18 Brayton Cycle-jet Engine

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Last Rev.: 17 JUL 08 BRAYTON CYCLEJET ENGINE : MIME 3470 Pae 1

Grading Sheet~~~~~~~~~~~~~~

MIME 3470Thermal Science Laboratory

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Experiment !

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St*dent+, 'ame+ - Section./&I'TS S(E T&T$L

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Last Rev.: 17 JUL 08 BRAYTON CYCLEJET ENGINE : MIME 3470 Pae !

MIME 3470Thermal Science Laboratory

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Experiment !

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EB/E#IME'TTIME-$TEA TIME5 $TE~~~~~~~~~~~~~~

&")E(TI?ESof this experiment are to:1. Understand the basic operation of a Brayton cycle1.

2. Determine the performance (efficiencies) of an actual turbinecomponents and the cycle.

;ig*re "a+ic "rayton (ycle Model oC a Generic Ga+ T*rbine

TE%

A simple gas turbine is comprised of three manmade componentsand one implied component !hen considering it as a closed cycle

(see"igure1). #he implied component$the lo!er heat exchanger

of the figure operating bet!een %tates & and 1$!ill be discussedlater but is added !hen considering the gas turbine as a closed'

ideal cycle. #he three manmade components are1. (ompre++orlo!pressure (ambient) air of %tate 1 is

compressed to %tate 2.

2. (omb*+torfuel is added to the compressed air and ignited.. T*rbinethe hot combustion gasesexpand through andproduce

!or*bytheturbine' turbW .+artofthis!or*isusedtodri,ethe

compressor' compW .#henetoutputted!or*oftheentirecycle'

cycleW 'isshaft!or*andcanbeusedtopo!ermachineryi.e.'

generatorsorhelicopters.Any*ineticenergyoftheexhaustgases

at%tate&isconsideredlostenergy in thiscase.-o!e,er' ifagas

turbineisusedasajetengine'thenthrustisthedesiredoutputandustenough!or*isproducedbytheturbinetodri,ethecompres

sor andproduce any needed auxiliarypo!er. #hen the exhaust

gases are expanded through a no//le to create a high,elocityflo!'i.e.'thrust.

#oanaly/e thecycle' !eneedtoe,aluate allthestatesascompletely

aspossible. #he Brayton airstandard model2 is ,ery useful for this

1 0n uropean literature' this is called the oule cycle.2 air


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de,elopmental effort' efficiencies of 89 to 9; can no! beachie,ed for the turbine and compressor components.

(old $ir


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#he irre,ersibilities present in the real process can be representedby introducing the compressor isentropicefficiency'

( )( )

12

12

hh

hh

w

w

a

s

acomp

scomp

isencomp

== 8!9

!here the subscriptssand isenboth refer to the isentropic process

and the subscript arefers to the actual process.

Combustor


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Last Rev.: 17 JUL 08 BRAYTON CYCLEJET ENGINE : MIME 3470 Pae

con,erting thermal energy into *inetic energy instead of its desiredob of generating shaftpo!er. %o !e do not !ant to increase the

!or*ing fluidEs ,elocity through the turbine. 4n the other hand' theob of a no//le is to con,ert thermal energy to thrust energy i.e.'

,elocity.

(ycle ECCiciency Cor a )et Engine

#hermodynamic efficiency' th' is defined as

( ).nergyInput/ostsThat.nergy

0utput.nergy1esired

th = 879

#he reader !ill remember that gas turbines are used for t!o different functions. #he first is !here shaft po!er is needed to propel

an aircraft or a fast boat or to dri,e an electric generator. 0n such

cases' the turbine is designed to absorb as much of the energyfrom the exhaust gases as possible. %ome of this energy is used to

dri,e the compressor and the rest is net shaft !or* for the cycle'

cycleW .Inthisusage'thethermodynamicefficiency for the

cycle is

( ) ( )( )a

aa

in

compturb

in

cycleth

hh

hhhh

(

ww

Q

W

2)

12&)

=

==

8!9#he second use of a gas turbine is as a et engine !here the desiredoutput is thrust$i.e.' a high gas ,elocity at %tation C' !hich is

no//le exit in "igure . #he thermodynamic efficiency in this case

is expressed as

( )( )( )a

aao

a

a

in

thrustth

hh

hh

hh

V

Q

W

2

CC

2

2C 2

=

==-

8H9

!here hoCa & actual total enthalpy at %tation C' and

hCa & actual enthalpy at %tation C.

;ig*re T*rbine and 'ole and $++ociated (ontrol ?ol*me

Kememberthatinthisexperiment'!emeasurethetotalorstagnation

temperatureandpressureat%tations2'&andCandstatic pressureand

total temperature at %tation . "urther'because of the small flo!,elocities at%tations2''and&'thestagnation,aluesareessentially

the same as the static ,alues. #hus' !e only ha,e to determine hCa

from the stagnation ,alue hoCaJ f(ToCa).

