9 ,111~1~~AQ

NATIONAL ADVISORY COMMITTEE “FOR AERONAUTICS

TECHNICAL NOTE

No. 1612

EFFECT OF REDUCING VALVE OVERLAP ON ENGINE AND

COMPOUND-POWER-PLANT PERFORWCE

By David S.” Boman and Samuel J. Kaufman

Flight Propulsion Research LaboratoryCleveland, Ohio

W~hingtonJune 1948

https://ntrs.nasa.gov/search.jsp?R=19930082276 2020-03-16T04:58:21+00:00Z

NATIONAL ADVISORYCO~ FQRAERONAUTICS

~~&L Nm No ● 1612

.—

IzlmEoTcm REmKzmG VALXE ovE.RLAlON ENGINE AND

COMFOUND-POWER-PLANT IEKF-OE

By IkLvid S. Boman and Smmel J. Khufman

SUMMARY

An e~erhmntal investi~tion of a 620-valve-overlap, 18-cylfnder,air-cooled, ?xIial engine mtiied tith 400-valve-overlap cams wasmade to detemdne the effect of a change in valve overlap m engineperformance.

With these data and data on the unmodified 620-valve-overlapengime as a basis, cxxnputations were made to show the effect ofchange in valve overlap on compound-engine perfcwmance.

At rated power, the reduction in valve overlap investigated. caused a reduction of 6 percent in net thrust horsepower ad a reduc-

tion of 2 percent in net specific fuel consumption of the compoundengine at the engine exhaust pressure for max5mmInet power.

.

.,INTRODUCTION

me effect C& exhaust pressure on engine performmce has beeninvesti~ted au two models of a standard 18-cylinder, air-cooled,nxlial atictit en@ne, one having 40° valve overlap and the other62° valve overlap and increased cooling-fin area. The results &these investigation are reported in references 1 and 2. The per-formance of compound power plants using these engines was ccunputed.and the results reported In references 3 and 4. These power plantsconsisted of a turbti and auxiliary supercharger mouuted on acomon sh#t and geared to the engine crankshaft.

The results of the investigation reported in r=erenoe 4 showedthat the ccmpound power plant using the engine af reference 1 pro-vided more power at a lwer net brake speoific fuel consumption atcruise conditions (lean fuel-air rat tos ) than the cazpund powerplant ushg the engine of reference 2. The better performance C&the cmpound power plant using the engine of reference 1 was attri-buted to its lower valve overlap (40°) as compared with the engtie

2

of referenoe 2, which had a valve overlap cd’ 620.overlap engine had bet t er cooling characteristicsPower ratiw, however. than the 400-valve-overlap

WA TN No. 1612

The 620-valve-and a higherengine. The better

cooling cxacteristics of the 620-valve-overlap engine were theresult & the redesign d the cylinder fins and the larger valveoverlap. b = attempt to combine the best features of both engines,the cams from the 400-valve-overlap engine were installed in the62°-valve.overlap engine.

The results d’ an experimental investigation of the performanceof the 620-valve-overlap engine fitted with 400-valve-overlap camsme reported herein. Curves that show the effect of engine exhaustpressure on engine pawer, charge-air flow, volumetric efficiency,and etiaust-gas temperature an-included.” Curves for the 40°- and620-valve-overlap engines are also presented to compare the perform-ance of the three engines and to ccmpare the calculated performanceof the ccmpound power plants.

AHmA!rus

This investigation was conducted using the R-2800 (C series)28-cylinder air-cooled radial engine of reference 2 (designatedengine 2) equipped with the 400-valve-overlap cams from the R-2800 “

,

(A series) engine of reference 1 (designated engine 1). This modi-fied engine is designated engine 3. Except for the installation ofthe 400-valve-overlap cams this setup was e=ctly the same as that

.

reported in reference 2.

Some of’ the pertinent specifications for the three enginesdiscussed herein are:

Engine 1(A series)(refer-ence 1)

Compression ratio 6.65Blfier gear ratio 7.6:1Impeller diameter, in. 11I?ropeller reduction-gear ratio 0.50:1Spark advance, deg B.T.C. 25Valve overlap, deg 40Valve timing, deg.

