1 .

I

NACA TM 655

EXPERIMENTS WITH INTUBED PROPELLERS

NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS WASHINGTON, DC

JAN 30

N O T I C E

T H I S D O C U M E N T HAS BEEN R E P R O D U C E D FROM

T H E BEST COPY F U R N I S H E D US B Y T H E SPONSORING

A G E N C Y , ALTHOUGH IT IS R B C O G N I Z E D THAT C E R -

T A I N P O R T I O N S ARE ILLEGIBLE, I T IS BEING R E -

LEASED I N T H E I N T E R E S T OF MAKING A V A I L A B L E

A S MUCH I N F O R M A T I O N A S POSSIBLE,

. T . ., . . ;. . . . . TEC"IIC.AZ:.,ME~ORAIQD~~~,^"Y) ;,+ .+5' : . . . . . . . :. i i . . .... . . . . . . . . - . I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ! . . . :.. ... _ . ,

3 , , %

. . . . . . . . , . . . . . - . : . . . . . . . . . . . 'Bi ,&... ,8$'ip,+ . . . . . .: . . . . . . . - .. . . . . . . . . . . . . . . . . . . . I :' .. - . L ' ! . . ' ! . . . . . . . _ I , I i ' . .

. . . . . . . . . . . . . . . . . . . . . . . . , , . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . t . : .

, . . . . . . * ....

. . . .: , . i . .

. . .

. I - .. . - ...

' . . > . .

. . .

T'h w r i t e r , f o l l o w i n g h i s a r t i c l ' e . pub'l.i.shed in"t ,he: A z r i l ? 1 9 3 1 number: o f L t A e r o t e c n i c a , und,er t h e t i t l e o f " ' A l a a Turbinal1 ( . turbfne wing), '-i'?.~lu.st.ra%~'s' t h e .-resu.lt s of t k e expe r imen t s w i t h h i s new method o f - p r o p u l s i o n and e xp 1 ai n s i t s , ndv.an t ag e s . In .' d e s c r i 'b; i n &'. t h e -e xp e r i ine n t s w i t h - p r o p e l l e r s dper.ated la . ca,Gjunc.tXon w i t % a Vmturi t u b e formi-pg the n l y fuse l ' ige l .o f . ; . th& " t u r b i n e w i t l g , 11 i t i s necessg ry . tie.' 'e . . . . a ' a i f f e r e n . t . . . "Iiam'e . . . . . . . . . f\p,oii: %>'e. -prerc'eding one . . . . . . , L ' . . . . . . . . . . . . . . . . . .

. _ 'WIND . T ~ E L TESTS ,~ITH~.PRoPELLER.~~O'~A~.I~G. .

. .

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

. . . . . AT A FXXED'::PO'I~~T . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -. % - . . . : . . : . < - ' - . . . . . .

The above-mentioged q r t , i c l e e x p l a i n s how t h e i n s i d e shape 0:f. t h e . . l o n g i t u d i n a l .sect5-'o,fi:.';of ' t h e ,Ventur i - tube

' f u s e l a g e i s of c a p i t a l . fnp 'or tance ' . f o r ' f B . e sl i 'ccess of *.he expe r imen t s . T h e e t y 2 e s of tubes were d e s i g n e d ( f i g . $1) by v s r g i 3 g tile i n s i d e shajje..and, i n t h e t k i r d t y p e , a l so

. . tLe ou t s - ide shape, whicll g a v e . d i f f e r e n t e x p e r i m e n t a l r e - su l t s . ' ' .

.

. . . . .

. -These fuselage t u b e s were aadq. an a 1:5 . s c a l e r T t w a s n e c e s s a r y t o adopt ' such a l a r g e : scale because t h e 'di- mensions o f the. t ube Xad t o c o r r e s p o n d t o t h e s i z e .of t h e

Exper imenters know t h a t : r e s u l t s . o b t a i n e d w i t h . a p r o p e l l e r nodel hav ing a . d i a a e t e r of l e s s . t h a n 50 c m

(about 20 i 'n . ) :a re n o t r e l i a b l e . .Heace , t h e . s c a l e of t h e p r o T e l l e r node l . . . b e i n g g iven , t k e s c a l e of t h e - f u s e l a g e model fo l lowed .

. : . p r o p e l l e r .

. . . . . . . . . .

'Eoreover; ' s i .nce t h e .€uselage had-to b e - a t t a c h o d t ' o ' t h e a r m s .of Ithe' wind- tunne l : ' ba l ance , i f ha&. t o be very

.+"Espqr$6nze.con !Elicne fn€ub&te . l t . L t A e r o t e c n i c a . . . . . . . . (Rome),

. 1 . . . . .

' . * ... . . . . . . ..: . . . ----- . . . ' . :

. . . . . . . . . . . . . _.-. . . . . . . . . . . . . . . . . .

August , 1934 , ' pp..::923,953;. ,

. . . . . I . . . . . . . . . . . . . . . . . . . . . . . . 1 : : , . . . . c .'. ! ......_...... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . r :, . . . . . . :: . . . . . . . ' . . . . . . , 1

. . **

. . . . . . . . ... ".. . . . L a . . r

_ _ X .A...G..A. T e c h n i c a l . m,eaorr?aC:r$. i;o.. 555. . . , . . . . .- . . . . . ... . . .

_. . . . . .

