Multi-Task Windmill Challenge 2010

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MESA Wind Energy Challenge

A Multi-Task Windmill

August 2010

Tom MilnesJHU/APL & AIAA Mid-Atlantic Section

Mid-Atlantic Section


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AIAA Mid-Atlantic 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


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AIAA Support for K-12 Educators

AIAA Grant Program

$200 per teacher, up to $1000 per school for K-12Classroom projects related to Aerospace

Steps Join AIAA for Free as an Educator Associate

https://www.aiaa.org/content.cfm?pageid=208

Submit Online Application


Must conform to guidelines, Principal approval needed



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Multi-Task Windmill ChallengeLakewood 101 Box Fan~1/2m x 1/2m

3.1 m/s air speed


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Check This Out!!


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Motion

An objects motion is fully described bytranslation of its Center of Mass and rotation

about its Center of Mass (CM)


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Motion Continued

Translation Can Occur in 3 Dimensions

Rotation Can Occur in 3 Dimensions

Full Description of Motion is referred to as 6Degrees of Freedom (6-DOF)


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Forces and Motion

Forces Acting through CM only causestranslation

Forces acting a distance (torque X) from CM willalso cause rotation

F F

r

X = rF

F=maX = IE


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Translation and Rotation for

Challenge Generally center of mass is pinned for rotating

elements so motions are eitherpure

translation orpure rotation in this challenge Trick is to covert Power and Energy from

Translation to Rotation, vice-versa, and to otherforms


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Energy Energy is required to do Work

Work is done when an object is moved a distanceagainst 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 groundhas Gravitational Energy = mgh

If dropped will convert to kinetic energy

Kinetic Energy on Ground = mv2 = mgh


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1 kg g = 9.8 m/s2

F = 9.8 N


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1 kg

g = 9.8 m/s2

F = 9.8 N

h = 1 m

Work = Fh = Energy= 9.8 Joules


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Rotational Work

Its takes energy to rotate an object against atorque

Work = Energy = XU X m F, h m U


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Power Poweris Required to Work Quickly

Power = Energy / Time

Poweris 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

Poweris required to sustain an angular velocityagainst a torque

Power = Torque x Angular Velocity, P=X[


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1 kg g = 9.8 m/s2

F = 9.8 N


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1 kg

g = 9.8 m/s2

F = 9.8 N


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1 kg

g = 9.8 m/s2

F = 9.8 N


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1 kg

g = 9.8 m/s2

F = 9.8 N


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1 kg

g = 9.8 m/s2

F = 9.8 N

1 m/s

Power = Fv = Energy/s= 9.8 Watts


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Power Rotating Shaft to Move a

Mass

r

F=mg

X = Fr = mgr

[=v/rP = X[ = Fr[ = Fv = mgv


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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


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Energy and Power are Convertible

Gravitational Potential to Kinetic Energy mgh -> mv2

Rotational Powerto Mechanical Power X[ -> Fv = mgv

Torque x Angular Velocity = Force x Velocity

Rotational Powerto Electrical Power X[ -> VA

Without losses replace -> with = Want to eliminate losses due to friction, drag

etcetera


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Windmill Design Two Components

Power Generation

Convert wind power to mechanical power

Wind -> Pushes Wind Mill Blades -> Wind Mill ShaftTurns

Power Distribution

Use power of rotating shaft to

Transfer power by moving mass

Move vehicle quickly

Generate Electricity


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How Much Power in Moving Air? Power is Energy / Time How much Energy in Moving Air?


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Fan

m

m

m

m

3.1 m/s

1/8 m3

Density of Air - 1.225 kg/m3

Mass = 1.225 kg/m3 x 1/8 m3 = .153 kg


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Fan

m

3.1 m/s

.153 kg

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

3.1 m/s


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Fan

m

3.1 m/s

.75 Joules.74 Joules

t = m / 3.1 m/s = .16 s

m

3.1 m/s

Power = Energy / Time = .74 Joules / .16 s = 4.6 Watts


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Betzs LawWindmill Deflects Air

2 1

1Ideally v v giving a maximum power conversion of 16/27 (.59)3

Need a method of measuring airspeed to test this!

!


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Cowling?


