“Materials Aspects of Turboelectric Aircraft Propulsion ...€œMaterials Aspects of Turboelectric...
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“Materials Aspects of Turboelectric Aircraft Propulsion” Presenter: Gerald Brown Coauthors: Hyun Dae Kim and James Felder Abstract: The turboelectric distributed propulsion approach for aircraft makes a contribution to all four “corners” of NASA’s Subsonic Fixed Wing trade space, reducing fuel burn, noise, emissions and field length. To achieve the system performance required for the turboelectric approach, a number of advances in materials and structures must occur. These range from improved superconducting composites to structural composites for support windings in superconducting motors at cryogenic temperatures. The rationale for turboelectric distributed propulsion and the materials research and development opportunities that it may offer are outlined. https://ntrs.nasa.gov/search.jsp?R=20090042355 2020-04-27T15:20:09+00:00Z
Transcript of “Materials Aspects of Turboelectric Aircraft Propulsion ...€œMaterials Aspects of Turboelectric...
“Materials Aspects of Turboelectric Aircraft Propulsion”Presenter: Gerald Brown
Coauthors: Hyun Dae Kim and James Felder
Abstract:The turboelectric distributed propulsion approach for aircraft makes a contribution to all four “corners” ofNASA’s Subsonic Fixed Wing trade space, reducing fuel burn, noise, emissions and field length. To achieve thesystem performance required for the turboelectric approach, a number of advances in materials andstructures must occur. These range from improved superconducting composites to structural composites forsupport windings in superconducting motors at cryogenic temperatures. The rationale for turboelectricdistributed propulsion and the materials research and development opportunities that it may offer areoutlined.
https://ntrs.nasa.gov/search.jsp?R=20090042355 2020-04-27T15:20:09+00:00Z
National Aeronautics andSpace Administration
Materials Aspects of Turboelectric Aircraft Propulsion
PresenterPositionOrganizationCoauthors
Gerald V. BrownSenior Research EngineerGRC Structures & Materials Div.Hyun Dae Kim, James Felder
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Materials Aspects of Turboelectric Aircraft Propulsion
Presenter Gerald V. BrownPosition Senior Research EngineerOrganization .^ GRC Structures & Materials Div.Coauthors
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The Turboelectric Approach
The turboelectric approach does not replace the turbine engines or the fans,rather it enables them to be located and optimized independently for thegreatest aircraft benefit.
The incentive for higher thermodynamic and propulsive efficiencies remains.
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N3-X Distributed TurboelectricPropulsion System
SuperconductingWing-tip mounted continuoussuperconductingturbogenerators
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Low velocity core exhaustreduces noise.
- ri
Forward and aft fan noiseIs shielded by airframe.
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BENEFITSLarge core engines with low TSFCdrive superconducting generators.
Multiple motor-driven fans ingest •'`boundary layer & give high bypassratio for low fuel burn and emissions.
Electric power from generatorsis distributed to multiple fans.
Fans fill in center body waketo reduce drag, fuel burn andemissions.
Electric power distribution tomultiple fans is more efficientand lighter than mechanical.
Upper surface suction increases liftcoefficient at TO & delays separation.
High-speed core engineshave fewer turbine stagesthan direct fan-drive cores.
Small diameter core engine inletsare acoustically treatable.
THE TURBOELECTRIC APPROACH CONTRIBUTES TO EVERY CORNER OF THE SFW TRADE SPACE
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OUTLINE
q Rationale for turboelectric distributed propulsionq Turboelectric componentsq Selected areas of materials needs and opportunities
• Engine materials for high thermodynamic efficiency andlight weight- - an ongoing need
High-temp disks, blades & coatings, etcMaterials to reduce engine weight
• Low-AC-loss conductors for motor and generator stators• Composite formers, structure and torque tubes for motors
and generators• High-performance cryocoolers• High-performance cryogenic power converters (inverters)• Conformal liquid hydrogen tankage• Flight weight superconducting transmission lines
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N2A
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Higher Bypass Ratio & BoundaryLayer Ingestion Save Fuel
Compared to N2A, N3 -X has:Twice the fan area and bypass ratio (BPR 20 vs. 10)Ingestion of center body boundary layer10 to 20% lower fuel burnReduced noise from core engine and fans (FPR~1.35)Engine-out thrust symmetryLower throttle-dependent pitching moment
* Thrust requirement is 30,000 lbf at aerodynamic design point of 31,000 feet, MN 0.8, ISA.Thrust requirement is 108,000 lbf at rolling take-off condition at sea level, MN 0.25, and ISA+27.
