Jarred Morales and Cody Beckemeyer Advisior: Dr. Junkun Ma ET 483

Introduction With a constant increase in energy usage in this world an alternative method of generating power other than fossil fuel is needed Wind turbines use the kinetic energy of the wind and convert it to mechanical energy Vertical axis wind turbines (VAWTs) are easy to be installed and are easy to be used by individuals

Trailing Edge Flap

Comparison to HAWT VAWT can be placed independently of wind direction, perfect for places that the wind changes daily Gearbox and generator are able to be placed near the ground, so they are easier to be maintained than HAWT VAWT have lower rotational speed and lower tip speed ratio therefore higher torque is involved HAWT have higher tip speed ratio and coefficient of performance Cp, but have lower torque VAWT have either low or insignificant starting torque so the rotor must be brought up to speed by either a small generator as a motor or a small secondary rotor

NACA0012 Airfoil

Top View Individual pitching of each blade Flaps can be regulated Using camber and pitch controls or local actuators helps create a greater force differential across the turbine This also allows operation over wide range of wind speeds and improves tolerance to wind variation

Angle of Attack α - It is the angle between the chord line of the blade and the relative wind or the direction of the air flow -changes due to the variation of the relative velocity - both the speed of the blade and the speed of the wind affect this angle

Angle of Attack

Equal pressure distribution

Lift and Drag - The induced velocity (Vi) and the rotating velocity ωr of the blade determine the orientation and magnitude of the relative velocity - This changes the Lift(L) and drag forces(D) - D acts in the direction of W and the lift acts perpendicular to W - As both the magnitude and orientation change the resultant force Fr changes - The resultant force is composed of both normal component Fn and tangential component Ft - Ft drives the rotation of the wind turbine and produces the torque

Lift and Drag coefficients

Tip speed ratio (TSR) λ = ΩR/Vwind, where R is the radius of the blades, Vwind is the wind velocity, and Ω is the angular velocity λ is greater than 1 means that the blades can travel faster than the speed of the wind Maximum power extraction can be found by finding the time taken to reestablish the disturbed wind for the next blade to move into location of the preceding blade

optimal rotational frequency Ts= 2(π)/n(ω) Tw=s/v Ω is the rotational frequency of the rotor S- length of the disturbed wind N-number of blades V-wind speed ts > tw, some wind is unaffected. If tw > ts, some wind is not allowed to flow through the rotor. The maximum power extraction occurs when the two times are approximately equal

Attack angle at 15˚