Reproduction Quality Notice

This document is part of the Air Technical Index [ATI] collection. The ATI collection is over 50 years old and was imaged from roll film. The collection has deteriorated over time and is in poor condition. DTIC has reproduced the best available copy utilizing the most current imaging technology. ATI documents that are partially legible have been included in the DTIC collection due to their historical value.

If you are dissatisfied with this document, please feel free to contact our Directorate of User Services at [703] 767-9066/9068 or DSN 427-9066/9068.

Do Not Return This Document To DTIC

mu •J#priH»i-*NWW»* "•L*- -,,

»

1

APR Oct. 1<*1

NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS

WARTIME REPORT ORIGINALLy ISSUED Octobar 15*1 aa

Advance Restricted Report

THE SELECTION OF PROPELLERS FOR HIOH THRUST

AT LOW AIRSPEED

By David Blermann end Robert H. Conway

Langley Memorial Aeronautical Laboratory Langley Field, Va.

1 L fc V : ! tt (to Or.cment? Divr»:?«, T-21 KUi, WrirJ.t Held

Mumtim i'a REMAN um,i .UM:|I - ISHWr-6 iU^-/A/<9F^J9V

•• i*« ' c, LwV«» .«lion " ' ' til .- mvillS Ut». . •.i»(ttlt'(,ij;e..^e ( I .';

n.i»iil (ILIJ. .,»,.•.. .ft,,

NACA WASHINGTON IMi

NACA WAKTIM: EU i CATS are raprmta f ; ft] en, riginally Issued tu provide rapid distribution öf ircto results to an authorized ervup requiring them for the war effort. They were pre-

viously :.' .: -'. :• r • .iocurity statua tut axe now unclassified. Seme of these reports were not tech- nically * i:'ea. All have been r*!pr *iu*ed without change in »rif<r to expedite general distribution.

1,0.

THE SEtECTIOH OF FROFEUIKS FOE H3SH TEflET

AT LCW AIRSPEED

By David Biernann and Hebert I!. Convoy

SüMMfCT

An anal;.-ciDf tared on recent propeller data, woo made of several ir-etlnds Tor imfrovine the thruBt of propellers operating at lew airr.poedn. The analysis coiu-intod of doteiTalnini; the improvements In thrust or efficiency which could toe obtained by tho following expedients:

(u) Increased number of blodco

(b) Increased bluie width

(•:) Increaced •Haceter

(d) Dual rotation

(o) Two-speed Retiring

The anolyels indicated that all of tho above tsethodc were very effective in increasing tlie efficiency or hi; lily loaded pr-u'ellero operating at low r.irpp6eds, par „ j cularly Die last one listed.

HCTSODUCTIGS

Tlio pr^blon of improvlnc the thrust of propellers at low alrtipeedo is pr'xarlly one of reduclnr tho an^le of attack of operation of the sections in order to improve tho L/D. Reducing the blade helix ancle also Improves the thrust for a clvcn power utjut owing to tho effect of rotating tba lift vector into a

p alJntntnü with tho tlirust rector, thereby reducing tho rotational lorn <uid at the Eiaa_ time absorbing the- cnt'lnc pewor. That the low-cpced operating condlti^iiE of conventional thrce- blade conti-oiluble propellera m present-day high-perfaraaooe uli— piano? la not conduci-.'o to high efficiency nay roadily bo Been by refcn-lnp to fit^ire 1, which shova the. blade uv !••, P, for various conditions of power luadliic and V/riD. Obviously, take-off lludo anclen of fr.jm 30° tj > j1 correspond to ui,-jLc—ui -attack value« ranping well bey und the ntall, a- oay to noted Crem en

'ion of the angle-of-attack curve •.'.en in the lower part re 1.

Fipu-o 2 proscr-tc an l/D curve for the Clark Y section vhleh chova the magnitude of impr,'Vt-nf;nt «hut accaupwvieo any reduction in tl* nnglc of attack.

