NASA Distributed Electric Propulsion Research

NASA
Distributed Electric Propulsion
Research
E2 Fliegen
Stuttgart, Germany
Feb 27th, 2015
Mark Moore
Convergent Electric Propulsion Technology Demonstrator Principal Investigator
NASA Langley Research Center
mark.d.moore@nasa.gov
Many Electric Flight Demonstrators
Have Been Developed in Recent Years
But All are Low Speed
Rui Xiang RX1E
China
Breuget Range Equation
for Electric Aircraft
E-Fan
EADS
Range is Independent
of Speed
FEATHER
JAXA
DA-36 E-Star
EADS
NASA Focus:
Show Electric Flight
Relates to Higher Speed
(While Still Achieving
High Efficiency)
Electric Cri-Cri
EADS
E-Genius
EADS
2
Electric Propulsion Differences
Compared to Existing Propulsion Solutions
Electric Propulsion Penalties
Energy Storage Weight (50x worse than aviation fuel)
Energy Storage Cost (Tesla 65 kWhr battery is ~$25,000)
Certification Uncertainties and Absence of Standards
Electric Propulsion Benefits
~2x efficiency of turbine engines, 3-4x efficiency of piston engines
High efficiency across >50% rpm range
6x the motor power to weight of piston engines
None air breathing - No power lapse with altitude or on hot days
Extremely Quiet
Zero vehicle emissions
10x lower energy costs
Electric Propulsion Integration Benefits
Scale independence of efficiency and power to weight
Power to weight and efficiency don’t degrade at smaller sizes
Extremely compact
High reliability – few moving parts
The integration benefits suggest Distributed Electric Propulsion (DEP)
approaches could achieve closely coupled, multi-disciplinary benefits
across aerodynamics, propulsion, control, acoustics, and structures.
3
NASA Rapid Spiral Development
Research of Distributed Electric Propulsion
3m Span Small UAS
Scale
10m Span DEP Wing Only
Scale
11m Span Full General Aviation Aircraft
Scale
4
NASA Langley 1st DEP Spiral
Sub-Scale 12’ Wind Tunnel Test
12’ NASA Langley Wind Tunnel Testing to Establish 1st DEP Controls Aerodynamic Database
Wind Tunnel Test Unpowered CL’s
5
NASA Langley 1st DEP Spiral
Sub-Scale VTOL DEP Flight Demonstrator
6
Current General Aviation Aircraft
Aerodynamic Efficiency
Lift/Drag
Ratio
Cirrus SR-22
Wing CL
General Aviation aircraft are only aerodynamically efficient at low speeds because
the wing is oversized for 61 knot stall, 2000 ft field lengths.
Aerodynamic efficiency is very important for energy constrained electric aircraft.
7
Increase Wing Loading to Achieve
High Aerodynamic Efficiency at High Speed
Stall Speed vs Wing Loading
(General Aviation Aircraft)
Lift/Drag Ratio vs Cruise CL
(General Aviation Aircraft)
25
20
DEP
Clmax = 5
Stall
Speed
(knots)
DEP
Aircraft
200 mph
120 mph Cruise
Cruise
15
L/D
10
5
0
0
200 mph
Cruise
0
0
Wing loading
(lb/ft2)
0.2
Conventional GA aircraft
0.4
0.6
0.8
1
1.2
CL
DEP GA aircraft
8
Highly Coupled Aero-Propulsive DEP Wing
To Achieve High Wing Loading
(18) .5m diameter propellers
distributed across wing span
with 12 kW per propeller
(220 kW total power)
9
DEP Highlift Aero-Propulsive
Analysis Results
Lift Coefficient at 61 Knots (with and without 220 kW)
No Flap (STAR-CCM+)
40º Flap, No Power (STAR-CCM+)
40º Flap with Power (STAR-CCM+)
40º Flap with Power (Effective, STAR-CCM+)
40º Flap with Power (FUN3D)
40º Flap with Power (Effective, FUN3D)
6
•
5
•
3
Lift Coefficient
versus
Reference Speed
2
25
20
CLmax
CL
4
STAR-CCM+ uses SST
(Menter) k-ω turbulence
model with γ-Reθ
transition model
FUN3D runs use SpalartAllmaras
1
Constant Power
(220 kW)
15
10
5
Unpowered
0
0
0
-2
0
2
4
α (º)
6
8
10
20
40
60
80
Velocity (kts)
10
NASA Langley 2nd Spiral
Design/Analyze/Build/Test 10m DEP Wing
11
NASA Langley 2nd Spiral
DEP Wing Initial Testing
Low Speed Testing (40 mph) at Oceano Airport
Testing is Starting at NASA Armstrong Dry Lakebed
with Speeds of 70 mph
Air Bag System Dampens
Ground Vibration
12
NASA Langley 2nd Spiral
DEP Wing Initial Testing
Low Speed Taxi Testing Results
40 mph, 6400 rpm α=10 deg, Full Flaps,
Upwind with 4 kt wind
Instrumentation system is 75%
complete; Air Data probe, wing
surface pressures and GPS are
not yet integrated, so we can’t
account for winds on the airfield
will increase/decrease effective
airspeed (and measured lift)
With time averaging, the
vibration levels from the ground
are well managed.
