activities on mea and electric-powered propulsion technologies in

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

4

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


5


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

6

indicatorsmeasurement system

display

Li-ion battery

warning & caution

fourfold electric motor(4 elements of motor connected in series)

reductiongear(1:3.16)


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)

7


fourfold motor

8

Time

Thrust

Avoidance of complete thrust loss

Safety altitude

failure

× ✓

Time

✓✓

✓✓✓✓

Altitude

15

Characteristic features of the electric propulsion system(1/2)


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

9

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

10

1.FEATHER Project


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)


Cruise Fuel/EnergyConsumption(rel. to 2005 best in class)


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

14

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(

15

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 aircraft０１

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


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.

activities on mea and electric-powered propulsion technologies in

Documents