Coupled Calculation And Analysis Of Multi-physical Field Of A Fully Air-Cooled Hydro-Generator Considering Rotational Condition

With the development and utilization of renewable clean energy,hydropower generation capacity has been growing.As a key power equipment of energy conversion(e.g.hydro-generators),the unit capacity has been on the rise.Now the ventilation cooling and heat transfer problems of large capacity hydro-generators have become the key problem in the design.In this thesis,a 250MW fully air-cooled hydro-generator in Wuqiangxi Power Plant is taken as an example.According to the actual structure size of generator and electromagnetic field theory,the mathematical model of 2-D electromagnetic field of the hydro-generator was established.The distribution of magnetic field of the generator,eddy current in damper windings and magnetic field of air gap were calculated and analyzed by using the finite element numerical method to solve electromagnetic field of generator.Based on this,the eddy current losses of damper windings and the amplitude of all times harmonics of air gap magnetic field were determined.And the additional losses of rotor were calculated by the numerical analysis method.Based on the above theoretical analysis,combining with the characteristics of heat transfer in hydro-generator,cold air flow and special ventilation cooling system structure of hydro-generators,the physical and computational model of 3D fluid and temperature coupled fields in the solved domain is established under the condition of rotor rotation.And the finite volume numerical method was used to calculate the fluid and temperature fields in the rotor calculation region.Firstly,the temperature changing with time and steady-state temperature distribution of the rotor internal heat source are obtained,and the variation of steady-state temperature of the heat source along the axial direction is analyzed.The calculated average temperature of excitation windings is compared with the measured data,which verifies the correctness of the method.Secondly,the maximum and average temperature of cold air and the non-heat source components are compared and analyzed respectively,focusing on the temperature distribution of pole body insulation,pole plate,upper and lower plate,end fluid and fluid between two poles,which have the bigger difference between maximum and average temperature.On the basis of this,the influence of air temperature at the inlet of support on the surface heat dissipation coefficient of excitation winding was studied.In order to solve the problem of fluid flow in the rotor solution domain,the velocity distribution on the windward and leeward sides of fluid between two poles,the velocity distribution on axial cross section at ducts and between two ducts,and the dynamic pressure distribution of fluid near the rotor heat source are calculated and analyzed respectively.For the change of rotor yoke ventilation duct structure,the influence of distance between adjacent ventilation ducts on the temperature distribution of excitation winding and the velocity distribution of fluid near the windward and leeward sides were studied.The effect of width decreasing degree of the ventilation duct outlet on the temperature distribution of the excitation winding windward and leeward sides surfaces,the velocity distribution of the circumferential and axial sections of the fluid between two poles and the temperature distribution of the fluid windward and leeward side.For the abnormal air path in rotor,the maximum temperature of excitation winding is calculated when the rotor yoke duct is different blocked.Therefore,the temperature distribution of pole body insulation,the velocity variation of the central line of fluid between two poles,and the velocity distribution of the axial cross section of ventilation duct in the middle of the shaft of the fluid between two poles are studied.