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NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS. . . .,–.- _

W“lurrmll ‘lMMDORT.

ORIGINALLY ISSUED.. June 1944as

AdvariceConfidentialReportL4F06

COOLINGCHARACTERISqxCSOF A PRATT& WI- R-@)().

ENGINE@TAILti- IN AN NACA SHORT-NOSE

HIGH---vELOCITY COWLING

By BlakeW. Corson,Jr., and CharlesH. McLellan

LangleyMemorialAeronauticalLaboratoryLagley Field,Va.

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NACA W.~TIME REPORTS are reprints, of papers ori&inaUy issued to provide rapid .distribut.ion ofadvance research results to”an authorized group requiring them for the war effort. They were pre-viously held under a security $tatus but are now unclassified. Some of these reports were not tech-nically edited. All have been reproduced ‘vithout change in order to expedite general .$3istribution.

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~ L-207

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#I 31176013649696

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NACA ACR .1?0● .L4FM ,....

., ,;N4sTIONALADVISORY “COMMITiER FOR AEROMIUTICS “..,.. ..:.,:. .“ “.

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ADVANCi -CCWFIDENiI&..REP0RT” . ,,, .,,,--,.“;~,“..;... ● . i.... .’. . . ..;.

C00IJNG C’iARACTERISTICS OF A PRATT ii ‘WiKP&Y R-2900

!“lEGINLINSTA1iLZDIN AN NACA S130.RT-2!0S2

HIGH- IN13T-W.LOCITY

By Blake ‘W..Corson, Jr., andrl..

suMMAfi-Y

COWLI?W ‘..:Charl;p ‘~...”McLellan” ““”“:.:.

An investiCatiionhaa been made of ~he coollng charac-teristics of a,Pratt & Whitney R-200@ en~ine ds installedIn an NACA short-nose hi~~h-inl’gt-velocity cowlin~ (thelkC.4D~ cowllng) . The t.3st3 were made In tka LMAL 1~-fcmthigh-speed tunnel of a stub winr and nacelle cOrd2inatiOna,

!ke intera~l aerodynamics of the cowling were studiedfor ranps of’ gwpeller-.advanco ratio uxl inleb-velacityratio obta~.nedby the de”flec’tionof’the cowlln(;flaps.The eilg$ne-cooling tcsta included variations of er@nepower, fuel-air ratio, and cooling-air pressure drop.

‘TM en~ine-cooling data have bean presant,3d in theform of the NACA erigine-coolia~.correlation curves; .EUM “an illustrative examplo of’the use of these cur7es forcalculation of engine-cooliqg requirements in fli@t isinclude,d, ., “

INTRODUCTION.,..

The “purpose.of the present lnves”tl~atton was to”establish the cooling characteristics of a.Pratt & WhitneyR-2800.-E erqqineas installed In an NACA”short-nose high-”inlet-~[ploctty cowling (the~N~CA Ds cowling), For the “tests the enghe. was.mountsd on a gtub win- and onclosed-

!?by the NAdA J)S Cowltng and.”anacelle. Th .s”,cowlingwas.developed from the N.4CAC cowling, described in reference 1,to provide a lower-draC installation, higher pressurerecovery at the front face of tho”enzine. and a h5xharcritical Mach number. The engine-c;ol.ifigtests w=re con-ducted in the LMAL 16-foot high-speed turiel.

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2 ?iA!2AACR NO. L4F06

The engins was operatad over a range of power”up torated power. The effects of varlatfon of’ooollng-af.rpregsyre drop and fuel-air ratio upon engine temperatureswere”measured. The data are prssented in a form suchthatz for a given set of flight and engine-operating con-ditions, the average and maxhum cylinder temperaturesmay be readily obtained.

DZSCRIPT’ION OF MODEL AND AFPARATIE

The model, a full-scale stub wing and nacelle, isshown in figure 1 mounted in the test section of the IMAL16-foot high-speed tunnel.

The power plant is a Pratt & Whitney R-2800 A-seriesengine converted to a B-series, which has a normal ratingof 1600 horsepower at 2400 rpm., This engine, an 18-cylindsr, two-row, radial, air-cooled type, is equippedwith a sinqle-sta~e, two-sp~ed, qear-driven supercharger.The supercharger gear ratios are 7.6:1 for low blower and9.9:1 for high blower. For this particular engine, only“the low blower could be ussd. The propeller drive, a2:1 ratio reduction gear, incorporates ths standard Pratt “& Whitney torque meter, which measurgs the reaction fromthe propeller reduction gears. The engine is equippedwith a Stromberg PT-13G1 injection-type carburetor.

