Study On The Flow Pattern Evolution Characteristics Of The High-power Air-cooled Turbo-generator In The Multi-wind Area Of ??the Basin

Large-scale thermal power units have been the mainstream of China's electric generator due to their high energy conversion efficiency and good system stability.As the key equipment of thermal power generation,the increase of the capacity of a single generator can reduce the cost of unit capacity and material consumption.However,accompanying the increase of the single generator capacity is excessive electromagnetic load and thermal load,which will lead to a substantial increase in the temperature rise of the generator.Therefore,the increase of turbo-generator capacity depends on the reasonable cooling structure.Air cooling system has been occupying a dominant position in China's turbo-generator industry due to their simple structure,convenient maintenance,and high safety and reliability.Therefore,studying the ventilation structure of air-cooled turbo-generators and analyzing the flow characteristics of the fluid field in the generator are of great significance for improving the cooling effect of air-cooled turbo-generators and designing larger capacity generators.Firstly,this thesis takes a 350 MW air-cooled turbo-generator as the research object.According to the characteristics of its internal ventilation structure,the all-air-cooled,self-ventilated cooling system is emphatically introduced.The running path of cooling medium in the local fluid region,such as stator,rotor and end of generator,is introduced in detail.According to the characteristics of its physical structure,the calculation domain of the generator is selected reasonably.Secondly,on the basis of the corresponding solving conditions which are given,the finite volume method is used to numerically study the three-dimensional fluid field of the cooling system during the steady state operation of the generator.On the premise of verifying the correctness of the numerical study of the fluid field,the flow rate and velocity of the cooling medium in the space of the radial ventilation channel of the stator and rotor and the sub-slot of the rotor are analyzed respectively.The flow pattern evolution law of cooling medium which in the multipath ventilation system of the large air-cooled turbo-generator is revealed.Finally,in order to elucidate the influence of different rotor end structures of a large-scale air-cooled turbo-generator on the flow rate distribution and fluid flow pattern in the rotor domain.Two optimization schemes are proposed for the rotor end structure of the generator by adding baffle and small rotor fan based on the original ventilation structure.The flow rate distribution in each wind area of the generator is taken as the basis for checking the accuracy of the calculation.The effects of flow rate and velocity spatial distribution in the rotor axial and radial air ducts for different end structures of the rotor are compared and analyzed.In this thesis,the numerical simulation and structural optimization of the ventilation and cooling system in the multi-wind zone of large-scale air-cooled turbogenerator are carried out.The results provide theoretical references for the design and performance optimization of large-scale generator ventilation systems.