2

l i g h t . In fact, .it _yae ,;lade o f s b e e t - - a l y i n u m and d i d no t weigh over 10 kg (22 lb.). . (Zig.. 2.) The l a r g e s i z e of t h e f u s e l a g e model c r e a t e d d i f f i c u l t i e s i n t h e wind-tunnel t e s which w i l l be. c o n s i d e r e d l a t e r .

. .

, u -

Two p r o p e l l e r s were ch-osep f o r t h e wind- tunnel t e s t s : one from the seap lane C -R7-20,' t h e - ot l ier l r o m t h e S 59. These t w o p r o p e l l e r s d i f f e r c h i e f l y i n p i t c h , t h e C R 20 p r o p e l l e r having a p i t c h of 0.472 m (1.55 f t . ) and a d i - ameter o f 0.48 m (1.57 f t . ) , w h i l e t h e p r o p e l l e r of t 9 e S 5 9 has a p i t c h o f 0.41 m (1.35 f t . ) and a d i a m e t e r of 0,5205 m (1.71 f t , ) .

The fo l lowing t e s t s mere made with each p r o p e l l o r :

1, P r o p e l l e r a l o n e : 2.

, 3.. 11 i p p r e s e n c e of. Ventu r i - tube f u s e l a g e ; n i n t e g r a l w i t h ' I1 11- I I

. 4, R e s i s t a n c e . o f Ventur i - tube f u s e l a g e a t d i I ' f o r e n t r e v o l u t i o n speeds o f t h e p r o p e l l e r .

The f i r s t , t e s t mas made by a t , t a c h i n g t h e p r - o p e l l e r t o t h e a r m of the b a l a n c e o f t h e t u n n e l p r o p e l l e r s , ' m i t h t k c d e t e r m i n a t i o n o f t h e thrust T.m. developed by t h e p ro - p e l l c r and of t h e power I?. m. abso rbed by t h e p r o p e l l e r at d i f f e r e n t r e v o l u t i o n speeds o f t h e p r o p e l l e r .

D

?he t h r u s t . was measured i n k ' i l o g r a n s " and t h e powor i n ki logram-meters . The r e s u l t s : f o r b o t h p r o p e l l e r s a r e g i v e p in Tabla I,

* .

---1__--.c--

TABLE 1

P r o p e l l e r of C R 20

p e 11 e r ab -

p e l l e r p e l l e r kg ! kgm ' .

24.67 1.410 0.05711 2600 I 2600 3000 32.61 1.950 0,05981 3000 3400 3800

: 4200

--- - lrgn X '7.23298 = f t q - l b , kg X 2.20462 f 1%.

r !

1 I

i

c .

T o m . Power Thrus t

ab- p r o - r.p.m. so rbed duced of pro- by pro - by pro- p e l l e r p e l l e r p e l l e r

kgm kg ---_I--

2200 9.29 0.775 2 600 16.69 1.225 3000 27.0 1.700 3400 40.26 2.250 3800 56.36 2,815

27,Ai C I A ; Technica l . tdemoranc?ua 170. 655 ,3

-

%..E! W.m.

0.0834 0.0733 0.0530 0.0558

?be seconil t e s t w a s inade by a t t a c h i n g t h e p r o p e l l e r as above and p l a c i n g behind i t t i le Ven tu r i - tube f u s e l a g e '

( f i g , 3). which w a s a t t a c h e d t o the wind-tunnel wal l s . The s a i e d a t a were de te rmined for b o t h p r o p e l l e r s as g i v c n i n Table 11. These d a t a were o b t a i n o d w i t h t h e n o d i f i c d Ven tu r i - tube f u s e l a g e (2d s e r i e s of t e s t s ) .

4200 460G 5000

I pz;; 76.85 3.550 100.86 4.265 128.87 5.025 I0 .0390

.P r o ----

r.p.m. o f pro - p e l l e r

--- 2200 2600 3000 3400 3800 4200 4600

9.54 21.45

1.100 b.1153 1.875 jo.0~4

The t h i r d t e s t w a s made by a t t a c h i n g t h e p r o p e l l e r alone t o t h e b a l a n c e and s e c u r i n g f i r m l y t o t h e same arm t h e Ven tu r i - tube f u s e l a g e , so a s t o m a s c r e on t h e b a l a n c e t h e thrust r e g u l t i n g f r o m the t r a c t i o n of the p r o p e l l e r and f r o m the r e s i s t a n c e of the Ven tu r i - tube f u s e l a g e . (Fig. 4.)

Analogous data were determined by v a r y i n g t h e r.p.m. of t h e p r o p e l l e r . The r e s u l t s are g i v e n i n Tab le I11 and r e f e r t o t h e mod i f i ed Ventur i - tube fuse lage , which w a s used i n t he second s e r i e s o f ex- -er iments .

92.63 15.100 121.67 !6 ,100

0,0550 0.0500

c

N.A.C.A. Technica l Memorandum 170. 655 4

TABLE: 1x1

rep.m. of p ro - p e l l e r

1800 2200 2600 3000 3400 3800 4200 4600

.

.

e l l o r o

W .m. Power

ab- sorbed by p ro - p e l l e r

-

kgm IZC-

5.25

17.23

40.21 58.74 78.44

104.24

9.49

27 60

C R 20 2.m.