Intake opens, B.T.C. 20Intake closes, A.B.C. 76Exhaust opens; B.B.C. 76Exhaust closes, A.T.C;, 20

Engine 2(C series)(refer-ence 2)

6.757.29:1

11.50.”45:1

2062

36607026

Engine 3(modifiedC series)

6.757.29:1

11.50.45:1”

2040

20767620

.

NACAT19HO. 1612 3

mom

Procedure

II’or all the conditions of the “irivesti+jation of the 620-valve-overlap engtie modified with 400-valve-overlap cams (engine 3), theprime variable was engtie exhaust pressbre. At each set of engineoperating conditions, the exhaust pressure was varied from about8 inches of mercury absolute to about 20 tnches of mercury aboveinlet-manifold pressure. A list of operating conditions is pre-sented in the following table:

I?uel-air 10.063]’ 0.069 I 0.085 I o ● 100ratio

Enginespeed

(Kl?fd1600180020002200240026002800

~o40404040

----

Inlet-mamlfold pressure(in. Hg absolute)

30> 34, 40, 45 40 --------------40 40 4040 40 4040 2-5,30, 40, 50 4040 40 4040 40 30, 40, 45, 50

-------------- 40 --------------

Ckqarison of Puwer Plants

The three engines discussed herein are compared tith each otheron a basis of the performance of the engine alone and of the perform-ance of compound power plants using these engines. The engine datafor en@ne 3 (modified engine) are compared with the engine @tafrom references land 2 (engines land 2, respectively). . .

The compound power plants using these three engines were com-pared ona net-thrust-horsepower basis in order to include theeffects of cool- drag and other factors affecting power-plantperformance. The net thrust horsepower ficludes the engine pro-peller thrust horsepower (including the power of the turbine), thee-ust Jet thrust, the cool--air drag (or thrust), and the dz’s&of picking up the charge air. Thus:

nthp = VP[ 1ehp + qg (thp - ashp) + jhp - chp

4

where

ashp

chp

ehp

*P

nthp

thp

Tg

~p

auxiliary-stage

NACATN No. 1612

supercharger horsepxer, power required tocompress charge air from altitude tem~erature a~d pressureto carburetor top-deck pressure with duct loss allowanceusing an efficiency of 80 percent

cooling-alr drag horsepower based on momentumchange of cool-ing air across engine cowl and assmdng average cylinder-head temperature of 450° 1?

reciprocating-engine horsepower Includimg power of engine-stage supercharger

exhaust jet thrust horsepower ~cluding charge-air pickuphorsepower

net thrust horsepower

turbine horsepower, power obtained. from expanding engineeXhaust gas from engine exhaust pressure and temperature

to altitude pressure through turbine with adiabatic eff Lciency of 80 percent

gear efficiency, assumed to be 95 ~rcent

propeller eft’iciency, assumed to be 85 percent

No drag powers associated with intercooler and oi 1- coolercooling-air flows are included in the net power because calcula-

tions showed them to be negligible. The net thrust specific fuelconswaption was calculated by dividing the fuel flow by the netthrust horsepower.

IOMUUl?SANDDISO~SION

Basic Data for Engine 3 (MXiified Engine)

The experimental data and computations are presented in amanner similar to that of references 1 and 2.

The effect of varying the ratio of engine exhaust yressure toinlet-manifold pressure pe/~ on brake horsepower, charge-air

.

.

.

NAOA TN No* 1612 5.

. flow, volumetric efficiency, ratio d indicated mean effective pres-sure to inlet-manifold pressure +, mixture temperature minuscarburetor-air temperature Tm - Tc, and etiaust-gas temperaturefor modified engine 3 is shown in figures 1 to 6, respectively. Thevariation of the ratio of inlet-manifold pressure to full-openthrottle carburetor-inlet Treasure ~/pc with engtie speed iSshown in figure 7 for a carburetor-air temperature of 550° R.

References 1 and 2 showed that # and volumetric efficiency~en plotted against pe/~ are independent of inlet-manifoldpressure. Therefore, most of the investigation conducted onengine 3 was at one inlet-manifold pressure. As shown in figures 3and 4, this correlation was substantiated by a small amount of dataobtained at other inlet-manifold pressures.

