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NATIONALADVISORYCOMMITTEEFOR AERONAUTICS

TECHNICAL MEMORANDUM

No. 1169

DESCRIPTION OF RUSSJANAIRCRAFT ENGINES“AM 35” AND “AM 38”

By H. Denkmeier and K. Gross

Translation“Beschreibung der russischen Flugmotoren “AM 35” und “AM 38”

Deutsche Luftfahrfforschung, Untersuchungen und Mitteilungen Nr. 690Deutsche Versuchsanstalt f. Luftfahrt E. V., Inst. f. Triebwerk-

Gestaltung, Motoren-PruHeld, Berlin-Adlershof .ZWB, Aug. 1, 1942

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WashingtonJune 1947

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NATIONAL ADWSORY COMMITTEE FOR AERONAUTICS

TECHNICAL MEMOWilXJM NO. 11.59

DESCRIPTION OF RUSSIAN AIRCRAE’TENGINES

By H, Denkmeier and K. Gross

Only the following excerpts, which describe the Ruseian developedswirl throttle, have been translated and are presented here.

A. DESCRIPTION OF AM 35 AND AM 38 ENGINES

IV. Construction of Engines

& Supercharger:-- The AM 35 Supercharger aildthe AM 38 super-charger ~-l~%_) are of a .single-sta~ecentrifugal type. Mounted ona 16-blade half-opon impeller is a steel inducer. Adjoining theimpeller is a nonbladcd annulai-casing of lar~e radial dimension towhich the swirl throttle is attached (figs. 21 and 22). The techni-cally most modern part is the swirl throttle (fig. 26) mounted on theinlet to the supercharger;the mechanical construction of this throttleis strikingly simple. Because the swirl throttle has up to the presenttime never been found on other engines, the assumption may be made thatthis throttle is a purely Russian devel.opm~nt. Twelve radial guidevanes carried by journala at the outer ends are simultaneously con-trolled by means of’ toothed segments and a toothed ring. Motion istransmitted by a boost-pressure regulator mouiltedon the side of thesuperchargerhousing to one of’the guide vanes. Placement of thevanes in an oblique position imparts a spiral motion to the air in thedirection of rotation of the superchargerand rcd.ucesthe superchargerdriving power. The smaller amount of’su~ercharger work is accompaniedby a smaller temperature rise in the compre~sor, Because the swirlthrottle also has the functions of a boost-pressuxe regulatingvalve, its effect on the adiabatic pressure head of the superchargeris greatest near sea level lecause of the markedly oblique setting ofthe vanes and decreases with increasing altitude, that is, with theincrease of the angle to which the blades are open.

,..*“Beschreibungder russischen Flugmotoren “AM 35” und “All38.”

Deutsche Luftfahrtforschung,Untersuchungen und Mittellungen Nr. 690.Deutsche Versuchsanstalt f. Luftfahrt E. V., Inst. f. Triebwerk-Gestaltung, Motoren-Pr~ffeld,Berlin-Adlershof, ZWB, AUG. 1, 1942.

2 NACA ~hiNo. 1169

The superchargerwork aa,vedby this method of’throttling is con-aide]:alle;it will le diacuased further in the description of investi-ga.tiona,which follows.

The swirl throttle installed in the AM 35 and the AM 38 allowsvery high supercharger apeeda at aea level and therefore allows theeli?ninationof a gear dift for low al.ti%udes.

. . .

B, TEST RUNS OF AM 35 AiiDAM 38 ENGINE6

II. Test Run of Ali38 Engine

The engine is a purely low-altitude en~ine equipped with a super-charger, the full pressure altitude of which ia 2,2 kilometers. Theinfluence of the swirl thrcttle, which is noticeable only below fullpressure altitude, did not appear very strongly in these teata becauseof the I.OWdesign altitude of the supercharger. This characteristicfirst became fully evident in the operation of the AM 35-A engine,which is equipped with a high-altitude supercharger. [NAcA comment:The statement had preciously been made that “The superchargers of thetwo engines are of exactly the same design except for the gear ratios”jmmely 11.05:1 and 14.6:1.]