Thrus t p ro -

duced by pro- p e l l e r

kg

0.825 1,250 1,750

3.075 3.850 4.712 5.650

2.350

--.

P r o p e l l e r of S 59

- 1 - 30G0 j 36.86 3.175 /0.0851 3400 1 51.37 I 4.037 0.0786 3800 75.19 15.050 0.070~

6,125 000644 4600 1125.49 7.437 3,0592 :::: 1l;::o 18.150 0.0557

I !

I 1

The d a t a f o r t h e C R 20 p r o p e l l e r a r e p l o t t e d i n Fig- u r e 5 and f o r t h e S 59 iq , -F igure 6. I n o r d e r t o be b e t t e r a b l e t o de te rmine t h e d i f f e r e n c e between t h e v a r i o u s t h r u s t s and pomersunder the t h r e e d i f f e r e n t c o n d i t i o n s , i t w a s thought b e s t t o determine t h e r a t i o between t h e t h r u s t and t h e power at d i f f e r e n t r e v o l u t i o n speeds. This r a t i o i s g iven i n t h e f o u r t h colunn of Table I11 and p l o t t a d i n F i g u r e s 7 and 8 f o r p r o p e l l e r s C B 20 and S 59, r e s p e c t i v e - l y . The r e s u l t s c l e a r l y i n d i c a t e t h e advantage of t h e p ro - p e l l e r i n t e g r t r l w i t h t h e Ventur i - tubo f u s e l a g o over t h e s

p r o p e l l e r a lone and in the p r e s e n c o of t h e Von tu r i - tubs f u s e l a g e .

As t o what caused t h o g r e a t o r t r a c t i o n and t h e l e s s poner absorbed by t h e p r o p e l l e r i n t e g r a l w i t h t h e Tentu.ri- tube f u s e l a g e w i t h r e s p e c t t o t h e p r o p e l l e r a l o n e , i t ' w a s obv ious ly t h e r e a c t i o n ( n o t r e s i s t a n c e ) o f t h e Ventur i - tube f u s e l a g e , which w a s confirmed by t h e f o u r t h t e s t . I n t h i s t e s t t h e p r o p e l l e r a lone m a s a t t a c h e d t o t h e wind- t u n n e l ba l ance . This balance w a s s e c u r e d , however, i n 2. p o s i t i o n of s t a b i l i t y i n such a way as no t t o b e a f f e c t e d by t h e p r o p e l l e r t h r u s t . The f u s e l a g e m a s mounted near t ho p r o p e l l e r , as a l r e a d y shown, b u t suspended from a d i f - f e r e n t ba l ance , so as t o make i t p o s s i b l e t o v a r y i t s fo re -and-a f t p o s i t i o n accord ing t o whether t h e r e was a r e = s i s t a n c e o r a r e a c t i o n . (Fig. 9.)

. . . -_ . - . 1

.

P r o p e i ? e r .r'.p:.rn, --- i . L + ... Re si stcilce'. fn

grams ( r ea ' c t ina )

.

.-- ---- -- ..- 1844 -2208/. 2620

: : . :.. %.:

B . A . C . A . Technica l Keiaorandun !To, 655 5

By v a r y i n g t h e p r o p e l l e r r.p.m, f r o m a uiniinum - t o 'a maxinuin, e r e a c t i o n w a s always o b t a i n e d , t h o valGcs o f which a r e g iven i n TPzble IV and ? l o t t e d i n F i g u r e 10.

. .

. VIND-T'flTiGTEL TESTS

Thoso t o s t s w o r e made w i t h tho same C Ii 20 ant? S 5 9 p r o g o l l e r s , as f o l l o w s :

1. P r o p e l l e r a l o n e with wind v e l o c i t i e s o f 1 5 and 20' m (49,2 and 65.6 f t . ) per socoild;

2 , P r o p e l l o r i n presenco of Voatur i - tube f u s e l a g e w i t h w i n d v e l o c i t i o s o f 15 and 20 ra por second;

3, P r o p o l l o r i n t e g r a l w i t h Ventur i - tube f u s e l a g e v i t h wind v e l o c i t i e s of 1 5 a i ld 20 m p o r second;

.. N.A.C.A. Techn ica l ?demorand&m io. 655

t

4. Resis tance o f - Ventur i - tube , f u s e l z g e f r o m v a r y i n g t h e wind v e l o c i t y ; -

20 m/s at d i f f e r e n t p r o p e l l e r r.p.n.; 5. R e s i s t a n c e of Ven tu r i - tu3e f u s e l E g e w i t h wind o f

6. C R 20 p r o p e l l e r i n t e g r a l w i t h C B 20 . f u s e l a g e . *

For b r e v i t y , o n l y t h e r e s u l t s o b t a i n e d wit3 a wind v e l o c i t y of 20. m (65.6 f t , ) p e r second a r e e i v e n , s i n c e t h e r e s u l t s ob ta inod w i t h t h e mind v e l o c i t y of 1 5 m (49 f t . ) p e r second a r o ana logous t o t h e former.

t h e u n n o d i f i e d Ven tu r i - tube f u s e l a g e ( f i r s t s o r i o s or" cx- p e r i m e n t s ) , w i th t h e modi f ied fuse lage (second s e r i e s ) , and w i t h t h e second m o d i f i c a t i o n ( t h i r d s e r i e s ) , as shonn i n F i g u r e 1. The p r o p e l l e r m a i n t a i n e d t h e p o s i t i o n i n d i - c a t e d i n F i g u r e 11.

