Aircraft Design for Reduced Climate Impact

2011·6.3 MB·English

by  Emily Dallara

AIRCRAFT DESIGNFORREDUCED CLIMATEIMPACT
A DISSERTATION
SUBMITTEDTOTHEDEPARTMENT OFAERONAUTICS AND
ASTRONAUTICS
ANDTHE COMMITTEE ON GRADUATESTUDIES
OF STANFORD UNIVERSITY
IN PARTIALFULFILLMENT OF THEREQUIREMENTS
FORTHEDEGREEOF
DOCTOROFPHILOSOPHY
EmilySchwartzDallara
February2011
2011byEmilyDallara.AllRightsReserved.
Re-distributedbyStanfordUniversityunderlicensewiththeauthor.
Thisdissertationisonlineat:http://purl.stanford.edu/yf499mg3300
ii
IcertifythatIhavereadthisdissertationandthat,inmyopinion,itisfullyadequate
inscopeandqualityasadissertationforthedegreeofDoctorofPhilosophy.
IlanKroo,PrimaryAdviser
IcertifythatIhavereadthisdissertationandthat,inmyopinion,itisfullyadequate
inscopeandqualityasadissertationforthedegreeofDoctorofPhilosophy.
JuanAlonso
IcertifythatIhavereadthisdissertationandthat,inmyopinion,itisfullyadequate
inscopeandqualityasadissertationforthedegreeofDoctorofPhilosophy.
MarkJacobson
ApprovedfortheStanfordUniversityCommitteeonGraduateStudies.
PatriciaJ.Gumport,ViceProvostGraduateEducation
Thissignaturepagewasgeneratedelectronicallyuponsubmissionofthisdissertationin
electronicformat.Anoriginalsignedhardcopyofthesignaturepageisonfilein
UniversityArchives.
Abstract
Commercialaviationhasgrownrapidlyoverthepastseveraldecades. Aviationemis-
sionshavealsogrown,despiteimprovementsinfuelefficiency. Theseemissionsaffect
theradiativebalanceoftheEarthsystembychangingconcentrationsofgreenhouse
gasesandtheirprecursorsandbyalteringcloudproperties. In2005,aircraftopera-
tionsproducedabout5%oftheworldwideanthropogenicforcingthatcausesclimate
change, andthisfractionisprojectedtorise.fl] Changesinaircraftoperationsand
designmaybenecessarytomeetgoalsforlimitingfutureclimatechange.
A frameworkispresented for assessingthecomparativeclimateimpactsoffu-
tureaircraftduringconceptualdesignstudies. Alinearclimatemodelestimatesthe
temperaturechangecausedbyemissionspecieswithvaryinglifetimesandaccounts
forthealtitude-varyingradiativeforcingsproducedbyNOxemissionsandaviation
inducedcloudiness. Theeffectsofdesigncruisealtitudeon aircraft fuelconsump-
tionandNOxemissionratesaremodeledsimultaneouslybyintegratingtheclimate
modelintoanaircraftdesignandperformanceanalysistool. Theaveragetempera-
tureresponsemetricaggregatesthelifetimeclimatechangeimpactsfromoperating
afleetofparticularaircraft. Lastly,uncertaintyquantificationstudiesareperformed
todeterminethelevelofconfidenceinestimatesofrelativeclimateperformanceof
competingaircraftconfigurations.
Aircraftclimatechangemitigationstrategiesareinvestigatedwiththisframework.
Withoutapplyingadditionaltechnologies,designingaircrafttoflyatMach0.77and
25,000-31,000ftaltitudeenables10-35%reductionsinclimateimpacts (and1%in-
creasesinoperatingcosts) comparedwithmoreconventionaldesignsthatcruiseat
Mach0.84,39,000-40,000ftaltitude. Thisresearchalsomodelstheperformanceof
iv
aircraftthatadoptpropfanengines,naturallaminarflow,biofuels,lowNOxcombus-
tors,andoperationalcontrailavoidance. Aircraftflyingbelowfuel-optimalaltitudes
incurafuelburnpenalty,butpropfanandlaminarflowtechnologiescanoffsetthese
penaltiesandproducelargefuelsavings. Thesetechnologiesenablecollectiveclimate
impactreductionsof45-75%simultaneouswithtotaloperatingcostsavingsrelative
to aconventional, baselinetechnology, minimum cost aircraft. Uncertaintyquan-
tificationstudiesdemonstratethatsignificantrelativeaveragetemperatureresponse
savings canbeexpectedwiththesestrategiesdespitelargescientificuncertainties.
Designstudiesillustratetheimportanceofincludingnon-C02effectsinanaircraft
climatemetric: ifaircraftaredesignedtominimizeC02emissions,insteadofthetem-
peraturechangecausedbyallemissions,thenpotentialsavingsarehalved. Strategies
forimprovingtheclimateperformanceofexistingaircraftarealsoexplored,reveal-
ingpotentialclimateimpactsavingsof20-40%,tradedfora1-5%increaseintotal
operatingcostsandreducedmaximumrange.
Acknowledgments
Thisthesiswouldnothavebeenpossiblewithouttheguidanceandsupportofmany
people. Iowemydeepestgratitudetomyadviser,ProfessorIlanKroo. Heembraced
andsharedmypassionforenvironmentally-friendlyaircraftdesignandallowedme
