On the Aerodynamic Optimization

7/30/2019 On the Aerodynamic Optimization

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AI AA-84-2163On the Aerodynamic Optimizationof Mini-RPV and Small GAAircraftF. R. Goldschmied, Monroeville, PA

A l A A2nd Ap pl ied Aerodyn am ics ConfereAugust 21 -23, 1984/Seattle, Washington

For permiss ionto copy or republish , contact the American Instituteof Aeronautics and A stronautics1633 B roadway, NewYo r k ,NY10019


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ON TH E AERODYNAMIC OPTIMIZATION OF MINI-RPV A ND SMA LL GA AIRCRAFlFoblo R . Goldschmied"Monruevi le, PA 15146

Wing drag, l b

J et total-head @ Sta. 5, lblft '

FWbstract

A brief study has been carried out on the adap-tation of an optimized system comprising an axisym-metri c body, suc tion boundary-layer co ntrol and AH,, Total-head ri s e of fan between S t a .stern je t-pro pul sion, which was developed o ri gi - 2 and 5, l b / f t2

na l l y f o r l igh te r- than- a i r app l ica tion , to mini-RPVand small GA aircraf t by the addi t ion of dynamicwina l i f t . F or mini-RP V. co ns ide ratio n has been n Fan soeed, RP M

H,

Wing l i f t , 7b

,

Free-stream s tat ic pressure, l b / f t2

S tati c base pressure @ S t a . 5, l b l f t '

given to fuselage diameters o f 20 and 34" with agros s weig ht range from 125 t o 300 l b a t the speedso f 100 and 150 Kn. The pr ed ic te d powers rangedfrom 2.35 t o 16.20 HP . P5

For the GA airc raft,co nsi deratio n has been givento fusela ge diameters of 45 and 60" with a grossweight range from 1400 t o 3400 l b a t the speed of200 MPH. The predicted powers ranged from 60.6t o 132.5 HP .

Nomencl a t ur e

A Wing area, f t2AR Aspect ratio

B Wing span, f t

C Wing chord, f t

Wing drag coefficient

Fan pressure-r ise coeff icientAH, 5

4"CH,, = -

o J e t to ta l -head coeff i c ie n t, - PCHT, =

-L q0 Wing l i f t coeff i c ien tCL = qP, - PC P 5 =-

ta t ic base pressure coeff icientq0 @ Sta. 5

Fan suct ion f low coeff icient

Thrust coeff ic ient fo r wingW

TO

CTw =-

o v o ' 6 6

qovo .66Tota l th rus t coeff i c ien tTo = _ _ _

Diameter of ste rn je t and o ffan, f t

d,

D Diameter o f fuselage, f t

qo = w,24T

u = nd,nt

UO

V

NO

Free-stream dynamic pressure, l b / f t 2

Fan suction flow, ft ' lsec

Thrus t of fusel agelboundary-l ayerco ntro l/ je t system, l b

Fan t i p speed, ft/ s ec

Free-stream velo city, ft/sec

J e t v e l o c i t y @ Sta. 5, ft/sec

Fuselage volume, f t3

Gross weight, l b

E l - wouoHP550 Aerodynamic efficiency index

Fan to ta l e ff i c iency

Kinematic v i sc os i ty o f a i r, f t2 / sec

Mass dens i ty o f a i r, l b sec2 / f t4

'IFV

P

$ = A Fan flow parameter5 diu t

Introduct ion

The conc ept o f the optimum aerodynamic in te gr a-tio n of body pres sure -di stributio n (w ith concomitantshape), sl ot- su ctio n boundary-layer co ntrol andstern je t-pro pul si on was presented i n 1967'; a wind-tunnel ver if i ca t ion with a self-propel led tes t modelwas pre se nted i n 1982,' showing 50% power red uc tio nas compared to the be st s treamlined body wi th ste rnwake -pro pel ler. An optimized LTA system was deri vedfrom the above data' and i t was al s o shown tha t je t-propulsion of a subsonic body with free transitionwas achieved wi th j e t total-head equal t o free -stream's.' It can be noted that, for the same massflow, a conventional free -stream j e t propuls or wouldhave a je t total-head coe ff icie nt CHT, = 4 or, forthe same diameter, a co e ff ic ie nt CHT, = 2, as showni n Ref. 5, on the bas is of the bes t conventionalstr ea mlin ed body of equal volume.

The op timiz atio n of streamlined bodies by shape*Consulting Engineer; Associate Fellow A I A A . only was presented i n 1974;6 f or al l- turb ul en t.-/ boundary-layers, l i t t l e drag gain could be obtained@Copyright 1984 by Fabio R. Goldschmied, P.E. by op timiz ing the shape. T his extensive programReleased Io A l A AIo publish in al l orms.


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proved conclusively that boundary-layer controland prop ulsio n had t o be integrated with the bodyshape i f su bs tantia l power gain had to be achieved.

