first report propeller design fyp 2003

8/8/2019 First Report Propeller Design FYP 2003

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Group

AhsanMansoorKhan

MunawarHussainJeelani

GroupSupervisor

Dr.AnwarulHaq

Mr.SherAfgan

PropellerdesignforveryhighaltitudeandlowReynoldsnumber


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ProjectDescription

Thepurposeofthisprojectistodesignapropellerthatisabletoproviderequiredamountofthrustfor

theaircrafttoliftitfromsealevelandclimbtoreachathighaltitudeforsustainedflightat70,000ft.

Propeller

Apropellerisameansofconvertingenginepowerintoapropulsiveforce.

Rotatingapropellerresults intherearwardaccelerationofamassofair,thereactiontothis

rearwardmotionisaforwardforceonthepropellerbladescalledthrust.

Thrust=MassofairflowxAcceleration

Thepropelleracceleratesa largemassofairrearwardatarelatively lowvelocity.Thereaction to this isa thrust forceacting ina forwarddirection,propellinganaircraftalong its

flightpath.Whenapropellerisfittedinfrontofanengine,itisatractor,whereaswhenfitted

attherearitisapusher.

Propellerefficiency

Propellerefficiencyistheratioofthrusthorsepower(THP),whichisdeliveredbythepropeller,

totheenginepower(BHP)requiredtodrivethepropelleratagivenrpm,expressedasa

percentage.

PROPELLEREFFICIENCY= THP/BHP

Anotherdefinitionistheratioofusefulworkdonebythepropellerinmovingan

aircraft,totheworksuppliedbytheengine.

Theworkdonebythepropelleristheproductofthethrustandforwardspeed(TAS).

Theworksuppliedbytheengineisthetorquerequiredtoturnthepropelleratagivenrpm.

PROPELLEREFFICIENCY=(THRUST*V)/P

V=Trueairspeed

P=Powerprovidedbytheengine


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Whentheaircraftisstationaryonthegroundwiththeenginerunning,thepropelleris0%

effective,since,althoughitmaybedevelopingalotofthrust,itisnotdoinganywork.

Astheforwardspeedoftheaircraftincreases,theefficiencyincreases.

Ingeneraltrendsefficiencylevelof88%uponachievingtheoptimumairspeedforthatpropellercanbeexpected.

Propellertypes

Fixedpitchpropeller

Fora fixedbladeangle,withvariations in forwardspeed theangleofattackchanges.As the

forwardspeedincreases,theangleofattackdecreasesandwithitthethrust.

ThedisadvantagesoffixedpitchpropellerarethattheFixedpitchpropellers,likemost

airfoils,aremostefficientonlyunderonesetofconditionsi.e.cruise.Butuntilreachingcruising

airspeed,theAOAofthepropellerbladesiscomparativelylarge;thereforethepropellerisless

efficient.Duringtakeoff,theAOAofthebladesofsuchapropellerwouldbeextremelylarge.

Thiswouldresultinpooracceleration,hencerequiringalongertakeoffrun.

For furtherunderstandingconsiderwhena fixedpitchpropeller isoptimised for takeoffand

climbperformance,thecruisespeediscompromised,sincethebladesAOAwouldbetoolow

formaximumefficiencyathigherspeeds.

Variablepitchpropeller

Duetothedisadvantagesoffixedpitchpropeller,variablepitchpropellerismost

suitabletouseasshowninfigurebelowwhichshowsgeneraltrendseeninpropeller

performanceforvaryingpitchangles.


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CounterRotatingPropellers

AirbusA400M

ContraRotatingPropellers


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DualPropellerApproach

VariableDiameterPropeller

SikorskyAircraft

Hartzell

Condorpropller


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ERAST

Pathfinder

PerseusB


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HighAltitudeCharacteristic

Airdensitydropsinhalfforevery15,000feetinaltitude lowairdensity,almostconstantairtemperature,thehorizontaldirectionmovement[1] Nothunderstormorclimatechange. Thesoundvelocitydecreaseswiththeincreaseofaltitude.

Soatahighaltitude,theMachnumberofbladetipairfoilprofileislargerthantheoneatthesealevel

andtheshockeffectincreasesatthesametime.

Machnumberisdefinedas:

M=V/a

where

V=speedofpropeller

a=Speedofsound

AsvalueofSpeedofsound(a)decreaseswithincreaseinaltitudeitcanbeseenfromtheequationthat

MachnumberincreasesprovidedtheSpeedofpropeller(V)iskeptconstant.