There ere Hcvoral nothnds for reducing the aiyrlo of attack end blade ari^lo foi- conventional three-'olado propollcrG, which sv%- he enumerated un follow.

la) Increenlns the blade area by

1. Imrearod blade width

2. Inr.rea.ced ir.raber of blades

3. Incre&ced diraocter

{l) Increaolne the rotational apeod for the take-off condition tliroich the vine of two-speed eeerc«

toother method Tor improving the efficiency lo "by reducing the rotational VJSF, by dual rotation or through the v.oa of fixed Btfrfacta tioimtoc in the stream ahead of or behind the propeller.

Thong verlouo mathoda Tor improving the thruct of propellerc for loVapeed operation are herein ajiul."ied on the heule of tost fla'-li.

TBESS3l£Ka.Ca

The data ueed in moklnc these aral;-oen were obtained during the pact 2 ;tore ficratectB of single- rnd dual-i'ctatlnp pro^c-Uero. The four- and slac-blnde cinole- atid duol-rota^ins propeller data dlncunce-d herein were obtained fVom reference 1> the other data dlscUBMd ht.rein \rill bo publlahcd at a later date A detailed d»»crlptlon of the set-up and testing technique !• fclven In reference 1. 1 iguroc 3 rni U are a photograph and a dinencionod plan view, respectively, of the oet-v.p. Ten-foot propellers, licjailton Etonunrd drawlnc HOB. J135*6 (li^it-hmd) end 31 (lti't-hond) wero used, rlrai-fora and blolc-forn curves tor thoee pripeUero ore provided in fipuro 5-

Cvshda. - In the analysec presented heroin, Btcndard propeller coefficlcntc and nymbolr art «Ma, ac listed belows

-, power coefficient p na DJ

T Cm B 1*—;, thrust cocri'iclent p u D4

°T i — V/nB, propulsive efficiency CP

—^"^-» spoed-pover coefficient

V/nD advanco-diaooter ratio

P power of engine, foot-pounds ppr second

T0 • T - Hi, effective thrust, pounds

T total propeller thrust

AD Increased drag of body due to propeller slipntrenm

n propeller rotational speed, revolutions! per Becond

D propellor diameter, feet

V air speed, feet per second

p maec density of air, clues per cubic feot

p0 moss density of air at cea lovol (o.OOC370)

A.TT. B 3-O09OQ /*'• 16 o-c

»0

•ult

©" *Q8. activity fuctor

blade vldth

station reJJ.ua

propeller radius

blade ancle at 0.75B, degree

Bpeod of sound at sea level

speed of sound at altitude

a

helical tip speed of propeller

circular tip speed of propeller

section angle of attack at 0.75R for Infinite aspect ratio, measured from chord line ..u«o aspect .„ wun cnord line

shoving iha efficiency or relative thrust that can he obtained frets certain propeller and gear arrangements for a constant power input- The thrust ratios and efficiencies are plotted against v/nD or constant values of Cp. Constant Cp represents alco constant engine power input, assuming that constant speed propellers are employed and assuming that comparisons are made on the basis of constant altitude.

Lr ««A* in tr ^S-^Ä^ "» •—« case based on thn v/t a thB case or +~„ "»ottinee. vhrn rT

10 «Euro 6 la n ov. x ° fraB 0.2 to o * "«"•rent «^ J° ° (

Cha" e^ng rollle8 of . °"£

number of toX^^"1**, Fronted m * % Countered for

» x-«n» tnci diameter,

Ho rCOaeo of ordlnaten foi. Sfn , ,w"e ßlven far -i• «o-lerol ^ow«,. coofficim«- ^'"OOfes SJI'B0eI«»Ü8O.t.. , ««^ients, Cp

•^ftlt- °"7/ end «_ "' 0-38.

The sea-level power coefficient (Cp • 0.3fl) applies to the take-off

analysis. The chart indicates that take-off power coefficients ranging from 0.05 to O.L may fee expected for military applications.

Solidity anrdvcla.- The three methods for Improving the thrust by means of increasing the blade area, (a) increased number of blades, (b) increased blade width, and (c) increased diameter, will rocult in caeontlolly the rcac effect, except possibly for differences in weights and mechanical camplicotlone, provided tho tip speed is the

The method for camputlnc the thrunt und efficiency of propellers havlii£ various numbers of blades or having blades of different widths io civen in tho following outline:

Constentr: Y, Cp, p, r>B.

