中文摘要：

全面系统地分析了特大口径水轮机进水球阀在直线关闭、二阶段关闭情况下的动水关闭过程，选择可能出现的最不利工况，研究进水阀前后压力及机组流量的变化过程。通过研究发现，二阶段关闭有效地降低了水轮机进水球阀的最大水击压力，但同时在拐点处引起了尾水管压力以及机组流量的波动。在此基础上，深入进行阀门内部流场整体和细部结构的数值模拟，发现球阀内部涡区分布与水击压力最大点之间的必然联系。

英文摘要：

The hydrodynamic closure process of the intake ball valve of hydroturbine is analyzed compre- hensively and systematically based on the closure law of the straight line and two-stage. The pressure prior to and after the intake valve, the change of the unit discharge and the best law of the hydrodynamic closure are studied in the worst case. The closure law of the two-stage reduced the water hammer pressure effec-tively; however, the pressure of the draft tube and flow rate have fluctuated. On this basis, the numerical simulation and visualization of overall and detail in inner flow field of the ball valve is applied; and the connection between the vortex in the ball valve and the maximum point of the water hammer pressure is found.