T e s t s 2, 3, 4 and 5 were e a c h made t!areo t i m e s w i t h

R e t u r n i n g t o t h e exper imentq w i t h t h e p r o p e l l e r r o - t a t i n g at. a f i x e d p o i n t , t h e e x c e s s i v e d imens ions of ' t h e V e n t u r i - t u b e f u s e l a g e have a l . ready been i loted. The v e l o c - i t y o f t h e a i r i n t h e t u n n e l m a s measured at a c e r t a i n d i s t a n c e ups t ream 2 r o m t h e model (Zig. l l ) , a a d , i f t h o model m a s ve ry l a r g e , i t d i n i n i s h e d t h e f r e e s e c t i o n of t h e a i r passago add c o n s e q u e n t l y i n c r e a s e d t h e vc1ocit:i.

I n o u r caso; t he d i a b e t e r o f t h o t u n n e l at t h e model i s 2 m (6.56 f t , ) w i t h a s e c t i o n o f 3.1416 m2 (33.82 sq.ft3. The model of t h e Ven tu r i - tube f u s e l a g e ( secon? s e r i e s ) h a s a g a r a s i t e s e c t i o n o f 0.28 m2 (3.01 sq,ft.). The wind v e l o c i t y o f 20 m/s, measured u p s t r e a m i a co r re spondence w i t h t 3 e model, i s 20 X 3.1416/2.8616 = 22, c r e a s e o f lo$ . I t should be bo rne i n mind that the r e - s i s t a n C e a l s o i n c r e a s e s w i t h the squa re o f t h e v e l o c i t y , b u t t h i s i n c r e a s e i s d i s r e g a r d e d i n t h e f o l l o w i n g c a l c u l a - t i o n s . Hence, the v a l u e s of 'Y = V/ND m d of tho e f f i - c i e n c y 'Q = T Y / X a r e b o t h i n c r e a s e d l o $ f o r . t h e p r o p e l - ler i n t e g r a l w i t h t h e Ven tu r i - tube f u s e l a g e .

o r an i n -

I n B i g u r e s 1 2 and 13, t h e r e a r e p l o t t e d t h e r e s u l t s of t o s t s 1, 2 and 3 w i t h p r o p e l l o r s C R 20 and S 5 9 , r e - s p e c t i v e l y , and rrith t h e mod i f i ed V e n t u r i - t u b e f u s e l a f ? e (second series). These c u r v e s show how t h c eff1ci'cnc:i of t h e p r o p e l l e r is i a c r o a s e d bjr t b e 2 r e s e n c e of t h e Vel i tur i - tube f u s e l a g e i n b o t h t 'nese c a s e s .

.

7 . .

N . A . C . A . Technica l iiemorandum' No.. 665, -

.

... . . . . . . . .

The. e f f i c i e n c y o f ' 'the. p r o p e l l e r i n t eg r ' a l ' . W i t h . the . :

f u s e l a g e a l s o i n c l u d e s tile t o t a l r k s i s t a n c e o f . : t h e f u s e - .

l a g e . Moreover, t he above-mentioned lo$ n u s t be:-added. .

.. . . . . F i g h r e s 1.4 ..+rid .1..5. show. t h e e f f e c t 'of Xn'e i n s i d e shape

of:the f u s e l a g e .on t h e c h a r d c t e r i s t i c s o f t h e ' C R.20 and' .

S 59 . p r . o p e l l e r s ' i n t e g r a l wi th t h e . iinmo'difi'ed fu ' s e l age : .

( f i r s t s e r i e s ) . 'The maximum , e f f i c i e n c i e s "are .much i n f e r i - ,or: t.o those o b t a i n e d w i t h t h a mod i f i ed . fu s ' e l age . . .

. ' .:. Iq,:..experirnent NO. 4 , f o r b o t h t h e mod i f i ed and unnod- i f i s d , f . u se l ago , t h o r e s i s t a n c e s a r e P l o t t s d i n ' ; F i g u r e 1 6

(32.8 t o 9 8 , 4 ' \ f t . ) p e r second, U o t o t h e ,great ' r e d u c t i o n : . . i n thq -resistance of t h e modi,fied f u s e l a g e as' comparod ; '.

w i t h t h e r e s i s t a n c e o f t h e unnod. i f iod f u s e l a g e . ' '

f o r . a n . i n c r e n s o i n t h o wind v e l o c i t y f r o m 10 t b ' . 3 0 : m .' . .

. . ID t e . s t . No.:.5.?e o b t a i n t h e r e s i s t a n c e s of t h e same

two. f u s e l a g e s w i t l i . , . a wind v e l o c i t y o f 20. 'mIs a n d ' v a r y i n g .

pr .opeI le r , , r.p..m.' mote he re a 1 s o " t h o j great r e d u c t i o n i n ' '. t h e : r e s i , s t a n c e o f ' t h o modif ied fuse1,age. ( f i g . 1.7). a n d . . t h o d i f f e . r . on t ,course of t h o curve.