(Suteorlpt 3 denoted number of standard-width blades.)

(Subscript x denotes increaaed number of blades or increased blade width.)

1. For several Vfdues of V/nD, P is reed at a conotant, value of Cp from U.O Cp chart.

2. Cm la road from the Op chart foi- values of p and V/nD under (l)•

3- Tho following plots may be connnructed:

(a) Cm vo. V/rJ)

(b) CT , Cr3 VS. V/nD, Tx/T3 vc V/nD

(c) C^./Cp L VB. v/nD

The outline of the method for improving the thrust by moans of increaplnc the diameter is civen as followa:

Ccnrtonts: p, p, nD or Up speed.

(»subscript 3 denotes threo-bli.de propollor of normal diametor.)

(rubccrlpt x denotes propollti" of Increaaed diameter.)

1. For sovoral values of V/nD, p3 le rood nt a constant Cp frnm tho Cp chart.

2. 0p3 1B read from tho Op chart for tho values of p3

raid V/nD under (l).

Cpx • (D./Dj;)* Cp3

Px in rood from Cp curves for sovoral values of V/n3

end Cp .

Cj is read for corresponding volvßO of V/nD and ßx.

Tho following plots may bo constructed:

(a) Of vs. V/nD

3-

k.

5-

6.

(b) CTx/Cr3 vs. V/nD

(o) Cr/CpSL vs. L, (n vs. nD zJ))

vc^x (a «• & In the present analysis a threo-blade propeller Is compered

with it slx-Hido propeller which aboorbs tho came power for the peak efficiency condition. Tho actual blade- area ic slightly different, awing to the difference in blado interference for the two cusoß.

Dfi • 0-75 »3, instead of DG » 0.707 D3, which corresponds to constant area-

Dual rotation. - The method for comparing single- and dual- rotating propellers io tho gome as that far propellers of different solidities and so will not be repeated hero.

Two-awed, gearing. - Tlie object of two-speed prorellor reduction gcorc io W provide a ocans for lncreaelng tho propeller rotational speed for tho take-off and climb- If tho ciißlnc could bo ovor- spoedtd the necessary amount, tho recults would be the euae as thoso obtained with two-uptcd gears. The amount that the propeller opted should be Increarcd for take-off doponds entirely upon the tip speeds encountered.

*'""*». 25,000 rect HeIlc* M* epood - 910 , .

apood +„ *,° ^odueo the, —^

****** * ° D**d ÄS^ii* ** tlp

•1-305.-<i.097.a>J(3

-# "Hit

Coneta„ta: p ""* * «*Ü*,d J7 ' P» and D.

^ubocript i rofora tQ

8 . For A ßiven value off Cj> , (1 la reed at several values

of (v/:iB) from the family at Cp curves.

. Cij corresponding to ß Mid (v/rtfi) 1B read ?rom

the family of (>j curves.

?. For 6 elvon value of i^/n,» Cp is ecmputei;

it. (v/tiD)= is ecraputcd-, (\'/nO)E = nj/a, (v/iiT)x.

*>• Ba covreBjoiidlne to Ci>„ and (v/nD), la read from

the f sally of Oji„ curvea.

6. Of oorreopMiUng to Pa and (v/nl))a In rend from

the fan-'Xv of Oj curves.

7. The f sllwlne plots may 'be constructed;

(a) »„ff^ «I. v/rX

M CTa/Cpa Cv/ngE) vo. (v/l^D) •>" IäIMII •proixallp;

tH ^/C^ ^" ^l^.-The thrust of

SÄSSSJÄ- ^ «preaaio» IC 1

la i-i.i" *y ~

1-1

-,,-rm convenient to v «solved into cno more co'

-T, AT <\-IT T

M

T,?/V for T

dp»'»' f« T

r~7~

:iA

j

SJP. for A I*

T^ --«—(v/nD)3 (2)

ro obtain thia In toras of thruot, the cuhotltutloa of -f v/nD C-.

fox" n la made

CJ» /c?2

Cp IJD

(')

Rewriting:

&?* * 5 ci> -- CT - 5 c-,n = o 1 2 J nD 2 -

Thin may bo solved to five On for riven valuta of Cp anil. *ideal

V/iVD, vhloh Mftj then bo oonporaA with the Oj cf on;- deolred liar a... t.x . era voluoa of Op ami V/nD.

