明渠接竖井水电站引水系统的瞬变流规律

Transient flows in headrace system combining open channel and shaft for hydropower stations

明渠衔接竖井的水电站引水系统在增负荷时衔接处容易发生断流,在甩负荷时明流隧洞内可能会发生明满流交替.基于此,研究断流和明满流发生的条件,采用理论分析结合CFD数值模拟的方法开展研究,提出了相应的防止措施.首先基于溃坝波理论推导了断流发生的条件,采用断波公式给出明满流发生的条件;然后用CFD验证了这些判别公式的正确性,并且分析总结了流态规律;最后以某实际水电站为例进行了三维数值模拟分析,提出了限制增负荷值和运行水深来防止断流和明满流发生的措施.

Unsteady flows are induced in the headrace system of hydropower station combining open Chan- nel and vertical shaft when load changes. Water cut off may occur easily at the joint of diversion tunnel and shaft during load acceptance conditions. And the free-surface-pressurized flow may occur in the tunnel dur- ing load rejection conditions. The purpose of this paper is to study the condition of emerging these two harmful phenomena and to put forward corresponding prevention measures. An introduction to the mathe- matical model is given based on the dam break theory and the bore flow theory. The reliability of the meth- ods is verified and flow patterns are studied by simulations of CFD software. Three-dimensional numerical simulations of a practical power station are conducted; and the restrictions about the load increase and wa- ter depth for preventing the water cut-off and the free-surface-pressurized flow, are proposed.