| The paper regards Danjiangkou hydraulic power station expanding units project as the project background, which has a better expanding units primary conditions and carry on better opportunity of the expanding units with water-allocating from south to north at the same time, the expanding units can get better electric consumption benefit. The main work of the paper is the three-dimensional turbulence calculation in the hydraulic turbine application, setting up the three-dimensional turbulence model of the hydraulic turbine draft tube theoretically, and carrying on three-dimensional emulation calculation to it. By drawing it through three-dimensional simulation emulation, It can offer the good water flow state to the hydraulic turbine draft tube, cut down water head lose, improve hydraulic turbine efficiency, and reduce cost of draft tube model test. It also has important theory meaning and practical value.Particularly, the work of the thesis includes the following main contents:1) Narrate the overview of Danjiangkou hydraulic power station expanding units project and development situation of three-dimensional flow simulation emulation calculation in hydraulic turbine, expound the thought of setting up turbulence model of hydraulic turbine draft tube.2) Analyze the three-dimensional turbulence mathematical model of the elbow draft tube in the paper (k-s two equations model for three-dimensional stationary flow and Reynolds stress seven equations model for three-dimensional unsteady periodic flow), Besides, it also introduces the method to solve the general differential equations; The three-dimensional question discretization, the mesh system discretization and the boundary conditions discretization.3) Simply explaining two kinds of three-dimensional modeling methods of hydraulic turbine draft tube, namely the horizontal section method and the oblique section method; the latter one is adopted by author with modeling.4) Regard the hydraulic turbine (HL220-LJ-380) of Danjiangkou hydraulic power station expanding units project as the target of calculating, which establishes the model of the draft tube, carries out three-dimensional stationary flow emulation calculation and three-dimensional unsteady periodic flow emulation calculation on the basis of selecting the size of the drart tube, and analyzes the result of calculation. It draws device conclusion and actual project meaning of draft tube in Danjiangkou hydraulic power station expanding units project.The focal points of the thesis are:(1) By comparison of two methods, the oblique section method is confirmed for Danjiangkou expanding units project, using Auto CAD and Pro-ENGINEER softwares to establish the draft tube model.(2) Deeply analyzing the controlled equations and three-dimensional turbulence model, it has led out general differential equations and derived the dispersed format of general differential equations by the limited volume method. It also derives calculation formulas of various dispersed coefficient to set up three-dimensional turbulence model of draft tube and confirm the solving method.(3) To solve the difficulty in the flow field calculation, it proposes staggered grid tosuit flow calculation and explore the application of flow simulation in hydraulic power station by software FLUENT. Utilizing GAMBIT in FLUENT software to mesh the model, adopting unstructured tetrahedron mesh instead of the commonly used structured hexahedron mesh. It has improved the accuracy of calculation of the numerical simulation effectively and carried on three-dimensional flow simulation emulation to draft tube and analyze the result finally. |
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