______ __ ______ –i

~ . .eNATO’!+~ ADVISQRY COMMITTEE FOR AERONAUTICS

WAlrm!m IuwomORIGINALLY ISSUEDNovember 1941 as

Advance Restricted Report

WIND-TUNNEL TESTS OF EIGHT-BLADE SINGLE- AND

DUAL-ROTATING PROPELLERS IN THE TRACTOR POSITION

By David Biermann and W. H. Gray

Langley Memorial Aeronautical LaboratoryLangley Field, Va.

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. . . ..-. ,,, ,,, W&HINGTON 9,, ,.* ~fitilyll 46’s!JO:st>l$tim. .. .

NACA WARTIME REPORTS are reprints” of papers originally issued to provide rapid dist~ibution ofadvance research results to an authorized group requiring them for the war effort. They were pre-viously held under a security status but are now unclassified. Some of these reports were not tech-nically edited. All have been reproduced without change in order to expedite general distribution.

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-DUAL~RO@ATII!G P3QP~L+F@S. IIT,TJO! TRA~10R%S191’01!7.. ...-. . .. ... ./ ..:. ..k... .9 .- . . .. ..

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Tests of lCJ-foot dianeto,r”,.e.~ght-blade siu~le- anddu.ql-.rotqtlng propelle~s.were c“o”nducte”~in the 20-foot“propellerJr&search. tunnel as a cbqtitiuatlon of a previousinye6t$gation of four- and six-blade ”propellors. The pro-.zeZ1.ers wprb nount”od at the front ond of a streamline body

. in #pinners that i?overed the hubs and phrt.of the shanks.“Tho .efftict of a synnetr”lcal wing no”im%od In tho slipstreamwas invo~tig”ated.. ,BlaCo-a.nglo so~ti:fngsranged fron 20° to65°. ..

~TQo result~ Indicata that dual rotation rosultod in. . ~ins of-l to 9 porcont in ‘bfflcioncy ovor slnglo rotation

for~oight-blado :propollors, .but tho prosezlco of a wingr,odu.ced th~ gain BJ- about ono-halfm Also indicated was agroator ljo-iorabsorp,tlon due to dual rotation over tho cn-tiro flight range, and high.~r offlcionc~ or thrust for theradgo of take-off and c1:u?). ‘.,

. .INZ!RODUCTTOIT “

,.

A report prov.iously ~oleasod (roforonco 1) prosontodresults of tests of four- and’slx.~blade dual- and singlo-rot..ati.ngtractor propollors. Tho .proson% rophrt doscribos

.. tho results of a suh~o.quqnt investigation of eight-%lados~n.gle- atid.’dual-rutatin~ propellers mounted In the trac-tor pogition on %he. sane se.t-up’as that” prevlo.usly used.The effe~t. of a eynnetrical v~hg hounted in the sli.pstreanwas incIuded in thq ~nv~stighttoq.as heforo... .+ . . .. .

,. . . .. ‘. . . .A:PPAEL4~US..A~.HfiTHODS . . .

...-

Inasnuch as the present investigation is a continua-tion of one previously nade in tho propeller-rasearch tun-nel (see reference 1), a detailed doscriptlon of the appa-

L .—...—.- .— —.

... ,. . . . . -. “ ,. . >.. .

2 .. .

.. . . ... . .... . .. ... -....

ratus and uethods will not .be.r?pqatod. .~oro. 4 short dQ-soription is included, howover, in o.rilorto”nako this re-port fairly oonpleto within itself.

Propellers.- Both the eight-llctdb single- and dual-rotatlng propellers were nounted in four-wny hubs spaced

9= inches atiar.t(see figs.”1 and 2), thereby providing.

identical :blade shank and spinner conditions. Preliminarytests, were”nade to detorninb the optinuatmgular dl.splaco-uen.t ‘oet.weon tho front and rear propoller”blmdos for the .“singlo-rotntion tests; the blades of the front propollerwere” .”aptto ldr.d *Ro blntks of *ho rear. propeller by.75°,

52~”* and 3“0°. Although the results “indicnted little dif-

ference between these three spr.cings, “the 52~0 spacing w’aeconsidered the best. Equml spacing of 45° was not possi~leowing-.ko m liaitatio”n inyosed by the &c.ft spline~ ..... . .