. . . The wximum output waa reached at an al.titucleof approxi-mately 2,2 kilometers; from there the output curve passes into thenormally falling branch by way of’an arc, This arc-shaped bend atfull pressuro altitude is caused by tho swirl throttlo. The advantageof the swirl throttle, to which in effect the possibility of elim-inating the sea-level stage of the supercharger is due, becomesapparent in a very conaidorable increase.of output below fuil pres-sure al’~itudeas compared to operation with the normal throttle, Forexample, ii’for the output curve at pL = 1,56 atmospheres absolutoand n = 2150 rpm, the indicated outputs of the engjne ‘withandwithout the swirl throttle are calculated according to

Vi x 714 x GLwith throttleNi with thrcttle = - 632

where vi = 0.32, for indicated output with awi$?lthrottle at

pL = 1.56 atmospheres absolute, tL = ’35°C, and n = 2150 rpm.

0.32 X 714 X 4920‘i with throttle = 632

NACA W No. 1-169 3

*.::

‘i with throttle =~~:, ... .

/J Because the quantities of air ~ith

1780 horsepower

.and without swirl throttle at equal

i,? boost pressure vary in proportj.onto the absolute temperature, fcir’the>‘h:;1 air delivery without swirl throttle at pL & 1.56 atmosphei-esabsolute/.I{f and tL . 116° C the following results are obtained:;/

‘L with throttle% without throttle = TL without ~tiottle % with throttle

368= ~~x”492C = 4650 kilograms per hour...

and therefore

0.32 X 714 X 4650‘i without throttle = 632

. 1680 horsepower

At an altitude of 0, a gain in power of 100 horsepower, which.decreases to O at full pressure altitude (hatched area in fig. 30),is calculated. The same power gaiilis found in actual test. Thereduction of temperature due to the swiri throttle was ‘measuredas21° C. correspmlding to the te-mperatu.rebehavior of the engine, apower’gain of 70 horsepower Is attained. To this gain is added thereduction in power used to drive the supercharger, in accordance with

Gs Cp At X 427Ne.l = 7!5

with swirl throttle

without

1.37 x 0.24 X 80 X 427Ne-l = -——.——..._

75= 149.5 horsepower

swirl throttle

1.29 X 0.24 X 101 X 427Ne-l = — 75—— = 178 horsepower

ANC.l = 28.5 horsepowerm ,,,

AHw ‘%-+” =

0.192

4

AHad—- = 0.405Had totel

NACA ~No. 1169

Thus with a 4@.5-percent reduction of the adiabatfc pressure head asaving in supercharger driving power of 19.2 percent is obtained.

For the 100 horsepower calculated Tower gain, an experimentallyobserved gain of 70 + 28.5 = 98.5 horsepower, that isj 70 horsepower,is gained from the reduction of temperature and about 30 horsepowerfrom the reduction of power input to the supercharger. The decrease inpower gain aa full pressure altitude is approached is caused by theincreased opening angle of the swirl throttle (fig. 30), which is con-trolled by the boost-pressure regulator.

[NACA ccnunent: A further power gain should result from thedecreased supercharger outlet temperature. Decreased mixture temper-ature will result in higher permissible power output with fuel of agiven knock rating.]

. . .

Figme 31 shows the ;;resstli-es behind.the su;?erchargercorres;?o.ndf.ngto the altitude-power grayh, These pressure ct~~es have the same shapeas is usual with.conventional regulati.agvalves. Only at full pressurealtitude is there, due to the nature of the swiri throttle, a curvedtransition instead.of an angle in the curve. T?lepressure loss insupercharger duct and carburetor with fully opened swirl throttlea-mountsto 100 millimeters of mercury.

The temperature reduction caused by the swirl throttle at fullpressure altitude is shown in figure 32. Here the temperature, likethe supercharger-outletpres=ure, remains at the same level until abovefull pressure altitude. The t~~iiilines “Delowan altitude of 3.2 kilo-meters show the curve of boost air temperature that would be attainedwithout the swirl throttle. Cnly at an alti’~uiieof 3.2 kilometersdoes the actual tem’’eraturedifference ‘II - TI reach the va”lues

corresponding to operation with open swii-lthrottle. The inlet-airtemperatures to the su~ercharger correspond to the Ina temperatures.

