Subsonic Civil Transport Aircraft for 2035: An...

Subsonic Civil Transport Aircraft for 2035:

An Industry-NASA-University Collaborative Enterprise

MIT / Aurora / Pratt & Whitney

Technology Lead: Alejandra Uranga [email protected] Engineer: Mark Drela [email protected] Investigator: Edward Greitzer [email protected]

AIAA SciTech 2015January 5, 2015

Summary

I MIT, Aurora Flight Sciences, Pratt & Whitney, NASA working together todevelop concepts for a 2035 subsonic transport aircraft

I Experiments, computations, and analysis to climb the TRL ladder

I Large scale powered experiments in NASA Langley 14⇥22 footSubsonic Wind Tunnel

I New engine concepts to power this aircraft

I Achieved project objectives

I BLI benefit assessmentI Engine conceptsI Technology development

I BLI benefit quantified to give ⇠ 8% power saving for a realisticconfiguration, the D8

I Proof-of-concept of BLI for civil transports

MIT N+3 Phase 2 AIAA SciTech 2015 1 / 29

Outline

1 Introduction

2 The D8 Aircraft Concept

3 BLI Benefit

4 High E�ciency, High OPR Small Cores

5 Summary and Conclusions


University-Industry-NASA CollaborationUniversity

IIndependent examination of concepts

IEducation of next generation of engineers

Industry

IAircraft and engine design, development

IProduct knowledge

NASA

IBridging TRL gap between university and industry

INational facilities for experimental assessment of ideas, computational examination

of flow fields

Collboration within and between organizations

IPhase 1: ⇠30 people including 5 faculty, 6 students

IPhase 2: ⇠>30 people including 2 faculty, 3 sta↵, 9 students

Program driven by ideas and technical discussions ) changes in “legacy” beliefs


NASA Sets Aggressive Technology Goals

In 2008, NASA put forward an N+3 request for proposals:

What would it take to develop an aircraft for the 2025-2035

timeframe which could meet the future civil transport challenges?


Source???

Fuel Burn and NASA Goals

0

2

4

6

8

10

12

14

16

18

20

1.E+06 1.E+07 1.E+08 1.E+09

PFEI(kJ/kg1km)

Productivity.(Payload*Range,?kg1km)

B737-800

B777-200LR

70% Reduction.D8.3

70% Reduction.

50#best#aircra,#within#global#fleet##

Produc7vity##(Payload#×#Range,#kg.km)#

PFE

I

B737-800

70%#Reduc7on# D#Series#

Fuel#Burn#

PFEI#(kJ/kg. km)#


E. Greitzer et al. 2010, NASA CR 2010-216794

Industry-University Team MembersCecile Casses⇤

Je↵ Chambers (Aurora)

Austin DiOrio⇤+

Mark Drela

Alex Espitia⇤

Sydney Giblin (Aurora)+

Adam Grasch⇤+

Edward Greitzer

David Hall⇤

Jeremy Hollman (Aurora)

Arthur Huang

David Kordonowy (Aurora)

Jennie Leith

Bob Liebeck

Michael Lieu⇤

Wesley Lord (P&W)

Roedolph Opperman (Aurora)⇤

Sho Sato⇤+

Nina Siu⇤

Ben Smith (Aurora)

Gabriel Suciu (P&W)

Choon Tan

Neil Titchener

Alejandra Uranga

Elise van Dam⇤

* Graduate Students+ Non-current

Plus 13 undergratuate studentsPlus others at P&W and Aurora


The D8 Aircraft ConceptMIT 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

�37% fuel with current tech(configuration)

�66% fuel with advanced tech(2025-2035)

No “magic bullet”


A. Uranga et al. 2014, AIAA 2014-0906

System Impact of BLI

BLI benefitsI

Aerodynamic (direct) benefitsI Reduced jet and wake dissipationI Reduced nacelle wetted area

ISystem-level (secondary) benefits

I 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)



M. Drela 2011, AIAA 2011-3970

A. 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

1

88 %

81 %

82 %

67 %

66 %

100 %

op

tim

ize

d7

37

-8

00

M=

0.8

,C

FM

56

en

gin

e

0

slow

to

M=

0.7

2

1

D8

fu

se

la

ge,

pita

il

2

re

ar

po

dd

ed

en

gin

es

3

in

te

gra

te

de

ng

in

es,

BL

I

4

op

tim

ize

en

gin

eB

PR

,F

PR

5

20

10

en

gin

es

8

Fuel

Burn

63 %

D8.2

6 7 9 10

20

35

en

gin

es

20

35

ma

te

ria

ls

win

gb

ot.

