Research On End Ventilation And Heat Transfer In Variable Speed Pumped Storage Generator-Motor At Different Speeds

Variable speed pumped storage generator-motor is a new type of pumped storage generator-motor by changing the rotor excitation alternating frequency to achieve a speed that follows its head and head change.AC excitation is used to change the rotor speed to improve the low turbine efficiency,increased cavitation,vibration and abrasion of pumped storage units during operation.However,the electromagnetic design,end electromagnetic fields and loss distribution,fluid flow and heat transfer mechanisms of variable speed pumped storage generator-motor lacked systematic research.In this paper,a 10 MW variable speed pumped storage generator-motor is used as a research object.Basic parameters of the generator-motor are designed.End electromagnetic fields,fluid flow,heat transfer and related influences are studied in depth.Development of larger capacity variable speed pumped storage generator-motor is provided as a theoretical basis.A firm foundation is laid for the optimal design of large domestic variable speed pumped storage units.Firstly,a 10 MW variable speed pumped storage generator-motor is parametrically designed.The electromagnetic design of the 10 MW variable speed pumped storage generator-motor is determined after several comparative studies.A mathematical and physical model of the two-dimensional electromagnetic field of the variable speed pumped storage generator-motor is established.Stator voltage,stator current and stator-rotor core losses are investigated under generator condition of generator-motor.The accuracy of the calculation is verified by test.A dual convergence method is used to determine the excitation parameters of variable speed pumped storage generator-motor at synchronous speed.A three-dimensional transient electromagnetic field model for variable speed pumped storage generator-motor is established.Losses in end members of variable speed pumped storage generatormotor under different speeds are calculated.Secondly,a mathematical and physical model of the ventilation network of10 MW variable pumped storage generator-motor is established.The air volume at each position of the variable speed pumped storage generator-motor at subsynchronous speed is calculated.A coupled fluid and heat transfer model for the end of 10 MW variable speed pumped storage generator-motor is established.The inlet velocity and outlet pressure calculated from the fluid network are used as boundary conditions for the three-dimensional end fluid and heat transfer coupling model.Fluid flow distribution in the end zone of variable speed pumped storage generatormotor at sub-synchronous speed is studied.Temperature distribution pattern of variable speed pumped storage generator-motor end components at sub-synchronous generator speed is analyzed.Finally,the wind volume at each position of the 10 MW variable speed pumped storage generator-motor is calculated at different speeds using ventilation network.The total airflow values at synchronous speed are compared with the total airflow measured in the test.The accuracy of the ventilation network calculation results and the feasibility of the ventilation network calculation method are verified.Boundary conditions using a coupled model of fluid and heat transfer at the end of the fluid network at different speeds are calculated.A three-dimensional end fluid and heat transfer coupling model is used to investigate the variation of fluid flow velocity in the end region of variable speed pumped storage generator-motor at different speeds under generator condition.Variation of the end member temperature under different speeds is revealed.The calculated end component temperature is compared with the test result.The accuracy of the temperature calculation results and the feasibility of the temperature calculation method are verified.