The o b j e c t i ve o f t h i s p ap er i s t o i n v e s t i g a t eheavier- than-air appl icat ions of th i s opt imizedsystem, i .e . to invest igate the in s tal la t io n ofa l i f t i n g wing onto the fuselagefboundary-layerco ntro lf je t propulsio n system. The evaluation w i l lbe ca rrie d out on the bas is o f an aerodynamic e f f i -ciency index 6 = W,U,/HP f o r two c lasses o f a i r-cr af t, i.e. mini-RP V @ 100 and 150 Kn and smallGA (General Avia tion) 2-seat and 4-seat ai rc ra f t0 200 MPH.

Q timize o Body/Boundary-Layer C on trol /J et-P ropb lsi on System: *Tunnel Te-ss_t

The wind-tunnel te s t program o f the 20" diameterse lf-p ropel led model was ca rrie d out i n 1981 i nthe 8x10 low-speed wind tunnel o f the David T aylo rNaval Ship R&D Center; the te s t program was qu it eextensive as i t comprised over 800 t e s t p o i n t sorganized i n 86 tes t runs. The tes t res ul ts arepresented i n Refs. 2, 3 and 4. The basic testmodel wi th open j e t (Conf. 00) i s shown i n F i1 (starboard photo) and i n F i g . 2 (stern photoy:I n F i g . 1 the 12" chord s tru t can be p l a i n l y seenas la rge as a wing would be; i t s interfere ncee f fe c t i s a l re a dy ac counte d f o r i n a l l t he t e s tresul ts . F ioure 2 shows cle ar ly the three radialrakes i n th e j e t nozzle to measure the f l ow andthe j e t to ta l -head.

Fig. 1 S tarboard photo o f wind-tunnel te s t model(Conf. 00)

The ax ia l force (dra g o r thru s t) measurements

were based both on the wake's momentum balance,as in di ca ted by a wake rake, and on the for c eexerted on the s trut, as indi cated by the wind-tunnel balance which was supporting the strut.

A t the higher thru st coeffic ients , above C T =0.010, there was i n a l l cases exc el le nt agreementbetween the two types o f axial force measurements,as shown i n Fi gs. 7, 8 and 9; therefore the thrustdata cannot be dispu ted i n any way.

The model was a ls o tes ted wi th a tail boo m i nthe j e t nozzle (Conf. 01) as shown i n F i g . 3.

:.:.:::. . . . 8:. ./j

F ig. 2 S tern photo o f wind-tunnel te s t model(Conf. 00)

F i g . 3 P ort photo o f wind-tunnel te s t model wi thtai lbo om (Conf. 01)

The la yout o f the tes t model's aftbody wi th thes u c ti o n s l o t , f a n i n s t a l l a t i o n and j e t n oz z l e i s

shown i n F i g . 4. While the fan should have beena t S tati on 5, the arrangement shown had t o be ac-cepted f o r pr ac tic al reasons. The fan mass-flowweighted mean pres sure r i s e i s computed betweenStat ions 2 and 5, wi th the flo w being measured a tS tation 5; the fan a i r power i s determined by theproduct of f lo w and pressure ri s e.

Figure 5 presents a photo of the axial fanin s tal la t io n i n the forebody of the wind-tunnel tes tmodel: the fan discharae i s i n the l e f t foresround,

._..hile the fa n intake i s in dicated by the Foundededge inside the forebody.

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F ig. 4 Aftbody layout with suc t ion-s lo t , f ani n s t a l l a t i o n and j e t n o z z le ( C on f. 00)

Fig . 5 Photo o f f a n i n s t a l l a t i o n i n w i nd -tu nn elte s t model

The typ ica l s tepwise s t a t i c p ressure d i s t r ibu t ionon the body i s shown i n F i g . 6 a t 0' and 6' ang le

of a t tack. The s tepwise di s t r ib ut i on i s used (withsui tab le boundary-layer con trol) t o avoid the largegrowth of the boundary-layer momentum-thicknesswhich nonnal lv occurs i n the adverse Dressuregrad ien t a rea "and t o achieve ve ry low extern al wakedrags, as shown i n Refs. 1 and 2.

While i n Refs . 2, 3 and 4 the wind-tunnel te s tdata were p lo tte d onl y up t o CT = 0.020, since themain focus was on the equ il ib ri um poi nt (CT = O ) ,i n t h i s p a p e r a l l the ava i l ab le t e s t da ta a re p lo t -ted, fo r both fre e t ran s i t io n on the body and fo rt r ans i t ion t r ipped a t 10% leng th .....:...

