RESEARCH MEMORANDUM PRELIMINARY RESULTS OF AN INVESTIGATION OF THE EFFECTS

O F SPINNER SHAPE ON THE CHARACTERISTICS OF AN

PROPELLER, INCLUDING THE CHARACTER- ISTICS OF THE PROPELLER AT

NEGATIVE THRUST

By Robert M. Reynolds

Ames Aeronautical Laboratory Moffett Field, Calif.

NACA D-TYPE COWL BEHIND A THREE-BLADE

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NATIONAL ADVISORY COMMLTT'E - . - 8

FOR AERONAUTICS NrJV 1 9

NACA RM A 5 9 0 2

NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS . RESEARCH MEMORANDUM

PRELIMINARY RESULTS OF AN INVXSTIGATION OF THE EFFECTS OF SPINNER SHAPE OM TEE CHARACTERISTICS OF AN

NACA D-TYPE CCHL BEHIND A THREE-BLADE PROPELLER, INCLUDING THE CHARACTER-

ISTICS OF THE PROPEUXR AT NEGATIVE THRUST

By Robert M. Reynolds

SUMMARY

c

An investigation has been conducted to determine the effects of spinner shape on the pressure-recovery characteristics of an NACA 1-series D-type cowl operating behind a three-blade single-rotation propeller. Two spinner shapes were considered, an NACA 1-series spinner and a modi- fied spinner, more nearly conical than the 1 series. The aerodynamic characterietics of the propeller operating ahead of the cowling and also operating on the isolated 1-series spinner were also determined. The negative thrust characteristics of the propeller-spinner combination were measured at lar speeds for blade angles from 25' to -2OO.

Some of the results of this investigation are being made available in preliminary form in this report in order to expedite their release.

INTRODUCTION

A t the present time there are several new turboproppowered airplanes in an advanced stage of development. These airplane designs have the common problem of providing efficient air induction for the turbine engine.

It is the purpose of the present report tosummarize the results of 'tests made to compare the ram-recovery characteristics of a D-type cowl behind a fairly thick three-blade prapeller in combination with an NACA 1-series and a modified-conical spinner. Also, in summary, the maximum efficiency of the propeller operating ahead of the cowling is comgared with the maximum efficiency of the propeller operating on the isolated

fi

m 1-series spinner. The low-speed characteristics of the propeller

2 - NACA RM A53J02

operating under negative thrust on the isolated 1-series spinner are included.

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- "- 1

The present results are offered without discussion in order t o permit their release ahead of the more detailed results of the investl- gat i on. . .

SYMBOLS

a speed of sound, f t /sec

b blade width, f t

'd blade section design l i f t coefficient

power coefficient, - P Pn3D5 CP

rn

D propeller diameter, f t

b - blade width r a t i o D

H t o t a l pressure, lb/f t2

H1-Po ram-recwery r a t i o %-Po

h maximum thickness of blade section, f t

h - blade thickness ratio b

J propeller advance ra t io , - VO

Ma

nD

datum Mach number, - v a

n propeller rotational speed, r p s

. . .. .

. ..

P power, ft-lb/sec

NACA RM A5902 " .

LC 3

static pressure, lb/ft2

propeller t ip radius, f t

blade-section radius, f t

thrust , lb

thrust coefficient, - T P F I ?

datum velocity (wind-tunnel air-stream velocity corrected for sol id blockage of cowling but uncorrected for wind-tunnel-wall constraint on the propeller slipstream), ft/sec

equivalent free-air velocity (datum velocity corrected for wind- -

tunnel-wall constraint

inlet-veloci ty ra t io

propeller blade angle at

design propeller section

efficiency, - or - J Tvo CT P CP

on- the propeller siipstream) , f t /sec

mass density of a i r , slugs/ft3

Subscripts

0 free stream

1 location of rake in cowling i n l e t

a apparent (applied to values of thrust, parer, and efficiency measured for the propeller operating in the presence of the cowling)