;ig*re 7h-s8Mollier9 iagram Cor State 1

e !ill assumethat the increase in pressure bet!een %tates Caand oCais due to an isentropic compression as sho!n in "igure ?.

Aet engine on a real aircraft !ould ha,e as desired outputted!or*both thrust and shaft !or* to run' say' an electric generator to

po!er a,ionics.

Lno!ingpoCa' pCa' and ToCa' !e can sol,e for TCausing 3uation

29 and using a root sol,er as !e did !ith 3uation ?

( )

==

a

aoT

T

pp

pR

T

dTTcs

ao

aC

CC

C

9 ln 8D09


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and acti,ate fuel flo!. #he %K9 engineEs fuel system is ,erysimilar to largescale engines$fuel atomi/ation ,ia return flo!

highpressure no//les that allo! operation !ith a !ide ,ariety of*erosene based li3uid fuels (e.g.' diesel' et A' +& through 8).

;ig*re HMiniLab )et Engine and Experimental Set*p

Engine Components and Measurement Locations

#he engine consists of a single stage radial compressor' a counter

flo! annular combustor and a single stage axial turbine !hich

directs the combustion products into a con,erging no//le forfurther expansion. Details of the engine may be ,ie!ed from the

Ocuta!ayE pro,ided in "igure 19.

Instrumentation,DataAcquisition,andDataImport toMathcad

#he sensors are routed to a central access panel and interfaced

!ith data ac3uisition hard!are and soft!are from et

T&%'()e O&t>et N"??>e E,(t


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#he "ile "ormat should be #ext. #he second field contains the

file path name relati,e to the 7 Directory' i.e.' c:RQQ.

. 7lic*


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&. %lo!ly open the throttle. a*e sure that you allo! the enginetime to reach steady state by monitoring the digital engine rpm

indicator on the panel. #he reading fluctuates some!hat so useyour udgment.

C. #a*e data at different engine speeds. Fou !ill use the data to

studyho!cycleandcomponentefficiencies change!ithspeed.. Afteryouaredoneta*ingdata'turnoffthefuelflo!s!itch first.

?. #he data !ill be stored in MabP0 files (Q.l,m) !hich can

be read by athcad.

$T$ $'$L%SIS #E/T

1. "irst' read your data files and plot all 11 data ,alues (C

pressures' C temperatures' and rpms vs. time) on one plot$similar to that sho!n belo!.

2. "rom this plot' select three points in time !here you considerthe gas turbine to be operating at steady state. #hen determine

the indices of the data ,ectors corresponding to these times."or the example plot abo,e' the first steadystate time chosen

!as Csec. 0n the pre,ious column' a time ,ector of t23 !as

established. #he student needs to find (by trial and error) !hatindex of the ,ector corresponds to aboutCsec(or !hat e,er

time the student chooses from his or her data).

. "or

the

steadystateoperating

conditions'

calculate

compressor isentropic efficiency' turbine isentropic effici

ency' actual thermodynamic efficiency (based on thrust)'

and the ideal Brayton cycle thermodynamic efficiency

based on thrust for the et engine. "or the referencetemperature in computing enthalpy' use Tref J 2?.1C#.

&.4nonegraph'plot( ) isencomp vs.rpm' ( ) isenturb vs.rpm'

th vs. rpmand( ) isenth vs.rpmfor the steadystateconditions.

; TE IS(6SSI&'

1. -o! do the compressor and turbine efficiencies affect the

cycle efficiencyI2. -o! does the actual cycle efficiency compare !ith the ideal

Brayton cycle efficiencyI

#E;E#E'(ES1. #urbine #echnologies' Mtd.' Brayton 7ycleet ngine xperi

ment' http#.turinetechnologies.co"&"inila&Technical apers&


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E#E $T$5 ($L(6L$TI&'S5 and #ES6LTS

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IS(6SSI&' &; #ES6LTS

1. -o! do the compressor and turbine efficiencies affect the

cycle efficiencyI5nswer6

2. -o! does the actual cycle efficiency compare !ith the ideal

Brayton cycle efficiencyI

5nswer6

(&'(L6SI&'S


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Last Rev.: 17 JUL 08 BRAYTON CYCLEJET ENGINE : MIME 3470 Pae 1!

