National Aeronautics and Space Administration

Optimization of Hybrid Wingbody Aircraft

Meng-Sing LiouNASA Glenn Research Center

Spring Progress in Mathematican and Computational Studies on Science and Engineering ProblemsMay 3-5, 2014, National Taiwan University

A Tribute

A cumulative effort, by postdocs and students under various NASA programs, developing and piecing together a set of necessary elements for performing MDAO.

• Akira Oyama• Hyoungjin Kim• Byung Joon Lee• Justin Lamb• Angelo Scandaliato• Nick Stowe• Weigang Yao• Mattia Padulo• May-Fun Liou

• SFW, SUP• NASA Postdocs

Program• NASA USRP

KnowledgeCapabilitiesApplications

NASA’s Technology Development Goals

Current Commercial Aircraft

• Pros: lighter weight, higher lift to drag ratio, and lower fuel burn, reduced community noise

• Cons: aerodynamic interferences may reduce aerodynamic performance, propulsive efficiency and structural tolerance to distortion

• A complex system requires simultaneous consideration of of multiple disciplines and design objectives

Hybrid Wingbody vs Current Aircraft

N2-B

Tube and wing Hybrid (blended) wingbody

Historical Development of HWB Vehicles

Northrop YB-35, 1946

Airfoil: NACA 65-019 root, NACA 65-018 tip

Northrop YB-49, 1947 Northrop Gruman B-2, 1989

Historical Development of HWB Vehicles

Boeing UCAV X-45C, 2002

Boeing UAV X-48, 2007

Burnelli CBY-3, 1955 Dassault nEUROn, 2012

Commercial Transport ???

Hybrid Wingbody Aircraft – N3-X

• HWB (hybrid wing body) configuration for N+3 requirements • Turboelectric Distributed Propulsion

– Embedded fans driven by electric motors in a mail-slot nacelle– Wingtip mounted superconducting turbo-generators– Decoupling of generator and motor speeds – Ingestion of upper surface boundary layer

• Expected to reduce fuel burn by more than 70% relative to Boeing 777-200LR

Kim, H. and Liou, M.-S., AIAA-2013-0221.

Fuel Efficiency and Noise DataFuel Efficiency Comparison

0

1000

2000

3000

4000

5000

6000

7000

0 100 200 300 400

Payload (1000 lbs)

Fuel

Eff

icie

ncy=

nmi x

pa

yloa

d/ra

nge

CurrentBest CurrentN2AN2BN2A-EXTE

Nm

ix P

aylo

ad /

Fuel

Bur

ned

B767-300ER

A330-300

B777-200ERA330-500FX

B767-300F

A330-200F2

A330-200F2

B747-8B777F

B747-400F

B747-400ERF

+1.6-6.1-11.1-17.2EPNdB Margin without elevon noise

+6.1+0.6-3.5-8.3EPNdB Margin with elevon noise

250.4250.4250.4250.7N+2 Goal

252.0244.3239.3233.5Cumulative EPNdB without elevon noise

256.5251.0246.9242.4Cumulative EPNdB with elevon noise

FPR=1.7FPR=1.6FPR=1.5FPR=1.4

+1.6-6.1-11.1-17.2EPNdB Margin without elevon noise

+6.1+0.6-3.5-8.3EPNdB Margin with elevon noise

250.4250.4250.4250.7N+2 Goal

252.0244.3239.3233.5Cumulative EPNdB without elevon noise

256.5251.0246.9242.4Cumulative EPNdB with elevon noise

FPR=1.7FPR=1.6FPR=1.5FPR=1.4

Table 21 N2A-EXTE FAR-36 noise assessment.