The propeller is a controllable three-blade HamiltonStandard propeller A6257A-6 with a diameter of 12 feet7 inches. The cuffs on this propeller had previouslybeen trimmed for a larger spinner than was used in thepresent tests. The excess clearance between cuff endand spinner surface was therefore reduced by balsa-woodfairhgs held in place by doped fabric.

The general shaps and coordinates of the short-dlffuser cowling are given in figures 1 and 2. Thecowling exit flaps controlling the engine cooling-alrflow extend around the periphery of the cowling exceptfor a short distance at.the top where tlw carburetorduct blocks the exit; The individual exhaust stacksterminate at the cowling exit slot as shown in figure 2.A calibration of the exit area of the cowling, withallowance for these stacks and the carburetor duct, ispresented In figure 3.

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NACA ACR ~Oc L4F06 E 3

— In-addttion-to the usuLt.engiml.,instr~.nts, ....pro.-vtsions were made for measuring the fuel flow, weightflow of engine charge air, cylin~r temperatures~ weightflow of cooling air, and engine cooling-air pressuredrop ●

The fuel flow was measured by both a calibratedrotameter and a weigh tank. The weight flow of chargeair was measurad by a calibrated venturi in an auxillarycharge-air duct, The conventional charge-air scoopwas blocked off, and the auxiliary duct brought theengine charge air from out of doors through the venturi,thence through the vertical duct shown in figures 1 and2 to the carburetor top deck. ~ this way not only wasmeasurement of the ctirge air facilitated, but also thedanger of engine detonation was mini~lized because thewarm air f~om the wind-tunnel stream was not used in theengine. Pulsation from the propeller was avoided; and,because the total pr~ssure of both the wind-tunnel streamand the outside air was atmospheric, pressure at the car-buretor dsck was not sacrificed.

Temperatursa were measured by calibrated iron-constantan thermocouples and ware recordod on a Leeds &Northrup Speedomax. The cylinder temperat~u’esweremeasured at the war spark plug und at the base of allcylinders. The temperatures at the spark plug weremeasured by gasket-type th~rmocouples and hy a therrno-coup19 embedded iIYeach rear spark-plug boss (fi~. 4).The base thermocouples were embedded in the rear of thebase flange. The temperature of the engine charge airwas measured at the top deck of the carburetor.

The weight flow of the engine cooling air wasmeasured by the four shielded total-pressure ”rakes andthe surface static orifices In the cowling entrance (fig.5). The pressure tubes for measuring the enginecooling-air pressures were located as shown in figures 6to 8. F~ont pressures in the baffle entrance of thefront cylinders were measured on only one side becausethe other baffle ent~ance was in the wake of a push rod,as shown in figure .7,

The gasoline used throughout the tests met the Army-Navy specifications. This fuel is a blue, leaded gaso-line, which has an antiknock rating of 100 octane and acalorific value of not less,than 18,700 Btu per pound.

4 NACA ACR ~~0.L4F06

SYMBOLS

P pvessure referenced to free-stream static pressure,pounds per square foot

P mass density of air, SIWS nor cubic foot

v velocity, feet per second

q~ impact pressure, compressible dynamic pressure,

( +)pounds per s~uare foot Fc V2

Fc ($compressibility factor for air 1 -t +M4+ .OOZ-m )

U Mach number, the ratio of alrspaed to acouSticvelocity

V/n!)

n

D

‘T

CP

P

‘a

AP

Wa

we

propeller-advance ratio

engine rotational s~eed, r~m

propeller rotational speed, rps

propeller diameter, feet

angle of attack of thrust axis, deCrees

P(\power Coef’ficieilt—pn~D51

power, foot-pounds per second

velocity in cowling entrance, feet per second

relative density of air6.~W

relative density of air a~ stagnation point (relatlvedensity of cooling air)

cooltng-air pressure drop, pounds per square footor inches of water

wsl&ht flow of coolin~ air, pounds per how orpounds per second

weight flow of charge air (without fuel), poundsper hour or pbunds per second

EACA AOR No- L4F06 5

T“Thn.a,.. cylinder-head temperature. (average indication of

“18 thorhodbnples embedcledsnear..rear sp.aak=plu~,. boss9s), ‘F

“’!.% cylinder-base temperature (average @dlcation of18 thermocmmles.e rnbedded in cvlitid.er=base

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flangbs), ‘F”.

