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FORAERONAUTICS
TECHNICALNOTE3062
A F12GHTINVESTIGATIONOF THEPRACTICAL
PROBIIIIMSASSOCIATEDWITHPOROUS-
LEADING-EDGESUCTION
ByPaulA..HunterandHaroldL Johnson
LangleyAeronauticalLaboratoryLangleyField,Va
~
WasMngt.on
February1954
.-.2~.
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https://ntrs.nasa.gov/search.jsp?R=19780078540 2018-05-22T13:14:47+00:00Z
TECHLIBRARYKAFB,NM
lx
.NKTIONALADVISORYCOMMITTEEFORAERONAUTIC.
.
IIOLL274
TECHNICALNOTE3062
A FIZGHTINVESTIGATIONOFTHEPRACTICAL
PROBIIMSASSOCIATEDWITHPOROUS-
IWDING-EDGESUC?TION
By PaulA. HunterandHaroldI.Johnson
SLIMMARY
A flightinvestigationhasbee~made.oftheyracticalproblemsassociatedwiththeuseofporous-leading-edgesuetion. Thewingleadingedgeofthetestairplanewasporousoverapproximately83 per-centofthespansndthefirst8 percentofthecholdontheuppersurface.VWiousotherextentsofsuctionareawithintheselimitswerealsotested.
Resultsofthisinvestigationhaveindicatedthata wingequippedwithporous-leading-edgesuctioncanle constructedwhichhassufficientstrengthanddurabilityforusein flightwithoutaddingexcessiveweight.Forthetypeofporousmaterialusedinthisinvestigation,cloggingdueto atmosphericdustdidnotappearto%e a problem.Forthelightrainencounteredinflight,thePOWEYrequiredto producea givenflowcoef-ficientwasabout50 percent.nmrethanthatrequiredforthedrycondi-tion. Basedonthegrounddata,itwasestimatedthatforflightinheavyrainthepowerwouldbe approximatelytwicethatforthedrycondi-tion. Atmaximum%lowerspeedtheporousareabecsmeclesredwithin3 to 4 minutesafterwaterceasedto impingeonthesurface.Undercertainconditions,testsshoweda severevibratjonoftheporousmate-rialinducedby an “organpipe”resonanceoftheaircolumuwithintheducts. As expectedfromwl.nd-tunnelresultsobtainedprevioustothisinvestigation,theuseof leading-edgesuctionwiththesmallamoumtofpoweravailablehadlittleeffectonthemaximumliftcoefficientdevel-opedwiththeairfoilsectionusedinthiswing(MICA2412).Ingeneral,an appreciabledropoccurredinmaximumliftcoefficientfromtheleading-edge-sealedconfi~ationto theconditionof zerosuctionwiththeporous-areaconfigurationstested.Incrementsin liftcoefficientduetothesuctionavailablegenerallybroughtthemaximumliftcoefficientbackapproximatelyto thevalueforthewingwiththeleadingedgesealed.Themaximumtheoreticalaerodynamicpower,ifductlossesareexcluded,variedwiththeconfigurationstestedfrom3.65 to 9.70 horsepower.
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INTliODUCTION
Theuseofporoussurfacesforboundary-layercontrolhasforaperiodofapproximately30 yearsbeenthesubjectofmanytheoreticalandexperimentalstudiesinvolvingareasuction.Previousflightstudiesof sreasuctionhavebeenlimitedmostlytomodelssndpartial-spantestsections(forexample,refs.1 and2),althoughan incompleteinvestiga-tionofsreasuctionappliedtonearlyalltheresrwardportionsoftheuppersurfaceofthewtngsofan airphe wasqadeinEnglandnearthebeginningofWorldWarII (ref.3). In thepresentinvestigation,porous-leading-edgesreasuctioncoveringthefirst8 percentchordontheuppersurfacewasappliedto essentiallytheentirewingspanoftheairplanetested.
Theuseofareasuctioninvolvesseveralpracticalproblemswhicharenotreadilysolvablebywind-tunnelstudies.Oneofthegeneralproblemsisthecloggingoftheporesofthemoredensematerialsby atmw-phericdustandby rain. Constructionofa structurallyefficientwingwithporoussurfacesisanotherpracticalproblemwhich,thoughimportant,doesnotappeartobe extremelydifficult,particularlyinthedesignofa newwingwheretheductingcanhe madepartof theload-carryingstructure.
TheNationalAdvisoryCcmmitteeforAeronauticshasconductedaflight-testpro-to investigatevariouspracticalproblemsassociatedwiththeuseofporousmaterialsforboundary-layercontrol.Becausetheairplaneavailableforthetestshada rounded-leading-edgetypeofair-foil(NACA2412)characterizedby a trailing-edgestall,verylittlebenefitinmsximumliftcouldbe expectedfromtheapplicationof lead.ing-edgesuction.Thisexpectationwasverifiedby two-dimensionalwind-tunneltestsmadepriorto theflightinvestigation.
SYMBOLS
b s-pan,ft
c localchord,ft
CL airplaneliftcoefficient,-lL(ncosa+Zsj.na)~cSA
‘
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NACATN 3062 2
CQ
Ho
%
H1
2
n
P
PO
pd
PI
AP
Q
q
qc
%
ql
s
SA
s;
‘P
d
suctionflowcoefficient(aconstantvalueof S~ correspondtigto 89.2percentoftotalwingareawasusedincomputingflow
coefficients),-Qvs~
free-streamtotalpressure,% +Po, lb/sqft
ducttotalpressure,p~ + qd,lb/sqft
ducttotalpressureat outboardmeasuringstation,lb/sqft(assumedH1 = PI; ql = O)
longitudinalacceleration,~sitiveforward,g units
normalacceleration,positiveupward,g units
staticpressureatwingsurface,lb/sqft
free-streamstaticpressure,lb/sqft
ductstaticpressureat inboardmeasuringstation,lb/sqft
ductstaticpressureatoutboardmeasuringstation,lb/sqft
pressuredifferenceacrossporousmaterial,lb/sqft
totalvolumeflowrate,cu ft/sec
impactpressureatwingsurface,lb/sqft
calibratedimpactpressure,lb/sqft
ductimpactpressureatinboardmeasuringstation,lb/sqf%
ductimpactpressureatoutboardmeasuringstation,lb/sqft
pressurecoefficient,HO-P q=—qc %
wingarea,sqft
wingareaaffectedby suction(sreabetweenspanwisestationsatouterextentsofporousarea)
areaofporous~terialmeasuredalongsurface,sqft
.
