Flow Field Simulation Analysis Of Dynamic Water Shutdown Of Main Inlet Valve Of Pumped Storage Power Station Based On CFD

With the development of society,people’s demand for power system stability is getting higher and higher.Pumped storage power station’s unique performance of peak load regulation and valley filling,frequency and phase modulation,and the ability to deal with power grid emergencies,has gradually become an indispensable and important part of China’s power grid.Compared with conventional hydropower stations,Pumped Storage Power Station has more complex operating conditions and more frequent working conditions conversion.Under extreme conditions,how to maintain the safe and stable operation of units is very important.However,the flow state of pumped storage units under load rejection condition is very complex,which also poses a severe test for the safe and stable operation of pumped storage units.Therefore,it is of great practical significance to study the transition process after load rejection.At present,the commonly used numerical simulation methods of transition process include one-dimensional characteristic line method and three-dimensional CFD method,both of which have certain limitations.In order to explore the three-dimensional transient flow process and characteristics of the main intake valve in a pumped storage power plant under two conditions of the guide vane rejection and the guide vane coordinated closure during load rejection,this paper combines the two methods to study the two different shutdown modes participating in the regulation of the transition process after load rejection in a pumped storage power station.Firstly,the water diversion pipeline system of the pumping power station was established by one-dimensional numerical simulation calculation method.The characteristic characteristics of the main inlet valve closed and the main inlet valve and the vane closed together were calculated under the load-shedding condition.When the unit is running under the rated working condition of the turbine,the load is suddenly unloaded,the vane is rejected,and the main inlet valve acts to intercept the water flow.The effect of the closing on the adjustment guarantee calculation is similar to the vane closure.When the unit is running under the rated working condition of the turbine,the load is suddenly unloaded,and the vane and the main inlet valve are closed.In the first way,the guide vane 25 s is closed linearly,and the main inlet valve 64 s is closed linearly;the second way,the guide vane is rejected,and the main inlet valve 64 s is linearly closed,and the transient value of the transition process is compared.By comparing the extreme values of the calculation results of the transition process,it is found that the parameters such as the maximum pressure before the valve,the maximum speed rise,the maximum pressure at the end of the volute and the peak flow rate through the valve are better when the guide vane-main intake valve closes in a coordinated manner.Secondly,a three-dimensional physical model of the main intake valve is established,and then a three-dimensional simulation model is established.The boundary conditions of the flow field simulation are defined by using profile file.Realizable k-e turbulence model is selected to simulate the three-dimensional transient flow process in the main intake valve under two shutdown modes.The pressure curve before the valve is calculated and compared with the one-dimensional numerical simulation results.The result has small error and high reliability.Thirdly,the evolution process of internal flow field under two shut-off modes is analyzed.The results show that the CFD simulation results of three-dimensional transient flow process inside the main intake valve under two shut-off modes have high accuracy;the internal flow field of the main intake valve is complex during the shut-off process,and the eddy current formed will change the internal flow direction,resulting in greater pressure loss in the valve chamber;The change of pressure brings hidden danger to the safe operation of the unit.The maximum pressure in the valve chamber appears at the pivot under the two closing modes,and the maximum pressure and flow velocity under the co-closing mode are relatively small.