R = s s x 1 0 6 I... iMSz

L&&-.00 0.7 0.4 0.6 0.8 1.0 12 1.4 1.6-... .8.-L 2.0 2. 2. . . U ..4 2. 6

1.8 1. 0

Dimanrianler~ i d l 0i i ldnce. XI 0

Fig. 6 Experimental s ta t ic-pressure dis t r ib ut i onon te s t model @ 6" angle o f attack

System Analysis

A procedure has been developed fo r the ad di tio nof wings t o the body and fo r the co mputation o f t h eadd i t iona l th rus t acqui red f rom the j e t t o counter-ac t the wino 's draa . The wino 's l i f t ld ra a ra t io shave been coGputed irom classical NACAdata;' b e tt e rres ul ts could be obtained wi th modern ai rf o i l s suchas the Liebeck, the NASA GA (W)-l and -2, e tc. Thefan performance has been based on the tested NASAaxia l roto r /s ta to r s tage 516; the s tage 's designand experimental performance i s given i n Ref. 8.

The experimental wind-tunnel te s t data of R ef.2 have been rep lo tted i n the complete th ru s t rangeand are shown i n Fi gs. 7, 8 , 9 , 11, 12 and 13. Thef a n s e l e c ti o n p l o t i s g iv en i n Fig. 10, with the516 performance curves re la ti n g pressure, fl o w andeff i c i ency.

The computational procedure comprising 15 stepsi s g iven be low:

1. S ele ct the max. cru is e speed U and thecorresponding dynamic pressure qo; determine o restimate the gross weight Wo.

2. S elect fuselage diameter t o yi e ld adequatecabin space and/or equipment volume.

3. Assume l i f t c o e f f i c i e n t CL of wing @ max.cr ui s in g speed. Compute the wing lo ad in g qoCL andthe wing area A = Wo/qoCL. A lift c o e f f i c i e n t C L= 0.40 i s s elected fo r the mini-RPV and CL : .30i s s e l e cte d f o r t h e GA a i r c r a f t .

4. Compute the wing cho rd and span, ass uminga wing aspect-ratio AR = 10 and constant chord:

c = Q B = 1ocActually the wing may have a taper ra t i o and thecomputed chord valu e i s th e niean chord.

5. Compute the wing l i f t /d ra g ra t i o a t theselected CL point , using one of the fol lowing twoexperimental equations from Ref. 7 (Fig. 18, p . 21)f o r wings of aspect ra t i o AR = 10:

a. Cg=O.0068+0.0343 C f (NACA 23018 A i r f o i l )

b. Cg=0.0045+0.0383 C f (NACA 653-418 A i r f o i l )

A par ame tric wing des ign s tudy should be made, i nthe manner of Koegler,' bu t it i s beyond the scopeo f t h i s b r i e f p a p e r.

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6. Compute the drag of the wing:

0.03-

WOFw = cL/cD

I ..* I I I

Transition

since the wing l i f t must equal the gross weightW, Compute the thrust coefficient:

required t o generate the th rus t t o counterbalancethe wing drag. Add 10% to the wing thrus t co eff i -ci en t f o r wing/fuselage interfere nce drag, althoughthe model was tes ted i n the wind-tunnel wi th as tr ut la rge enough t o be a wing; al so add anotherthrust coeff icient increment of 0.003 f o r t h eempennage and ta i l b o ms .

CT, = CTw f 0.10 CTw f 0.003

I n the wind-tunnel tes ts of Ref. 2, an empennageadequate to y ie ld neu t ra l s t a t i c s t ab i l i ty t o thebody up t o 8' had an incremental power coefficiento f o n ly 0.0020.

7. Obtain the value of the fan a i r power coef-f i i e n t :

from the experimental pl o t C HP ~J s CT as presentedi n F i g . 7, c orre sp on di ng t o t h e above CT f o r t hef ree t r ans i t ion o r fo r the t ripped t rans i t ion case,as warranted by the Reynolds number and by opera-t ional considerat ions.

8. Obtain the value of the fan f low coeff i -c ien t :

from the experimental plot CQs vs CT as presentedi n F i g . 8, corresponding t o the above CT f o r t hef ree t r an s i t ion o r fo r the tr ipped t rans i t ion case,as warranted by the Reynolds number and by opera-tio na l cons iderations. Compute the fan flo w 4 =

9. Obtain the value of the fan pressure-rise

cq , x U 0 V Q . 6 6 .

c o e f f i c i e n t :

AnCHli = 2

qo

from the experimental plot C H ~ S s CT as presentedi n F i g . 9, corresponding to the above CT fo r the

f ree t r an s i t io n o r fo r the t r ipped trans i t ion case ,as warranted bv the Revnolds number and bv ooera-tional consid&ations. ~ C ompute th e fan i r e b er i s e AH,,= CH, x q

10. The select ion of the best axial rotor /s tatorstage f o r the jo b requires the computation of thefan system resis tance coeff icient O'/$ i n th e O Ndomain :

- - 2L Y 5

a" @= 3557

L

a

L._Ucrn

0.02k

M I 0 1 *

0 0.01 0.02 0.03 0. M

Thrust Coefficient C T=Tk,Vo'66

Fig . 7 Fan a i r power co ef fi ci en t CHP25 vs Th rustcoeff icient CT

Fig . 8 Fan f low coeff icient CQ5 vs Thrustcoe ff i c i en t CT

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4

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1

Transition

Thrust Coefficient CT = T/qoVa6

F i g . 9 Fan pressure-r ise coeff ic ient CH2s vsT h r u s t c o e f f i c i e n t CT