thefreedomtodrivethedirectionofmyresearch. Hisinsightsandpracticalguidance
overthelastseveralyearshavehelpeddevelopedmyabilitytotacklenewchallenges
andwillhaveapositiveimpactonmeasImoveforwardinmycareer.
Mysincerethanksgotomembersofmycommittee,ProfessorsJuanAlonsoand
MarkJacobson,forreadingthisthesisandprovidingthoughtfulcomments. Professor
JohnWeyantcontributedsignificantly, bothbyservingasadefenseexaminerand
throughusefuldiscussionsabout climatechangemetrics. Additionalthanksgoto
ProfessorMargot Gerritsenforservingasmydefensecommitteechairperson. Our
workintheareaofclimatemetricsalsogreatlybenefitedfromthefeedbackofMIT
ProfessorIanWaitz. Lastly,IwouldliketothankSteveBaughcumfromtheBoeing
Companyformanyhelpfulconversations,particularlyintheareaofcontrailavoidance
strategies.
Ifeelvery fortunatetohave been apartoftheAircraft Design Group. Over
thepastseveralmonths,everymemberofthegrouphasprovidedmewithfeedback
andsupportthathelpedshapethisresearch. IgreatlyvaluetheexperiencesIhave
sharedwithourformationflightteam: GeoffBower, JiaXu, Tristan Flanzer, and
AndrewNing. ManyotherfriendsonbothsidesoftheBayhavemademyyearsat
Stanfordamongthemostenjoyableinmylife. SpecialthanksgotoNoelBakhtianfor
bringingtheperfectamountoflevitytoourgraduateschoolexperiencesinEngland
andCalifornia.
vi
Finally, Iwould not bein thepositionthat I am today withoutthe loveand
supportofmyentirefamily. ThankstomyDadforalwaysbelievinginme,especially
whenIdidn't believeinmyself. ThankstomyMomforhertirelessdevotionand
sacrificeintakingcareofmybrothers,sister,andme. Thankstomyhusband,Chris,
forgivingmylifebalanceandmeaning(andforproofreadingthisentiredocument).
Thisthesisisdedicatedtohim.
vii
Contents
Abstract iv
Acknowledgments vi
] Introduction 1
1.1 GlobalClimateChange 1
1.2 AviationandtheEnvironment 4
L3 ContributionsandOutline 6
2 Aircraft ClimateImpacts 7
2J Introduction 1
2J2, AircraftEmissionsandClimate &
CarbonDioxide 11
2.2.2 WaterVapor 12
2.2.3 NitrogenOxides 12
2JLA SulfurOxides Li
2.2.5 SootParticles 14
2JLf5 AviationInducedCloudiness 14
2.3 AircraftEmissionsRegulations 16
2.4 EmissionsModeling 16
2.4.1 Fuel-ProportionalEmissions 17
2.4.2 N0VP3-T3Method 17
9.4.3 FuelFlowCorrelationMethods L&
2.5 ClimateImpactModeling 18
viii
i
3.5.1 GlobalClimateModels 13
2JL2 IntegratedAssessmentModels 19
2.5.3 LinearTemperatureResponseModels 2Q
3 ClimateChangeMetrics 21
3.1 Introduction 21
3.2 CommonlyUsedClimateMetrics 23_
3.2.1 MassofEmissions 23_
3.2.2 RadiativeForcing 23.
3.2.3 GlobalWarmingPotential 23
3.2.4 GlobalTemperaturePotential 24
3.2.5 DamagesandOtherEconomicMetrics 24
3.3 ClimateMetricforComparativeAircraftDesign 25.
3.3.1 DesiredMetricProperties 25
3.3.2 AverageTemperatureResponse 28
3.3.3 AlternativeAircraftDesignMetrics 34
4 AircraftDesignandAnalysisTools 35
4J Introduction 35_
4.2 ProgramforAircraftSynthesisStudies 35
4.3 OperatingCosts 3ii
4.4 VariableBypassRatioEngineModel 37
4.4.1 EnginePerformance 41
4.4.2 EngineGeometry 44
4.4.3 NacelleParasiteDrag 46
4.4.4 WeightEstimation 49
4.4.5 CertificationNoise 52
4.4.6 EngineMaintenanceandAcquisitionCosts 54
5 LinearClimateModelwithAltitudeVariation 55
5J Introduction 5Ji
5J2 Emissions 56
ix
i
5.2.1 CarbonDioxide,WaterVapor,Soot,andSulfateEmissionsIn-
dices 51
5.2.2 NitrogenOxideEmissionsIndex 57
5.3 RadiativeForcing 60
5.3.1 AltitudeVariation 01
5.3.2 Carbon Dioxide 64.
5.3.3 MethaneandLong-LivedOzone 64
5.3.4 Short-LivedSpecies 65
5.3.5 AviationInducedCloudiness 61
5.4 TemperatureChange 67
£l5 LimitationsoftheClimateModel 69_
5.6 UncertaintyQuantification 72
5.7 ComputingAverageTemperatureResponse 74
6 AircraftDesignStudies 78
6J Introduction 7&
6.2 AircraftOptimizationProblem 79
6.3 ResultswithBaselineTechnology 81
6.3.1 Single-ObjectiveResults 81
6^2 Cost-ClimateTradeoff 84
6.4 ResultswithClimateMitigationTechnologies 86
6.4.1 CO2ImpactReduction 86
6.4.2 NOyImpactReduction 94
6.4.3 AICImpactReduction 97
6.4.4 ComparisonofIndividualTechnologies 100
6.4.5 CombinationofTechnologies 102
6.4.6 AssessmentofClimateImpactUncertainty 104
6.5 AlternativeMetrics 109
6.5.1 ComparisontoResultswithC02-BasedMetric 109
6.5.2 ComparisontoResultswithOtherMetrics 110
6.6 Additional Studies 112
x
1