Design of Airfoils for Wind Turbine Blades

31 Pages·2004·1.16 MB·English

Design of Airfoils
for Wind Turbine Blades
Ruud van Rooij
([email protected])
Nando Timmer
Delft University of Technology
The Netherlands
03 May, 2004 DUWIND, section Wind Energy, Faculty CiTG 1
Delft University of Technology
13200 Bsc+ Msc students, 4750 employees
Delft University Wind Energy Research
Institute
(Coordinator: Section Wind Energy)
Faculties:
• Civil Engineering and Geosciences
(Wind Energy, Offshore)
http://www.windenergy.citg.tudelft.nl/home/flash/index.html
• Information Technology and Systems
(Electrical group)
• Design, Engineering and Production
(Systems &Control)
• Aerospace Engineering
(Aero, Aeroelastics)
03 May, 2004 DUWIND, section Wind Energy, Faculty CiTG 2
Section Wind Energy
(Civil Engineering and Geosciences => Aerospace Engineering)
Aerodynamic research
- Facilities
low speed
wind-tunnel
open-jet
research wind turbine
wind tunnel
03 May, 2004 DUWIND, section Wind Energy, Faculty CiTG 3
Contents
• Background
• Design goals HAWT airfoils
• Design approach
• Performance comparison
• Airfoil testing
• Effect on wind turbine power Cp
• Overview HAWT airfoils
03 May, 2004 DUWIND, section Wind Energy, Faculty CiTG 4
Background
Operational area
Control: Variable RPM Power restriction
1.2
High Cp
Power
80% of Energy
1.0
0.8
0.6
0.4
0.2
Winds speed (m/s)
0.0
0.0 5.0 10.0 15.0 20.0 25.0
Airfoil: High max. L/D Max. lift considerations
03 May, 2004 DUWIND, section Wind Energy, Faculty CiTG 5
Background
Blade geometry
Structural: Airfoil:
Outboard: t/= .15-18 - High max. L/D
- Insensitive to
roughness
Mid span: t/= .25 - Similar design
angle
Inboard: t/> .30 - High max. lift
(Rot. Effects)
No Aerodynamic
Transition piece
demands
03 May, 2004 DUWIND, section Wind Energy, Faculty CiTG 6
Background
Effect of rotation
Stall delay
2.50
RFOIL code
cl inboard
2.00
• Integral boundary layer eq.
mid-span
1.50
• Extended for radial flow
2d
• Radial equations
• Cross flow profile 1.00
0.50
DU 91-W2-250
Re = 3.0x10e6
0.00
parameter is c/r
(= local solidity) Angle (deg.)
-0.50
-5.0 0.0 5.0 10.0 15.0 20.0 25.0
03 May, 2004 DUWIND, section Wind Energy, Faculty CiTG 7
Design goals HAWT airfoils
steady
Thickness-to-chord ratio > .28 .28 - .21 .21 >
High maximum lift-to-drag ratio
Low max. and benign post stall
Insensitivity to roughness
Low noise
Geometric compatibility
Structural demands
03 May, 2004 DUWIND, section Wind Energy, Faculty CiTG 8
Design approach
(example DU 91-W2-250)
Main features
Small upper surface thickness
=> reduced roughness sensitivity
NACA 63-425
S-Tail
DU 91-W2-250 => Aft-loading
03 May, 2004 DUWIND, section Wind Energy, Faculty CiTG 9
Design approach
(pressure distributions DU 91-W2-250, Re = 3.0x106)
- 4. 0
Low roughness sensitivity
Cp
=> Transition at nose for Cl_max
- 3. 0
11.0o Low drag
=> Aft transition at Cl_design
- 2. 0
7.0o
Transition
Alpha= 0.0o
Separation
- 1. 0
0. 0
Aft-loading
1. 0
0.0 0.2 0.4 0.6 x/c 0.8 1.0
03 May, 2004 DUWIND, section Wind Energy, Faculty CiTG 10