' UT8 AT1D !3ISCUC::,I0ir

Thn reGiilto of tho :mJ..vDis ere prcsor-tod in several tfroiipo as folloi-a:

EUBKtt I BoXidlty

(a) Effect of lnerceolng the mrltr of blades 10 to 12

(o) Kffect of increfc3ir,3 blade width 13

(c) Effect of Increasing ditmeter Ik

10

II Duel rotation

III Two-opoed (jeorinG

IV CunparlBon of methods for increaclng thrvtot end efficiency

V Mothod for computing changes in static thrust fa.' changes in rolidl'-y

15

16 to 19

20 to 26

27

In thle analyais the emphanis 1B placed on methods for improving propeller thriujt or efficiency for the tato-off end climbing conditions, realising, of oeurM, that certain other sacrifices •hy be noccBsat-y. The ciuoB&ion 3 s alweya, "what is the beat c-aprem!;F.?" The answer deiMrmds upon tha pavticulaj- deeicn conditicne in inieitlon) therefore it cannot bo anuvered bore. Information for arriving at cood encinct-ing ccmproElncs io presented, however, in enoilj interpreted chai-tu which have a central application'

Solidity.- In figuroo 10, 11, rnd 12 the effect of increacinc the lumber of blades up bo a total of cii'ht is indicated} the diurxt..r, of courrc, ID kept com Lout. Although tlie peek efficiency for each propelli.a- i" approximately the ::emo in macnitudo, it occurs at different V/rD volucc for the different solidities. The effect of inert'jain,': the number of blades ?s to vnlond each individual blade, v*. Ich ollovo it to operato at lower values of a end Cj,. This incv^eeoci tho L/D and efficiency for the take-off and climb, partlaulnrly for the extremely hi-. 1c '•'..3D, but with seme sacrifice at tlxi upper end of the V/nD ranee» the EMcunt dependine upon tho pai't^civlar toBiF» conditions under consideration.

Of pirticulnr interest is the fact that thoro appears to be little f.ii'lcn-.v.y to v;c Gained at take-off by increar.inc tho nvmbcr o.C blade1! bayo'id BtX>

In ft . •• 13 tha effect of incrocr.j.r^j the blade width 50 percent 1B rh m I x ••• Vwo-b-nde propeller; the tests of whic?: wero aado

• •• .< rencc 8.) Although tlu.'- teeta v«ro : vi., oi'inr to their liiiitod mx.»., V t indit.'---.icns ari th tha bjai'o «lath has tho . t on th-j

. efficiency M Inftrcaalne tho aia&er of blades. Fu-L'i<r • ctiniiive tosta of wide ";>i.iSue nro buir,;. c;vtujtcd at too prefle&t tij ...

11

In fipure 1U a ccrrporlsor. ID made of two propellers having substantially the jane blade area but different diameters. Tho rclatl.-e diameters were determined from considerations of equal power absorption for peak efficiency; the six-blade propeller had slightly greater area thun the throe-blade propeller. Inasmuch ac the efficiencies wore about equal over the entire V/nD ruuco,

.!l it appears that Increased solidity is about an e%U0l substitute for Increarod diameter up to cone limiting value) that value probably corresponds to a six-blade propeller, since an eight-blade propeller was found to be only rlifditX, better than a six-blade one. (Seo flea. 10 to 13.)

