MR No. E5T04ti

NAT!ONAL .ADVKORY COMMITTEE FOR AERONAUTICS&&!w————

October 1945 asMemorandum Report E5J04

CORRELATION OF THE CHARACTERISTICS OF SINGLE -CYLINDER AND

FLIGHT ENGINES IN TESTS OF HIGH-PERFORMANCE FUELS IN AN

AIR-COOLED ENGINE

I - COOLING CHARACTERISTICS

By Robert W. Wilson, Paul H. Richard, and Kenneth D. Brown

Aircraft Engine Research Laboratory ,,,

Cleveland, Ohio ,,,’ ...,.,’ ‘-”...

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NACA ~~‘“““.,

WASHINGTON

NACA WARTIME REPORTS are reprints of papers originally issued to provide rapid distribution ofadvance research results to an authorized group requiring them for the war effort. They were pre-viously held under a security status but are now unclassified. Some of these reports were not tech-nically edited. All have been reproduced without change in order to expedite general distribution.

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ITATIOli&GhVISdRY COMMITKEE ~R Almcmfiumcs.... ,- ,..~ *~T’ ‘- . 1“

for’the “

Air Technhal S&Woe Cmmati, Army Alr Foroes

CORRELATION OF THE CHARACTERISTICS OF SINGLE—CYUNDER AND FLIGHT

EIVGIKESIN TESTS OF HIGH-PEKFORMAIKIEFUELS IN AN

AIR-cooxmImiGm

I - COO=G CHARACTERISTICS

By Robert W. Wilson, Paul H, Richard, and Kenneth D. Brown

SUMMARY

Variable charge-air flow, cooling-air pressure drop, and fuel-air ratio Investlgatlonswere conducted to determine the coolingoharacterlstlcs of a full-scale air-cooled single cylinder on aCUE setup. The data are compared with slmllar data that were avail-able for the same model multicylinder engine tested in flight in afour-engine airplane,

The oylinder-head cooling correlationswere the same for boththe single-cylinderand the flight engine. The cooling correlationsfor the barrels differed slightly In that the barrel of the single-cyllnder engine runs cooler them the barrel of the flight engine forthe same head temperatures and engine conditions.

INTRODUCTION

At the request of the Air Technical Service Comuand, Army AirForoes, an investigation is being conducted at the NACA Clevelandlabo~to~ to evaluate trlptane and other high antiknock a_ddltivesas blending agents of aviation fuels. A ~rt of thie pI’O@M(liS tocorrelate the knock-llmlted and ooollng-llmitedperformances of asingle oyllnder on a CUE setup with those of a multlcylinder engineIn flight.

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NACA MR No, E5J042

tant

.. ,The relation Or the knook M&t to the.cooling limit is impor-in predicting the maximum esfe engine performance. Whereas the

knook limits of the single-cylinderand fli&t engines msy matoh,, the cooling limit of the single-oyllnder engine could be very dif-

ferent from that of the flight eng!ne. The knook-l~mlted performanceof the elngle-cylinder and flight engtnes compared under a varietyof engine o~ratlng conditions lM reported in @rt II.

The cooling characteristics of theIn reference 1. The tests presented Inat the NACA Cleveland laboratory duringstudy of the single-cylinder cooling by

flight engine are presentedthis report were conductedApril 1945 and permit thethe NJICAcooling-correlation

equatlms.

INSTRUMENTATION

An attempt was made In the single-cylinder tests to simulatejust as close;~ as possible all the-cond~tions of the flight testsreported in reference 1, with which the single-cylinder da% obtainedin these tests were to be correlated. A front-row cylinder for theMUM model engine was used In the setup ehuwn in figure 1. The com-m“ession ratio in bcth cases was 6.7. A vaporization tank was Installedin the shgl~-cyllnder setup (fig. 2) to simulate the mixing and vaper-lzing of the fuel in the flight engine. A standard engine intake pipewas Irmtilled to represent the induotlon system of the flight engine.The fuel was 28-R in both series of tests.

