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Quantification of the Aerodynamic Benefitof Boundary Layer Ingestion
A University-Industry-NASA Collaboration
Technology Lead: Alejandra Uranga [email protected]
Chief Engineer: Mark Drela [email protected]
Principal Investigator: Edward Greitzer [email protected]
Green Aviation Technical Interchange MeetingNASA Langley Research Center
March 29 – 31, 2016
Message
I Closer integration of propulsion system and airframe provides newopportunities to increase fuel efficiency of commercial aircraft
I Boundary layer ingestion (BLI)
I Novel configurations
I System optimization (airframe, engine, operations)
I Flow power and dissipation provide useful metrics for integratedconfigurations
I Aerodynamic merit of BLI demonstrated in back-to-back comparisonof BLI vs non-BLI: 8–10% power reduction at cruise
2016 Green Aviation TIM 1 / 30
Outline
1 Introduction
2 Boundary Layer Ingestion (BLI)
3 Aerodynamic BLI Benefit
4 System-Level Benefits
5 Summary and Conclusions
2016 Green Aviation TIM 2 / 30
MIT N+3 Project
Aircraft and Technology Concepts for an N+3 Subsonic Transport
I Phase 1 (2008 – 2010): development of double-bubble D8 aircraft
I Phase 2 (2010 – 2015): benefit of airframe-engine integration
30+ people including 2 faculty, 3 staff, 9 grads, 13 undergrads
I Phase 3 (2015 – present): performance vs. speed, transonic OML
2016 Green Aviation TIM 3 / 30
The D8 Aircraft Concept
MIT N+3 D8.2
2016 Green Aviation TIM 4 / 30
I B737-800/A320 class
I 180 PAX, 3,000 nm range
I Double-bubble lifting fuselagewith pi-tail
I Two aft, flush-mounted enginesingest ∼ 40% of fuselage BL
I Cruise Mach 0.72
−36% fuel with current tech
−65% fuel with advanced tech(2025-2035)
No “magic bullet”E. Greitzer et al. 2010, NASA CR 2010-216794A. Uranga et al. 2014, AIAA 2014-0906
Boundary Layer Ingestion (BLI)
wake, or “draft”
WastedKinetic Energy
Zero NetMomentum
combined wake and jet
propulsor jet
+
+
++
+
+
+-
--
I BLI reduces wasted KE in combined jet+wake (mixing losses)
I Ambiguous decomposition into drag and thrust(airframe) (propulsion)
⇒ consider power balance instead of force accounting
2016 Green Aviation TIM 5 / 30
M. Drela 2009, AIAA Journal 47(7)
BLI Benefit
BLI benefit (aerodynamic)
Savings in power required for given net stream-wise forcewith BLI engines relative to non-BLI engines
Power metric
Mechanical flow power transmitted to the flow by the propulsors
PK ≡ ©∫∫
(pt − pt∞) V · n dS = m∆ptρ
I Independent of propulsor characteristics
I Surrogate for fuel burn: mfuel =PK
hfuel ηth ηf
2016 Green Aviation TIM 6 / 30
Obtaining PK
Direct Measurement: Integrating propulsor inlet and outlet flows
Indirect Measurement: Use electrical power to motor, PE
PK = ηf︸︷︷︸fan
efficiency
× ηm︸︷︷︸motor
efficiency
× PE
︸ ︷︷ ︸shaft power
Numerical Simulations: Use CFD to predict flow on full airframe with enginemodel, from which force and power can be extracted by integration
2016 Green Aviation TIM 7 / 30
PK =
∫∫exit
(pt − pt∞) V · n dS
−∫∫
inlet
(pt − pt∞) V · n dS
inlet exit
Non-BLI (Podded) Configuration
2016 Green Aviation TIM 8 / 30
Photo NASA/George Homich
0 50 in10
BLI (Integrated) Configuration
2016 Green Aviation TIM 9 / 30
Photo NASA/George Homich
0 50 in10
BLI (Integrated) Configuration
2016 Green Aviation TIM 10 / 30
Photos NASA/George Homich
Back-to-Back Comparison
2016 Green Aviation TIM 11 / 30
Non-BLI(Podded)
BLI(Integrated)
BLI Benefit: Power Ratio ≡ power required with BLI
power required without BLI=