“Turboelectric Distributed Propulsion Engine Cycle Analysis for Hybrid Wing-body Aircraft”, James L. Felder, Hyun Dae Kim and Gerald Brown,AIAA-2009-1132, presented at 47th AIAA Aerospace Sciences meeting in Orlando, FL, Jan 7, 2009.
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Tur ven
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Distributed Turboelectric Propulsion System Requires Cryogenicand Superconducting Components for Light Weight
superconducting generator
Superconducting transmission linesbetween generators and motors
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Superconducting motorsto drive propulsive fans
Cryogenic Inverter forvariable speed fans
The temperatures needed for superconductingmachines and the cryocoolers or LH 2 to producethem are no strangers to the space side of NASA.
Cryocooler(s) forcryogenic components
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Fully Superconducting Motor or Generator
SuperconductingAC stator coils
packs
Materials needs and opportunities for motors and generators:Composite formers and containment for rotor
Composite torque tubesLow-loss super- or normal- conductors for stator windings
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Cross section of fourcoil packs ready forstructural elements
One of four rotor coil packs
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Composite Rotor Formers, Structural Supportand Torque Tubes
• Lightweight rotor structure, centrifugalcontainment and torque transfer elementsare needed.
• Current technology uses vacuumimpregnation of coils in a metallic structure
• Lower density composite substitutes musthave appropriate thermal expansioncoefficients and good thermal conductivity
• ―Torque tubes‖ are required to transfer
torque between cold region and warm partswith low heat leak.• Composites and titanium compete here• High strength and stiffness but lowthermal conductivity is desired for torquetubes.
R q WUDQVIHU q• Power density of superconducting motorsand generators:
SOA: 6 hp/lbGoal: >30 hp/lb
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Low-temperature superconductor - NbTi
q YBCO ribbon has high AC lossesq Air Force striated ribbon reduced loss, but
not enough for our needq New ORNL wrap-around YBCO wire may
have promise
ORNL Structural, Single-crystal, FacetedFibers (SSIFFS) (2009 IR-100 Award)
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Low-AC-Loss Superconductorsq Must reduce hysteretic, coupling and
eddy-current lossesq Superconducting machines require fine,
twisted superconductor filaments in ahigh-resistance matrix to reduce losses
q Complex fine-filament composites weredeveloped for low-temp superconductorsincluding some brittle inter-metallic ones
q Critical current improvement alwayssought from flux pinning improvements
q MgB2 is more easily made with finefilaments and twist but requires loweroperating temperature than YBCO*.
q High resistance matrix is an issue forMgB2
q Phase I SBIR made progress (Hyper TechResearch)
q SOA filament diameter : 50 µm. Goal: < 10µm
* Yttrium barium copper oxide
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Low-AC-Loss Normal Conductors
q Room temperature resistance of normalAl or Cu is too high but is two orders ofmagnitude lower near LH 2 temperature
q But the AC losses can be nearly as badas for superconductors
q As for superconductors, fine, twistedfilaments and a high resistance matrix arerequired for Al or Cu operating at LH 2
temperature
q High-purity, fine-filament Al compositeconductors were produced by Air Forcefor use at LH 2 temperature*
q High-frequency performance not pursuedq Matrix alloy (Al-Fe-Ce) constituents must
not diffuse into pure aluminum
Conductor with 61 pure Al filaments in ahigh-resistance Al-Fe-Ce matrix for LH 2 roperation (AFRL). Precursor strand forconductor with 2989 filaments.
q Nanotube conductors at roomtemperature are under study for aircraftwiring applications, but present DCresistivity is over two orders ofmagnitude too high for motors
*“The origin and future of composite aluminum conductors”, Oberly, C.E.; Ho, J.C.; IEEETransactions on Magnetics, Volume 27, Issue 1, Jan 1991 Page(s):458 - 463
Carbon nanotube multifilamentconductor for high frequencyapplications at room temperature,(SBIR for Air Force)
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Reverse Brayton refrigeration cycle
Recuperator needs high lateral thermalconduction and low longitudinal conduction.Opportunity for nanotube mats, etc?
