Study On Hydraulic Transition Process Of Hydropower Station With Long Pressure Diversion System

When hydropower is operating,the frequent changes in load of turbine lead to the turbine guide vane closing quickly affected many parameters,such as water pressure in penstock,water level in the surge tank and unit speed parameter.At the same time,hydraulic transition process had a serious impact on the safe operation of the hydropower.Therefore,it is necessary to carry out the research on hydraulic transient process of hydropower station. In this paper,the hydraulic transient process of long diversion hydropower station is studied according to the basic principle and practical calculation method of numerical calculation of transition process,combined with the engineering pratice.Main contents of this paper are:(1) Using characteristic line method ,the paper estabishes an analysis mathematical model of hydraulic transient of pressure water diversion system of diversion type hydropower station,and manifold boundary conditions are reasonably treated,including water inlet boundary,impedance surge chamber boundary,bifurcate pipe boundary and water turbine boundary,and so on.And the calculation of surge pressure fluctuation in the water diversion system of the power station water diversion system is realized.(2) In this paper,form a long diversion type hydropower station for example,closing law of guide vane were optimized to determine the best guide vane closing law;and by changing the effective guide vane closing time,discussed the relationship between guide vane closing time and maximum pressure at the end of volute in the diversion type hdropower.(3) In this pa per, the transition process of large fluctuation of hydropower station is calculated.The change process of the unit speed and the pressure at the end of the spiral case,the fluctuation process of the water level in the surge chamber and the pressure distribution along the tunnel are obtained.The calculation results show that:in the transient process of the station diversion type hydropower, large flow inertia in pipeline lead to water level fluctuation cycle pressure chamber long and large amplitude of pressure fluctuation at the end of the volute appeared obvious main wave and coda points.(4) The hydraulic disturbance process were calculated,the results shows that:in the long diversion type hydropower station,when the part of the unit in the same hydraulic unit discard all load,water level fluctuation of the surge chamber will affect the operation of the unit for a long time.But even so,the attenuation trend of the surge in the surge chamber is very obvious,which proves that the water diversion system is stable under the selected calculation conditions.