Ta cooling-air temperature (sta.nation-air tempera-ture in front of engine), SF

‘~ mean effectivt3 gas temperature, ol?

,

1

‘E% mean effective gas temperature for the cylinderbases, ‘F

%3*0 reference mean effective gas temperature (for 80° Fcharge-air temperature)~ ‘1?

Te charge-air temperature alheadof c.arburetorO ‘F

CPspecific heat at constant pressure, Btu per poudper oF (For air, 0.24)

x, y, and z exponents ~ssociat9d with Was WeO and ~aAP~respe9tlvely

cl~ c2,c00C5 constants

A coefficient of friction power

B coefficient of blower power

c constant proportional to engine displacement

8 acceleration due to gravity (?i2.2”feet per secondpar second)

PeSL exhaust back pressure at sea level, absolute,inches of mercury

‘ealt exhaust back “prosaur~ at ~ltitude, absolute, inchesof mercury

.L!IROIWNAMIC9OF COOLING-AIR FLOW

The press-are recoveries at tha various stations with-in the cowling were determined tor the two extreme positions

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6 h NACA.AOR NO ● L4F06

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of the cowllng flaps~ gaps of 2.5 and 7.2. inches. Thesetests were.made at 260 miles per hour, with Cp = 0.20,

V/nD = 1.9, and the thrust axis at zero angle of attack.

The pressure recoveries at various stations through-out the cowling are shown In fZgure 9, expressed asratios to the compressible dynamic pressure. The plottedvalues represent the cirmmferentinl averages of thereadings of tinediffuser and individual cylinder preseuretubes shown in ftgures 5 and 6. The plots of total pren-sures measured by the cnwlin3-erltrance rakes at station Aof figure 5 show that, contrary to the expected results,the pressure recoveries are lower for the low-inlet-velocity condition with the cowlin~ flaps closed than frrthe hi~h-inlet-veloclty condition with the flaps open.The propeller blade sections in front of the cowlingopeninq were apparently stalled for the l.ow-inlet-velocltycondition becnusej normail.y~ the higher angles of attackof these mopeller sections would result in higher pres-sure reco~erles for the low-hlet-velocity condition,

~h~ front pressures on the “front-row cylindersare about the sarfi~cn’thn two cowling-flap posl.tions~as shown by curves B of ft~wre 9. The radial distribu-tion of the t,otGlpr~ssl~r~ over the cyllnder IS notuniform. The pressure tubes lr~catedGn the barreland cn tiletop of the head arg cut of the blast of

#r@m.t~]ediffuser and, ~o~~~qu~~ltly~ u~~~ - ‘iVS nuch .lower raadlngs than the tubes on the side of the head,which. are well centered in the ceolinG-air flow. TheFreasura recovery on th~ front of the rear cyliridersis less than thht on tke front cylinders and is alsorlorouniform “oecame of the losces of pressure encounteredin passin~ through t’hespaco between the front-rowcylinders.

The restricted front-cylinder exit passages between.th3 cylinders of the raar mw result in htgher positivepressures for the flaps closed and k lower negativo pres-sures for the flaps open than were recorded for th~ rearcyl’??ndsrs.This difference in rear pressures tends tocounteract the higher front-cyllnder front pressures andto equallze the cooling-air pressure drops across thetwn rows of cylinders, as shown in the fol.lowlng table:

1

NACA Am No. L4F06m ~ ‘7

Y. . . . . . . . ~ . . . . . . . ,., .,-Coaling-air pressure ..drop...~

Location Of (percunt q~ )pressure tubes Stations with cowliw flaps sgt

2.5 In. 7.2 in.

Front bankTop of head B to C. 43 85?ie&d BtoC 45 93”Bai’re1 Btoc 30 69

Rear bankTop of head DtoE 39 95Head Dto~ 37’ 65Earre1 Dtofl ~.j 82

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Ths pressure drops gl.venfor the cowlln$ with ths flap0 ~n.).cre nrobab?iplarpr than would beopen (~ap, 704 .

Cbtatned in ~l?.Ghtbocauso of the .qneutlj’incre~sadblocking effect of the ex$ended flaps in the tunnel.