$//E'I(ES

$//E'IB $ GEGE"$ILE%"#$%T&'

George "ailey "raytonb. 7 0ctober 3879 /ompton Rhode Island

d. 3: 1ecember 38; he #oul! #ork on the i!ea for 1 yearsefore receivinga patenton it in1'2 for the F+ea!yotorG gasengine.Theatent/ffice i!entifies this,2cycleengineasahotairengine that ran@uietly#ithkerosene.?raytonHsengine#asan interestingone. tuse! t#ocylin!ers,connecte!,#ith thepistonsrunning inoppositephase./ne#astheco"pression cylin!er, #hich co"presse! the fuelair "iEture to a so"e#hat higherpressurethanthepressure inthepo#ercylin!er.ntro!ucingthene#principleof fuel inCection, it pu"pe! the co"ustile "iEture into the po#er cylin!er,#here it#ascontinuouslyignite!an!urne!!uringthepo#erstroke,keepingthepressureupinthecylin!erasthepiston#as!isplace!,thusacco"plishing#orkperunitoffuel.8o#ever,"uchoftheefficiency gaine!ythis"etho!#aslost!uetothelackofana!e@uate"etho!ofco"pressingthefuel"iEturepriorto ignition. Thepo#er cylin!er, operating ataslightly lo#erpressure than theco"pressioncylin!er,#as@uiteait larger.(lthoughthisengine#asnotverysuccessful, it #as consi!ere! the first safe an! practical oil engine.Theseengines#ereco""erciallyavailalegasoroilurningFhotairG!esignsfro"#hichthe?rayton,orisoaricco"ustion,cycleoriginate!.

(gasturine,ifyouthinkaoutit,operates"uchthesa"e#ay.Thisconstantpressureco"ustioncycleiskno#ny engineersasthe?raytoncycle,thoughfe# coul! !ra# a picture of a ?rayton engine.

(nothersourcereports9eorge?ailey?rayton#asaninventorofengines.8econstructe!anu"erof!ifferentpatternsoftheseengines,so"eof#hichheputintos"alloatsorlaunches>they#erethepri"itivenaphthalaunchesno#ingeneraluse.roalythe"osthighlyfinishe!engineheeveruilt#assenttothe-entennialat hila!elphia,after#ar!s itrantheshop onotterStreet,rovi!ence,+,an! laterit#assenttoSaylesH?leachery>heinvente!aneyeletan! rivet"achine, Thepatents ofthese"achines#ereproalythe"ostre"unerativeofanyheeverotaine!,nettinghi"nearlyfiftythousan! !ollars.8e#entto0nglan!on usinessin/ct.,142,an!#hilethere!ie!>hiso!y#asroughtho"ein143.8isho"e#as?oston>hisfa"ilystillresi!esthere.I?irth 134, 0ast 9reen#ich, Kent, +ho!e slan!Death ?et /ct 142 an! 143, ee!s, :est orkshire,

0nglan!7ather :illia" 8. ?raytonother inerva ?aileyarrie! +hon!a . Dean, 23 /ct 162 n rovi!ence, +Daughter avelle -lifton ?rayton

EvolutionoftheInternal-CombustionEngine?raytonLsengine#as!isplaye!atthe1'6hila!elphia-entennial0Ehiition.

(lthough "ore i"pressive stea" engines #ere !isplaye!, ?raytonLs enginepointe! to the future.The/tto=-o"panyengine, patente! in 1'6#asnotrea!yinti"etoe!isplaye!athila!elphia./ttoLsengineforfirstti"eplace!internalco"ustiononasoun!lyco"petitivefooting#ithstea" po#er.t#ason!isplayinarisin1'.nspire! y?raytonLs "a""oth internalco"ustionengineat the-entennial0Eposition,9eorge?.Sel!on$inventoran!la#yer,161422%egan#orkingonas"aller lighterversion,succee!ingy1' inpro!ucingaonecylin!er,28, 3'* poun! version #hich feature! an enclose! crankshaftMthe F+oa!0ngineG. 8e file! for a patent in 1'4MnotCust for the engine ut the entireconceptofanauto"oile.Through legal"aneuvers,this#asgrante! in145Mpoise! to reap royalties fro" the fle!gling("erican auto in!ustry. 9eorgeSel!en, !espite never actually pro!ucing a #orking "o!el of an auto"oile,ha!acre!ileclai"tohavepatente!theauto"oile.The first person to eEperi"ent #ith an internalco"ustion engine #as theDutch physicist -hristian 8uygens, aout 16*. ?ut no effective gasolinepo#ere! engine #as !evelope! until 154, #hen the 7rench engineer J. J.Ntienne enoir uilt a !ouleacting, sparkignition engine that coul! eoperate!continuously. n162(lphonse?eau!e+ochas,a7renchscientist,patente! ut !i! not uil! a fourstroke engine> siEteen years later, #hen;ikolaus(./ttouiltasuccessfulfourstrokeengine, iteca"ekno#nastheF/ttocycle.GThefirstsuccessfult#ostrokeengine#asco"plete!inthesa"eyearySirDougal!-lerk,inafor"#hich$si"plifie!so"e#hatyJosephDayin 141% re"ains in use to!ay. 9eorge ?rayton, an("erican engineer, ha!!evelope!a t#ostrokekeroseneengine in1'3,ut it#as too largean! tooslo#toeco""erciallysuccessful.n159ottlieDai"lerconstructe!#hatisgenerally recogniAe!as theprototypeof the"o!erngasengines"allan!fast, #ith a vertical cylin!er, it use! gasoline inCecte! through a caruretor. n14 Dai"ler intro!uce! a fourstroke engine #ith "ushroo"shape! valves

