Exergy analysis of a turbofan engine for an unmanned aerial vehicle during a surveillance mission

14 Pages·2015·1.607 MB·English

by  Yasin Sohret, Ali Dinc, T. Hikmet Karakoc

Energy93(2015)716e729
ContentslistsavailableatScienceDirect
Energy
journal homepage: www.elsevier.com/locate/energy
Exergy analysis of a turbofan engine for an unmanned aerial vehicle
during a surveillance mission
Yasin S¸o€hret a,*, Ali Dinç b, T. Hikmet Karakoçc
aGraduateSchoolofSciences,AnadoluUniversity,TR-26470,Eskis¸ehir,Turkey
bTusasEngineIndustriesInc.,TR-26003,Eskis¸ehir,Turkey
cFacultyofAeronauticsandAstronautics,AnadoluUniversity,TR-26470,Eskis¸ehir,Turkey
a r t i c l e i n f o a b s t r a c t
Articlehistory: Inthisstudy,anexergyanalysisofaturbofanengine,beingthemainpowerunitofanUAV(unmanned
Received8June2015 aerialvehicle)overthecourseofasurveillancemissionflight,ispresented.Inthisframework,anengine
Receivedinrevisedform modelisfirstlydeveloped,baseduponenginedesignparametersandconditionsusingagenuinecode.
8September2015
Next,theexergyanalysisisperformedaccordingtothermodynamiclaws.Attheendofthestudy,the
Accepted17September2015 combustion chamber is identified as the most irreversible component of the engine, while the high
Availableonlinexxx
pressureturbineandcompressorareidentifiedasthemostefficientcomponentsthroughouttheflight.
Theminimumexergyefficiencyis58.24%forthecombustionchamberattheendoftheingressflight
Keywords:
phase,whilethemaximumexergyefficiencyisfoundtobe99.09%forthehighpressureturbineatthe
Aircraftengine
Cycleanalysis start of the ingress flight phase and landing loiter. The highest exergy destructionwithin the engine
Gasturbine occurs at landing loiter, take-off and start of climb, with rates of 16998.768 kW,16820.317 kW and
Exergyanalysis 16564.378kWrespectively.
Turbofan ©2015ElsevierLtd.Allrightsreserved.
UAV
1. Introduction second laws of thermodynamics, pays attention to the quality of
energyconsumptionandconversionwithinasysteminadditionto
Asaresultoftechnologicaldevelopmentandrapidadvancesin thequantity.Therefore,itleadsustounderstandtheirreversibility
engineering sciences and industry, world energy demand in the andlosswithintheexaminedsystem[3e5].Forthispurpose,many
21st century is ever increasing. Recent reports by well-regarded studieshavebeenpresentedintheliteraturefortheevaluationof
institutions[1,2]revealthatfossilfuelsarestillthemostcommon various energy systems e.g. power plants, engines, heating and
energyresources,ratherthanrenewableenergyresources.There- coolingsystemsandsuchlike[6e15].
fore, there is pressure to develop more efficient energy system The transportation sector accounts for approximately 25% of
designs,andtoutilizeandsustainenergymoreefficiently.Atthis energyconsumptionworldwide[1].Airtransportationhasgrown
point, thermal engineering, commonly referred to energy engi- in importance thanks to the time it saves us in daily life. Corre-
neering,playsavitalrole.Exergyinparticular,isaprominenttoolin spondingly,thenumberofaircraftinservicehasincreasedandthe
thisfieldofengineeringprovidingbenefits,suchastheevaluation contribution of air transportation to energy utilization has
andoptimizationofenergysystems.Exergyanalysiscomprisesthe increased more than expected. Thus, aircraft propulsion systems,
firstandsecondlawsofthermodynamics.Thefirstlawdealswith especially gas turbine engines, have caught the attention of re-
energyconservationandformschangesofenergywithinthesys- searchersdealingwiththermalengineering.However,anumberof
tem.Thus,itenablesustounderstandtheconversionrateofenergy early research papers emphasize the need to use exergy in the
into another form, while the second law of thermodynamics ex- courseofaircraftpropulsionsystemsdevelopmentprocessesasan
plainsthetheoreticallimitationsofasystemunderactualoperating optimizinganddesigntooltoachievemoreefficientandenviron-
conditions.Exergyanalysis,whichbenefitsfromboththefirstand mentallyfriendlysystems[16,17].Withrespecttothis,numerous
aircraft gas turbine engines have been investigated using exergy.
Turgut et al. [18] contributed to the literature by examining a
turbofanengineatsealevelconditionwiththeaidofexergy.The
* Correspondingauthor.Tel.:þ905347661416. fanandhotsectionnozzlewerefoundtobethemostirreversible
E-mailaddress:[email protected](Y.S¸o€hret).
http://dx.doi.org/10.1016/j.energy.2015.09.081
0360-5442/©2015ElsevierLtd.Allrightsreserved.