The location of thermocouples and pressure tubes in the flighttests is set forth in detail in the appendix of reference 1. Thelowtions were kept as nearly as possil?lethe same in the single-cylinder setup. The cooling-air pressure distribution that wouldbe encountered in flimt was simulated by cooling-air turbulencevanes in front of the single cylinder. C31ind9r te~ratures weremeasured by iron-constantan thermocouples looated at the rear-spark-plug gasket, the frCnt-t3park-phZgboss, the rear-spark-plug loss,the rear middle banel, and the rear fhnge. The mixture tempera-ture In both cases was ‘zaasuredby an unshielded iron-constantanthermocouple installed In the center of the SOo elbow of the Intakepipe. In the fllght tests the tixture anticyliudef twtiT:yre.turesworedetermlr.eciircm an average of the 14 cyl:nd9rs. ‘Thecooling-airpre”sauredrop acrons the single cylinder fm both the cylinder headsand barrels was determined from the differential of the total pressureahead of the cylinder and the static pressure at the rear of thecylinder. The ccoling-alr preesure was corrscted to a standard ah?density of 0.002378 slug per cubic foot ahead of the cylinder.

IWACA m No. E5J04 3

The cold valve olearance~ for the ahgle--oylinder engine were.. .. set at 0.090 inoh.for th9 Intakq-val.vsand 0.060 inoh for the exhaust. ...

valve. These valve cleeranoes were foti In ‘a‘pmvibus inveatlgaticm(referenoe 2) on the same alngls-&linder setup to give a running.valve ttmlng dose to that specified for the multioylinder engine(Intake opens, 36° B.T.C.; Intake closes, .60°A.B.C.; eihaust opens,76° B.B.C.; exhaust closes, 20° A.T.C.). The cold valve clearancesfor the flight mgine were set at 0.020 tnch as apeoified by theengine manufacturer.

Three t~s qf cooling test were rundata to compare with the ~ooling data for

to obtain single-cylfnderthe fli@ht euine rme-

sented In reference 1. TW cha=be-air flow, the ~oolin~-alr-preesuredrop, and the fuel-air ratio we;”eIndependently varied and at condi-tion very closely mtohlng &hose of the flight-engine teets. Theengine operatl~ conditions that were used in the eingle-cylinderteets are preeented In the following table:

SII?GLk-CYIJ- ENG13tE(Y?ERATINGCONDITIONS

@hq@e speed, 2250 rpm; spark advance, 25° B.T.C.;cooling-air temperature ahead of cylinder, Ta, 5a0 F.]

Engine Conditions

. ——.

Char e-air flow, ~,lbL -cyllnder

Coollng-alr pressuredrop, In. water:Head UAWBarrel OA~

Fuel-air ratio. Dm inlet-air temperature. OF

—-— —. —— -Test m-lables

~ir flowlnressure drc~

Varied I 405i

I11.6 1

IVaried

10.7 Varied

0.060 I 0.060200 I 200

BESULTS ANDDIS~ION

——.. . — ..Fuel-airrat10

413

11,811.O

Varied180

catparison of engine temperature8. - Figures 3, 4, and 5 are apresentation of cylinder temperatures and engine peeormence againstoharge-air flow, cooling-air pressure drop, and fuel-air ratio,respectively, for the sin&le-oylinderand fli@t engines. The

cylinder-head temperatures for the single-oylinder and flighteng-s matoh very well, but the cyllnder-barrel temperatures forthe single-oyllnder engine are lower than for the flight engine.Single-oyllnder engine performance IE!presented cm an indicatedbasis and flight engine performance (from reference 1) Is presentedon a broke basis. Tho cooling-alr-preesuredistrlbution for thetwo engines was not the same in that the pressures were higher forthe barrels and lower for the heads of the single-cyltier enginethan for the flight engine.