~h”e bl~d6s use~d for tl.is-“present inve~tigation “wera the.snne as previously t.ested,”naawly, Hr=iltom Standard 3155-”6and 3156=6, right-hand~npd left-hands respectively.. ~ladb-.fern..curves nre given in figure 3. Clark Y sections me ..incorporated throughout.

.,..

Test condition s.- Because of the linlttng tunnelspeed (approxinatel~ 110 ~ph)-and. the liniting power ofthe drive rotors (two 25 hp electric notora), the Reynoldsnuaber ~nd the tip speed were consi.d.ernbly lower thanthoso experienced in flight. The naxinun propeller speed,which was 550 rpn, was obtainable oqly for the low. blade .angles nnd the low V/nD range of the tests.. The t~pspeed, consequently, was below 300 feet por second,. and “thus tho offoct of conpro.ss~bility could not Wc neacuro~. “-The Reynolds number of the 0.75R section wa?” only of the “ -order of one nillibn. The eff.ectzof Reynolds.nunber wasnot critical within.the rmnge” o.f the tests.as the eff.botof chnnges between one-half nlllion and one nill”ion “couldnot be netnsured~

.. . .

The left-hand (front) propeller w~s set nt even val-ues of blade setting for the duml-rotation tests~ Theright-hand (ronr.) propoller was sat to nboorb tho snyppower as tho loft-hhnd .propellor for “only tho.peak offi-cioncy condition.” A plot of. tho qngulmr diffb.ronqe bot.woo”ntho right-hand nnd tho loft-hand propollor-blndo settingsis gl.von in flguro 4. Tho spocd of tho right- nnd tholoft-hand propollors was naintainod oqunl throughout tho

-..

31

tosttlm Tho test proooduro “was”~ho smno as that used for“previous tnvostlgations in this tuanol. ...-----

R3SULTS MD DISCUSSION. .

Tho noasured values havo boon roducod to tho usualcooffi.cionts of thrust, powor, and propulsive offi.ci.ency.

. .

CT = effoctivo thru.s~

p n= D*

.“,.

..

pv 5ca=—

Pna . .

whore tho effoctivo thrust is tho noasurod thrust of thopropellor-%ody combination plus tho drag of tilo boil~aoasurod 6eparately.

D propeller d.ianeter, feet

n propeller rotational speed, revolutions“ per second

P aase density.o.f -the air, slugs per cubi.o foot. .

These coefficients yese plottod against ?/@l. Theresults are given in th~ folloving figures:

l?igures.“. .,.. . .

5-7 C“hatimdteristic curves for eight-blade propallQr,“ single rotation without ving

. . . ... . . .8-11 “ Characteristic”” curves four eight-~la{!e propeller,

dual”rotation without wing -

12 - 15 Characteristic curves for eight--blade propeller,single rotation with wing

—-—. . . ., . . —-..-,.——, .,. .— —

4

Figures(Cent .)

16 - 20

21

22 - 23

24 - 25

26 - 27

28 - 29

30 - 32

33

The

Characteristic curves for eight-blade propeller,dual rotation with wing

.Ratio of power cooffictents por %laEo for oight-

and throo-blado propeliors

Characteristic curvo co=p~.riso~s showing effectof snail variations la roar blado-nnglo sot-tlng

~fficioncy oavolopo comparisons for olght-bladopropolzors

Efficionc~ onvolopo coapnrlsoas of four-, sIx-,and eight-hln?o pz*opollors

Incrononts of officioncy resulting fro= clualrotation

Effect of dual rotation on efficiency for con-stant powor coofficionts

Effect of clual rotation on thrust

general characteristics of eight-blade single-anil i%ual-rotating propellers, shown in figures 5 to 20,indicate that the ~rinclpal effect of the increase?. solid-ity oTer thr.t for the four- r-m!.slx-bla’?.e propellers re-ported. In reference 1 was increcseC total po~!er absorption :with little loss in blade efficiency.

