Investigation Of Fluid Flow And Heat Transfer Characteristic Inside Complex Stator Structure For Large Generator

The research of physical fields inside large generator is a synthesis problem which refers to multi-disciplines and multi-specialties. There are some difficulties and engineering significances to calculate physical fields in generator accurately because of complex stator structure, rotation of rotor and multi-coupled of physical fields, which has become one of the most difficult problems of international electrical machine field.In this dissertation, some documents about electromagnetic field, fluid field, temperature field and multi-couple fields are researched, the development of this issue is discussed and the shortcomings of research are given. The purposes, significance and contents of research for problem are confirmed.The numerical relationship of stator strands eddy loss of generator and strands structure is found based on electromagnetic field theory. The eddy loss variation orderliness of stator strands, especially different structure strands along radial direction high are indicated and analyzed. Strands eddy loss distribution characteristic under the condition of changing strands width because thickness variation of stator main insulation, and the theory method of main insulation thinning that is strands structure optimization is proposed. At the same time, the generator 2D eddy magnetic field solved model was built and the stator iron loss distribution orderliness along radial height are given by using of numerical calculation, which change the inaccurate assumption that the stator iron loss is average at the tooth and yoke respectively during computation. The calculation precision of fluid field and temperature field inside stator is enhanced from loss angle.A concept of circular flow object in generator is indicated, and the incompressible viscosity fluid field with circular flow object inside stator radial ventilation duct of large generator under single path ventilation system is numerically calculated using finite volume method (FVM), fluid flow characteristic inside radial ventilation duct with circular flow object or not are compared, distribution characteristics of the fluid velocities along radial direction and circumferential direction of stator are given, meanwhile the fluid flow inside pipe is solved, the results calculated and measured results are compared. The problem that heat transfer coefficients were difficult to determine is solved.The heat transfer characteristics of generator stator are numerically researched using indirection and direction couple method of fluid field and temperature field respectively, the effect of fluid flow characteristic inside radial ventilation duct on stator temperature field is analyzed, and the space distribution orderliness of fluid velocities, fluid temperature, surface heat transfer coefficients inside ventilation duct and stator temperature are investigated, numerical relationship of multi-fields couple inside generator stator complex structure is ascertained. The design method of generator stator strands with different structure is given by distribution characteristic of generator temperature and main insulation temperature drops with different structure strands.Heat transfer characteristic inside large generator stator changing main insulation structure is analyzed based on coupled field theory, and the feasibility of stator strands structure optimization was proved from the multi-coupled angle of electromagnetic loss, fluid flow and heat transfer. Furthermore, the stator temperature distribution characteristics are researched numerically under condition of stator row insulation conductivity coefficient variation and part structure aging of row insulation, the effect of row insulation on symmetry of stator temperature is confirmed.The corresponding research can be made more detailed and deeply by the investigation, which not only improves the calculation precision of large generator physical fields but also extends research range of couple fields in generator. Scientific strands structure and ventilation structure are adopted, which can decrease the loss in the generator, improve the ventilation effect of large generator at the same time, reduce the accident rate, elevate the working performance and improve the operating reliability and security of large generator.