In figure 33, air consumption is plotted a~ainst altitude. Inspite of the relatively great s.cat;bei”ingof tk:edata points, it maybe seen tha-teach curve is cGnvex dovnwartly mtil full press:~realtitude is ~eached. The parz o~:the c~li-verising agaj.nas fullpressu,realtitude is approached corl”espond.s“ho the usual air-quantitycurves for muliicylinder engiliesjvhich ‘riseat a tiillf~~mrate untilfull pressure altitude is reached. In the same engine, the impzoved

NACA TM No. 1169 5

flow coefficient at low altitudes due to the swirl throttle producesan increase fn air quantity at sea level. Beyond full pressurealtitude, “thec:urv’esfollow a normal course;

*.*

Figure 35 showe the variation of certain engine operatingcharacteristicswith engine speed, which at the usual operating speedsof 1800 to 2200 rpm is very slight. The influence of the swirlthrottle is particularly apparent here in tileboost air temperature.The numbers printed bjside the data -pointsindicate the opening anglesof the swirl throttle, Below n = 1640 rpm, the swirl throttle iswide open because of the low boost pressure and therefoiaehas noeffect. In this region the temperature rises as a function of thespeed in the usual manner, Only with the closing of the swj.rlthrottledoes a break appear in the temperature curve. Thereafter, the observedtemperatures run far below the temperatureswithout swirl throttle,which are shown by the thin line. Breaks are also evident in thepower and specific fuel consumption curves.

111. Test Run of AM 35 Engine

. . . Due to the greater full pressure altitude [NACA comment:6 lan],the effect of the use of the swirl throttle is much greateras compared with the AM 33 engine.

..*

. . . Full pressure altitude is 6 kilometers with an output of1240 horsepower. Equal pi-essuroaltitude is !3.5kilometers with anoutput of 870 horsepower. The power gain produced by the swirlthrottle is made clearly evident by some data pointB obtained withthe throttle disconnected (fig, 40).

ThUS tit an altitude of 2 kilometers, pL = 1.35 atmospheresabsolute, and n . 1750 rpmj a power difference of approximately100 horsepower is obsei-ved. By extending this power line in theusual manner as a straight line towards an altitude of O, at thatpoint with these same opemting data, a power gain of 150 horsepower,which becomes still greater for higher speed and hifjherboost pres-sure, appears. Because of the high boost air temperatures, thesemeasurements could be made only at lower speeds and higher altitudes.In the same figure the respective opening angles of the swirl throttleare shown.

. . .

6 XACA

The respective pressures ahead of the superchargereuperchar&er-outletpressures measured at full throttle

~No. 1169

and theare shown in

figure 41. Here the swirl throttle acts simply as a boost pressureregulator. The pressure loss in the air duct and the carburetoramounts to 100 millimeters of mercury.

The effect of the marked temperature reduction produced by theswirl throttle is most cl.eariyevident in the graph of boost airtemperatures plotted against altitude (fig. 42). At an altitude ofO and n = 2050 rpm, there is a temperature reduction of 43° C. Thesupercharger pressure has no influence on the temperature level.

Figure 43 shows air consumption plotted against altitude. Here,as in the AM 38 engine, the eaddle-shapedform of the curves belowfull pressure altitude may be o%served. The thin lines show air flowin the tests with the swirl throttle disconnected and correspond tothe usual curves with a clack throttle. In these air-consumpt~.oncurves the effect of the swirl throttle is again clearly evident.

The flow coefficient for the same operating condition with andwithout swirl throttle is plotted in figure 44. The air quantitiesfor the flow coefficient without swirl throttle were extrapolated onthe basis of the available data points,

,..

The variation of certain oyerating characteristicswith the speed(fig. 46) is very small between n = 1S00 to 2150 rpm. AtPI,= 1.1 atmospheres absolute, this range extends to 1600 rpm.

Because the high supercharger gear ratio in this engine produces evenat lower engine speeds a high supercharger-outletpressure that kee~sthe swirl th~-ottleconstantly in an almost closed position, there isno visible effect of the swj.rlthrottle in these curves.,as contrastedwith those for the AM 38 engine. The numbers adjoining the datapoints give the opening angles of the swirl throttle.

.*.

