Francis Turbine Runner Retrofit Study

In the hydraulic turbine runner factory of middle and small scale, we can use some small modification, such us guide vane quantity changing, trailing edge cutting and lines adjusting which in meridian view, to improve runners which can not satisfy tasks demand because of the operational environment changing. The key of modification is raise the efficiency or enhance power the runner can supply. Although replace with a new runner may generally fit best, the cost of this approach is also maximum. Consequently, it is important of seeking for some straightforward procedure to improve these situations.Firstly, the design method of runners and the method of numerical calculation has been introduced. Then FINE / TURBO package for numerical simulation of the original runner has been used, and the simulation results compare the actual flow field to verify the applicability of the package. After the method of cutting trailing edge of blades, increase or decrease the number of guide vanes and the change in the crown ring lines, and modified under the program of cutting blades and guide vanes with a detailed change analysis, the optimal value of the two programs has been acquired. Finally, the original data parameters of the model blades, with its efficiency as the objective function, using genetic algorithms to optimize the parameters of several blades to get the highest efficiency.The method of computational fluid dynamics (CFD), combined with FINE / TURBO package is used, and an HL240-WJ50 turbine was simulated to reveal effects these single adjustment would have. Then the blades were optimized using several optimization methods. Conclusion is as follows:(1) When reduce the number of guide vanes, the flow rate increases while efficiency decreases slightly. Hence, this approach can serve the purpose of capacity increase. However, reducing the role of guide vanes will reduce its diversion, and the structure may lead the runner instability.(2) When cut the trailing edge, the efficiency will drop, but with the openings between the blades increases, the capacity will increase over. In this article, up to 18% capacity increase when the cutting quantity become 30 millimeters.(3) After the model parameterization, database generation and optimization process, a new blade is obtained, and making the efficiency of the runner up 2.47%.