PK
P ′K
Propulsive Efficiency:
ηp ≡ net propulsive power to vehicle
power added to flow≡ PK − Φjet
PK
Experiments
NASA LaRC 14×22 tunnel (2 entries)
I 1:11 powered model, 13.4 ft (4 m) spanV∞ = 70 mph, Rec = 570k, M∞ = 0.09
84 mph 680k 0.11
I Non-BLI and BLI configurations
MIT 1×1 tunnel
I Turbomachinery characterization
2016 Green Aviation TIM 12 / 30
Experiments
Non-BLI and BLI configurations share a large part of hardware
I Common wings
I Common front 80% of fuselage
I Common propulsor units plug into interchangeable tails(fan stage, motor, center-body, housing, nozzle, electronics)
2016 Green Aviation TIM 13 / 30
Outline
1 Introduction
2 Boundary Layer Ingestion (BLI)
3 Aerodynamic BLI Benefit
4 System-Level Benefits
5 Summary and Conclusions
2016 Green Aviation TIM 14 / 30
BLI Benefit: Less Power to Produce Given Force
0 0.02 0.04 0.06 0.08 0.1-0.04
-0.03
-0.02
-0.01
0
0.01
0.02
0.03
0.04
CPK
CX
BLI
non-BLI
unpowered
net drag
net thrust
cruise
70 mph Indirect84 mph Indirect70 mph Direct
Data taken at 70mph and 84mph during both 2013 and 2014 NASA Langley entries;
12–17 repeat runs at each condition
2016 Green Aviation TIM 15 / 30
BLI Benefit
0 0.02 0.04 0.06 0.08 0.1-0.04
-0.03
-0.02
-0.01
0
0.01
0.02
0.03
0.04
CPK
CX
BLI
non-BLI
unpowered 70 mph Indirect
84 mph Indirect70 mph Direct
0.04 0.045 0.05 0.055-4
-3
-2
-1
0
1
2
3
4×10−3
BLI
non-BLI
net drag
net thrust
cruise
70 mph Indirect
84 mph Indirect70 mph Direct
8.6% BLI Benefit
(CI = ± 0.3%)
2016 Green Aviation TIM 16 / 30
Bases for Comparison
Given a non-BLI propulsor with some jet velocity, mass flow, nozzle area,how do you choose an “equivalent” BLI propulsor for comparison?
smaller propulsor
Anozzle
Anozzle ref
lowerpropulsorpower
1.20.80.60.4 1
1.02
0.98
0.96
0.94
0.92
0.90
1
BLI propulsorswith same net force
non-BLI propulsor
PK
PKrefequal Vjet
equal Anozzle
equal PK
equal m
2016 Green Aviation TIM 17 / 30
BLI Benefit and Propulsive Efficiency
Benefit primarily due to higher propulsive efficiency
Additional 1% gain from reduced body dissipation
2016 Green Aviation TIM 18 / 30
0.74 0.76 0.78 0.8 0.82 0.84 0.860.85
0.9
0.95
1
1.05
ηp
PKPKref
reduceddissipation
(Φwake + Φsurf)
increasedpropulsive efficiency
BLI benefitat equalAnozzle
non-BLI 70 mphnon-BLI 84 mphBLI 70 mphBLI 84 mph
BLI Benefit: Not Unique
Vary propulsive efficiency by changing nozzle area
2016 Green Aviation TIM 19 / 30
BLI Plug C
Plug B
Plug A
non-BLIPlug B
0.74 0.76 0.78 0.8 0.82 0.84 0.860.85
0.9
0.95
1
1.05
ηp
PKPKref
non-BLI 70 mphnon-BLI 84 mphBLI 70 mphBLI 84 mph
8.6%benefitat equalAnozzle
10.3%benefitat equal
m
Outline
1 Introduction
2 Boundary Layer Ingestion (BLI)
3 Aerodynamic BLI Benefit
4 System-Level Benefits
5 Summary and Conclusions
2016 Green Aviation TIM 20 / 30
System Impact of BLI
BLI benefitsI Aerodynamic (direct) benefits
I Reduced jet and wake dissipationI Reduced nacelle wetted area
I System-level (secondary) benefitsI Reduced engine weightI Reduced nacelle weightI Reduced vertical tail sizeI Compounding from reduced overall weight
“Morphing” sequence: B737-800 7→ D8
I Features of D8 introduced one at a time
I Sequence of conceptual aircraft designs, optimized at each step(TASOPT)
2016 Green Aviation TIM 21 / 30
E. Greitzer et al. 2010, NASA CR 2010-216794M. Drela 2011, AIAA 2011-3970A. Uranga et al. 2014, AIAA 2014-0906
Morphing Sequence: B737-800 7→ D8.2 7→ D8.6
0
0.2
0.4
0.6
0.8
187 %
81 % 82 %
67 % 66 %
100 %
optim
ized
737-
800
M=
0.8,
CFM
56en
gine
0
slow
toM
=0.