The circumferential presolu-ed?.strlbution Ycr theengine is shown in I’tgures 10 and 11. T!:afront-bankpressures (fi~. 10) are fairly unif’arm with b~~ 5xcep-tion of the pressures for cylladers 2 an~ IS .~~ldthetop head tubes fcr the flup-o”~u:lcondition. ‘L’l.elotipressures on cylind”ars2 ur:cilb are pxm?ubly duo ellx.erto bul!.ss in til~inner cowliE.zl.ea~irud to clear tlmdistrifiutors or possibly to t~~eh~enkin~ down of t-w flowat this point because of the puesance of the blocked-offcarburetor-duct entrance just above the top of thecooling-air inlet. The pressure dlstrtbution on therear cylinders (fig. .11) was loss unj.for.mfor all.loce-tions with the cowlin~ flaps closed (rap, 2.5 In.),and with the cowling flaps open the front pressuresvaried as much as 0.4qc.

The results of tests to determine the effacts ofpropeller operation upon the coollng-alr pressure drop .are shown Zn figures 12 and 13. Tko proceduro for thesetests was to set the cowllng+xit fla~ and to adjust thepropeller for constant speed and po-wan; the wind-tunnelairspeed was then vai’iedand press~l~ameasurements .were taken.through a range cf V/nD. This procedure wasfollowed for three cowling-exit-flap settln~s and farthrse values cf propeller powar cce.fficient. The ov9r-all cooling-air pressure drops given in fi#ures 12 and 13

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NACA ACR NO- h4F06 9

-.. , R~sum& of enF~ne-coollng-correlation prjnciples.-U-.:,, Me””’principles of e~qine-cooll~oorrelati.on.,,ar~ .~a,s~don

the fundamental laws of heat transfer. The developmentof a technique for applyin~ these prfnclplos has beenpresented In references 2 to 4. A general statement ofthe correlation principle is that the ratto of coolhg-temperature differential to heating-temperature differ-ential Is a function of a relation between internal flowof heating fluid and external flow of cooling fluid. “This principle Is expressed symbolically by

~h - ~a vJeY Vvey=cl~=ca

Tg - Th a (aaAp)z(1)

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The XACA.method of correlating engine-cooling dataIs based on the concept that the true gas.temperature ofthe charCe ’.andcombustion products, which underCoes cyclicvariation within the cylinder, -maybe replaced Ly a h~po-thetlcal mean effective ga9 temperature Tg , It has beenfo~d (reference 4) that, of the several factors vk,ich.mayaffect the mesn effect~ve gag temperature in en~inesoperatir.g with fixed sparlcadvance, only two var~ ena~hIn normal operat?.on to demand consideration. These t~:ofactors are the ?’uel-airratio and the temperature af thedLar&e before entering the cylinder- A Generalizationof these.effects is expressed by

(2)

where ATg is a &as-temperature increr.ent associated

with inlet-charge temperature and where T8~()’ the refer-

ence mean effective gas temperature, is regarded solelyas a function of fuel-atr ratio and must be experimentallydetermined along with the other constants established Inengine-coollng-correlation test90

The precedent (reference 2) of using 80° F as areference temperature Te for the carburetor inlet airis followed here. In the absence of a blower the gas-temperature, increment is expressed simply by

The factor 0.8 is empirical but has been found satisfactory.

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When a supercharge is employed.in the engiqe .induction Systiem, the blower-temperature ripe must bo ,included In the gas-temperature Incitement. El?tlwlt:ml .of the blower-temperkturoof blower v(orlrwith heat,as nir-terlperature rise.basocion similtir analysis

Blmer rise =

..

CorreMtioI: riocrE:Irc.x, y, end z In c3quat=”E)tisn-curves, which arc plotof the ratio of texperat~reassoc?.ated variable l;a,Y:e

plats are obtained flwm tests uade in accordance with atest program of’which tke followin.fiis ty~ical:

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NACA AOR No. L4F06 11

During the test in which only the coolir!!-air pres-sure drop was varted as wall as the tc+stin which onlythe charge-air flow was varied, the fuel-air ratio was

,. ,i

held as fiearly a~ possible constant at O.0~. At this.value of fuel-air ratio, the datum mean effeotlve gastemperature

?3mis established b~ reference 2 as equal..

to 1150° F for the heads and 6000 F for ‘the bases. Themesn effective gas temperature was then computed by useof the following equations, which were derived from”equa-tions. (2) and (3):

For the heads,

I

.

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12 “~

and, for the bases, ~ “ ““

I 2.

‘!3 ( )]=600 +Oa8 Te-80+22~L ....Only low-blower tests were used to establlsh the correla=tion and all the quantities pertinent to the correlatj.onwere measured after the engine temperatures had becomestabilized.

