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NATIONALADVISORYCOMMITTEEFOR AERONAUTICS

TECHNICALNOTE

No. 1784

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FLIGHT DYVESTI~”TION IN CLIMB AND AT HIGH SPEED OF

A TWO-BMDE AND A THREE -BLADE PROPELLER

By Jerome B. Hammack

Langley Aeronautical LaboratoryLangley Field, Va.

Washington

January 194

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‘mcHmcAL NOTENo● l@4

FIZG3TINVESTIGATION IN CIJM3 AND AT HIGH SPEEDOFc

A TWO-BLADE JU4DA TED3EE-BIAIEPROPELLER

By Jerome B. Ebmmack

As part of a flight program at the NACA to obtain information ongeneral propeller aerocQnamic characteristics, an investi@tion has beenmade of a two-blade and a three-blade propeller on a slender-nose fi@terairplane in climb mxl at high speed.

In climbs, tie ~ropeller efficiency varied with both change inoperating engine power and change in blade number. For nozmal ratedengine power (XO hp ti 2630 rpm) the propeller efficiency was higherthen for military power (1200 hp and 3000 rpm), being on the order of4 percent higher at 12,000 feet with a three-blade propeller. With atwo-blade propeller, the propeller efficiency was approximately the sanefor normal rated ad military power at altitudes below “12,000feet. Ataltitudes above 32’,000feet, the propeller pfficiency for the mil3tez’y-power condition increased by about 6 percent at 20,000 feet because of thepower drop when the critical altitude was exceeded. A change in bladenumber from three to two resulted in a decrease in propeller efficiencyfrom 8 to 14 percent for the normal-rated-power condition md about6 to 7 percent for the military-power condition. ~s loss in effi-ciency was due to increasing the power loading’per blade which tookplace when the blade nuriberwas changed.

In high-speed flight at a Mach nmiber of O.7, prope~er efficiencyincreased 17 percent when the power coefficient per blade was increasedfrom O .07to O .17 at the normal engine rotational speed of 2&)0 rpm; thusthe propeller efficiency is shown to increase with power coefficient athi@er speeds. Further improvement might have been obtained if thepropeller had been tested at hi@er loadings, since the values of effi-ciency continued to increase up to the highest loadings used in thetests. Compressibility losses occurred at hi@ speed whenever a tipMach rnmber of O .9 was reached and increased in severity with furtherincreases in tip Mach ntier. The main sources of efficiency losswere the shank and tip sections of the blade . Tip compressibilitylosses could be miniml.zedby reducing rotational.speed. When the tipMach nmiber was reduced from O .96 to O .82 at the seineblade powercoefficient (O .13) and advence ratio (2.5), the propeller efficiencyincreased by 4 percent. -

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2 NACA TN No. 1784

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As part of a f13.ghtprogrm to detemnine the aerodynamic character-istics of various propdlere, tests have been made~of two-blade andthree-blade propellers on a high-speed fighter airplene.

The unrestricted free-etreem flaw about the spinner snd nose ofthe airplane used for the tests is especially suited.to the study ofpropeller shsnlm. The shank problem has %een discussed in reference 1from some of the data obbataea in this series of tests. Completeresults ofhigh-speed

the tests on this propeller are presented; and cm andcharacteristics,

number of blades

as affected by blade loading, are discussed.

SYMEOIS

blade width (chord), feet

power coefficient()35

power coefficient per blade for a two-blade propeller

power coefficient per blade for a three-blade propeller

section lift coefficient

design sectioi lift coefficient

lift coefficient at O .7 radius

()thrust coefficient +pn2D5

coefficient

in air, feet per second

element thrust

s-peedof sound

propeller diameter, feet

drag, pounas

blade section madmnun thictiess, feet

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advance ratio (V/nD)

lift, pounds

airplene Mach number (V/c)

helical tip Mach number

propeller rotational speed, revolutions per second

enghe power, foot-pounds per second ‘

propeller tip radius, feet

radius to a blade elenmnt, feet

radius to a survey point, feet

thrust, pounds

true airspeed, feet per second

fraction of propeller tip radius (r/R)

blade angle at any

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Cp

density, slugs per

radius, degrees

cubic foot

PROEEJICERAND TEST EQUDMENT

Blade-form curves for the propeller tested ere shown in figure 1.The shanks are characterized by a rapid transition from thin sectionsalong the blade to round sections at the roots. The airplane used wasa fighter-type airplane having an engine installation which permits aslender nose shape. A photograph of the airplane in flight is shown infigure 2.