Comparison of Basic Data for Three Engines

Erake horsepower. - Comparison curves showing the effect ofPe/~ ~d e~~e spe~ on brake horsePower for the @ee e=~esat an inlet-manifold pressure of 40 inches of mercury absolute anda fuel-air ratio of 0.085 are presented in figure 8. Engine 3 pro-vides slightly less pawer than engine 1 over the entire range ofPe/I?m regardless of the engine speed for the condition shown.Engine 3 also provides less power than engine 2 at the lower valuesof pe/~ but protides more pwer than engine 2 above values of

3?e/Pm of about 1.1. As the engine speed is increased from 1600 to2400 -, the differences in engine power between engines 3 and 2at the low values of pe/~ decrease but the differences at thehigh values of pe/~ increase. For other inlet-manifold pres-sures and fuel-air ratios, the trends of power with pe/~ are thesame as shown in figure 8.

Charge-air flow and vohnnetric efficiency. - The =riation ofcharge-air flow and volumetric efficiency with pe/~ and enginespeed for the three engines is shown in figures 9 and 10, respec-”tively. The curves in these two figures follow the same trends asthe brake-horsepower curves of figure 8. The UnUSUSllYkgeincrease in charge-air flow tith decreasing Pe/~ at low ~ee~ana below a value of pe/pm of 0.5 for engine 1 did not occurwith engine 3 in spite of the fact that both engines have the samevalve overlap:

.,.

.

6 RACA TN ~0 . 1612.

Indicated power. - The Umensicmlesa quantity + (ratio ofengine indicated mean effective pressure to engine inlet-manifoldpressure ) is used as a measure of indicated power for any givenengtie speed and inlet-manifold temperature (ref erence 5 ). Thevariation of ~ with =pe/~ and engine speed is shown in figure 11.The curves in this figure indicate the same trends as the curves ofbrake horsepower in figure 8.

IXhaust-@s temperature. - The effect of pe/~ and enginespeed on exhaust-gas temperature for the three engines at-an inlet-manlfold pressure of 40 inches of mercury absolute and a fuel-airratio of 0.085 is shown in figure 12. The eibaust-gas temperaturefor engine 3 averages about 100° F lower than that for engine 2 and500 F higher than that for engine 1 for the entire range of pe/pmat an engine speed & 2400 rpn. At lower engine speeds, the etiust-gas temperatures of the three engines maintain the same relative

positions as at the engine speed of 2400 rp except at high valuesof pe/pm where the temperatures d engines 1 ant-3 coincide.

Comparison of Cmpound-Power-Plant

Performance at Three Engines

The calculated performance of compound power plants using thethree engines is shown in figure 13 where the net thrust horsepowerand the net thrust specific fuel consumption are plot ted againstPe/~ for a flight VelOCi%y of 400 miles per hour and an altitudeof 30,000 feet. Figure X5(a) presents the performance of the threepower plmts at an engine speed & 2200 rp, a fuel-air mtio of0.063, and an inlet-manifold pressure of 40 inches of mercury abso-lute, appro~tely cruise conditions. At this power level, engine 1gives a maxinnm value of 1468 thrust horsepower at a net thrustspecff ic fuel consumption of O.392; engtie 2 gives a maxtium valueof 1420 thrust horsepower at a net thrust specific fuel conwmptionof O.425; and engine 3 gives a maximumvalue of 1330 thrust horse-power at a net thrust specific fuel consumption of 0.408.

Based on these values for the cruise condition, the compoundpuwer plant using engime 3 gives about 9 percent less thrust horse-power at about- 4 percent higher net thrust specifio fuel consumptionthan that using engine 1 and about 6 percent less net thrust horse-power at about–4 percent lower net thrust specific fuel consumptionthan the compound power plant ushg engine 2.

.

.

HACATN No. 1612 7

At approximately rated power (engine speed, 260Q rpm; fuel-airratio, 0.085 ; and inlet-manifold pressme, 50 in. Hg absolute,fig. 13(b)), the cruise-power trends of figure 13(a) are consider-ably changed. As shown in figure X3(b), the compound power plantusing engine 3 gives about 2 yercent more net thrust horsepower atabout 5 percent lower net thrust spec~ic fuel consumption thanthat using engine 1 and about 6 percent less net thrust horsepowerat about 2 percent lower net thrust s~ecific fuel consumption thanthe compomd power plant using engine 2 at the values of pe/~for maximumpuwer.