All the engine-cooling correlation test data aro ~presented in tables I to III. A t~ical constructioncurve “used to obtain the exponent that governs the effectof pressure drop on engine coollng is shown.in figure 15.The data for figure 15 ware obtained from teslis2?40and -241 and are given in tab~les I and II. Figure 15 Is aplot of the.ratio of temperature dirferentlals for teqts ““in which the cooling-air pressure drop was varied sys=temtically and the engine char~e airW-ls held practically : . -constmt nt 775.0 pounds per hour- Tiumro 15 Is there-

-

fcrga graph

The slope of

of equation- (1) in tb.efoilowing form:

the “curve is -a ‘From figure 15, z = 0.321.

The construction curve used to obtain the exponentthat ,qovems the effect of’char~e-air flow on engine tem-perature is shown in flguve 16. ‘Thiscurve Is a plot ofthe ratio of temperalmre differentials for tests in whichthe engine charge air was varied systematically and the” ,{cooling-air pressure drop wus held practically constant

. .

at 14.2 inches of water. F’igtire16 is thereforw a graphOP equation (1) in the following form:

‘hqah = C4 Wey

Tha slope of the curve 1s y. From i’igura 16, y = 0.565.

l?yplottin~ the ratio of tel~peratura difl’er?ritials

/agaln~t Wey/z’o=Ap, all the data used in fixing th9construction cur%es were nlottod on a sin Ie curva repre-

fsentin~ the following form cf equation (1 :

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% - Ta.~~ = C2 ~=..c2.(-J=.oe56,.[-J8321

- Th ;“aahp~-”,

TM’s expression is an engine-cooling correlation equationbased on cooling-alr pressure drop and Is plotted infigure ,17. The value of the constant C~ = 0.560 wasdetermined from this graph.

Th~ vartatlon of reference mean effective gas tem-perature ‘gso with fuel-air ratio (fig. 18) was deter-

mined by tests 24.2and ~ (table II) after the corrsla-tiionline had been established. In this case the charge-air flow and cooling-air pressure drop were measured andtheir respective exponents were known for each test point.

The correlation abscisca/

Weyiz aa~p was computed and the, corresponding value of the ratio of temperature differ-

entials (ordinate] was read from the correlation curve offi~ure 17. The temperatures ~ and Ta were measured.The computation of ‘g

was then accomplished by

Th(1 + Ordinate) - Ta

‘13=— Ordinato

The reference mean effectiw gas temperature obta!ned byuse of equations (2) and (3) Is

%-go= Tg - ATg

This plot of ‘~go against .Wel-air ratio (fig. 18) is

essential to general application of the correlation curve.

An engine-cooling correlation based on the weightSlow of cooling air is establis”ned by a procedure similarto that followed for the correlatl.onbased on cooling-airpressure drop. Data from the same tests have been usedfor both correlations. The construction curve for thecorrelation based on weight flow of cooling air.1s pre-sented in figure 19. Curves are shown for cowling flapsopen and closed. FigWe 19 1S a plot of the ratio oftemperature differentials for tests in which the COOling.air flow (pressure drop) was varied systematically whilethe charge-air flow was held practically constant at77~0 pounds per hour; figure 19 1.stherefora a graph ofequation (1) in the following form:

1

14

“%-4 = C5 W*”X

TIM 310pe of the cuwes is -x. From figurs 19, x = 0.6A2.

.

Graphs, similar to those by which tlhecoolingcharacteristics cf th’?cylin~~r heads Eavg been rresentedin f:Lgures15 to 21, are ,rivenfor the cylinder bases infigures 22 to 28. Data for tha tases ars given in

lMCA ACR No, L4F06 15

table III. Engine speed had no measurable effect on—. -“-cyl,lmder-hsadtemperatures except through,its effect on

the blower-temperature rise, which was accounted for.Inasmuch as the heat generated b?:piston friction hasdirect eftect on the cylinder-base temperatures, thebase temperatures are affected by engine speed. Theeffect of engine speed is shown In flbmre 25 by thedisplacement of points from the curve of reference meaneffective gas temperature f’orthe bases- Base tempera-tures at speeds greater tiian2120 rpm were greater thanindicated by the correlation curve and, consequently,the effective @as temperature was higher; the converseis true for points at low engine speeds.