Y.S¸o€hretetal./Energy93(2015)716e729 717
Nomenclature F exergeticfuel
f fuel
E_ exergyrate(kW) flight flight
_ gas exhaustgas
IP improvementpotentialrate(kW)
_ i enginestationnumber
Q heattransferrate(kW)
in inletsection
R universalgasconstant
k kthingredientofthemixture
_
W workrateorpower(kW) L loss
cp specificheatcapacityunderconstantpressure mix mixture
(kJkg(cid:3)1K(cid:3)1) out outletsection
e_ specificexergyrate(kWkg(cid:3)1) P exergeticproduct
m_ massflowrate(kgs(cid:3)1)
F thrust(kN) Superscripts
FAR fuel-airratio CH chemical
h enthalpy(kJkg(cid:3)1) KN kinetic
LHV lowerheatingvalue(kJkg(cid:3)1) PH physical
M molarweight(kgkmol(cid:3)1) PT potential
N molenumber(mole)
NGV nozzleguidevanes Abbreviations
P pressure(kPa) AC aircompressor
T temperature(K) CC combustionchamber
TSFC thrustspecificfuelconsumption(kgkN(cid:3)1h(cid:3)1) HPT highpressureturbine
V speed(ms(cid:3)1) LPT lowpressureturbine
g gravity(ms(cid:3)2) TFE turbofanengine
x molefraction UAV unmannedaerialvehicle
y variable
w uncertainty Greekletters
z altitudefromreference(m) d fueldepletionrate
ε exergyefficiency(%)
Subscripts x productivitylack
0 deadstateconditions c relativeirreversibility(%)
air specificationofair
D destruction
components of the engine as a result of the study. In Ref. [19], performedinthisstudy.InRef.[24]theperformanceofaJ85-GE-21
fundamentalexergyrelationshipswereintroducedtoevaluatethe turbojet engine with afterburner was evaluated at sea level con-
performance of an aerial vehicle for each phase point of a flight. ditionsand11000maltitudesbasedontheexergyanalysismethod.
Exergy balance equations and entropy functions were developed Adecreaseofexergyefficiency,basedonreducinginletairspeed,
regarding the impact of drag and lift forces on the energy con- wasnotedbytheauthors.Inaddition,thestudyconcludedthatthe
sumption of the propulsion system. Tona et al. [20] present the loss of exergy efficiency was 0.45% with a 1 (cid:2)C temperature
exergyparametersofaturbofanengineinadditiontoaneconomic decrease.Balli[25]presentedtheimpactofanafterburneronthe
evaluation.Withinthisscope,thevariationinexergyefficiencyfor exergetic performance of an experimental turbojet engine. The
each component was obtained at the take-off, climb, cruise, exergy efficiency of the investigated engine was calculated to be
descent,holdingandlandingphasesofaflight.Dependingonthe 29.81%and22.77%formilitaryandafterburnermodes,respectively.
exergyanalysis, researchersalso performeda costanalysis of the A genetic algorithm was developed for the exergy-based optimi-
evaluatedengine.Turan[21]discussestheeffectofcertainengine zationofaturbofanenginebyTaietal.[26].Enginecycleanalysis
designparameters, forexample pressureratio,turbine inlet tem- equationswerecombinedwithanexergyapproachinthiscontext.
peratureandflightMachnumber,ontheexergeticperformanceof A3.3%e11.0%increaseinspecificthrustgenerationwasconfirmed
aturbojetengine.Thisstudymaybeconsideredamilestoneasthe attheexpenseof1.5%e2.3%ofextrafuelconsumptionwiththeaid
firstexergyanalysisofanUAV(unmannedaerialvehicle)applicable ofthermodynamicoptimization.
jetengine.Asaresultofthisstudy,itwasconcludedthattheexergy ExergyanalysesofgasturbineenginesoperatedonUAVs(un-
efficiencyofcomponentsandtheengineimprove,inrelationtoan manned aerial vehicles) are scarce in the literature. Related to
increaseinMachnumber.Anotherpaper[22]revealstheexergetic progressinthisfieldgasturbineenginesusedforUAVsshouldbe
performanceandeconomicaspectsofaCT7-9Cturbopropengine. investigated from the view point of exergy. For this purpose, the
Thecompressor,combustionchamber,gasturbineandpowertur- currentstudyaims tocontribute tothe literature byexamining a
bine components are evaluated within this framework. Balli and turbofanenginewhichisthemainpowerunitofanUAV.Within
Hepbasli [23] conductedan exergyanalysis of another turboprop thisscope,exergyparameters(exergyefficiency,exergydestruction
engine, mostly used for military applications. The engine was rate, improvement potential rate, productivity lack, and fuel
investigated under different operating modes, such as 75% and depletion rate) for each component of the engine are presented
100% loads, military and take-off. The dependence of exergetic basedonobtainedresultsfromanenginemodelforamissionflight.
characteristics of the engine on operating mode was presented. The exergy analysis of the engine is conducted for a typical sur-
Unlike in previous studies, uncertainty analyses were also veillancemissionflightoftheUAV.
718 Y.S¸o€hretetal./Energy93(2015)716e729
2. Modeling developed for modeling the UAV and its engine with regard to
mission flight conditions. In Fig. 2, a flowchart of the UAV and
2.1. UAVandmissionflightdescription turbofanenginemodelingcodeisgiven.Themaincodecomprises
three embedded algorithms for UAV sizing, engine modeling and
UAVsaredefinedasaerialvehiclesthatdonotcarryapilotand performance calculation. Firstly, the main code reads more than
which are operated remotely or autonomously during a mission 100 input parameters from a file. These input parameters can be
flight. Thus, they have numerous military and civil applications, summarizedasfollows:
suchas:aerialphotography;agriculturalpurposeslikecropmoni-
toring and spraying; herd monitoring and driving; coastguard (cid:4) AUAVflightprofileandcapabilityrequirementsoftheaircraft
searchandrescue;coastlineandsea-lanemonitoring;pollutionand (Machnumber,flightaltitude,payloadtobecarried,operation
landmonitoring;surveillanceforillegalimports;fireservices and radius,andsoon.)
forestry; fire detection; shadowing enemy vessels; decoying mis- (cid:4) Aerodynamic data estimations for drag, lift coefficients, wing
siles by the emission of artificial signatures; reconnaissance; sur- loadingandsuchlike.
veillanceofenemyactivity;targetdesignationandmonitoring;and (cid:4) UAVsizingparametersandratios,suchasthrusttoweightratio,
thelocationanddestructionoflandminesandsuchlike[28e32]. fuelweightratiooftheUAV,aspectratio,tiptohubchordlength
Theevaluatedengineinthisstudyisthemainpowerunitofan ratio, thickness to chord ratio of wing, fuselage length to
UAV,similartotheGlobalHawk.TheGlobalHawkisaHALE(high diameterratioandsoon.
altitude long endurance) type UAV developed within the frame- (cid:4) Engine design parameters (selection/limits), such as fan and
workofaprojectbytheUSAirForce,primarilyforreconnaissance compressor pressure ratios, turbine inlet temperature, fan-
and surveillance missions [32e36]. An assumed surveillance compressor-combustor-turbine-exhaust and mechanical effi-
missionflightscenarioisgiveninFig.1fortheevaluatedUAVinthe ciencies, inlet-bypass duct-combustor-jet pipe total pressure
currentstudy.Thephasesofthemissionflightarestart(0),take-off losses,coolingandbleedairratioandsoon.
