Distributed Electric Propulsion Research
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Transcript of Distributed Electric Propulsion Research
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NASADistributed Electric Propulsion
Research
E2 Fliegen
Stuttgart, Germany
Feb 27th, 2015
Mark Moore
Convergent Electric Propulsion Technology Demonstrator Principal Investigator
NASA Langley Research Center
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Many Electric Flight DemonstratorsHave Been Developed in Recent Years
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Rui Xiang RX1EChina
E-FanEADS
FEATHERJAXA
E-GeniusEADS
Electric Cri-CriEADS
DA-36 E-StarEADS
Breuget Range Equation for Electric Aircraft
NASA Focus: Show Electric Flight
Relates to Higher Speed(While Still Achieving
High Efficiency)
But All are Low Speed
Range is Independent
of Speed
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Electric Propulsion DifferencesCompared to Existing Propulsion Solutions
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Electric Propulsion PenaltiesEnergy 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 range6x the motor power to weight of piston engines
None air breathing - No power lapse with altitude or on hot daysExtremely Quiet
Zero vehicle emissions10x lower energy costs
Electric Propulsion Integration BenefitsScale independence of efficiency and power to weight
Power to weight and efficiency dont degrade at smaller sizesExtremely compact
High reliability few moving parts
The integration benefits suggest Distributed Electric Propulsion (DEP)approaches could achieve closely coupled, multi-disciplinary benefitsacross aerodynamics, propulsion, control, acoustics, and structures.
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NASA Rapid Spiral DevelopmentResearch of Distributed Electric Propulsion
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3m Span Small UAS
Scale
10m Span DEP Wing Only
Scale
11m Span Full General Aviation Aircraft
Scale
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NASA Langley 1st DEP Spiral Sub-Scale 12 Wind Tunnel Test
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12 NASA Langley Wind Tunnel Testing to Establish 1st DEP Controls Aerodynamic Database
Wind Tunnel Test Unpowered CLs
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NASA Langley 1st DEP Spiral Sub-Scale VTOL DEP Flight Demonstrator
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7General 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.
Lift/DragRatio
Wing CL
Current General Aviation AircraftAerodynamic Efficiency
Cirrus SR-22
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80
5
10
15
20
25
0 0.2 0.4 0.6 0.8 1 1.2
Increase Wing Loading to AchieveHigh Aerodynamic Efficiency at High Speed
StallSpeed(knots)
Wing loading (lb/ft2)
DEP Clmax = 5
Stall Speed vs Wing Loading(General Aviation Aircraft)
Lift/Drag Ratio vs Cruise CL(General Aviation Aircraft)
200 mphCruise
120 mphCruise
L/D
CLConventional GA aircraft
DEP GA aircraft
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5
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0 0.2 0.4 0.6 0.8 1 1.2
DEPAircraft
200 mphCruise
00
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9Highly Coupled Aero-Propulsive DEP WingTo Achieve High Wing Loading
(18) .5m diameter propellers
distributed across wing span
with 12 kW per propeller
(220 kW total power)
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01
2
3
4
5
6
-2 0 2 4 6 8 10
CL
()
Lift Coefficient at 61 Knots (with and without 220 kW)
No Flap (STAR-CCM+) 40 Flap, No Power (STAR-CCM+)
40 Flap with Power (STAR-CCM+) 40 Flap with Power (Effective, STAR-CCM+)
40 Flap with Power (FUN3D) 40 Flap with Power (Effective, FUN3D)
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STAR-CCM+ uses SST (Menter) k- turbulence model with -Retransition model
FUN3D runs use Spalart-Allmaras
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5
10
15
20
25
0 20 40 60 80
CL
max
Velocity (kts)
Unpowered
Constant Power (220 kW)
Lift Coefficient versus
Reference Speed
DEP Highlift Aero-PropulsiveAnalysis Results
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NASA Langley 2nd SpiralDesign/Analyze/Build/Test 10m DEP Wing
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NASA Langley 2nd SpiralDEP 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
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Low Speed Taxi Testing Results
Instrumentation system is 75% complete; Air Data probe, wing surface pressures and GPS are not yet integrated, so we cant 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.
40 mph, 6400 rpm =10 deg, Full Flaps, Upwind with 4 kt wind
~2300 lbf Lift
NASA Langley 2nd SpiralDEP Wing Initial Testing
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Data is matching CFD extremely well, with the vectored thrust
(effective lift) accounted.
40 mph, 6400 rpm =10 deg, 40 Deg Flaps
Reference Speed (knots)
Current Validation
NASA Langley 2nd SpiralDEP Wing Initial Testing
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Inner span propellers are fixed pitch and
fold conformal against the nacelle,
and are only active at low/slow flight.