In order to compare t&e cylinder temperatures for the single-cyllnder and flight engines the clifference in the ooollng-air tem-perature ahead of the cylinder Ta, for the eingle-cylinder andflight engines (18° F) was added to the cyllnder temperatures ofthe flight engine. The cooling-lr temperature ahead of the oylinderTa, for the single-cylinder en@ne was 58° F and for the flightengine was 40° F.

In figures 3, 4, and 5 the mnlf old pressures of the single-cylinder and the flight engines differ in that the points of mess-urement were different.

Figures 6 and 7 show that for the single-cylinder and flightengines the rear-~k-plug boss and the rear middle-barrel temper-atures have the eeme relation to the rear-spark-plug gasket and therear fl.angetemperatures, respectIvely. In figure 7 there is nostraight-llne relation between the temperatures for the variablecooling-air p..ssure drop runs but the temperatures for the single-cylinder and flight engines fall on the same curve.

CwlparIson of engine cooling by the NACA correlation method. -The NACA cooling-correlation equations as used for the flight engine

..—

(reference 1) are as follows:

n/m m

()

~.Ta Wc

‘== OA~‘a-~

and

~-Ta

()

~ n/m mc—=

‘gb -Tb K CM%

1“

NACA m Ho: E5J04 5

where, . . -...-..-!, . . . . . . r.. ., .._

averiagecylinder-kid tempemtiiure’,*” ‘s- .- ‘-‘- “ ‘

average cylinder--l tempenture, OF . -.. .

cooling-air tempe~ture ahead of oyllnder, OF

mean effeotive gm tempemture for head and barrel,” . .respectively, OF

oharge-air flow (on ~li@t-engine hsl13), -e.

ratio of cooling-air density ahead of cylinder tostandard air density of 0.002378 slug/cu ft

cooling-air pressure drop for head and barrel, respec-tlvely, in. water

empirioal constants

the cooli~ correlation presented.in this report the rear-spark-QIug boss @ w rea tiddle-~rrel tem?era~ures were usedas an indication of Th cindTb, respectively.

Followin8 the procedure used in references 1 and 3, variationsof Tg with ohangea in dry tnlet-oharge temperatures are accGunted

fcr by using a reference man effective gas temperature %o for Q

dry Inlet-charge temperature of 0° F and the following equations(from reference 4):

‘gh = Tg% + 0.8q

T8b

=T + 0.42 Tmgob

where

% dry Inlet-charge.temperaturejOF

reference =n effeotive gas temperature for head and‘% ‘&b barrel, respectively, % (Tm=OOF) Tgo is solely

..a function of fuel-air ratio in these tests.

.

-“. . . .

6 lrkuxMRNO.15J04

Ih the oorrelatlon for the single-oylinder engine the samevalues of T

%and T

%(1086° and 536° F, respectively, at

a fuel-alr mtlo of 0.080) were used as in references 1 and 3.”

The values of the constants n, m, and k in the correlationequations were deterrulnedfrom the variable oharge-air fluw andcooling-air PressL-e drop tests at a fuel-air ratio of 0.080. The~iatim d ‘8~h

- ’60bwith fuel-air ratio was then-deter-

mined from the variable fuel-air ratio tests.

The exponent n that governs the effeot of charge-air flow on~-Ta ~-Te

the functions ~ — is evaluated from ths slopesgh

-Th-Tgb

- Tb

of the plots shuwn intlgure 8.

The exponent m that goven.s the effect of uooling-air pressure% - ‘la % - Ta

drop on the functions ~-~~- and ~—%-Q

is evaluated fromtlie&!n

slopes at the plots shown In figure 9.

