POLI di MI tecnico lano tecnico lano MULTI-DISCIPLINARY CONSTRAINED OPTIMIZATION OF WIND TURBINES C.L. Bottasso, F. Campagnolo, A. Croce Politecnico di Milano, Italy EWEC 2010 Warsaw, Poland, April 20-23, 2010
Dec 19, 2015
PO
LI
di M
Itecn
ico
lano
tecn
ico
lanoMULTI-DISCIPLINARY
CONSTRAINED OPTIMIZATION OF WIND
TURBINES
C.L. Bottasso, F. Campagnolo, A. CrocePolitecnico di Milano, Italy
EWEC 2010 Warsaw, Poland, April 20-23, 2010
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POLITECNICO di MILANO Poli-Wind Research Lab
POLITECNICO di MILANO Poli-Wind Research Lab
OutlineOutline
• Introduction and motivation
• Approach:
- Constrained multi-disciplinary optimization
- Simulation models
- Aerodynamic optimization
- Structural optimization
- Combined aero-structural optimization
• Applications and results
• Conclusions and outlook
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POLITECNICO di MILANO Poli-Wind Research Lab
POLITECNICO di MILANO Poli-Wind Research Lab
Introduction and MotivationIntroduction and MotivationFocus of present work: integrated multi-disciplinary (holistic)
constrained design of wind turbines, i.e. optimal coupled sizing of:• Aerodynamic shape • Structural members (loads, aero-servo-elasticity and controls)
Constraints: ensure a viable design by enforcing all necessary design requirements
Applications:• Sizing of a new machine• Improvement of a tentative configuration• Trade-off studies (e.g. performance-cost)• Modifications to exiting models
Previous work: Duineveld, Wind Turbine Blade Workshop 2008; Fuglsang &
Madsen, JWEIA 1999; Fuglsang, EWEC 2008; etc.
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POLITECNICO di MILANO Poli-Wind Research Lab
POLITECNICO di MILANO Poli-Wind Research Lab
OutlineOutline
• Introduction and motivation
• Approach:
- Constrained multi-disciplinary optimization
- Simulation models
- Aerodynamic optimization
- Structural optimization
- Combined aero-structural optimization
• Applications and results
• Conclusions and outlook
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POLITECNICO di MILANO Poli-Wind Research Lab
POLITECNICO di MILANO Poli-Wind Research Lab
Optimizer • Local/global solvers (SQP, GA)• Functional approximators
ApproachApproach
1. Aerodynamic Optimization
2. Structural Optimization
3. Combined Aero-Structural Optimization
Cp-Lambda aero-servo-elastic multibody simulator
ANBA cross sectional analyzer
Parameters
Cost function & constraints
Aerodynamic parameters: chord, twist, airfoils
Structural parameters: thickness of shell and spar caps, width and location of shear webs
Macro parameters: rotor radius, max chord, tapering, …
Partition of optimization parameters: aerodynamic, structural, macro (i.e. combined aero-structural)
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POLITECNICO di MILANO Poli-Wind Research Lab
POLITECNICO di MILANO Poli-Wind Research Lab
Aerodynamic Optimization
1. Compute Cp-TSR curves
2. Compute AEP
3. Compute constraints
4. Converged blade design?
5. Update rotor model
Constraints: • Noise constraint (V tip):
regulation in region II1/2• Torque-TSR stability• Max chord• …
Blade parameterization: Chord and twist shape functions deform a baseline configuration
Richer shape with fewer dofs
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POLITECNICO di MILANO Poli-Wind Research Lab
POLITECNICO di MILANO Poli-Wind Research Lab
Cp-Lambda (Code for Performance, Loads, Aero-elasticity by Multi-Body Dynamic Analysis):• Global aero-servo-elastic FEM model
• Rigid body
• Geometrically exact beam
• Revolute joint
• Flexible joint
• Actuator
ANBA (Anisotropic Beam Analysis) cross sectional model:• Evaluation of cross sectional stiffness
(6 by 6 fully populated) • Recovery of sectional stresses and
strains
Compute cross sectional stresses and
strains
Compute sectional stiffness of equivalent
beam model
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POLITECNICO di MILANO Poli-Wind Research Lab
POLITECNICO di MILANO Poli-Wind Research Lab
Structural Optimization
1. Control synthesis
2. Cp-Lambda
multibody analysis
3. ANBA cross
sectional analysis
4. Converged blade
design?