~2300 lbf Lift
13
NASA Langley 2nd Spiral
DEP Wing Initial Testing
40 mph, 6400 rpm α=10 deg, 40 Deg Flaps
Current Validation
Data is matching CFD extremely
well, with the vectored thrust
(effective lift) accounted.
Reference Speed (knots)
14
Cruise Aero-Propulsive Effects
Wingtip Propulsors Increase Cruise Efficiency
Lower Induced Drag
Smaller
diameter
propeller
Higher Cruise
Speed and/or
Lower tipspeed
propeller
DEP Aircraft
Conventional GA Aircraft
Aerodynamic Effects of Wingtip Mounted
Propellers and Turbines,
Luis Miranda AIAA Paper 86-1802
Inner span propellers are fixed pitch and
fold conformal against the nacelle,
and are only active at low/slow flight.
15
NASA Langley 3rd Spiral
DEP General Aviation X-Plane
Tecnam P2006T Baseline Light Twin
Retrofit LEAPTech NASA DEP Demonstrator
• Modifies existing General Aviation (GA) aircraft by removing the wing
and engines, and replacing with a DEP wing system.
• Research provides rapid concept to flight of DEP technologies.
•
•
•
•
•
Complex high voltage electric power architectures and EMI mitigation
Multi-disciplinary high aspect ratio wing aeroelastics
Robust, reliable, Redundant distributed control
PAI design tools and validation, wingtip vortex propulsion
Spread frequency acoustics
16
DEP Community Noise Benefit
Conceptual Effects of Frequency Spreading
Broadband noise
Cirrus SR-22
Conventional Single 3-Bladed Propeller Harmonics
(18) Asynchronous 5-bladed propellers that spread a
single blade passage harmonic across
30 harmonics instead of 1 that blends into the
broadband as ‘white noise’
17
3rd Spiral DEP Flight Demonstrator
System Level Impacts
Primary Objective
• Goal: 5x Lower Energy Use (Comparative to Retrofit GA Baseline @ High
Speed Cruise)
• Minimum Threshold: 3.5x Lower Energy Use
Derivative Objectives
• 30% Lower Total Operating Cost (Comparative to Retrofit GA Baseline)
• Zero In-flight Carbon Emissions
Secondary Objectives
•
•
•
•
15 dB Lower community noise (with even lower true community annoyance) .
Flight control redundancy, robustness, reliability, with improved ride quality.
Certification basis for DEP technologies.
Analytical scaling study to provide a basis for follow-on ARMD Hybrid-Electric
Propulsion (HEP) commuter and regional turbo-prop research investments.
Primary Objective Basis
• Electric only conversion of the baseline aircraft results in a 2.9 - 3.3x efficiency
increase (i.e. 28% to 92% motor efficiency).
• Integrating DEP results in an additional 1.2 - 1.5x efficiency increase.
• Minimum threshold is 2.9 x 1.2 = 3.5, with goal of 3.3 x 1.5 = 5.0 goal.
18
Battery Specific Energy Sensitivity
200 Whr/kg batteries
with a 200 mile range
with reserves
Cirrus SR-22
with Retrofit Electric Propulsion
11,300 lb
400 Whr/kg battery energy density is critical to
enable early adopter electric propulsion markets
Cirrus SR-22
General Aviation Aircraft
3400 lb
19
Early Market Electric Propulsion Market
Thin-Haul Commuter Mission
Thin-Haul Commuters provide Essential Air Services to small communities with ‘thin’
passenger trip distributions. New business models and technologies are developing across
many industries to capture ‘long-tail’ markets instead of focusing only on dominant markets.
(see The Long-Tail:
Why the Future of Business is Selling Less of More)
Example of dominant (green) and long-tail (yellow) market distribution
(with each being 50% of the total market share)
14000
Cape Air Commuter Trip Range Distribution
12000
10000
8000
Number
of 6000
Trips
No Trips
with Range
> 220 nm
All Cape Air Operations
11.7M Seat Miles
~100 Cessna 402 9 passenger
Aircraft
4000
2000
20
23
27
34
39
40
48
59
66
79
82
90
97
104
110
129
135
139
159
163
168
169
172
183
210
0
Trip Range (nm)
8
Why Use Spiral Development?