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Qther pertinent propeller

Propeller characteristics:

and engine

NACA TN No. 1784

specifications are as follows:

Propeller diameter, feet ● .....0.............................. =.08Desi@ lift coefficient ● .*......*............................. 0 ●5Blade activity factor ...................’....*...........0.... 130Blade sections ....................................... NACA 16 seriesCalcul.ate&design adwnceratio ...>.......................... 2.5 ,Calculated design power coefficient per blade................. o .Y2

Engine characteristic:Designation .............00...0......00............ Al13son ~-171.O-93Propeller gear ratio ......................................... 2.23:1Normal power rating:

-e speed.,rpm ....*...................0................ 2&loMemifold pressure, inches of mercury ...................... .38Horsepower ................................................ 900Critical altitude (approximately),feet ................... 24,OOO

Military Tower rat-: “

-e wed, rpm ..................● .0 ... ... ... ● ......* . .. 3000Manifold pressure, inches of mercury ...................... 5Q’Horsepower ................................................ 1200 ,Critical altitude (approxbnately), feet .● .....*......● 0... 16,000

PmpeUer torque was measured hy an NACA hydraUc torquemeter. Thehydraulic torquemeter was s~lar to the torquemeter used in reference 2

.

~a measuredtorque by balancing propeller counter torque against ahydraulic piston, the oil pressure withi.nthe hydratic cylinder heingproportional to propeller torque. Torquemeter oyeration was checked b’

frequently by seveml recalibration during the tesi program. Fromthese checks the torquemeter meammments were beleived to he accurateto within 9 percent.

Propeller thrust was measuredbythe slipstream-surveymethod

described in reference 3. The survey rake was located about 3* feet

(O.32D)behind the plane of the propeller and can be seen mounted onthe airplane with the two-blade propellerinstallation in figure 3.Standard.NACA recording instruments were used to determine engine speed,-t pressure, static pressure, and free-air temperature.

TESr ERwEmREs .

Climb tests.- With engine speed, manifold pressure, and indicatedairspeed held at desired values, short records were tdcen at prescribed

+

intervsls as the airplsne climibedfrom sea level to altitude.

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NACA TN ~0. 1784 5

Data were obtained in the following contitione, all at an indicatedairspeed of 165 miles per hour:

(1)

(2)

(3)

(4)

Normal rated power, three blades.

Militez’ypower, three blades.

Normal rated power, two blades.

Military power, two blades.

High-m eed tests..- All high-speed runs were at en altitude of20,000 feet. Each ~ was made at falues of engine speed, tO??W3 Y and .

indicated airspeed selected to ptiduce a desired conibinationof veluesof airplane Mach number, propeller ad~ance ratio, and power coefficient.Because the airplane was usually cldmbing or diving during each run,only engine speed, torque, and airspeed could he fixed. These valueswere held constant as the airplane passed through an altitude of20,000 feet, where a short re~ofi w& taken. -

REDUCTION OF DATA

‘Themethods for reduction of recorded dataoutlined.in reference 3. h calculating values

were similar to thoseof propeller efficiency,

the effect of slipstream rotation on th~ total-pres-&r~ measurement waa-neglected. This effect, which is discussed in reference 4, is a functionof advance ratio, number of blades, and.power loading. The uncorrectedvalues, although from 3 to 4 percent too high, are nevertheless suffi-ciently accurate for comparative purposes, in that differences incorrection are small over the test range.