Typical distrlbuti.ons of cyllndgr-head and basetemperatures for two cowling-exit-flap settings are

. presented in figure 29- As was found in all tests,tho fi’ont-cylinder heads ran considerably hotter thanthe rear-cylinder heads. The difference in the tem-perature readings was somewhat ~reater for the embed-ded thermocouples than for the spark-plug-gasketthermocouples. The temperat.uras of the front andrear cylinder bases were a~:.roximately eql~al. Thevariation between front-row temperatures and rear-rowtamparatures was less systonatic on the cylinder basesthan on ths cyllnder heads.

A comparis~n o.~the avaraga temperature of tliefront row of cyli.ndqrswith the average temperature o.fthe rear row of cyl+.ndera :s shown in fl~ure 20. corn-parisons arc made at 800 and 1100 brake horsepower bothon the basis of spark-plug-rasket and embedded thermo-couples. FQuve 30 indicates that tlieaverage front-cylinder-head temperature was of the order of 50° Fhotter than that of’ the re~r-row cylindsr heads at higherpowers. Mtermination of the cause for this temperature

:,.’ diffarenca between front and rear cylinders is beyond thescopa of tho present paper.-.

,

i 1Us3imation of charge-air flow.- 0n9 of the principal~.1 facto~nvo lved In a coolinz correlation is the internal““4

L flow of heati~ fluid. In ~nternal-ccmbusti.on enginesthe flow of heating fluid is most directly related to the

[~ cb.arge-air flow. The correlation ,method, consequently,has been deveIoped with charge-air flow as a primaryvariable. Inasmuch as charge-air flow is usually notspecified for various engine operating conditions, a

.,

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16

method for estimati~, the

HACA AOR ~;O● L4iI’06

charge-air flow required forany condition of engine-airplane operation is necessaryin the application of the engine-cooling correlatlan.

vvhere (4)

ihp j.ndicated b.orsspcwer &s dofimd by equation (4)

A coef’f!c15nt of frlstion o.]wcr

B cocfflcltintof blower pow~r \

c consta~t proportional to e@.ne dia~lac~ment

\

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NACA AOR ~O”oL4F06 “~ 17

B= 0.0495 ~Impel.ler dlam.)(Blower gear ratlo)]2. ... .........- -------... .........+_..““””0”-0495(0.917X 7.612 “-”””’-”‘“““-”““:-“’” “=

= 2-4

The constant C provides for the power increase withaltitude due to the decrease In exhaust back pressure.By allowing a pressure of 70.7 pounds per square foot perinch of mercury, the power increase is

hp =

“c ==

where the

70.7 x ~lne displacement2 X 1728 X 60 X 550 (peSL - pealtJ1~

0.00062(Englne displacement)1 ● 735

engine displacement is measured in cubic inches.

The expression of indicated horsepower then becomes

Low blower

The constants Eiven In equations (5) and (6) are notintended to be used individually for the calculationeither of friction and Blower horsepower or of the powerobtained from decreased “iwckpressure- Equation (6)can be used with figure 31 to determine the enginecharge-air flow with satisfactory accuracy. Figure 31,which presents indicated specific air consumption as aunique function of fuel-air ratio, was prepared by useof equation (5) and the same data (table I, tests 242and 244) that were used in establishing the curve ofreference mean effectiv~ gas temperature. Data fromother tests are include’d in”flgure 31.

Equations (5) and (6) can be rewritten to furnish adirect solution for the engine charge-air flow when usedwith figure 31.

a “NACA ACR NO, L41’0618

Low blower

() 2 / TJ”bhp + 27 i$m. (

- 1.735 pe~~ - %alt)\tiPT )we =

()

2

& - ‘“0024 am

(7)

Hi&h blower

I)eterm!.nsthe vcrlatlan of hattest c~lindor-headtemperature with cmoling-alr jwesaure drop ncross theengine for the enflir-e-airplane.c,omhir.s.ticndescribedherein for the f’ollowi~ operatln.q ccnd~tionc: Armysummer air, 2000 hor~epower, low blower, 2700 rpm, ada fuel-atr ratio of 0.107. ~~~sune low oirspeed - that1s, negligible effect of rdr~peed on coo2inC-alr tem-perature.

1?

I;ACA

(1)-“ .... .... .