The denomination of $ i s the f an f low paramete r:

@ =$-

7 d:ut

The denomination of + i s t he f a n t o ta l - p re s s u r eparameter:

The fa n diameter corresponds to the j e t diameterd, ; u t = n d S n i s t h e f an t i p s peed a nd P i s thea i r mass dens i ty. Figure 10 presents the $ 4 p l o twith two fan system res ista nce curves, repre se ntingthe max. and min. encountered i n th i s s tudy, andwi th the experimental performance c urves $4 nd$ - n ~ f the selected NASA ax ia l ro to r / s t a to r s t age518;

i tcan be seen th a t a f a i r l y good match i s

achieved, i . e. the fan w i l l operate between 88.3and 90.6% effic ien cy. Fan aerodynamic se lec tionprocedures are discussed thoroughly i n S ect ion 6o f Ref. 10.

11. The fan speed i s computed:

n =-- q5 a 130.13 RP S$ V O . 3 3

The value of the fan flo w parameter + i s dete rminedi n Fig. 10 from the inte rs ec tio n of the fan systemresis tance curve with the NASA 518 performancecurve . The range of $ i s from 0.485 t o 0.508.S imi la r ly, the f an e ff i c i ency n~ i s de te rmined i nFig. 10 from the NASA 51B efficiency curve at theabove 0 loca t ion .

The fa n diameter i s assumed to correspond to thes te rn j e t d iamete r:

The fan s ha ft power can be computed now fro mth e C H P 2 5 value of Step 7 and the above efficiencydetermination f o r an ava i la ble fan design:

ds = 0.1625D.

12.

p 1.00 ,* i I I I INASA Axial

Y

0.4 -

0 3 -Fan System Resistance

0. 2 -

0.1 -

I I I I

0 0.2 0.3 0.4 0.5 0.6Fan Flw Parameter 0

F ig. 10 Fan pres sure parameter +and totale f f i c i e n c y QF vs fan fl ow parameter $

13. The j e t to ta l -head coeff i c i en t

Hs- PoCHT, = _ _qo

i s determined from the p lo t of F ig . 11 and the j e tv e l o c i t y r a t i o U s / U , i s determined from the p l o to f F ig . 1 2 f o r t he f r e e t r a n s i t i o n o r t h e tr i p p e dtr a n s it io n cases, as warranted by Reynolds numberand opera t i na l con s i dera t i n s .

14. The j e t s t a t i c base p ressure coe ff i c i en t CP,i s de te rmined f rom the p l o t o f Fig. 13. I t can beseen that the s ta t ic base pressure coeff ic ien t rangei s v e ry h i gh ; C P s w i l l be over 0 .8 for the thrustco eff ic i en t range of th is s tudy. As a reference,Ref. 11 shows tha t the base pressure co ef f i c i en to f c o nv en ti on al b o a t t a i l / j e t a f te r b od i e s i s i n th e0.10 t o 0.15 range.

15. The f ina l s tep i s the computation of theaerodynamic efficiency index:

The index expresses the power required to f l y th ea ir c ra ft s gross weight a t the max. crui se speed;therefore , i t i s a good ind ic ati on of the eff i-ci en cy of the aerodynamic des ign when comparingt w o a i r c r a f t a t the same speed.

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Mini R P V

L&,- ' FreeTransiiion Coni.fiake

1 andTransitionTripped B 58% 0

I I I I I0.01 0.02 0.03 0.04 0.05

0.66Thrust Ccefficient CT= T/q V0

Fig . 11 J et total-head co eff i cie nt CHT, v SThrust co eff ic ien t CT

1.8 I I I I 1

0. 2 c -I1 l oI I I I J

0.01 0.02 0 m 0. M 0.0510Thrust Ccefficient CT = TPoVo'66

Fig . 1 2 J e t v e l o c i t y- r a ti o U,/U, v s Thrustcoeff icient CT

1.4, I I I I I

I I I I I0 0.01 0.02 0.03 0.M 0.05

Thrust Ccefliclent C l=T/qoVo'M

Fig . 1 3 J et s ta t i c base pressure coeff icient CP , v sThrust coef f icie nt CT

Mini-RP V aerodynamic design has not achieved ye tan adequate degree of ef fi c ie nc y f o r the missi onspeed and endurance requirements. C ons idering ty p i -cal current vehicles such as the A i r Force/Boeing

A ir c ra f t indus tr ies Scout, the Tadiran Mast iff MK3and the Developmental Sciences Sky Eye, i t i s fo undthat the gross weight ranges from 22 0 t o 380 l b ,the maximum c ru i s i ng speed ranges from 8 5 t o 100

Kn and the engine powers range from 22 t o 30 HP .The aerodynamic efficiency index ranges from 2 . 5t o 3 . 5 .