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v trueairspeed,ft/sec
v apparentvelocitythroughporousmaterial,~, ft/sec%
w airplaneweight,lb
x chordwisedistance,ft
Y spanwisedistance,ft
z distancenormalto sirfoilchord,ft
a calibratedangleof attackreferredto thrustsxis,deg
APPARATUS
Airplane
FlighttestswereconductedontheCessna190airplane(seetableIfordimensionaldsta)showninthephotographs”presentedasfiguresl(a)andl(b)andinthethree-viewdrawinginfigurel(c).Therelativesizeandlocationofthelower-surfacesplit-typeflapareshowninfigure1(c).Figurel(d)showsa comparisonoftheactualwingprofileat a representa-tivespanwisestationwiththeNACA2412profileandalsosomedetailsoftheporous-leading-edgeconstructiontobe describedsubsequently.TheactualwingprofilediffersfromtheNACA2412profileinthatithasaslightlylargerleading-edgeradius,haslesscamberinthefirst10per-centofthechord,andhas& slightamountofnegativecamberinthefirst2 percentof thechord.Thesevariationsresultedfrommanufac-turingandmodification-shoptolerances.
-Boundsry-Layer-ControlEquipment
Theporoussurfaceconsistedof a sandwichcontaininganoutersur-faceofwovenMmel filtercloth,a 16-meshcopperwindow-screensepa-rator,anda backingof0.016-inch-thickperforatedbrasssheet.ThefilterclothwaswoveninDutchweavewith30wiresby 250wiresperinchto a thicknessof0.028inch,rolledto0.020inch,andfurtherhamneredto 0.018inchto reducetheporosityandimprovethesurfacesmoothness.ThefilterclothwasobtainedfromtheMichigsnWireClothCompany.Theperforatedbrass,whichwasusedto stiffenthefiltercloth,had714openingsof0.020-inchdiameterpersquareinchspaced0.041inchapart. . .Thesandwichwasformedto theleading-edgecurvatureon steeljigsandthethreelayerscementedtogetherwitha plasticadhesiveattheedgesonly. u
NACATN 3062 5
Wind-tunneldataindicatedthatmostoftheadv~tageofPorous-leading-edgesuctionontheNACA24I2airfoilcouldbe obtainedwithavalueof CQ of 0.002whichcorrespondsto an inflowvelocityof3.6fpsat anairspeedof 63mph. Thedesignporositywassuchthata pressuredifferenceof72.8lb/sqf%wouldproducea velocityof3.6fpsthroughtheporousmaterial.Thearithmeticmeanof 20 readingsofporosityofonlythefilterclothshoweda velocity3 percentabovedesignvelocityatdesi~pressuredifference(moreporous).Thecopperscreenandperforatedbrassdclnotappearto addappreciableresistance.
Figure2(a)showsthegeneralarrangementof equipmentandductingintheairplane.Theleadingedgeofthewingwasporousover83.4per-centofthespanandthefirst8 percentofthechordontheuppersurfaceas showninfigurel(b).Theleading-edgeductwasformedbytheincorpo-rationofa falsespar,ductbottom,andporousmaterialsupportsasshowninfigure2(b). Theporouscoveringwasattachedattheedgesinsectionswithmachinescrews;theedgeswerefairedwithmodelingclayandshellacked,as showninfigure2(c).,A portionof thewindowoverthepilot’sheadwasreplacedby a pancoveredwithporousmaterial,SEshownin figurel(b),inorderto continuetheareasuctionoverthecentersection.Theundersideofthepanandpartoftheductingareshownin figure2(d).Theflowwasremovedfromeachwing-leading-edgeductatthewingrootby theductshownin figure2(e)whichincorporatedturningvanesinthe90°bend;theflowwasthenfurtherductedtothebloweras shownin figure2(f). Thesmallductshowninfigure2(f)isthecontinuationoftheductfromthecentersectionshowninfigure2(d).Fromtheblowerexit,theflowwassplitandwasexpelledfromtheexitholesonthesideofthefuselageas showninfiguresl(a)and2(a).Twobutterfly-typeshutterswereinstalledintheexitductsbehindtheblower.
Theblowershownin figure2(f)isthecompressorstageof a largeaircraft-engineturbosuperchargerwhich,thoughnotideallysuitedtothisapplication,wasusedbecauseitwasreadilyavailable.Theblowerwasdrivenby a smallautomotiveenginerated25 horsepowerat 4,400rpmanda right-anglegearboxin sucha mannerthattheblowerspeedwasthreetimesthatoftheengine.Theengine-blowerinstallationis shownin figure2(g). Engineandexit-ductshuttercontrolsweremountedonthetopoftheenginecoveras canbe seeninthisfigure.Thelouversinthetopofthefuselagejustbehindthewing,showninfigurel(c),wereinstalledto removeenginefumesfromthecabin.
Duringtheinvestigation,largedeflectionsoftheporoussurfaceoccurredwhensuctionwasappliedin configurationswherelargeportionsoftheporousareaweresealed..!I’hisconditimrequiredadditionalstiffenerstoreducetheunsupportedlengthof theporousmaterialfromtheapproximately30-inchspanwiseincrementsshownin figure2(b)to
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about10inches.Theseadditionalsupportsweremadeofthinduraluminplacededgewiseto theporousmaterialwiththeedgeshsrpenedto reduce Hinterferenceofthesupportto theflow.Thesupportswere1 inchwidenormaltothewingsurfaceandhadtheloweredgeflangedto stiffenthesupportandto assisttheflowtoturninboardafterpassingthroughtheporousmaterial.Photographsofthenormalleadingedgeandleadingedgebuckledby suctionareshowninfigure3.
Instrumentation
StandardNACAinstrumentationwasprovidedto recordcontinuouslyairspeed,threecomponentsofacceleration,rollingandpitchingveloci-ties,sideslipangle,angleof attack,controlpositions,controlforces,temperatures,angleofbankorpitch,airplaneheading,andpressures.Theairspeedusedinthispaperis calibratedairspeedasobtainedbymeasuringpressuresfroma total-pressuretubeanda swivelstatic-pressuretubermauntedona boom1:chordsaheadoftheleadingedgeoftherightwing
(fig.1)sndby correctingthosepressuresforpositionerroras deter-minedfroma trailingbomb. Theangleofattackandangleof sideslipwereobtainedby useoffree-floatingvanesmountedon a boom12chords
4aheadoftheleadingedgeoftheleftwing(fig.l(a)).Theanglesreadfromtheangle-of-attackvanewerecorrectedforrollingandpitchingvelocitiesanderrorduetotheinducedflowfieldaheadoftheairplane.
Staticpressuresweremeasuredatthreespanwisepositionsalongtherearwardwall,atonepositionontheoutboardendwallof oneleading-edgeduct,sndatonepositionintheblowerexitduct.Theorificeontheoutboardendwallisreferredto subsequentlyastheoutboardmeas-uringstation.Flowquantitiesweremeasuredin eachofthethreelongi-tudinalductsby usingtotalpressureandtheaverageof fourstaticpressuresin eachofthelargeductsandby usingstaticpressureattheentryandthroatofa venturiinthecenter-sectionduct.Temperaturesoftheflowinoneofthelargeductsandinthecenter-sectionductwerealsorecorded.A surveyoftotalpressurewasmadeacrosseachmainductpriortotheflightteststo determinethevelocitydistributionintheseducts. A dischargecoefficient,estimatedat0.974,wasusedindeter-miningthevelocitythroughtheventuriinthecenter-sectionduct.
