This article was downloaded by: 10.3.98.104 On: 03 Oct 2021 Access details: subscription number Publisher: CRC Press Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: 5 Howick Place, London SW1P 1WG, UK

Green Aviation: Reduction of Environmental Impact Through Aircraft Technology and Alternative Fuels

Emily S. Nelson, Dhanireddy R. Reddy

Improvement of aeropropulsion fuel efficiency through engine design

Publication details https://www.routledgehandbooks.com/doi/10.1201/b20287-3 Kenneth L. Suder, James D. Heidmann Published online on: 07 Sep 2017

How to cite :- Kenneth L. Suder, James D. Heidmann. 07 Sep 2017, Improvement of aeropropulsion fuel efficiency through engine design from: Green Aviation: Reduction of Environmental Impact Through Aircraft Technology and Alternative Fuels CRC Press Accessed on: 03 Oct 2021 https://www.routledgehandbooks.com/doi/10.1201/b20287-3

PLEASE SCROLL DOWN FOR DOCUMENT

Full terms and conditions of use: https://www.routledgehandbooks.com/legal-notices/terms

This Document PDF may be used for research, teaching and private study purposes. Any substantial or systematic reproductions, re-distribution, re-selling, loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden.

The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The publisher shall not be liable for an loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material. Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3 Improvement ofaeropropulsionfuelefficiency throughenginedesign CHAPTER 3 research efforts atGRCworking incollaborationwithN component efficiencies over thepast70years. Many oftheseimprovements wereenabled by increases inenginebypassratio(BPR),cycle pressureratio,turbineinlettemperature,and of thisimprovement canbetracedtoaircraftenginefuelefficiency improvements enabledby those inaircraftaerodynamics,vehicle weight,andaircraftengineefficiency. Alarge fraction (Rutherford, 2012). This improvement can be traced to many aircraft improvements including sector. agency, N and the associated carbon dioxide and other emissions. As the concerns over globalwarming andairqualityhave increasedthemotivation toreducefuelburn U.S. energy securityandlower relianceonforeignoil.Finally, inrecentyearsenvironmental efficiency throughmoreaffordable travel. Reducedfuelconsumptionisalsorelatedtoincreased and enginemanufacturers, andassociatedindustries. The publicbenefitsfromimproved fuel in thecostofoperationaircraft,whichdirectlyimpactsprofitabilityairlines,aircraft fuel consumption. There is an economic motivation in that fuel consumption is a large factor enabled throughN will focus primarily on aerothermodynamicimprovements to aircraft engine systems that were development foraircraftengineinlets,fans, compressors,turbines,andnozzles. This chapter system improvements throughconceptdevelopment, componenttesting,analysis,andmodel N of contributions toward theNation’s goalofimproved aircraftfuelefficiency. Specifically, the National Aeronautics andSpace Administration (N 3.1 Kenneth L.SuderandJamesD.Heidmann sometimes denotedasSFC), wellassecondarilyfromreductionsintheengineweight: primarily throughreductionin thepropulsionsystemthrust-specificfuelconsumption(TSFC , that propulsion system contributions to improved aircraft range (and reduced fuel burn) come rogate forreducedaircraftfuel burn forafixed mission. TheBreguet rangeequationshows Breguet rangeEquation(3.1).Inthisequation,increasedaircraftcanbeviewed asasur specific contributions ofGRCinthisarea. tions describing aeropropulsion fuel efficiency beforethe remainder of thepaperdelves into and development efforts. The following discussionwill walk throughthemathematicalequa- aircraft engines,itisimportanttounderstandtheunderlying physics motivating theseresearch Ames ResearchCenter, universities, aircraftsuppliers,andengineindustrypartners. ASA GlennResearchCenter(GRC)hasplayedadirectroleincommercialaircraftpropulsion Aircraft fuelburn perseat-milehasdecreaseddramaticallyover thelast50+years(Fig.3.1) There aremultiplemotivations forimproving aircraftfuelefficiency andthereby reducing The high-level startingpointforany discussionofaircraftfuelefficiency isthewell-known Before discussingdetailsofthehistoryGRCcontributions toimproved fuelefficiency for Intr ASA hasalarge stake inensuringimprovements infuelefficiency ofthe aviation oduction ASA researchefforts. Ai rcraft range = Velocity TS FC 49    Drag Li ASA) hashadalongandsuccessfulhistory ft    ln ASA Langley ResearchCenter, N    1 + WW Nation’s civil aeronautics research PL W fuel + 0   

(3.1) ASA - Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3 50 (Eq. (3.3)),astransmissionefficiency η

of thecycle (PR,oralsoknown as the overall pressureratio( OPR)): where SA 3.0license,https://creativecommons.org/licenses/by-sa/3.0/legalcode (accessed August 31,2016).) theicct.org/blogs/staff/overturning-conventional-wisdom-aircraft-efficiency-trends. Creative Commons CCBY- ventional wisdomonaircraftefficiency trends. TheInternationalCouncilonClean Transportation, http://www. Figure 3.1. Overall efficiency concepts toward capturingthosepotentialgains. improvements inthecoreengineandpropulsor. Section3.6willdiscusssome ofthefuture clear fromthefigurethat gains in overall efficiency areincreasedmostbysimultaneous Boeing 787stillleave roomforfuturegains inboththermalandpropulsive efficiency. Itisalso such astheBoeing777/GE90andmorerecentlydeveloped fuel-efficientaircraftincludingthe to theoverall efficiency. Itisalso worth notingthat even modernaircraft/enginecombinations engine development andhighlightsthemutual contributions ofthermalandpropulsive efficiency payload weight,and efficiency η ity andfuelenergy perunitmassitcanbeseenthatTSFCisinversely proportionaltooverall and hascontinuedtothepresentday. the majortrendfromturbojettolow- andhigh-bypassturbofan enginesthatbegan inthe1960s Figure 3.2plotstheTSFCbenefitsresultingfromsomeofthesearchitecturalchangessuchas in Section3.6,enginearchitecturalchangescanhave adramaticimpactontheengineTSFC. Drag representtheaerodynamic quantities ofthe aircraft performance. As willbeexplained later

ciency, however, assumesthatthecompression systemcomponentshave noaerodynamicloss. where The gas turbineengineBrayton cycle idealthermalefficiency η Figure 3.3shows aplotofthermalandpropulsive efficiency trendsspanning thehistoryofjet TSFC canbefurtherdecomposedasshown inEquation(3.2).For agiven aircraftflight veloc- K.L. Suder&J.D. Heidmann TR is the temperature ratio and TSFC representsenginethrust-specificfuelconsumption,W Average fuelburn fornew jetaircraft,1960to2010.(FromRutherford,D.2012.Overturning con- o : η

W o is primarily a function of propulsive 0

is aircraftemptyweight TS FC η = B η η =− o o tr γ is the ratio of specific heats. This ideal thermal effi- 1 () =(η isgenerallycloseto1.0: Fu TR el energy 1 th =− )(η Velocity . 1 The Velocity isthatoftheaircraft,andLift pr PR perunit )(η () γγ 1 tr − ) (3.3) 1 ma

(3.4) η ss pr and thermal

(3.2) B issetbythepressureratio fuel

is fuelweight,W η th efficiencies PL

is

Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3 and specificpower for various cycle pressure ratiosandturbineinlettemperatures. Thisfigure ciency potential. This is illustrated in Figure 3.4, which shows trends of ideal thermal efficiency thermal efficiency requiresincreased turbineinlet temperaturesto fully realize the thermaleffi- at GRChassupportedimprovements inthesecomponentefficiencies.Inaddition, thisideal the compressorandturbine. As willbeseenlaterinSection3.6.4 ofthischapter, muchwork The actualthermalefficiency ofthe cycle willdependonthecomponent efficiencies inboth

Figure 3.2. AIAA J. 52:901–911.ReproducedbypermissionUnited of Technologies Corporation, Pratt& Whitney.) 2014. Aeropropulsion for commercial aviation in the twenty-first century and research directions needed. provements. BPR, bypass ratio; LT Figure 3.3. State-of-the-art thrust-specificfuelconsumption(TSFC)trendswithsubsonicenginearchitecture. Comparison ofhistoricalenginethermal(η Improvement ofaeropropulsion fuelefficiencythrough enginedesign O, landing and takeoff; η th tr ) andeffective propulsion(η , transmission efficiency. (From Epstein, A. H. p ) efficiency im- 51 Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3 52 exit temperature (combustor inlet temperature), Consider alsothatasenginethermal efficiency and overall pressureratio increase,thecompressor has dramaticbenefitsattheaircraft systemlevel, particularlyformilitaryandhigh-speed flight. of theenginemustdecreasefor agiven enginecoreflow rate. Therefore,increasing allowable T efficiency, raisingturbineinlettemperature(T weight oftheengine.Inadditiontoenablingbenefitshigher engine cycle OPRandthermal cooling andmaterialsdevelopment intheincreasedcorespecificpower andresultantthrust-to- will offer astep-changeinturbineinlettemperaturesthefuture. materials. As discussedinChapter5,theintroductionofceramic-basedturbinebasematerials been enabledbyimproved turbinecoolingschemesandaboutone-thirdbyimproved turbine and 3.6thatapproximatelytwo-thirds ofthehistoricalincrease inturbineinlettemperaturehas designs andadvanced materials,includingthermalbarriercoatings.ItcanbeseenfromFigures3.5 have progressively increasedduetotheintroductionofincreasinglymoresophisticated cooling bine metal temperature. Beginning with uncooled metals before 1960, turbine inlet temperatures a technologythatwork synergistically withturbineinternalcoolingtoreducetheunderlyingtur increase turbineinlettemperaturecapability. Itshouldbenotedthatthermalbarriercoatingsare als improvements, and includes the more recent application of thermal barrier coatings to further advanced coolingstrategies aswelladvanced materials.Figure3.6demonstratesthesemateri- reflective ofthedirectimpactthisparameteronfuel burn reduction. inlet temperature.OPRshave continuedtoriseforbothaircraftand power turbineapplications, sure ratio. This explains theespeciallystrongemphasisinmilitaryenginesonincreasedturbine temperature resultsinahigherpower density, higherthrust-to-weightengineregardless ofpres- ratio advantage islost. Additionally, Figure3.4(b)demonstratesthatanincreasedturbineinlet must becoupledwithcomplementaryincreasesinturbineinlettemperature,orthepressure temperature. Higherpressureratios,andtheaccompanying advantages inthermalefficiency, illustrates that there is a synergistic relationship between cycle pressure ratio and turbine inlet important as the overall size of the engine is limited by airframe mounting considerations—for enables engines having acceptablethrust-to-weight andcorepower density. This alsobecomes For afixed T Figure 3.4. Figure 3.7 highlights the strong benefit of increased turbine inlet temperature enabled by this Figure 3.7highlightsthestrongbenefitofincreasedturbineinlet temperatureenabledbythis Figure 3.5shows ahistoricalprogressionofincreasedturbineinlettemperaturesenabledby K.L. Suder&J.D. Heidmann Brayton cycle thermalefficiency andspecific power trends. 4 , theamountofallowable energy addition in thecombustor decreasesandthethrust 4 ) increases the thrust-to-weight of the engine which ) increasesthethrust-to-weight of theenginewhich T 3 , increases due to increased compressive heating. 4 -

Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3 to thepresentday becauseofthedramaticfuel burn benefits. peratures forboth aviation andindustrial groundpower applicationsofgas turbines hascontinued provide thrust.Similarto theOPRtrenddiscussedearlier, thetrendtoward higherturbine- inlettem particularly importantwiththe rise ofvery high-BPRenginesandtheresultinglarge fans usedto

a given thrust, higherT Masson SAS. All rightsreserved.) advanced thermalbarriercoatings.Aerosp.Sci. Technol. 7:73–80.Copyright 2003,publishedbyElsevier from Schultze,U.,C.Leyens, K.Fritscher, etal.,2003.Somerecenttrendsinresearchandtechnologyof operational temperatureofturbinecomponents. Y-PSZ, yttriumpartiallystabilizedzirconia.(Adapted Figure 3.6. Zelina. 2003.Progressinaero-enginetechnology, 1939–2003. AIAA 2003–4412.2.) Figure 3.5. Turbine componentmaterialtemperature capabilityimprovements, showing increasein Turbine inlettemperaturetrendswithtechnologyimprovements. (FromBallal, D., andJ. Improvement ofaeropropulsion fuelefficiencythrough enginedesign 4 canimprove integration oftheenginewithairframe. This becomes 53

Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3 Figure 3.7. 91–2187.) is compressorinlettemperature.(FromKoff, B.L.1991.Spanningtheglobewithjetpropulsion. AIAA er, 54 which canfurtherreducefuelburn. power densitycorecanenableagreaterpercentageofBLIalongwithhigherBPR,both mitigated. For aircraft architectures which are proposed to benefitfromBLI,a smaller, higher if the detrimental effects of the resulting non-uniform velocity profile entering the engine can be airframe boundarylayerfluidintotheenginescanresultinanetaircraftfuelefficiency benefit boundary layeringestion(BLI).Itcanbeshown bycontrolvolume analysisthattheingestionof aviation, beginning withthe development ofimproved engines basedonthereciprocating engine Improving aircraftfuel efficiency hasbeen aneconomic considerationsince theearliest daysof 3.2 speeds typicalofthelarge commercialaviation market. and flightspeedwithhigh-bypassturbofan enginesbeing thearchitectureofchoiceforcruise thrust requirement.Enginepropulsive efficiency isstronglydependentonenginearchitecture large quantityoflow velocity airratherthanasmallerquantityofhighvelocity airforagiven producing device. This equationdemonstratesthatitismorepropulsively efficienttoejecta where The propulsive efficiency ofany thrust-producingdevice isgiven by Another technology which can potentially reduce aircraft fuel burn is the idea of engine m K.L. Suder&J.D. Heidmann ismassflow rate,γisratioofspecificheats,Ridealgas constant,TisgasT temperature,and Early Hist Fuel Efficiencyfforts, 1943 v istheflightspeedof vehicle andcisthevelocity oftheairejectedbythrust- Engine-specific power and thrustincrease withturbine rotorinlettemperature,T ory ofN ASA GlennResearchCe nter Aer η pr t = o 1958 1 + 2 v c (3.5) opr opulsion 4 . HP is pow- 2

Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3 1943 untilitsabsorptionintothenew N mance aircraftandinitiatedtheformationofN systems, but itwas theimpetusgiven by World War IIthataccelerated theneedforhigherperfor and propellercombination.Greatstridesweremadeintheearlydevelopment ofthesepropulsion ceased in1956. Itsaw continuedservice intheU.S.militaryuntil 1978. A culminationof this in many typesofmilitaryaircraft,and morethan30,000weremanufactured before production as thefirstaxial-flow turbojetapproved for civil use intheUnitedStates1949.Itwas used enabled thesuccessofGE J-47turbojet(GeneralElectriccompany designation TG-190) Wright J-65andGEJ-47engine series.Infact, testinginthe Altitude Wind Tunnel andERB tests conductedinERBthe late 1940sand1950swerenumerousexperiments related tothe combustion, heattransfer andotherenginecomponents. Among theturbomachinery component turbines forjetengines. This uniquefacility isstillinusetoday fortestingofturbomachinery, ton enginecomponentresearch,but was upgraded in1944toenabletestingofcompressorsand try andN Engine ResearchBuilding(ERB),providing essentialdatatotheindustryvalidate bothindus- 1950s. Many single-stageandmultistagecompressortestswereconductedattheCenterin role incomponentdevelopment initsCompressorand Turbine Division duringthe1940sand ciencies andenablethehigherpressureratiospromisedby architecture.GRCtookaleading with multistageaxialcompressorshighlightedtheneedforcomponent researchtoimprove effi- the UnitedStates,but notwithoutinitialtroubles refining early designs. These earlychallenges could bemastered. The axialcompressorquicklybecamethecompression system ofchoicein tages inefficiency andpressureratioifthecomplex aerodynamicsandmechanicaldesignissues cepts was simplerandmorereliable,but themultistage axialcompressoroffered potentialadvan- axial andcentrifugal compressors. The centrifugal compressor ofthe Whittle andvon Ohaincon- to 1955(Dawson, 1991). mance andcoolingtestsfrom1950to1952, Allison J-71and T-38 enginetestsfrom1952 mance testsfrom1945to1950, Westinghouse 24C-7 and24C-8engineafterburner perfor engine in1944,GE TG-180 and TG-190 (alsoknown astheJ-47)engineandafterburner perfor utable towork inthisimportantfacility werethesolutionofcoolingproblemsforR-3350 improvements in turbojet and turboprop engine fuel efficiency. Among the success stories attrib- a greatnumberofengineperformancetestswereconductedinthefacility andledtodramatic and itsconversion toavacuum facility forrockets underthenew N quickly converted totestturbojetand turbopropenginesupontheirintroduction.Between1944 propeller and engine mount and was initially conceived for piston engine research, but was to testaircraftenginesatsimulatedaltitudeconditions. The facility was large enoughforboth the GEI-Afortestinginnew Static Test Laboratoryin1943(Dawson, 1991). cating engines,thedawn ofthejetengineagebecame arealityatthecenterwithdelivery of in October1942. Although GRChadinitiallyfocusedsolelyonair- andliquid-cooledrecipro- on theteststand,anditflew inatwo-engine arrangement ontheBell AiracometXP-59Aaircraft expertise insuperchargers. InMarch1942,theGeneralElectricI-A Whittle-derived engineran in 1941.GeneralElectric(GE)was chosentodevelop theengineforproduction,owing totheir the Britishenteredintoanagreementtosendplansfor Whittle enginetotheUnitedStates Germany, GreatBritain,andthenintheUnitedStates.BecauseoffearsaGermaninvasion, obvious advantages of its high-speed flight capability and heavily supported development in compatible withtheflow ofairthroughtheengine, unlike areciprocatingengine(Conner, 2001). men realizedthatthejetenginewas uniquelysuitedtoproviding power forflightbecauseit was for higher-speed flight over theconventional reciprocatingengineand propeller combination.Both in thelate1930s,itsparked arevolutionary new meansofaircraftpropulsion,offering advantages independently began todevelop thegas turbinejetengineorturbojetfor flightapplication opment ofturbojetandearlyturbofan enginetechnology. When Frank Whittle andHansvon Ohain

One ofthe primary designchoicesinthe development of early turbojetengineswas between The GRC Altitude Wind Tunnel was completedin1944andwas thefirstwindtunneldesigned In theearly stages of turbojet engine development, the military was keenly aware of the ASA-developed models. The ERB was completedin1942,again predominantlyfor pis- Improvement ofaeropropulsion fuelefficiencythrough enginedesign ASA Agency in1958,GRCwas instrumentalinthedevel- ASA GlennResearchCenter. Fromitsgenesisin ASA spacedirective in1958, 55 - - - Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3 56 jet fuelpricesand theireffect onthe airlineindustry. Oil(andjetfuel) prices remainedrelatively Interest inaircraft fuelefficiency increased dramaticallyinthe1970s because ofthesharprisein 3.4 subsequent high-bypass-ratioturbofan engines. enabled by the introduction of the JT9D engine in 1970 and the CF6 engine in 1971 as well as 1991). Figure3.2demonstratesthatastepchangeinenginethrust-specific fuelconsumption was general werebasedondevelopments made byN fan usedintheCF6engineandinstallationtechnology forhigh-bypassturbofan enginesin engine. The GECF6was developed outoftheirmilitary TF-39 engine,andboththehigh-bypass was developing theCF6engine,often consideredthefirsthighbypasscommercialturbofan Meanwhile, highbypassturbofan engineswerebeingdeveloped bytheindustry. GeneralElectric that would beenabledalongwiththefuelburn reductionbenefitsofhigherbypassturbofans. a large partoftheresearch focus. The QuietEngineProgramlooked atenginenoisebenefits aircraft propulsionarchitecturetoday. high-bypass turbofan engine architecture that has become the predominant large commercial into productionengines.Figure3.8shows cross-sectionalschematicsoflow-bypass andthe increasing low spoolbypassflow andtheincorporationofa fan stageforthrustwereintroduced capable of providing an appreciable bypass flow and thrust, but slowly the additional benefits of speed ofeachspool.Initially, thisdesignchangewas notintendedtocreatealow pressurespool porate dual-spoolcompressorconceptstoallow forbetterefficiency throughoptimaldesign increased toenableimproved thermalefficiency forturbojetengines,designersbegan toincor matically reducefuelburn over thenext several decades. As compressorpressureratioswere In theearly1960s,turbofan enginesbegan toemerge—an enginearchitecturethatwould dra- 3.3 tics researchandtohelpsolve someofthesegrowing issues. associated withairportshadbecomeamajorissue.GRCwas calledupontoreinitiateaeronau- aviation industryhadgrown tothepointthatissuesofcapacity, congestion,noise,andpollution 1966 thattheCenterturneditsattentionbacktoaeronauticsresearch.By1966,commercial bofan enginedevelopment continuedintheaviation industryduringthisperiod,itwas notuntil and space research in response to the Soviet launch of Sputnik. Although turbojet and early tur and transpirationcooling. hollow turbine blades and continuing toward more exotic cooling schemes such as film cooling acceptance ofincreasinglycomplex turbinecoolingmethods beginning withinternallycooled Figure 3.5,thework conductedatGRCinthistimeperiodwas instrumentalintheindustry came to GRC and ledthe Center’s efforts at improving turbine cooling methods. Referring to War IIandworked initiallyattheU.S. Air Force’s Ohio. In1949he Wright FieldinDayton, Eckert. Eckert hadjoinedvon OhainandotherGermanscientistsintheUnitedStatesafter World fer and cooling research during the period 1943 to1957. A key figure inthiseffort was Ernst authoritative publicationonmultistageaxialcompressordesigntheoryandpractice. great value totheaxialcompressordesigncommunity formany yearsandisstillconsideredthe Compressors,” N and eventually declassifiedandrepublishedin1965as “Aerodynamic Design of Axial-Flow early periodofcompressortestingatGRCwas publishedasaseriesofclassifiedreportsin1956 When N In 1957,theCompressorand Turbine Division was disbandedasGRCmoved toward nuclear A similarresearchtrajectorywas playingoutintheareaoffundamentalturbineheattrans- K.L. Suder&J.D. Heidmann Energy Crisisof1970s Intr Pr opulsive Efficiency ASA reinitiatedaeronauticsresearchin1966,turbofan engine development became oduction f Turbofa n Engies ASA SP-36(BullockandJohnsen,1965). This N and N ASA Aer ASA andmilitaryprograms(U.S.Government, on and Impr a utics Response ASA publicationhasprovided o ved - -

Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3 filing in1991(Bowles, 2010). Pan American World Airlines tothebrinkofbankruptcy in1974andultimatelytobankruptcy 2012). This dramaticincreaseinfuelpricesputtheairlinesunderdeepfinancialpressure, driving fuel pricesbyafactor of4inthemid-1970sandafactor of8by1980(ShettyandHansman, stable foralongperiodfrom1945throughtheearly1970s,followed byspikes thatincreased Figure 3.8. pressor inlettemperatureandT known thatatlower flight speedspropellersoffer lower SFC becauseoftheirlow pressureratio pulsor forhigh-subsonic (MachnumberMapproximately 0.8)commercialaircraft.Itis well proposed totake thedramatic stepofincorporatinglarge, unductedpropellersasthemainpro- third GRCprojectunderthe ACEE Program was the Advanced Turboprop Project. This project fuel consumption. This aspect ismissedifoneonlycomparesperformanceofnew engines. The aviation fleet, the rateofperformance deterioration can have a dramatic impact on overall fleet oration comparedtotheCF6-50C. Sinceaircraftengineshave alonglifespan inthecommercial often-overlooked goaloftheE3Projectwas a50%reduction intherateofperformancedeteri- with improvements indirectoperatingcost,noise, emissions,andperformanceretention. An (installed thrust-specificfuelconsumptioncomparedtothe GE CF6-50C was establishedalong a new engineratherthansimplyimprove existing components. A goal of12%fuelreduction The E3Projecthadmoreaggressive goals thantheECIProjectinthatgoalwas todesign cific enginecomponents. Thesecondproject was theEnergy EfficientEngine(E3)Project. of thisprojectwas toincreaseaircraftenginefuelefficiency by5%throughredesignofspe- which relatedtoenginetechnologyandledbyN and GeneralElectricCF6-50C. The ACEE programwas composedofsixprojects,three more fuel efficient. Thebaselineenginesused forthis goalwerethe Pratt& Whitney JT9D-7A ment ofvarious aeronauticaltechnologiesthatwould make futuretransportaircraftupto50% Efficiency (ACEE) Programin1975. Thegoalofthisprogram was toacceleratethedevelop-

In responsetothisrapidincreaseinfuelprices,N The firstoftheseprojects was theEngineComponentImprovement (ECI)Project. Thegoal Turbofan engine architectures. (a) Low-bypass turbofan. (b) High-bypassturbofan. Improvement ofaeropropulsion fuelefficiencythrough enginedesign 4 isturbineinlettemperature. ASA GlennResearchCenter(Bowles, 2010). ASA establishedthe Aircraft Energy T 2 is com- 57

Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3 speed andwould potentiallybeabletooffset thenoisedisadvantage ofpropfans (Bowles, 2010). “propfan.” The sweptbladegeometrywould resultinalower tipMachnumberforagiven flight representative of fan blades than typical propeller blade shapes—hence the commonly used term solution toboththenoiseand high-speedefficiency problems was touseswept bladesmore in unductedconfigurations,having nonacelletoshieldandabsorbradiatednoise. Thetechnical at Mach 0.8 flight speeds and higher altitude flight as well as to mitigate the noise issues inherent such large-diameter propulsors. The challengewas to enable highly efficient turboprop operation efficient atlower flightspeedsbecauseofthehighrelative tipMachnumbersassociatedwith tecture viableforlarge civilian aircraft.Like propellers,turboprops(or “propfans”) weremore tion reduction relative to then-current engines. Major challenges existed in making such an archi- ment (Davis andStearns,1985). were achieved throughacombinationof materials development andcoolingconceptimprove- previous stateoftheart. Along withincreasedcycle temperatures,reducedturbine coolingflows turbine (HPT)andfive-stage low-pressure turbine(LPT),andcomponentefficienciesabove the fan, low-spool pressureratiotoarrive attheOPR),ahighlyefficienttwo-stage high-pressure (note thatthecompressorpressureratioisonlyapartof cycle OPR—onemustincludethe Project. ects suchasEnvironmentally Responsible Aviation (ERA)andtheSubsonicFixed Wing (SFW) reduce SFC,andcontinuetobethemaindrivers forsuchefforts even todayunderN temperatures, andimproved componentefficiencies. Thesearecommonthemesintheeffort to fan andhigherthermalefficiency byusinghigher overall pressureratio,higherturbineinlet et al.,1987). The E3Projectachieved higherpropulsive efficiency byusingalow-pressure-ratio Administration noise regulations, and(5)meetEPA then-proposedemissions standards (Ciepluch mance deteriorationby50%,(3)reducedirectoperatingcosts5%,(4)meetFederal Aviation To summarize,theE3Projectgoalswereto(1)reduceSFCby12%,(2) SFCperfor (Fig. 3.9),whichpowers theBoeing777aircraft,benefitedgreatlyfromE3Projectefforts. duced intoengineproductsthe1990sandbeyond. Specifically, GE’s large GE90engine turboprop was very enticingtotheaviation industry. fuel prices spiking, the promiseofreducedfuel burn engine concepts such as the advanced cally becauseofhighrelative Machnumbers,andacousticissuesbecomeproblematic.Butwith and high effective bypass ratio. However, at 58 Figure 3.9. The Advanced Turboprop Project under ACEE had a vision for a 20% to 30% fuel consump - Some ofthefeaturesGEE3effort includeda10-stage,23:1pressureratiocompressor The E3Projectfrom1975to1984developed many enginecoretechnologiesthatwereintro- K.L. Suder&J.D. Heidmann General ElectricGE90enginecrosssection. M = 0.8 thesebenefits typically diminishdramati­ ASA proj- -

Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3 Rarebird/0809.html (accessed April 28,2017).Copyright 2007. With permission.) (UDF) usedtwo contra-rotatingpropellers witheightbladeseach.http://www.b-domke.de/AviationImages/ Figure 3.10.

Wood and wake structureinanisolatedtransonicfan (Hathaway etal.,1986;Strazisar, 1985,1989; 67 was thefirstmajordatasetacquiredwithasingle-channel LDV, whichcapturedtheshock velocity inside the rotating passages of transonic compressors. The transonic fan N codes. LaserDopplervelocimetry (LDV) was customizedtomeasuretheaxialandtangential bomachinery analysistools,includingthegrowing fieldofcomputationalfluiddynamics(CFD) used bytheturbomachinerycommunityasabasisforvalidation anddevelopment of tur sets. Inthe1970sand1980sGRCproducedanumberofcompressor datasetsthathave been Nation onitstaxpayer-funded researchhasresultedin theproductionofopenexperimental data- tal capabilitiesforcompressorandturbinetestingtheemphasis onproviding returntothe Throughout N 3.5 would however returnin themid-2000swithspike infuelprices. ture andendedheavy N greatly reducedtheurgency fortheairlineindustrytoadoptaradicalchangeinenginearchitec- fuel pricesby1986hadretreatedbacktonearlypre-1970values ininflation-adjustedterms. This to turbofan engines,despitethelarge benefitsinfuel burn reduction.Perhapsmoreimportantly, engine architecturesmadetheairframersreluctanttodeviate fromtheirestablishedcommitment from comingtofruitioninthemarket. First,potentialnegative publicperceptionofpropellor-like terrotating GE“unductedfan” (UDF)concept(Fig.3.10),various factors kept theseconcepts N ating rangefrom maximumflow tonear-stall conditions at70%speed(fullysubsonic), 80% CFD blindtest case. N American SocietyofMechanical Engineering’s (ASME’s) InternationalGas Turbine Institute most widelyreferencedcompressor geometryforsuchdatasets,having beenthe basisforthe simultaneously inN tem was laterdeveloped andutilizedtomeasurebothaxialtangential velocity components LDV system (Hathaway etal.,1987;Suder al., 1987). A two-channel laseranemometersys - that capturedtheunsteadyfan rotor/statorbladerow interactionswiththe same single-channel ASA/Allison/Pratt & Whitney/Hamilton Standardsinglerotation conceptandthelatercoun- Although muchprogresswas madeonthedevelopment ofaviablepropfan throughboththe N D et al.,1987).Subsequently, N ASA’s Role inComponet Test Cases yn amics Development General Electricunductedfan engine. (FromDomke, B.2007. The GE36UnductedFan ASA GlennResearchCenter’s history, theuseofCenter’s uniqueexperimen- Improvement ofaeropropulsion fuelefficiencythrough enginedesign ASA Rotor37(ReidandMoore, 1978).N ASA Rotor37 has anextensive setofLDV dataacrosstherotor oper ASA investment inunductedconfigurations bythelate1980s. Theidea ASA Stage67(Rotor+Stator67)was thefirstdataset and Computation ASA Rotor37isperhapsthe al Fluid ASA Rotor 59 - - Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3 codes and the resulting designs. In the turbine area, an example of one the widely employed code validation datasets (Skoch Hathaway pressor tomake detailed measurements forcodevalidation andtheresults aresummarizedin Rotor 37testcase.Inaddition, N et al., 2002) which incorporates a full compressor stage versus the rotor-only approach of the turbulence modelimplementation, andtipclearancemodeling. CFD andexperimental resultshave led tosignificantimprovements inCFDmeshgeneration, in additiontotheunderlyingcodealgorithmsandmethods. These discrepanciesbetweenthe produced bythevarious codes,some ofwhichisattributable tohow thecodes wereemployed CFD codes(Dunham,1998). These testcaseactivities highlightedthelarge rangeofresults N rotor inisolation. The Advisory Group for Aerospace ResearchandDevelopment alsousedthe which indicatedthecodeswerenotaccuratelypredicting flow physics ofthiscompressor not onlyinthe level oftheperformanceparameter but also the shapeofradialdistribution, the state-of-the-art(SO pressure ratio,temperatureandefficiency. TheeightCFDcodesinFigure3.12represented and CFDresultsofoverall performanceat 100% design speedaswelltheradialdistribution of ASME blind testcase results, shown in Figure 3.12, compare the N and shock/tipleakagevortex interactionat 95% spanfora0.5%rotortipclearance. The detail isprovided inFigure3.11,whichshows theshockboundarylayerinteractionat70%span reference). The dataarebestsummarizedinSuder(1996),andanexample ofthemeasurement and 90%speed(transonic),100%designrotor(fullysupersonicintheframeof blockage andloss . Ph.D. N Thesis ( investigation of the flowfieldina transonic, axialflowcompressor with respecttothe developmentof n Figure 3.11. 60 ASA Rotor 37 benchmark data set to compare results from a large number of Additional experimental testcasesproducedbyGRCincludetheN K.L. Suder&J.D. Heidmann et al.(1993).Centrifugal compressor scalingstudies(Skoch andMoore,1987) ASA Rotor37LaserDopplervelocimetry data.(FromSuder, K.L.1996.Experimental A) predictiontoolsfromaroundtheglobein1994.Notediscrepancies ASA TM–107310), Case Western Reserve University, Cleveland, OH.) et al., 1997) were used to improve centrifugal compressor CFD ASA built a5-footdiameter (5ft=1.524m)centrifugal com- ASA Rotor 37 experimental ASA Stage35(Van Zante Navier-Stokes

Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3 CFD iscomputationalfluiddynamics,mthemassflow rateandm n Figure 3.12. Reserve University, Cleveland, OH.) with respect tothedevelopment ofblockage andloss.Ph.D. Thesis (N (From Suder, K.L.1996.Experimentalinvestigation oftheflowfieldina transonic, axialflow compressor

required toresolve the unsteadyfull-wheelflowfield forallstages. Thisisparticularly important throughout amultistage turbomachinewithout themassive timeandexpense thatwould be Navier-Stokes codeoffers theabilitytoaccuratelymodel thedeterministicimpactofbladerows the field. Aprime example ofthiscontribution isthe APN of N and Spalart-Allmarasturbulence models(DurbinandReif,2001). these endwall heat transfer data were instrumental in the development and assessment of the v2-f been usedtovalidate turbineheattransfertoolsacrossthecommunity(Fig.3.13).For example, test casesistheN N ASA has also directly contributed to CFD analysis improvement through development ASA in-houseturbomachinery codesthathave contributed tothe bodyofknowledge in ASA Rotor37 American SocietyofMechanicalEngineeringblindtestcase results(1994). Improvement ofaeropropulsion fuelefficiencythrough enginedesign ASA Transonic CascadeHeat Transfer dataset(Gieletal ., 1999),whichhas ASA code(Adamczyk,1984). This choke ASA TM–107310), Case Western isthechokingmassflow rate. 61 Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3 n Figure 3.13. 62 downstream fan aerodynamicperformance. ysis capabilityhasfoundexcellent applicationinstudyingtheimpactofdistortedinletflows on Navier-Stokes simulationsofmultistage compressorsandturbines. This kindofunsteadyanal- heat transfer. The TURBO code was developed under GRC funding and enables full unsteady ing internal passage heat transfer, film-cooled external heat transfer, and turbine tip clearance tions of turbineheat transfer analyseshave beencarriedoutusing the Glenn-HT code includ- methods toincreaseturbineinlettemperatures(Fig.3.14).Several first-of-their-kind demonstra- turbine cooling passages and film coolingholesthatwerediscussed earlier in thischapter as cooling andheattransferapplications.Ithasincorporatedtheabilitytoresolve thecomplicated TURBO, H3D, ADPAC, andSWIFT. The Glenn-HTcodedevelopment hasfocusedonturbine that have madeasubstantialimpacton the turbomachinery analysis field include Glenn-HT, turbine industryandisincommonusetoday. OtherN today’s computers. The APN for multistage compressors, where such an unsteady calculation would be prohibitive, even with have beenstudiedandbetter understood throughGRCefforts. tip leakageflows, turbinecooling flows, blade row interaction,stall inception and flow control and experimental investigations. Suchturbomachineryflow physics featuresasshockstructure, contributed significantly toturbomachineryflow physics insightfrom synergistic computational flow features.N Stokes equations,large eddysimulation,anddetailed spatial resolutionofsmallgeometricand prediction usingadvanced modelingtechniquessuchasunsteadyReynolds-averaged Navier- highlighting detailedflow phenomenasuchasleakageflows, resulting inbetter exit flow profile strong agreementamongthecodesforcompressorspeedline andstall,withsomeofthecodes Celestina andMulac,2009;Chima,Hah,2009,Herrick etal.,2009). The resultsindicated activity. The resultswerereported atthe2009 AIAA Aerospace Sciences Meeting(Ameri,2009; rotor 37andN APN K.L. Suder&J.D. Heidmann ASA, TURBO, Glenn-HT, H3D,andSWIFTwereallrecentlyvalidated against N ASA Transonic Cascade Heat Transfer data. ASA stage35testcasesaspartofaN ASA CFDdevelopments andapplicationstoturbomachineryproblems have ASA codehasbeendistributed totheU.S.aircraftandindustrialgas ASA-sponsored Navier-Stokes CFDcodes ASA turbomachinerycodeassessment ASA Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3 concepts. Among thekey propulsiontechnologies identifiedbytheseN +3 studiesare more which can serve as “collectors” for technologies that mayapplyto multiple long-term aircraft Airbus 320andBoeing 737asopposedtodeveloping anew aircraft. aircraft. This fact is evidenced bythelatest trendtore-enginecommercialaircraftsuch as the technology playsamoresignificant rolethanFigure3.15portraystoprovide morefuel-efficient is categorized underaircraft improvements forbookkeeping purposes. Therefore, theengine tion. ogy owing toitsimproved lift-to-dragratiorelative tothetraditionaltube-and-wingconfigura- (HWB) concept,andthelarge effect oftheHWBconceptitselfasafuelburn reductiontechnol- Unitized Structure—an advanced compositestructurethat may enablethe hybrid wing-body airframe dragbyreducingturbulent boundarylayer shear),PultrudedRodStitchedEfficient ogies representedincludelarge contributions fromhybrid laminarflow control(a way toreduce layer ingestionforthe“acceleratedtechnologydevelopment” configuration. Airframe technol- bar representingengines. A smallerbarof3.3%representsthepotentialbenefitboundary ogies ofallkinds,includingbothcoreandpropulsorimprovements, areincludedinthelarge for theN+3timeframe(about5yearsbeyond N+2).InFigure3.15,advanced engine technol- level (TRL)6by2020withpotentialentry intoservice(EIS)by2025)(Fig.3.15),aswell dicted improvement in aircraft fuel burn for the Responsible Aviation Projects indicate that the propulsion system plays a large role in the pre- Recent N 3.6 Figure 3.14.

The SFWProject’s N+3studieshave focusedprimarilyonadvanced aircraftconfigurations, Note that the reduction in aircraft size, drag,andweightdue to engine fuel burn reduction Current N ASA systemstudiesconductedundertheSubsonicFixed Wing andEnvironmentally Turbine tipflow structurespredictedwithmoderncomputationalfluiddynamics(CFD). Improvement ofaeropropulsion fuelefficiencythrough enginedesign ASA Efforts at ReducedFuelConsmption N+2 timeframe (engine technology readiness 63 Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3 readiness level. trol; PRSEUS,PultrudedRodStitchedEfficientnitizedStructure; TE, trailing edge; TRL, technology entry into service; HLFC, hybrid laminar flow control; HWB, hybrid wing-body; LFC, laminar flow con- n Figure 3.15. 64 emissions, fuel burn, andnoise. using either battery or fuelcellenergy sources thathave potential for significant reduction in distributed propulsion, boundary-layer-ingesting engines,andhybrid turbo-electricengines compact, high-efficiency gas generators, higherbypassratiosenabledby various methodsof K.L. Suder&J.D. Heidmann ASA fuelburn reductionestimatesforfutureaircraft.BLI,boundarylayeringestion;EIS, Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3

ing tohigheroverall pressureratioandturbineinlettemperature and enginearchitecturesaswellmoreaggressive enginecoretechnologydevelopment lead- However, increasedenergy pricestendstoplacearenewed emphasisonbothalternative aircraft onward areattributable totherelatively stablepriceofjetfuelfrom1985totheearly2000s. were studiedinthelate1980sunderN reduce aircraftfuelburn, openrotors(orpropfans orunductedfans, asthey wereknown then) in fuelburn becauseoftheirlow fan pressureratioandthusincreasedpropulsive efficiency. To Propulsion systemsincorporatingopenrotorshave thepotentialforgame-changing reductions 3.6.1 describe recentN reducing aircraftfuelburn andresultantcarbondioxideemissions. The following sectionswill warming fearshave risenduringthispastdecade,afactor thatplacesadditionalemphasison efficient aircraft. UDF design;thereby makingthemaviablepropulsor conceptforthenext generationoffuel- designs provide significant improvements inbothfuel burn andnoiserelative tothe1980s GE36 engine toamodernopen-rotor design.ItisclearfromFigure3.17thatthemodernopen-rotor 2013) compares the fuel burn and noise levels of the GE36 (1980s open rotor) and turbofan geometries for an isolated configuration during the phase 1testing.Figure 3.17 (Suder designs. Figure3.16shows anopen-rotormodeltestedatN ity ofmeetingbothnoiseandefficiency goalssimultaneously forthenew generationofopen-rotor to minimize noise while still maintaining efficiency. These modeling advances increase the possibil- tational fluiddynamics over thelast20yearsenablethree-dimensional(3D)tailoringofbladeshapes investigated aswellinstallationeffects suchaspylon andfuselageintegration. Advances incompu- efficiency fromacounter-rotating open-rotor system.Candidatetechnologiesforlower noise were Administration toexplore thedesignspaceforlower noisewhilemaintainingthehighpropulsive and thedesireforreducedemissionshasresultedinarenewed interestinopen-rotorsystems. propellers ended.Recentuncertaintyinoilpricescombinationwithclimatechangeconcerns goals. When oilpricesdroppedinthe1990s,technologydevelopment intheareaofhigh-speed ology, it was necessary to compromisethe GE36 aerodynamics so the engine could meet noise demonstration of the technology. Because of limitations of the design andmodeling method- example ofthisdevelopment effort. The UDFwas installedontheMD-80aircraftasaflight aforementioned oilpricespikes oftheprevious decade. The UDF, orGE36engine,was one (8×6 SWT)forcruiseperformance testing. For thethirdphaseoftestingrigwas installedinthe8-by6-Foot Supersonic Wind Tunnel cant upgradessuchasanew digitaltelemetrysystemforrotorforceandstraingage monitoring. at GRC.ORPRwas completelyrefurbishedforthecurrenttestentry andalsounderwentsignifi- Propulsion Rig(ORPR)isinstalledinthe9-by15-Foot Low-Speed Wind Tunnel (9×15LSWT) and acoustics,(2)diagnostics,(3)cruiseperformance.For phases1and2theOpenRotor synopsis oftheactivity. in Van Zante(2013)and Van Zanteetal.(2014),andthefollowing paragraphsprovide abrief the acousticsignaturebut maintainperformance. The open-rotortestcampaignisdocumented sent moderndesignsthatincorporatevarious 3Ddesignfeaturesandotherstrategies toreduce improve modelingandsimulationcapabilities foropenrotors. The otherfive bladesetsrepre - acoustic measurementsoftheHistoricalBaselinebladesetwereusedasabenchmarkdatasetto sets, theHistoricalBaselinebladeset,isrepresentative of1990sbladedesign. Aerodynamic and were evaluated fortheiraerodynamicperformanceandacousticcharacteristics.Oneoftheblade Much ofthe“leveling-off” ofaircraftfuelburn reductionsseeninFigure3.1from1990 N N The open-rotortestprogramconsistsofthreephases:(1)takeoff andapproachaerodynamics During thetestcampaignsixdifferent bladesetsoruniquecombinationsofforeandaftblades ASA hasbeencollaboratingwithGeneralElectric Aviation andthe Federal Aviation ASA acquiredasubstantialamount ofaerodynamicandacousticdataonavariety ofblade Open-rotor propulsors ASA andindustryefforts atmeetingthisneedfor theaviation sector. Improvement ofaeropropulsion fuelefficiencythrough enginedesign ASA Advanced Turboprop Projectasaresult ofthe ASA GlennResearchCenterrecently. (T 4 ) cycles. Inaddition,global et al., 65 Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3 0414. Work oftheU.S.Government.) ation project’s propulsion technologyphaseIoverview andhighlights ofaccomplishments. AIAA 2013– (From Suder, K.L.,J.Delaat,C.Hughes, D. Arend, etal.,2013.N 15 EPNdBnoisemargin toInternationalCivil Aviation Organization Chapter4standard (ICA Figure 3.17. n Figure 3.16. 66 K.L. Suder&J.D. Heidmann Modern openrotordesignsprovide greaterthan25%reductioninfuelburn andabout ASA-General Electricopen-rotortestingconfiguration. ASA environmentally responsible avi- O, 2008).

Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3 the U.S.Government.) Updated assessments ofanopen-rotorairplaneusing advanced bladedesigns. AIAA 2013–3628. Work of ratio; TF, turbofan; UHB,ultrahigh-bypass. (FromHendricks,E.S.,J. Berton, W. J.Haller,et al.,2013. Figure 3.18. and ductedhigh-bypasspropulsorsareshown inFigure3.18. The aircraftwiththeopen-rotor mission rangeof3250nauticalmiles. A comparisonofthefuelburn andnoisefortheopen-rotor rear fuselage-mountedenginesandhaving acruisingMachnumberof0.78at35,000ftand et al., 2013). The N aircraft platformtocomparethetradeoff betweenfuelburn andnoisereduction(seeHendricks comparison of an open-rotor systemtoa high-BPR ducted propulsor, N improved aeroandacoustictoolstomitigate theinstallationeffects. Inordertoperformadirect some ofthechallengesinmakingopen-rotorsystemsviable. The futuredesignintentistouse with theaircraftfuselage. in atranslatingplate. This typeofdataisusefulinanalyzingtherotorpressurefieldinteraction surements wereacquiredneartherotortipsfromalineararrayofpressuretransducersmounted number ofapproximately0.78intheGRC8×6SWT. Inaddition, unsteadypressurefieldmea- intensities) weredeterminedfromthemeasurementsinsupportofbroadbandnoisepredictions. and tipvortex insupportoftonenoisepredictions. Inaddition,second-orderstatistics(turbulence and was usedtoquantifythevelocity characteristicsandtrajectoryoftheforward rotorwakes edge ofthegenericpylon. Stereoparticleimagevelocimetry isthefourthmeasurementtechnique history ofstaticpressurefluctuationsontheforward andaftrotorairfoilsaswellthetrailing Pressure-sensitive paintwas usedtoquantifythemagnitudeandinferinformationabouttime the acoustic“adder”thatmustbeappliedtoaccountforarealisticinstallationonaircraft. ing edgeofthepylon. Farfield acousticdatawere acquiredwiththe pylon installedtodetermine tic phased-arraytechniqueidentifiednoisesourcelocationsonthebladesaswelltrail- techniques wereappliedduringthediagnosticstesting,eachwithaspecificobjective. Theacous- namic andacousticpenaltiesassociatedwithanaircraftinstallation.Four different measurement installed upstreamoftherotors. The pylon installeddatawillbeneededtoassesstheaerody- Measurements wereacquiredinanisolatedconfigurationaswellwiththegeneric pylon useful formodelingthesesystemsbut alsoforunderstandinghow futureprogressispossible. The datagathered andunderstandingobtainedfromthetestingwillbeinstrumentalinsolving Phase 3ofthetestcampaigndeterminedrotoraerodynamicperformanceatcruiseMach The diagnosticsprogramacquiredacomprehensive, detaileddataset,whichisnotonly Comparison ofadvanced turbofan andopenrotor oncommonaircraftplatform.BPR, bypass Improvement ofaeropropulsion fuelefficiencythrough enginedesign ASA notional aircraftdesignwas amodern162-passengerairplane with ASA designed a common 67 Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3 9 to12,thesecond-generation GTFwillnecessarily needtooperateataBPR from15to18, for the aircraft system as well. Whereas the first-generation GTF operated at a BPR of around lowing andtheadditional technologiesthatwillbeneededfornotonlythepropulsion systembut needed toachieve theN+2goals.Figure3.19illustrates thetechnologyroadmapN reaching N shift necessarytoreducethefuel burn minimumpointeven further. pressure ratiocurve, and atasignificantincreasein fan BPR,toachieve thesecondparadigm decreases. Sothenext-generation GTFwillberequiredtooperateatthelower endofthefan first generationGTFisbetween1.2and1.5, but as the fan BPRincreasesthe fan pressureratio increasing propulsive efficiency andreducingfuel burn. The fan pressureratiocurve forthe can enablefurtherreductionsinfan pressureratiocompared withdirect-drive turbofans, thereby fans arelimitedintheirabilitytooperateatvery low fan pressureratios. The GTFarchitecture nongeared counterpart,but withlessenergy expended. turbofan usesalarger fan thatmoves moreairatalower speed,allowing thesamethrustasits shaft andthefan enablesboththefan andLPTto operateattheiroptimumspeeds. A geared Introducing aplanetaryreductiongearboxwithsuitablegear ratiobetweenthelow-pressure slowly sothatadditionalLPTstageswillberequiredtoextract sufficientenergy to drive the fan. LPT increases.Consequently, ifthefan istorotateatitsoptimumbladespeed,theLPTwillspin conditions—and soreducedfuelburn. As BPRincreases,themeanradiusratiooffan and allows thefan andLPTtooperateatdifferent speeds—thusmoreoptimum,higherefficiency goes down, increasingfuelburn. P&WintroducedagearboxintotheirGTFenginedesignthat speed. At low fan speeds,theLPTisoperatingatfaroff-design conditions,anditsefficiency of both.Direct-drive turbofans necessarilyoperatethefan andlow-pressure turbineatthesame the GTFisachieved byoperatingthefan andcoreinsuchaway astooptimizetheperformance of UHBenginesthatwillseeEISwithanaircraftmanufacturer. The paradigmshiftproducedby has beeninvestigating UHBtechnologyover thelast20years,but theGTFisfirstgeneration defined asengineswitha fan BPRequaltoorgreaterthan12.N Pratt & Whitney (P&W)withtheirgeared-turbofan (GTF)UHBenginedesign.enginesare produced by introducing advanced fan and core technology. A shift of this type was produced by larger fan. Hence,atechnologyparadigmshiftisneededtoreducetheminimumpoint,which The larger, heavier nacelleproducesmoredragduringflight, and overcomes theadvantages ofa the fan sizecontinuestoincrease,aminimumisreachedbetweenfan sizeandweightdrag. there is a corresponding drop in fan pressure ratio and an increase in fan BPR. At some point, as directly correlated to fan size, fan pressure ratio and fan bypass ratio. As the fan size increases, higher bypassratiosandlarger fan diameters. Aircraft enginenoiseand fuelburn reductionare N 3.6.2 provide comparablefuelburn reductionsasan open-rotorsystem?” where thequestiontoconsideris,“Will themoderngeared-turbofan engine,onceoptimized, The next sectiondiscussesthedevelopment oftheultrahigh-bypass(UHB)ductedpropulsor, (and acousticliner),andasaresult,have greaterflow andacousticinteractionswiththeairframe. the acousticmargin ofductedsystemsbecauseopen-rotorbydefinitionhave noduct installed oncommercialaircraft. Also, itisunlikely thatopen-rotorsystemswillbeabletomatch lation effects andcertificationsmustbeaddressed beforeopen-rotorpropulsionsystemsare requirements andoffer substantialreductionsinfuel burn. Inaddition,moreresearchoninstal- this notionalaircraftsizeandmission. engine andattheexpense ofanincrease7dBcuminnoiserelative totheductedpropulsorfor propulsor provided anadditional9%reductioninfuelburn despitetheincreasedweightof 68 ASA’s aggressive noiseandfuelburn reductiongoalsaredriving aircraftenginedesignsto The UHBenginetechnologyassociated withthefirst-generationP&WGTF was closeto Fan propulsive efficiency increaseswithdecreasing fan pressureratio, but direct-drive turbo- In summary, themodernopen-rotor designsprovide significantmargin inStage4noise K.L. Suder&J.D. Heidmann Ultra-high-bypass enginecycleresearch ASA’s N+1noiseandfuelburn reductiongoals,but additionaltechnologies are ASA incooperationwithP&W ASA isfol- Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3 accomplishments. AIAA 2013–0414. Work oftheU.S.Government.) environmentally responsibleaviation project’s propulsiontechnologyphaseIoverview andhighlightsof into service; TRL, technology readiness level. (From Suder, K. L., J.Delaat,C. Hughes, etal.,2013. N ultrahighbypass(UHB)propulsiontechnologyroadmap.BPR,ratio;EIS,entry Figure 3.19. Blended-wing-body vehicles offer anattractive method toleverage boundary-layer-ingesting age ofthisboundary layerbyusingdistributed propulsorsacrossthe uppersurface ofthevehicle. from thevehicle ingested intotheengines,sosomeconceptsattempttocapturealarger percent- deficit (seeFig.3.20). Thepotentialbenefit dependsupon thepercentageofboundarylayer by reducingthejettingvelocity (c)comparedtoapoddedengine andreducingthevehicle wake This technologybenefitsthepropulsive efficiency ofthe vehicleasdescribedinEquation(3.5) 5% to10%becauseoftheirreacceleration offluidslowed bytheviscousdrag ofthe vehicle. Embedded engineswithboundary layeringestionoffer anadditionalfuelburn benefitofupto 3.6.3 test hardware. including testingoftheadvanced O with aminimalimpactonaerodynamicperformance,optimally lessthan0.5%infan efficiency, and acousticallytreatedsoftvanes (SVs)isfocusingonachieving 3to4dBofnoisereduction meet the aggressive noise goals. The next generation of over-the-rotor acoustic treatment (O technology. Investigating advanced noise-reductiontechnologiesarealsointheN heavy, andsoN as 50%toachieve theproperfan operatingconditions.However, traditional VAN designsare the UHBpropulsioncycle mustoperateover, thefan nozzleareaisrequiredtovary asmuch nozzle (VAN) technologiesarebeinginvestigated. Becauseofthewiderangeflightconditions increase propulsive efficiency and lower nacelleweight. Atthesametime,new variable-area This test will investigate new three-dimensional fan geometries and advanced inlet designs to a 22-in.(56-cm)fan diameter, fortestingintheGRC9-by15-Foot Low-Speed Wind Tunnel. ogy forthenext-generation GTF. result, N possibly ashigh20,withcorrespondinglylower fan pressureratiosbetween1.2and1.4. As a N ASA andP&Whave beencollaboratively designingascalemodeloftheGTFGen2,with Boundary-layer-ingesting engines ASA andP&Whave again teamedtodevelop propulsionandnoisereductiontechnol - ASA isinvestigating advanced, lighterweightdesignsusingshapememoryalloy Improvement ofaeropropulsion fuelefficiencythrough enginedesign TR/SV designsusingexisting 22-in.-scale-modelturbofan ASA plansto ASA TR) 69

Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3 concept. n Figure 3.22. n Figure 3.21. to station0,upstreamofengine.(a)Conventional (jet)propulsion.(b)BLI Figure 3.20. 70 ing ample stability margin. The study used an existing N the identifiedaircraft benefitsbyachieving lessthana2%loss in fanefficiency whilemaintain- is todemonstrateanembedded integrated inletanddistortion-tolerantfan system thatprovides this problemandflow controltechnologiesthatcanmake the fan inflow moreuniform. Thegoal Technologies ResearchCenter(UTRC)arejointlyinvestigating fan designsthatcanmitigate radation oflifeduetotheperiodic distortionexperienced bytherotatingfan. N Turboelectric Distributed Propulsionconcept,respectively. Institute of Technology-Pratt & Whitney “double-bubble” configuration andtheN Figures 3.22and3.23show additionalBLI-relatedconcepts,includingtheN concept fromingestingtheboundarylayeronN flexibility inenginemountingontheuppersurface oftheliftingbody. Figure3.21shows a engines becauseoftheirlarger surface area,whichresultsinalarger boundarylayerandmore One ofthechallengesforBLIengines, however, isthepotentiallossinfan efficiency anddeg- K.L. Suder&J.D. Heidmann Propulsion benefitsofboundarylayeringestion(BLI),intermsbladetipspeedUrelative ASA-Boeing blendedwing-bodyconcept. ASA, MassachusettsInstituteof Technology, andPratt& Whitney doublebubble aircraft ASA-Boeing blendedwing-bodyaircraft. ASA Research Announcement (NRA) ASA-Massachusetts ASA andUnited ASA in-house Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3

ing theturbineinlettemperature (T the compressionsystemwhile maintainingorimproving aerodynamicefficiency andincreas- efficiency arepresented. reductions. InthissectiontheareasofN ciency inordertomake thebiggestimpactonoverall engineefficiency andresultingfuel burn recall thatitisimperative tomake improvements inbothpropulsive efficiency and thermaleffi- ingesting engines addressed improvements in propulsive efficiency. Returning to Figure 3.3, The previous sectionsonopen-rotorpropulsors,ultrahigh-bypassengines,andboundary-layer 3.6.4 the relevant physics. system-level benefitswillbe validated alongwiththedesignandanalysistoolsrequiredto model to finish before summer 2017. Through this effort, distortion-tolerant fan technology and maintain asufficientstabilitymargin. Thetestisinprogressasofthiswritingand expected the testistoassessabilityoffan tosustainhighperformancewithminimallossand to simulatethatofaHWBvehicle suchastheoneshown inFigure3.21. The mainobjective of tains aporoussectiontoprovide bleedcontroltoadjust theincomingfan/inlet boundary layer thick inlet boundary layer. Downstream of the rods and upstream of the inlet, the false floor con- inlet/fan hardware. Notetherodslocatedfar upstreamoftheembeddedfan inlettoprovide a experiment isshown inFigure3.24whereafalse floor was insertedinthetunneltomount 8- by6-Foot Supersonic Wind Tunnel atGRC. The arrangementofthisembeddedpropulsor 2011; Ferraretal.,2009;Florea2009. Arend embedded inletanddistortiontolerantfan design,andtheaeromechanicsanalysisisfoundin relevant publicationssupportingthisactivity inclusive ofsimulatedaircraftboundarylayer, the space andtodesignbuild anintegrated inletandfan embeddedsystem. A samplingofthe Polytechnic and State an axi-centrifugal compressor, wherebytherearaxial stagesofthemultistagecompressor are configuration. constraints fortheinletboundarylayerandrequirementsarelevant embeddedengine sponsored blended-wing-body design such as is depicted in Figure 3.21, to define the design n Figure 3.23. increased combustor inlet temperature These competingdemandsrequire ever-smaller rearcompressorstageblade heightsalongwith Another challengeisrelatedto the needformorecompact,high-OPR,high-bypass-ratioengines. combustor. These arechallenginggoals,becauseinboth cases thesearecompetingconstraints. In thecoreturbomachineryarea, theemphasisisonincreasingoverall pressure ratioof N ASA istestingadistortion-tolerantfan witharelevant boundarylayerinflow fieldinthe ., 2014; Tilmanet al.,2012;Floreaal.,Bakhle Engine core research ASA turboelectricdistributed propulsionconcept. N ASA partnered with Improvement ofaeropropulsion fuelefficiencythrough enginedesign University (Virginia Tech) through the 4 ) whilereducingnitrogenoxide (NO UTRC, Pratt & Whitney Aircraft Engines and Virginia T 3 ASA researchanddevelopment toimprove thermal values. One potential solution to these demands is NRA to exploit the optimal design x ) emissionsfromthe et al., 71

Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3 ing, inwhichcase theoverall efficiency ofthecompressionsystem tendstosuffer because of mental databases.RefertoReid andKey (2015), Volino (2017),andKatz(2017). chinery community, intheongoingspiritofN experimental dataforuse incomputationalfluiddynamics validation efforts acrosstheturboma- aerodynamic lossandincreased pressureratiocycle engines. The awards arealsoproducing standing andmitigating turbine andcompressortipclearanceflows, which can enablereduced also recentlyfundedasetofN currently studying this and other potential solutions to this challenging problem.N or innovative coolingschemes would potentiallyberequiredtoenablethisconcept.N small correctedmass-flow values requiredofsuch cycles. Highertemperaturematerialsand/ replaced byacentrifugal rearstagethatwould beabletooperateatahigherefficiency forthe Figure 3.24. and fan installationinthe8×6SWT. bleed platesareusedtocustomizeboundarylayerupstreamoffan inlet.(b)close-upoftheintegrated inlet Wind Tunnel (8×6 SWT).(a)Barsupstreamoffan are usedtothicken boundarylayer, anddownstream 72 Increasing compressor OPReitherdrives thedesign toward more stagesorhigherstageload- K.L. Suder&J.D. Heidmann Boundary layeringestion(BLI)fan testriginstalledinN ASA Research Announcement awards focusing onbetterunder ASA-led development ofturbomachineryexperi- ASA Glenn8-by6-Foot Supersonic ASA has ASA is - Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3 Unfortunately, the efficiency goalswere notobtainedatthishighblade loading(refertoFig.3.25). ing levels (pressureriseper stage)withincreasedefficiency relative tothe bestcurrentdesigns. design goalswas investigated. This designpushed the SO above thedashed linewould representadesignthatwas betterthan theSO loading isthemoredifficultit is to achieve highefficiency. Any compressorwithadesign point the squareofrotortiprotational speed)andefficiency. Asshown, thehigherthatblade represents stateoftheartforblade loading(representedasthechangeinenthalpy divided by design. A pictorial view of the design space explored is found in Figure 3.25. The dashed line campaign (N sure ratiosix-stagecorecompressortodeterminewhatlimits bladeloading. The secondtest first testcampaign(N ing) and efficiency without negatively impacting weight, length, diameter, and operability. The and analysiscampaignsexplored thedesignspacetoimprove thecompressorOPR(bladeload- Van ZanteandSuder (2015)forbackgroundontheN achieve a2.5%reductioninenginespecific fuelconsumption.RefertoSuderetal.(2013)and pressure riseby30%relative totheERA baselineengine(GE90onthe777-200)to goal of the ERA highly loaded compressor activity was to increase efficiency and to increase ogies toenablehigh-efficiency andhighOverall PressureRatiocoreengines.Specifically, the The N 3.6.4.1 given componentefficiency. higher efficiency canbeattainedatagiven loadingorahighercanbeachieved fora research programsistopushthecomponentefficiency-loading curve highersuchthateithera to increasedOPRishigherstageloading. The emphasiswithintheindustryandinN dynamics issuescanalsolimittheuseofadditionalcompressorstages,sooftensolution ing loss,respectively. Overall enginesizeand weight constraints, engine operability, and rotor either increasedwettedareaanddraglossesorboundarylayerseparationmix- in enthalpy dH relative tothestate-of-the-art bestcurrentpracticesasindicatedbythedashedline,representingchange Figure 3.25. and emissionsreduction.ISABE2015–20209. Work oftheU.S.Government.) K. L.Suder. 2015.Environmentally responsibleaviation: propulsionresearchtoenablefuelburn, noise,

In ERAPhase1,alegacy high-OPRcompressordesignthatfell shortoftheefficiency ASA Environmentally Responsible Aviation Projectfocusedonthecompressortechnol- NASA ERAcore compressor technology development efforts ASA ERAPhase2)focusedontwo builds ofthe frontstagesofanew compressor Compressor designspaceforEnvironmentally Responsible Aviation Phase1and2 ave divided by the square of the rotor tip rotational speed Improvement ofaeropropulsion fuelefficiencythrough enginedesign ASA ERAPhase1)investigated thefronttwo stagesofalegacy high-pres- ASA ERAPropulsionactivities. Two test A designspacetohigherblade-load - U tip 2 . (From Van Zante, D. E., and A. ASA 73

Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3 74 high-speed multistage compressor test facility, W7 in the Engine Research Building at mechanisms and interaction effects of embedded transonic highly loaded compressor stages. The is complete,andinitialresultsindicatethecompressorhasmet its designintent. only in agreement with each other but are also in agreement with the designintent.Build2testing required toprovide thebleedflow. Extensive CFD simulationsthathave beenconductedare not compressor bleedlocationstobemoved further upstream,therebyreducingthecompressorwork The higherbladeloadingofBuild2provides anoverall systembenefitbecauseitallows forthe loading (pressure rise perstage) at the same efficiency levels ofBuild2, asshown in Figure 3.25. test wheretheprimarydifference isthatBuild2was designedtoachieve highercompressor blade the Phase1testing. The Phase2compressortestcampaign consistedofaBuild1testand2 three stagesofahigh-efficiency, high-OPRcorecompressordesigninthesameN Phase 1design(discussedintheprevious paragraphs).For ERAPhase2,N to bestcurrentdesignbut nottothehigherlevels ofbladeloadingthatwereattempted in the levels arehigherthanthoseofPhase1andthattheblade-loadinglevels wereincreased relative efficiency andbladeloading.RefertoFigure3.25 notethatthePhase2compressorefficiency learned fromthePhase1compressordesign. The Phase2compressorwas designedforincreased results refertoCelestina,etal.(2012),andPrahst,(2015). the compressor. For additional detailsanddiscussionofthe CFD analysisandexperimental test the secondstage. Therefore, themajorsourceofunexplained lossresulted fromthefirststageof figurations revealed thatthelevel of performanceatthislocationisunaffected bythe presenceof that was notpredictedbydesigntools. Assessment ofStator1LEmeasurementsinbothtestcon- leading toastagemismatchissue. The mismatch isthoughttobeduealossinthefirststage 2 was chokingatamassflow ratethatprevented stage1fromreachingitspeakefficiency point, device tomeasureinstantaneouspressure),andtraversing probes. The resultsindicatedthatstage data fromleading-edge(LE)instrumentation,wall statics,over therotorKulites (apiezo-electric detailed datatodefinetheinletboundaryconditionscompressor. This approachenabledtheabilitytosortoutlosscontributions fromeachstageandprovided after addingthesecondstagetoenableevaluation oftheperformanceandlossesineachstage. plan focused on making steady and unsteady measurements for the single stage and then again and atransitionductfromthelow-pressure compressor(LPC)totheHPCcompressor. The test inlet conditionstoahigh-pressurecompressor(HPC)ofanengine,inclusive offan framestruts Glenn ResearchCenter, was usedtorunthistest. The inlettothecorecompressormodeled ing a75%reductioninlanding andtake-off (LT The ERAgoalisa50%reduction infuelburn below currenttechnology aircraft,whileachiev- 3.6.4.2 prediction toolsbycomparisonswiththeexperimental results. actions andtheirimpactonloss,(3)validate thedesignmethodologyandcapabilityof (1) understandtheflow physics thatresultedinhighlosses,(2)characterizethebladerow inter analyze, andtestthefirsttwo stagesofatransonicSO to the shock and/or blade row interactions. Therefore, the goals in ERA Phase 1 were to isolate, passage shocksandfurtherimpactflow separations and/orlow momentumandlossregions due sensitive tovariations intheeffective flow area,whichcan affect thelocationandstrengthof design. The fronttwo stagesaretransonicacrossthespan,andthereforetheirperformanceisvery The highlosseswereattributed tothefronttwo stagesofthishighlyloadedsix-stagecompressor changes inengine diameterrequiredtoachieve thehigher bypass.Notonlydoesthis enablethe High-power-density coresenableUHBsystemsby increasingthebypassratiowith minimal Achieving thisgoal requiresdevelopment ofhigh-power-density, high-thermal-efficiency cores. on Aviation Environment Protection CAEP-6standardrequirements(Suderetal.,2013). ERA Phase2utilizedacompletelynew corecompressordesignstrategy andleveraged lessons For both1-and2-stageconfigurations,detaileddatawere taken at97%designspeed,acquiring N ASA testedthefirsttwo stagesusingSO K.L. Suder&J.D. Heidmann NASA ERAcore hot-sectiontechnology development efforts A researchinstrumentationtoinvestigate theloss O) nitrogenoxides(NO A high-pressure compressor in order to A high-pressurecompressorinorderto x ) below Committee ASA tested the first ASA testedthefirst

ASA facility as N ASA -

Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3 increased turbinebladeinlettemperature T Figure 3.26. Paper GT2010–22361. Work oftheU.S.Government.) An assessmentof theimpactofemerging high-temperature materialsonengine cycle performance. ASME development toincreaseT increase inengineOPRbyworking onthecompressortechnologiesand(2)CMCmaterial fuel burn areillustratedbythesystemstudyresultsshown inFigure3.26(Tong, 2010). challenge forincreasingOPRandT 2. 1. temperatures andjetvelocities, whichincreasenoiseandaddweight. ity concernsnearairports.Specifically, NO set. Sincethen,emissionsstandardshave become even morestringentbecauseoflocalairqual- revisions totheemissionsregulations andincludedthemeetingoftheseregulations intheirgoal emphasis onemissions.Itwas notedearlierthattheEnergy EfficientEngineProjectanticipated pressures andtemperatures,whichencouragesNO with high-power-density, highlyefficientcoresarethatthey resultin(1)highercombustor inlet weight associatedwiththelarger diameterUHBengines. The technicalchallengesassociated UHB enginestobeinstalledunderthewing,but thisalsocontributes tothereduceddragand 3. technology, NO

In thefollowing sectionstheresultswillbedivided intotwo elements:(1)onethataddresses One oftheconstraintsonever-increasing OPRandT The approachisto Maximize engineOPRandturbineinlettemperature,T diameter, andincreasepower density toenablehigh-BPRengines Select N a. weight by compression systemsandEBCcoatingsareexploited. Interact withtheU.S.DepartmentofDefensetoinsureN c. b. Developing integrated ceramic-matrixcomposite(CMC)high-pressureturbine(HPT) Developing anddemonstratinglow-weight durableoxidenozzles Maximizing HPCloadingandperformance, vanes andbladesthatareintegrated withenvironmental barriercoatings(EBCs), ASA-unique capabilitiestoincreasethermalefficiency (fuel burn), minimizecore Specific fuelconsumption(SFC)reduction duetoincreased overall pressureratio (OPR)and x emissionsincreasedramaticallywithincreasingOPRandcycle temperature. Improvement ofaeropropulsion fuelefficiencythrough enginedesign 4 andreducecoolingflow. Thebenefitsofthesetechnologiestoreduce 4 asshown inFigure3.27.For agiven level ofcombustor 41 asafunctionofreducedcoolantflow (From Tong, M. T. 2010. x emissionsareamajorconcern,andthispresents x productionand(2)higherengineexhaust 4 forreducedfuelburn istheincreased 4 , andreducecoolingflow and ASA-unique capabilitiesin 75

Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3 n Figure 3.28. Figure 3.27. 0414. Work oftheU.S.Government.) ation project’s propulsiontechnologyphaseIoverview andhighlightsofaccomplishments. AIAA 2013– emissions. (FromSuder, K.L.,J.Delaat,C.Hughes,etal.,2013.N 76 to maintainorreduceNO reduction ofcoolingflow intheHPT vane additionallyreducesNO developed to allow forhigherenginetemperaturesandreduced coolingflow requirements. The area, high-temperatureCMCcombustor, turbinevane, andenginenozzlecomponentsarebeing of materialsdevelopment, compressortesting, andcomputationalanalysis.Inthematerials out-of-house laboratories. been currentlydemonstratedand totestthesemodelsinarelevant environment inN of CMCcomponentsthroughdesign andfabrication oflarger, morecomplex modelsthan have usage for combustor dilution jets. The plan is to advance the technology readiness (TRL) level the combustor exit temperatureforagiven turbinerotorinlettemperatureandfreeingcoolant The strategy istoadvance combustor mixingtechnologyinconcertwithOPRand T N ASA isaddressingthesechallengesofhigherOPRand T K.L. Suder&J.D. Heidmann Trade space between engine overall compressor pressure ratio and nitrogen oxide (NO ASA anti-vortex filmcoolingconceptwithbifurcated exits. x alongwiththrust-specificfuelconsumption. ASA environmentally responsibleavi- x 4 emissionsbyreducing throughacombination 4 advances ASA and x ) Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3 References aircraft engineefficiency. ment andresearchdevelopment basedon the underlyingphysics ofjetpropulsionandimproved contributions and how they have been achieved through a consistent focus on concept develop - pioned byGRCanditsresearchstaff. This chapterhassummarizedahigh-level view ofthese ments envisioned inthenext decadesthroughcomponent, engine,andaircraftconceptscham- engine specificfuelconsumptionhasbeenreducedbymore than50%,withsimilarimprove- research programs. Through thispartnershipwithindustry, thefuelburn perpassenger-mile and has playedaleadingroleinadvocacy fornew enginearchitecturesinfundamentalandapplied sively throughthedevelopment ofturbojet,turbofan, andpotentialunductedfan concepts,GRC engine industry. Beginning withtheearlyreciprocatingenginespropellers andprogres- physics insightandcomputationalfluiddynamics validation inpartnershipwiththeaircraft opment, analytical tool and model development, and research investigating fundamentalflow greatly tothisimprovement throughfullenginetesting,componenttestinganddevel- dramatic improvement inaircraftfuelefficiency andperformance. TheCenter hascontributed The historyoftheN 3.7 versity, andotherU.S.FederalGovernment Agencies. Group, whichcontinuestodayasaforumforbettercollaborationbetweenN that weredeveloped undertheauspicesofN cacy of this research topic was strengthened through a series of turbomachinery white papers tip, endwall, andleakageflows becomedominant sourcesoflossintheenginecore. Theadvo- engine coresincreaseinOPRandreducesizetoenablefurtherincreasesturbofan BPR,the better understandingandmitigation ofturbomachinerytipclearanceandendwall flow losses. As focusing onenablingcontinuedimprovements toengineOPRandthermalefficiency througha high-temperature water-laden gas. robust EBCsforCMCcomponentstoprotecttheceramicmaterialfromerosive effects of materials improvements toward reducedfuelburn engines.Development continuesonproviding bined cooling/materialsproblem continues thehistoricaltrendofsynergistic turbinecoolingand may needtode-emphasizeinternalcoolingandrelymoreonexternal filmcooling. Thiscom- their reducedthermalgradientcapability, CMCsandotherceramic-basedturbinecomponents bine materials,whichhave uniqueconstraintsforcoolingcomparedtometalparts.Becauseof cooling flows. Arecentareaofresearchdelves intotheoptimizedcoolingofceramic-basedtur (Fig. 3.28),whichcanoffer dramaticimprovements infilm-cooling effectiveness andreduced cepts, includingideassuchasan“antivortex” row offilmcoolingholeshaving bifurcated exits Ameri, Ali A. 2009.N Adamczyk, J.1984.Modelequationforsimulatingflows inmultistageturbomachinery. N Ballal, D.,andJ. Zelina. 2003.Progressinaero-engine technology, 1939–2003. AIAA 2003–4412. Bakhle, M. A., T. S.R. Reddy, andR.M.Coroneos.2014.Forced responseofafan withboundary layerinlet Bakhle, M. A., T. S. R.Reddy, G.P. Herrick,etal.2012. Aeromechanics analysisof a boundarylayer Arend, D.J.,G. Tillman, and W. F. O’Brien.2012.Generationafternext propulsorresearch:robust design