A breakdown of the components that make up the net thrust:~l~gower is shown in the following table for a value of pe/Qm

:

Engine Turbine Auxiliary Jet cooling- ‘Net Net thrustpower puwer super- power air drag thrust specific

Engine (hp) (hp) charger (hp) (hp) power fuel con-(hp) Sumpticxl

np) (lb~p-hr)

Cruise power. 1 1306 578 143 32 * 51 1442 0.388

2 1095 595 143, 33 -22 1350 .4113 1100 545 1.35 30 -7 1303 .403

. Rated mower1 1819 954 224 55 206 1984 0.5372 1638 1034 230 60 -12 2113 .5073 1700 915 218 53 26 2035 .499

The table shows that changing the 620-valve-overlap cams ofengine 2 to 40° (engine 3) increased the engine power and cooling-air drag power and decreased the tmbine power, auxiliary super-charger power and Jet power for both cruise- and qted-power condi-tions. The decrease in turbine power was the greatest componentpower change and resulted in the lower net thrust pawer of compoundengine 3 as compared with that of compound engine 2. The netthz-ust power of compound engine 1 was greater than that of eitheren@ne 2 or 3 at cruise condition because of the higher enginepower. At the rated-power condition, the thrust power of oompoundengine 1 was lower than that of either engine 2 or 3 in spite ofthe higher engine power because M the “greater cooling-air drag.

SUMMARY OF RXH%HIS

8 NAM TN No. 1612

A comparison d performance and calculated data obtained fromthree 18-cylinder, air-cooled, radial engines - engine 1 (400 valveoverla~), engine 2 (62° valve overlap with increased cooling-finarea) and engine 3 (engine 2 modified with 400-valve-overlap cam),showed that:

1. ~ine 3 Provided slightly less brake horse~ower than enginelover the entire range of the ratio of engine exhaust to inlet-manifold pressure Pe/ti* At low values of’ pe/pm, engine 3 pro-vided less brake horsepower than engine 2; however, at higher valuesd Pe/Pm> engine 3 provided more power than engine 2.

2. Charge-air flow, volumetric efficiency, and the ratio ofindicated mesm effective pressure to inlet-manifold pressure 4,showed the same trend tith pe/pm as brake horsepower.

3. At cruise power, the capound power plant usbg engine 3gave about 9 ~ercent less thrust horsepower at about 4 percenthigher net thrust speoific fuel consumption than that using engine 1and about 6 percent less net thrust horsepower at about 4 percentlower net thrust specific fuel consumption than the compound puwerplant using engine 2 at the values of pe/pm for maximun pawer.

4. At rated power, the compound powew plant using engine 3gave about 2 percent-more net thrust horsepower at about 5 percentlower net thrust specific fuel consumption than that using engine 1and about 6 percent less net thrust horsepower at about 2 petientlower net thrust specific fuel consumption than the compound powerplant using en@ne 2 at the values of pe/pm for maximumpower.

.

.

.

Flight X3?opulsion Research Laboratory,.National Adtisory Conmittee for Aeronautics,

Clevehnd, Ohio, January 20, 1948.

IUUA!r5 Ho. 163.2 9

1. ~, Ih4vids., Eagey, Tikir F., d DO*S ~a I).: Effeotof Edlw#3t Eressum mLthe Perfcmuanoe of m 184yMnder Air-cOd.9a IMidl - Vith a Vd.v-eOverlap of 4P. EACA mEo. 122C, M47 ●

5. P3xi&3_, Be@am& Effeot of~t Baok Pl%ssm cxn-Pm?eo?. K?AcACB no. 3F17, 1843.

,-

10 NACA TN No. 1612

1400

1200

1000

800

600

s 8(a) Fuel-air ratio, 0.0@3; Inlet=ac1 manifold wessure, 40 lnohes

mercury absolute.-1600

1400

1200

1000

800

6

8 , ,1,,,,,,,, 18

Engine s eed1600 I 1 I I I I 7(rpm

I I I I o lF”” +A I + M

Uuv g

I I-BoO!2000

L400 (YIA17W I: 2200A “400

ma 1---w , I

. .800

1200 ~ -+ \ .-+,

+\

10C00 \ \. 1 xl u t I

Y ;\ Y

+.

ax - \

a

600(o) Fuel-alr ratio, 0.0S5; lnlet-

manlfold pressure, 40 lnohesmeroury abaolute.

