Active Aerodynamic Load Control for Wind Turbine Blades
Active Aerodynamic Load Control for Wind Turbine Blades
Jose R. Zayas
Sandia National Laboratories
&
C.P. van Dam, R. Chow, J.P. Baker, E.A. Mayda
University of California - Davis
Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company,for the United States Department of Energy under contract DE-AC04-94AL85000.
March 01, 2006 EWEC 2006 – Aerodynamics, Aero-Elasticity, Aero-Acoustics, Loads
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OutlineOutline
Problem Statement and Goal Active Control Background Microtab Motivation
CFD work Wind tunnel results
Modeling & Tools Future Work Conclusion
March 01, 2006 EWEC 2006 – Aerodynamics, Aero-Elasticity, Aero-Acoustics, Loads
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Problem Statement & GoalProblem Statement & Goal
With Wind Turbines Blades Getting larger and Heavier, Can the Rotor Weight be Reduced by Adding Active Devices?
Can Active Control be Used to Reduce Fatigue Loads?
Can Energy Capture in Low Wind Conditions be Improved?
Research Goal:Understand the Implications and Benefits of Embedded Active Blade Control, Used to Alleviate High Frequency Dynamics
March 01, 2006 EWEC 2006 – Aerodynamics, Aero-Elasticity, Aero-Acoustics, Loads
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Active Flow/Load ControlActive Flow/Load Control
• Blade Load Variations Due to Wind Gusts, Direction Changes, and Large Scale Turbulence
• Active Load Control on Blade/Turbine can be Achieved by Modifying:– Blade incidence angle (pitch)
– Flow velocity (modification in RPM)
– Blade length
– Blade aerodynamic characteristics through:• Changes in section shape (aileron, smart materials, microtab)
• Surface blowing/suction
• Other flow control techniques (VG’s, surface heating, plasma)
α
CL
α
CL
March 01, 2006 EWEC 2006 – Aerodynamics, Aero-Elasticity, Aero-Acoustics, Loads
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Active Flow/Load ControlActive Flow/Load Control
• Active Load Control:– May remove fundamental design constraints– These large benefits are feasible if active control technology is
considered from the onset– May allow for lighter more slender blades designs
• Active Load Control has Already been Implemented in Wind Turbine Design. e.g.:– Yaw control– Blade pitch control– Blade aileron (Zond 750)
March 01, 2006 EWEC 2006 – Aerodynamics, Aero-Elasticity, Aero-Acoustics, Loads
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Active Flow/Load ControlActive Flow/Load Control
Microtab Concept being ProposedActive Aileron on a Zond 750 Blade
Courtesy: NREL
March 01, 2006 EWEC 2006 – Aerodynamics, Aero-Elasticity, Aero-Acoustics, Loads
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Gurney Flap (Passive)Gurney Flap (Passive)
• Gurney Flap (Liebeck, 1978)– Significant increases in CL
– Relatively small increases in CD
– Properly sized Gurney flaps increases in L/D
March 01, 2006 EWEC 2006 – Aerodynamics, Aero-Elasticity, Aero-Acoustics, Loads
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Microtab ConceptMicrotab Concept
Evolutionary Development of Gurney flap
Tab Near Trailing Edge Deploys Normal to Surface
Deployment Height on the Order of the Boundary Layer Thickness
Effectively Changes Sectional Camber and Modifies Trailing Edge Flow Development (so-called Kutta condition)
March 01, 2006 EWEC 2006 – Aerodynamics, Aero-Elasticity, Aero-Acoustics, Loads
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Microtab ConceptMicrotab Concept
Small, Simple, Fast Response Retractable and Controllable Lightweight, Inexpensive Two-Position “ON-OFF” Actuation Low Power Consumption No Hinge Moments Expansion Possibilities (scalability) Do Not Require Significant Changes to Conventional Lifting
Surface Design (i.e., manufacturing or materials)
March 01, 2006 EWEC 2006 – Aerodynamics, Aero-Elasticity, Aero-Acoustics, Loads
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Microtab Research ApproachMicrotab Research Approach
Wind-Tunnel Based Physical Simulations: Pro’s
Proof that concept works as “advertised” Con’s
Requires extensive experimental resources Can be expensive and time consuming Limited to modest chord Reynolds numbers
CFD-Based Numerical Simulations: Pro’s
Relatively fast and inexpensive to study a large number of geometric variations Provides detailed insight to the flow-field phenomena
Con’s Requires extensive computational resources (software & hardware) Learning curve for CFD is steep
March 01, 2006 EWEC 2006 – Aerodynamics, Aero-Elasticity, Aero-Acoustics, Loads
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Microtab Research ApproachMicrotab Research Approach
Current Study uses a Closely-Coupled Collaboration Between Computational Fluid Dynamics (CFD) and Wind Tunnel Experimentation
Wind Turbine Dynamic Simulation Pro’s
Gives understanding on the effects to the entire system Cost effective in comparison to field testing Mature codes
Con’s Difficult to capture all of the physics in the model Requires insight and careful validation of the results
Final Goal is to Fly an Effective, Robust Active Load Control System on a Wind Turbine
