| In the tail-water tunnel of the hydropower station, the rapidly changing process of water stress and flow rate induced by factors such as load increasing or decreasing of turbine, opening and closing of turbine, opening and closing of the sluice gate, is called hydraulic transients. To prevent the danger of water hammer, the hydraulic characteristics of transients in tail-water tunnel of hydropower station under several working condition must be studied in the stage of designing hydropower station system.The pressure and free flow combined hydraulic transients model of the tail-water tunnel is established with Preissmann Slot Method. The water surface profile in steady flow and the fluctuation of water level and pressure in unsteady flow under certain working condition are calculated and compared with the results of the experiments, by which the model above proves to be correct and effective. Simulating the hydraulic parameters in the load-increased condition, load-thrown-off condition of large fluctuation transition period and other combined working condition, the process of water level fluctuation of surge tank and several key sections of the tail-water tunnel is obtained.The results show that Preissmann Slot Method could effectively simulate the hydraulic transients of free-pressurized flow in the tail-water system. When the water level downstream is closed to the top of tail-water tunnel, the intermittent high pressure water hammer would be induced. |
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