MESA Wind Energy Challenge A Multi-Task Windmill

1. MESA Wind Energy ChallengeA Multi-Task Windmill November 2009 Tom Milnes JHU/APL & AIAA Baltimore Section Paul Wiedorn Wilde Lake HS & TEAM

2. AIAA Baltimore Section Support • Major Supporter of Maryland MESA • Judges for National Competition and MESA Days • Members of National Competition Committee • Up, Up, and Away Workshop • Workshops on MESA Aerospace Challenges • Classroom Visits • Career Workshops at BEYA Event • Funding for Classroom Projects • RC Airplane Program Pilot

3. AIAA Support for K-12 Educators • AIAA Grant Program • $200 per teacher, up to $1000 per school for K-12 Classroom projects related to Aerospace • Steps • Join AIAA for Free as an Educator Associate • https://www.aiaa.org/content.cfm?pageid=208 • Submit Online Application • https://www.aiaa.org/content.cfm?pageid=216 • Must conform to guidelines, Principal approval needed • https://www.aiaa.org/content.cfm?pageid=244

4. Motion • An objects motion is fully described by translation of its Center of Mass and rotation about its Center of Mass (CM)

5. Motion Continued • Translation Can Occur in 3 Dimensions • Rotation Can Occur in 3 Dimensions • Full Description of Motion is referred to as 6 Degrees of Freedom (6-DOF)

6. Forces and Motion • Forces Acting through CM only causes translation • Forces acting a distance from CM will cause rotation (torque ) r • = rF • F=ma •  = I F F

7. Multi-Task Windmill Competition • Middle and High School • LIFTING TEST - Greatest Average Power • mgh / t (g=9.8 m/s, h = .75 m) • WIND TO VEHICLE - Greatest Kinetic Energy Transferred to Vehicle over 250 cm course • ½ mv2 v = 250 cm / t (Vehicle mass  200g) • High School Only • ELECTRICAL POWER - Greatest average power with 60 change in direction • V1A1+ V2A2 = Average Power

8. Energy • Energy is required to do Work • Work is done when an object is moved a distance against a force • Lift a 1 kg mass 1 m against gravity • Force = mg = 1 kg x 9.8 m/s2 = 9.8 Newtons • Work = Force x Distance = 9.8 N-m = 9.8 Joules • Work = mgh = Energy • Not Surprisingly an object h meters off ground has Gravitational Energy = mgh • If dropped will convert to kinetic energy • Kinetic Energy on Ground = ½ mv2 = mgh

9. 1 kg g = 9.8 m/s2 F = 9.8 N

10. Work = Fh = Energy = 9.8 Joules 1 kg h = 1 m g = 9.8 m/s2 F = 9.8 N

11. Rotational Work • Its takes energy to rotate an object against a torque • Work = Energy =  •   F, h  

12. Power • Power is Required to Work Quickly • Power = Energy / Time • Power is required to sustain a velocity against a force • If we want to raise the rock at 1 m/s then • Power = Force x Velocity = Fv = mgv = 9.8 N-m/s = 9.8 Joules/s = 9.8 Watts • Rotational Power • Power is required to sustain an angular velocity against a torque • Power = Torque x Angular Velocity, P=

13. 1 kg g = 9.8 m/s2 F = 9.8 N

14. 1 kg g = 9.8 m/s2 F = 9.8 N

15. 1 kg g = 9.8 m/s2 F = 9.8 N

16. 1 kg g = 9.8 m/s2 F = 9.8 N

17. 1 kg Power = Fv = Energy/s = 9.8 Watts 1 m/s g = 9.8 m/s2 F = 9.8 N

18. Power – Rotating Shaft to Move a Mass P =  = Fr = Fv = mgv =v/r r  = Fr = mgr F=mg

19. Electrical Power • Power = Voltage x Amperage, P=VA • Voltage = Energy / # of Electrons • Joules / Coulomb of Electrons • Amperage = # of Electrons / s • Coulomb of Electrons / s • Voltage x Amperage = Joules / s = Watts • Measure V = 1 Volt, A = 1 Amp • P = VA = 1 Watt

20. Energy and Power are Convertible • Gravitational Potential to Kinetic Energy • mgh -> ½ mv2 • Rotational Power to Mechanical Power •  -> Fv = mgv • Torque x Angular Velocity = Force x Velocity • Rotational Power to Electrical Power •  -> VA • Without losses replace -> with = • Want to eliminate losses due to friction, drag etcetera

21. Windmill Design Two Components • Power Generation • Convert wind power to mechanical power • Wind -> Pushes Wind Mill Blades -> Wind Mill Shaft Turns • Power Distribution • Use power of rotating shaft to • Lift mass quickly • Move vehicle quickly • Generate Electricity