; .In:. ' ,order t o make a p . rac t ica l"compar isor i of. . the char- a c t e r i s t i c s of t h e p r o p e l l e r 'C R 20 i n t e g r a l w i t h the . '

Ventu r i - tube f u s e l a g e , i t i s i n t e n d e d t o make t h e .same . .

p r o p e l l e r i n t e g r a l w i t h the model o f t'ne f u s e l a g e o f t h e C R 20 - s e a p l a n e . The fuse l age . .of t h e .C R 20 seap1an.e con- s i s t e d . o f one . c e n t r . a l hull (fig.. 1 8 ) ,' t o which were. at- .

t a c h e d a 2 . l . t h e . o t h b r p , a r t s ( s t r u t s , 1;anding gear , wings, . ' - e t c . ) cove red by t h e p r o p e l l e r . . ' (F ig . 18.)

. . I n . o r d e r t o o b t a i n . the mos t u n f a v o r a b l e c o n d i t i o n s , t h e r e w a s p u r p o s e l y chosen the C 3'20 p u r s u i t s e a p l d n e , t h e f f n e s t o b t a i n a b l e , w h i l e f o r comparison t h e r e w a s 6 8 -

l e c t e d a n o t h e r a i r p l a n e ' o f l e s s f a v o r a b l e c h a r a c t e r i s t i c s . The c h a r a c t e r i s t i c s o f t he p r o p e l l e r .C R . Z O i n t e g r a l witk t h e f u s e l a g e o f t h e seap lane C R 20 ark p l o t $ e d i n . F i g u r e 20. I n t h i s f i g u r e and i n comparison w i t h tho'se. charac- t e r i s t i c s , t h e r e a r e p l o t t e d t h e c u r v e s foa ' . t he ' s a Ide p r o - p e l l e r i n t e g r a l W i . t h t h e Ven tu r i - tube f u s e l a g e .

If, a,? , a l r e a d y m&ti,onea, t h e . 10s c o r r e c t i b n . i s made i n t h e e f f i c i e n c y c u r v e o f , the C . I? . . 20, p r o p e l l e r t n t o g r a l wi th t n e Ven tu r i - tube f u s e l a g e , t h e r e is fo.urid a d e c i s i v e advan tage o f t h e l a t t e r , i n tha t i t s e f f i c i e n c y i s greaA- e r up t o Y L= 0.45. Above t h i s v a l u e o f Y , however, t h e maximum e f f i c i e n c y i s s l i g h t l y l e s s , b u t r ema ins near-

. . . . . . .. . .' . . -.

. .

. .

a N , d . C i A . T e c h n i c a l b4omorepdun.N~. 655 . :

l y c o n s t a n t over a l a r g e . r a n g e o f Y . This a l n a y s . w i t 5 o u t t e 2 i n g account o f t h e i n c r e a s e d r e s i s t a n c e due t o t h e i3- c r e a s e d wind v e l o c i t y n e a r t h e model.

The d i f f i c u l t take-off o f t h e t r a n s a t l a n t i c s e a p l a n e s S 55 f r o m B o l a m a i s remembers3. D i f f i c u l t y i s s.ti11 ex- p e r i e n c e d i n t a k i n g o f f f r o m t h e Libyan Deser t . . The dif- . ' f i c u l t y c a n be g r e a t l y red.uce3 by t h i s ne tkod , becaase . t h e p r o p e l l e r t r a c t i o n or thrust i s g r e a t l y i n c r e a s e d a n d t h e absorbed power r educed at t h e v e l o c i t y of t h e t ake -o f f ,

. In t h i s c o n n e c t i o n i t may a l s o be a f f i r m e d that i t i.s n o t n e c e s s a r y t o r e d u c e t h e r e v o l u t i o n s of t h e v a r i a b l e p i t c h p r o p e l l e r , i f t he p r o p e l l e r i s i n t u b e d , consoquent- l y r e d u c i n g t h a s i z e o f t h e p a r t s and t h e we igh t of t h o eng ine sild i n c r e a s i n g t h e r e l i a b i l i t y o f f u n c t i o n i n g .

I now take t h e l i b e r t y t o make an o b s e r v a t i o n regard- i n g t h e system which y i e l d s t h e c h a r a c t e r i s t i c c u r v e s or' t h e C R 2 0 and S 59 p r o p e l l e r s i n t e g r a l w i t h t h e Ven- t u r i - t u b e f u s e l a g e . This o b s e r v a t i o n regards t h e method by n h i c h t h e v a l u e s o f T = V/ND a r e o b t a i n e d . D i s c o n s t a n t , V i s f i x e d and r e - a a i n s c o n s t a n t d u r i n g t h e whole t e s t . . On t h e o t h e r hand, I? v a r i e s f r o m the n i n - inum t o t h e maximum v a l u e p e r m i t t o ? by t h e wind- tunnel ba l ance .

The Y , thus o b t a i n c d , i s v a l i d f o r . i s o l a t e d p r o - p e l l e r s and f o r p r o p e l l e r s i n t h e s r e s e n c e o f o r i n t e g r a l w i t h a normal f u s e l a g e snopt bp t h e s l i p s t r e a n , because t h e e n t i r e fuse l ago- i s oxposed. t o t be wind v e l o c i t y V i n c r e a s e d by t h e v e l o c i t y of t h o s l i p s t r e a m .

