Location: Hydro Power Project, Himachal Pradesh, India
The Francis turbine is a type of reaction turbine, a category of turbine in which the working fluid comes to the turbine under immense pressure and the energy is extracted by the turbine blades from the working fluid. The desire to accurately comprehend the flow features within turbines has been an area of much concern. This is result of the need to predict their performance characteristics, determine the cavitation properties of the turbine and to further improve their efficiency.
The objective of the CFD study was to analyze the flow through a Francis turbine runner using CFD to evaluate the flow behaviour inside the runner, determine and locate the area with minimum pressure on the blade surface (areas susceptible to cavitation), and to predict the hydraulic efficiency of the runner.
To ensure the accurate transfer of the fluid pressure field obtained in CFD the finite vol. mesh of the fluid domain is used as finite element mesh of blades in stress analysis. The finite vol. mesh obtained from CFD contains only shell elements at all faces of blades this shell mesh is converted into 8 nodes tetrahedral parabolic elements.
Three simulation cases were considered for this study:
Runner blades with maximum erosion.
Runner blades with minimum erosion
Optimized Runner blades.
Modal Analysis, Fatigue and Stress Analysis were carried out for various scenarios like:
Fluid pressure load
Centrifugal loads of runner running at a speed of 300RPM
Centrifugal loads running at speed of 545RPM during Free running condition.
Crack analysis and Life Estimation for runner blades were also analyzed for static and dynamic loading to identify the crack initiation and propagation