5. Update models
Analyses: • Transfer loads from
multibody to cross sectional models
• Recover sectional stresses and strains
Compute cost function: • Weight
Compute constraints: • Stress/strains safety
margins
Analyses: • DLCs (IEC61400:
load envelope, fatigue DELs)
• Eigenfrequencies (Campbell diagram)
• Stability
Compute constraints: • Max tip deflection• Frequency
placement
Modeling:• Extract reduced model
from multibody one• Linearize reduced model
Synthesize controller: • Compute LQR gains
Update process:
Update cross sectional models
Compute beam stiffness and
inertial properties
Update multibody model
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POLITECNICO di MILANO Poli-Wind Research Lab
POLITECNICO di MILANO Poli-Wind Research Lab
Structural Blade ModelingStructural Blade Modeling
Maximum chord line
Straight websCaps extend to
embrace full root circle
Cross section types
Sectional structural dofs
Twisted shear webs
Location of structural dofs and load computation section
Load computation section
Spanwise shape functions
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POLITECNICO di MILANO Poli-Wind Research Lab
POLITECNICO di MILANO Poli-Wind Research Lab
Combined Aero-Structural Optimization
1. Family of optimal
aerodynamic designs
2.Associated family
of structurally optimal designs
3.Define combined
cost
4.Compute optimum
Parameter: radius, max chord, etc.Example: tapering
Example: spar cap thicknessExample: AEP over weight
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POLITECNICO di MILANO Poli-Wind Research Lab
POLITECNICO di MILANO Poli-Wind Research Lab
OutlineOutline
• Introduction and motivation
• Approach:
- Constrained multi-disciplinary optimization
- Simulation models
- Aerodynamic optimization
- Structural optimization
- Combined aero-structural optimization
• Applications and results
• Conclusions and outlook
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POLITECNICO di MILANO Poli-Wind Research Lab
POLITECNICO di MILANO Poli-Wind Research Lab
Parameter: blade tapering, constrained max chord
Optimization of a 3 MW Wind Turbine
Optimization of a 3 MW Wind Turbine
1. Aerodynamic Optimization
2. Structural Optimization3. Combined Aero-Structural Optimization
Long blade span (D=106.4m) and small maximum chord (3.9m) is penalized by excessive outboard chords(lower flap frequency/increased tip deflections)Optimal solution: intermediate taper
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POLITECNICO di MILANO Poli-Wind Research Lab
POLITECNICO di MILANO Poli-Wind Research Lab
WT2, the Wind Turbine in a Wind Tunnel
WT2, the Wind Turbine in a Wind Tunnel
Civil-Aeronautical Wind Tunnel - Politecnico di MilanoIndividual blade
pitch
Torque control
Aero-elastically scaled wind turbine model for:
• Testing and comparison of advanced control laws and supporting technologies
• Testing of extreme operating conditions
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POLITECNICO di MILANO Poli-Wind Research Lab
POLITECNICO di MILANO Poli-Wind Research Lab
Structuraloptimization
Design of an Aero-elastically Scaled Composite Blade
WidthChordwise Position
Thickness
Sectional optimization variables (position, width, thickness)Span-wise shape function interpolation
Optimization
Cross sectional analysis
Equivalent beam model
ANBA (ANisotropic Beam Analysis) FEM cross sectional model:• Evaluation of cross sectional
stiffness (6 by 6 fully populated matrix)
Objective: size spars (width, chordwise position & thickness) for desired sectional stiffness within mass budgetCost function: sectional stiffness error wrt target (scaled stiffness)Constraints: lowest 3 frequencies
Rohacell core with grooves for the housing of carbon fiber spars
Thermo-retractable film
Carbon fiber spars for desired stiffness
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POLITECNICO di MILANO Poli-Wind Research Lab
POLITECNICO di MILANO Poli-Wind Research Lab
Design of an Aero-elastically Scaled Composite Blade
Filippo Campagnolo
Modes Reference [Hz]Optimization
procedure [Hz]
1st Flap-wise
23.2 23.1
2nd Flap-wise
59.4 59.1
1st Edge-wise
33.1 33.1
Mass gap can be corrected with weights
Solid line: scaled reference values
Dash-dotted line: optimal sizing
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POLITECNICO di MILANO Poli-Wind Research Lab
POLITECNICO di MILANO Poli-Wind Research Lab
ConclusionsConclusionsPresented holistic optimization procedures for wind turbines:
• Refined models: aero-servo-elastic multibody + FEM cross sectional analysis can account for complex effects and couplings from the very inception of the design process (no a-posteriori fixes)
• Fully automated: no manual intervention, including self-tuning model-based controller that adjusts to changes in the design
• Fast design loop: can perform a full design in 1-2 days on standard desktop computing hardware
• General and expandable: can readily add constraints to include further design requirements
• Ready-to-use multibody aero-servo-elastic model of final design: available for further analyses/verifications, evaluation of loads for design of sub-components, etc.
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POLITECNICO di MILANO Poli-Wind Research Lab
POLITECNICO di MILANO Poli-Wind Research Lab
OutlookOutlook
Real-life applications:
• Completed design of 45m blade (to be manufactured end 2010)
• Design of 16.5m blade under development
Software enhancements:
• Improved speed: parallelization of analyses (DLCs, Campbell, FEM cross sectional analyses, etc.)
• Improved coupling between aerodynamic and structural optimizations
• Automated generation of CAD model (mould manufacture, FEM analysis)
• Automated generation of 3D FEM model for detailed verification (stress & strains, buckling, max tip deflection, fatigue, etc.)