Tuftpicturesoftheflowoverthewingweremadewitha rearward-facing35-millimetermotion-picturecamerawhichwasnmuntedaboveandbehindthewingonthestructureshowninfigures1(%)and2(c)andwhichphotographeda sphericalmirrorthatreflectedan ima5 oftheentirewing.
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TESTS
Flighttestsweremadeto determinethepowerreqtiements,theeffectof vexyingsuctionflow,andtheeffectofvaryingtheextentofporousareaontheliftcoefficientandangleof attackatthesta~ inthecourseof accrmndatingflighttimeontheporoussurfaces.Stallsweremadeatfourdifferentblowerspeedsineachofthefollowingconditions:airplsneenginewitha manifoldpressureof2’5inchesof~rcury,at2,200rpm,flapsup anddown,andairpbneengineidling,flapsup anddown. Allflightdatapresentedinthisreportwereobtainedaftertheadditionalchordwisestiffenerswereinstalled.Inmskingtheflighttests,theblowerwassetat a predeterminedspeedata flightspeedofapproximately85to90 mphandno furtherchangesinblowercontrolsettingweremadeduringthesubsequentstallapproach.Theresultwasapproximatelyconstant-volumeflowthroughtherangeof airspeedobtainedduringeachtest. Thevariousspanwiseandchordwiseextentsof suctiontestedareshowngraphicallyinfigure4. Theextentofporousareawasvsriedby sealingportionsoftheporoussreawithcellulosetape.Theratioofwingareasffectedby suctiontototalwingareaasdeterminedby thespanwiseextentofporousareaandtheratioofporousareatototalwingareaarealsogiven.Inorderto determinetheeffectofwateron theporousmaterial,oneflightwasmadewithleading-edgeconfigura-tion(a)(fig.4)inrainofvaryingintensity.
Testsweremadeonthegroundatvarioustimesduringtheprogramtodeterminetherelativeporosityandpowerrequirementsoftheporoussur-faceasaffected%y time,flighttime,andwater.Thesetestsweremade .by runuingthebloweratvarioussteadyrotationalspeeds.Rainwassimulatedin someofthesegroundtestsby sprayingthewingwithwaterandtakingrecordsatfullthrottleandalsoby firstwettingthewingandthenstsrtingtheblowerengineat fullthrottle.All~oundtestsweremadewithleading-edgeconfiguration(a)(full8 percent).
RESULTSANDDISCUSSION
PracticalProblems
Sincethisinvestigationwasa researchprojectto determinethepracticabilityoftheporoussurface,theweightandvolumeofthecompo-nentsotherthantheporoussurfacewerenotgivenmuchconsiderationsolongastheywerenotexcessive.As a result,theweightoftheairplanewithboundary-layercontrolwaslarge.An appreciablereductioninweightswouldhavebeenpossiblehadanairplanebeendesignedespecially
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fortheboundary-layer-controlinstallationandhadoneofthehigh-power-to-weight-ratioblowersystemsnowavailablebeenused. WeightsoftheprimarycomponentsaregivenintableII.
Porosity.-Dataaffectingtheporosityoftheporousleadingedgeasdeterminedfroma numberof groundtestsareshownintableIII. Theresultsofthetestssreshowninfigure5 plottedasapparentvelocitythroughtheporousmaterialagainstthepressuredifferenceacrosstheporousmaterial.Comparisonofthedataoftests1 and2 indicatesnolossinporosityafterapproximately12hoursof flighttimeand89 daysofbeingparkedin a ratherdustyhangar.Dustthereforeseemstohaveno adverseeffectsonthepractic&bilityofthistypeofporotisurface.Theapparent@n inpawsitybetweentests1 and2 maybe takenasanindicationoftheaccuracyofmeasurement,withthetrueporositycurvelyhg somewherebetweenthetwofairedcurves.Thelossofporosityshownby thedataoftest3 maybe attrilnrbedto theretentionofadhesivefromthecellulosetape,whichwasusedto varytheextentofporoussrea,afterthetapehadbeenremoved.Testsmadeafterthefirsttwoattemptsat cleaning(tests4 and5) apparentlysucceededonlyjn drivingtheadhes-ive deeperintothesurfacewithsuccessivelossesinporosity.Iatertests(tests6,7, and8)madesfteradditionalattemptsat clesningandadditionalflighttimeshowedslightincreasesinporosity,buttest9madeneartheendoftheflig@ investigationshowedan appreciableincreaseinporosity.No cleaningwas“attempted%etweentests6 and9.Theexplsnationappearstobe thatthesolventscontainedintheadhesiveparticlesdriedoutandpetittedtheremovaloftheresidueby airandby,airandwatermixtureswhichpassedthroughtheporousmaterialduringflightandgroundtestsjustpreviousto test9.
Theshapeofthecurvesinfi~e 5 givessomeindicationof thetypeofflewthroughtheporousmaterial.Thestraight-linecurveshavingtheiroriginsat zerofortests1,2,3, and9 indicatethattheflowthroughthescreenforthesetestswasnmstlyviscous.Althoughstraightlinescouldreasonablybe fairedthroughthedatafortheothertests,extrapolationofthelinesdidnotpassthroughzerovelocityat zeropressure.Onesetofdataforwhichpointsinthelowvelocityandpres-surerangewereavailable(test8) showsappreciablecurvatureinthisrange,snindicationofa transitionfrommostlyviscoustomostlyturbu-lentflow.A seeminglyreasonableexplanationforthischangeisthat,astheeffectiveTorousareawasreducedby partialblockingof someofthepassagesintheporousmaterial,thecriticalReynoldsnmbed oftheflowthroughtheporousmaterialwasreachedsndtransitionto turbulentflowoccurred.
Effectsofrdn.- Theeffectsofrain,realandsimuhted,ontheporousmaterialareshownin figures6 and7. Figure6 showsa comparison ‘of groundandflighttestswherethedataforthedrygroundtestaretakenfromtest8 (seefig.5). An explanationforthelargedifference u
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2xNACATN 3062 9
inpressuredifferentialbetweenthedryandwetconditionsforthegroundandflighttestsmaybe thatthesimilatedrainforthegroundtestswasmuchheavierthantheactualrainencounteredin flight.Theinter-ceptofthedashedlinesfortheflightdatawiththepressurescalerepresentsa reasonablevalueoftheaveragepressureontheexternalsurfaceoftheleadingedgeinflightas determinedby themethodexplainedintheappendix.Thepressuresforthegroundtestsrepresentthepres-suredifferenceacrosstheleadingedgeonly,whereasthefllghtpressuresincludethepressuredropabovethewing(estimated63 lb/sqft). Fig-ure6 showstheincrementinpressureproducedby simulatedheavyrainin groundteststobe approximatelyequalto thepressuredropabovethewinginflight.Thus,forflightinheavyrainthepressurewhichtheblowerwouldhaveto overcomewouldbe approximatelytwicethatforflightinthedrycondition.Thisincrementwasoftheorderof50per-centforthelightrainencounteredin flight.
