Kathmandu University
Study of Sediment Erosion in Guide Vanes of
Francis turbine
Ravi Koirala1,2, Hari Prasad Neopane1, Baoshan Zhu2, Bhola Thapa1
April, 2017
1Turbine Testing Lab, Department of Mechanical Engineering, Kathmandu University, Dhulikhel, Nepal2State Key Laboratory of Hydroscience and Engineering, Tsinghua University, Beijing, China
CRHT VII, 2017 Kathmandu University 2
Contents
Background
Sediment Erosion in Guide Vanes
Research Focus
Investigation through GV cascade
Investigation through RDA setup
Conclusion
CRHT VII, 2017 Kathmandu University
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
3
Figure Global sediment deposition proportion and undeveloped resources [Edenhofer, Madruga, & Sokona, 2011], [Gleick, 1993]
CRHT VII, 2017 Kathmandu University
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
4
CRHT VII, 2017 Kathmandu University
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
5
Figure Clearance Gap in Francis turbine
Figure Cross Flow though Guide Vanes
CRHT VII, 2017 Kathmandu University
Sediment Erosion in Guide Vanes
• Turbulence Erosion
• Secondary Flow Erosion
• Leakage Flow Erosion
• Acceleration Erosion
6
Figure Summary of Guide Vane Erosion Mechanisms
CRHT VII, 2017 Kathmandu University
Sediment Erosion in Guide Vanes
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Figure Sediment Erosion in faces of Guide Vanes
Figure Sediment Erosion at Guide Vane edges and facing plate
CRHT VII, 2017 Kathmandu University
Sediment Erosion in Guide Vanes
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0
1
2
3
4
5
6
7
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Cle
ara
nce G
ap w
ith F
acin
g P
late
[m
m]
Guide Vane Position
8500 Hours
16500 Hours
Figure Clearance gap measurement location
Figure Guide Vane Erosion at A+C
Figure Guide Vane Erosion at B+D
0
1
2
3
4
5
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Cle
ara
nce G
ap w
ith F
acin
g P
late
[m
m]
Guide Vane Position
8500 Hours
16500 Hours
CRHT VII, 2017 Kathmandu University
Observation
• Erosion on Leading edge, trailing edge, faces and clearance gaps
were observed
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CRHT VII, 2017 Kathmandu University
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
10
CRHT VII, 2017 Kathmandu University
Investigation though 3GV setup
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Figure Design method of 3 Guide Vane setup
Figure CFD analysis of flow cascade
Meridional Velocity
Tangential Velocity
CRHT VII, 2017 Kathmandu University
Investigation though 3GV setup
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Figure Position-wise tangential and normal velocity distribution at Guide Vane Outlet
CRHT VII, 2017 Kathmandu University
Investigation though 3GV setup
13
Figure Experimental Setup for erosion testing in 3 Guide Vane system
Pressure Tank
Tank Outlet
Tank Inlet
Bypass
Sand Hooper
Sump Tank
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
CRHT VII, 2017 Kathmandu University
Investigation though 3GV setup
0
0.2
0.4
0.6
0.8
3 6 9 12 15 18 21
% C
um
ula
tive
Wei
ght
Lo
ss
Weight of Sediment passed [Kg]
Figure Mass loss with respect to sediment passed
Figure Effect of erosion on pressure around guide vanes
Figure Erosion on Aluminum Guide Vanes
0
2
4
6
8
10
3 9 15 21
% P
ress
ure
Chan
ge
Sediment Passed [kg]
P1
P2
P3
CRHT VII, 2017 Kathmandu University
Investigation though RDA setup
Figure Experimental practice in Rotating Disc Apparatus
Disc speed 458 rpm
Sediment Concentration 66.67 gm/ltr
Particle size 150 – 300 µm
CRHT VII, 2017 Kathmandu University
Investigation though RDA setup
0
0.26
0.52
0.78
1.04
1.3
NACA0012 NACA2412 NACA1412 NACA4412
% W
eig
ht
los
s
Profiles
30 mins 60 mins 90 mins
Figure Selection of Guide Vane Profile for erosion handling
CRHT VII, 2017 Kathmandu University
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
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Kathmandu University
Thank you for your attention!
Contact :
Turbine Testing Lab
www.ku.edu.np
Kathmandu University,
P.O. Box : 6250
Phone : +977-011-661399