(0e1),climb(2e3),cruiseclimbingress(4e5),loiter(6e7),egress (cid:4) Empiricaldataandcorrelationsforweightandvolumeestima-
(8e9),descent(9e11)andlanding(11).Accordingtotheassumed tionoftheUAVcomponents,systemsandengine.
missionprofile(flightscenario),atfirsttheenginestartsatpoint0,
theUAVgoesalongtherunwayreachingaspeedofapproximately Afterreadingtheinputdata,theUAVsizingalgorithmcalculates
185km/hatpoint1.Atthistime,theUAVtakesoffandclimbstoan thesizeandweightoftheUAVandtherequiredenginepowerand
altitudeof15,240m(50,000ft).Atpoint3,theclimbphaseends weightthroughiterationsforeachflightpointbasedontheabove
andthecruiseclimbingressphasebeginsatpoint4.Frompoint4to mentioned inputs. Next, the engine modeling algorithms charac-
point 5, the UAV ascends from an altitude of 15,240 m up to terize the engine according to the engine design parameters for
19,812m(65,000ft)altitude,whilecruisingtowardsthefieldtobe meeting the thrust demand of the UAV at each phase of mission
observed.Intheperiodbetweenpoints6and7theUAVconducts flight.Atthenextstep,performancecalculationsaremadeforthe
surveillance(loiter)foraround24h.Afterthis,theUAVegressesthe engineandUAVateachflightpoint.TheISA(InternationalStandard
missionfieldatpoint8anddescendstoanaltitudeof15,240m.At Atmosphere) model is embedded into the code and is used for
point9,theUAVcontinuestodescendandawaits(loiters)landing enginemodelingandperformancecalculationalgorithms.Thecode
atpoint10,dependingonconditions.Finally,theUAVlandsatpoint checks whetheror notthe results are satisfactory. Warning mes-
11andthemissionflightends. sages are generated if any of the following cases occur. Inputs
shouldthenbereviewed:
2.2. ModelingtheAE3007Hturbofanengine
(cid:4) Too low a thrust to balance drag, for the input altitudes
Enginemodelingwasperformedinapreviousstudyconducted (decreasealtitudeorincreaseaircraftthrusttoweightratio)
byDinc[32]accordingtotheparametriccycleanalysisequations (cid:4) Too low an input velocity to produce required lift (increase
explainedinmanytexts[37e40].Parametriccycleanalysisaimsto cruiseorloiterMachnumber)
obtain estimates of performance parameters (thrust and specific (cid:4) Complex numbers in results (check engine and aircraft
fuel consumption) in terms of design limitations (e.g. maximum parameters)
allowable turbine temperature and attainable component effi- (cid:4) Negativenumbersinflighttimesegments,climbrateandsoon
ciencies),flightconditions(ambientpressureandtemperatureand (checkengineandaircraftparameters).
Machnumber)anddesignchoices(e.g.compressorpressureratio
and combustion efficiency). The AE3007H turbofan engine, the Finally,alldetailedresultsarewrittentoafileforuserevalua-
main power of the Global Hawk, is modeled on a genuine code tion.Forotherdesignoptions,ausermaychangetheinputfileand
Fig.1. AnAssumedsurveillancemissionflightscenariooftheevaluatedUAV.
Y.S¸o€hretetal./Energy93(2015)716e729 719
Fig.2. AFlowchartofthegenuinecodedevelopedformodelingtheUAVanditsengine.
runthecodeagain.Inthepresentstudy,agenuinecodeisusedfor X X
modelingtheAE3007Hturbofanengineateachphasepointofthe m_in¼ m_out (1)
surveillance mission flight scenario of the UAV according to the
X h (cid:2) . (cid:3) i
enginestationnumberingthatisshowninFig.3. Q_ (cid:3)W_ þ m_ h þ V2 2 þgz
TheAE3007Hturbofanengineiscomprisedofasinglefan(2-13- X h in in(cid:2) .in (cid:3) ini (2)
2b4u)s,tiaon14c-hsatamgbeehri(g3h1-p4r)e,sasu2r-estcaogmehpirgehssporre(s2s6u-r3e)t,uarnbiannen(u4l1a5rec4o1m6-) (cid:3) m_out houtþ Vo2ut 2 þgzout ¼0
anda3-stagelowpressureturbine(46e48).Anozzle(5e7)isalso Here,m_ notatesmassflowrate,whileQ_,W_,h,V2/2,andgzare
installed after the low pressure turbine for thrust generation. In
heat transfer rate, work rate, enthalpy, kinetic and potential en-
addition,aby-passcanal(13e17)andaby-passnozzle(17e18)are ergiesoftheflow.Anexergybalanceequationasthethirdfunda-
includedintheengine[41].
mentalequationforasteady-statesystemisstatedas[15,43]:
3. Exergyanalysis E_F(cid:3)E_P(cid:3)E_D(cid:3)E_L¼0 (3)
_ _
3.1. Fundamentalconsiderations where EF and EP represent exergy rates of fuel and product
_ _
respectively,whileE andE meanexergydestructionandexergy
D L
Asmentionedearlier,exergyanalysisisanapproachwhichisa lossrateswithinthesystem.Inaddition,exergeticfuelshouldnot
combination of the first and second laws of thermodynamics. In beconfusedwithactualfuels,suchasnaturalgas,coalorkerosene.