+1.6-6.1-11.1-17.2EPNdB Margin without elevon noise

+6.1+0.6-3.5-8.3EPNdB Margin with elevon noise

250.4250.4250.4250.7N+2 Goal

252.0244.3239.3233.5Cumulative EPNdB without elevon noise

256.5251.0246.9242.4Cumulative EPNdB with elevon noise

FPR=1.7FPR=1.6FPR=1.5FPR=1.4

+1.6-6.1-11.1-17.2EPNdB Margin without elevon noise

+6.1+0.6-3.5-8.3EPNdB Margin with elevon noise

250.4250.4250.4250.7N+2 Goal

252.0244.3239.3233.5Cumulative EPNdB without elevon noise

256.5251.0246.9242.4Cumulative EPNdB with elevon noise

FPR=1.7FPR=1.6FPR=1.5FPR=1.4

Table 21 N2A-EXTE FAR-36 noise assessment.

Noise Relative to FAR 36 Stage 3

26%

Expected improvement by 26%

But …

Challenges

• Integration of propulsion and airframe– Inlet ingesting thick boundary layer, resulting in a

considerably distorted flow with total pressure loss at the compressor face

– Significant loss in aerodynamic performance resulting from their mutual interferences

N2-A

N2-B

N3-X

HWB Configurations Studied by NASA Boeing UAV X-48, 2007

Outline of Presentation

• Integrated Configuration• Mitigation of inlet flow distortion and loss of

propulsive efficiency• Aerodynamic analysis and optimization for N2-B and

N3-X

Hybrid Wing Body Aircraft: N2B

N2-B

Impact on Propulsion System: Thick low-momentum layer ingested into inlet, Significant distortion and Total pressure loss at AIP

Boundary-Layer Ingestion

Pt/Pt_inf

0.9920.9680.9440.920.8960.8720.8480.8240.8

Horseshoe vortex,Lip flow separation

Non-uniform flow at AIP

S-bend separation,Secondary flow

Advantages: Reduced ram dragReduced structural weightReduced wetted areaReduced noiseIncreased propulsive efficiency

Flow Features in Embedded Boundary Layer Ingestion (BLI) Inlet

Hybrid wing-body

Forces:Viscous stressesStreamwise adverse pressure gradientCentrifugal force

BLI InletAllen et al.Vortex generator

Wall bleeding

Taming Distortion and Losses in BLI Inlets

• Alternative way to conventional flow control, without incurring system losses.

• Shape optimization: properly conditioning the flow before it entering the inlet.

Yu the Great – Xia Dynasty

Design Optimization: Problem Statement

• Design Condition• M0=0.85, Re0=3.8mil., A0/Ac=0.533• BL thickness : 35% of Inlet Height

• Design Variables• Control Points on the NURBS Patch, -1.8 x/D 0.5

Liou, M.-S. and Lee, B. J., “Minimizing Inlet Distortion for Hybrid Wing Body Aircraft,” ASME J. Turbomachinery, Vol. 134, #3, 2012.Lee, B. J. and Liou, M.-S., “Optimizing Shape of Boundary-Layer-Ingestion Offset Inlet Using Discrete Adjoint Method,” AIAA J. Vol. 48, No 9, 2008-2016, 2010.

• Design FormulationMinimize :

Subject to :

zi : z coordinate of ith control point

zL : limit of design variable (10% of Inlet Height)

Detailed Flow Structures: Near Inlet Throat

Y/D=0.5 Plane

Eliminated lip flow separation

flow separation at lip Establishing a global pressure field, resulting in flow acceleration

Performance at Off-design Conditions

• Simultaneous improvements in total pressure recovery and distortion

• Superior performance is maintained by the optimized design at all off-design conditions

Oil Flow Patterns at Off-Design Conditions

A0/Ac=0.533 A0/Ac=0.401A0/Ac=0.506

Baseline Model

A0/Ac=0.557

Optimized Model

A0/Ac=0. 523 A0/Ac=0. 423

Inlet-fan Coupling

• Mitigate deficiency in traditional specification of outflow pressure condition for assessing the inlet performance

• Direct coupling of, hence specification by the fan operating condition

• Need for fan flow analysis– Full-scale simulation– Reduced-order modeling

Reduced-order Model for Fan Flow

• R4 Fan—1/5-scaled model tested in NASA Glenn Research Center, 22 in. diameter and 22 blades

