wind turbine blades - an overview
TRANSCRIPT
BladesDesign, Materials and manufacture
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Wind Turbine Blades – An Overview3
Naming and definitions
Leading edge
Trailing edge
root
Tip
Leeward
Torsion/pitch
Flap direction
Edge direction
Profile
chord
Pitch axis/sweep angle
Windward
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Blade Requirements
What do we need from our Blades?• Low weight
– Reduce loads on rest of turbine– Easier to transport and handle
• Stiff– Tower Strike is a ‘design
constraint’– Need to maintain aerodynamic
shape• Strength and Durability
– Avoid Material Failure (extreme loads and fatigue), buckling, performance degradation due to erosion etc.
• Aerodynamic design• Easy to manufacture• Low price
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Loads on the Blade
Rotational speed
Lift
Drag
Bending force
Wind speed
Relative wind speed
Effective driving force
Centre line
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Loads on the Blade
Design Loads are split into 2 sets: • Edgewise • Flapwise Need to consider • Extreme Cases• Fatigue Loads
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Loads on the Blade• Load magnitudes are high.
• For the extreme forward flapwise case it is the same as hanging 2 empty double decker london buses from the tip of the blade!!
• Under this load the blade deflects by about 10m at the tip.
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Structural Concepts
How do we get a light, stiff and strong blade that can withstand the loads for 20 years ?
Efficient arrangement of the best materials.
Pre-Preg Blade
Wood Carbon Blade
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Materials
• Glass fibre (Unidirectional, or woven)
• Carbon fibre (Unidirectional layers or prefabricated rods
• Epoxy • PUR-glue• High density PVC-foam• Wood (balsa, plywood)• Steel and copper
Manufacture of PrePreg Blades
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Sub process Precutting of prepreg
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Supporting carbon spar concept• The supporting spar with a
rectangular section • The airfoil shells with sandwich
construction at the rear
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Prepreg
• PREimPREGnated glass or carbon fibres
• Fibres impregnated with epoxy resin and hardener
• Prepreg is tacky and easy mount• Vacuum is used to remove air and
heat start the hardening process
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Manufacture
Root joint
Main spar Shells Finish
Tip spar Precuttingprepreg
Painting
Main process
Sub process
Start End
Process flow prepreg blade production
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Sub process Tip spar Lay-up on tip spar
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Sub process Curing of tip spar
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Main process Main spar Putting on root joint
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Main process Putting on tip spar
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Main process Lay-up on main spar
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Main process Curing of main spar
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Main process Shells Layout of coat
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Main process Lay-up of prepreg
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Main process Lay-up of PVC
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Main process Vacuum on shells
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Main process Curing of shells / close mould
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Main process Remove support materials
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Main process Layout glue
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Main process Putting main spar into the shells
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Main process Open the mould after curing of glue
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Main process Moving the blade after de-moulding
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Main process Finish Grinding / repair of edges
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Main process Grinding with flatter grinding machine
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Main process Painting of blade
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Blade WeightsBlade length
Weight (approx.)
23 meter 1300 Kg
25 meter 1800 Kg
32 meter 3600 Kg
39 meter 6500 Kg
44 meter 6300 Kg
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Wood carbon concept• ‘Sandwich’ Construction to provide extra flexural stiffness• Carbon pultrusions provide extra ‘global’ stiffness• Glass along TE provides stiffness for edgewise loads.
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Wood Carbon ManufactureLay Materials into Blade
halves (Leeward/Windward
Vacuum Assisted Resin infusion
Cure Cycle
‘Debagging’
Join Up
Breakout
Finishing
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