1600“‘J%%-’”

1400\ E= *

Y \ %

. ,(

1200 \ *

\,

10W\

4-\ ~

‘+ ‘x\

em \

J,l, ,,1,1,,! ,,1?11,1 11111,1,,,,I Ill,I,11,,0 .4 .8 . .

Pe/Pm(b) Fuel-alr ratio, 0.069; inlet- (d) Fuel-alr ratio, 0.100; lnLet-

manlfold pressure, 40 inches manifold pressure, 40 Inohenmermry absolute. meroury absolute.

Figure 1. - Variation of brake horaepover with pe/~. Brake horsepower oorrected co oonatant“carburetor-airtemperatureof 55@’ R. Engine 3, 40° valve overlap.

, .

z

Pe&b

(e) Engine speed, 1600 rpm; fuel- (f) Engine ~peed, 2200 rpm; fuel-ati ratio, 0.069. air ratio, O.O@b.

Figure 1. - Continued. Variation of brake horsepower with Pe/%. -tie ~ge-r c~rre~t*

ta constant oarburetar-air Wnperatv.re of 550° R. Engine 3, 40° valve overlap.

—

2000

lmo

1800

1400

1200

Mao

w

6CQ

400

0 .4 ..9 1.2 1.6 2.o

Pe/~

‘g) fi%:%r’:t%,%ww

Figure 1. . Concluded. Variation of brake horsepower with p~pm.

ta constant oarburator.dr ~~ratwO, Of 56o0 R. ~Ine 3,

.

Brakn hnrsepowur correoted

40° ml we overlap.

%99

.

e,Ooo

6,0M

10,CQO

& (a) Fuel-ati ratio, 0.063; ldet-

~ manifold premure, 40 Inoiwmemury absolute.

; L2,0CX30

c

3Y 10,OOO

&

1!8,0MJ

6,000

4,000

(b) Fuel-air ratio, 0.069; lnlet-Mnifold pr@ssure, 40 inohesmeroury abaolute.

Figure 2. - Variation of oharge-air flow with

U,wo

10,000

e,OCQ

6,00’3

$ (o) Fuel-air ratio, 0.025; lnlet-~ manifold pres sur?, 40 Inohes

merenry absolute.

i 12,000

c

3

I 10’000KJ

8,000

I I I I6,0fxl

I 1’+% I

1 1 I 1 I I I , # ,

1.2 1.6

Pe/Pn(d) Fuel-air ratio, 0.100; inlet-

munlf old ~essure, 40 inoheamerowy absolute.

PAM. Ohar~-alr flow oorreoted to oonatant narburetor-

z0.

air temperature of 550° R. Engine 3, 40° valve overlap. G

Inlet-manifold

8,000 14,00c o 26

7!~ ++ 30x 39

40

6,000 12,00Q: 45

T x & 50

- -m

4,0Q0 10,000 . <i.

$ ~

P x.-i air ratio, 0.069.J2,000

; 4 ~n

h -r

.5‘ +

*1 O,OCQ . k 6,000 . . — — — — —

I \

!

-t L _

%

~ 8,m

I

6,000

v:

1.2 1.6 2.0 , o~ .4 .B 1.2 1.6 .

Pel~

(f) Engtie epead, 2200 rpm; fuel- (g) Engine ~peed, 2600 r~; fuel-ati ratio, 0.0B6. alr ratio, 0.100.

Figure i?. - Conoluded. Variation of oharge-dr flOW with Pe/~. Charge-air flow aorrected to

constant carburetor-air tauperatvre of 550° R. Ea@ne 3, 40° v~ve oveYlaP.

.

66$

.

.

NACA TN No. 1612

,

1.0

.9

.8

.7

1.0

●9

.8

.7

.

.

