Quantification of the Aerodynamic Benefit of...

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


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


The D8 Aircraft Concept

MIT N+3 D8.2


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


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


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


PK =

∫∫exit

(pt − pt∞) V · n dS

−∫∫

inlet

(pt − pt∞) V · n dS

inlet exit

Non-BLI (Podded) Configuration


Photo NASA/George Homich

0 50 in10

BLI (Integrated) Configuration


Photo NASA/George Homich

0 50 in10

BLI (Integrated) Configuration


Photos NASA/George Homich

Back-to-Back Comparison


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


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)


Outline

1 Introduction






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


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%)


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


BLI Benefit and Propulsive Efficiency

Benefit primarily due to higher propulsive efficiency

Additional 1% gain from reduced body dissipation


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


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






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)


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 %


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%


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


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


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






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%


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


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:


Alejandra Uranga, Ph.D.Assistant Professor and Provost FellowAerospace & Mechanical EngineeringUniversity of Southern California

Email: [email protected]: (213) 821-0846

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