72
1
D8
fuse
lage
,pit
ail
2
rear
podd
eden
gine
s
3
inte
grat
eden
gine
s,B
LI
4
optim
ize
engi
neB
PR
,FP
R
5
2010
engi
nes
8
FuelBurn
64 %
D8.2
6 7 9 10
2035
engi
nes
2035
mat
eria
ls
win
gbo
t.N
LF
smar
tstr
uct
49 %
38 % 36 % 35 %
D8.6- 15 %
2016 Green Aviation TIM 22 / 30
Sensitivities to Conceptual Models (Preliminary Phase 3)I Assessing uncertainty on TASOPT’s conceptual predictions
I Mission: 180 PAX, 3 000 nm, Mach 0.80 cruise
I Compare overall (system-level) benefit of the D8 relative to aconventional tube-and-wing aircraft with same technology, speed, etc.
I Introduce changes in engine models, and re-assess D8’s benefit
0 20% 40% 60% 80% 100%
All Changes
+200K Turbine Metal
Geared Weight Model
+5% Fan Efficiency
-20% Nacelle Drag
-10% Engine Weight
Baseline 2010 Eng Tech 25.5% D8 benefit ± 2%
25.6%
24.8%
25.5%
26.5%
24.5%
23.9%
2016 Green Aviation TIM 23 / 30
Relative Benefit of D8 (Preliminary, Phase 3)Benefit of the D8 relative to conventional tube-and-wing configurationis insensitive to changes in engine models
0 1 2 3 4 5 6 7
M∞ = 0.802035 Eng Tech
M∞ = 0.802010 Eng Tech
M∞ = 0.722010 Eng Tech 21–23% benefit
23–25% benefit
21–23% benefit
Tube-and-wing D8
PFEI (kJ/kg·km)
Penalty: - 2% ηf+ 10% eng weight
Payload Fuel Energy Intensity
2016 Green Aviation TIM 24 / 30
Effect of Cruise Speed (Preliminary, Phase 3)
0 1 2 3 4 5 6 7
D8
Tube-and-Wing
PFEI (kJ/kg·km)
+ 9%
+ 6%
M∞ = 0.72 M∞ = 0.80
23% benefitat M∞ = 0.72
25% benefitat M∞ = 0.8
I Cost of flying faster is significantI Cost for D8 is smaller than for tube-and-wing
I Larger nacelles in tube-and-wing aircraft cause higher penalties(weight, drag) from larger engines
2016 Green Aviation TIM 25 / 30
High-Efficiency, High-OPR, Small Cores
Pratt & Whitney – Lord et al., AIAA 2015-0071
SAE INTERNATIONAL
“Engine Architecture for High Efficiency at Small Core Size” Lord et al., AIAA 2015-0071 - Pratt & Whitney
42 2016 Green Aviation TIM 26 / 30
Outline
1 Introduction
2 Boundary Layer Ingestion (BLI)
3 Aerodynamic BLI Benefit
4 System-Level Benefits
5 Summary and Conclusions
2016 Green Aviation TIM 27 / 30
Summary
I BLI has potential for large fuel reduction for transport aircraft
I Carried out first back-to-back comparison of BLI vs non-BLI
I Demonstrated aerodynamic merit of BLI for realistic configuration
8.6% at equal nozzle area ±1.8% at 95% confidence
10.3% at equal mass flow
I Proof-of-concept of BLI for fuel reduction of commercial transports
I System-level benefit of BLI estimated to be above 20%
2016 Green Aviation TIM 28 / 30
A View of the Future?
I There have been 50+ years of developing non-BLI systemswe now need to learn to use BLI
I Opened up new possibilities for advanced transport aircraft
I Identified new class of important research problemsI Aircraft configuration and airframesI Propulsion system and integrationI Component technologies
2016 Green Aviation TIM 29 / 30
Acknowledgments
I Funding from NASA under Cooperative AgreementsNNX08AW63A, NNX11AB35A, NNX15AM91A
I Team members at MIT, Aurora, Pratt & Whitney, NASA
I NASA Project management
I Staff at NASA Langley 14×22 Foot Subsonic Wind Tunnel
I N. Cumpsty, Y. Dong, A. Epstein, E. Gallagher, A. Murphy,J. Sabnis, G. Tillman, H. Youngren
Contact Information:
2016 Green Aviation TIM 30 / 30
Alejandra Uranga, Ph.D.Assistant Professor and Provost FellowAerospace & Mechanical EngineeringUniversity of Southern California
Email: [email protected]: (213) 821-0846