Cruise Aero-Propulsive Effects
Wingtip Propulsors Increase Cruise Efficiency
Smaller diameter propeller
Higher Cruise Speed and/or
Lower tipspeed propeller
Lower Induced Drag
Aerodynamic Effects of Wingtip Mounted Propellers and Turbines,
Luis Miranda AIAA Paper 86-1802
Conventional GA Aircraft
DEP Aircraft
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Modifies existing General Aviation (GA) aircraft by removing the wingand 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
Tecnam P2006T Baseline Light Twin Retrofit LEAPTech NASA DEP Demonstrator
NASA Langley 3rd SpiralDEP General Aviation X-Plane
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DEP Community Noise Benefit
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
Broadband noise
Conceptual Effects of Frequency Spreading
Cirrus SR-22
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3rd Spiral DEP Flight DemonstratorSystem Level Impacts
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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.
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Cirrus SR-22General Aviation Aircraft
3400 lb
200 Whr/kg batterieswith a 200 mile range
with reserves
400 Whr/kg battery energy density is critical to enable early adopter electric propulsion markets
Battery Specific Energy Sensitivity
Cirrus SR-22 with Retrofit Electric Propulsion
11,300 lb
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Early Market Electric Propulsion MarketThin-Haul Commuter Mission
Example of dominant (green) and long-tail (yellow) market distribution (with each being 50% of the total market share)
0
2000
4000
6000
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10000
12000
14000
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All Cape Air Operations 11.7M Seat Miles
~100 Cessna 402 9 passengerAircraft
Cape Air Commuter Trip Range Distribution
Trip Range (nm)
Numberof
Trips
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)
No Trips
with Range
> 220 nm
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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
Why Use Spiral Development?
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Questions?
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NASA
Convergent Aeronautic Solutions (CAS)
Distributed Electric Propulsion (DEP)
Tecnam P2006T Based X-PlaneEffect of Propeller Radius to Chord Ratio
Spanwise Lift Distribution with Propellers
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Lift Drag Thrust CL Effective CL CD
0 3,377 lb 524 lb 853 lb 4.86 4.86 0.778
2 3,471 lb 565 lb 853 lb 4.99 5.04 0.838
4 3,535 lb 603 lb 853 lb 5.09 5.17 0.895
5 3,589 lb 626 lb 853 lb 5.16 5.27 0.929
6 3,617 lb 641 lb 853 lb 5.20 5.33 0.952
8 3,645 lb 670 lb 853 lb 5.24 5.42 0.995
9 3,648 lb 676 lb 853 lb 5.25 5.44 1.003
10 3,662 lb 698 lb 853 lb 5.27 5.48 1.037
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DEP Operating Cost BenefitWhile Achieving Zero In-Flight Emissions
Electricity based aircraft energy provide a decrease in price variability and cost riskas well as a true renewable energy path
(100LL fuel is ~2x higher cost than auto gas)
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100
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200
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Energy
Insurance/Taxes
Personnel
Pilot
Acquisition
Facilities
Maintenance
General AviationTotal Operating Cost Comparison
SOA Baseline DEP Concept
$/Hr
0
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Energy
Insurance
Flight Crew
Financing
Maintenance
Single Aisle CommercialDirect Operating Cost Comparison
SOA Baseline DEP Concept
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System Impact of Applying Distributed Electric Propulsion
January 1315, 2015 NASA Aeronautics Research Mission Directorate 2015 LEARN/Seedling Technical Seminar 25
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 17Propulsive Efficiency: Energy conversion efficiency from 24% to 83%Emissions: Life cycle GHG decreased by 5x using U.S. average electricityCommunity Noise: Certification noise level from 85 to 2.5xOperating Costs: Energy costs decrease from 45% to 12% of TOC
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General Aviation: Cirrus SR-22
Gross Weight ~ 3400 lb
L/D cruise ~ 11
Wing loading = 25 lb/ft2
Commuters: Cessna Grand Caravan
Gross Weight ~ 6200 lb
L/D cruise ~ 10
Wing loading 22 lb/ft2
Regional Jets: Bombardier Q300
Gross Weight ~ 43,000 lb
L/D cruise ~ 16
Wing loading 71 lb/ft2
Single Aisle: Boeing 737
Gross Weight ~150,000 lb
L/D cruise ~ 18
Wing loading 111 lb/ft2
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.
DEP Integration Application Across Aviation Markets
Electric propulsion integration benefitsdecrease with larger aircraft due to the far superior baseline metrics, but still offercompelling benefits across efficiency, emissions, noise, and operating costs.