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Cowling Used by Washington State MESA Team


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Two Windmill Types

Horizontal Rotating Shaft Vertical Rotating Shaft


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Simplified Horizontal Wind MillLift Force

distance r

Lift ForcerL = X = IE

r-distance, L-Lift, X-torque, I-Moment of Inertia, E-angular acceleration

Side View

Wind

Wind

Front View


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Factors for a Good Turbine Blade

Airfoil Design Design from the Side

Planform Design from the Top

Aspect Ratio Squat or Elongated Blade Twist


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Airfoil Design from the SideAirfoil works by redirecting movingair downward (Action) resulting inLift (Reaction). The Bernoulli Effect- Loss of Pressure with increasein velocity is a small effect.


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Airfoil

The key effect contributing to Liftis Leading Edge Suction due toturning off moving air about leadingedge of wing without increase inspeed. The so called

Coanda Effect resultsfrom the Viscosity ofAir.


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Airfoil

A key airfoil characteristic is angleof attack U. This allows the airfoil toredirect moving air downward. Thuseven a flat plate can generatelift.

U


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Airfoil

Camberor curvature of the wingallows more effective redirectionof the air without flow detaching.


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Airfoil

Thickness about camberis also aFactor. A blunt leading edge withMaximum thickness ~1/3 way backAnd tapered trailing edgemaximizes lift and

minimizes drag.


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Planform Design From the Top

Rectangular

Tapered

Elliptical


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Induced Drag

High Pressure

Low Pressure

Wing TipVortex


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Wing Tip Vortex


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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


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Aspect Ratio

Aspect Ratio

Length of Wing / Average Width (Chord)

Low Aspect Ratio

High Aspect Ratio


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Best Aspect Ratio?

Low Speed

High Aspect Ratio*

High Speed

Low Aspect Ratio


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Wind Mill Blade Twist

Angle of Attack is dependent on the speed ofthe blade with respect to the air

If the blade is moving perpendicular to the wind theangle of attack will change


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Rotor Aerodynamics

(r) r [

Blade must be twistedmaintainoptimum angle of attack

Electricity GeneratingWind Turbines Use an

odd number of blades toa oid harmonics

Problem Wont know rotational speed [ until windmill is built.

So twist should be adjustable!


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Blade Twist Diagram

WINDv

B Dv r! [

I /B Dv

F

WIND

WIND

tan

(r) ar

r

ctan

v

v

r

F !

F!

[

[


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Typical Horizontal Windmill


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Blade Design Materials

Pink or Blue Foam Board

3-D Printer

Balsa Wood / Shrink Wrap


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Vertical Windmills

Drag Type Vertical Windmill Lift Type Vertical Windmill

X TI

WI D WI D

rT

[! ! X TI

WI D WI D

rT

[! ! "


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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


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Weight Lifting Challenge

h = 75 cm

Want to maximize Power = Weight x Velocity

Weight = mg, Velocity = h/t m is teams choice

Windmill is intrinsically a high torque, low speed

device Best strategy is to lift large Weight at low speed

Attempt to increase speed leads to power losses


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Weight Lifting Challenge


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Vehicle Challenge


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Possible Solution

PulleySystem


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Wind To Vehicle Setup


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Wind Changing Electric Power

Wi d Ch i El t i P


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Wind Changing Electric Power


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Handling Wind Change

Horizontal Windmill

Wind Vane

Turning Bearing Vertical Windmill

No Problem!

M l d HS Ch i Wi d T i M h i


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Maryland HS Changing Wind Turning Mechanism


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Generating Electrical Power


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Electrical Power Generation

High rotational speeds are required for efficientelectrical generation

Windmills are high torque low speed devices How can rotational speed be increased.

Proper gearing!


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Step Up Gearing

12 Teeth

8 Teeth8 12

12

8[ ! [


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Kid Wind Gear Kit

8:1 Rotational Speed Gain


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Step Down Pulleys

1r

r

1

1

r

r[ ! [


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Power Losses

Must carefully watch for power losses in everystage

Rotating Shaft, Pulleys, Rotating Bearings Must Minimize Rotational Inertia I in Rotating

Elements

Eliminate unneeded mass


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Scoring

Technical Paper 100 points

Academic Display 100 points

Oral Presentation 100 points

Device Performance 150 points

Total Points 450 points


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Performance Scoring

Mass Lift

Wind to Vehicle

Electrical Power

MS HS


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Resources

Tom Milnes [email protected] Kid Wind Website - http://www.kidwind.org/

Wikipedia

http://en.wikipedia.org/wiki/Wind_turbine American Wind Energy Association

http://www.awea.org/

Competition Guidelines http://www.jhuapl.edu/mesa/events/natl/competition.

asp

Multi-Task Windmill Challenge 2010

Documents