22. Multi-Task Windmill Challenge Lakewood 101 Box Fan ~1/2m x 1/2m 3.1 m/s air speed

23. How Much Power in Moving Air? • Power is Energy / Time • How much Energy in Moving Air • Kinetic Energy - ½ mv2 • m = Volume x Density of Air • 20” ~ 1/2 m, Volume = 1/2 m x 1/2 m x 1/2 m = 1/8 m3 • Density of Air - 1.225 kg/m3 • m = 1/8 m3 x 1.225 kg/m3 = .153 kg • Assume air moves 3.1 m/s • Energy is .74 Joules • 1/8 Cubic meter of air is replaced in .5 m/3.1 m/s = .16 seconds (t = d/v) • Power = Energy / Time = .74 Joules /.16 s = 4.6 Watts

24. Density of Air - 1.225 kg/m3 Fan 3.1 m/s ½ m 1/8 m3 ½ m ½ m ½ m Mass = 1.225 kg/m3 x 1/8 m3 = .153 kg

25. Fan 3.1 m/s ½ m .153 kg Kinetic Energy = ½ mv2 = ½ x .153 kg x 3.1 m/s x 3.1 m/s = .74 Joules

26. 3.1 m/s ½ m Fan 3.1 m/s ½ m .74 Joules .75 Joules t = ½ m / 3.1 m/s = .16 s Power = Energy / Time = .74 Joules / .16 s = 4.6 Watts

27. Betz’s Law Windmill Deflects Air

28. Two Windmill Types Vertical Rotating Shaft Horizontal Rotating Shaft

29. Simplified Horizontal Wind Mill Lift Force Lift Force rL =  = I Wind Wind distance r Side View Front View r-distance, L-Lift, -torque, I-Moment of Inertia, -angular acceleration

30. Factors for a Good Turbine Blade • Airfoil Design – “Design from the Side” • Planform – “Design from the Top” • Aspect Ratio – “Squat or Elongated” • Twist

31. Airfoil – Design from the Side • Airfoil works by redirecting moving • air downward (Action) resulting in • Lift (Reaction). The Bernoulli Effect • Loss of Pressure with increase • in velocity is a small effect.

32. Airfoil The key effect contributing to Lift is Leading Edge Suction due to turning off moving air about leading edge of wing. This is a consequence of the Viscosity of Air.

33. Airfoil A key airfoil characteristic is angle of attack . This allows the airfoil to redirect moving air downward. Thus even a flat plate can generate lift. 

34. Airfoil Camber or curvature of the wing allows more effective redirection of the air without flow detaching.

35. Airfoil Thickness about camber is also a Factor. A blunt leading edge with Maximum thickness ~1/3 way back And tapered trailing edge maximizes lift and minimizes drag.

36. Planform – Design From the Top Rectangular Tapered Elliptical

37. Induced Drag Wing Tip Vortex Low Pressure High Pressure

38. Wing Tip Vortex

39. Minimizing Induced Drag • Rectangle Maximizes Induced Drag • Although easy to construct • Ellipse Minimizes Induced Drag • But can be hard to construct • Tapered Planform Frequently Chosen • Almost as good as ellipse in minimizing drag • Reasonably easy to construct

40. Aspect Ratio • Aspect Ratio • Length of Wing / Average Width (Chord) Low Aspect Ratio High Aspect Ratio

41. Best Aspect Ratio? • Low Speed • High Aspect Ratio* • High Speed • Low Aspect Ratio

42. Wind Mill Blade Twist • Angle of Attack is dependent on the speed of the blade with respect to the air • If the blade is moving perpendicular to the wind the angle of attack will change

43. Blade must be twisted linearly to maintain optimum angle of attack Rotor Aerodynamics Electricity Generating Wind Turbines Use an odd number of blades to avoid harmonics Problem – Won’t know rotational speed  until windmill is built. So twist should be adjustable!

44. Typical Horizontal Windmill

45. Vertical Windmills Drag Type Vertical Windmill Lift Type Vertical Windmill

46. Vertical Wind Turbines • Have not caught on in the commercial market • Drag Type has low efficiency • Lift Type efficiency better • Optimal Design is not Clear • However • May be well matched for this contest • Insensitive to Wind Direction • Flow Field is Rectangular

48. Weight Lifting Challenge • h = 75 cm • Want to maximize Power = mgh/t • m is team’s choice • Testing required to find best combination • Rotation speed can be increased by Step-Up Gears • Linear Speed can be increased with large spool

49. Step Up Gearing 12 Teeth 8 Teeth

50. Kid Wind Gear Kit 8:1 Rotational Speed Gain