Study On Optimizing The Length Of Inlet Chamber Of Circulating Water Pump Station In Power Plant

The inlet of the circulating water pump station is an important part of the circulating water system of fire/nuclear power plant.The rationality of its layout is related to the safe,stable and efficient operation of the power station.The pump sump is an important structure connecting the forebay and the circulating water pump in the inlet channel.Its role is to smooth the flow of the forebay and provide smooth and uniform inlet conditions for the pump impeller chamber.Longer pump sump can ensure the ideal inflow conditions of the pump,but the corresponding area and engineering investment are large,especially when some projects are limited by objective conditions and cannot guarantee sufficient length of the water absorption chamber,necessary flow pattern optimization measures need to be taken.Therefore,under the premise of ensuring the good inflow conditions of the pump,it is of practical engineering significance to study the flow channel rectification anti-vortex technology that shortens the length of the pump sump to improve the operation efficiency of the power plant and reduce the engineering investment.In this paper,the physical model and mathematical model are established based on the inlet channel of a circulating water pump station with a ’outside-in-out’ side inlet rotary filter layout.The flow pattern and rectification measures of different lengths of pump sump are systematically simulated and optimized.The main contents and research results are as follows(1)Under the premise of considering the small amount of engineering,the back wall distance of the suction pipe and the diversion vortex-proof structure at the bottom of the suction pipe were optimized.The model test results show that the optimized rear wall spacing is reasonable,and the wedge-shaped diversion cone can effectively prevent the generation of vortex,ensuring the smooth and uniform inlet flow of the pump suction pipe.(2)The test verifies the rationality of the water absorption chamber length 7.5D(D is the diameter of the pump horn)recommended by the existing specification.The physical model test results show that the side inlet rotary filter(outside inlet and inside outlet)is adopted in the flow channel of the pump station.When the length of the pump sump is not less than 7.5D recommended by the specification,the good inflow conditions of the pump can be ensured without or with a small increase in the rectification and anti-vortex measures(such as the anti-vortex breast wall).(3)A complete set of rectification anti-vortex measures to shorten the length of the pump sump was proposed in the experiment.According to the test results,a set of rectification and anti-vortex measures are put forward,which are triangular diffusion guide wall+cylindrical uniform diffusion pier+anti-vortex chest wall at the inlet of the pump sump.The minimum submerged depth of the anti-vortex chest wall is 0.5 D,and the flow area ratio of the cylindrical uniform diffusion pier is not less than 0.50.By taking this optimization measure,the length of the pump sump is greatly shortened.Through the system optimization rectification measures,the influence of filter bias on the pump sump is weakened,and the velocity distribution before the pump suction mouth is uniform.There is no surface vortex and water vortex in the pump sump,and the inlet flow of the circulating pump is ideal.(4)The feasibility of the above optimization measures is further verified by threedimensional numerical simulation.In view of the shortcomings of long model test cycle,sparse measurement points and limited simulation conditions,the threedimensional numerical model was used to conduct a detailed simulation of the hydraulic characteristics in the convection channel.The simulation results were in good agreement with the model test data,indicating that the optimization measures to shorten the length of the suction chamber were reasonable.The selected turbulence model can better predict the flow characteristics in the inlet channel.The complete set of rectification vortex elimination technology for pump sump can effectively shorten the length of pump sump,save engineering civil construction investment,and have significant economic benefits.The research results and simulation methods have reference value for the optimization design of inlet passage of circulating water pump station in similar fire/nuclear power plant.