Effect of ?.uml rotztion on totr.1 power mbsorbe~.- Of—..—pcrtioulr.r interest is the feet that tho ‘1.UCL-5 otatingpropellers absorbec!. npprocinbly core power thnz Lid thesingle-rotatin~ one, as ZQT be note?. In figures 16 to 19,wherein the characteristic Curyos obtainod for sovoral ,nn-glo settings for single rotation nro ouporizposo<. on thosefor dual rotnt~on. Qhis increase.1 ~;owor absorption cay bor.ccounto~”.for h7 the fact that tho front propollor lntro-(l.ucodc rotational co=ponen+ to tho sltpstrocn, which in-croaso~ tho ro.sultant velocity over the rear propelierblad~s. This rotational conponent is greatest when theblat!. elenents neet the relative nlr with the greatest an-gles of ~.ttack, so.the effect was TLore noticeable at lotrV/nD values than for the high T/nD values. This in-

5

creased power-absorption characteristic of dual-rotatingprbpellews is one-explanation ~Qr their. re+su-lt~,ngsuperior

“.take-off qualities, owing~.to the faot that for this condi-tion the pitch Is reduced to a-lower value than for si.ngle-rotating propellers. .. . . . .

A comparison is nade in figure 21 wherein the power -absorbed at,peak efficiency per blade,~.relative to thatfor” the blades-of a three-blade propeller, Is”presented”for” both single- and dual-rotating propelierso This pldt~ndicates that the effectlveaesg of each blade of the dualpropqller in absorbing.power was spbstant.lally”~ore thanthat for a single-rotating propeller; the individual bladeeof am eight-blade dual propoller absorbed approzl=ately 87

... percent aa Euch pQwor aa each blade of s three-blndo singlepropeller, as conpnred. to only 60 percent. for an elght-blade eingle propeller. .

..E<fect ~ dual rotation on U.ower a%s.orbed by—-..— rear pro-

ueller..-. The dual-rotation teats wore conducted d.th’therear propeller set at a slightly lower afigle than the frontone in order” to e~umlize the power for the peak efficiencycondition. The rear propoller ahsorbed”uoro power”than thefront one at Lower V/nD values than those for peak effi-cioncyw ““A few tests were nado to daterni.ne the blade set-tings of the rear”propeller nocesiarjr to.produce equalpower absorption;” the results of theso tests me shown infiguree”22 and 2S. Whether there Is any .kerodynanlc nd-vantnge In oquallzing the power of the two propollors forthe take-off and. clinbtng condlti.ons of. fllght cannot bodetorninod”:fion the~o tests becnuso.direct efficiency con-pnrlsons &unaot be made” on a baai~ .of equcl p“ower absorp-tion. “ ‘.’ . .

..-. . .Envelope officlency conparisonso- The same general

improvement in efficiency due to dual rotation .may be notedIn figure 24 for the eight-blade propellers as for the .earlier tests of four- and six-blade propellers. The gainIn efficiency due.’to dual rotation, without the wing,ranged from about. 1“ to.8 percent, depending upon the bladeangle or :V/nD, which la somewhat greater than that meas-ured in the four- and. siz-blade.:tes$s~ The gnfns woreeomewhat less with the wing In pl.nce, owing to its effectin reducing the rotational losses for thp:singlb-rotntingpropeller. The wing appemred to have u sllght beneficialqffect on the dual propellers,.ms may be noted.in figure25. This same effect, which is not easily accounted for~was ELISO indicated In the earlier tests of the four- andslz-blade propellers. ..

6

.. . .

In figures 26 an&”27~ akti “eli”ow& the envelope efflcienoycurves for the present ‘eight-blade”,propeller”s and eurveafor four- and six-blade propel-ler~, obtained from referenceZ for comparison. The generel effect of increasing %he. so-lidity for single” sotation without the wing, shown”in fig-ure 26(a), was to reduce the efficiency a few percent overthe V/nD range. The presence of the wing resulted in .“raising the efficiency of all these single-rotating propel-lers nartlcularl.y thoee of highest solidity. (See fig.26(b!.] The loasin efficiency resulting from increasingthe solidity was generally less for dual rotation than. “for-single rotations as ~ay be noted” from figures 26 and 27~ .particularly for the condition without wing-

It should be pointed out that envelope efficiency oom-parlsons for propellers of different solidity are mre of anacademic inte=est than of’practic%l value because of thefact that the power absorption is different for differentsoliditles. Stich comparisons provide a mea6ure of blade.efficiency, or the effect of blade interference. From eng-ineering design considerations the comparisons should bemade on the ‘oasis of constant power. Such comparisons ofsolidity are provi?.ed in reference 2.

