Post on 03-Jan-2017
Research Activities on Electric Aircraft and Hybrid Electric Propulsion System
Keiichi OKAI
Advanced Aeropropulsion Laboratory (AAL)
The University of Tokyo /
Japan Aerospace Exploration Agency
Europe-Japan SymposiumElectrical Technologies for the Aviation of the FutureMarch 26-27, 2015, EU Delegation, Tokyo, Japan
2
Long-term Research
(in “Sky Frontier Program”)Emission-Free Aircraft Concept & Technology Study
Ultra Low Emission and Highly Efficient Propulsion System
-Distributed and Electric Propulsion System
Technological issues to be pursued
Light-weight and robust (distributed) electric fan
Electric Generator system (FC-GT hybrid )
Fuel and Power feed distribution control
(2) Conceptual study of hybrid/electric propulsion
Aircraft Image Propulsion System Schematic
(1) FEATHER project(Flight-demonstration of Electric Aircraft
Technology for Harmonized Ecological
Revolution)
Maiden Flight (Nov. 2014)
Outline
JAXA’s unique electric propulsion
system
Validation of the new functions and
system performance
Flying laboratory toward electric
aircraft research
Small airplane for
FEATHER project
2Electric fan
JAXA conducts these research activities with University of Tokyo and Nihon University.
Contents
1.FEATHER Project
2.Hybrid/electric Propulsion systemfor the aviation
3. Summary
FEATHER project
Li-ion battery
http://www.aero.jaxa.jp/publication/event/pdf/event140918/poster07.pdf
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JAXA’s Electric Motor Glider
Wind tunnel testing
Electric motor
1. Japan’s first manned-electric aircraft demonstration program
/ Through the program JAXA acquired electric flight and MEA related systems research baseline.
1. Developed JAXA’s own electric motor for the test2. Two characteristic features in utilization of the
propulsion motor – four-fold motor / regenerative function
FEATHER project
Li-ion battery
http://www.aero.jaxa.jp/publication/event/pdf/event140918/poster07.pdf
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JAXA’s Electric Motor Glider
Original motor glider Diamond aircraft type HK36TTC-ECO
Width 16.33 m
Max. takeoff weight 850 kgf
Power source Li-Ion battery
Engine 60kW electric motor
Crew member 1 person
Specifications of the electric motor glider
Wind tunnel testing
Electric motor
System configuration
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indicatorsmeasurement system
display
Li-ion battery
warning & caution
fourfold electric motor(4 elements of motor connected in series)
reductiongear(1:3.16)
JAXA’s Electric Motor Glider
invertersfourfold electric motor
Electric propulsion system for FEATHER
Li-Ion battery
Capacity:75 Ah Total mass: 120kg Open circuit voltage: 128 V Maximum current: 750A(10C, 75s) Configuration: 32cells in series
Characteristics of electric motor
Permanent magnet type synchronous motor Fourfold motor (4 elements of motor connected
in series ) Regenerative function
Electric motor performance
Maximum output: 60 kW(4min.) Power density: 2.1kW/kg(w/o reduction gear) Efficiency: 94% or higher
Inverter IGBT Four individual inverters for four motor elements
Cooling Water cooling(Motor and inverters)
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http://www.aero.jaxa.jp/publication/event/pdf/event140918/poster07.pdf
fourfold motor
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Time
Thrust
Avoidance of complete thrust loss
Safety altitude
failure
× ✓
Time
✓✓
✓✓✓✓
Altitude
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Characteristic features of the electric propulsion system(1/2)
http://www.aero.jaxa.jp/publication/event/pdf/event140918/poster07.pdf
large
風力充電
Powere lever
空力抵抗
Driv
eR
GN
adjustable rage
(FEATHER)
Altitude
Distance
Concept of regenerative air brake
air flowcharge
air drag
electric power regeneration
small
conventional air brake
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The “Regenerative air brake system” is composed of a propeller, electric motor, inverter, battery and power lever.
The system enables us to not only charge the electric energy during descent but also control the angle of descent
without conventional air brake.
Characteristic features of the electric propulsion system(2/2)
Results of FEAHER project
We have succeeded in flight demonstrating as follows:
i. Avoidance of complete thrust loss in engine failure during climb by using the fourfold electric motor
ii. Regeneration of about 5kW electricity during descent by the motor and propeller
iii. Control of descent rate by the regeneration without conventional airbrake
iv. Continuous “regenerative soaring” free from descent in thermal condition
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1.FEATHER Project
2.Hybrid/electric Propulsion systemfor the aviation
3.Summary
Contents
2. Hybrid/electric propulsion technology (1/2)Motivation (Recognizing the potential of Liquid Hydrogen)
Okai, K., Long Term Potential of Hydrogen as Aviation Fuel, ICAO Environmental report 2010, pp. 164-167, 2010.
LH2 is (1) zero CO2 emission fuel, (2) Coolant and (3) Cryogenic superconducting medium.
JAXA has been conducting R&D activities on LH2 fueled turbojet propulsion system for Hypersonic flight.
Low Carbon Fuels
Turbo/Hybrid-electric Propulsion
Unconventional AirframeDistributed Propulsion
[1] ATAG(Air transport Action Group): Reducing emissions from aviationthrough carbon-neutral growth from 2020, 2013
TECHNOLOGY BENEFITS
TECHNOLOGY GENERATIONS
N+3 (2025) N+4Noise(cum margin rel. to Stage 4)
-71dB Better than -71dB
LTO NOx Emissions(rel. to CAEP 6)
-80% Better than -80%
Cruise NOx Emissions(rel. to 2005 best in class)
-80% Better than -80%
Cruise Fuel/EnergyConsumption(rel. to 2005 best in class)
-60% Better than -60%
NASA subsonic transport system level metrics[2]
N+3 values are referenced to a 737-800 with CFM56-7B engines.