RESULTS AND DISCUSSION

Climb tests.- The behavior of the propeller in %oth a three-bladeand a two-blade configuration h climbs at an indicated,airspeed of165 miles per hour is shown in figures 4 to 7. These figures show theeffect of increasing the power coefficient per blade by approximately50 percent in climbs at both normal rated and milltary power.

Exact values of the mount of increaae inplotted as the ratio Cp2/Cp3 against advance

figure 8.

power loading per bladeratio J are shown in

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Fordata are

NACA ‘TNNo. 1784

the normal-rated-power condition with three hades the measuredshown in figgre 4. Derived values of section lift coefficient

are shown in figure g(a). For the ran@_ of section lift coefficient.covered the lift-drag ratio (L/D) is increasing with increasing 13ftcoefficient (reference ~). The Troleller efficiency varies from 88 to90 percent.

Decreasing the nuniberof blades from three to @o increases thepower per blade as shown in figure 8. h the nomal-rated-power climbcotition this increase in power loading is accOmptied by a decrease inefficiency (fig. 5). The decrease of propeller efficiency with sltitudeis due @marily to increasing the lift coefficients beyond,the mostfavorable L/D range into the stall region. The slight increase at theend of the clhh is due to a reduction in power loading, accompanied byreduced blade Hft coefficients which resulted @ decreased Drofiledrag losses. The variations in’lift coefficient are shown in figure g(b).The efficiency varies from74 to & percent thmmgh the clhib renge, adecrease of 8 to 14yercent from the lower blade loading. Efficienciescalctiated by msens of references 6 and 7 show a loss of the ssmema+git~e under these conditions. This decrease in operating efficiencyis caused by (a) raduction in the nuniberof blades which increased thetiucea losses end (b) increased profile drag losses, both becquse ofthe higher angle of attack of the blade element end.because of theapproach of the blede element to the stall region.

Results obtained with the three-blade propeller in a military-power cMib are shown h figure 6. Propeller efficiency varies from83 to ~ percent. The increase at altitude is attributed to a reduc-tion in axial energy losses with ticrease in forwerd speed. When thepower coefficient per blade is increased by using a two-blade progel.ler(fig. 7) instead of a three-blade propeller the efficiency drops tovalues between 77 @ 80 percent through the same range, a differenceof 6 to 7 percent. Variation of section lift coefficients for military-power cliribin both a three-blade and two-blade configuration can beseen in figures 9(c) and 9(d).

Changing the blade number from three to two for normal rated powerwas found to decrease the efficiency by 8 to 14 percent, depending onaltitude. This ssme change in blade nuniberfor the military-powercoxiiitionproduces a decrease in efficiency of o- 6 to 7 percent.This smeller efficiency drop results from the fact that the powerloading on the blade is not changed so drastically in the military-power condition, as can be seen in figure 8.

A comparison of the efficiency of the three-blade propeller atno-~ power (fig. 4) end military power (fig. 6) in cliaibshows thatthe efficiency is higher at nomnal power, being of the order of 4 percent ●

higher at 12,000 feet. Figure 10 shows a comparison of the propeller char-acteristics in the normal-rated and military power conditions. AS shown

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NACA TN No. ‘1704 7

in figure 10, this higher efficiency at normal power is to be expectedbecause, at eny given altitude, the propeller at normal Tower operates atlower tip Mach numbers, higher values of J, and at approximately thesame value of Czo .~ as the propeller at military ~wer. The effi-

ciency at military power increases from 83 ercent at 4000 feet (J = 1.o6)

tto approximately 87 percent at 16,~0 feet J = 1.28) b spite of anincrease in tip Mach nmiber fram O.73 to 0.78 end an increase in CZ

o .7Rfrom O.75 toO.83. This increase of efficiency with altitude indicate~that the increase in J (fig. 10) has the yrincip.1.effect and that thesections are apprentl,y operating at subcriticalMach numbers. similarly,reduction h efficiency at militery power from that at normal power at agiven altitude must be ascribed chieflyto the lower mhzes of J atmiliterypower in the climbing range. Similerly, a comparison of theefficiency of the two-blade propeller at both nonnel power end militarypower shows that the propeller efficiency was approx3me.telyconstant ataltitudes below 12,000 feet. At altitudes aboye 12,000 feet, the pro-peller efficiency increased when mil.itarypower was used to the extentthat at 20,000 feet a gainin efficiency of the order of 6 pprcent wasobtained as a result of the decrease inpower when critical eltitude wasexceeded.

