Investigation Of Heat Convection And Thermal Distress In The Insulation For Large-scale Turbine Generators

With the growing of energy demand and the development of power generation technology,the advantages of nuclear plants are increasingly highlighted.Waterhydrogen-hydrogen cooled steam nuclear power turbine generators get further progress.Due to its large capacity,high thermal and electrical loads,and the impact of rotor rotation and vibration,its rotor insulation system is relatively weak.Meanwhile,under the demand of environmental protection,more and more coal-fired power plants have been converted into gas-steam combined cycle power plants,and the matched large-capacity air-cooled steam turbine generators get a springback develoment.The air-cooled steam turbine generator generally adopts single-channel ventilation system,which makes the temperature of the stator much higher than that of rotor.The insulation system of the stator is difficult to operate safely under the condition of the high thermal and electric load and vibration.To investigate the problems above descriptions,the dissertation takes a 1100 MW nuclear water-hydrogen-hydrogen turbine generator rotor and a 150 MW thermal power air-cooled turbo generator stator as research objects,the contents are organized as follows.Firstly,based on the actual structure of the turbine generator,the 3D fluid flowing and heat transfer coupling mathematical models with complicated wind path as precondition boundary are established to calcualate and analyze fluid and temperature fields.The temperature distributions of the windings,iron cores,insulation and fluid of the nuclear power turbine generator rotor under healthy insulation,the velocity distribution of fluids in coordinate directions,as well as the relationship between surface velocity and heat dissipation coefficient in ventilation trenches are studied.Since the rotor rotation and air-gap axial air intake have an effect on air intake of the stator radial ventilation groove,taking a single-channel ventilation system of the coal-fired plant aircooled turbo-generator as study object.A corresponding stator-rotor coupling calculation model is established and analyzed.The temperature distribution of each components and fluid distribution in the ventilation channel are analyzed.The influence of the air-gap intake air volume on the stator temperature field and radial ventilation channel flow is also studied.Secondly,the rotor temperature field of the 1100 MW nuclear power turbine generator considering rotor rotation is calculated via finite volume method.The effect of incidence angle change of hydrogen in the winding,the varied additional rotor core losses and short-time overcurrent of rotor windings on the fluid temperature and velocity field,as well as the heat transfer law of the rotor insulation are analyzed.The stator main insulation of the 150 MW air cooling turbine generator can occur shelling gap under the action of electric,thermal and mechanical.Oxidation reaction can gradually increase the shelling gap in the main insulation.Thus,temperature distributions of the turbine generator stator parts,e.g.windings,insulation,air in the shelling gap,core componets under the different shelling degrees along the axial and circumferential directions are analyzed.It can provide a theoretical basis for fault diagnosis and safe operation of the turbine generator.Thirdly,the distribution of the heat transfer coefficient on the fluid-solid interface of the stator of 150 MW air-cooled turbogenerator is calculated and analyzed.The axial variation curve of the heat dissipation coefficient on the windward side of the winding is fitted to correct the original expression.Due to the influence of the material properties of the insulation on the heat transfer of the insulation,the temperature distribution of the stator using high thermal conductivity insulation materials is analyzed.On this basis,the electric and temperature fields of high thermal conductivity powder in the case of uneven doping of stator main insulation are investigated.It gives a reference for the development of new main insulation material applied to generator.Finally,in order to investigate the influence of different electric and thermal factors on the stator main insulation shelling,electric-thermal-fluid coupling finite element models of the turbine generator stator under main insulation thermal disdress are established.The influence of the thermal conductivity of the main insulation and the shelling gap degrees on the stator electric and thermal fields is highlighted and analyzed.Based on the calculated results,the prediction of the remaining life of insulation thermal damage caused by the electric-thermal dual factor is proposed.Based on the(Radical Basis Function)RBF neural network model,the insulation thermal conductivity,dielectric constant,maximum electric field intensity,and maximum insulation temperature are taken as input samples,and the average temperature difference between insulation and windings is regarded as output samples to predict the remaining life,which supplements the defect of single factor prediction of remaining life and improves the prediction accuracy.Through the research on the heat exchange law of the turbine generator stator and rotor insulation,health status,materials and residual life prediction under insulation fault conditions,the results can better guide the development and safety run of turbo generators.