1.0

.9

.@

.7

1.0

.9

.7

I*O

.9Inlet- Fuel- z

.8

.7

.069 :I

v 40 .069 ~I

I

I

3I

——-.1.0 -

j

●9

.8 -\ 1600 ,Ej

●7 -1*S8,,Ia n*,, ,1,, ,, * ,#, ,m t* m, *,an

o .4 .8 1.2 1.6 2.0Pe/Pm

Figure 3. - VarlatLon of volumetric efficaienmywith pe/pm.

Engine 3, 40° valve overlap.

—

10

9

6

10 7

9

e 10

’79

a

47

96

8

‘7

69

8

r , ,-—

1 I

(a) ha-air ratio, 0.063.

10

9

8

10

9

$

4

10

9

8

7

,6

PelPm z(b) Fuel-alr rmtlo, 0.069. 0

.

Figure 4. . Varlatlon of d with pe/~ Values of 6 oor’rected to oonatant Inlet-manifold

tmparature of 660° R. Engine 3, 40° valve overlap.z

G

. .

NACA TN No. 1612

11

10

9

8

11

10

9

8

67

10

9

8

7

.

Figure

.

8 :

-t% * \ 2800

Inlet-manifold ]pressure

(in. Hg absolute~

11%.

10 4050

9 L

10

9

9

7 -

6 -IftvIt,I ,,10 .4 .8 1.2 1.6

Pe/P~

(c) Fuel-air ratio, 0.085.

4. - Continued. Variation of @ with’pe/~. Values of d “

#

corrected to constant inlet-manifoldtemperature of 660° R. Engine 3,40° valve overlap.

18 NACA TN No. 1612.

.

10

9

8

7

10

9

8

7

9 .

8 :

10 >

9 ;

8 :

7 :

10 ;

9 .

8 . L

7 - u

6 -Ill,~ 1800 , ,E:1,&I , ,,,m ,B z ,,, , ,, ,, ,,, 1~

o ●4 1.2 106Pe/;:

(d) Fuel-air ratio,,O.100. .

Figure 4. - Concluded. Variation of @ with pe/~. Values of $

corrected to constant inlet-manifold temperature of 660° R. Engine 3,40° valve overlap.

.

.

.

.

NACA TN No. 1612 19.

.

.0

E4

IE

El

.

.

1!20

100 [

so

100

So

60

00

60

40

80

60

40

80

60A r r

40 rrl-- -!% % .s..tt.n .,8*,,.I._l.LI.*.tt

9 .4 .8 1.2 1.6 0 .4 .8 1.9 L6

(a) Fuel-alr ratio, 0.06S.Pa/~

(b) Fuel-air ratio, 0.W90

F1K81w 5. - VariatLon of mixturetemperature minue eartmretor~e temperature T= - 2e with

PJPn . Euglne 3, 40° valve overlap.

20.

NACA TN No. 1612

.

120

lm

Km

60

lm

w

60

60

OR 60

60

40

60

40

60

40

S?o

[“’’1’0”““’‘“”““”““““‘“”““““:’”‘“Engine speed

(l’Pm)

Wo

d u r ‘ L J Y ~IriLet-maniro16

(in.p%%%ute )

o 2sf -t 30

❑ 402600

. m + -fJ 4F — — — — — o~L.I d

ASO

Engine epeed(rpm)

,

.

0 .4 .0 10Q, 1.6 0,.4 .8 102 1.6(o)Fuaba!r ratio, 000g6, Pe/Pm

(d) Fuel-air ratio, 0.100.

~l@re 5. - concluded. Varia&ionof mixture temperature minus carburetor-air tamparature l?n - Tc

~1~ Pe/~ . Engine 3, 40° valve overlap. ‘

.

.

.

.

NACA TN No. 1612 21

.

.

.

1700

1500

1300

1900

E“069111111a

1700 . 1,/ A’ -+-

t

o-r-

41500 -

1900 ~ 1 # 1 1I I

I I I [ 1

IL

1500 -11411,*I ,t,, ,#

.063I I I

1 1 1 I 1 t IL: 1- llb1 1 1 1 I I I a 1

o .4 .8 1.2 1.6

P*/Pm

(a) Inlet-manifold pressure,40 inches mercury absolute.