this framework, fundamental equations should be written to Thetermfuelinexergyanalysisisusedtodefinealloftheresources
performexergyanalysisofanysystem.Therefore,foranysteady- consumedtogainanexergeticproductfromthesystem.Exergyis
statesystem,massandenergyconservationequationsarewritten considered to consist of physical, chemical, kinetic and potential
respectivelyasfollows[21e23,42e44]: components, neglecting nuclear, magnetic, electrical and surface
tensioneffects.Therefore,thecomponentsofexergyarephysical,
chemical,kineticandpotential[15,23,42e44]:
(cid:2) (cid:3)
E_¼m_ ePHþeCHþeKNþePT (4)
PhysicalexergyorflowexergyisfoundbyRefs.[23,42e44]:
(cid:4) (cid:5)
ePH ¼cpðT(cid:3)T0Þ(cid:3)T0 cplnðT=T0Þ(cid:3)RlnðP=P0Þ (5)
Thechemical exergyofagasmixtureandaliquidfuelcanbe
expressedrespectivelyasfollows[41e43]:
X X
eCH ¼ x eCHþRT x lnx (6)
mix k k 0 k k
eCH ¼gLHV (7.a)
f
Fig.3. ASchematicviewoftheAE3007Hturbofanengine[32].
720 Y.S¸o€hretetal./Energy93(2015)716e729
(cid:6) (cid:7) (cid:4) The bleed and cooling system were assumed to be shut off
g¼1:0401þ0:1728hþ0:0432oþ0:2169s 1(cid:3)2:0628h duringthecourseoftheanalyses.
c c c c (cid:4) Theairwasassumedtobecomposedof75.67%nitrogen,20.35%
(7.b) oxygen,0.0345%carbondioxide,3.03%watervaporand0.8255%
otheringredients[47,48].
Here,xkandRarethemolefractionofeachmixtureingredient
anduniversalgasconstant.Additionally,LHVandgrepresentthe
lowerheatingvalueandchemicalexergyofthefuelinEqs.7.aand
7.b.Kineticandpotentialexergyastwoothercomponentsofexergy
3.3. Exergyanalysisoftheturbofanenginecomponents
areformulatedasfollows[42e44]:
.
Inthissectionofthepaper,theapplicationofgoverningequa-
eKN ¼V2 2 (8)
tions to each component of the turbofan engine is explained
dependingontheassumptionsmade.
ePT ¼gz (9) Massbalance,energybalanceandexergybalanceequationsfor
thefan(F)maybestatedasfollows:
In exergy analysis, exergy efficiency, improvement potential,
fueldepletionrateandproductivitylackarebeneficialindicatorsin m_2¼m_13þm_24 (15)
the evaluation of the exergetic performance of the considered
system. Exergy efficiency is defined as the ratio between exergy (cid:3)W_Fþm_2h2(cid:3)m_13h13(cid:3)m_24h24¼0 (16)
ratesofproductandfuel[15,18,43,45]: (cid:2) (cid:3)
_ W_F(cid:3) E_24þE_13(cid:3)E_2 (cid:3)E_D;F ¼0 (17)
E
ε¼E_P (10) FortheAC(aircompressor)thefollowingequationsmaybeused
F
forexergyanalysis:
Improvement potential is defined as the rate of exergy
destructionminimizationwithinthesystembyvanGool[15,18,46]: m_ ¼m_ (18)
26 3
IP_ ¼E_Dð1(cid:3)εÞ (11) (cid:3)W_ þm_ h (cid:3)m_ h ¼0 (19)
AC 26 26 3 3
Relative exergy destruction rate or relative irreversibility in- (cid:2) (cid:3)
dicates the percentage of exergy destruction within the system W_AC(cid:3) E_3(cid:3)E_26 (cid:3)E_D;AC ¼0 (20)
component:
Intheanalysesofthefanandaircompressor,thespecificheat
_
c¼PED_ (12) capacity of the working fluid air under constant pressure is
E dependentontemperatureandiscalculatedusingEq.(21)[21]:
D
ableFsueulsdtoepcloemtiopnrerhaetnioditshaendoetshterurcetvioalnuraattioenofpeaxrearmgeettiecrfwuehliwchitehnin- cp;air ¼1:04841(cid:3)38130:7619 Tþ9:41503778 T2(cid:3)5:140910031 T3
thesystem[18,23,27,45]: þ7:92981 T4
1014
_
d¼PED_ (13) (21)
EF ThefollowingequationsareusedforexergyanalysisoftheCC
(combustionchamber):
Productivitylackistheratioofexergydestructionratetototal
exergeticproductratewithinthesystem[18,23,27,45]: m_ þm_ ¼m_ (22)
31 f 4
_
E
x¼PDE_P (14) m_31h31þm_fLHVhc¼m_4h4 (23)
(cid:2) (cid:3)
3.2. Assumptions E_4(cid:3) E_31þE_f (cid:3)E_D;CC ¼0 (24)
Atthisstageoftheanalysis,thechemicalexergyofthefueland
Assumptionsmadeinthecurrentstudyareasfollows: fluegasarefoundbyEqs.6,7.aand7.b.Thespecificheatcapacityof
flue gas under constant pressure, dependent on temperature, is
(cid:4) Theenginewasconsideredundersteady-stateconditionsdur-
determinedbyfollowing[49]:
ingthemissionflight.