In figure 53, the curves of external driving power are plottedagainst altitude. The inputs were observed with the Iiomal operatingcondition of the engine ar.dwith open and closed Gas :h-::~ttle.Theswirl tlmottle operated in the normal uanmer; to this operation mustbe attributed the deviation oi-the curves from the normal coursebelow full pressure altitude because of reduction of superchargerpower input. fitan altitude of H = m kil.cmeters, the curves withopen and with clcs;d gas throttle intersect at the points that corre-spond to the power necessary to overcome friction alone without anywork of gas changing.

.“.

NACATM NO. 1169

Iv. SUMWRY,,, .,, ._.

. .“-Thepre~ence of the swirl throttle permits a gain of100 h&seyower at sea level; operation of the engine below fullpreEsure altitude, which, as stated in thereached at an altitude of 2 kilometers, isthe swirl throttle. . . .

Translation by Edward S. Shafer,National Advisory Committeefor Aeronautics.

Russian manual, isnot possible without

NACA TM No. 1169 Fig. 3

Figure 3. - View of accessories and supercharger of AM 38.

>.

NACA TM No. I 169 Figs. 21,22

-.

Figure 21. - Supercharger. View of swirl throttl e.

.

Figure 22. - Supercharger with impeller.

NACA TM No. I 169 Fig. 26

Figure 26. - Swirl throttle.

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D.

‘, ‘H,6.66 I iters, E, 1:7

g, EO, 20 0 B. T. C.

Es, tj20 A. B.C.

~, tj2° B. B.C.

Aw”200 A. T.C.

ic fuelpt ion, beShp-hrl

1 , , , 1 # A 1. , I , , , , 1 , 1 , I II \ I Ill

00

II ,

0 I 2 5 4 5 6 7 ~ =’ foAltitude, km

zo●

L 1 I 1 ,

/. o .9 .8 .? .6 .5 .4 .3 .2 T

Air density ratio, y/yO -.(n

Figure 30. - Altitude-power graph for AM 38 engine (Russian captured engine, work NO. 65J.●

uo

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rpm. . ,.L,-

2150 ,’” : ‘-’ :mx 1 I- . . . -.

-— v 200(/ ““i “:-

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:n . t- -—- --

— D-” ! ii, ‘“-” “’”- “7 v

r r --l-i- --1 -4 -+4 :-I -w--!-””% : ‘- ~~ - :- -:”” ““--’ - “--4-”-

1 I J I I v~ I II I I u I l-l

I i I I I I I I 1 lUI [ Ix.[ 1’ TI

..>—.— I‘1 I I I—. .,.<. . . .—..1

1 -—. . L L– ..- 1 _.. .-/ “~ ““ - “- ]“-:t-+--j--’

. ..—. -—..- .+_ — --:— -.

:L -,. .._ ___ . —. ..- - --- :.

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1= i. 1

‘i ‘f- i ‘~:~”- - ;.- --”- -- ““ ““’ - “: -% k;--%+> < ;; :’~”~‘“aPre~~ur~ ~I-_ 7-7----4.% -“- ‘-’ “- ‘“ – ““ “:”

..-. — .——. _-. -._..: .-. ..— . .----..—

..:...-

.. .-,

;. . .,:. .: :-

0 2 3 4 5- 6 7 8 9

Altitude, kmI 1

iw 600 5LW 400 ----3k-

Pressure ahead of supercharger, mm H9

Figure 31. - Pressure behind supercharger (Russian captured engine AM 38, work No. 65).

Ml●I I ! I I t 111 \ I [I I Ii’

1 !.[:I I 1 Ill II

Speed, .- I I I irnml

uo

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Q

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an

aL

!/0 1 1 ! 1 , I 1 1 t 1 , , 1 I 1 , I , , , , , ,

Illr ‘ . J- Temperature increase without swirl throttle I I 1 I I I I I 1 ‘‘“’’”’~1

#L

60

50

4030

,-; 201

1- l--

0

/..

20I r I 1 I ! 1 1 1 I I [ 1>

Ill I I I

II I II I I I I I I I I 1 I I I I 1 I I I I I I I

Figure 32. - Temperature behind supercharger (Russian captured engine AM 38; work

No. 65).

I PL

0 / J? 3 4 5 6 78Altitude, km

I

sped,lrpm)

.56 #lm● .—2000

—-1850

n

/0

I

u 9 8 Air den{ity rati&’~ Y/Y..5 .+ .3 .l?