BnsLXS&iiiSB' - In figure 15 tho öffnet of dual rotation is shown far the alx-blade pi'opoller} the results vore taken directly from reference 1. The principal effect of dual rotation is, of course, to eliminate the rotational component of the pllpstree<m, which results in improved efficiency, parbiciilarly for highly loaded propellers operating at low values of v/nl). The test results indicate tliat dual rotation Increases the efficiency over the entire operating range, especially fat hifhly loaded propeller:: •

Two-srccd pearliv;.- Although the advantages of two-speed gearing have been appreciated for a Ions time, there has not been any se-rlouo attempt to incorporate two-epeod genre into propeller drives until recently. The reasons for uhic aro that two-speed gears have not been vitally noceEHi.r,v, up to the yi'eccnt time, in order to ob'-Mn Futisfactory propeller performance at low forward speeds} and also because the high speeds and crulping altitudes have not lieen high enough to maku possible ary lav,-c galas

In thrurt

In figures 1' to 19 are plotr inrücs.ting tho Improve-mentu in 1 paei'iblo through the use of two-3pi:ed coarj for a /ariety of condltlciir. It ma;- to noted that the advaatujeB GTS grtatect for low solidity propellers uhirh are operated under highly loaded conditions. Alro thr, adrantegoa :sre- the gre-abc-st for hlfh ictios el fi :J- change, which CLJI only be uevd far hlgh>speed| high-altitude airplanes.

Corroc.'-ir-cns "' it th:'dn. - In figures 20 to 85 are both thrust and efficiency comparisons of the various methods xov increasing tho thrust of propellers operating at. IJW .'orward speeds« It tppeera that the motaod of tvo-spoed gearing offers the greatest roturn of any single method, partlc^Llarly in /lew Of t!ic fast that It 1.' not accompanied by any aerodynamic 1OU.J for the hlgb'speed

Ion. Increased solidit..-, particularly if accompanied by dual rotation, offers further moaiu; for improving the low-speed conditions.

12

With all Bf the raethodo noniblneft the ideal ofrieloney con he closely u.pronuhed, even for extremely hichly loaded propellers.

An these methodB ere directed toward reducing the angle of attack of the hladeB, vlth tho exception of duel rotation, It any he of interest to oxomlno the oporating conditions- In figure Sf i o a. plot of p and a for the Yorlouo Methods indicated in figures 21 end EU. It may ho noted the* as the Diode nnglo and angle of attack at 0.T3* w© roduood hy any method, the efficiency at lev speed is incrucood.

Take-off ccmmt.a,tlonn.- In computing take-off dlotancco the problem often arises of determining the cHaivjctorlatictN of some particular propellor vhich has a different solidity or activity factor from one for vhich teat results are evalluhlo. A« moot methods for computing tako-aff distances lnvolvo tho static throat, tho problem is one of correcting tho static coefficients for differences in activity factor.

A chart ID presented ^figure 27 wherein the static thruct coofficlont is plotted tcainst niflnbor of hladoo, vhich eloo represents a rouge of activity i'octox-o for tho ontlro propeller on tho nwvumption that tho activity factor verlos directly us the nuater of hlacuB for a typical present typo propellor design. Although this chert was not derived from toot data vheroin tho activity factor vao chtmged hy lncreaalns tho Vlado vldth, the available Information Indicates that the oi'CoctB avo euhetontiolly tho ootto, irrespective of tho method of changing *ko activity factor.

There are tvo methods of using tho chavt, ono in vhich tho values of static thrust ore used directly; and tho other, in vhich the curves ore ueod as correction factor« for c":ror tost data. Tho latter method is x-ocoisacnded tccauoe tho relative thrust Is probchly independent of moot of the- propeller-design characteristics, such as filrfoll eoctlon, thickness, and pitch dintri'oution. 'ihia method cf correction consists simply of multiplying tho known static thrust coefficient ty tho ratio of static thrust ccofflclonts takon freu tho chart correspondinc to tho different activity festere-

Rimilcr charts any ho constructed for different v/rj) values ty making cross plots from figures 10, 11, and 12.

In tohleo I und IX are listed, for convenience, the activity fact ore for a numhor of cccconly used Curtice end HaaHtcn St ander 1 proi oilers.