Figure7 showsa comparisonoftwogroundtestsinwhichtheblowerenginewasstsrtedatfullthrottle.Thenumbersalongthecurverepre-senttimein secondsfromstarting.Nowaterwasaddedto theleadingedgeforthewetconditionafterstsrting.It appearsthat,undertheseconditions,theporousmaterialwouldhavecompletelycleareditselfofwaterwithin3 to 4 minutes.
mom theseresults,rainappearsto be a veryimportantfactorwithregardtothepracticabilityofporous-leading-edgesuction.A suctionsystemhavinga blowerwhichoperatedat designpressureratioindryair,aswouldprobablybe thecaseforotherthanexperimentalsystems,wouldbe greatlyhihderedinrain,sincetheblowerwouldnotbe capableofproducingtheadditionalpressuredropneeessaryto overcomethesur-facetensionofthewaterintheporoussurface.Theblowerusedinthisinvestigationwasbeingoperatedatpressureratiosoftheorderofone-fourthitsratedpressureratio;thus,theadditionalpressuredropwaswellwithinitscapabilityinasnmchastheblowerefficiencyapparentlyincreasedgreatlywithincreasingpressureratio.Duringthegroundsimulatedraintests,an appreciableamountofwatercouldbe seencomingoutofthefuselageexitducts.Thisconditionwouldappearto obviatethepracticabilityofusinganywater-absorbingmaterialsuchas feltforanypartoftheporoussurfacesincethewaterwouldprobablygreatlyincreasethedensityoftheporoussurface.Apparently,additionalworkshouldbe doneontheeffectofrainonporous-areasuction.
Powerrequirements.-Thepowerrequirementswerecalculatedastheproductofvolumeflowrateanddifferenceintotalpressuremeasuredatanytwostationsbetweenwhichtheincrementofpowerwssdesired.Theestimateddistributionofpowerfortheglidingcondition(aircraftengineidling,flapsup)withleadhgzedgeconfiguration(a)atmaximumblowerspeedazthestallisshowninfigure8.
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Sincenowing-surfaceorificeswereprovided,thedivisionofthetheoreticalaerodynamicsuctionpower(calledusefulpowerhereinforsimplicity)intopowerrequiredto overcomeporous-materialdragandpowerrequiredto reduceductpressureto averagesurfacepressurewascalculated.Theestimationoftheleading-edgesurfacepressurefromwhichthepressuredropequivalenttothesetwopowerrequirementswasdeterminedisgivenintheappendix.Themaximumtheoreticalaerodynamicpower,ifductlossesareexcluded,veriedwiththeconfi~ationstestedfrom3.65to 9.7ohorsepower.Thepressuredropproportionaltotheductpowerlossshowninfigure8 waspartiallymeasuredandpartiallycalcu-lated.Ductlosswasmeasuredbetweentheoutboard-ductstaticorificeandthevelocity-meas~ingstationinthewingroot.Ductlossesfromthisstationtotheblowerendfromtheblowertothefuselageexitswerecalculatedwiththeaidof reference4. Thecalculatedductlossamountedto aboutkopercentofthetotalductloss.
Thepowerto driveaccessorieswasestimatedtobe 1 horsepowerandthegesrboxefficiency-sassumedas98percent,whichisveryreasonableforthespiralbevelgearsused.Theenginepowerwastakenfroma powercurvewhichwassuppliedbytheenginemanufacturerwiththeengineandwhichwascheckedandfoundtobe reliable.Theblowerlosswastakenasthedifferencebetweentheenginepoweroutput(ata particularrotationalspeed)andthetotalofotherpowerrequirementsgivenpreviously.Themsximumobtainableenginerotationalspeedwasappreciablylimitedbympropermatchingof enginetorqueoutputandtorqueinputrequiredbytheblower,sothatatno timewasfull-ratedpoweroutputoftheengineobtained.
TableIV showsthevariationwithblowerspeedandleading-edgeconfigurationoftheratioofusefulpowerto engineout~utpower,theratioofporous-materialpowertousefulpower,theapproximateratioofductpowerlossto engineoutput,andtheapproximateblowerefficiency.Valuesofengineoutputpowerandflowcoefficientforeachcae arealsogiven.
AerodynamicData
Effectof suctiononmaximumlift.-A sunmmryofthemainaerodynamicdataobtainedduringthisinvestigationis showninfigure9 asthevaria-tionof liftcoefficientwithflowcoefficientforvariousextentsoftheporousleadingedgeandvsriousairplaneconfigurations.Thefirstpointtobe notedisthatthereisan initialdroph liftcoefficientfromthecompletelysealedconfi~ationto thezero-suctioncase(ductdampersclosed)withallleading-edgeconfigurationsexceptconfi~ation(e)(centersectiononly)andconfi~ation(f)(last1 percent)in fig-ures9(d)and9(e),respectively.Theapparentreasonforthisbehavioristhata circulatoryflowissetup throughtheporoussurfaceasa
.
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resultofthelsrgepressure~adientabovetheporousarea.‘Thiscircu-latoryflowevidentlyhastheeffectofpronmtingseparationata lowerangleof attackthanthatatwhichitwouldoccurifthisflowdidnotexist.Figure10showsthetheoreticalpressuredistributionovertheuppersurfaceoftheleadingedgeoftheNACA2412airfoilata liftcoefficientof 1.6. Thedifferenceinpressuresoverthefirst1 percentmaybe seentobemuchlessthanthedifferenceinpressuresoverthefull8 percentsothattherewouldbe lessopportunityforlocaloutflowto occuroverthefirst1 percent.As thechordwiseextentofporousareawasvariedfrom8 percent(configuration(a))infigure9(a),to2 percent(configuration(b))in figure9(b),andfinallyto 1 percent(configuration(c))infigure9(c),theinitialdropin liftcoefficientbecsmeprogressivelyless.Figure10showsthatthemaximumdifferenceinpressurecoefficientsoverthechordwiseextentsofporousareavariedinthesamemanner,thedifferencesbeingoftheorderof 4.25for8 per-cent,1.95for2 Tercent,and0.80for1 percent.
A porousmaterialhavinglessover-allporositywouldreducethelocalcirculationandhencetheinitialdropin liftcoefficientwiththebloweroff,butwiththebloweroperating,lsrgerpowerrequirementswouldbe needed.
Afternotingtheinitialdropsin liftcoefficientobtainedonpreviousconfigurations,configuration(f)(last1 percent)wastriedinan effortto reducetheinitialdropwhilemaintainingsomeoftheaddi-tionalliftdueto suction.Figure10showsthatthemaximumchangeinpressurecoefficientforthisconfigurationwouldbe oftheorderof0.18as comparedwith0.80forconfiguration(c)(first1 percent).Fig-ure9(e)showsthattheinitialdropin liftcoefficientwaslessforconfi~ation(f),aswasexpected,butthatno subsequentgainin liftcoefficientwithsuctionwasobtained.