4 NACA RM A 5 9 0 2

The m o d e l of the cowl and propeller waS mounted on the 1000-horsepower propeller dynamometer (described i n ref. 1) in t he t e s t section of the Ames =-foot pressure wind tunnel as sham in f igure 1. Figure 2 is a sketch of the general m o d e l arrangement shlrwing the prin- c ipa l model dimensions. The inlet area of the model w a s scaled (epprox- imately 1/4 s i z e ) t o match the air requirements of the Pratt-Whitney T-34 engine. Coordinates for the cowling and spinners are given in table I. The three-blade propeller used for this investigation has the designation MACA 3.638-( 675) (O57)-057i. Blade-foriicurves for the propeller are presented in figure 3. The platforms between the propel- ler b lades and the spinners were fixed to the spinners a$ a local blade angle of 83O and had the dimensions and coordinates.given in figure 2 and table I, respectively.

" .

The instrumentation of the cowl and the methods used in obtaining ram-recovery r a t i o and inlet-velocity ratio were the same as described in reference 2, except. that for this investigation the total- and s ta t fc- pressure rake8 were made up of six tubes each in p lace of the eight-tube rakes employed in the tes ts of reference 2. The methods used in deter- mining the thrust , power, and efficiency of the. propeller when operating on an isolated spinner and when operating ahead of a'cowl.ing were the same as described i n references 1 and 3, respectlvely. For the propeller operating under negative thrust a-tthe larger negative blade angles, the minimum advance r a t io was l imi t ed t o the corresponding value of T, at which the theoreticare-fTects of the tunnel-walls could be confirmed from measurements of w a l l pressures.

TESTS AND RESULTS

.. I

Summary c w e s sharing the ram-recovery r a t i o as a function of in le t - ve loc i ty ra t io for the cowl with the two diff-erent spinner shapes are presented in figure 4 fo r Mach numbers from 0.2 t o 0.8 with the propeller removed. Similar data are presented i n figure 5 for the propeller oper- a t ing a t var ious cambinations of Mach number, blade angle, and advance rat io.

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The maximum apparent efficiency of the propeller operating ahead of the D-type cowl is sham as a function of Mach number and blade angle i n figure 6. These data are a l l for an inlet-velocity ratio of approxi- mately 0.5. The maximum efficiency of the propeller with the 1-series spinner with the cowl removed i s a l so sham in th i s figure. Note tha t a t , t h e higher Mach numbers (0.70 and 0.80) the propeller blade angle is so large that the inner portions of the blade are a t loca l angles greater

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NACA RM A53JCE 5

than goo. Stress limitations of the m o d e l propeller prevented testing at a hfgher rotational speed and, thus, the propeller characteristics at lower blade angles could not be measured at these Mach numbers.

The aerodynamic characteristics of the propeller operating under conditions of negative thrust at a forward Mach number of 0.15 axe shown in figure 7 8 s a function of sdvance ratio and i n figure 8 as a function of propeller blade angle.

All data presented herein were obtained at a Reynolds number of 1.0 million per foot, based on the datum velwity.

Ames Aeronautical Laboratory National Advisory Committee fo r Aeronautics

Moffett Field, Calif., Oct. 2, 1953

1. Reynolds, Robert M., Buell, Donald A., and Walker, John H.: Inves- tigation of an MACA 4-(5) (05) -041 Four-Blade Propeller With Sev- eral Spinners at Mach Numbers Up to 0.90. NACA RM AZIlga, 1952.

2. Sammonds, Robert I., and Moa, Ashley J.: Effects'of Propeller- Spinner Juncture on the Pressure Recovery Characteristics of an NACA 1-Series D-Type Cowl in Combination With a Four-Blade Single- Rotation Propeller at Mach Numbers Up to 0.83 and at an Angle of Attack of Oo. NACA RM A52DOla, 1952.

3. Reynolds, Robert M., Sammonds, Robert I., and Kenyon, George C. : An Investigation of a Four-Blade Single-Rotation Propeller in Combination With an FIACA 1-Series D-Type Cowling at Mach Nunibers Up to 0.83. NACA RM ~ 5 3 ~ 0 6 , 1953.