The effectsof dual rotation on the peak efficiency”for four-, six-, -and eight-blade propellers are summarizedin figures 28 and 2S: Although the results” are not of .sufficient, accuracy to fiefine differences in efficiency .less than 1 percent, they show, in general, that the gainarising from dual-rotatiag propellers increases with theblade angle or. V/ni), and also with propeller solidity.The gains were somewhat greater for the condition withou”tthe wine than with the wing (7 percent as compared with 4*porcen%, for V/nD of 5.0, eight-blade propeller.). . .

..Efficienc~ an a thrust comuarisdne et constant- Dower.-.-..

~nas~uck as the dual-rot~ting propellers absorbed somewhatmore power at tho same blado settfng than the single.- .“rotatiag propollors, tho offoct of dual rotation on offi-cioncy should h tiasod on equal polror absorption. Compari-sons aro mado In-figwros 30 to 32 for Cp values of 0.2,0~4, and C.6. Substantial gains in offj.cioncy may ho notqdfor the ontlre oporating range, particularly fgr tho take-off condition of propollors oporating et high values ofCp . Thoso.officloncy gains aro translated into thrust .

gains in fi&re 33. Take-off thru~t gains up to 20 Pcq+cent aro indicated for dual propQllors oporating at.a.power

—— .- — —

,.. . .. . ..:”.. . . .. . . . .-,

,. . . . . ..:.

““.:.. . . . .. . . . . . . .. . ..-:. . .“.

. . ;. .“7

.. . . ..-. f.-.... .. .coo ffl.olont . o~ .Oi.6.~ . .schuo”what.. I.osdi.fdr “lower” power coeffi-‘ciont so’- Thls Iacr-oe;se.d,thru.st..may.,-hoiJS.ctiuntod~-for part lylIy tho fact that qud.-tia’~ting pro~~l~bas .a%Eb?%cd moropower than single-rotating onos as montlonod boforo and,consequently, tho blado-anglo sottlngs for. t.hq dual pro- “pollors woro conputod..tb..be souowliat~low.tirthan for sfnglo-rotating pr,qp.ffllors;p.artialarl>.fti?? %ho ‘tako=”e.ffnndclimb conditions. This lowor bLa&o+gl.o”. setting resultsin greater thrust for a given power output, owing to thehigher lift-drag ratios of the elements. Also with dualpropellers the losses due to. sl,i~stream rotatton are great-ly seduced and perhaps elimitiati:ed,.dliichaccounts for alarge percentage of the gain in efficiency.

. . . . .. .. . . . ‘L ,. : . . . ... . . ; ,... .

1...II.: COi~CLU&O~.S “ - ‘ .‘.. .%a . :.-... . . .’. ..

The general effects of Uual..ratmtion ,Q~ propeilerchhbactik~~ht.ice- f“ou.@&-1~’’p”re.ylous.~es:tib.o.ffour- and siz-bla:db p.r-oj01.1m’s tibre’ Stiiil-afi, .Buf$verb-’qore’ ~~onouncedIn the present investigation of eight-blade prope~lere.!Chese effects are listed more specifically in the follov-ing conclusions relating to the present investigation.

1. The peak efficiency of an eight-blade dual-rotating propoller was foun~ to iYo from 1 to 8 percenthi.ghor tha~ that for a corresponding single-rotating pro-pollor, The &ain In efficienc~ depended upon tho hlade-anglo setting, the highor tho settfng t~o groator tho gaintup to a limiting test blade-angle of 65 .

2. Tho prosonco of a wizg in the slipstroan improvedtho officioncy of tho single-rotating propollor about halfas much as was obtainod by moans of dual rotation.

