Development of a Vortex Method for Simulating Vertical ...
Transcript of Development of a Vortex Method for Simulating Vertical ...
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NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.
Dr. Ye Li
1st NREL MHK Device Modeling Meeting
March 1, 2011
Innovation for Our Energy Future
Development of a Vortex Method for Simulating
Vertical Axis Tidal Current Turbines
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Outline
• Introduction
• Turbine Modeling Method Li and Calisal, Journal of Offshore Mechanics & Arctic Engineering,
2010,132(3), 1102-1110
Li and Calisal, Renewable Energy, 2010, 35(10), 2325-2334
• Twin-Turbine System Study Li and Calisal, Ocean Engineering,2010 ,37(7),627-637
Li and Calisal, Ocean Engineering,2011, 38(4),550-558
• Conclusions
• Future Direction
National Renewable Energy Laboratory Innovation for Our Energy Future
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Objective and Motivation of the Research
• Why Vertical Axis Turbine?
Omni directional
Power conversion system close to free surface
Environmentally-friendly
Good for shallow water area
Outline
Introduction
Method
System Study
Conclusion
Future Direction
National Renewable Energy Laboratory Innovation for Our Energy Future
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• Theory
Time domain potential flow theory, with discrete
Lamb vortices decaying in time based on Reynolds
number with respect to the blade chord
• Assumptions
Shaft and arm effects are not simulated
No bottom and free surface
2D foil properties remain valid for lift and drag for
the proper angle of attack calculated by the induced
velocities
3D effects are simulated by treating a blade as
multi-elements
A Potential Flow Based Discrete Vortex Method Outline
Introduction
Method
Modeling
1-2-3-4
Validation
System Study
Conclusion
Future Direction
National Renewable Energy Laboratory Innovation for Our Energy Future
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Turbine Working Principles Outline
Introduction
Method
Modeling
1-2-3-4
Validation
System Study
Conclusion
Future DirectionR iU U U R
21
2L RL C cU
, 34iP l
l
r d lU
r
R BL U 1
2B L RC cU
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Blade and WakeOutline
Introduction
Method
Modeling
1-2-3-4
Validation
System Study
Conclusion
Future Direction
, 1, , 1, , ,S i j B i j B i j
, 1, , , , , 1T i j B i j B i j
National Renewable Energy Laboratory Innovation for Our Energy Future
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Wake Vortices
• Nascent Vortex
• Vortex Decay
• Lamb Vortices
2
1 c
r
re
V rr
cr t
0 1dK
j e
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V m V mt tt t
U U
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V m iP mt tU U U
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1
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V mtV m t tt t
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Outline
Introduction
Method
Modeling
1-2-3-4
Validation
System Study
Conclusion
Future Direction
National Renewable Energy Laboratory Innovation for Our Energy Future
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Turbine Design
Parameters Values
Number of blades 3
Blades type NACA 63(4)-021
Solidity 0.435
Turbine height 0.5m
Turbine diameter 0.91m
Tip speed ratio RU
power coefficient 31
2
PPCAU
Solidity NcR
Outline
Introduction
Method
Modeling
1-2-3-4
Validation
1-2-3
System Study
Conclusion
Future Direction
National Renewable Energy Laboratory Innovation for Our Energy Future
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Towing Tank TestOutline
Introduction
Method
Modeling
1-2-3-4
Validation
1-2-3
System Study
Conclusion
Future Direction
National Renewable Energy Laboratory Innovation for Our Energy Future
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ValidationOutline
Introduction
Method
Modeling
1-2-3-4
Validation
1-2-3
System Study
Conclusion
Future Direction
National Renewable Energy Laboratory Innovation for Our Energy Future
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Definition of the Twin-turbine SystemOutline
Introduction
Method
System Study
General
1-2
Power
Torque
Noise
Conclusion
Future Direction 2 2T T SP P
2 1 2TP P P
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Twin-Turbine TestOutline
Introduction
Method
System Study
General
1-2
Power
Torque
Noise
Conclusion
Future Direction
National Renewable Energy Laboratory Innovation for Our Energy Future