distortion. AIAA Paper 2014–3734. ingesting fan. AIAA 2012–3995. for embeddedenginesystems. AIAA 2012–4041. The N The N Summary ASA SubsonicFixed Wing Projecthasrecentlyinitiatedanumberofresearchawards ASA GlennResearchCenteriscontinuingtodevelop advanced turbinecoolingcon- Improvement ofaeropropulsion fuelefficiencythrough enginedesign ASA R ASA GlennResearchCenter(1943topresent)coincideswithaneraof O T OR 37CFDCDEvalidation: Glenn-HTcode. AIAA 2009–1060. ASA-led Turbomachinery Technical Working ASA, industry, uni- ASA TM–86869. 77 - Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3 78 Celestina, M.L.,J.C.Fabian, andS.Kulkarni. 2012.N Celestina, M.L.,andR. A. Mulac.2009. Assessment ofStage35with APN Bullock, R.O.,andI. A. Johnsen.1965. Aerodynamic designofaxialflow compressors.N Bowles, M.D.2010. The “Apollo” ofaeronautics:N Berdanier, R. A., andN.L.Key. 2015. An experimental investigation oftheflow physics associatedwith Schulz, Rutherford, D.2012.Overturning conventional wisdom onaircraftefficiency trends. TheInternational Reid, L., and R. D. Moore. 1978. Design and overall performance of four highly loaded, high speed inlet Ciepluch, C.C.,D. Y. Davis, andD.E. Gray. 1987.ResultsofN Chima, R. V. 2009. SWIFTcodeassessmentfortwo similartransoniccompressors. AIAA 2009–1058. Prahst, P. S.,S.Kulkarni, andK.H.Sohn.2015.Experimental resultsofthefirsttwo stagesofan advanced Koff, B.L.1991.Spanning theglobewithjetpropulsion. AIAA 91–2987,1991. Katz, J.2016.Highresolutionmeasurementsoftheeffects oftipgeometryonflow structureandturbulence Herrick, G.P., M.D.Hathaway, andJ.-P. Chen.2009.Unsteadyfullannulussimulationsofatransonicaxial Hendricks, E.S.,J.Berton, W. J.Haller, M. T. Tong, andM.D.Guynn.2013. Updatedassessmentsofan Hathaway, M. D., R. M. Chriss, J. R. Wood, Hathaway, M.D., T. H.Okiishi,K.L.Suder, etal.1987.Measurementsoftheunsteadyflow fieldwithin Hathaway, M.D.,J.B.Gertz, A. H.Epstein,etal.1986.Rotorwake characteristicsofatransonicaxialflow Hah, C.2009.Large eddysimulationoftransonicflow fieldinN Giel, P. W., G.J. Van Fossen, R.J.Boyle, etal.1999.Bladeheattransfermeasurementsandpredictionsin Florea, R. V., C.Matalanis,L. W. Hardin, etal.2012.Parametric analysisanddesignforembeddedengine Florea, R. V., R.Reba,P. R. VanSlooten, etal.2009.Preliminarydesignforembeddedenginesystems. Ferrar, A. M., W. F. O’Brien, W. F. Ng, R. V. Florea,andD.J. Arend. 2009. Active controlofflow- inserpen Epstein, A. H.2014. Aeropropulsion forcommercialaviation in the twenty-first century andresearchdirec- Durbin, P. A., andB. A. PetterssonReif.2001.Statistical Theory andModelingfor Turbulent Flows . New Dunlap, S.F. 1991. Technology transferinU.S.aeronautics:Government supportoftheU.S.commer Dunham, J.,ed.1998.CFDvalidation forpropulsionsystemcomponents. AGARD–AR–355. Domke, B.2007. The GE36UnductedFan (UDF)usedtwo contra-rotatingpropellers witheightblades Dawson, V. P. 1991. Engines and innovation: Lewis Laboratory and American propulsion technology. Davis, D. Y., andE.M.Stearns.1985.Energy efficientengine:flightpropulsionsystemfinaldesignand Conner, M.2001. Hans Von O hain: elegance inflight.Reston, VA: AIAA. thermal barriercoatings. Aerosp.Sci. Technol. 7:73–80. N N end wall lossesandlarge rotortipclearancesasfoundintherearstagesofahighpressurecompressor. dom-aircraft-efficiency-trends (accessed August 31,2016). Council onClean Transportation blog,http://www.theicct.org/blogs/staff/overturning-conventional-wis- stages foranadvanced, high-pressure-ratiocorecompressor. N overall pressureratiocompressorresearch—pre-testCFD. AIAA 2012–4040. transonic corecompressorunderisolated andmulti-stageconditions. ASME Paper GT2015–42727. 11AI21A fortheperiodofJune6,2011–July31,2016. in thetipregion ofarotorblade.FinalReportforN compressor stage. AIAA 2009–1059. open rotorairplaneusingadvanced bladedesigns. AIAA 2013–3628. the N the statorrow ofatransonicaxial-flow fan: Part II—resultsanddiscussion. ASME Paper 87–GT–227. fan. AIAAJ. 24:1802–1810. a transonicturbinecascade.N inlets. AIAA Paper 2012–3994. AIAA 2009–1131. tine inletsforblendedwing-bodyaircraft. AIAA 2009–4901. tions needed.AIAAJ. 52:901–911. York, NY: John Wiley &Sons. cial aircraftindustry. Darby, PA: DianePublishing. each. http://www.b-domke.de/AviationImages/Rarebird/0809.html (accessed April 28,2017). N analysis. N Propul. Power 3:560–568. ASA e-book,http://www.nasa.gov/connect/ebooks/aero_apollo_detail.html ASA/CR—2015-218868. ASA SP–4306. K.L. Suder&J.D. Heidmann U., C. Leyens, K. Fritscher, ASA low-speed centrifugal compressorflow field.J. Turbomach., 115:527–542. ASA CR–168219. ASA/TM—1999-209296. et al. 2003. Some recent trendsin research and technology of advanced et al. 1993. Experimental and computational investigation of ASA’s aircraftenergy efficiency program,1973–1987. ASA Grant/Cooperative Agreement NumberNNX- ASA environmentally responsibleaviation high ASA Rotor37. AIAA 2009–1061. ASA’s energy efficientengineprogram.J. ASA TP–1337. ASA. AIAA 2009–1057. (accessed August 31,2016). ASA SP–36.

-

Downloaded By: 10.3.98.104 At: 09:22 03 Oct 2021; For: 9780203119969, chapter3, 10.1201/b20287-3 Skoch, G. J., P. S.Prahst,M. P. Wernet, et al . 1997.Laser anemometer measurements of the flow fieldin Skoch, G.J.,andR.D.Moore.1987.Performanceoftwo 10-lb/seccentrifugal compressorswithdif- Shetty, K.I.,andR.J.Hansman.2012.Currenthistoricaltrendsingeneralaviation intheUnitedStates. Strazisar, A. J., J. R. Wood, M. D. Hathaway, Strazisar, A. J.1985.Investigation offlow phenomenainatransonic fan usinglaseranemometry. J. Eng. Tillman, G., L. W. Hardin, B. A. Moffitt, Suder, K.L., T. H.Okiishi,M.D.Hathaway, etal.1987.Measurementsoftheunsteadyflow fieldwithin Suder, K.L.,J.Delaat, C.Hughes,etal.2013.N Suder, K.L.1996. Experimentalinvestigation oftheflowfieldina transonic, axialflowcompressor with Van Zante,D.E.2013. The N U.S. Government. 1991. Technology transferinU.S.aeronautics: .S. Government supportoftheU.S. Tong, M. T. 2010. An assessment of the impact of emerging high-temperature materials on engine cycle Wood, J.R., A. J.Strazisar, andP. S.Simonyi. 1987.Shockstructuremeasuredinatransonicfan usinglaser Volino, R.J.2016.Experimentalandcomputationalinvestigation ofunsteadyendwall andtipgap flows in Van Zante,D.E.,F. Collier, A. Orton,etal.2014.Progressinopenrotorpropulsors:theFAA/GE/N Van Zante,D.E.,J. Adamczyk, A. J.Strazisar, etal.2002. Wake recovery performance benefitinahigh- Van Zante,D.E.,andK.L.Suder. 2015.Environmentally responsibleaviation: propulsionresearch toena-

a 4:1pressureratiocentrifugal impeller. N (AVSCand AIAA–87–1745). OM–TR–87–C–21 ferent bladeandshroudthicknessesoperatingover arangeofReynolds numbers.N edu/bitstream/handle/1721.1/72392/ICAT%20REPORT%20SHETTY.pdf (accessedMay2,2017). Report No.ICAT–2012–6. MITInternationalCenterfor Air Transportation (ICAT). https://dspace.mit. Power—T. ASME107:427–436. GT–342). 87–GT–226. the statorrow ofatransonic axial-flow fan: Part I—measurementandanalysistechnique. ASME Paper pulsion technologyphaseIoverview andhighlightsofaccomplishments. AIAA 2013–0414. Reserve University, Cleveland, OH. respect tothedevelopment ofblockage andloss. Ph.D. N Thesis ( axial-flow fan rotor. N commercial aircraftindustry. Darby, PA: DianePublishing. performance. ASME Paper GT2010–22361. propulsion. Invited Paper tothe49th AIAA Aerospace SciencesMeeting,Orlando,FL. anemometry. AGARD–CP–401. gas turbinepassages.FinalReportforN open rotortestcampaign.Aeronaut. J. 118:1181–1213. speed axialcompressor. J. Turbomach. 124:275–284. ble fuelburn, noise,andemissionsreduction.ISABE2015–20209. Rotor Test Campaign. AIAA 2013–0414. Improvement ofaeropropulsion fuelefficiencythrough enginedesign ASA TP–2879. ASA Environmentally Responsible Aviation Project/General ElectricOpen ASA Interagency Agreement NNC11IA11I. et al. 2011. System-level benefits of boundary layer ingesting et al.1989.Laseranemometermeasurementsinatransonic ASA TM–107541 (ARL–TR–1448and ASME Paper 97– ASA environmentally responsibleaviation project’s pro- ASA TM–107310), Case Western ASA TM–100115 ASA 79