Thrust gradient curves obtained at military power for both three-blade end two-blade operatio~ axe shown in fi~es 11 and 12. Thecurve”sshow no compressibility effects. l?eitherwere compressibilitylosses evident in nomal-rated-power c-s.

High-speed tests.- For the high-speed investigation,“theairplane wasflown at speeds from a Mach number of 0.3 to a Mach number of O.~ for arange of power coefficient per blade from O.07 to 0.17. The high end ofthis range was made possible by reducing the number of’blades from threeto two.

The effect of blade power loacMng on propeller efficiency is shownin figures 13 end 14. Runs for figure 13 were made at an engine speed of2&10 rpm and runs-for figure 14 at en en~ne speed of 3000 rpm to determinethe effect of tip Mach number. The effect of blade loading on efficiencyat a Mach number 0.7 is presented in figure 15. At a forwerd Machnuniberof 0.7, the efficiency of the pfipell.erincreases with powercoefficient per blade. Figure 15(a) shows the variation of propellerefficiency with shenk losses included. As pointed out in reference 1,shed losses reduce propeller efficiency for this propeller less aspower loading is increased at high speeds, and this fact accounts for mostof the improvement shown. Figure 15(b) presents the vtiation inpropeller efficiency when shed losses are omitted. Data for shanklosses were obtained from reference 1. The improvement in propellerefficiency with blade loading as Shown in figure 15(b) results fromthe decreased profile drag resulting from propeller sections operatingat more fayorable L/D ratios. Lift coefficient values for a typical

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8 NACA TN No. 1784

run are shown in figure 16. These data show that, at a blade power coef-ficient of O .17, the blade sections exe operating at very nearly the designlift coefficient of O.5. I?igure15(a) shows that, at an engine speed of

,?

2&30 rpm, increasing the power coefficient per blade from 0.07 to 0.17(an Wrease of 0.10) ticreases the propeller efficiency at a Mach nmiberof O .7 from 65 percent to & percent or en increase of 17 percent. At anengine speed of WOO rpmj increasing the power coefficient per blade from0.07 to 0.13 (O.13 being the msxdmmm value obtainable at an engine speed of3000 rpm) ticreased the efficiency at a Mach nuniberof O.7 from @ percentto 74 percent. The decreased efficiency at an engine speed of 3000 rpm ascompared with that at 2600 rpm is due to the higher tip Mach numbersassociated with the hi~er rotational speed. At an airplane Mach nuniberof O.7, the tip Mach number is O .95 for en engine speed of 2@0 rpn and1.03 for an engine speed of 300 rpm.

The main sources of efficiency loss in hi@-speed f~ght with thisblade design are present at the tip and shti sections of the blade.Compressibility losses are generaUy known to begin at the tip and to proceedinboez’dprogressively with increasing speed. This shift in load unloadsthe outer sections of the blade and reduces the part of the disk areathat carries the load; the load Orithe inboard section is thus ficreased.Tip losses can %e seen graphically in figures 17 md 18, which aretypical thrust distributions. Figure 17 is for the “lowestpower coeffi-cient per blade obteined, and figure 18 is for the highest. Losses dmeto comprebsibility are evident whenever tip Mach numbers of the orderdf O .9 are attained. These losses could be reduced by reducing tipspeed. For example, at an advance ratio of 2.5 and power coefficient

‘per blade of 0.13, a reduction in tip Mach numiberfrom 0.95 to 0.82increase-sthe propeller efficiency by approximately 4 percent. For higheradvence ratios, larger gains would be re&l.zed. The data of figures 17end 18 show that the shank sections account for a large part of theefficiency 10ss. The negative area shown represents drag and variespr3ncipaUY with airplane Mach number. This loss appears to be relativelyindependent of power loading. Losses due to the shanks of this propellerhave been discussed ftdd.yin reference 1, which points out that thelosses are caused by thick airfoil.sections in the shank region. Aswas stated in reference 1, shank losses account for an efficiency lossof appro-tely 9 percent at a Mach nmiber of O.7 at a test powercoefficient of O .17 per blade.