In t h e case o f t h e Ventur i - tubo f u s e l a g e , o n l y t h e i n s i d e i s under t h e above c o n d i t i o n s , w h i l e t h e ou t s i Je i s a lmsys exposed t o a v e l o c i t y V o f t he wfnd, which i s c o n s t a n t and f i x e d f r o m t h e b e g i n n i n g 03 t h e expe r imen t . As i s w e L l known, t h i s v e l o c i t y i n d u c e s on t h e f u s e l a g e a c e r t a i n r e s i s t a n c e o f c o n s t a n t v a l u e f o r t h e d u r a t i o n of t h e experiment ,

F i g u r e 10 shows that t h e e T f e c t i v e thrust due t o t h e f u s e l a g e i n c r e a s e s as t h e r e v o l u t i o n speed o f t h e p r o p e l - l e r i n c r e a s e s . Hence t h e p r o p e l l e r must be g i v e n a su i t - a S l o speed because i t must overcome t h e drag o f the o u t - s i d e p o r t i o n .

. . .

N . A . C . A . Technica l Hemorandurn No . 655 9

But such c o n d i t i o n s do n o t occur i n p r a c t i c e . A 3 a i r p l a n e s ta r t s f r o = a speed of z e r o and i n c r e a s e s gradu- a l l y up t o i t s maximum specd. The p r o p e l l e r r .p .n . a l s o i n c r e a s e s , bu t much moro s lowly t h a n t h e spoed o f t h e a i r - p l a n e , becauso th i s i n c r e a s e i s due s imply t o t h o f a c t that t h e p r o p o l l e r r o t a t i n g at a f i x e d p o i n t b r a k e s the eng ine and p r e v e n t s i t f r o m d e v e l o p i n g i t s f u l l poner . The v a r i a t i o n i n t h e r.p.m. cando t amount t o more than 100 o r p o s s i b l y 150 and i s the re fo re a lmost n e g l i g i b l e .

However, 'Y shou ld be o b t a i n e d by v a r y i n g V and by s l i g h t l y v a r y i n g ( o r even k e e p i n g c o n s t a n t ) t h e p r o p e l l e r r.p.n,, f o r t h e p u r p o s e o f s i m u l a t i n g , i n so far as p o s s i - b l e , t h e a c t u a l o p e r a t i n g c o n d i t i o n s of t h e p r o p e l l e r .

T e s t s were made w i t h t h e p r o p e l l e r i n t e g r a l w i t h t h e Ven tu r i - tube f u s e l a g e , w i t h c o n s t a n t N and v a r i a b l e V. The r e s u l t s a r e shown i n F i g u r e 2 1 ( t h i r d s e r i e s o f exper - i m e n t s ) , as compared w i t h c o r r e s p o n d i n g data . o b t a i n e d by v a r y i n g the r.p,iP. The d i f f e r e n c e i s obv ious and shows t h a t my o b s e r v a t i o n .mas c o r r e c t . N e v e r t h e l e s s , i t no l o n g e r seems p o s d b l e , i n t h e s t u d y of t h e p r e s e n t c r a f t , t o app ly Rena rd ' s l a w o f s i m i l i t u d e , o b t a i n e d by v a r y i n g t h e r.p.m. but i t nust be o b t a i n e d i n s t e a d by v a r y i n g t h e v e l o c i t y o f the a i r c u r r e n t .

I n o r d e r t o de te rmine t h e g r e a t e r e f f i c i o n c y of the p r o p e l l e r i n t e g r a l w i t h the . f u s e l a g e , i t i s w o l l t o con- s i d e r t h e f o l l o w i n g p o i n t s :

1. The expe r imen t s showed t h o r e s i s t a n c e o f t h e Von- t u r i - t u b e f u s e l a g e at d i f f e r e n t wind v e l o c i t i e s and, i n p a r t i c u l a r , a r e s i s t a n c e of 0.7 kg (1.54 l b . ) (second so- r i e s ) ( f i g . 16) n t a v o l o c i t y of 20 m/s (65.5 ft./soc.).

2, From the exporimonts w e de t e rmine t h e th rus t , t h o power abso rbed and t h e e f f i c i e n c y o f each o f t h e t w o s r o - p e l l e r s , t h o C R 20 and the S 5 9 , i n t o g r a l w i t h t h o n o d i - f i e d Vontur i - tube f u s e l a g e . ( F i g s . 1 2 and 13.)

3. T h e ' e f f e c t i v o thrust o f b o t h p r o p e l l e r s i n s a i d c o n d i t i o n i s t h e sum of the r e s u l t a n t t h r u s t , , m e a s u r e d by t h e t u n n e l b a l a n c e , and or' t h o r o s i s t a n c e o f t h e Ven- t u r i t u b e at t h o g ivon wind v e l o c i t y .

This , because i n o r d e r t o o b t a i n a p o s i t i v e p r o p o l - l o r t h rus t , i t must f i r s t overcome t h e r e s i s t a n c e of the

i

2.537 3.375 4,225

.

0.622 0.565 0-.518

NIA;CIAb Teciipical idemorandurn Bo. 655 1 0

Y

Venturi- tube f u s e l a g e . !doreover, i t i s d e s i r a b l e t o keep the r e s i s t a n c e of t h e f u s e l e g e c o n s t a n t at d i f f e r e n t p ro - p e l l e r spceds , because i t s i i l c r easo o r d e c r e a s e i s due t o t h e e f f e c t of t h e r o t a t i o n of t h e ;?repeller and t h e r e f o r e i s t h e e f f e c t of t h e p r o p e l l e r i t s e l f , I n a3 a i r p l n n o we have S = R (S = p r o p e l l e r t h r u s t a d R = a i r p l a n e r e - s i s t z n c e o r d r a g ) .