3. An eight-blsdo dual-rotating propollor was foundto absorb substantially noro powor at porik officioncy thanan eight-blado slnglo-rotating proi)ollor; tho offoct wasovon more pronounced at ta,ko-off and. climbing conditions-

4. An eight-blado dual-rotatin~ propollor was foundto bo substantially nore offj.ciont for tho tmko-off contri-tion of flight than an eight-blade single-rotating pro-pollor, particularly for conditions of oporation at high .powor cooffioionts.

. .. . . .. . .. . .5.” “!?he blade efftcignoy ;of.-elght~blado “eitigla~ and..m‘dunl-r~tating propellers was only..slight~y less than for

corresponding fouz- aad sl=whlat!!e.~rop.ellers praviousl$,$eete&. ““ . . . .. “ . .. ..“

. ...- ,.. .., 6. Th-e power a~ser~et! per blade by elghttib~~a.e.-aual-rq$qti~~ and eight-blade siz@Rrotatio~.pr opel@ rs,. as

. qonpa+red to a three-blade propeller, was. about 87 and BO.peroent, “respectively, at.pee~ efficiency. ‘ “ .

.“ ,. . :. .. . . ... ... . . . . . .. ..

.. ..L.a?@ey:Heaerlal Aoronauti.cal :Laborat”ory, - 0 ..”’- :

. .

National A@vteory Coanit%ee for Aoronautlos, “ “ “Langley Field, ~a.

mmmelmns

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~...:. Bjofiann,Jav.id, and Ha.r”tmaa,Ndw”in.pa?. ..WZx@-Tintill

Tests .of ~our-.and SZx_Blade, SSqg~e- and BwJI+Rotatin#.T.ractOr PropellersP , MACA Eep~ .lJo,.”74’?m... ..1942; “. . . . .

.. ,.

2. Biomann, I@vld, and. Con?ay,.Ilobert. N.: The Soloatlonof Prqpollers for tiigh.-Thrust at ,LQW .Atrspe”edo . MACA

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–27.0~ ~ 33.8”-nv,

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Note: Frontand roar IInacelle lineeare identical.

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Figurel.-Planview ehowing dimneional details of wing and nacelle.

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..-=37=----—.—, . . . ..—.m..es- _—._..

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Fi&ure 2.- Test set--q. Ei~t-blade dual-rotation propeller installed. cl)

IUACA Figs.

2.4

2.0,. . .----. .

<IIy L2 /‘

z$ .8~

.4 / {

/‘/

o /0 20 30 40 50 60 70 80Bhde u.le, p, &g

Figure 4.- Difference in blade angle for equal torqueat peak efficiency for,eight bladea, dualrotation.

Figure 21.- Ratio of power absorbed at peak ”efficiencyper blade for eight-and three-bladepro-pellers. With wing.

.

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./6

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o .4 .8 [2 /.6 2.0 2.4 2.8 .?.2 3.6 4.0 4.4V/nD

4.8 52 5.6 6.0

Figure 5.- Thrust-coefficient curves for 8-blade, single rototion , withcmd wing.

.8

.6

7

.4

.2

0 .4 .8 [2 /.6 2’,0 2.4 28 3.2 3.6 4.0 4.4 4.8 5.2 56 60 {~nD -m

figure 7.- Efficiency curves for g-blade, single roiotion, without wing 4

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0 .4 .8 i2 [6 2.0 2.4

.80 ,

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o .4 .8 it2 1.6 ‘2.0 24

FWJ. IX* - hP_fflGid mrvas fa- 8-MA .inql.rointm. aiih win+

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. ...—-—*_ ,.,:- .:.,~~

2.0

1.6

Cj

/.2

.8

.4

0 .4 .8 /2 /.6 2.0 2.4 2.8 3.2 3.6 4.0 4.4 4.8 .52 5.6 6.0~nD

Figure bb. - Power-coefficient curves, for 8- bladt’, single rotation, without wing.

