Research On Fluid And Temperature Field Of Air-cooled Turbine-generator With Novel Stator Ventilation Structure

Since the adoption of air-cooling technology,large turbo-generators have gradually attracted great attention from all over the world due to their simple structures,easy operation and maintenance,and high security.The development of "gas-steam combined cycle" power generation technology,the increase of global electricity consumption and the higher global requirement for energy conservation and environmental protection are all demanding larger capacity for air-cooled turbo-generators.At present,the main way to increase the capacity of generators is to increase the electromagnetic load of the generator,which is accompanied by the increase of winding loss.In this case,if the ventilation cooling system cannot take away the generated heat in time,the temperature of stator winding of the generator will sharply rise,which may possibly make the stator winding and the core burnt and therefore cause huge economic losses.To maintain a normal status for the air-cooled turbo-generator with an increased electromagnetic load,a better ventilation cooling structure need to be adopted to control the temperature of the generator.The study of new-type ventilation structure is an inevitable work for the development of air-cooled turbo-generators to those with larger capacity,and therefore is of great significance for air-cooled turbo-generators.In this thesis,with a 150MW full-air-cooled turbo-generator taken as an example,a novel stator ventilation structure where axial vents that are arranged in the stator teeth is proposed.Firstly,a global two-dimensional electromagnetic field model of the generator is established based on the actual size of the generator.The air gap magnetic flux density,stator tooth magnetic flux density and stator core loss of the generator are calculated,and then the measured stator core loss value is compared with the calculated one to verify the accuracy of the calculation.The influence of the size and position of the axial vents to the air gap magnetic flux density,stator tooth magnetic flux density and stator core loss of the generator are also calculated and analyzed.Secondly,two-dimensional global ventilation system fluid network models of the generator in half axis are established based on the actual size of the generator.The total airflow amount,the air gap airflow amount,airflow amount in the sub-slot of the rotor and airflow amount in the stator end of the generator are calculated.A comparison between the calculated value of total air volume and the measured one is made to verify the accuracy of the calculation.To improve the amount of air flowing into the axial vents,air-introducing plates are proposed to be provided beside the axial vents.The influence of the new-type stator vent structure on the total and branch airflow amount are calculated and analyzed.Furthermore,three-dimensional fluid models of the generator stator in the aspects of a tooth,two half slots and a half axis are established respectively.The fluid flow patterns in the air gap and the axial vents are calculated and analyzed,and the influence of the size and position of the axial vents and the presence or absence of the air-introducing plate on the fluid flow in the axial vents and the stator radial ventilation ducts are also calculated and analyzed.Finally,based on the theory of fluid and heat transfer,flow-heat transfer models of the generator stator in levels of a tooth,two half slots and a half axis are established respectively.The temperature distribution law of the generator stator is reached and analyzed.A comparison between the measured winding temperature and the calculated one is made to confirm the accuracy of the calculation.The influence of the size and position of the axial vents and the presence or absence of the air-introducing plate,on the maximum temperature,average temperature and temperature distribution of the stator windings,insulation and teeth are further calculated and analyzed.