13

CaiCniPE» ETliTE;

The protlm of increasing the take-off end disking thruct of highly loaded propellers resolves Itself Into providing aeons for reducing the angle of attack of operation end oleo for ellnlnating the rotational lonaes in the slipetreaa. üf the tothods etulied to accomplish this purpose, tho relieving remarks apply:

Increasing tho nunber of blades from throe to etx was found to result in nubatmcial improvements In the low-ci-'tcd thrust, particularly for the higher power louxüngc. Eicht-blade propellers were t'oiuul to produce only a slightly hit>ier thrust than oix-blado ones. InOMNt solidities resulted in auall reductions in the hlji-uj'eiäd «fficiency.

Increasing the solidity bj ineno oi" increaping tho blado width was found to rccult in about the DSBO effoota as increasing tho nuriber Of bladr-B, within tlio ücopo of tho enalyais>

Increasing tho blade area by Beans or increasing the di.-ateter hod about the asms ciTect on ;he lovspei d thrvxt ;>.a increasing the solidity, far equal tip speeds-

Dual rotution rooulted In c. cr.nl 1 lfflprovenent in the efficiency over the entire operating range, particularly for the more hi$Jv lvjoded propeller••

Two-pj*.ed gearing vrio found to be very effective in inert t.Ling tho low-speed eiu'uut, particularly for low rolidlt-v propellers iipi.--atIng un'-or hlahly loaded conditions. Tho advantages or tvo- specd gearing were greatest for high .'ttioa of [M;

1 change, which

can only be urea i\'r hlgh-spood, high-altitude airplanes. Ac no efficiency penalty la imposed at h'gh speed., tola method appears fee Vc very attractive for a certain cl^.!.i JJ. alrplanec

A combination of :>ix-blade-, dv.al-ro a,: on, i rearing vor found to provide moans for clc xiäatlng the Ideal efficiency for highl] loaded propellers.

la;ifley Mmorial Aevonouliacl Laboratory, national Adrioarj c ulttee ;c.r Aeronautics,

L mgloy 1 leid, Va.

lit

BFi-ia-jiiias

»opelOero. EACA Hep. No. Mi W**

2. ntrtmon, Edwin P.» and. BierDBim, David: The Aerodynanio

ITACA Rep. Mo. 6«), 1S3Ö.

3, end U

16 TABLE n

Activity FactorB of Hanllton Standard Proieller BladeB

Blade drawing mwber Baolc diameter

(ft) Controllatlo binde Hydranatic blade A.F.

JX'J'j-C 10.5 90

6091 -0 10.5 83

C095 -0 6l.'7 6237 -12

-18 -2!+

aa. -0 -6

-12 -18 -24

9-5 71 83 95

107 120

C101 -0 •6

-12 -18 -2!»

£183 -0 -6

-12 -18 -21»

10.0 77 07 97

108 119

C103 -0 fill -6

-12 -18 -2U

6139 -0 «6

-ie -18 -21»

11.5 1

Ö 72 62 91

100

(105 -0 (3U9 -C

-12 -18 -21»

6153 fi!29

-0 -6

-12 -18 -2'»

13.0 • 66 75 83 92

100

(109 -0 6135

-12 -18

.-•• 66 78 90

101

61*7 -0 LI85 -0 10.75 £5

6i65 -0 ... -12 -1«

t-239 -0 -6

-12 -18

8.0 ,6 81 9C

110

• "-'?"- *

SOU •• ;

TABLE II (Cont.) 17

Blade drawing E ..' • llutl» bl«M

liUialpr B.. ;'rf*»tlc 'blade '

Basic dlBTsrter

(ft) A.F

6227 -0 6157 <

-12 -18

621+7 -0 6179 -6

-12 -16

10.5 87 98

108 119

C2U1 -0 -{

-12 -13

9.0 8 96

107

Blade drawing number By dramatic blado

Baste diameter

( •)

A.F.

6155 -0 «-159 -1

-12 -1ft -2'*

1'uO 75 83 92

101 109

6173 -0 17.0 61

6187, 6I89 -0 15-0 65

tlS>3 -0 -6

-12 -1«

tt.5 93 10U 111» 125

6235 -0 12.5 90

62U3 -0 -6

-12 -18 -e.'i

15.0 ei 88 9U

101 108

62U5 -0 -t

-12 -IP -21;

17.0 75 80 86 91 90

18

620.

