Fossil fuels such as oil and coal are being consumed in mass quantities. Due to this mass consumption we are being faced with serious environmental issue and also being affected by the lack these fossil fuels. To counteract the problem caused by the exhaustion of energy resources, people have begun to pay more attention to natural renewable energy. This is not only being looked at by our country but the whole world in general. Amongst the many available renewable energy resource the world is paying particular attention to hydro power which employes the concept of circulation of water. This is a clean energy resource because no CO2 is emitted in the process of being used. In specific hydro power generator with capacity below 70∼500kW being looked at because of its small and simple structure.
The Francis turbine is an inward flow turbine that is the most efficient and widely used water turbine in the world today. In Francis turbine, water passes through the series of blade rows and changes its direction from radial to axial. Even though the turbine has high efficiency, studies are still on going to improve the efficiency even by a small amount. Conventionally this was done by making test models or conducting full-scale tests which was time consuming and expensive. Recent developments in computer capability have increased the use of numerical methods such as computational fluids dynamics (CFD) in the design and optimization of the turbine. CFD is an inexpensive tool which can be used to investigate the internal flow characteristics of the turbine with good accuracy and can be used to achieve significant improvements in efficiency.
In this paper the description of the internal flow in a Francis turbine is addressed. 3D viscous flow simulation with SST k-ω turbulence model is conducted using the commercial code of the ANSYS CFX version 11.