*

.8

.6

7

.4

.2

0 .4 .8 [2 16 2.0 2.4 2.8 3.2 3.6 4.0 4.4 48 52 .56 6.0l@D

Figure 19.- Efficiency curves for 6-blode dual rot. t;on with winq showing 5’Jpe~mpu.. d curves for 3CY, 45-and 6V single rotation.

r -—. -

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0 .4 .8 12 16 2.0 2.4 2.8 3.2 .36 4.0 4.4 48 51? 56 60

fqura 8- nwu.i .,afhcnm+ curves for @- blL ia dual mtathm, train. wdtmd wmq. “-—

“ ~’”--

1

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0 .4 .8 L2 16 2.0 2.4v~D

o .4 .8 L2 16 2.0 2.4

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0 .4 .8 L2 ~6 2.0 2.4 28 3.2 .36 40 44 48 52 ~; &O .;).

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F)gm91t4-&-afhud -tnr C-bbadm&drG+EIuI,kkr, dhut,@

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7

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0 .4 .8 /2 [6 2.0 2.4 2’.8 3.2 3.6 4.0 4.4 4.8 52 5.6 6.0~nD

Figure Il.- Efficiency curves for 8- blade dual rotation, tractor, without wtnq

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.24.-r

./6

.08

~

o .4 .8 /2 /6a

2.0 2.4 2.8 3.2 3.6 4.0 4.4 4.8 52 56 6.0 pVlnD =

Figure l.?..- Thrust-coefficient curves for 8-blade sinqle rotation witl) w;ny . R

f.-, . -?

2.0

1.6

1.2

C&

.8

.4

0 .4 .8 /2 J.6 2.0 2.4 2.8 3.2 3.6 4.0 4.4 4.8 5.2 5.6 6.0V/nD

Figure 13(b).- Power-coefficient curves for 8-blode sinqle rotation with wing.

.8

.6

7;

.4

.2

0 .4 .8 [2 /6 2.0 2,4 2.8 .3.2 3.6 4,0 4.4 48 5.2 5.6 6.0V/nD

Figure 14.- Efficiency curves for 8-blode single rotation w;;h wing.

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7

:8

.6

6.4

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5.6

.2

0

4.Lf

4.0va

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(28

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%WH+H+H, , , , , , , ,I I l_u_LJ_l o0 ,8 16 2.4 3.2 40 48 56Ca

Fi&pra 15.- llmim tit for Propdler S155-6,0@t-bla& ❑ingle rotation with WIIW.

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0 .4 .8 A2 ~6 2.0 2.4 2.8~nA

3.2 .36

I I I I I I I I KI I I I I I I I I I I I

4.0 4.4 48 52 56 60

, , & 1

I I L

\ .

L

.72

.64

.56

.48

.40

G

.32

.24

./6

.08

0 .4 .8 “ 12 L6 2.0 24V~D

\ . 111111 [11.1111

.36 \ I I I I , 1 IlF#t#&&/kr- – ~

.32

.28

.24

.20

Cp

.16

.t2

.08

.—Vj+ID

, ,, , , , , , 1 , ,

Ilnl I I I I I.04

0 .4 .8 12 16 2.0 2.4

II

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1

I

i

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4

I

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2.4

Pn---

1.6

c;

/.2

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,0 .4 .6 A2 16 2.0 2.4 2.8 3.2l$hD

36 40 4.4 48 52 56; 60.

.. ,

I

fi@# n@- ~ mat%adm cur... far S-blad. dual mWmn with .mq, shows.g Supurmpmad nmv.. fur4Y and W For W@ rofat, on.

t

8

I

,

,

I

II

1.2

Lo

.8

CJ

.6

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0 .4 .8 L2 L6 2.0 2.4 28 3.2 36 40 44 48 52 56 60

I

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7

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6.4

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5.6

.2

4.8

0

4.0.va

3.2

2.4

/.6

(28

o .8 16 2.4 3.2 40 4.8 56 640~.

?%SUI’E20.- Ih8i@I ohut for propellus 81W-6(R.H. ) ml 3156-6 (L.H. ) ,elpJt-blmda danl rotationwith wing.

u ... .

