CFD-based Turbine Runner Blade Length Numerical Simulation Of Three-dimensional Space

In the process of hydraulic turbine operation, because the water contains undissolved gas, sand and other impurities, and on the surface of the sand’s crack, there are many nuclei, when the pressure drops below the vaporization pressure, the undissolved gas, nuclei then the bubble formed which called cavitation, cavitation will make its flow components many damages to turbine, so the hydraulic turbine will create noise and vibration. If the cavitation is serious, it will reduce the turbine efficiency or even worse, it can not work normally. Therefore, the cavitation is always the main problem of turbine designment, manufacturing and scientific research, but also is an important to efficiency and quality. Because of the complexity of the cavitation flow phenomena, the experimental study has many difficulties, however, with the development of CFD (computational fluid dynamics) and computer performance, using numerical simulation has become an important method to analyze the problem. This method does not need a large number of experiments, it can predict the experimental data, in order to improve reliability and save money.Considering the operation environment of China’s hydropower, hydraulic turbine runner’s cavitation is very necessary. For the analysis of internal runner cavitation flow, we will take long blades runner and long and short blades runner as my models to study turbulent cavitation using the method, numerical simulation of three-dimensional.According to the actual parameters of HLA351-LJ-170turbine, using the3D modeling software Pro/ENGINEER to establish two kinds of hydraulic turbine model, the long blade and short blade,using unstructured tetrahedral mesh,computational fluid dynamics knowledge and CFD software FLUENT6.3, with the most widely used RNG κ-ε model of Reynolds averaged method and mixture model to simulation of the long blades and short blades turbine runner in the different flow conditions, such as flow rate, pressure and gas concentration distribution. Through the numerical simulation, it can be accurately calculated the total area of cavitation on the runner, cavitation of the regional level. Under the same operating conditions, the results show that, the internal length of blade runner of turbine flow rate, pressure distribution and cavitation performance and short blades are better than the long blade of turbine runner, so it is of great significance to the designment, the optimization and modification of hydraulic turbine.