The wind-tunnel t e s t model,2"'4 wi th i t s dia-meter D = 20.0 in. and 100 Kn speed, may be classi-f i e d a s a ful l -scale mini-RPV; Table 1 presents i t sperformance data f o r 125, 150 and 175 l b g ro ssweights with a suitable wing (CL = 0.40) and empen-nage.

Pave Ti ger, the Atmy/Lockheed Aqu ila, the Is ra el

Table 1 20" Diameter ( V = 6 . 2 f t 3 ) Mini-RPVP 100 Kn (q o = 34.1 PSF)

(Free Transi t ion)

Gross Weight W l b

Wing loading qoCL @ CL= 0.4PSF

Wing area A = Wo/qoCL, f t2

Wing chord, C f t

Wing span, B f t

L if t / dra g ra t io of wing,CL/CD @ CL = 0 . 4 0

CLDrag of wing, Fw = W o / ~

Thrust coeff. f o r wing CTw

Total thru s t coe ff. CTaFan a i r power co eff. CHP,

Fan flow coeff. CQ,

Fan flow 9 CFSFan pressure-risecoeff . C H z sFan pressure-riseAH 2 i PSF

Fan s ystem-resi stance

Fan speed, n RP M

Fan diameter, d , in .

coeff . @ 2 / *

Fan efficiency, '? F %Fan shaft power HP

J et total-head coeff. CHT5

J e t ve l o c i ty r a t i o U,/Uo

J e t s t a t i c bas e

Aerodynamic efficiency F.index

pressure coeff. cp 5

125 I t

13 .6

9 . 1 9

0 .958

9 . 5 8

37.6

3 .32

0.0285

0.034E0 .060

0.0237

13 .50

2 .54

86.36

0 . 7 8 5

33,964

3.25

8 9 . 7 52 . 3 5

2.66

1 . 3 5

1.04

16 .34

~

150 l b

1 3 . 6

11 .03

1.050

10 .50

37.6

3 .99

0.0348

0.04120.0685

0.0252

1 4 . 3 5

2.80

95.20

0 . 8 0 5

35,756

3 .25

90.502 .78

2.90

1 .42

1 .10

17.20

_ _

17 5 l b

13 .6

12 .86

1 .134

11 .34

37.6

4 . 6 5

1.0406

1.04761.0755

1.0264

1 5 . 0 3

3 . 0 5

103.70

0 . 8 11

37,311

3 . 2 5

90 .753 .12

3 .16

1 . 5 1

1 .10

18 .22

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V

With free t ra ns i t i on the fan shaf t powers are3 HP and l e s s a t the 100 Kn speed; the aerodynamice f f ic i e n c y i nd e x i s o v e r 16. The engine may bean ava i la ble Fox Twin, yie ldi ng 3 HP @ 14,500 RP Mand weighing 3 l b wit h mount and muffle r. Table 2 pres ents the performance data o f the same 20 i n .fuselage a t 150 Kn speed with free t ran s i t io n,while Table 2a presents the corresponding data witht r a n s i t i o n t r i p p e d @ 10% length on the fuselage,for gross weights of 150, 175 and 200 l b . I t i sfound th a t the fan sha ft powers are les s than 7HP with f ree t r an s i t io n and l e s s than 8 HP w i t htripped transition; the corresponding aerodynamiceff ic iency index values are over 13 and 10, respec-t i v e l y.

As a di re c t comparison with a curr en t mini-RPVdesign, the fuselage diameter was increa se d t o 34in . to match both the la te ra l dimension and thelen gth of the A i r Force/Boeing Pave Tiger's fuse-lage; Table 3 presents the performance data @ 100Kn with free t ra ns i t i on while T able 3a presentsthe cor responding da ta wi th t r an s i t io n t r ipped @10% length, fo r gross weights o f 225, 250 and 2751 b.

Table 2 20" Diameter ( V = 6.2 ft') Mini-RPV@

150K n

(q o=

77.3 PSF)(Free Trans i t ion)7Wing loading qoCL @ C~=o.4

Wing area A = Wo/qoCL, f t2

Wing span, B

L i f t/ d r a g r a t i o o f w'CL/CO @ CL = 0.40

Wing chord, C =t

CLDrag of wing, Fw = W0/%

Thrust coeff . f o r wing CTw

Tota l th rus t coe ff . CT,

Fan a i r power co eff . CHP,Fan f low coeff . CQ,

Fan flow Q CFS

Fan pressure-r ise

Fan pressure-r iseAH,, PSF

Fan s ystem-resi stance

Fan speed, n RP M

Fan diameter, dS in .

co ef f. CH2 5

coeff . '$2/ $

Fan ef fic ie nc y, 'iF %

Fan s ha ft power HP

J et total-head coeff . CHTs

J e t ve l o c i ty r a t i o U,/Uo

pressure coeff .

Aerodynamic efficiency E

J e t s t a t i c base cp5

4 index

4.87

0.697

6.97

37.6

3.99

0.015:

0.0191

0.039!

