Numerical Simulation And Performance Analysis Of Three-Dimensional Turbulent Flow In Francis Turbine

With the development of hydraulic turbine in recent years, high energy performance , good cavitation performance and stability of turbine are more important then ever. Considering the achievement aboard on the design of high performance hydraulic turbine, CFD is an important design approach to obtain accurate and detailed data of inner flow. Therefore, it is significant to totally understand the inner flow of all passage components to predict the performance of hydraulic turbine and improve its design. And it is the validity method to optimize the turbine design.The distuibution of axial plane stubs and stub crossing points are non-uniform and quantity of them is not equal when the blade is made by using traditional design method of turbine. These are not benefit with calculating wood model and drawing. In this paper, to make blade wooden patterns is using blade mean camberline. This makes the wooden patterns meet the demand of the design and meet the shape of the runner blade. And this can agree with requirements of hydro and mechanical analysis and making the model of blade by using the numerical control machine. It has reference value to whole design of turbine. Low specific speed France turbine is made by this method.In order to study the hydraulic performance and the stability of turbine, the CFD of the designed low specific speed Francis turbine is done. Through the details simulation calculation of typical operation conditions of turbine, some conclusions are showed: the design of the overflowing parts is appropriate; the flow in the draft tube is smooth in the optimal operation conditions, the rotation direction of the vortex band is reversed to the runner in the large flow, and the rotation direction of the vortex band is identical to the runner in the small flow. Through the analysis of the overflowing parts, some fruits are gained: the hydraulic loss of the diversion parts becomes small when the opening angle becomes small; the hydraulic loss of runner is the smallest in the optimal conditions, and the initial cavitation coefficient become small when the opening angle becomes large; The loss of the draft tube concentrates in elbow bend when the flow is large and concentrates in the right cone when the flow is small.Combining with Empirical formula and using the UDF in the FLUENT, theprogram of the intensive analysis about wearing on overflowing parts of turbine which is induced by sand is worked out. Through the optimal simulation with the theory of two-phase turbulent flow, the abrasion in the runner crown and the working face is serious. The field of maximum velocity of the particle phase is in the working face approach to the runner inlet. The field of maximum density of the particle phase is in the working face approach to the runner outlet and the lower loop. The magnitude of the particle density approach to the blade is great.