Anotherpointworthnotingisthatacoefficientoccurredwithairplaneengineenginepoweroffand,generally,a higherrequiredtoregainthisinitialliftloss
largerinitialdropin Mftpoweronthanwithairplanevalueof flowcoefficientwaswithairplaneenginepoweron.
A comparisono,fthevariousdatapresentedinfi~e 9 indicatesthatnoneoftheleading-edgeconfigurationstestedwasclesrlysuperiorwithregardto increasingthemaximumliftcoefficient.Althoughtheincrementin liftcoefficientfora givenincrementinflowcoefficientwasgreaterforsomeconfigurations,theinitialdropin liftcoefficientwasgenerallylargerforthosesameconfigurationssothatthemaximumliftcoefficientwiththemaximumsuctionavailableremainedmuchthesameformostoftheconfigurationstested.Hadthesesameextentsofporousareabeentestedon a sharp-nosedairfoilwhereleading-edgesepa-rationismorelikelyto occurthanwiththerelativelybluntleadingedgeoftheNACA2412airfoil(seefig.l(d)),theresultswouldundoubtedlyhavebeenmuchmorefavorable.
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Itwillbe notedthattherearethree“fun 8 percent.” Thedataof figure9(a)
NACATN 3062
partsoffigure9 labeledwereobtained~ustafterthe
installa~ionoftheadditionalleiding-edgestiffener-andthoseof fig-ure9(g)wereobtainedduringa flightinrainmade184daystotaltime,18hours9 minutesflighttime,afterthatforfigure9(aJ. Thedataof figure9(h)wereobtained2 daysaftertherainflightforcomparisonwiththerainflight.Becausetheintensityoftherainvariedfromadrizzleto ratherheavyrslnduringtherainflight,notverymuchcanbe gainedfromsucha comparison.Onepointwhichappesrsworthyofco~arison,however,isin connectionwiththeinitialdrop h lift coef-ficient.Thisinitialdropis lessfortheraindata(fig.9(g))thanforthedry-airdata(fig.9(h)or9(a)).Thisdifferenceistobeexpectedinasmuchastheraintendsto increasetheover-alldensityoftheporousmaterialandthusreducesthelocalcirculationthroughit.
l?iguxes9(a)and9(h)providea bettercomparisonsincethecondi-tionsweremoresimilar.A totaltimeof 186days,a flighttimeof19hoursk6minutes,occurredbetweentheflightsfromwhichthesedatawereobtained.Theonlymajordifferencebetweenthesedataisthegreaterinitialdropinliftcoefficientforthedataof figure9(h).Thisdifferenceisprobablya consequenceofthehigherporositywhichexistedforthelasttestsmade[seetests8 and9, fig.5).
Earlytuftpicturesshowedthatthestalloriginatedatthetrailingedgeofthecentersectionwithpoweroffandjustinbosrdoftheaileronswithpoweron. Configuration(e)(centersectiononly)andconfigura-tion(g)(outboardsealed)weretested~ ~ attemPtto ~luence theoriginofthestallbut,asis discussedsubsequently,thetestswereunsuccessful.h obtainingdatawithconfi~ation(d)(fi$=9(d))~aseverevibrationoftheleadingedgeontheotierpanelsoccurredwhich,forthemaximumblowercondition,couldbe seenwiththesldofa mirrorandcouldbe heardoverthenoiseoftheairplaneengineandtheboundary-layer-controlenginesndblower.Theresultingpressurerecordsweresuchthatnovaluesofflowcoefficientcouldbe obtainedforthemaxim.m-blowerconditionand,therefore,estimatedvaluesofflowcoefficientswereusedforthiscondition.Thevibrationoftheleadingedgewassoviolentthatthepilotandengineer-observerdeemedit advisabletoterminatethemaximum-blowertestsbeforecompletion.Thepressurerecordsindicatethatthevibrationcontinueddownthroughtheblowerspeedrangebutwithmuchreducedviolencesothatitcouldno longerbe seenorheardandthepressurerecordsbecamsreadable.Apparently,thesealedouterductsactedas closedorganpipesandreinforcedthepressurepulsesoriginatingattheblower.Thevibrationoftheleadingedgemayhavebeenat leastpa$tlyresponsibleforthelossof liftwithincreasedsuctionshowninfigure9(d).
Thedataforconfiguration(g)(outboardsealed)showninfigure9(f)areverysimilarto datafortheoriginalfu~-8-percentconfiguration “
NACATN 3062
of figure9(a)exceptthatslightlylessandtheliftslightlygreater.
J-3
theinitialdropin liftcoefficientiscoefficientsatmsximumblowerspeedare
Comparisonof flight andwind-tunnelresults.-A comparisonof someresultsfromtheflight-testinvestigationwiththosefromunpublishedtwo-dimensionalwtid-~el dataobtainedbeforebeginningtheflightinvestigationis showninfigureIL. Thewind-tunnelmodelwasa 36-inch-chordmodelof theNACA24I2airfoilsectionwitha porousnoseconsistingof filtercloth,similartothatusedontheairplane,backedwithsin-teredbronzeforstiffness.W@d-tunneldatawereobtainedat a speedof78.5mph. Fortheparticularresultsshown,thenoseofthew@d-tunnelmodelwassealedfromtheleadingedgetothe0.4-percent-chordstationandwasopenforthenefi7.3~ercent.Thiswind-tunnelconfigurationwastheonenesrestthe8-percent-openconfigurationusedontheair-plane.Theflightdatausedwereobtainedwithairplaneenginepoweroffandfhps Up. A comparisonof leading-edgeporositiesapplicableto theflightandwind-tunnelresultsisshowninfi~ n(a). Thecme forthewind-tunnelresultsrepresentsonlya smallportionofthevelocityanddifferentialpressurerangetested.Thetwoeetsofdataarecon-sideredtobe in goodenoughagreementfora reasonablecomparisonofaerodynamicresults.Figuren(b) showsthevariationofmaximumliftcoefficientwithflowcoefficienttobe ofthesameorderofmagnitudeforthetwosetsofdata.Theinterceptofthewind-tunnelcurvewithzerosuctionwasnotavailablebutthetrendindicatedbythedashedlinewasestimatedfromotherresultsfromthesameinvestigation.Thetind-tunneldatashowa netgainin liftcoefficient(fromthesealedcase)of only0.25attheoptimumvalueof CQ = 0.002. An interestingobserva-tionisthatalmostthesameincrementin liftcoefficientwasobtainedin flightwiththemaximumavailableflowcoefficient,althoughthetrendindicatesthata largerincrementin liftcoefficientwouldhavebeenobtainedhadhigherflowcoefficientsbeenavailable.
Tuftpictures.-Figure1.2showsa typicalfrsmefromtuftphoto-graphs.Thisframewastakenduringtheflightwiththeleading-edgeconfiguration(b)(first2 percent)in a semistalledcondition,withpoweroff,andwithflapsdownatthemaximum-suctioncondition.Asmentionedpreviously,thetuftpicturesweretakenby a csmeramountedaboveandbehindthewing,facingrearwardandupward,andshootingintoa sphericalmirror.Althoughtheuseofthesphericalmirrorresultedinappreciabledistortion,itwasusedbecauseitpermittedanimageoftheentirewingtobe obtainedwitha singlecamera.Thechordwisestripsonthewingwere27.25inchesapart(approximately12.5percentofthesemispan).