Figure 33. - Ai r flow at various boost pressures and speeds as function of altitude’

(Russian captured engine AM 38, work No. 65).

z

D

-n-.

(nb

—

Fig. 35 NACA TM No. 1169

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m

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L

ala I@E@

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Pressure ahead of valves, p,fa tm *SJ

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I ‘ n \ !i .! .:. , ,.. 1 ! ,

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;. . . .. I ..: ., i ; ‘ ‘I :

1

Engine speed, n, rpm

Figure 35. - Full power, boost air temperature, and specific

fuel consumption as functions of engine speed (Russian

captured engine AM 38, work No. 65). Pressure ahead of

and behind engine, 760 millimeters of mercury; temperatureahead of engine, I 5° c.

I

–1

zTahwff power atPL= 1.69 ●tm sibs.

:*

fw Presau re, pL Speed, nlatm ab~ ) (rpm)

Im 1.1 1.35 1.415● ● ● 2050

I 9001750

m L— !., H5ek+.-

1 P\I IN I

o I i? 3 4 5 6 7 8 9 10 /2

zo8

Altitude, km*1.0 .9 .8 .7 .6 .9 .4L .3

Ai”r density ratio, Y/Y. -.

I Figure 40. - Power outputs and opening angles of swirl throttle with various boost.,

-.

pressures and speeds as functions of altltude [RussianIn

captured engine AM 35-A, work ,I

No- 3853).+Q

!i

‘3Peed . . . ,..:.

i rpm). . . . .—.

)~. ~ox

c

4 ,Q = I 900 _.:_ ___

#I ~ , 1750

m;

.- u— -—..- J- —..-1

.--—

1 [ I I I I I I I I 1 1 w. 1 1 t

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bv -.; \ F

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. . . ..-. — . — ..- .—. —.-. ——- . ..-: . —-—.

al \

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a —. . . . ..— —. . .

Zal“

-+— .- ---- —- . -.—L.

. . . . —.. —-. ..— . . .

1“:...-

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! :

.: :.: :.

. .._ . . . .

~ _7, . . . . . . .

f 3“ :.-

t + - ““(“z- -~ - ““7 “-”- “! “---,- ‘-” f~Altitude,s

Pressure ahead of supercharger, mm Hg

Figure 41. - Pressure behind supercharger as function of altitude (Russian captured

engine AM 35-A, work No. 38531.

km

z

zo,

I

I

Z

z0,

n-.

Figure 42. - Boost air temperature ata

supercharger outlet as function of altitude g

(Russian captured engine AM 35-A, work No. 3653). +N

~ Air delivery at

I ttie-off power

-n-.

u●

Figur

n

I z 3 + 5 6 7 8 9 10 II /2

Altitude, km1 1

to .9 .8 .5- .4 .3AI r“7density rat’?o, Y/Ye,

e 43. - Ai r flow at various boost pressures and speeds as function of altitude(Russian captured engine AM 35-A, work No. 3853).

zot

.7 .6 .5 .4 .35 3 .Z5 .2 .)5

Pressure ratio, pa/p L

Altitude, km

Figure 44. - Flow coefficient as a function of altitude (Russian captured engine AM 35-A,work No. 3853).

I

,

Fig. 46 NACA TM No. 1169

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3

%

L

al

a.Ealw

L

.-

a

C.JL.- ~

u-.- .Uc*Oa .-~w

pressure, p,

Engine speed, n, rpm

Figure 46. - Full power, boost ai r temperatu re, and specificfuel consumption as functions of engine speed [Russian cap-

tured engine AM 35-A, work NO. 3853). pressures ahead of

and behind engine, 760 millimeters of mercury; temperature

ahead of engine, 15° c.

.L

al

mc.->.-Lv

,.. ./ 2 ‘3 ‘4 5 6 78 10 /2 /4 16 ”/8” ‘~

Altitude, KM

e

zo*

/.0 .9 .6 .7 .6 .5 .4 ,3 .2 .1 o

Air density ratio, YIYOn-.

Figure 53. - External driving power as a function of altitude with open and with ciosed, ~gas throttle [Russian captured engine AM 35-A, wrk No. 3853). U

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