aerodynamics of blade of hawt
TRANSCRIPT
Aerodynamic Of Blade Of HAWT
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Wind
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Importance of Wind Energy
1. A country will become more self-sufficient by using
alternatives such as wind power.
2. No CO₂ emissions
3. Creates jobs
4. Can be used for charging batteries or can be combined
with a diesel engine to save fuel
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Fundamentals of Wind Turbines
• Wind Power: Conversion of wind energy into a useful
form of energy.
ex. wind turbine, wind mills, wind pumps
• Wind turbine: A wind turbine is a device that converts
kinetic energy from the wind into electrical power.
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A Typical HAWT
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Horizontal Axis Turbine
• This is the most common windturbine design. In addition tobeing parallel to the ground, theaxis of blade rotation is parallel tothe wind flow.
• Some machines are designed tooperate in an upwind mode, withthe blades upwind of the tower.
• In this case, a tail vane is usuallyused to keep the blades facing intothe wind. Other designs operate ina downwind mode so that the windpasses the tower before strikingthe blades.
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Horizontal axis wind turbine (HAWT)
• Rotor may be upwind or downwind of the tower.7
• Lift is the main force
• Much lower cyclic stresses
• 95% of the existing turbines are HAWTs
• Nacelle is placed at the top of the tower
• Yaw mechanism is required
HAWT
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Economic Advantages
• Greater fuel diversity
• No delay in construction
• Low maintenance costs
• Reliable and durable equipment
• Additional income to land owners
• More jobs per unit energy produced
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Airfoil Nomenclature
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Airfoil Shape
• Just like the wings of an
airplane, wind turbine blades
use the airfoil shape to create
lift and maximize efficiency.
The Bernoulli Effect
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Drag Force-“When an object place in the wind mill , it
experiences forces on the body. This forces are called as Drag
Forces.”
Lift Forces-“The force created due to pressure difference between
upper and Lower surface of the blade.”
• The forces on lower side is more than that on upper side
• For efficient operation lift must be more than Drag forces.
• The lift to drag ratio should be large for good operation
• Low pressure side of the blade is called as Aerofoil.
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Aerodynamic on Airfoil
Angle of attack-“The angle made between direction of wind and
chord line of the blade is called angle of attack.”
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Low Angle of attack Medium Angle of attack High Angle of attack
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Twist & Taper
• Speed through the air of apoint on the blade changeswith distance from hub.
• Therefore, tip speed ratiovaries as well.
• To optimize angle ofattack all along blade, itmust twist from root to tip.
Fast
Faster
Fastest
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Aerodynamic on Airfoil
p
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i
α
Aerodynamic Forces acting on Airfoil
• Where,
w- relative wind velocity
u- linear velocity or rotational velocity of blade
v- velocity of wind
FL- lift force
FD- drag force
F- total force
α- angle of attack
I – flow angle
i- pitch angle
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Aerodynamic Forces acting on Airfoil
• Consider a cross section of airfoil.
• Wind of velocity v acting on blade at point p as shown in
figure.
• Blade is rotating anticlockwise direction with velocity u.
• Take negative component u in a opposite direction a blade
rotation.
• This velocity component added vectorially to the impinging
wind velocity gives the resulting wind velocity, w.
• At right angle w, is the lift force FL caused by the
aerodynamic shape of the blade.
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Aerodynamic Forces acting on Airfoil
• The drag force, FD is parallel to the w.
• The vector sum of FL and FD gives resultant or total force,
F acting at point P due to wind as shown in figure.
• Now draw the projection line of vector, which states that
the total force acting in the direction of blade rotation.
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