A Case Study About Improving The Efficiency Of A Hydro-turbine System By Vortex Enerators

Hydro turbine is a water conservancy equipment which transforms the energy of water into the driving force through which can a power generation system work. There is always an important part called draft tube in francis turbines. Draft tube has two functions, one of which is guiding the water downstream and the other is to recover the kinetic energy of water flowing from the runner exit. But in actual use, there could be some drawback of draft tube such as flow separation. In order to solve these problems we suggest here a type of vortex generator in the draft tube to improve the turbine working performances and finally increase the turbine working efficiency. To do so can we get better to make use of the kinetic energy of water. Our work can be divided into6chapters as follows.Chapter1:Starting with the introductions the background and importance of the research subject. Then the functions of hydro turbine and the draft tube is presented as well as the drawbacks of draft tube. In addition, we itemized different kinds of methods to improve the performance of draft tube. The advantages and disadvantages of each method are compared. Finally we put forward various of vortex generators and depict their structures. The applications of each vortex generators are also described.Chapter2:The fundamental conceptions of grid are illustrated, including grid cell, grid size and grid deformation. Then the basis requirement of grid is presented which contains consistency of geometry, consistency of solution and compatibility of numerical methods. Summary on the classify of grid is made. Grid generation software called Gridgen and a file format named PLOT3D are introduced.Chapter3:The construction of hydro turbine applied by Finland Waterpumps Oy. is explained. The grid generation of different parts of the turbine is achieved. An optimized method based on both Gridgen and Fortran77that can actually make grid points distribution be better has been put forward. Finally we generated the grids of draft tube installed different vortex generators.Chapter4:Three component parts of CFD technology containing pre-processing, solver and post-processing are described. Then the conception of turbulence is explained, as wall as the turbulence models and the computational methods of turbulence. The ideas of wall functions and domain interfere are introduced. Finally the converge criterion and the working parameters of the turbine are exposed.Chapter5:The computational method of turbine efficiency is illustrated, basing on which method can we get the turbine’s working performance curve. The drawbacks of the draft tube have been got. Then we analyzed the12different optimized cases qualitatively and quantitatively. Finally we got the best case and explain the practical significance.Chapter6:The work is summarized and the conclusion remarks are presented.