Stallpatternsweresimilarfora givenpowerconfigurationregard-lessof leading-edgeconfiguration,amountofsuction,orflapposition.In general,thestalloriginatedattherightsideofthecenter-section
.___— .—.—— ——- — --—-—, —-—— .——————----—- ———-——————
14 NACATN3062
trailingedgewithpoweroffandatthet%ailingedgejustinboardoftheaileronswithpoweron. Thestalledsreasspreadforwardandspanwiseina triangularfashion.Suchdifferencesin stallpatternaswereobservedcouldnotbe definitelycorrelatedwithflapposition,leading-edgeconfig-uration,or smountof suction.
CONC17JDINGREMARKS
Resultsofthisinvestigationhaveindicatedthat a practicalwinghavingporous-leading-edgesuctioncanbe constmctedwhichhassufficientstrengbhanddurabilityforuseinflightwithoutaddingexcessiveweight.Forthetypeofporousmaterialusedinthisinvestigation,cloggingdueto atnmsphericdustdidnotappeartobe a problem.Forthelightrainencounteredinflight,thepowerrequiredto producea givenflowcoef-ficientwasabout50percentmorethanthatrequiredforthedrycondition.Bssedonthegrounddata,itwasestimatedthatforflightinheavyrainthepowerwouldbe approximatelytwicethatforthedrycondition.Atmsximumblowerspeed,however,theporousareabecameclearedwithin3 to4 minutesafterwaterceasedto impingeonthesurface.Undercertainconditions,testsshoweda severevibrationof theporousmaterialinducedby w “organpipe”resonanceoftheanticolumnwithintheducts.Asexpectedfrompreviouswind-tunnelresults,theuseof leading-edgesuctionwiththesmallamuntofpoweravailableandwiththewell-roundedairfoilsectionused(NACA24I2)hadMttleeffectonthemaximumliftcoefficientdeveloped.Ingeneral,an appreciabledropin mximumliftcoefficientoccurredfromtheleading-edge-sealedconfigurationto theconditionofzerosuctionwiththeporous-sreaconfigurationstested.Incrementsinliftcoefficientdueto thesuctionavailablegenerallybroughtthemsxi-mumliftcoefficientbackapproximatelyto thevalueforthewingwiththeleadingedgesealed.Themaximumtheoreticalaerodynamicpower,ifductlossesareexcluded,variedwiththeconfigurationstestedfrom3.65to9.70 horsepower.
LangleyAeronauticallaboratory,NationalAdvisoryCommitteeforAeronautics,
IangleyField,Vs.,October26,1953.
“
NACATN 3062 15
APPENDIX
ESTIMM’IONOF LEADING-= SURFACEPRESSURE
Sincenowingsurfaceorificeswereprovided,thedivisionofthetheoreticalaerodynamicsuctionpowerrequired(calledusefulpowerhereinforsimplicity)intopowerrequiredto overcomeporous-materialdragandpowerrequiredto reduceductpressureto averagesurfacepres- .surewascalculatedinthefollowingmanner:Thepressureintheduct PIforbloweridlingandwithexit-ductshuttervalvesclosedisassumedtobeequaltotheaveragepressureovertheporousarea p atthesamevalueof liftcoefficientwiththebloweratmaximumspeed.Inordertodeterminetheaveragepressureovertheporousareaat somehighervalueof liftcoefficientwithbloweroperating,thispressureisexpressedintermsofpressurecoefficientS by meansoftheequationS = (% -P)/qcwhere ~ and qc arefree-streamtotalandcalibratedimpactpressures,respectively.Thepressurecoefficientis correctedtothepropervalueof liftcoefficientby themethoddescribedbelowandthenewsurfacepressuremaythenbe calculated’.
Theprocessof correctingforliftcoefficientconsistedof calcu-latingtheoreticalpressurecoefficientsforthewinguppersurfaceatvariousvaluesof liftcoefficientobtainedfromdatainreference5,integratinganddeterminingtheaveragepressurecoefficientoverthefirst8 percent,andplottingtheseaveragepressurecoefficientsagainstliftcoefficient.Thepressurecoefficientdeterminedfromflightdatawithoutsuctionis locatedonthisplotat itscorrespondingliftcoef-ficientanda curveparalleltothecalculatedtheoreticalcurveispassedthroughthetestpoint.Thepressurecoefficientattheliftcoefficientformaximumblowerspeedcanthenbe pickedfromthisnewcurve.Withthesurfacepressurep thusdetermined,thepressuredifferenceacrosstheporousmaterialis
AP=P- P1
andtheiniti”alpressuretobe overcomeby thebloweris
~-p=sqc
Theseequationsarebasedontheassumptionthatthedynamicpressuredoesnotassisttheflowtopassthroughtheporousmaterial.
——— .—..-—— — ~—— -—- ———
ItEFERmms
NACATN 3062
1.Jones,Melvin,andHead,M. R.: TheReductionofDragby DistributedSuction.ThirdAnglo-AmericanAeronauticalConference(Brighton),Sept.4-7,1951,pp.199-230.
2. Raspet,August:BoundaryLayerStudieson a Sailplane.PreprintNo.348,S.M.F.FundPreprint,Inst.Aero.Sci.,Jan.-Feb.1952.
3. Miles,F. G.: SuckingAwaytheBoundaryLayer.Flight,vol.X#Pl,no.1570,Jsn.26,1939,PP.82b-82d.
4. Henry,JohnR.: DesignofPower-PlantInstallations.Pressure-LossCharacteristicsofDuctComponents.‘NACAWRL-208,1944.(FormerlyNACAARRL4F26.)
5. Abbott,IraH.,VonDoenhoff,AlbertE.,andStivers,IouisS.,Jr.:~ ofAirfoilData. NACARep.824,1945. (SupersedesNACAWR L-560.)
3X17
----- -- ——. -—.-. .-—. —.—-— —— .—-—-. —I’ABM lo- lJWSIUNAL
approximatetake-offweight,lb . .Horsepower(at2,200rpm). . . . .Propellerdiameter,ft . . . . . .Over-alllength,ft . . . . . . . .
wing:Area(includingfuselage),sqftSpan,ft . . . . . . . . . . .Dihedral,deg. . . . . . . . .Aspectratio ... . . . . . . .Taperratio. . . . . . . . . .Meanaerodynamicchord,ft . .Incidence,deg . . . . . . . .Washout,deg . . . . . . . . .Airfoilsection. . . . . . . .Flapsrea,sqft.... . . .Aileronarea,sq ft . . . . . .Flapdeflection,down,deg . .Ailerondeflection,deg. . . .