Recuperator stack* Recuperator plate** “A Recuperative Heat Exchanger for Space-Borne Turbo-Brayton Cryocoolers”,R. W. Hill, M. G. Izenson, W. B. Chen and M. V. Zagarola
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State-of-the-Art-Breaking CryocoolerReverse-Brayton, Stirling and pulse-tube
coolers are candidatesPhase I SBIR produced preliminary design
of reverse Brayton cryocooler with 1 /6 th
the weight of existing coolers and noloss in efficiency (Creare)
High performance recuperator is requiredLight-weight turbo-compressor is requiredCooler SOA is 30 lb/hp-input.Goal is 5 lb/hp-input.
Reverse-Braytonwarm module
(prelim. design)
Reverse-Braytoncold module
(prelim. design)
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Cryogenic Power Converter (Inverter)
• Changes DC electrical power to ACpower for variable speed motor drive
• Room temp inverters are 95% efficientwith power density up to 10 hp/lb
• 99.8% efficiency expected atcryogenic temperatures
• Power density goal: 20 hp/lb or more
• Some cryogenic inverter work hasbeen done
• 2 kW unit to be delivered to NASA(by MTECH Laboratories, Inc.)
• Semiconductor parts for cryogenicuse are selected from standard parts
Higher efficiency at low temp from:– Lower ―on resistance‖
– Faster switching
High heat transfer to cryo fluids is possibleNew semiconductors especially for cryo
temperaturesPassive components can be greatly improvedExpansion coefficient compatibility important
to avoid brittle failure
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SOA numbers: 5 W/m loss, 10 kg/mTarget numbers: Mass goal: 5 kg/mTerminations & interconnects may be issues
Superconducting transmission lines for ground-basedelectric grid should be further developed for flight weight.
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Flight-Weight Superconducting Transmission Lines
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Typical LH 2 Tanks Conformal LH 2 Tanks
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Light-Weight, Conformal Liquid Hydrogen Tanks
Three ways LH 2 might be used:q Jet-fueled aircraft (1) - - Replace cryocoolers
with tanked LH 2 . Use GH 2 as fuel(LH2 : ~8% of total fuel energy)
q Jet-fueled aircraft (2) - - Size cryocoolers forcruise. Tanked LH 2 for excess cooling at TO(LH2 < 1 % of total fuel energy)
q LH2-fueled aircraft - - Portion of fuel coolscryogenic components before being burned.(Zero Co2 aircraft)
q No current NASA activity for aircraft in thisarea
q NASA carbon-fabric-reinforced compositesfor composite tanks reduced tankpermeability to He by 70%. H 2 permeabilitydata needed.
q Conformal tanks could use of odd-shapedvolumes in hybrid wing body
q Available LH2 would reduce or eliminatecryocooler requirement
q More AC loss can be tolerated in motorsand generators
q Use of pure normal conductors and/orMgB2 becomes more favorable with LH 2
N.B. The use of LH2 is only a possible option. It is NOT requiredto implement turboelectric propulsion!
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Ships, Trains & Cars Already Benefit From Why not Airplanes?Hybrid Electric Power Systems
Advances in materials can help make this possible.
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References1. ― HTS Machines as Enabling Technology for All - Electric Airborne Vehicles ‖ , Philippe J. Masson, Danielle S. Soban, Gerald V. Brow n and Cesar
A. Luongo, Superconductor Science & Technology, 20 (2007) 748–756.2. ― Hybrid Wing/Body Cruise Efficient Short Take -Off and Landing Transport Concept Using Distributed Propulsion System ‖ , by Hyun Da e Kim, Q q6\VWHP" qq E\
Gerald V. Brown, and James L. Felder, presented to the International Powered Lift Conference, London, July 22-24, 2008.3. ―Turboelectric Distributed Propulsion Engine Cycle Analysis for Hybrid Wing -body Aircraft ‖ , James L. Felder, Hy un Dae Kim and Gerald q .LP q DQG q q
Brown, AIAA-2009-1132, presented at 47 th AIAA Aerospace Sciences meeting in Orlando, FL, Jan 7, 2009.4. ‖ Next Generation More -Electric Aircraft: A Potential Application for HTS Superconductors ‖ , Cesar A. Luongo,, Philippe J. Masson, Taewoo
Nam, Dimitri Mavris, Hyun D. Kim, Gerald V. Brown, Mark Waters, David Hall, Applied Superconductivity Conference 2008, Chicago, IL.
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6. ― Review of high power density superconducting generators: Present state and prospects for incorporating YBCO windings ‖ , ,Paul N.Barnes,Michael D. Sumption and Gregory L. Rhoads, Cryogenics, Vol 45, Issues 10-11, Oct-Nov 2005, Pgs 670-686.
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