The propeller used in these tests has relatively high efficiency‘ata forward l&h number of O.7 when operated at the highest test powercoefficient. This efficiency might be further Improved by increasingthe power loading and aero@mmically @roving the shank sections. Anincrease in power loading, however, would be detrimentsllfor clbibingperfonmnce as shown in the section on “Cm tests.“ Shsnk sectionscould be improved either by increasing the spinner dimeter as repotiedin reference 1 or possibly by cerrjing thin airfoil sections into thespinner. Both of these methods apply only to high-speed fli@t ~ asshank losses are neglible in climbs.

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NACA TN No. 1784

CONCLUSIONS

9

Flight investigations of a three-blade and a two-blade pwpellermounted on a slender-nose fighter airplane indicated the followingconclusions:

1. For three-blade operation, the propeller efficiency in cldmibswas higher for normal rated power than for military Tower, being about4 percent hi@er at an altitude of X2,000 feet. For two-blade operation,the propeller efficiency was appromtely constsnt at altitudes below12,000 feet. At eltitudes above 12,000 feet, the propeller efficiencyincreased when military power was used to the extent that at 20,000 feeta gain in efficiency of the order of 6 percent was obtained as a retitof the decrease in power when criticel altitude was exceeded.

2. When the blade number was changed from three to two, the propellerefficiency decreased about 8 to 14 perce’ntfor the normal-rated-powercondition and about 6 to 7 percent for the military-power conditionbecause of the increase in power loading per blade.

3. At a Mach nuniberof 0.7 with sn engine speed of 2@0 rpm, propellerefficiency increased 17 percent as a result of increasing the power coeffi-cient per blade from O .07 to O .17; thus the propeUer efficiency is ~oundto increase at high speeds with increased power loading per blade.

4. Compressibility losses appeered with this blade desi~ at a tipMach nurtiberof about 0.9.

5. The main sources of efficiency loss were present in the shankand tip sections of the’blade. Tip losses could be minimized byreducing rotational speed, as when the tip Mach numiberwaa reduced from0.95 to 0.82 at the sane power coefficient per blade (0.13) and advanceratio (2.5) the propeller efficiency increased by 4 percent.

.Langley Aeronautical Laboratory

National Advisory Conmittee for AeronauticsLangley Field, Vs.? November 3, 1948

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10 NACA TN No. 1784

1. Hemmack, Jerome B.: Investigation of Thrust Losses Due to Shanks of aFlared-Shank Two-Blade Prqeller on a Slender-Nose Airplane.NACA TN No. 1414, 1947.

2. 7ogeley, A. W.: Flight Measurements of Compressibility Effects ona Three-Blade Thin Clark Y Propeller Operating at Constant Advance-Dismeter Ratio and Blade Angle. NACA ACR NO. ~12 , 1943.

3. VO@ey, ~. W.: Climb end Hi@-Speed Tests of a Curtiss No. 714-lC2-12Four-Blade Propeller on the Republic P-47C MrTlane. NACA ACRNo ● L4L07, 1944●

4. Pankhurst, R. C.: Jdrscrew Thrust Grading by Pitot Traverse: Allowancefor Rotation of Slipstream at IUgh Rates of Advance. R & K NO. 2049,British A.R.C., 1945.

5. Stack, Jo3n: Tests of Airfoils Desigaed to Delay the CompressibilityBurble. NACA Rep. No. 763, 1943.

6. HarIman, Edwin P., and Feldman, Lewis: Aerodynamic Problems in theDesign of Efficient Propellers. NACA ACR, Aug. 1942.

7. Crigler, John L., and Talkin, Herbert W.: Propeller Selection fromAerodynamic Considerateions. NACA ACR, July 1942.

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24 NACA !C!NNo. 1784

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Figure ~.- Thrust gradient curves for military-yower clhib with three-bl.adepropeller.