1.4

/.2

/.o

.8

c+FrCfi

.6

.4

.2

0 .4 .8 Li? /.6 2.0VJrzD

figure 22. - Propeller curves showing the effect of small v.r,atlom m re.,- blode

CT

1

/0

.8

.6

.4

.2

no .4 .8 L2 16 2,0 -

V@D

I

angle (or o fro!+ blade angle of 40~ (8-blade dual ro+ot,on propellers wihou} wing,)~

+

I-uN

.56

.48

.40 I—— ___ _38.7°

I\&” <.. —— __ _ -- an-lo

w

.32

c,.

.24

./6

.08

0 .4 .8 1.2 [6 2.0VhD

.56

.48

.40

.32

c%

.24

./6

.08

0 .4 .8 /.2 /6 2.0VJnD

fiqure 23.- Power coeffici?nf curves Showinq the effeci of small vario+ions ;n rear blade angle for a front blade angle of 40”.

(E-blade dual r.ata~ion propellers Wl+houf w’Inq.)

I

NACA Figs .24,25

.9

.8

.7

.6

.5

v

.9

.8

.7

.6

.50 .4 .8 /.2 /.6 2.0 (?4 2.8 3.2 .36 4.0 4.4 +?8 5.2 56

VfnD(a) Wi+hou~ w~ncj Lb) W(th wing

Figure 24, - Efficiency envelope comparisons for e;qht-blade propeller si-towing affect o+ dualrotation

.9

.8

.7

.6

.5

n

.9

.8

.7

.6

.50 .4 .8 /.2 /.6 2.0 2.4 2.8 3.2 3.6 4.0 4.4 48 5.2 5.6

V/nD(a)Single rotation (b) Dual rotat(on

Flqure 25, - Efficiency envelope comparisons for eiqh+-blad~ propeller show!’ng cffec+ of w;ng

, . . . ..-.... ..-.-—

.

.

..

MA(2A F&m 26,27

v

o .4 .8 l+? 1.6 2.0 2.4 ~2k8n .%? .5!6 4.0 4.4 48 S.2 S.6

(a) Without wing.., ..-

(b) with wing.Figure26.-Efficiencyenvelopecomperiaonsforeinglerotation(4-and6-blade raeults taken

from referenoe 1).

Q

(d Withoutting. (b)WithuingoFi~ 27.- Hfieiemy •n~elqe oqleong for dml rotation (4-rend 6-bide reeultn taken

frm reforaloe 1).

.

HACA Fe. 28,29

0 .4 .8 1.2 1.6 2.0 24 32 Jt6 4.0 4.4 48 .%2’ 56i%%

FiWe 28.- Increments of peak efficiency resulting from dual rotation. Without wing(4-and 6-blade reeult~ taken from reference 1).

.=

.04

.W

An

.02

.01

0 .4 .8 L? 1.6 2.0 2.4 2.8 a2 s36 40 44 4.8 62 S6

Figure 29e-

V/nD

Imremento of peak effioienoy reeulting from dual rotation. With vi%(4-ti 6-blade resulte taken from reference 1).

I—_. ..— . . . . . — —.-. .—

I

Pi&@.50,s1

o .? .4 .6 .8 /.0 L2 1.4 i.6 M 2.0 2.I? 2.4 26 2.8 3.0Vjm

Figure 30. - Effeot of dual rotation on efficiency for constant power. Cp = 0.2. With wing.

.9

.8

.7

.6

.5

~

.4

.3

./?

.1

0 .2 .4 .6 .8 LO /.2 /.6 1.8 ZO 2.2 2?4 2.6 2.8 ~0‘“4w

Figure31.- Effoot of dual rotation on effioiemy for oowtdi power. Cp = 0.4. With wing.

1

— Iamm II I n=~mllm■ mmu-mm—-m-—, =—-,,. ,..—

MACA Fi@. 32,35

0 .2 .4 .6 .8 10 /.2 1.4 1.6 1.8 2.0 /?.Z 2.4 2.6 2.8 ~oVlmo

Figure 32.- Effaot of dual rotation on effioienoy for conntant power. Cp = 0.6. With wing.

Fiwa 33,-Effeot of dual rotation on thruet at oonstant power. Vithwing.

.

—