7

In t h e expe r imen t s i n t e g r a l w i t h t h e Ven tu r i - tube f u s e l a g e , we ob to ined a t h r u s t d i f f e r e n c e between t h e t o - t a l p r o p e l l e r t h r u s t and t h e r e s i s t a n c e of t h e f u s e l a g e , i .e . , P = S - R (P = t h r u s t measured on t h e b a l s i l ~ e ) . Heace t h e t o t a l e f f e c t i v e th'rust of t h e p r o p e l l e r i s S = P -I- R, These c o r r e c t i o n s of t h e t h r u s t and he3ce of t h e e f f i c i e n c y a r e g i v e n i n Tablo V. Apparen t ly , t h e r e i s no v a r i a t i o n i n t h e powor absorbed .

. Prop e 11 e r r.p.n.

3200 3600 4000 4400 4800 5200

P r o p e l l e r r.p.n. I

3000 3400 3800 4200 4600 5000

TA3LE V

0.700 16262 1.937 2,675 3.525 4.512

0.0698 10.067

0.0999 I 0,0717 0.105 0,0719

Oh0945 IO.0699

0.9168 0.8537 0,835

0.721 0.686

0.765

Thrus t on

ba lance kg

0,625 1 ,325 2.150 3 4 037 4,025 5,062

T o t a l t h r u s t

kg 1 . 325 2 . 025 2.850 3.737 4 . 725 5.752

.-_I

IC--

:g x 2.2(

0 ,611 ' 0.0765 01553 0,0840 0.505 0.0869 0.464 / 0 * 0 8 9 7 ---- *--- -_ 1.52 = l b ,

x --_I-_-_-

0.0465 0 . 0524 0 . 0559 0.057 0.0568 0.0577 - -_-_

r,

- - .- -_ 0.952 0.882 0.537 0.8129 0 . 7 7 2 6 0.721 _-_ .

N . A . C . A . Technica l Zdenorandlrm Bo. 655 11

These d a t a , measured i n c u r v e s ani? superposed i n 3 i g - u r e s 12 and 13, a r e e l s o p l o t t e d i n F i g u r e s 22 and 23 , 03

which i s shown t h e i n c r e a s e d e f f i c i e n c y o f t h e p r o p e l l e r i n t e g r a l w i t h t h e Ven tu r i - tube f u s e l a g e (by s u b t r a c t i a g t h e f u s e l a g e r e s i s t a n c e ) , as comcared. w i t h t h e same a l o n e ann i n t h e p r e s e n c e of t he f u s e l a g e . The f u s e l a g e r e s i s t - ance f o r m s p a r t o f t h e t o t a l r e s i s t a n c e ,and hence o f tho t o t , o . l e f f i c i e n c y o f t h e e n t i r e c r a f t . Eo T i l l t h e r e f o r e examine, i n a future a r t i c l e , t h e e x p e r i m e n t a l e f f i c i o n c y r e s u l t s o b t a i n e d w i t h t h e coiaplcte t u r b i n e wing. Other v e r y u s e f u l a p p l i c a t i o n s can bc made of t h c p r i n c i p l e o f t h o t c r ' o i n c wing.

IC t h e r e a r e openings in t h e s i d e s o f t h o Vsn tu r i - t u b e f u s c l a g o ( f i g s . 24 and 25) e n d i n g n e a r t h o na r rowes t s e c t i o n o f t h e t u b e , nhcro t h e n c g a t i v o p r e s s u r e i s t h o g r e a t e s t , a r c v c r s a l o f the a i r f l o w i s o b t a i n o d . If t h i s r c v c r s a l i s fo rward , i t i n c r e a s e s t h o t h r u s t ( f ie ; . 24); i f upwzrd, i t i n c r e a s e s the l i f t . E x p e r i n o n t s w i l l soon be i n s t i t u t e d i n t h i s connec t ion . A t p r e s o n t m e have t h o f o l l o w i n g c o n c l u s i o n s :

1. The e f f i c i e n c y of a p r o p c l l e r i n t h e p roscnce o f a Ven tu r i - tube f u s e l a g e i s g r e a t e r t h a n t h a t o f an i s o - l a t e d p r o p e l l e r ;

2. The e f f i c i e n c y of a p r o s e l l e r i n t e g r a l w i t h a Ten- t u r i - t u b e f u s e l a g e i s g r e a t e r t h a n that of a n i s o l a t e d p r o p e l l e r o r of a p r o p e l l e r i n t h e p r e s e n c e of t h e sLme f u s e l a g e ;

3. The Ventur i - tube f u s e l a g e , Fhen tho ' p r o 7 e l l e r i s runn ing , o f f e r s no r e s i s t a n c e , b u t Froduccs a t h r u s t ( r e - a c t i o n ) , which i n c r e a s e s t h e j3 rope l l e r t n r u s t , as s'r;-onn by F i g u r e 10;

4. The f u n c t i o n i n g o f t ho p r o p e l l o r i s g r e a t l y af- f e c t e d by t h e i n s i d e shape o f t h e Ven tu r i - tube f u s e l a g e .

T r a n s l a t i o n by Dwight K. H i n c r , N a t i o n e l Advisory Committee f o r Aeronau t i c s .