WA

Jfy ria*. 1.2

70

n,

50

~*30 o *20

ß ••

-.*

£ 6

-

^ .i

s ?

IU

0

-/öl— tf .4 .8 1.2 1.6 2.0 2.4 2.8 3.2 3.6 4.0 4.4 4.8 5.2

V/nD M JIM 1.- Variation of f' and ot^wlth v/nD for a three-fclade controllable nropell^r

8* "•- - 0.8, Ü.4, aM C.C.

fr*

^">K

p .._ v 3 „ .

\

-a-—-== O 4 8 12 16 20 24 28 32 36 40 44 48

Angle of attach, deg

• in» for a "lirk * »irtoil.

i IT

I

I s/r» (9

Tu -..;,.

No**?: Front an! raar naselle ltntfl are limHwl, ^^

Figur« 4#- Plan »!•»» showing iiirrnnional iet-iili- of wlnc an* nicelle. Dineneton a for f-w-blai* nrondW = 9.7" and for «ix and aighf blaie nropeller • 10,0".

• ' "

n,V . .

*/.4

|/2

g/.O

I U Q.

/ 1 . ....... / ..... _ . 17

~~7 j y

' o olaaea f / . j

XQf v •' "r 4t

ZzZF'fe •—£ ^ ^ ^ £ ^ ^ ^

^S^^1^^51

7.JSJ

5 .«> ||

-.2

./5S-Ö 8^

/

~IQO 200 300 400 500 Airspeed for helical lip speed at 950 fps

(0.9VC at 18.000 ft), mph

• •

./0.5 b

.05 %£

1.80 l{ ' 700 fps /

1.70 1 1 / Ö00 9001

1.60 1 -,.50 won.

/ /. / / / /

'^^1100 j/^ J"^

1.10

i an Iff loo MO mo eeo eeo 300 310 3eo *?o ico 500

Airspeed, mph

r . i

—

ff}

1TACA

1.E4

i.ao

1.1«

i.ii

VecAealt

1.08

1.04

1.00 U

Ilfi. 7 i

' ^

10 20 3° Altitulo, 1000 ft

•• ;>.

I qt eyial at aaa loyal wltu rtttteld,, Figure '.- Variation of ratio "^„i of »oua.l at altitu.1

»—'•

-4

r r

z>

&40

a.oo * d •„"•••••'.

Fie«. I';}?

T3

1.60

1.20

•• ___" . _ :s; ' | /

i __ ~".r~^^_ _i ^, t.4 _L_ S-, V —. • 1.6

_N -V_I_ % XJZ ~ *\ %Taf\ f 66

" $ ^i_ -"* ""^ _ $ \ ""a* i» *,\A - *"Bs=:~2S - —^ ^ ^ ^= s^-*

— -*S5-~=i = n = §^ -- \l Zj • >i :>, . _ ^ £ «^ a __ ^S^-fl,? S5s .4 T^_6,

-..-.- ..,,:*il "^"- •' 0 .4 .8 /.£ 1.6 2.0 3.4

V/n,ü Figure 16.* Effect of two-np«*ed gemrinr on t\ riif-t at low •pMda« nu*M*bltrfa n I

.

<?.<«?

'•).,.. I-.J

.8 1.2 V/nfi

7.- Effect of tn-npeed ,-earin., on thnut at lo» «peed*. Fwr-bltdi propoller.

I 1^

'S

27 rig«. w.!9.:?

q_ c ! 1.80

• . •- 1

\ /»..,/l > U'o, .a t n«/n,-/.<?

**. k I_LI :..

r. 1.40

s N v. 1 ITH rsii

s iSosJ r-U

C- - 4> \ ^"s -LL ^fc^ ' 1.00. .... .... ^- • > 6

8 12 1.6 20 2.4 V/n,D

Figur» 1H.- Effect of lw ip—d *^snri(r an thru Ft. at )a» Bpead*. fix-Mtl* prop«Uer.

e.oo

1.60

ISO

.80,

\ ' ' n.y» 1.- 1.2 . 1.4 s s - 1.6

's ' '

• *" - s t N*»I • ' ( Ofs. ' - _ Td ' 1\ ••

'c »" ä .- ' •> %

1.2 1.6 2.0 2-4 V/nfi

Figur« 19.- Lffoel of tao-xpeed ^earin^ on thrurt at law ap«»<ir. Kiüjht-bUd« pror-elli*r.