(2)

(3)

~h

ACR NO, ~l?06

Eatimatlon of oharge air:-,.Frti fl~ure”31, ‘“-”at a “fuiil-”airra-ti,odf “’0;107,

we— = 6.43ihp

From equation (7’),

2000 + 27(2.7)2We-= -

&- 0o0024(2m7)2

= 15900 lb~

= 4.42 lb\sec

Detezminatlon of TE:

19

From equattons (2) and (3),

Tg [ -80 + 22(&”f]= Tg30 + 0.8 Te

From fi~re 18, at a fuel-air ratio of 0.107, read

%~c = 082Q T’

For Armv summer air at sna level,

Te = Ta

= 100° F

Tg = [882 + 008 100 - 80 + 22(2.7)9

= 1026° 1?

Computation of head temperature:

The ratio of temperature differentials % - ~’a la~

the ordinate.

= (T[,x Ordin~t~) + Ta = (1C26 x ~dinate) + 100

1 + Ordinate 1 + OrcUnate(9)

For Army summer alr at sea level,

a = ‘a= 00922

The column numbers used in the following table referto;

1. Assumed values of ccollng-air pressure dro~

2. Computed We~’7~/o.bp “

3. Or~.inatefrom fl~lre 17

4. Average ~ (emboddad thermocouples) ccmpu ted byequation (9)

5. .HottmstY.ead-embedded-thermocouple,tgl:lperat’~refromcolumn 4 and f’iCvLre21

1 I 2

204~c1: 1.24018 .i32524 .62030 ,4CJ5

3 I 4 I 5

Ordinate,

‘h - ‘a”Tg–-1

0.761m603.531.462,449

prassure drop in figure 32. Thts problem has bo~n s@li-flad by ignortnq tke adiabatfc temperature l~is~due taflight spasd. For a~>~lication at raascnably great air-speed, account must be taken cf t!’?.sadiG3atlc te~pe.vaturenise of th9 cooll.ng air, wYI?.cF.must ba r.ddad to :;%.es$.c-cifled air tempertitura. Tll(30p51?Etl”~ COil(?lt~.0?13ChfiCenfor this problem ccrres~:ond closaly to conditions thatmight exist at t~ke-off. It cm be seen f~or flqure W?.that, with a spark-plu~-gasket iexperature limit of 50(1°F,a mininurn pi’essur~ drop cf 2.1iil~h.~s~f’water is requiredfor coolin~ the hottast bead.

Langley Memorial Aeronautical. LaboratoryNational Advisory Comiiittes for Ae~onautlcs

I..—. .. .

NACA ACR No, L4F06

REFERENCES-.,... . ....-... .....-. ----- ..,

1. Valentine, E. Floyd: PreliminaryDlreoted”tiward improvement ofNACA ARR, April 1942.

. .2. Pinkel. BenHamIn. and Ellerbrock.

21

.,.,. .

Investigationthe NACA Cowltng.

Herman H.. Jr.:Corfislat~on ok Cooling Data ffioman Air=~oo16dC~llnder and Several Lhllticyilndei’Engines.HACA Rep. No. 693, 1940.

3. ScheT, Oscar W., Pinkel, BenJamIn, and Ellerbrock,Herman H., ,Tr.: Ccrroction of Temperatures ofAir-Cool.ed SnSino Cylindern for Variation inEhgine and CoolinC Conditions. NACA Rep. ]{0. 645,1938 c

5. Pye, D. R.: Tile Internal Combustion En~?.ne. vol. 11.The Aero-Engine. C1.ai”endonI’re3s (Oxford), 1S34,?. 271.

—

NACA ACR No. L4F06 22

-

&

,

NATIONAL ADVISORYTABLE I COMMITTEE FOR AERONAUTICS

ENGINE-COOLINGCORRELATIONDATA - (HWERAL

Engine Charge-~e 1 Pwl- CarburetorT Cooling-TestRun bhp alr flow atr temperature~ ATg

::;;: airflow U@lr)rmtlo (OF) (“p) (Ol?)(lb/hr)

flow(lb/see)

Tests with constantl’uel-airratio

24o24024o~

21+024o24o24o24o24o24o24o24o240

241241241241241

2422422422&J242242a242242242242242

244244244244a244244

1100 21201100 21201100 21201100 21201100 21201100 21201100 21201100 21201100 21201100 21201100 21201100 21201100 21201100 21201100 2120

600 2120800 2120990 21201200 2120600 2120

804079 3Z79 7

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7069

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Teats with varying fuel-air ratio

212021202120212021202120212021202120212021202120

21202120212021201749

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------------------------------------------------

----------------------------

—.