(cid:4) Theairandcombustiongaseswereassumedtobeperfectgas. P
(cid:4) The fuel was kerosene. The chemical formula of the kerosene cp;gas¼ PcpN;kNMkMk (25)
wasconsideredasC11H21,whilethelowerheatingvalueofthe k k
kerosenewas43370.596kJ/kg. After analyzing the combustion chamber, calculations of HPT
(cid:4) Thecombustionreactionwasconsideredtobecomplete. (highpressureturbine)exergyanalysisareperformedaccordingto
(cid:4) Allthecomponentsoftheenginewereassumedtobeadiabatic followingequations:
andheatlossesweredisregarded.
(cid:4) Kinetic energy, potential energy, kinetic exergy and potential m_ ¼m_ (26)
415 416
exergychangeswithintheenginewereignored.
(cid:4) Chemical exergy of the air was disregarded being so close to (cid:3)W_ þm_ h (cid:3)m_ h ¼0 (27)
0.00value. HPT 415 415 416 416
Y.S¸o€hretetal./Energy93(2015)716e729 721
(cid:2) (cid:3) Therefore,theexergybalancestatementfortheoverallengineis
E_415(cid:3)E_416 (cid:3)W_HPT(cid:3)E_D;HPT ¼0 (28) re-arrangedasfollows:
(cid:2) (cid:3)
Similar formulations can be derived for a LPT (low pressure E_ (cid:3)FV (cid:3)E_ (cid:3) E_ þE_ ¼0 (38)
f flight D 7 18
turbine)asfollows:
Thus,fortheoverallengineEq.(10)isderivedas:
m_ ¼m_ (29)
46 48
(cid:3)W_ þm_ h (cid:3)m_ h ¼0 (30)
LPT 46 46 48 48 FV
(cid:2) (cid:3) εTFE ¼ E_flight (39)
E_46(cid:3)E_48 (cid:3)W_LPT (cid:3)E_D;LPT ¼0 (31) f
Depending on disregarded kinetic and potential energy 4. Resultsanddiscussion
changes within the engine, hot section and by-pass nozzles are
beyondthescopeofthispaper.However;mass,energyandexergy Inthisstudy,aturbofanengineofaUAVwasinvestigatedwith
balanceequationsmaybeexpressedfortheBPC(by-passcanal)as the aid of exergy, based upon data obtained from an engine
follows: modelingstudyforasurveillancemissionflight.Inthissectionof
m_ ¼m_ (32) the paper, the modeling results and the results of the exergy
13 17 analysisarepresentedbelow.
m_ h (cid:3)m_ h ¼0 (33)
13 13 17 17
4.1. Enginemodelingresults
E_13(cid:3)E_17(cid:3)E_D;BPC ¼0 (34) Anenginemodelisdevelopedforamissionflightprofile.More
than 100 input parameters (related to mission profile, UAV and
enginedesigncharacteristics)areinputtedintothemodel.Anen-
gine model is developed foreach phase point of the surveillance
3.4. Exergyanalysisoftheoverallengine
missionflightscenario.InTable1,theobtainedenginecharacter-
istics are summarized for each flight phase point during the sur-
The exergy analysis of the overall engine is conducted in
veillance mission. The assumed parameters for the engine by
accordance with the scheme demonstrated in Fig. 4. Thus, the
genuineenginemodelcodearethrust,flightspeed,inletairmass
exergetic fuel of the engine is considered as the total exergetic
flowrate,fuelflowrate,temperatureandpressurevaluesateach
valueoffuelprovidedtotheenginewhiletheexergeticproductis
engine station as illustrated in Fig. 3. In addition, as a result of
theexergyrateofthrustgeneratedbytheengine.Theexergybal-
comparingthegenuinecodewithcommercialGasTurb11software
ancefortheoverallengineistherebyexpressedasfollows[43]:
[51], deviations (namely errors) of pressures, temperatures, air
E_ (cid:3)E_ (cid:3)E_ (cid:3)E_ ¼0 (35) mass flow rates, fuel mass flow rates at engine stations and
f T D L
generated thrust are found to be 0.20%, 0.09%, 0.58%, 1.66% and
_
Here,E istheexergyrateofthrustandisfoundbyRef.[18]: 0.57%respectively.
T
E_ ¼FV (36) Figs.5and6areplottedtoclearlyseevariationsofpressureand
T flight temperaturewithintheengine.AccordingtoFig.5,anincreasein
_ temperaturevariationatthehighpressureinletandNGV(nozzle
E in Eq. (32) represents the exergy loss rate and it equals the
L guidevanes)outletaresimilar.Ontheotherhand,thetemperature
exergyrateoftheexhaustgas:
atthefanoutlet,compressorinletandoutlet,combustionchamber
E_ ¼E_ þE_ (37) inletandoutletvaryinasimilarmannerdependingontheflight
L 7 18 phasepoint.Dependingonothertemperaturevariationswithinthe
engine, an increase in temperature at the high pressure turbine
outlet,lowpressureturbineoutletandhotsectionnozzleoutletare
approximatelythesame.
Fig.6 demonstrates the pressure variationof the engine sta-
tions with flight phase points. Until the end of the take-off (or
start of climb) phase, pressure variation at every station of the
engine is approximately constant. However, in the period be-
tweenthestartandthecommencementoftheclimbandegress
phases,pressureateachenginestationdecreaseswithapproxi-
matelythesameslopeangle.However,fromtheegressphaseto
the start of landing, pressure at each engine station increases
significantly.
ThevariationofTSFC(thrustspecificfuelconsumption)andFAR
(fuel-air ratio), as performance evaluation parameters of the
aircraft gas turbine engines, is plotted depending on the flight
missionprofileinFig.7.TSFCindicatestheamountoffuelprovided
tothecombustionchamberforthepurposeof1kNthrustgener-
ation by the engine. Fromthis viewpoint, the TSFC of the engine
increasesremarkablyduringthetake-off,climbandegressphases
Fig.4. ASystemdefinitionfortheoverallengineanalysis[50]. ofthemissionflightandpeeksattheendoftheegressphase.The
722 Y.S¸o€hretetal./Energy93(2015)716e729
Table1
Engineperformanceparametersduringthesurveillancemissionflightscenario.