.- Coapariion of Mthod« for m

I >i

n

•••• •

•

,' --

—.its I I*" *.*<*• ^ ,' *• -titual.gtor«tH

;

»f

"•»«Ml

*4<-£?0 %^^

——

ö

30 ri«i. 26,27

1 1 II 1 1 1 3 blades 4 . 6 - 6 • dual-rotating 8 •

— J • geared 1.4:1 ••" 6 • • • auo/ rotating

t--- 5 5 ̂ s ij

r"-"

3J -j

& ̂ ̂ * -- •*' #-

40 .;

,^

N 's gM - * *

'" .-J

s 5 ii •' <s V ,; *"•

"-13

ü- A»

-m •O .« 1.6 2.4 3.2 40 48

V/nD

Flgir« 26.- Variation of ««and p «ith V/nD for Mitral propallarf at *V • 0.4.

t

27C 360 Activity 450

factor 540 630 720

1 i- •

• 36 .4

-. •

| * 2

28

20 ^ \Cr- l ^

14 5 6 7 Mjmber of blades

."i.ur. .'?.- YvltMofi of •t.ttr thniM •itfi ..1W"

TTTLE: The Selection of Propellers for High Thrust at Low Airspeed

AUTHORIS): Biermann, David; Conway, R. N. ORIGINATING AGENCY:National Advisory Committee for Aeronautics, Washington, D. C. PUBLISHED BY:

ATI- 6394

ARR-L-483 u

Ott'41 I linr.las _Eng_ 30 30 photo, tables, dlagrs. graphs

fi/T fa r*J fr^c/icc c uHioDIM A# Problem of improving thrust at low speeds is primarily one of reducing angle of attack

of operation of sections to improve L/D or reducing blade helix angle. An analysis, based on recent propeller data, is presented for determining Improvements in thrust or efficiency which could be obtained by increased number of blades, Increased blade width, Increased diameter, dual rotation, and two-speed gearing. All methods were found very effective, particularly two-speed gearing.

DISTRIBUTION: Copies of this report obtainable only from Originating Agency DIVISION: Propellers (11) SECTION: Aerodynamics (1)

ATI SHEET NO.: R-U-l-7

SUBJECT HEADINGS: Propellers - Aerodynamics (75478); Propellers - Lift-drag (75478.95); Propellers - Performance (75479.28); Thrust measurement (94100)

Air Mulai iaJ Commond AIR TECHNICAL INDEX Wright-Poti.Mon Air fort» I

Do y ton. Ohio

TITLE: The Selection of Propellers for High Thrust at Low Airspeed

AUTHOR(S): Biermann, David; Conway, R. N. ORIGINATING AGENCY:National Advisory Committee for Aeronautics, Washington, D. C. PUBLISHED BY:

ATÜ- 6394

WOUSMNO uaasa KO.

"<*• 41 Ilnclaga I' S- _EnS- SMXB

30 numu-.ne»

30 photo, tables, dlagrs. graphs ABSTRACT:

Problem of improving thrust at low speeds is primarily one of reducing angle of attack of operation of sections to improve L/D or reducing blade helix angle. An analysis, based on recent propeller data, is presented for determining improvements in thrust or efficiency which could be obtained by increased number of blades, Increased blade width, increased diameter, dual rotation, and two-speed gearing. Ail methods were found very effective, particularly two-speed gearing.

DISTRIBUTION: Copies of this report obtainable only from Originating Agency DIVISION: Propellers (11) SECTION: Aerodynamics (1)

ATI SHEET NO.: R-11-1-7

SUBJECT HEADINGS: Propellers - Aerodynamics (75478); Propellers - Lift-drag (7547B.95); Propellers - Performance (75479.28); Thrust measurement (94100)

Air Documents Division, Intotllnonco Dopartrncftt Air »staticl r

am TECHNICAL inw WrigM-Porronon Air Fores Boss Dayton, Ohio