1. Study of Sediment Erosion in Guide Vanes of Francis turbine
Ravi Koirala1,2, Hari Prasad Neopane1, Baoshan Zhu2, Bhola Thapa1
1Turbine Testing Lab, Department of Mechanical Engineering, Kathmandu University, Dhulikhel, Nepal
2State Key Laboratory of Hydroscience and Engineering, Tsinghua University, Beijing, China
April, 2017

2. Contents
Background
Sediment Erosion in Guide Vanes
Research Focus
Investigation through GV cascade
Investigation through RDA setup
Conclusion

3. Background
Global Initiative to utilize renewable technology – hydropower is flexible and consistent renewable energy source
Production cost consistency, low operation and maintenance cost and environmental acceptability make it more reliable
Prior to developing new projects, identification of existing problems, its causes, severity and mitigation approach is essential
Figure Global sediment deposition proportion and undeveloped resources
[Edenhofer, Madruga, & Sokona, 2011], [Gleick, 1993]

4. Background
Sediment - major problem with turbines operating in Nepal – where prime electricity source is hydropower
Francis turbine is projected to be one of the most used system in future projects
Turbine Testing Lab, Nepal
Working in developing erosion resistant Francis turbine
Earlier attempts on design optimization of runner has set the scope of research
Guide Vanes
Stationary component in Francis turbine performing movement as per requirement through pivoted support
Regulates flow to runner

5. Background
Clearance gaps are applied to allow movement of vane though pivoted support
Cross flow occurs through this gap
In presence of sediment in water:
Increases gaps
Increases roughness
Affects life and performance
Figure Clearance Gap in Francis turbine
Figure Cross Flow though Guide Vanes

6. Sediment Erosion in Guide Vanes
Figure Summary of Guide Vane Erosion Mechanisms
Turbulence Erosion
Secondary Flow Erosion
Leakage Flow Erosion
Acceleration Erosion

7. Sediment Erosion in Guide Vanes
Figure Sediment Erosion in faces of Guide Vanes
Figure Sediment Erosion at Guide Vane edges and facing plate

8. Sediment Erosion in Guide Vanes
Figure Clearance gap measurement location
Figure Guide Vane Erosion at A+C
Figure Guide Vane Erosion at B+D

9. Observation
Erosion on Leading edge, trailing edge, faces and clearance gaps were observed

10. Research Focus
Prior to development of Francis turbine to address regional problems-laboratory estimation is essential
Experimental investigation of erosion is a destructive process
Simplified system is required
Forward two possible approaches on laboratory estimation of erosion:
Rotating Disc Apparatus [RDA]
3 Guide Vane Cascade System

11. Investigation though 3GV setup
Meridional Velocity
Tangential Velocity
Figure Design method of 3 Guide Vane setup
Figure CFD analysis of flow cascade

12. Investigation though 3GV setup
Figure Position-wise tangential and normal velocity distribution at Guide Vane Outlet

13. Investigation though 3GV setup
Bypass
Sand Hooper
3GV Test Setup
Operating Conditions
Head
0.1 MPa
Flow
0.006 m3/s
Sediment Feed rate
7.8 gm/sec
Particle size
150 – 300 µm
Tank Inlet
Tank Outlet
Pressure Tank
Sump Tank
Figure Experimental Setup for erosion testing in 3 Guide Vane system

14. Investigation though 3GV setup
Figure Mass loss with respect to sediment passed
Figure Erosion on Aluminum Guide Vanes
Figure Effect of erosion on pressure around guide vanes

15. Investigation though RDA setup
Disc speed
458 rpm
Sediment Concentration
66.67 gm/ltr
Particle size
150 – 300 µm
Figure Experimental practice in Rotating Disc Apparatus

16. Investigation though RDA setup
Figure Selection of Guide Vane Profile for erosion handling

17. Conclusion
Erosion on Leading edge, trailing edge, faces and clearance gaps were observed
Simplified setup is essential for testing
3GV setup and RDA is suitable option
Effect of erosion in terms of weight loss and flow around vanes can be observed

18. Thank you for your attention!
Contact :
Turbine Testing Lab
Kathmandu University,
P.O. Box : 6250
Phone :