EADS has recently funded 4 electric propulsion integration flight demonstrators
• To quickly become familiar with this new propulsion technology area through
hardware demonstrations that offer a solid engineering experience.
• To quickly explore alternate integration approaches.
• Companies have yet to flight demonstrated distributed electric architectures.
For each research effort spiral development was utilized to provide…
• Experimentation that provides TRL advancement across vehicle sizes due to the
scale-free nature of electric technologies
• Approach agility due to rapidly accelerating technologies
• Provide early lessons learned with minimal consequence
• Greater control of discrete costs and risks
• Establish an early certification basis
• “Fail early, Often”
21
Questions?
NASA
Convergent Aeronautic Solutions (CAS)
Distributed Electric Propulsion (DEP)
Tecnam P2006T Based X-Plane
Effect of Propeller Radius to Chord Ratio
Spanwise Lift Distribution with Propellers
22
α
Lift
Drag
Thrust
CL
Effective CL
CD
0º
3,377 lb
524 lb
853 lb
4.86
4.86
0.778
2º
3,471 lb
565 lb
853 lb
4.99
5.04
0.838
4º
3,535 lb
603 lb
853 lb
5.09
5.17
0.895
5º
3,589 lb
626 lb
853 lb
5.16
5.27
0.929
6º
3,617 lb
641 lb
853 lb
5.20
5.33
0.952
8º
3,645 lb
670 lb
853 lb
5.24
5.42
0.995
9º
3,648 lb
676 lb
853 lb
5.25
5.44
1.003
10º
3,662 lb
698 lb
853 lb
5.27
5.48
1.037
DEP Operating Cost Benefit
While Achieving Zero In-Flight Emissions
$/Hr
500
General Aviation
Total Operating Cost Comparison
450
400
Energy
350
Insurance/Taxes
300
Personnel
250
Pilot
200
Acquisition
150
Facilities
100
Maintenance
50
0
SOA Baseline
6000
5000
DEP Concept
Single Aisle Commercial
Direct Operating Cost Comparison
Energy
4000
Insurance
3000
Electricity based aircraft energy provide a
decrease in price variability and cost risk
as well as a true renewable energy path
(100LL fuel is ~2x higher cost than auto gas)
Flight Crew
Financing
2000
Maintenance
1000
0
SOA Baseline
DEP Concept
24
System Impact of Applying
Distributed Electric Propulsion
Make Aircraft More Efficient, with Improved Emissions, Noise, Ride Quality, Safety, and Operating Costs
• Typically achieving an improvement in one aircraft capability requires taking penalties in other areas.
• By leveraging this new integration technology, Distributed Electric Propulsion (DEP), dramatic
improvements are possible across these areas, while only absorbing penalties in range and weight
(which penalties will become significantly reduced as battery specific energy improves).
• Applying DEP to a General Aviation aircraft enables these improvements, while limiting the range to
200 miles and increasing the vehicle weight from 2700 lb to 3400 lb.
Aerodynamic Efficiency: Lift/Drag ratio improved from 11 to 17
Propulsive Efficiency: Energy conversion efficiency from 24% to 83%
Emissions: Life cycle GHG decreased by 5x using U.S. average electricity
Community Noise: Certification noise level from 85 to <65 dB
Safety: Highly redundant propulsion system
Ride Quality: Wing loading increased by >2.5x
Operating Costs: Energy costs decrease from 45% to 12% of TOC
January 13–15, 2015
NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar
25
DEP Integration
Application Across Aviation Markets
General Aviation SOA provides large benefit advantages
for early market success with emerging electric
propulsion technology adoption to provide
more rapid tech acceleration
for larger scale aircraft.
Single Aisle: Boeing 737
Gross Weight ~150,000 lb
L/D cruise ~ 18
Wing loading 111 lb/ft2
Regional Jets: Bombardier Q300
Gross Weight ~ 43,000 lb
L/D cruise ~ 16
Wing loading 71 lb/ft2
Commuters: Cessna Grand Caravan
Gross Weight ~ 6200 lb
L/D cruise ~ 10
Wing loading 22 lb/ft2
Electric propulsion integration benefits
General Aviation: Cirrus SR-22
Gross Weight ~ 3400 lb
L/D cruise ~ 11
Wing loading = 25 lb/ft2
decrease with larger aircraft due to the far
superior baseline metrics, but still offer
compelling benefits across efficiency,
emissions, noise, and operating costs. 26