况下，未产生气囊，洞顶内水压力变幅不大，对机组没有产生不利影响，电站调节系统能满足大、小波动稳定的要求。

Hydraulic calculation for tailrace tunnel with variable crown heights for underground powerhouse in right abutment at Xiangjiaba Hydropower Station

Tailrace water from Xiangjiaba Hydropower Station flows into the Jinsha River in which water level fluctuates greatly. Design alternatives for three kinds of tailrace tunnels with free flow,pressure flow and variable crown heights are studied. For the scheme of tailrace tunnel with variable crown heights, tailrace surge chamber can be omitted,but pressure and interface between free flow and pressure flow would vary with flow transition.Based on computer simulative program including diversion system, units and governors ,hydraulic transition computation is performed for whole power station regulation system under different conditions and tailrace tunnel flow fluctuation and its influence on units are studied. Simulative computation results show that gas pockets did not occur under altered free flow and pressure flow conditions in variable crown height tailrace tunnel, and internal. Water pressure changes a little in the crown, which didn't make adverse effect on the units. Power station regulation system reaches stability against fluctuations with different degrees.