NACA ACR No. L41’06

NATIONAL ADVISORYTABLE II

COMWT7EE FOR AIRONNJTICSENGINE-COOLINGCORRECTION DATA - CYLINDER HEADS

‘6~ ‘6 ‘h ‘h - ‘awal .11! C$aAP ~eI.76

Test Run — .

(“~) (%) ( %?)( inne:; —

‘g - ‘hwe UaAP

Tests with constant fuel-air ratio

21& ; J11 4 1223 331 0:Zk 57:: 43.0 0.096

$ i ::4 :: “!! :~g #:; $:$! !:5

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59.2 4.2 ● 109

Tests with varyfngf’uel-alrratio

0.309 ---- 111.7 0.159.303 ----

?1 ●0 .151

x.30 ---- ;4.9 .155

:~?8 :::: 14:ii● 157

1131 1210 366 .17210ZL 1191 350 ●334 ---- ; lo

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1180 1260 3711

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~ : 880 940 337 .429 ---- f:; .48&

1:;2975 30

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2 ?.32 ~~~~

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:: 3904 356 : 99 ~~~~ 13.9 .701

23

——.

NACA ACR No. L4F06 24

NATIONAL ADVISORYTABLE 111 COMMITTEE FOR AERONAUTICS.,.

ENGINE-COOLING CORRELATION DATA - CYLINDER BASES

~al.15

we

Tests with constant fuel-air ratio

0.121.139.167.200

:;gz.500.159.303

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Fmf of frupt cykv Si& CFFI=W c=@’nu@r

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NACA ACR No. L4F06 Fig. 13

.. . .. .— .—.

Frotmof front cylhdef Side of rearcylinder

A/) = Pressure C - %essvre D

A/q/qc

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COMMITTEE FOR AtRONAUllCSI I I I

00 4 ,8 /.2 . 16 20 2.4 2L3 32

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COMMITTEE FOR AERONAUTICS

5 8 /0 /5 20 3oMm

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Y- variation of (~ - Z- jj ‘~~~’t$ :co~~g - airpressure drop, F&eChary e-air flow, 7750 pouncii per> hour.Cy#nder head’.

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~ -Z&

~f-~h .30NATIONAL ADVISORYB

COMMITIEE FOR AERONAUTICS

4>000 6(M9 tptw K)oooCharge - air flo W, lb / AP

figure /6. -variation of(~-~)[~-~)with charge-wr f/ow; ~4 ej - air n? f;o~ O. 0 8; “flq+31/42 inches of wate r. Cylinder /7eads,

NACA ACR No. L4F06 Fig. 17’

.50

.40

.30

.20

COMMITTEE FOR AERONAUTICS

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.

,

NACA ACR No. L4F06 Fig. 18

.,

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figure /8. ‘Vdr;dfionofmectt7 G3ffectivegm fempmdfure~with fuel-air rdio, ~ylih&r heeds.

1

NACA ACR No. L4F06

,..,

,

,20~ I t 1 1 I I I I I

NATIONAl ADVISORYCOMMWH FOR AERONAUTICS

cowLin--f/dp posl’+ion

A Fuljope~~ Fall closed~ Vclriec( settlhg

30 40 60 60 /00

C oohngu if fl’o w, W&, lb/see

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NACA” ACR No. L4F06 Fig. 20

.. .—

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/0 /5 20 30 405060

NATIONAL ADVISORYCOMMITIEE FOR AERONAUTICS

~igut e 20. – Cooling corre!utioh b~ed on c o&’1”r7g-

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NACA ACR No. L4F06 Fig. 21

500.

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NACA ACR No. L4F06

.

Figs . 22,23

6 8 /0 /5 2a a

%‘) ‘h-“%KoNAL mmofwCOMMllTEE FOR AERONAUTl&S

Figure 22.- lAr~4tim Of (6 -72)Z~ -~) with c00\ln9-oir press u~e drop. Fuel-airratio , 0.08 ; Charge -oip flow,,

7750 pou~ds pep hoLL~Cylinder bases.

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ZL ‘+0~-T6

,30 NATIONAL ADVISORY

COMMITTEE FOR AERONAU11C5+000 kjooo @OO }qom

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NACA ACR No. L4F06 Fig. 24

./0 ./5 .20 .30 .40 ,4

NAnoNAlAOVISORYCOMMITTEE FOR AERONAUTICS

~~~7, Ob per secf~in water4

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NACA ACR No. L4F06 Fig. 25

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COMMlllEE FORAERONAUTICS

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NACA ACR No. L4Ff)6 Fig. 28

— .,.. .,

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