Figure 6. - Varfation or exhaust-gas temperature with Pe\Pm.

Engine 3, 40° valve overlap.

22 NACA TN No. 1612 -

.

3’

1800

1600

1400

MOO

16m

14000 .4 .8 1.2 1.6

Pe/Pm

(b) Variable inlet-mani~oldpressure.

Figure 6. - Conaluded. Varzation or efiaust-gas temperaturewith pe/~ .

Engine 3, 40° valve overlap.

.

.

.

.

.

*

NACA TN No. 1612

)

.

.

$

b

2.0

1.8 :

1.4

1.2

1400 1600 1800 2000 2200 2400Engine speed, rpm

Figure 7. - Variation of ratio of inlet-manifoldthrottle carburetor-inlet pressureair temperature, 5500 R.

~/pC with

2600 2800

pressure to full-open b

engine speed. Carburetor-

24

1600

1400

1200

1000

800

1400

1200

1000

800

1200

1000

800

600

NACA TN No. 1612

1

y:1 1 1 1 m a, * , n m , , , * , , , , 1 t n , , , ,* , , , , a , 1

0 ●4 .8 1.2 1.6

pe/&

Figure 8. - Ourves of brake horsepower from figure 1 plotted w%th curvesof brake horsepower from references 1 end 2. Inlet-manifold pressure,40 inches mermry absolute; fuel-air ratio. 0.08S.

-.

.

●

.

.

.

.

NACA TN No. 16t2 25

12,000

10,000

8,000

~

6,000

1 (Reference1),;

10,000.

6,000

8,000

6,000E

4,000

r

,, -:2,000 ,, ,,,, , m , * # # ,,tc1 ,4 .8 1.2 1.6

Pe/PmFigure 9. - Curves of aharge-airflow from figure 2 plotted with curves ofoherge-airflow from references 1 and 2. Inlet-manifoldpressure, 40 inchesmeroury absolute;f’uel-atrratio, 0.085.

26 NACA TN No. 1612

.

,

I“T’T1’”l’”””Engine

❑ I (Reference 1)Eng~ speed o 2 (Re~erence 2)

(rpm) ‘3%

&

1.2

-0-1*O

0 .4 .8 1.2 1.6

Pe/p=Figure 10. - Curves of volumetric efficiency from figure 3 plotted with

curves of volumetric efficiency from referenceel and 2. Inlet-manifoldpressure, 40 inches mercury absolute; fuel-air ratio, 0.025.

.

.

.

.

NACA TNe

●

No. 1612 27

l`'`'1''1'1''''l' '`"l-ll''.r"l.. ~l'..=l."."l=. ".1..".]Engine speed

(rpm)

82400

I

I I I I 1\T. 1

IL.

II I I I

6

1 (Reference 1):1 2 (Reference 2)=

8

10

0 .4 .8 1.2 1.6

Pe/PmFigure 11. – Curves of d from figure 4 plotted with curves of @from references 1 and 2. Inlet-manifold pressure, 40 inches mercuryabsolute; fuel-air ratio, 0.085. Values of d corrected to constantinlet-manifold temperature of 660° R.

28 NACA TN NO. 1612

18

1600

Engine

.● 1 (Referenoe 1)

2 (Reference 2)x 3

1800

1400

P~/Pm

Figure 12. - Curves of exhaust-gas temperature from figure 6 plotted withaurves Or exhaust- as temperature from references 1 and 2.fold pressure, 40 fnches mercury absolute; fuel-air ratio, O%ZYm=’-

.

.

●

.

.

29.

8

●

“*

NACA TN No. 1612

.

Pehm(a) Engine speed, 9200 rpm; fuel- (b) Engine epeed, zw rpm; ?uel-

alr ratio, 0.063; inlet-manifold alr ratio, 0.08.5;inlet-mnirold~eseure, 40 inohee merouryabeolute.

preeeure, BO lnohee merouryabeolute.

Figxra U. - Verlatlon or oompound-pawer-plant perrormenoe tith pe/~ fm. oaupound power plantstbraadirferentengties. Flight velooity, 400 mllee per hour; altitude, 30,000 root.

using .