March 01, 2006 EWEC 2006 – Aerodynamics, Aero-Elasticity, Aero-Acoustics, Loads
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CFD MethodsCFD Methods
ARC2D Compressible 2D RANS One-equation Spalart-
Allmaras turbulence model
OVERFLOW 2.0y Compressible 3D RANS Structured Chimera overset
grids Multiple turbulence models
Spalart-Allmaras Menter’s k- SST model
March 01, 2006 EWEC 2006 – Aerodynamics, Aero-Elasticity, Aero-Acoustics, Loads
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CFD MethodsCFD Methods
Grid Generation Chimera Grid Tools 1.9 Structured O- and C-type grids 350 to 400 surface grid points y+ < 1.0 for all viscous surfaces
March 01, 2006 EWEC 2006 – Aerodynamics, Aero-Elasticity, Aero-Acoustics, Loads
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Wind Tunnel MethodsWind Tunnel Methods
Open Circuit, Low Subsonic Test Section Dimensions
Cross section: 0.86 m 1.22 m (2.8 ft 4.0 ft) Length: 3.66 m (12 ft)
Low Turbulence < 0.1% FS for 80% of test section
March 01, 2006 EWEC 2006 – Aerodynamics, Aero-Elasticity, Aero-Acoustics, Loads
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Wind Tunnel MethodsWind Tunnel Methods
Force Measurement Lift and moment
determined using 6-component pyramidal balance
Drag determined using wake measurements Pitot-static probe
measurements Based on Jones’
Method
March 01, 2006 EWEC 2006 – Aerodynamics, Aero-Elasticity, Aero-Acoustics, Loads
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Wind Tunnel -vs- CFDWind Tunnel -vs- CFD
Results Repeatedly Show Excellent Agreement Between Computations and Experiment
S809 Baseline Airfoil
1.1% chord tab
95% x/c lower surface
Re = 1×106
Ma = 0.17
March 01, 2006 EWEC 2006 – Aerodynamics, Aero-Elasticity, Aero-Acoustics, Loads
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Full System Modeling - Background
Full System Modeling - Background
Wind Turbine Model Micon 65 Stall Regulated 3-bladed upwind Model results have been verified with field data
Dynamic Simulation Tools NuMAD (Numerical Manufacturing and Design Tool)
ANSYS FEA preprocessor Blade property extraction tool (BPE)
FAST (Fatigue, Aerodynamics, Structures, and Turbulence) Modal representation Limited degrees of freedom Used as a preprocessor to ADAMS
ADAMS (Automatic Dynamic Analysis of Mechanical Systems) Commercial multi body dynamic simulation software Virtually unlimited degrees of freedom
Micon 65 – ADAMS Model
NuMAD FEA Model
March 01, 2006 EWEC 2006 – Aerodynamics, Aero-Elasticity, Aero-Acoustics, Loads
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FAST –vs- ADAMSFAST –vs- ADAMS
Power vs. Wind Speed
0
20
40
60
80
100
120
3.0 8.0 13.0 18.0
Wind Speed (m/s)
Pow
er (k
W)
FAST
ADAMS
Edgewise moment vs. Wind Speed
-5
-3
-1
1
3
5
7
9
4 9 14 19
Wind Speed (m/s) m
omen
t (kN
m)
FASTADAMS
Codes Provide Virtually Identical Results
March 01, 2006 EWEC 2006 – Aerodynamics, Aero-Elasticity, Aero-Acoustics, Loads
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Determining Blade SolidityDetermining Blade Solidity
Outboard Portion of the Blades is Analyzed
Percent Reduction in Flapwise Bending Moments
0%
4%
8%
12%
16%
6 7 8 9 10 11 12
Wind Speed (m/s)
% r
ed
uc
tio
n
9% spanwise tab17% spanwise tab28% spanwise tab37% spanwise tab48% spanwise tab
March 01, 2006 EWEC 2006 – Aerodynamics, Aero-Elasticity, Aero-Acoustics, Loads
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Dynamic Effect of Microtabs(no control)
Dynamic Effect of Microtabs(no control)
Rotor Power
22
24
26
28
30
32
34
35.0 36.0 37.0 38.0 39.0 40.0
Time (sec)
Pow
er (K
W)
Baseline
Tabs
Flapwise Moment
12.0
13.0
14.0
15.0
16.0
17.0
18.0
25.0 27.0 29.0 31.0 33.0 35.0
Time (sec)M
omen
t (K
N m
)
Baseline
Tabs
Microtabs Deployed for the Entire Simulation
March 01, 2006 EWEC 2006 – Aerodynamics, Aero-Elasticity, Aero-Acoustics, Loads
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Controlled Microtab ResultsControlled Microtab Results
Flapwise Moment
10
12
14
16
18
20
22
6.0 16.0 26.0 36.0 46.0 56.0
Time (sec)
Mo
men
t (K
N m
)
BaselineDelta=10/tabs
Microtabs Response Using Simple Controller
March 01, 2006 EWEC 2006 – Aerodynamics, Aero-Elasticity, Aero-Acoustics, Loads
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Future WorkFuture Work
Develop and Analyze Active Control Microtab Airfoil Model for the Wind Tunnel Testing
Quantify Potential Benefits of Microtabs for Increase Energy Capture
Analyze other Potential Devices (flaps, spoilers,…) Model Devices on a Variable Speed / Variable Pitch
Machine (in progress) Develop a MATLAB Simulink Controller for Active Devices
March 01, 2006 EWEC 2006 – Aerodynamics, Aero-Elasticity, Aero-Acoustics, Loads
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ConclusionConclusion
Potential Advantages of Active Control have been Investigated
Microtab Analysis has been Quantified both Computationally and Experimentally
Potential Microtab Benefits have been Demonstrated on a Full System Model
Active Devices may Provide Substantial Benefit for Future Wind Turbine Designs
March 01, 2006 EWEC 2006 – Aerodynamics, Aero-Elasticity, Aero-Acoustics, Loads
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Thank You!!Thank You!!