The Length Of The Blades Of Francis Turbines Based On Numerical Simulation Of Flow Field Study

People have been looking for good methods which can work well in a wide operation range to precisely predict comprehensive performance of hydro unit, including efficiency, cavitation property and stability,sd as to reduce cost in test and model-making.CFD (Computational Fluid Dynamics) technology which is developed in recent years has the characteristics of agility, short cycle, low cost, and so on. This technoogy provides researcher with a new and effective researching means. We think that properly applying mathematic model and computational technology for turbulent flow in the hydraulic turbine, and conducting flow simulation and computation are the feaasible researching methods and are also the development trend of hydraulic turbine flow computation.As the core component of hydraulic turbine, blade plays an important role in the integrated performance of the hydraulic turbine. For the analysis of the flow effect cause by different blade, this paper conducts three-dimensional turbulent numerical simulation for two different runner and draft tube of the HLA351-LJ-170 Francis turbine. This paper establishes geometric model for runner and draft tube of the hydraulic turbine according to actual parameters, use structural grid division to build grid, choose standard k-εturbulence model and SIMPLEC algorithm.By analyse the results of two hydraulic turbine's numerical simulation in different operation condition. This paper receives these points'achievements:1. When turbine does not work in optimum operationg condition, especially in small flow operationg condition, the velocity and stresses on pressure/suction side and the leading edge of the blades are asymmetry. There is some unstable vortex in draft tube either. All this are one of the most import factors make the turbine's efficiency down.2. Long blade model is better than short blade model in energy performance^cavitation performance and stability of turbine. Long blade model is a better choice for this kind of hydraulic turbine.3. Finally, based on the flow field computation result, this paper conducts the performance pre-evaluation for this hydraulic turbine's runner and draft tube.