0.020;

17.20

1.94

150.0

0.746

44,071

3.2589.05.29

2.06

1.16

0.86

13.00

~

175 l b

30.8

5.68

0.753

7.53

37.6

~

4.65

0.0179

0.0226

0.0432

0.0210

17.89

2.05

158.8

0.763

45,412

3.2589.6

5.74

2.20

1.20

0.89

14.00

_ _203 l b

30.8

6.49

0.805

8.05

37.6

~

5.32

0.0205

0.0255

0.0471

0.0216

18.40

2.16

166.9

0.766

46,617

3.2589.7

6.26

2.30

1.25

0.93

14.69

With free t ra ns i t i on the fan shaf t powers areless than 6 HP w h i l e w i t h t r ip p e d t r a n s i t i o n t h epowers are less than 20 HP ; t h i s may be comparedwi th the 28 HP enaine o f the 250 l b Pave Tiae r.The aerodynamic efficiency index values are over14 and 11, r e spec t ive ly.

F i n a l l y, Table 4 presents the performance dataof the 34 in . diameter fuselage a t 150 Kn withgross weights of 250, 275 and 300 l b a nd w i t ht ri p p e d t r a n s i t i o n . I t can be noted tha t th i s casewi th 300 l b represents a subs tant ia l performanceimprovement over the Pave T ige r, i n both speed (50%gain) and weight (20% gain); the fan sha ft poweri s 16 HP and the aerodynamic ef fi ci en cy inde x i s8.75. It can be noted that, wi th t r ipp ed t rans i-t ion , the re i s no l aminar f low r i s k and tha t theturbulent power coeff ic ients should actual ly belowe r because the R eynolds number i s hi ghe r by thefac to r 1.7 x 1.5 = 2.55.

A schematic la yo ut of the proposed mini-RP V con-f i g u r a t i o n i s shown i n Fig. 14; the pylon/wingarrangement was proposed by Larrabee" f o r gl id e rsso as t o maximize the w ing's l i f t . I t can be notedtha t the pylon/fuselage interferen ce ef fe ct wasalready s imulated i n the wind-tunnel tes ts by the

s tru t. The wing span i s 162 in. and the usefulfuselage length i s 83 in . , whi le the ove ral l fuse-l a g e le n g th i s 127 i n . The empennage i s supportedby a single boom.

S m a l l General Aviat ion Aircraf t

Small GA aircraf t cornwise another cateoorv.~ ..

t o which th is system ana lysis may be appl ied w ithi n t e r e s t i n g r e s u l t s .

Table 2a 20" Diameter ( V = 6.2 ft3) ini-RPV@ 150 Kn (q o = 77.3 PSF)

(Trans i t ion Tr ipped @ 10% Length)

Gross Weight Wo l b

Total thrust coeff . CT,

Fan a i r power co eff. CHPZS

Fan flow coeff. CQ,

Fan flow Q CFSFan pressure-r iseco eff. CHFan pressure-r iseAH *5 PSFFan system- res i stance

Fan speed, n RP M

Fan diameter, d5 in .

coe ff . ' $ 2 / $

Fan efficiency, ' i ~ %

Fan s ha ft power HPJ et total-head coe ff . CHTS

J e t v e l o c i t y r a t i o U,/Uo

pressure coeff.

Aerodynamic efficiency Eindex


_ _150 11

0.019c

0.0500.022;

18.9

2.24

173.1

0.781

49,034

3.25

88.3

6.75

2.28

1.28

0.98

10.40

~

175 I t

0 .022

0.054:0.0227

19.3

2.35

181.6

0.778

49,835

3.25

89.9

7.19

2.40

1.32

1.02

11.19

-200 l b

0.0255

0.0587

0.0234

19.9

2.48

191.7

0.783

50,140

3.25

90.2

7.75

2.50

1.36

1.06

11.84

_ _

7


9/13

Table 3 34" Diak te r ( V = 30.5 f t3) Mini-RPV@ 100 Kn (so = 34.1 PSF)

(Free Transi t ion)

Gross Weight Wo l b

Wing loading qoCL @ C~'0.4PSF

Gross Weight Wo l b

Wing loading qoCL @ C ~=0. 4PSF

250 l b 275 l b

30.8 30.8

Wing area A = Wo/qoCL, f tZWing chord, C f tWing span, B f t

CLDrag of wing, Fw = W o / r l b

Thrust coeff. f o r wing CTwTotal thrust coeff . CT,Fan a i r power coeff. CHP,,Fan flow coeff. C Q sFan flow Q C F SFan pressure-risecoeff. CH25

0

L ift /dr ag ra t i o of wing,CL/CO @ CL = 0.40

6.65 7.31

0.0089 0.00980.0128 0.01380.0390 0.04050.0198 0.0202

48.8 49.81.92 1.98

CLDrag of wing, Fw =

Thrust coeff . f o r wing C TwTotal thrust coeff . CT,Fan a i r power coeff. CHP,,Fan flow coeff. C Q 5Fan flow Q CFSFan pressure-risecoeff . C H s s

Fan pressure-riseAH*, PSF

Fan system-resi stancecoeff. m2/*

Fan pressure-riseAH, PSF

148.4 153.0

0.724 0.731_ _

Fan system-resi stance

Fan speed, n RPMFan diameter, d i n.