ReferenceAltitude:70,000ftaltitude

Density =1.399*104Slug/ft3

TemperatureT=389.990R

At SeaLevel

Density =2.37*103Slug/ft3

TemperatureT=518.690R

Comparingtheabovedataitisclearlyseenataltitudeof70,000ftthedensityis17timeslessas

comparedtosealevel.Asmentionedabove

Thrust=MassofairflowxAcceleration

Decreaseindensityathighaltitudewouldmeanlessmassflowavailableinturnthiswouldmeanless

thrustavailable.


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Themainproblemtodesignpropellerefficientenoughtoproduceeffectiveorrequiredamountof

thrustatsuchvaryingconditionswhereitshouldbeabletolifttheaircraftfromsealevelandclimbto

reachsuchhighaltitude.

TypesofexistingPropellersforveryhighaltitude

Highaltitudelongenduranceunmannedairplanes

Tier,Helios,Pathfinder

Reynoldsnumber

TheReynoldsnumberrepresentstheratiooftheimportanceofinertialeffectsintheflowtoviscous

effectsintheflow.

Reynoldsnumberisdefinedas

Re=UL/

Where:

U=characteristicvelocity

L=characteristiclength

=densityofthefluid

=dynamicviscosity

LowReynoldsnumber

MainEffectsoflowReynoldsnumberareasfollows:

Rapidlydescendingmaximumlifttodragratioofcommonairfoils AtmosphericdensitydecreasesandAirkinematicviscositycoefficientincreaseswiththe

increaseofheightinturnbothfactorsdecreasetheReynoldsnumber.

ThemainproblemassociatedwithlowReynoldsnumberistheAppearanceoflaminarflowseparation

bubbleeveninsmallattackangles(seeFig.(a)below),whichbringstheslowlyincreasedliftcoefficient

andtherapidlyincreaseddragcoefficient.


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Alongwiththeincreaseofattackangle,liftcoefficienteventdoesnotchangeanymorebutthedrag

coefficientstillincreasesrapidlywhichmakestheairfoilmaximumlifttodragratiodroprapidly.

a)AirfoilboundarylayerinlowMach

b)AirfoilboundarylayerinhighMach

Fig.boundarylayerschematicdiagramontheuppersurfaceoflowReynoldsnumberairfoil

[1]

Formoreclearunderstandingthefollowingexampleshowstheflowpatternsthatarecausedbythe

flowaroundacylinderforvaryingReynoldsnumber.


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Thickness: 9.1%

Camber: 3.8%

Trailingedgeangle: 7.1o

Lowerflatness: 94.9%

Leadingedgeradius: 1.8%

MaxCL: 1.143

MaxCLangle: 7.0

MaxL/D: 58.18

MaxL/Dangle: 5.0

MaxL/DCL: 0.955

Stallangle: 7.0

Zeroliftangle: 3.5

E174(Dicke8.92%)


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Thickness: 8.9%

Camber: 3.8%




MaxCL: 1.15

MaxCLangle: 7.0

MaxL/D: 58.383

MaxL/Dangle: 5.0

MaxL/DCL: 0.961

Stallangle: 7.0

Zeroliftangle: 3.5

S9037(9%)

Thickness: 9.0%

Camber: 3.5%




MaxCL: 1.246

MaxCLangle: 8.5

MaxL/D: 55.999

MaxL/Dangle: 4.5


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MaxL/DCL: 0.92

Stallangle: 8.5

Zeroliftangle: 3.5

SD6080(9.2%)

Thickness: 9.2%

Camber: 3.7%




MaxCL: 1.196

MaxCLangle: 8.0

MaxL/D: 57.556

MaxL/Dangle: 5.0

MaxL/DCL: 0.948

Stallangle: 8.0

Zeroliftangle: 3.0


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SD2083(9.0%)

Thickness: 9.0%

Camber: 2.8%Trailingedgeangle: 9.8o



MaxCL: 1.071

MaxCLangle: 7.5

MaxL/D: 54.066

MaxL/Dangle: 4.5

MaxL/DCL: 0.795

Stallangle: 7.5

Zeroliftangle: 2.5


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S1210

Thickness: 12.0%

Camber: 7.2%Trailingedgeangle: 6.9o



MaxCL: 2.248

MaxCLangle: 9.0

MaxL/D: 73.283

MaxL/Dangle: 6.0

MaxL/DCL: 1.961

Stallangle: 9.0

Zeroliftangle: 10.5


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PropellerNomenclature

Fig.Constantspeedpropellerbladepositions

Feathered:Whenthechordlineofthebladeisparalleltotheairflow,therebypreventingwind

milling.