6 - NACA RM A53302

TABLE I.- COWLING-SPINNER COORDINATES

[Coordinates in inches]

0 .e84 -363 .443 ,516 .580 .641 .751

1.U4 .945

1.403 1.693 1.891 2 271 2.553 2.817 3 035 3 . w 3 3s . 3.&5 3 478 3 .44 3.499 3.499

0 -065 . I21 .181 .e41 .303 .3€Q .483 .P5 ,966

1.450 1.933 2.4l6 3.382 4.34

6 . m 5.307

7.248 8.lw 9.167 10.139 10.613 10.814 "

P h t f a r n

-h, juncture

;r,

0 .343 470 .650 9813 .985

1.019 .946 9803 .Q8

.e40 9 435

0 "- -"

1

NACA RM A53J02 7

Figure 1.- The model mounted on the 1000-horsepower propeller dynamometer in the =-foot pressure wind tunnel.

~ K N A C A 3.638 - (675)(057) - 0572 Detail 'A'

3.54

cowl 1

. "Model center line 11 ' Model center line

\.Rarn-recovery- rake location

Note: Dimensions shown In inches

Figure 2. - Model arrangement.

8 .

.40

.36

-32

~ .28 L \

- c 0' .24 E

.20 a E r u E . I 6

'0 0

0

.O 8

a4

0 0 .t .2 3 .4 .S .6 -7

Froctton of tip mdfua, r/R

Figure 3.- Plan-form and blade-form curves for the model propeller having the designation NACA 3.638-(675)(057)-0572.

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.

.

NACA RM A53502 - 9

.. - .2 -4 .6 .a 1.0

Inlet - velocity rat io, V J V

1.2

Figure 4.- The effect of inlet-velocity ratio on the average ram-recovery ratio for the cowl with 1-series and modified-conical spinners, prop- eller removed. Mach numbers from 0.20 to 0.80.

10

1.0

.9 I I I I I I I I I I I

.9

.8 I-series spinner Modffled-conical winner

.? / I I . j-357

/ .2 .4 .6 -8 I .o 1.2 1.4

Inlet-velocity ratio, VI/V

(d) Ma = 0.50; = 48O; J = 2.43 1

Figure 5.- The effect of Inlet-velocity r a t i o on the average ram-recovery r a t i o f o r the cowl with 1-series and modified-conical spinners, prop- eller operating.

-

-. -.

NACA RM A53502 z- 11

( e ) = 0.60; B = 53O; J = 2-82

(f) & = 0.70; fi = 9 . 5 O ; J = 3.40

.Y

!/ I-series spinner 7 "- Modified-conical spinner

// I 1

.6 .2 .4 .6 .8 LO 1.2 I .4

Inlet-velocity rat io, U / V ( g ) = 0.80; /3 = 9 . 5 O ; J = 3.30

Figure 5.- Concluded.

. . . .. . . . . .. .

.9 0

0 Y

6 CF .eo

.70

-6 0

and cowl. y/V, 0.5 , Tamax

(no cowl), Tmax

.50 -- Propeller with I-series spinner \

1 I

3 O

\-qi&7 .40 I - F

.I .I! .3 4 .5 -6 .7 .e .9 * Datum Mach number, Md z

cl

ul * W -

Figure 6.- The effect of I&& number an the msximm efficiency of the p r o p a r . 2

. . .

.

r

.2 4 .6 1.0 2.0 4.0 6.0 10.0 15.0 Advance ratio, J T

(a) VS. J

Figure 7.- Characteristics of the propeller in negative thrust; Q = 0.15.

14

a 0 0 cu I

dh

4.5

4x)

3.5

0 n ,3.0

2.5

2 .o L

1.5

1.0

.5

0

- .5

-1.0

(b) Cp VS. J

Figure '7.- Concluded.

NACA RM A53J02

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WlCA RM A53J02 "I

Figure 8.- The effect of blade angle on the characteristics of the propeller in negative thrust; Q = 0.15.

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t t