Engineparameter Flightphasepoint
1 2 3 4 5 6 7 8 9 10
T(kN) 29.429 28.472 3.624 3.63 3.376 3.369 1.91 1.913 3.63 29.907
Vflight(kmh(cid:3)1) 185.2 238.0 610.0 635.0 635.0 597.2 597.5 635.0 635.0 161.0
m_f (kgs(cid:3)1) 0.5217 0.5251 0.0961 0.0968 0.1049 0.088 0.050 0.0510 0.0968 0.5205
m_2(kgs(cid:3)1) 115.2 116.2 18.2 18.4 17.2 16.8 9.5 9.7 18.4 114.8
P0(kPa) 103 104 14 15 14 13 8 8 15 103
P2(kPa) 102 103 14 15 14 13 8 8 15 102
P24(kPa) 164 166 23 23 22 21 12 12 23 163
P13(kPa) 164 166 23 23 22 21 12 12 23 163
P17(kPa) 159 161 22 22 21 20 11 11 22 158
P26(kPa) 161 162 23 23 21 21 12 12 23 160
P3(kPa) 2313 2337 325 331 308 300 170 175 331 2304
P31(kPa) 2313 2337 325 331 308 300 170 175 331 2304
P41(kPa) 2243 2267 316 321 299 291 165 169 321 2235
P4(kPa) 2243 2267 316 321 299 291 165 169 321 2235
P415(kPa) 2243 2267 316 321 299 291 165 169 321 2235
P416(kPa) 573 577 105 107 99 97 55 56 107 572
P44(kPa) 573 577 105 107 99 97 55 56 107 572
P46(kPa) 568 571 104 106 98 96 55 56 106 566
P48(kPa) 206 207 48 49 45 45 25 26 49 206
P7(kPa) 204 205 48 48 45 44 25 25 48 204
T0(K) 289 290 231 232 232 230 230 232 232 289
T2(K) 289 290 231 232 232 230 230 232 232 289
T24(K) 336 337 268 269 269 267 267 269 269 336
T13(K) 336 337 268 269 269 267 267 269 269 336
T17(K) 336 337 268 269 269 267 267 269 269 336
T26(K) 336 337 268 269 269 267 267 269 269 336
T3(K) 782 785 628 631 631 627 627 631 631 782
T31(K) 782 785 628 631 631 627 627 631 631 782
T41(K) 1571 1572 1559 1560 1560 1559 1559 1560 1560 1571
T415(K) 1529 1529 1510 1511 1511 1510 1510 1511 1511 1529
T416(K) 1156 1155 1210 1209 1209 1211 1211 1209 1209 1156
T44(K) 1156 1155 1210 1209 1209 1211 1211 1209 1209 1156
T46(K) 1156 1155 1210 1209 1209 1211 1211 1209 1209 1156
T48(K) 928 927 1028 1026 1026 1029 1029 1026 1026 928
T5(K) 916 915 1006 1004 1004 1007 1007 1004 1004 917
T7(K) 916 915 1006 1004 1004 1007 1007 1004 1004 917
FAR is the burnt fuel mass within the combustion chamber per easycomparison.AccordingtoFig.8,thehighestexergydestruction
combustionairmass.AsseeninFig.7,variationsoftheTSFCand occurs within combustion chamber at every flight phase point,
FARareapproximatelythesameoverthecourseofthesurveillance whilethehighpressureturbinehasminimumirreversibility.Fora
missionflight. detailed assessment of the component based exergy analysis re-
sults, exergy parametersof each engine componentare givenfor
4.2. Resultsobtainedfromexergyanalysisoftheengine eachflightphasepointseparatelyinfollowingtables.
components AccordingtoTable2,whichisgivenforflightphasepoint1,the
most irreversible component of the engine is the combustion
Anoverviewofmajorexergyparametersofeachcomponentis chamberwitharelativeexergydestructionrateof88.29%,whereas
plottedlogarithmicallyscaledinFig.8forbetterunderstandingand therelativeexergydestructionrateofthehighpressureturbineis
lowestwithavalueof0.88%.Theexergydestructionratesofthefan,
compressor, combustion chamber, high pressure turbine, low
pressure turbine and by-pass canal are 501.088 kW, 440.760 kW,
14381.012kW,143.650kW,575.459kWand244.837kWrespec-
tively. Depending on the highest exergy destruction rate, the
combustionchamberhastheminimumexergyefficiencyofallthe
components.Exergyefficienciesofthefan,compressor,combustion
chamber,highpressureturbine,lowpressureturbineandby-pass
canal are 90.78%, 95.22%, 64.60%, 98.55%, 90.97% and 93.89%
respectively.
Theexergyparametersoftheenginecomponentsatflightphase
point2aresummarizedinTable3.Themostefficientcomponentof
the engine is shown to be the high pressure turbine, with the
combustion chamber having the lowest exergy efficiency. This is
easilyunderstoodfromtheexergydestructionratesof468.262kW,
445.130 kW, 14492.396 kW, 146.473 kW, 578.281 kW and
244.785 kW for the fan, compressor, combustion chamber, high
pressureturbine,lowpressureturbineandby-passcanal,respec-
tively. High exergy destruction within the component is an
Fig.5. Temperaturevariationwithintheengineduringthemissionflight.
Y.S¸o€hretetal./Energy93(2015)716e729 723
Fig.6. Pressurevariationwithintheengineduringthemissionflight.
combustionchamber,highpressureturbine,lowpressureturbine
andby-passcanal,respectively.Dependingoninefficiencieswithin
the components, the exergy destruction rates of the fan,
compressor, combustion chamber, high pressure turbine, low
pressure turbine and by-pass canal are revealed as 109.873 kW,
57.142 kW, 2453.382 kW,11.701 kW, 64.718 kWand 45.070 kW,
respectively.