Final ooollng-correlation linsa for heads and barrels of thesingle-oyl~riiersad flight engines were obtained by using the expo-nents detemlned from the plots shown in f~gure~ 8 and 9 and by

r, - Ta ~-Ta ~cdmplotting .;/+-- and ~~ — (fig. 10). Theagainst ~Ap

gh h ‘%bcooling equations obtained were as follows:

For heads, single-cylinderand flight engines:

~ 2.134 0=320

()

%- ‘a .00270 c

‘gh - %c?Aph

For barrels, single-cylinderengine:

Tb - ‘I’a o~ 1.614 0.438—= 0.340 ~‘gb - % \~@b

1-

NAcA MRNO:E5J04

For barrela~ fll@t engine:-, .,, .-..--,-..-,.,....... ,.,-...

Q-Ta

()

~ 1.309 0=567 ‘- I .- .-= 0.505.

‘6b - ~ *

For the single-oyllnderand fll@t englu.esthe oonstants inthe equation for the heads are the same, which indicates the _relation of head temperature to ohange in power and cooling-airpressure drop with other conditions the same. The constants.inthe equation for the barrele are, however, different for the twoconditicms because the barrel of the singie-cylinder englns runscoolor than the barrel of the flight engine for the same power endcooli~ -air pressuru drop.

Figure 11 is a plot of Tgo

~inst fuel-air ratio for the

heads and barrels of the single-cylindercnd the fll@t engines.The l’r curves for the flight engine were obtained from data at

a wtde%ariety of engine conditions. (See references 1 cmd 3.)The Tdo curves for the single-cylinder and fli@t engines match

fair”~ well.

SUMMARY OF RESULTS

Tho cylinder-head cooling correlationswere the same for boththe ein@e-cylinder and the flight engines. The cooling correla-tions for the barrels differed slightly in that the barrel of thesingle-cylinder mglne runs oooler than the barrel of the flightengino for the eam6 head temperatures and engine conditions.

.

Aircraft Engine Research Laboratory,National Advieory Committee for Aeronautics,

Cleveland, Ohio, Ootober 4, 1945.

— --——--- ———-1

8

RmERmcm

1. Werner, Milton, Blaokman, Calvin C., and White, H. Jhok: Flightand Test-Stand 13.westigationof High-Performance Fuels In Modi-fled Double-Row Radial Air-Cooled Engines. I - Determination ofthe Cooling Charaoterlstics of the Flight Engine. NACA MRHO. E5G09, 1945.

2. Cook, Harvey A.~ Richard, PaulEPfect of Valve Clearance onEn@ne Cooliw. lVACA~ NO.

H., and Brown, Kennsth D.: Thehock-Limited Performance andE5DI.8,1945.

3. White, H. Jaok, Blackman, Calvin C., and ~ndois, Mazzoel:”Fli@tand Test-Stand Investlgation of High-Petiormance Fuels in Double-Ruu Radial Air-Cooled Engines. III - Comparison of CoolingCharacter stlcs of Flight and Test-Stand Engines. NACA MRNO.E5B23, 1945.

4. Corson, Blake W., W., and MoLellan, Charles H. : Cooling Char-acter stIcs of a Pratt & Whitney R-2600 Engine Installed in an

“NACA Short-Nose Hi@-Inlet -Velocity Cowling, NACA ACR No. L41?G6,1944,

.

NACA MR HO. E5JOU

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NATIONAL ADVISfM?YCOMMITTEE FOR AERONAUTICS

Figure I. - Air-cooled single-cylinder setup.

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NATIONAL AOVISORVCMITTEE FOR KR~AUTICS

Figure 2. - Induction system used In singie-cyiinder setup.

NACA MR No, E5J04

F18qre 3. - Verletlon Or cylinder t.empmtumo C@ englm perf~ with Ch0r80+lbflwfor tk single-oyliuler ard flight engines. Single-oylinder engine performnw In preeentedon en ldioated beslo d flight engine prf~ (mferenoe 1) 1s preeented on a bmkaheals. En@M speed, 2250 ~; ccapreoslca mtio, 6.7; apakadmnce, 25° B.l!.C.; fuel,28-R; fuel-air mtio, 0.080; single-cylhder mollng-etr WOaeum drop, tiph, 11.6 k. SO;

oA~, 10.7 in. SO; flight omling-air preaeure drop, oA~, 11.8 in. SO; oll~, 10.1 in. SO.