IATA Technology Roadmap [1]Flightpath 2050 goal[3]
Flightpath 2050 targetCO2 emission perpassenger kilometer(rel. to Year 2000
level)
-75%
NOx emission(rel. to Year 2000level)
-90%
Aircraft noise level(rel. to Year 2000level)
-65%
[2] Bradley, M. K., and Droney, C. K.: Subsonic Ultra Green Aircraft Research Phase II: N+4 Advanced Concept Development, NASA/CR-2012-217556, 2012.[3] Flightpath 2050 Europe’s Vision for Aviation, European Commission, 2011.
2. Hybrid/electric propulsion technology(2/2)Target selection
Today’s high bypass DDTF and beyond
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By-pass ratio:
C
F
m
m
Small core engine generates large power to propel fan.
=> High bypass-ratio turbofan engines Limitation: α ~ 10
Direct-Drive Turbofan (DDTF)
Gear-Drive Turbofan(GDTF)
Open Rotor
?
C T
Compressor
Combustor
Turbine
Fm
CmCm)1(
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Direct-Drive Turbofan (DDTF)
Gear-Drive Turbofan(GDTF)
(GDTF)
Open Rotor ?Separation of fan from core engine
C T
Compressor
Combustor
Turbine
Multiple (electric-)fans powered by (one or small numbers of) core(s)
=> High (effective) bypass-ratio fan engine
Distributed propulsion
Power to propel the fan(s): Mechanical (Gear Drive) Compressed Air Electrical
Advantages and Challenges Potential for synergy effects in design integration
Distributed (semi-buried) distributed fans⇒Less Power required for propulsion (BLI* fans)⇒Extended and new flight control measure
(Relatively) large cores for effective thermal efficiencyEfficient Total Energy ManagementNoise shielding capabilityEnhanced reliability and redundancy with distributed propulsion Challenges are for:
Large-scale light weight fan moduleUltra-efficient core generatorEnergy efficient EMSLoss-less energy transmission
Highly efficient core
Distributed propulsor (fans)
Multi-fuels applicability
*BLI=Boundary Layer Ingestion
Technologies related to the FEATHER program
Magnetically Levitated Ducted Fan Being Developed as a Propulsor Option for Electric Flight (NASA)
NASA-TM-2005-213800
NASA Tip-Drive motor(to fit around propulsive fan)
1.Driving coils (point of action) on the outer shell
2.No need of iron core
(Large current variation; Relax physical limits)-> Small (relative) resistance loss
3.Energy recovery via LC circuit
2-1 High-power density electric motor for propulsion(1/2)- - Tip-drive motor concepts
US-Patent#7423405 Electromagnetic Rotating Machineby Okai, K. et al.
Other tip-drive motor concepts for aviation
High specific power motor is essential:
𝑃𝑜𝑤𝑒𝑟𝐷𝑒𝑛𝑠𝑖𝑡𝑦[𝑘𝑊
𝑘𝑔] ∝ 𝐻𝑡 × 𝐵𝑛× 𝑁
High rotation speed is not applicablefor large scale motor Superconducting motor
Adaptation of MgB2
Tcr=39[K]Cryogenic fuel has potential for
superconducting medium and coolant.(Maintaining superconductivity is crucial and important )
Tip drive motor
Luongo C.A., Masson, P. J., Nam, T., Marvis, D., Brown, G., Kim, H. D., Waters, M. and Hall, D., Next Generation More-Electric Aircraft: A Potential Application for HTS Superconductors, Applied Superconductivity Conference, 2008.
NASA-TM-2006-214481
2-1 High-power density electric motor for propulsion(2/2)Experimental approach to grasp engineering physics behind
【Features in the (original) motor configuration】1.Driving coils (point of action) on the outer shell; Infinity-shaped rotating coil
2.No need of iron core(Large current variation; Relax physical limits)-> Small (relative) resistance loss
3.Energy recovery via LC circuit Exp #1
Exp #2
Exp #3
Courtesy Dr. Kenya Harada (JAXA)
2-2 Potential of Fuel-cell Hybrid Gas turbine core (1/2)Various applications in aviation field as power source
HALE applicationPassenger aircraft0 1
SOFC/Reactor module characteristics
High Temp and High Pressure experimental setup
2-2 Potential of Fuel-cell Hybrid Gas turbine core (2/2) Configuration definition and data acquisition for systems analysis
Different power output ratio FC and GTGround power plant PFC > PGT
Propulsion system generator PFC ≤PGT
Potential multi fuelseg. H2 for Fuel cell and pre/post burner and
Bio-Jet fuel for primary gas turbine combustor Challenges- Stable operation in the fuel cell part- Realizing high specific power module
High pressure operation and dynamic response data
Summary on Hybrid/electric propulsion system studies
Hybrid/Turbo-electric propulsion system concepts are promising but key technology are at this moment fairly immature. Our focus is on motor and reactor parts in core engine.
SOFC/GT generator is applicable wide range of output power in aeronautics field.
1.FEATHER Project
2.Hybrid/electric Propulsion systemfor the aviation
3.Summary
Contents
3.Summary1. The presentation introduced the research
activities on the emission-free aircraft concepts in the long-term perspective (≈20yrs).
2. Propulsion system will be highly integrated in the airframe in design.
3. Hybrid/electric propulsion is promising regarding the ‘Emission-free aircraft’ goal. Introduction of innovative key technology and well-balanced hybridization in total design are important.