Horizontaltail:Aspectratio . . . . . . . . .Totalarea,si ft...... .Stabilizerarea,sqft . . . .Elevatorarea(lesstab),sq ftElevatortabsrea,sqft . . .Airfoilsection. . . . . . . .
.
.
.
.●
✎
✎
✎
✎
✎
✎
✎
✎
✎
✎
✎
✎
✎
Taillength(centerof gravitytoElevatordeflection,deg:up . . . . . . . . . . . . . .Down . . . . . . . . . . . . .
Elevatortabdeflection,deg:up . . . . . . . . . . . . . .Down . . . . . . . . . . . . .
Incidence,deg . . . . . . . . .
Verticaltail:Aspectratio . . . . . . . . . .Totalarea,sqft . . . . . . . .Finarea,sqft . . . . . . . . .Ruddersrea,sqft . . . . . . .Airfoilsection. . . . . . . . .Rudderdeflection,deg . . . . .Taillength(centerof gravitytoFinoffset,deg...... . . .
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elevatorhinge,
. . . . . . . .
. . . . . . . .
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.,
. . ●
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✎ ✎
✌
✎ ✎
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.
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.approx.),
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. 3,830
. .
. . 7%
. 27.10
. 218.u
. 36.17
. .
. . 6:;:,. 0.62. . 6.30. . 1.0. . 1.5NACA24ti. . . 8.68. . 12.32. . . 45. . . 95
. . .3.16
. . 35.20
. . 19.79
. . 14.660.75
“i& 0006ft. 18.0
.0 . 31.5
. . . 13.5
. . . .
. . . . E
. . . . -4
. . . 0.88
. . ~6.55
. . . 8.78● 7.77
“N~CA0006. . . Wl
rudderhinge,approx.),ft . . 18.3. . . . . . . . . . . . . . . . . 0
aDesigngrossweightof originalairplsne,lb . . . . . . . 3,350
. ..— -——. .———-- — — — ...—————— –— —-——. -——
TABLEII
COMPOMEMTWEIGHTS
[Allweightsinpoundd
Poroussurfaces:Total. . . . . . . . . . . . .Centersection. . . . . . . .Eachwing. . . . . . . . . . .
Completewingwithboundary-layer(includingporoussurfaces):Withoutfuel . . . . . . . . .%ith 61gallonsfuel . . . . .
Completewing,originalairplsne:WithoutMel . . . . . . . . .With76gallonsfuel . . . . .
. . . . .
. ...*
. . . .
control
. . . . .
. . . . .
. . . . .
. . . . .
.
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.
.
.
Boundary-layer-contnlequipmentinfuselageEngine . . . . . . . . . . . . . . . . . .Blower . . . . . . . . . . . . . . . . . .Gearbox . . . . . . . . . . . . . . . . .Mount. . . . . . . . . . . . . . . . . . .Ducking. . . . . . . . . . . . . . . . . .Accessories(coolingandlubrication,etc.)
Instrumentation. . . . . . . . . . . . . . .Instruments. . . . . . . . . . . . . . . .Batteriesandinverter. . . . . . . . . .Wingbooms(includingpickupheads). . . .Csmera,mirror,andmountingstructure. .
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Mountingboards,cables,relays,tubing,etc.
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. 15.0
403.25769.25
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295.5751.5
458.8153.078.842.347.330.0
107.4
%Cheductingnecessitateduseof smallerwingfueltanks.
.
NACATN 3062 19 ●
TABLEIII
POROSITYTESrs
.
.
@l por..itytestswererunonthegroundwiththeleading-edgeconfigurationlistedinfigurekascotiiguration(a)(til8percentopen)~
Flighttimesince~otdthe SticeTest previoustest previoustest, Remarks
HoursMinutes days
1 0 0 Madeatbeginningofprogram
2 11 53 89 AI1flights,fuu8percentopen
3 13 41 11.3 Divisionofflighttimeasfollows:7’hr43rein,u 8percentopen1hr02ti, completelysealed2hr51rein,first1percentopec2hr05rein,first2percentopen
4 0 0 Removedalltapeandcleanedbyrubbingsurfacewithlhcquerthinneroncloth
5 0 0 Sprayedsurfacewithprep-sol
6 0 1 Sprayedsurfacewithbenzene
7 0 28 Additionalstiffenersinstalled;sprayedcarbontetrachloridethroughbothsidesofporousmaterialwhileremwedfromwing
8 17 43 32 Divi_sionofflighttimeasfollows:k b olmin,tiIJ.8percentopen2 hr41rein,first2percentopen3 kc39rein,firstlpercentopenOhr51*, leadingedgesealed1hr42rein,centersectiononlyopen2h 21rein,last1percentopen2hr33rein,outboardsealed
Limitedattemptsatclean~.madebetweenflights
9 7 00 169 Approx.l&r inrainofvaryingintensity;fu~8percentopen
50 17 431
—— .——- —
Leading-edgecotiiguratIon
Full 8 percentopen
First 1 percentopen
First 2 percentopen
Laet 1 percentopen
OutboerdsealedFUll 8 percentIn rain
)~1 8 percentopen
Blower
L
[
blaxiuruJn2/31/3
Minimum
M.xilmlm
Keximm
MEMmlLl
Mawnurn
0.275,217’.168.054.436
,447
,472
.272
.323
.259
TABm Iv
FW%ER R3mRJlMEN16
0.332 0.0517.282 ,0304.185 .0038.M!4 o.430 ,0302
.39 I .0477
,4$Z? I .OI.25
.366 I .0299
.228 ,0326
.310 .0463
Blnwer)fficiencypercent
.@F!PE4
33.527.0i8.96.0
50,7
53.9
53.0
32.838.9
33.3
Engineoutput,llp
15,812.59,19.0
17.7
16.8
X),7
14,914,7
14.1
Flowcoefficientat btall
o.oo131.00098,00056,00020,00110
.0CQ76
.00114
.00110
.oo1.13
aBlowerveriationfB de6cribedaccordingto an approximatevariationof rotationalspeed.
%hee titswere obtainedat end of fll~t promem after flightin rain and are presentedforcomparisonwith otherdataobtainedearlyin-fll-@t-programfor .&e conflgmation. -
!2
II
I
I
I
I
I
1
I
.- ..-.“.- r--r —-.
:. -—
* 1 I,,.;”--
k ?’
::._&~=.=_5 ‘ --’-~’~=%. -
-%.. .->.$+. “L :7,
..?_* ‘“’ ~.. -.. ‘t-i- “-- 7--”(_&----___L-z= ..,.,.*...ZEG=5r“--”’ -2— .. ..-.
-. --- --e.. ,.. -
I—. . -. ..i
(a) one-quarter front view. 11-70267
Figure 1.- Ce6ma 190airplaneusedforflight teats.
23
t---- ‘0”541,,
.——. —.
-hr’4.70
———————740
Z_All dimensions in feet
— 36.17~
< , — .........+- —_/
( (’
-15.33~ 2710—
L
o
(c)Three-viewdrawing.
Figure1.-Continued.