Fan shaft power HPJ et total-head coeff . CHT5J e t v e l o c i ty r a t i o U,/UoJ e t s t a t i c base C P Spressure coeff.Aerodynamic e ffi ci en cy Eindex

coeff. $2/*

Fan efficiency, n~ %

-225 l b

13.6

16.51.28412.8437.6

~

5.98

1.01801.02281.04361.021034.952.05

69.9

0.763

:7,9165.52589.104.982.201.200.90

14.0

_ _

!50 I t

13.6

18.41.35613.5637.6

~

6.65

1.02011.02511.046f1.021f35.942.14

72.9

D.773

8,3545.52589.405.292.301.240.92

14.6

_ _175 l b

13.6

20.21.42114.2137.6

~

7.31

'LO2211.02738.0495'.022036.602.23

76.0

3.770

8.6195.52539.605.652.381.260.95

15.1

Table 3a 34" Diameter ( V = 30.5 ft') Mini-RPVP 100 Kn (qo = 34.1 PSF)(Trans i t ion Tripped @ 10% Le ngth)

Gross Weight Wo l b

Total thrust coeff . CTOFan a i r power coeff. CHP,Fan flow coeff. CQ,Fan flow Q CFSFan pressure-risecoeff . CH,,Fan pressure-riseA H 2 5 PSFFan system-resistance

Fan speed, n RP MFan diameter, d5 i n .

Fan shaft power HPJ e t total- hea d coeff. CHT,J e t v e l o c i ty r a t i o U,/UoJ e t s t a t i c base CP 5pressure coeff.Aerodynamic efficiency Eindex

coeff . m2/+

Fan eff iciency, n~ %

~

275 l b

0.02730.06120.023739.432.54

86.6

0.785

20,0185.52589.86.902.561.381.08

12.26

~

Table 4 34" Diameter ( V = 30.5 ft') Mini-RPV@ 15 0 Kn (so = 77.3 PSF)

(Trans i t ion T ripped @ 10% L ength)

Wing area A = Wo/qoCL, f t ZWing chord, C f tWing span, B f tL i f t /d rag ra t io o f wing,CL/CD @ CL = 0.40

Fan speed, n RPMFan diameter, d i n .

Fan shaft power HPJ et total-head coe ff. CHTsJ e t v e l o c i ty r a t i o U &J e t s t a t i c b as e C P5pressure coeff.Aerodynamic efficiency Eindex

Fan efficiency, QF %

25,8625.52588.415.001.901.150.87

7.72

'

26,2765.52588.615.701.961.160.89

8.19

-I00 l b_ _

0.8

9.740.9869.8637.6

7.98

1.01061.01461.04161.020550.52.02

156.3

0.738

5,5575.52588.816.202.001.180.90

8 . 7 5

Table 5 l i s ts the pert ine nt parameters of threecurrent 2-seat personal GA aircraft by Beech,Cessna and P iper; the gross weight i s nearly thesame (1670 to 1675 lb ) and so i s the speed (121t o 127 MPH) and the engine power (108 t o 115 HP).The aerodynamic e ff i c ienc y index i s i n the v ic in i tyof 5.0.

The fuselage diameter i s selected a t 45 in. soas t o accommodate two tandem se ats; the ca bi narrangement layo ut i s shown i n F ig. 15. It hasbeen observed t h a t minimum ca bin he ig ht i s 42 in.and th e minimum seat spacing dimension i s 36 i n.

The speed has been sel ec ted t o be 200 MP Hinstead of 125 MPH because it represents presentGA speed fo r small personal ai rc ra ft. Table 6 pre-sents the performance data for gross weights of1400, 1675 and 1800 l b with trip ped tr an s iti on .It can be seen tha t the fan s ha ft power i s l e s sthan 72 HP and the aerodynamic ef fi c ie nc y indexi s over 12.0. This performance yields a 60% speedimprovement, a 33% power gain and a 7.5% grossweight enhancement. l h e schematic la yo ut o f th i s2-seat GA configurat ion i s shown i n F ig. 16, witha mid-wing arrangement with 0.45 tape r r a ti o and277 in . o ve ra ll span. The useful fuselage le ngthi s 110 in . while the overal l fuselage length i s130 in . The empennage i s sup ported by a twi n boomand i t comorises twin rudders. -

8


10/13

0.272

5.04

n6.7'

0.322

5.05

U

F i g . 14 Schematic la yo ut of mini-RP Y co nfi gu ra tio n

Table 5 2-Seat E4 A i r c r a f t @ 120 MPH(qo = 37.0 PSF)

Empty weight W l b

Gross weight Wo I b

Wing area A ft'

Wing loading W/A PSF

Wing span B ft

Length 2 ft

Engine power HP

Uo MPHax. cruise

speed

CLWing l i f tcoeff .

