Development And Analysis Of A Million Kilowatt Grade Full Capacity Boiler Feed Water Pump Turbine Exhaust Casing

With the gradual advancement of national energy conservation and emission reduction policies,high power and high efficiency have become the main development direction of large domestic power plants.The localization development design of the million-grade boiler feed pump steam turbine has extremely high practical significance for breaking the foreign technology monopoly in this field and ensuring national energy security.Feedwater pump turbine is the driver of feed pump in power plant.Its efficiency and reliability are closely related to the operation cost and market competitiveness of power plant.The exhaust cylinder of a steam turbine guides the steam flow from the outlet of the last stage rotor blade to the condenser,and its aerodynamic performance affects the efficiency of the whole unit.The cat’s claw of the exhaust cylinder supports half the weight of the whole unit,so the rigidity of the exhaust cylinder determines the stability and reliability of the unit.Firstly,this paper describes the research status of exhaust cylinder aerodynamic performance and strength at home and abroad.Various studies have shown that the physical structure of diffuser and volute in exhaust cylinder determines the dynamic pressure recovery ability of exhaust cylinder,and the way to improve the exhaust cylinder aerodynamic performance is clear.Then the calculation method of industrial steam turbine exhaust cylinder based on computational fluid dynamics is introduced.Using CFX to analyze the aerodynamic performance of existing K56 rows of cylinders,it is found that the numerical results of CFX software under different working conditions are basically consistent with the values in the corresponding criteria.It shows that the method can be used to evaluate the aerodynamic performance of exhaust cylinders.The trend coincidence of the two curves also demonstrates that the fluid model,eddy viscosity model and wall function for high Reynolds number flow near the wall are basically accurate.According to the meridian diagram of the low pressure section,the development and design of the feed pump steam turbine are completed,and the 1:1 three-dimensional modeling is completed by Solid Works,and the fluid calculation domain of CFX is obtained.Through the coupling calculation of the last cascade and exhaust cylinder of steam turbine,the influence of different diffuser structure parameters on the dynamic pressure recovery coefficient and total pressure loss coefficient of exhaust cylinder as well as the uneven coefficient of exhaust cylinder outlet is analyzed,and the relatively excellent combination of parameters is found by comparing the simulation results under different structure parameters.At the same time,the influence of different internal bracing pipe and baffle structure on the kinetic energy recovery performance of exhaust cylinder was analyzed,and the appropriate internal bracing structure was found.Finally,ANSYS software is used to analyze the strength of exhaust cylinder.Simulate the restraint and force of the cylinder in the actual situation,check whether the stress and strain of the key parts meet the actual needs of the project.Considering the cost of production,the weight of the cylinder can be reduced by reducing the thickness of each steel plate of the welded cylinder row,and the rigidity of the cylinder block can be increased by increasing the local support of the thinned cylinder row.Finally,a turbine exhaust cylinder with relatively good aerodynamic performance and rigidity is designed.