CoarsePitch:themaximumcruisingpitchinnormaloperation

FlightFinePitch:Theminimumpitchobtainableinflight.


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GroundFinePitch:theminimumtorquepositionforgroundoperationandissometimes

referredtoassuperfinepitch.

ReversePitch:Anangletowhichthepropellerblademaybeturnedtoprovidereversethrust

fromthepropeller.

PropellerDesign

Differentparameterstoconsiderforthedesignarelistedasfollows:

Airfoilselection Airfoilthickness AirfoilCdversusClcurve Bladetwist Bladediameter PropellerHubdiameter RPM

BladeTwist

Thefollowingdiagramillustratesdifferencebetweenconstantbladeangleandbladewithtwist.

Asthepropellerforhighaltitudeapplicationbladewithtwististhelogicalchoicewhichgives

optimumpropellerperformanceatallbladestationstiptoroot.


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AdvanceRatio

Itistheratiooftheforwardspeeddividedbytheproductofrotationalspeedandthediameter

J=V/ND

V=Freestreamvelocity

N=numberofpropellerrevolutions/sec

D=Propellerdiameter

Startingpointforthedesign

Asinitialestimateofpropellerperformancetheanalysisusingfollowinginputswouldbedoneusing

simplebladeelementtheory.

ShaftPoweroutoftheEngine(hp) PropellerRPM(z) FlightAltitude(70,000ft) ForwardVelocity(Vo) AverageLocalVelocity(V) PropellerDiameter(D) NumberofPropellerBlades(n) BladeActivityFactor(AF) BladeDesignLiftCoefficient(Cl) PropellerAirfoilLiftToDragRatio(L/D)

Thismethodisbasedontheassumptionthat0.75rofbladelocationwhereristhechordof

bladesectioncanbeassumedtorepresenttheperformanceoftheentireblade.

ThisanalysisalsotakesintoaccounteffectsduetolowReynoldsnumberoperation.

HowevertheabovementionedanalysisisinaccurateiftheaircraftneedstooperateathigherMach

numberclosetoM=0.8howeverthisisefficientforlowersubsonicspeeds.

ForreferenceofthismethodFormulasandmethodisinitiallyreferredfrom

AircraftPropulsion:Scienceofmakingthrusttofly by BhaskarRoy HighAltitudePropellerDesignandAnalysisOverviewbyAnthonyColozza,FederalData

SystemsClevelandOhio44135,March1998.


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CostEstimation

CompositePropellerprototypemanufacturingCostestimated

Rs.20,000

Timeline


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References

[1] NumericalSimulationofLowReynoldsNumberandHighLiftAirfoilS1223byRongMa,PeiqingLiu,

ProceedingsoftheWorldCongressonEngineering2009VolII,WCE2009,July1 3,2009,London,U.K.

[2]36324005LowReynoldsNumberFlows.pdf

AircraftPropulsion:Scienceofmakingthrusttofly by BhaskarRoy

HighAltitudePropellerDesignandAnalysisOverviewbyAnthonyColozza,FederalDataSystems

ClevelandOhio44135,March1998.

DesignandPerformanceCalculationsofaPropellerforVeryHighAltitudeFlight,L.DanielleKochLewis

ResearchCenter,Cleveland,Ohio

Selig,M.S.,Guglielmo,J.J.,Broeren,A.P.,andGiguere,P.,SummaryofLowSpeedAirfoilData

(TranslationJournalsstyle),vol.1,SoarTechPublications,VirginiaBeach,VA,1995.

Selig,M.S.,andGuglielmo,J.J.,HighLiftLowReynoldsNumberAirfoilDesign,AIAAPaper941866,

June1994.

Airfoildatabase:DaVinciTechnologies,

http://www.davincitechnologies.com/AirfoilOptimizerStdAirfoils.htm

AirfoilInvestigationDatabase,http://www.worldofkrauss.com/

first report propeller design fyp 2003

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