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Twin-Turbine Validation
Outline
Introduction
Method
System Study
General
1-2
Power
1-2
Torque
Noise
Conclusion
Future Direction
Side-by-Side Relative distance=3.5
Counter-rotating
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Power Analysis
Counter-rotating Co-Rotating
Blade Profile NACA0015
TSR=4.75
(Increase 25%)Outline
Introduction
Method
System Study
General
1-2
Power
1-2
Torque
Noise
Conclusion
Future Direction
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Torque Fluctuation AnalysisOutline
Introduction
Method
System Study
General
1-2
Power
1-2
Torque
1-2
Noise
Conclusion
Future Direction
TSR=4.75
46
peakTF
peak
PSMC dB
f
Torque Fluctuation Coefficient
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,
,
TF TwinRTF
TF S
CC
C
Definition of the Relative Torque Fluctuation Coefficient:
Relative Torque Fluctuation CoefficientOutline
Introduction
Method
System Study
General
1-2
Power
1-2
Torque
1-2
Noise
Conclusion
Future Direction
Counter-rotating Co-rotating
TSR=4.75
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Noise Emission
• Noise Sources Mechanical
Hydrodynamics• Shaft
• Blade tip
• Wake Fluctuation
• Cavitation
• Others
• Assumptions The sound generated by the turbine is a plane
sound wave
Ocean is a free acoustic field without reflecting
boundaries and with a homogenous sound velocity
The velocity fluctuation is fully induced by the vortex shedding effect and the induced velocity caused by the rotation of the turbine
I pu
p Zu
Z c
2I cu
Outline
Introduction
Method
System Study
General
1-2
Power
1-2
Torque
1-2
Noise
1-2-3
Conclusion
Future Direction
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Noise Emission Intensity Analysis (Reduce 10dB)
Outline
Introduction
Method
System Study
General
1-2
Power
1-2
Torque
1-2
Noise
1-2-3
Conclusion
Future Direction
National Renewable Energy Laboratory Innovation for Our Energy Future
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Marine Animal Communication Frequency
Names Frequency (Hz)
American eel 75
Atlantic herring 30 -1,200
Bar jack 30
Bigeye mojarra 75-1,000
Bluefish 60-1,200
Coney 75
Cownose ray 150
Pinnipeds 50-60,000
Toothed Whale 10-10,000
Outline
Introduction
Method
System Study
General
1-2
Power
1-2
Torque
1-2
Noise
1-2-3
Conclusion
Future Direction
National Renewable Energy Laboratory Innovation for Our Energy Future
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Conclusions-Method
• A potential flow based numerical method for simulating tidal current turbines is developed
The numerical method can simulate the behavior of tidal current turbines with a good accuracy
This method can be used for predicting not only power output but also other turbine characteristics such as torque fluctuation and noise emission
The 2-D model can be used for preliminary assessment
Outline
Introduction
Method
System Study
Conclusion
1-2
Future Direction
National Renewable Energy Laboratory Innovation for Our Energy Future
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Conclusions –System Analysis
• An optimal configuration of twin-turbine
system can significantly increase turbine
performance
The power output of a twin-turbine system with an
optimal layout can be 25% higher than the power
output of two turbines far apart
The noise intensity of a twin-turbine system with
an optimal layout can be 10dB lower than the
noise intensity of two turbines far apart
The torque of a twin-turbine system with an
optimal layout fluctuates much less than torque of
two turbines far apart
Outline
Introduction
Method
System Study
Conclusion
1-2
Future Direction
National Renewable Energy Laboratory Innovation for Our Energy Future
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Future Direction
• Hydrodynamics
Free surface
Dynamic stall
Added mass and damping coefficient
• Optimization
Blade curvature
Pitch angle
• Others
Cost
Comprehensive
Outline
Introduction
Method
System Study
Conclusion
Future Direction
National Renewable Energy Laboratory Innovation for Our Energy Future
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Acknowledgements
• Colleagues at the University of British Columbia
• Colleagues at the National Renewable Energy
Laboratory
• Funding Agencies:
John Davies Foundation
Dieter Family Foundation
National Renewable Energy Laboratory Innovation for Our Energy Future
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Thank you!
Q&A