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Study on the Numerical Simulation of Flow and Heat Transfer in the Air Gap of Turbo-generator

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Tutor: WangKun
School: Huazhong University of Science and Technology
Course: Thermal Power Engineering
Keywords: turbo-generator,cooling and ventilation system,flow and heat transfer,numerical
CLC: TM311
Type: Master's thesis
Year:  2013
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Abstract:
In the operating process of turbo-generator, a large amount of heat generated indifferent parts of the generator which caused by electrical and frictional losses. This heatshould be removed; otherwise, high temperature may cause damage in the generator. Inorder to guarantee the operating security and reliability of the turbo-generator, heat shouldbe absorbed and temperature in all parts should be kept at a reasonable range. Therefore, itis a very important significance to study the flow and heat transfer in the cooling andventilation system and improve the cooling effect of the turbo-generator.Due to the full use of computational fluid mechanics and numerical heat transfertheory, Computational Fluid Dynamics method can simulate the flow and heat transfereffectively. In order to make up the shortcomings of physical simplifications that causedinaccurate results, the CFD method was applied to simulate and study the flow and heattransfer in turbo-generator. Firstly, the air gap of generator has been simplified as anannular gap between rotating inner cylinder and concentric fixed outer cylinder, and theconvective heat transfer characteristic of which has been simulated. Distributions ofvelocity field, temperature field and heat flux have been analyzed at different Taylornumber. Comparing with the Nusselt number calculated by empirical formula, the averagerelative error of the averaged Nusselt number calculated by CFD simulation is at areasonable scope, which validates the effectiveness of numerical simulation. Additionally,in order to study the axial slots¡¯ impact on the flow, annular gap model with axial slots onthe surface is simulated. At the same time, the friction factor and friction loss are estimatedand validated. Finally, considering the interaction between the air gap and radial ventilationducts of stator, a model consisted of these two parts is simulated. Distributions of velocityand temperature field have been studied and the flow and heat transfer characteristics havebeen analyzed.Thought the study in this paper, the shortcomings of previous methods have been made up for, moreover, there is a deeper understanding of flow and heat transfer in theradial ventilation ducts and air gap been rotor and stator of turbo-generator. Some referenceand advice are provided, which can improve the cooling effect and operating security andreliability of turbo-generator.
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