Study of sediment erosion in guide vanes of Francis turbine
Master thesis
Permanent lenke
http://hdl.handle.net/11250/2401220Utgivelsesdato
2016Metadata
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Sammendrag
The Himalayas and the Andes mountains are regions with some of the worldsbiggest hydropower potential. One of the biggest problems facing the developmentof these resources are high concentrations of hard minerals in the waterstreams. This causes severe sediment erosion in the hydraulic machinery. Asa result, the maintenance cost is increased and the power production decreases.
With a goal to learn more about this problem, NTNU and Kathmandu Universityhave initiated an large research cooperation. Together they have done a extensiveresearch on a Francis turbine in the Jhiruk Hydroelectric Centre in Nepal, whichoperates with a high sediment load. As an extension of this research, a test rigdesigned as a symmetric section of this turbine has been made at the WaterPower Laboratory at NTNU. The test rig, called the One GV Cascade, enablesresearchers and students to carry out experiments and study the passages flowconditions.
By carrying out a Computational Fluid Dynamics(CFD) and Particle ImageVelocimetry(PIV) analysis on this test rig, one can study in detail the flowaround different guide vanes(GV). Through comparing the CFD results with theexperimental results, it is possible to evaluate in detail how the different GVgeometries and clearance gap(CG) sizes will affect the flow. These results willhopefully make it possible to propose an improved GV design that causes lesssediment erosion in the Francis turbine system.
This master thesis will describe the basic theory, procedures and results fromthe CFD and PIV comparison. The main results shows that the new GVdesign(NACA 4412) has much better flow conditions compared with the referencedesign(NACA 0012). The new GV design creates a lot smaller pressure differencebetween the suction and pressure side. The effect of this is also obvious with15.7% lower clearance gap(CG) velocities, as well as a significantly smaller andweaker vortex filament.
To further confirm these results further studies has to be done. By designing anew test rig, with walls based on NACA 4412, the improved GV result can befurther validated. If the same results are obtained, NACA 4412 can be seen asa promising improvement in the effort of removing one of hydropowers biggest problems.
Keywords: Francis turbine, guide vane, sediment erosion, PIV, CFD.