.

—— ———— . . . . . . . . .—. .— __ ..,. . .. ..7,

,.. .

. . . ..- .,’,.--, . ,-,. .

NACA TN No. 1784 25

●3

o

-./

.3

“2

-* /

.2 ..4 ..6”- a /2

o z .4 .96 ●6 Lo /..X52

(d)Nat Cd~_: ~ P .a.6 ~~~t; J . 1.32j ~ . O.@.; CT = 0.167’jIf= 0.303j~ n 0.7’84.

. .

Figure I-1.-Concluded. -

—~z— — -.—, —

. . . . . .

26

I

NACA ‘TNNO. 17~

.3

.2

&d(~#) J

o

-. /o ●2 ,4 ,6 .6 /.0 AZ

Xs 2

Figure 120- Thrust gradient curves for military-puwer climb with two-blade propeller.

.

,- .. —- -— ———. .- .–.-’7----”” .

,: .--, ‘- .’....”~~ ““

NACA TN

C7’c.

No. 17~

-.. 1

dc-5G’ff2

.&..

2’

w

T:/-

(C) Test .OIIMtiOIM: ~ .80.2 ~~tj J . 1.30;(!-p. o.~j ~ * O.lksjM . 0.300j ~ = 0.7@.

-“0 ,2 .4 .6 .8 Ao X2’AS2

Figure K?. Continued. .

27

-. . . .. —- ——-- -– —.—--—— .—~ ,------ — .. ——..,”

NACA TN No. 1784

*

.

.2

0

-J

+

/-w$

// Jwk?? \.$$

L$ Jt

W97°

,

.

#

. .————.-... ’..,, .-’”.. . ,,-,.:-- i,. ,,,..:, .-. ,,

.

NACA TN

f?>percent

.

No. 1784 &

/00

90

f30

70

6Q

(a) ~ .0.07.

Iw

9-0

80

70

60.

b) p = 0.14.B

100

90

/30 f

70- QY

60 1

50 (o)

.40- I I I I I I y

+— Q0.17.B

“ .2 ..3 .4 .5 .6 .7 .8M

I I I J 1 I f.7

Fi$ure 13. - Variation ofat

...—.--—. ——.-

f%

efficiency of tested propeller with Mach numberengine speed of 2600 rpm.

—-—------v ––-—— - — —. —

,,.

30 NACA ~ No. 1784

/00~

w

80c‘

/ 7

?0 - \

6-a-

-,

(a) ~ = O.q’.

90

%percf?nt 80

70

6& “

0) :-.0.09.

.

Figure 14. - Variation of efficiency of tested propeller with Mach nuniberat enghe 9peed of 3000 rpm.

,., .. ---~ ~ .,. .. . -, . ... ., .,-—. ---

.“’.

NACA TN No. 1784 31

q’, /30perceof

74

0 two-b/a de tests❑ three-blade tests

n>percen$

100

90

go

70

60

50

40.06 .08 ./0 ./2 ./4 ./6 ./8

PoAItmcoe/YheA per A&de

‘FiP l~.- Ei?fectof power loading on efficiency of teeted propeller atairplane Mach num%er of 0.7.

.

- —— -.——.——— ——— -—.,. —.-—.— —.,..’.

32 NACA TN No. 1784

.8

.6

./?

o

C2

/.2

/.0”

.8

,6

.4

.2

\\ \\\

\\. \

\

-1

(FL) ~=o.07.

x

o 0.5\\ o .9\

/ \/ \ \

{ \\\

.\ 1- \

<\<<. ‘~

\n

(b) ~= 0.17.

ysy’

,2 .3 ..4 ; .6 .7, .8

Fiv 16.- Variation of Cz of propeller tested with Mach number at hi@speeds. tigim speed, 2600 rpm.

.

.

.