. .. ——.—.—. ——. —— —.— -—— -— —~ .— —..
%ln bp ]dnt0.033h thlok
NACA 2412 Profll>
Q Rivub tn mnln mar(all t’M I’IW8 ahead Of rm!n fwtl
.—
(d) Cmparison of actual wing profile with NAC!A241.2profile,
Figure 1.- Concluded.
4xNACATN~62 25
3Xhaustduct
/. —
\ / ~ edgeducts
Main ductExhaustduct= Centerduct
Blowerexit~ <*
BlowerEngineexhaust
GearboxEngin#
loEnginecoolantradiator
(a)Sketchof equipmentinstallation.
Figure2.-Equipmentinstallation.
.—_—... —— ——..— —._, _.. — -—-
Ncm
.~1 %<, ‘“,
,’ I \-‘., . .e
I i. ~— . .. . . .
L-67926(b) Leading-ei@-duct s+ructure.
Figure 2.- Conttiued.
,
IJ
I
“L. “ .–— —h . . . .
‘r1’
--”’—— --—.._.,, !(e) Ri@t-mti-duct IasGtion. L-67931.1
Figure 2.- Continwd.
I
NACATN 5062 31
IF\\,
L1.,: ,i‘j1,:
k)L-7027001
Mgine-blower installation.
Figure2.- Concluded.
I
.-2
I
— — ..— — —.—— ———. —. —-. —.— .——
32 NACATN 3062.. .
-----
t’ I-,
,“,; ,; ..”. ,. .- -. - .
.
(a) Normal.L-72837
-L -. :, 5, .’., >,,?,- \.* ,-’ “.-. *’ -‘mk
. . 1.:.-. .’ --- -. —-,
-“ .. ----~1
. . Ir I
L-72838(b)Collapsed.
Figure3.- Effectof suctiononunstiffenedleadingedgewithonlyfirst2 percentofleadingedgeopen.
—
5xNACATN 3062
w
LJ
w
w
cmfigurathl
(a)M 8percent
(b)FWst 2percentopen
(c)m’st1percent‘open
(d)Sealed
(e)Centersectiononlyopen
(f) Last 1percent
x/c
0.08
.@
.01
0.
.08
.01
(d Wtboti ‘ .08sealed
a-b
O.w
.@
.@+
o
.115
.W
.548
sA’/9A
0.892
.@
.892
0
.145
.=
.627
Figurek.-Porous-leading-edgeconfigurationstested.
33
%/S*
o.081
.029
.018
0
.012
.008
.057
— —. —____ —.-. — —. -——. —
34 NACA‘IN3062
1.6
●2
o6 4 8 12 16 20
Pressuredifferenceacrossporousmaterial,Ap,lblsqft
Figure5.- Variationofappsrentvelocitythroughporousmaterialpressuredifferenceacrossporousmaterialfromgroundtests.edgeconfiguration(a) .
24
withLeading-
NACATN 3062 35
194
1.2
1.0
.0
.6
.4
.2
0
1~~~ Condition / c ‘ I stall
/IO Flight Wet /‘ -[
❑ Flight Dry / /’ I~ Ground
iWet //’f /
/K~tiated] ~A Ground Dry,.’j tren* /
/ \/
I 1/ t
/I I
/r I // f /
/ //
I /JI I
LA / / /’/ .EstinAtedaverage/
Ilocalpressure
/ ~erp,r~~,ea~gI /“edge t/ {
& //1/‘
/
/’/
;/
o 20 40 60 80 100 120
Fressuredifferencebetweenfreestreamandduct,P.- PI>~/sqM
Figure6.- Effectofrainonporosityofporousleadingedge.Leading-edgeconfiguration(a).
——___ ________ —.— —— -——...—.—
1.4
1.2
1.0
.8
.6
●4
.2
0
Figure
TEstimate
*, sec
_8
5Initiallywet >
l.ydrII
trendduring /’“engineacceleration /
d’/
/’
//
/,/
/
//
●M
0 20 40 60“ 80 100I@ SSUI% differenceacrossporousmaterial,Ap ~ lb/sqft
7.- VariationofapparentvelocimthroughpressuredifferenceacroSsporousmaterial~dLeading-edgeconfiguration(a).
porousmaterialwithtimein seconds.
—
1. Porous material drag 1.34hp2. power to reduce duct pz?essure 2. 0 hp
$. Duct losses - i. Blower losses
2
9:6: k:. Gearbox los~es .30 hp. Power for accessories
7. Total engine output M ““ ‘,.
Theoreticalaerodynsniopower )+.OL’hp
Figure 8.-Estlruateddistributionof input power for the gkhiing conditionwith rmdnnm blower at the stall. Leading-edge configuration (a).
38 NNA TN 3062
LeadhgLeading-eem Ymnf&araton
sealed llatd Power Flaps
z.4
.8
2.4
.8
Q
0 .- .0008 .Omz .0016mm 00emOlmt,cQ
o .@ .0008 .0012 .0016FlowOOetfiOlent,CQ
o❑
oA
Gll upon kml
off up
off Ik.m
0 .C@ .0008 .001.2 .0016Flow008ff10i.3nt,CQ
0 .Ood+ .0008 .Oolz .0016FlowaOefftOWlt,cQ
.
Figure9.- Variationofliftcoefficientatthestallwithfluwcoefficient. -
—
NACATN3Q62
LeadingLeading-edgeedm confluuatlonae~ed li:ted PowerFlnp,g
Q
.8
0. .000!! .Oooa .00I.2 .0016plowOOeffialent.C~.
0 .CfJd+ .0008 .Oolz .0016MOTc04fflclent,cQ
Gnup
cm DOml
off up
off Ikn’n
2.4
.8o .Oool+ .0008 .oo12
FIow ooeffioient,~
.om6
.,
Figure9.- Concluded.
o .oo@ .0008 .0012 .om6plo=ooeffialent,~
. .. +-— -—-—— ._ .——. . .. —.—— —.. —
40 NACATN3062
9
8
\
7 L
6 \
m
;5Most rearward extent
: ofporousarea2a
;bm
1!
3
2
1 , .
0 .02 .04 .06 .08 .10Chordwi.sestation,x~c
Figure10.- TheoreticalchordwisepressuredistributionovertheuppersurfaceoftheNACA2412airfoilat a liftcoefficientof1.6.
.
.
.—
6XNA.CATN 3062
Figureid..-
/Elight\
/ (a)porositydata
o 8 16 & 32Wessure differenceacrossporousmaterial,Ap, ~b/8qft
1.8 1 1 1Poweroff,flapsup,leading-edgeconfiguration(a)1 1 1
IIU-1.6 Porous
leading !e“ edge ~ghtC -.; sealed
z!% ‘wind tunnel: l~c
5
El c
i1.2
‘1
I(b)Aercdgnamicdata,
1*OI I I 1 I 1 I 1
0
Comparison
3
.001 .002 .003 .ooI#Flowcoefficient,CQ
ofresultsofflightandwind-tunnelinvestigations.
-———-— ..— —— ———.