TheresultsoftheexergyanalysisaresummarizedinTable6for
theenginecomponentsatflightphase5.Here,thehighestexergy
destructionoccurswithinthecombustionchamberwitharateof
3080.99kW.Thecombustionchamberisfollowedbythefan,low
pressure turbine, compressor, by-pass canal and high pressure
turbine with exergy destruction rates of 74.602 kW, 62.587 kW,
49.673kW,44.091kWand13.281kW,respectively.Duetothis,the
exergy efficiencies of the fan, compressor, combustion chamber,
highpressureturbine,lowpressureturbineandby-passcanalare
Fig.7. TSFCandFARvariationoftheengineduringthemissionflight. 88.31%,95.46%,58.24%,98.91%,91.99%and90.549%,respectively.
AsindicatedinTable7,thehighpressureturbineisfoundtobe
themostefficientcomponentoftheengineatflightphasepoint6.
indicatorofirreversibilityandinefficiency.Similarly,improvement Theexergyefficienciesoftheothercomponentsare94.94%,92.57%,
potential ratesof thefan, compressor, combustionchamber,high 92.35%, 90.62% and 64.88% for the compressor, fan, low pressure
pressureturbine,lowpressureturbineandby-passcanalarefound turbine, by-pass canal and combustion chamber, respectively.
tobe 39.966 kW, 21.201 kW, 5129.251 kW, 2.140 kW,52.048 kW Additionally,theimprovementpotentialratesofthehighpressure
and14.702kW,respectively,atflightphasepoint2. turbine,compressor,fan,lowpressureturbine,by-passcanaland
Table4isasummaryofresultsobtainedfromanexergyanalysis combustionchamberarefoundtobe0.511kW,2.715kW,3.437kW,
oftheenginecomponentsattheendoftheclimbflightphase.From 4.368kW,4.198and788.318kW,respectively.
thetable,thecombustionchamberisnotedasthemostirreversible For the flight phase point 7, the results of exergy analysis are
component with a relative exergy destruction rate of 92.049%, designatedinTable8.Attheendoftheloiterphaseoftheflight,the
while the high pressure turbine takes the minimum exergy high pressure turbine and compressor are shown to be the most
destruction portion with a relative exergy destruction rate of efficientcomponentsoftheengine.Therelativeexergydestruction
0.523%amongallthecomponents.Improvementpotentialratesare rates of the fan, compressor, combustion chamber, high pressure
foundtobe1.118kW,3.056kW,854.654kW,0.150kW,5.210kW turbine, low pressure turbine and by-pass canal are found to be
and3.674kWforthefan,compressor,combustionchamber,high 4.970%,2.140%,86.868%,0.487%,2.446%and3.089%,respectively,as
pressureturbine,lowpressureturbineandby-passcanal,respec- anindicatorofirreversibility.Fueldepletionratiosandproductivity
tively. Depending on exergy destruction rates, the exergy effi- lacks of the components are directly proportionate to exergy
cienciesofthefan,compressor,combustionchamber,highpressure destruction rates and inversely proportional with exergy
turbine,lowpressureturbineandby-passcanalare95.93%,94.85%, efficiencies.
64.86%,98.91%,91.99%and91.72%,respectively. According to the exergy analysis conducted for the engine
InTable5,theexergyanalysisresultsoftheenginecomponents components under operating conditions at start of egress, the
at flight phase point 4 are given. According toTable 5, the com- highestexergydestructionrateis1293.872kWforthecombustion
bustion chamber is identified as the most inefficient component chamber.Theexergydestructionratesoftheothercomponentsare
amongallthecomponents,similartoflightphasepoints1,2,3and found to be 72.118 kW, 28.648 kW, 6.849 kW, 33.617 kW and
4. The exergy efficiencies of the components are 83.90%, 95.12%, 46.508 kW for the fan, compressor, high pressure turbine, low
64.83%,99.09%,92.15%and90.49%relatingtothefan,compressor, pressureturbineandby-passcanal,respectively.Earliermentioned
724 Y.S¸o€hretetal./Energy93(2015)716e729
Fig.8. Fuel,product,exergydestructionandimprovementpotentialratevariationsoftheenginecomponentswiththeflightphasepoints(plotsarelogarithmicallyscaled).
Table2
Exergyparametersofenginecomponentsatflightphasepoint1.
Component E_F(kW) E_P(kW) E_D(kW) ε(%) IP_ (kW) c(%) d x
F 5438.825 4937.736 501.088 90.787 46.166 3.077 0.007 0.008
AC 9220.385 8779.625 440.760 95.220 21.070 2.706 0.006 0.007
CC 40624.694 26243.682 14381.012 64.600 5090.832 88.299 0.190 0.243
HPT 9915.040 9771.390 143.650 98.551 2.081 0.882 0.002 0.002
LPT 6373.753 5798.294 575.459 90.971 51.956 3.533 0.008 0.010
BPC 4009.254 3764.417 244.837 93.893 14.952 1.503 0.003 0.004
Table3
Exergyparametersofenginecomponentsatflightphasepoint2.