Cyllnder temperatures, ‘FRear-spark-plug gasket Rear-spark-plug boss Front-spark-plug boss Rear middle barrel Rear flange

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NACA Ml? tiO* E5J04

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YFl&ure 5. - Verletionof cylixler temperatures ti englm performnoe with fkwl-eir ratio for

the single-oylitir ml flight ●ngime. Single -qllnder englm perfommx. . indicated ~is cud fl%ght exhe performme

Im preeented cm(referenoe 1) 1s pmmentwl on a broke kuslm.

l!ogfne#peed, .250 m; capzweai- mtio, 6.7; qm.rk admmm, 2?5°B.T.C.; frsl, 28-R;FIn@e oylimler: coolln&eIlr pressure &oP, O@h, 11.8 in. E20; =~s U.o ~. R20; ~-

fold premnm, 39.6 in. x abe.; flight: mollalg-elr pmseere drop,UA%, u?.2 in. SO;oil~, 10.4 In. ~O; _ifO).dpremnm, 35.2 in. x abms

HACA MR HOC E5

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COMMITTEE FOR AERONAUTICS

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280 320 360 400 440 4$30 520Rear-spark-plugboss temperature,‘F

Figure 6. - Comparison of rear-spark-pluggaslostte~rature with rear-spark-plug boss temperature for the single-cylinderand the multi-cylinder engine. EMine sped, 2250 rpm; compression ~tio~ 6.7;

spark advance, 25° B.T.C.; fuel, 28-R; fuel-air ratio, 0.080.

—Variable charge-airflow run

2 — ------Variable cooling-alrpressure drop run

11* 121

160 200 240 2&!o 320 360Rear middle-barreltemperature,‘F

Figure 7. - Comparison of rear-flange temperature with rear middle-barrel temperature for the single-cylinderand flight engines.E~ine speed, 2250 rpm; compression ratio, 6.7; spark ad%ance,25° B.T.C.; fuel, 28-R; fuel-air ratio, 0.080.

NACA MR NO. E5J04

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Fl~ 8. - VariationofTh> ati‘~T withcharge-airflow,WC,forthegh - ‘h ‘% - ‘b

single-cylinderatiflight engines. Engine t3p8ed, 2250 rpm; compreeeionrntio,6.7;sparkadv~e, 25°B.T.C.;fuel,28-R;fuel-airratio,0.080;cooling-airpreaaureA.rep:‘iPhj11.6in.~O; uA~, 10.7in.1$0.

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Th .Ta ~Tb - ‘awith cwlingair pressuredropforFl@re 9. -Waz=latim of —a —‘%

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thesingle-oyllmleratifli@t englnee.Enginempeed,2250rpm;canpmoelonratio,6.7;spark advance, 25° B.ToC.;fuel,28-R;fuel-lrratio,0.080;charge-airflow,405lb/hr-cylinder.

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NACA MR NO, E5J04

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Fi@re 10. - Cooling-correlation ourvee ror the eingle-oylitier and flightengines. 13n@na speed, 2250 W; canpreseion ratio, 6.7; aparlcadvanoe,250 B .T.c.; fiel, 28-R; fuel-air ZUtlO, o.o~.

. . . .. .... . . .. ... . .-. —...-——

NACA 14R NO. E5J04

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COMMITTEE FOR AERONAUTICS II 1“’’l’’’’rrl””i

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Figure 11. - Variation of mean effect17e gas tamparature Tgn with fuel-

air ratio for the eingle-oylinder and fllght engines. Engine speed,2250 rpm; oomprasslon ratio, 6.7; epark advanoe, 25° B.T.C.; fuel, 28-R.

IIllll3 117