Aerodynamice f f i c i e n c y Eindex

_ _ _Beech

77,kipper

1,103

1,675

30.0

13012.88

24.0

115121

0.341

_ _

4.70

Cessna P ipe r152 IPA-38-112

ierobat Tomahawk 2

124.7

24.1 23.1

122 1 127

Note: The above data were de rive d from AviationWeek & Space Technology, March 12, 1984, p. 144.

L >

I48" I

4-Seat Cabin Arrangement - 60" Oia. Fuselage

- 110" L

2-Seat Cabin Arrangement - 45" Dia. Fuselage

F i g . 15 Cabin arrangement layo ut fo r GA a i r c r a f t

Table 6 45" Diameter ( V = 70.6 ft3) 4 A i r c r a f t@ 200 MPH (q o = 104 PSF)

(Trans i t ion Tr ipped @ 10% Length)

Gross Weight Wo l b

Wing loading qoCL @ C ~=0.3PSF

Wing area A = Wo/qoCL, f t2Mean wing chord, C f tWing span, B f t

Li f t /d rag ra t io of wing,

Drag o f wing, Fw = Wo/rlb

Thrust coeff. for wing CTwTota l th rus t coe ff . CToFan a i r power coeff. CHP,Fan flow coeff. CQ,Fan flow Q CFSFan pressure-r ise

Fan pressure-riseAH,, PSFFan system-resistance

Fan speed, n RPMFan diameter, d 5 in .

Fan s ha ft power HPJ et total-head co eff . CHTsJ e t v e l o c i ty r a t i o U,/Uo

pressure coeff .

CL/CO @ CL i .30

CL0

coef f . C"* 5

coeff . mn

Fan e ff i c i ency, ' 1 ~ %


Aerodynamic efficiency Ei n d e x

-1400 1 b

31.2

44.82.1121.1

38.3

_ _

36.5

0.02060.02560.05880.0234117.12.45

254.8

0.793

25,7777.3190.160.62.51.370.92

12.1

-

675 1 I31.2

53.72.3123.1

38.3

-

43.7

1.024;1.030:1.06511.0241122.12.66

276.6

0.794

!6,82!7.319 0 . 268.6

2.661.411.10

13.0

-800 1 b

31.2

57.72.4024.0

38.3

-

47.0

1.02651.03211.06851.0248124.12.74

284.9

0.796

17,2117.3190.371.62.741.441.11

13.3

9


11/13

Table 7 l i s ts th'e pert inent parameters of f ivecurrent 4-seat GA a i rc ra f t by Maule, Mooney, P iper,Cessna and Beech, wi th speed from 196 t o 201 MPH,gross weights from 2500 t o 3400 l b and enginepowers from 200 to 285 HP. The aerodynamic e f f i -ci enc y index ranges from 6.5 t o 7.9.

The cabin dimensions fo r four s eats are typi -c al ly 43 in . width, 48 in . height and 92 in .length; a fuselage diameter of 60 in. has beenselected and the cabin layout arrangement i s shown

i n Fig. 15. Table 8 pres ents the performance data f o r gross

weig hts of 2500, 2900 and 3400 l b a t 200 MP H witht r ipped t rans i t ion . I t i s seen that f o r the lowestweight the fan s haf t power i s 110, fo r a ga in o f47%; f o r the middle weight the fa n power i s 120HP , f o r a g ai n o f 40%, while for the top weightthe fan power i s 13 2 HP, f o r a gain o f 53%.

Length ft

Engine power HP

M a x ' cruise U MP Hspeed

Wing l i f tcoeff.

Aerodynamice f f i c i e n c y Eindex

CLr - r f l Schematic-Seat GA Aircraftayout1 Confiouration

24.4 24.7 27.3 28.6 26.7

210.0 200.0 200.0 235.0 285.0

196.0 201.0 198.0 199.0 198.0

0.157 0.148 0.167 0.172 0.184

6.49 7.47 7.90 7.22 6.501675 6 Gross Weight68 HP (Tripped Trans. I

F ig. 16 Schematic lay out of 2-seat GA a i r c r a f tconfiguration

Ta ble 7 4-Seat 6R A i r c r a f t @ 200 MPH(so = 104 PSF)

_ _2125

340033.5

181.0

18.8

Gross Weight W l b

Wing loading qoCL @ C ~ = 0 . 3PSF

Wing area A = Wo/qoCL, f t2Mean wing chord, C f tWing span, 8 f tL if t /d ra g r a t i o o f wing,CL/CO @ CL = 0.30

Drag of wing, Fw = Wo/-lb

Thrust coeff . f o r wing CTwTotal thrus t coeff . C TOFan a i r power coeff . CHP,,Fan flow coeff. CQ,Fan flow Q CFSFan pressure-ri secoeff . CH..

CLCD

L D

Fan pressure-riseAH". PSF

/

On the Aerodynamic Optimization

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