Component E_F(kW) E_P(kW) E_D(kW) ε(%) IP_ (kW) c(%) d x
F 5486.345 5018.082 468.262 91.465 39.966 2.860 0.006 0.008
AC 9345.975 8900.846 445.130 95.237 21.201 2.718 0.006 0.007
CC 40947.408 26455.012 14492.396 64.607 5129.251 88.501 0.190 0.242
HPT 10027.496 9881.023 146.473 98.539 2.140 0.894 0.002 0.002
LPT 6425.034 5846.753 578.281 91.000 52.048 3.531 0.008 0.010
BPC 4075.563 3830.778 244.785 93.994 14.702 1.495 0.003 0.004
considerationsforenginecomponentsatflightphasepoints1,2,3, 2453.382 kW and 14363.42 kW at flight phase points 9 and 10,
4,5,6and7canalsobeassertedforenginecomponentsoperated respectively.Dependingonthisirreversibilitywithinthecombus-
underflightphasepoint8conditions(Table9). tionchamber,theexergyefficiencyofthecombustionchamberis
Tables10and11showtheexergyanalysisresultsforthestart foundtobe64.83%and64.54%atthestartandendofthelanding
andendofthelandingflightphase,respectively.Thehighestexergy flight phase, respectively. The exergy efficiencies of the fan,
destruction occurs within the combustion chamber with rates of compressor, high pressure turbine, low pressure turbine and by-
Y.S¸o€hretetal./Energy93(2015)716e729 725
Table4
Exergyparametersofenginecomponentsatflightphasepoint3.
Component E_F(kW) E_P(kW) E_D(kW) ε(%) IP_ (kW) c(%) d x
F 675.415 647.935 27.480 95.931 1.118 1.040 0.002 0.003
AC 1151.981 1092.650 59.331 94.850 3.056 2.245 0.005 0.007
CC 6922.185 4489.888 2432.297 64.862 854.654 92.049 0.214 0.279
HPT 1269.816 1256.001 13.814 98.912 0.150 0.523 0.001 0.002
LPT 813.215 748.127 65.088 91.996 5.210 2.463 0.006 0.007
BPC 536.222 491.834 44.388 91.722 3.674 1.680 0.004 0.005
Table5
Exergyparametersofenginecomponentsatflightphasepoint4.
Component E_F(kW) E_P(kW) E_D(kW) ε(%) IP_ (kW) c(%) d x
F 682.831 572.958 109.873 83.909 17.679 4.007 0.010 0.013
AC 1171.482 1114.339 57.142 95.122 2.787 2.084 0.005 0.007
CC 6976.796 4523.414 2453.382 64.835 862.729 89.478 0.215 0.283
HPT 1289.670 1277.969 11.701 99.093 0.106 0.427 0.001 0.001
LPT 824.891 760.174 64.718 92.154 5.077 2.360 0.006 0.007
BPC 474.172 429.102 45.070 90.495 4.284 1.644 0.004 0.005
Table6
Exergyparametersofenginecomponentsatflightphasepoint5.
Component E_F(kW) E_P(kW) E_D(kW) ε(%) IP_ (kW) c(%) d x
F 638.298 563.697 74.602 88.312 8.719 2.244 0.006 0.009
AC 1095.081 1045.408 49.673 95.464 2.253 1.494 0.004 0.006
CC 7378.577 4297.587 3080.990 58.244 1286.495 92.655 0.266 0.373
HPT 1223.031 1209.749 13.281 98.914 0.144 0.399 0.001 0.002
LPT 781.623 719.037 62.587 91.993 5.011 1.882 0.005 0.008
BPC 466.508 422.416 44.091 90.549 4.167 1.326 0.004 0.005
Table7
Exergyparametersofenginecomponentsatflightphasepoint6.
Component E_F(kW) E_P(kW) E_D(kW) ε(%) IP_ (kW) c(%) d x
F 623.466 577.176 46.290 92.575 3.437 1.882 0.004 0.006
AC 1063.199 1009.474 53.725 94.947 2.715 2.184 0.005 0.007
CC 6393.869 4148.786 2245.084 64.887 788.318 91.278 0.214 0.280
HPT 1168.222 1155.643 12.579 98.923 0.135 0.511 0.001 0.002
LPT 747.897 690.744 57.153 92.358 4.368 2.324 0.005 0.007
BPC 477.663 432.885 44.778 90.626 4.198 1.821 0.004 0.006
Table8
Exergyparametersofenginecomponentsatflightphasepoint7.
Component E_F(kW) E_P(kW) E_D(kW) ε(%) IP_ (kW) c(%) d x
F 352.555 279.907 72.649 79.394 14.970 4.970 0.012 0.016
AC 601.214 569.929 31.285 94.796 1.628 2.140 0.005 0.007
CC 3606.664 2336.916 1269.747 64.794 447.022 86.868 0.216 0.287
HPT 660.602 653.489 7.113 98.923 0.077 0.487 0.001 0.002
LPT 426.347 390.599 35.748 91.615 2.997 2.446 0.006 0.008
BPC 231.647 186.490 45.157 80.506 8.803 3.089 0.008 0.010
pass canal are 83.90%, 95.12%, 99.09%, 92.15%, 90.49% for flight oftheingressflightphase.Atflightphasepoint5,theexergyeffi-
phasepoint9,and89.71%,95.26%,98.58%,91.05%,93.78%atflight ciencyofthecombustionchamberdecreasesto58.24%.
phasepoint10,respectively.
InFig.9,theexergyefficiencyvariationsoftheenginecompo- 4.3. Resultsobtainedfromexergyanalysisoftheoverallengine
nentsareplottedduringtheflight.Itisclearfromthegraph,the
exergy efficiencies of high pressure turbine and compressor are Inthisstudy,inadditiontoacomponentbasedexergyanalysis,
approximatelyconstantat99%and95%,respectively.However,the theoverallengineisalsoexaminedaccordingtothemethodology
exergy efficiencies of the fan and by-pass canal dramatically previouslyexplainedforeachflightphasepoint.Asaresultofthe
decreaseattheendoftheloiterandthestartoftheingressflight analysis, the main exergy parameters of the engine are obtained
phases. The exergy efficiency of the combustion chamber is andcompiledinTable12.Thelowestexergydestructionwithinthe
approximately65%throughouttheentireflightexcludingtheend engineoccursatthestartoftheingressanddescentflightphases.