. N.A.C.A. Technical Memorandum No. 655 Figs. 1 ,3

--__ ----_ - _c_ - - - -._ -

_ _ _ _ - _ - _----

e=40.50 a= 37.50 b=l50.00 c= 22.50 d= c?o.oo

f =57.00 g46 .00 h=6 3 . GO i=60.00 j=51.00 lc=l9.00 15.15.00

Fig. 1 Tube having inside shape of venturi tube and outside shape of wing prof i le . Scale 1.5 of the model. Longitudinal section.

-. To the propeller balance -.

Fig. 3

1 3 ~ N.A.C.A. Technical Memorandum No.655 Fig. 5

Propeller integral with Venturi-tube fuselage ------ 11 in presence of 1' I1 11

isolated 11 - 150

140

130 5

120

110

4 100

90 W.m.

3 7f

T .m. (e) 60

2 50

40

30

20

10

0 0

1

2000 3000 4000 5000 Nom. r.p.m.

Fig.5 "Stipa" intubed Tropeller (Series 11) Propeller of seaplane CR 20. Thrilst and power of 2ro9eller rotating at a fixed point.

.P - ... .. . .

N.A.C.A, Technical Memorandum No, 655 Fig. 6 Propeller integral with Venturi-tube fuselage

---a_- I1 in presence of If I1 11

. 5

4

.

1

0 2000 3000 4ooc 5000 N.n.

r .p.m. Fig. 6 "Stipa" intubed propeller (Series 11) Propeller of

seaplane S 59. Thrust and power of 3ropeller rotating at a fixed point.

15; N.A.C.A. Technical Ideaorandm No, 655 -rl. 21g. 7

.

F i g

2000 3000 4mc 5000 N.m. r.p.ol.

I1Stipa1' intubed propeller (Series 11) Propeller of s e a p l h e CR 20. Thrust and power of propeller rotat ing at a fixed point.

;. 7

W.A.C, FJgs. 8,lO-

r.p.n?. Fig. 10 Stipa's experiments (Series 11). Negative resistaace (reaction)

of tube at differellt propeller r.p.m. V=O m/sec.

,

1% E.A.C.A. Tech ica l Menorandurn No. 655

f l To the propellor balance.,

Figs. 9,11

I %-Rear balance

Fig. 9

Fig. 11

18-= U.A.C.A. Technical Idonorandm Bo.655

.18

.16

.14

.12

I-

x .10

.08

.06

. 04

.02

0 0 .1 .2 .3 .4 .5 .6 .7 .a

Y

Figs. 12,13

Fig. 12 S t ipa" intubed

propel1 e r (Series 11) Propcllcr of scaplaao CII X v = 20 n/scc.

tagral

7

x .

.

. 1%

.16

.14

.12

.10

.08 7

x. .06

04

.02

.8

' .?

.4

- 3 r\

.2

.1

0 .1 .2 03 .4 .5 .6 .7 Y

0

Fig . 15 Model S 59 integral with tube D=0.5205 m VZ%O mlsec.

.

. 14,15

2oc N.A.C.A. Techiical iJenorandurn Bo. 655 Fig. 16

. Z l c N.A.C.A. Tech ica l Memorandum No. 655

t

2500

2000

1500

R , g

1000

590

Fig. 17

/

moo 3000 4000 5000 r.p.m.

Fig. 17 Stipa's experiments. Resistance of tube ( in grams) a t different propeller r.p.m. V=ZD rn/sec.

. . . . .. . _. . .- - .~. . . __ -____

. z3

M.A.C.A. Technical Memorandm No. 655 Figs.l8,19

To the propel ler

I

,

./ - - ..- .- F i g . 19

I

N.A. C .A. Techni .16

44

.12

.10

.06

.04

.02

.

.

.20,21

Fuselage CR 20

7 x

Tube ---- - - .__.--_.-__ Tube for co r rec ted voloci ty

Fig. 20 Propeller of seaplane CR 26, integral with fuselage. 014 e 7

.12 .6

.10 .5

.08 .4 rl

.06 .3

.04 .2

.c2 .1

0 Y

--- P r o p l l e r of seaplane CR 20 intograi w i t h tube (V=20 m / s ~ ~ )

11 11 11 n 11 11 11 (N.m.=4600)

. 2 4 ~ N.A.C.A. Technical MeEorandum N0.555

1 I

2 2

020

.18

-16

14 T

x 012

0 10

08

.O6

04

0 02

1.:

1.(

C 0 .

o t

r 0 1

* t v

F * L

. 04

03

02

.1

0

Fig022

a,Integral derived resistance,isolated tube. b,Inpresence. c,Integlal. d,Alone

Fig. 22 "Stipal' intubed propellor (Series 11). Propcllcr of seaplane CB 2ci ( v = ~ c m/sec.)

'.

2 5 ~ N.A.C.A. Technical Memorandm No.655 Fig. 23

.22

.a

.18

.16

.14

1

1

7

x rl

.12

.10

.08

.06

.04

.02

a,Intogral derived resistance,isolated tube. b,In presence c,Integral. d, Alone.

Fig.23 "Stipafl intubed propeller (Series 11) .Propeller of seaplano s 59 (v=~o m/accJ

i

4

N.A.C.A. Technical Uemorandum Eo. 655

Fig. 24

Fig. 25

Figs. 24,25

.