• Reduced-order model built based on the CFD solutions

1.26

1.28

1.30

1.32

1.34

1.36

1.38

35 36 37 38 39 40 41 42 43 44 45

Fan

pres

sure

ratio

Corrected mass flow (kg/s)

Fan test data [Hughes]

Swift

Euler + body force

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

0.045

0.05

35 37 39 41 43 45

del_

S / R

Corrected mass flow rate (kg/s)

Fan test data [Hughes]

Euler + body force

The Need for Analyzing Integrated Configuration

Propulsion Model for N2-B

Effects of Propulsion System Installation

Impacts on Flowfield and Aerodynamic Performance

Inlet Performance

AIP1 AIP2 AIP3 AIP4 AIP5

X=0.740

X=0.718

X=0.800

X=0.777

Outer inlet Center inlet

AIP1 AIP2 AIP3 AIP4 AIP5Present simulation 0.9650 0.9758 0.9644 0.9401 0.9553Boeing estimation 0.9671 0.9751 0.9671

0.92

0.93

0.94

0.95

0.96

0.97

0.98

0.99Recovery

N/A N/A

Design Optimization

• Nacelle geometry• Minimize drag, and• Minimize distortion

Drag Minimization

-0.05

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

CL

AOA (deg)

Clean wing

N2B

Design 1

Design 2

Distortion Minimization

X=0.740

X=0.718

AIP1 AIP2 AIP3

X=0.740

X=0.718

AIP1 AIP2 AIP3

N3-X

• Turbo-electric distributed propulsion (TeDP)• Targeted benefits: fuel burn savings by 70% relative to Boeing

777-200LR, M=0.84

Why Electric Propulsion• Exhaust of current

airplanes, CO2, NOx, particulates, … contributes climate changes

• Noise mitigation• Allowing solar energy as

power source

Solar Impulse II

Fan Model

1.38

1.40

1.42

1.44

1.46

1.48

1.50

1.52

1.54

38 40 42 44 46 48

Fan

pres

sure

ratio

Corrected mass flow (kg/s)

Clean inflow + R4 ( Exp) [Hughes]Clean inflow + R4 (Body force)Inlet A + R4 (full CFD) [Webster et al.]Inlet A + R4 (Body force)

0.70

0.75

0.80

0.85

0.90

0.95

38 40 42 44 46 48

Stag

e ad

iaba

tic e

ffici

ency

Corrected mass flow (kg/s)

Clean inflow + R4 (Exp) [Hughes]

Inlet A + R4 (Body force)

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

0.045

0.05

15 20 25 30 35 40 45 50

del_

S /

R

corrected mass flow rate (kg/s)

100%95%

87.5%77.5%

70%

60%

50%

Flowfield near and inside the propulsion system

Centerplane of Outermost passage

Symmetry place

Propulsion Performance

0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.95

1.00

110 120 130 140 150 160

Fan

effici

ency

Corrected mass flow rate (kg/s)

Clean inflow CFD (SWIFT)

Installed on N3-X

81

1.15

1.20

1.25

1.30

1.35

1.40

1.45

110 120 130 140 150 160Fa

n pr

essu

re ra

tioCorrected mass flow rate (kg/s)

Clean inflow CFD (SWIFT)

Installed on N3-X

81

Design by Drag Minimization

Optimized

Baseline

Concluding Remarks & Outlook

• Using high fidelity analysis and optimization in early design phase can reveal areas of importance and shed insight on technological challenges.

• Have discovered an effective way to improve inlet performance, without sacrificing system efficiency.

• Geometry, geometry, geometry …• MDAO has received considerable emphasis, developed

fast, and its future for prime time is very promising.

Leonardo di ser Piero da Vinci

April 15, 1452~May 2, 1519, Florence, Italy

Thank you for your attention andBest wishes!

http://www.youtube.com/watch?feature=player_embedded&v=FWvgpngKIW4

http://www.solar-impulse.com/

Keep up your dream,Look up to those pioneering dreamers, and

Follow their spirits.