B%at")Ds Rea M"t"%0EhiitTitle ?rayton,9eo.?.,hila!elphia,a.,0EhiitO54*,

achinery 8all,?l!g. O2.9eorge ?. ?raytonHs hy!rocaron +ea!y

otor engine.-entennial hotographic -o. & -entennial 0Ehiition Digital -ollection

http&&gen#e.#hipple.org&!**1&5526'.ht"lhttp&&li###.lirary.phila.gov&-en-ol&ce!ci"gvie#.tafP-0D-;o)c*121* -ulp, John S., .D., http#.atis.net&stationaryengine&!igest&v*3.n5*2

http&&i"artineA.etsin.up".es&k3&c1'&o#er.ht" http#.as"e.org&history&rochures&h135.p!f

http#.nation"aster.co"&encyclope!ia&9eorge?.Sel!enhttp&&personal#es.oaklan!.e!u&Qlei!el&S(0B(0+B4'**6.p!f

http#.infoplease.co"&ce6&sci&(*562.ht"l http#.as"e.org&history&iography.ht"lO?rayton

http#.cretivenergy.co"&rayton.ht"l http#.h#.ac.uk&"ec:::&researchh"&ter"2B2***&part2.D7

http#."ariti"e.org&fleetsu&!iesel&chap1.ht"

an!t#ocylin!ersarrange!ina,havinga"uchhigherpo#erto#eightratio>#iththeeEceptionofelectricstarting,#hich#oul!noteintro!uce!until142,"ost "o!ern gasoline engines are !escen!e! fro" Dai"lerHs engines.EvolutionoftheTurbineEngineJohn ?arer receive! the first patent for a turineengine in 0nglan! in 1'41.8is!esign#as forpropellinga Hhorselesscarriage.HThe turine#as !esigne!#ith a chain!riven, reciprocating type of co"pressor. t ha! a co"pressor,aco"ustion cha"er, an! a turine. The gasturine engine #as first

successfullyteste!y 7.:hittlein143',an!firstapplie!ythe8einkel(ircraft-o"panyin1434.To!ay,gasturinesareuse!ypracticallyallaircrafteEcepts"aller ones, y "any fast oats, an! increasingly een use! for stationarypo#ergeneration,particularly#henothpo#eran!heatareofinterest.
http://genweb.whipple.org/d0041/I55267.htmlhttp://libwww.library.phila.gov/CenCol/cedcimgview.taf?CEDCNo=c012140http://www.atis.net/stationary-engine/digest/v03.n502http://imartinez.etsin.upm.es/bk3/c17/Power.htmhttp://www.asme.org/history/brochures/h135.pdfhttp://www.nationmaster.com/encyclopedia/George-B.-Seldenhttp://personalwebs.oakland.edu/~leidel/SAE_PAPER_970068.pdfhttp://www.infoplease.com/ce6/sci/A0858862.htmlhttp://www.asme.org/history/biography.html#Braytonhttp://www.cre8tivenergy.com/brayton.htmlhttp://www.hw.ac.uk/mecWWW/research/whm/term2_2000/part2.PDFhttp://www.maritime.org/fleetsub/diesel/chap1.htmhttp://www.maritime.org/fleetsub/diesel/chap1.htmhttp://www.hw.ac.uk/mecWWW/research/whm/term2_2000/part2.PDFhttp://www.cre8tivenergy.com/brayton.htmlhttp://www.asme.org/history/biography.html#Braytonhttp://www.infoplease.com/ce6/sci/A0858862.htmlhttp://personalwebs.oakland.edu/~leidel/SAE_PAPER_970068.pdfhttp://www.nationmaster.com/encyclopedia/George-B.-Seldenhttp://www.asme.org/history/brochures/h135.pdfhttp://imartinez.etsin.upm.es/bk3/c17/Power.htmhttp://www.atis.net/stationary-engine/digest/v03.n502http://libwww.library.phila.gov/CenCol/cedcimgview.taf?CEDCNo=c012140http://genweb.whipple.org/d0041/I55267.html


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18 Brayton Cycle-jet Engine

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