. .. .,. —-. — —— —.. . ..-. ———-,-. . ‘., ..” .,.,-

NACA TN No. 1784 33

i.II

,2

,/ — –Jtznz?’ ,

;2

I

:30 .2 ,4 .8 @ /2”

%26

(a)!lbStctitl~z q .w.8~~~tj J=l.k5j Cpz 0.147jCT.0.W2;U. O.solj~ . 0.P8.

Figure 170- ‘l?hrusb gradient curves of tested propeller at high speed.Power coefficient per blade of 0.07 at an engine speed ,of2600 rpm.

.-— —---- . . --—.~-. —— — —— -. —...— _ -——. --— ———.- ——-——..- —.—-.,..

34.

,., . ,- .-, .— -, —,..’.. ,.

‘,. .

NACA TN No. 17a4 35

_.._.._- ..—--— —.- -–—~-....——— — —. -,.

—- —- —.- . . .,. ,.—

36

r

NACATN No. 17~

.

./

‘ &?/’.. T

. W!rveyI

I‘ :/ II

I4

-.

.

..

:6

77

“9p

o .Z 4 .6 .0 ho /.z%52

(d)!kd.d~~:~ =68.7’w~~tj J=3.aj ~.o.lssj ~EO.032;M= 0.6~j ~ = 0.938.

Figure 17.– Continued.

,.. . . ., ,.- .?’”’ , ‘:”’”—-——.,. ,

NACATN No. 1784

).

37

I

.

. .

(e) Testcmditions:q .153.8percent;J = 3.44;~ = o.148;% = 0.IM8;H = 0.76; ~ = o.yj~.

Figure 17 .– Concluded.

,— --- .. —-— _. —___-~-- ——------ —---— .’ -.-— -

. .

NACA ~ NO. 1784

3

.2

dCT ~

:2

I

:30 .2 .4 .6 .8 10 L2

2.*S .

(a)TestCOIIMtlCKIE:II.70.0 Pe=t; J . 1.b6j Cp . 0.31~j~ . O.1.~;M = 0.304;~ = 0.722.

FiY

18. - Thrust @ant curves of tested propeller at high speed.ower coefficient per llade of 0.17 at engine speed of 2600 rpm. “

. . . ... ... ..’ /...; . . . ,, ..’

NACA TN No. 1784 39

.

.

- ,- 1 I I \

n.—” m--i-md Q‘ suhey~l

ItkikfT.-’-y-l ,1--l-~l\.- ‘1 I I

. .QJ /’./$. II l~eft~l I I I I

I!JIIJ’I I I

I I I I -\I \ I I I

I

‘survey

NtlFi i i“# \.‘m&

~)I I I 1 I I I I I I I

0 J ●4 .6 .8 10 62X52

(’b)lbfi Odti-: n D 83.9 w-; J . 1.90j~ = O.mj CT O.lbljH . 0.3Hj Ht U 0.765.

Figure 18.– Continued.

— ...-. —. -— —.—,—— — —.-— —--——- — s“-.. —-—. — ––.——-—. .—— —4 —. . .

., . .

40 NACA ~ No. 178+

b

q I I I I I-- 1’-1 I I I I

survey \\

Figure 18.– Continued.

4

— ,— —..:,-: –,—-. ,.. —~ -— - .-.-,, .,, -,. . ,, . . ,,

1

.

NACA TN No. 1784 41

2-

. . .-

./ /~

0- b

1

I-J/ -

I

-2-

.3 .$-

*

-3

76

ao .2 .4 .6 ,8 Lo f!2 c

x~2

(a)!%Etwtl=: ~n @.O~l&lt;J = 3.*j Op n 0.328j~ n O.~jM . o.67zj ~ . O.=.

Figure 18.– Continued.

.

1

.-— —.—. — - ----- .-— —— --.-—------ -- —-. - ..—-

42 NACA TN No. 17@t4

.

.2 I

+ . ,Left >.survey

./ //

survey

o .

J / .

.-. I

G. -Q()

74---%- 3k

. . .7> I Iu I I I 1 1 I I , ,

I

.

——- ..—. —-- . ..—. n..--”—— .,.,. ~’...’ . ., -,.