NL

F

sm

art

stru

ct

48 %

38 %

35 %

34 %

D8.6

- 15 %


Phase 2 Research Thrusts

Task 1: airframe-propulsion system integration

I Define/design aft section of D8: integration of engines into fuselage

I Quantify aerodynamic benefit of boundary layer ingestion (BLI)

I Propulsor performance with distortion from BLI

I Phenomena, expected (and unexpected) behavior

I Combined experimental and computational approach



How

I Direct, back-to-back comparisonof non-BLI and BLI configurations(podded) (integrated)

I Turbomachinery characterization

Tools

I Analytical analysis (1D power balance)

I Experiments at NASA Langley14⇥22 wind tunneland MIT tunnels

I Computational studies

I Close collaboration with NASA


Goals of Phase 2, Task 1

1 Define/design aft-section of D8


Photos NASA/George Homich

Goals of Phase 2, Task 1

2 Quantify aerodynamic benefit of BLI for D8-type configuration

8.4% with equal nozzle area10.5% with equal mass flow

3 Develop methodology for studying aircraft configurations with BLI

4 Define technology road map for the D8: next steps to increase TRL


BLI Analysis

I Ambiguous decomposition into drag and thrust(airframe) (propulsion system)

I Use power balance method instead of force accounting

I BLI reduces wasted KE in combined jet+wake

wake, or “draft”

WastedKinetic Energy

Zero NetMomentum

combined wake and jet

propulsor jet

+

+

+

+

+

+

+

-

-

-


M. Drela 2009, AIAA Journal 47(7)

BLI Benefit


non-BLI(Podded)

BLI(Integrated)

Metric: Mechanical flow power, PK

, transmitted to the flow by propulsors

BLI benefit =P

K

non-BLI

� P

K

non-BLI

P

K

non-BLI

⇡ 8% to 10%

Non-BLI (Podded) Configuration


Photo NASA/George Homich

0 50 in10

BLI (Integrated) Configuration


Photo NASA/George Homich

0 50 in10

Survey Propulsor Inlet and Outlet


Rotating rake systemin wind tunnel experiments

Total Pressure

Inlet Rake

Total Pressure

Exit Rake

Integrated Propulsor Ingested Flow


Experiments Left propulsor Right propulsor BL profile

Total pressure coe�cient Cp

t

=p

t

� p

t1

q1

z

Dfan

y/Dfan

-0.6 -0.4 -0.2 0 0.2 0.4 0.6

0

0.2

0.4

0.6

0.8

1

1.2

-0.75 -0.5 -0.25 0

0

0.2

0.4

0.6

0.8

1

1.2

Left

Right

-1

-0.8

-0.6

-0.4

-0.2

0

-0.6 -0.4 -0.2 0 0.2 0.4 0.6

y/Dfan

z

Dfan

y/Dfan

-0.6 -0.4 -0.2 0 0.2 0.4 0.6

0

0.2

0.4

0.6

0.8

1

1.2

-0.75 -0.5 -0.25 0

0

0.2

0.4

0.6

0.8

1

1.2

Left

Right

-1

-0.8

-0.6

-0.4

-0.2

0

-0.6 -0.4 -0.2 0 0.2 0.4 0.6

y/Dfan

↵ = 2�

11 kRPM(cruise)

↵ = 6�

13 kRPM(climb)

“Benign” stratified flow

Importance of Experimental Results

I Wind tunnel experiments ! proof-of-concept

I Assessment of D8 configurationI Aerodynamic performanceI Computations crucial in data reduction and interpretation

I First back-to-back assessment of BLI vs non-BLI

I BLI benefit results applicable to full-size aircraft when usingmechanical flow power as performance metric computations


Outline

1 Introduction

2 The D8 Aircraft Concept

3 BLI Benefit

4 High E�ciency, High OPR Small Cores

5 Summary and Conclusions


N+3 D8 Engine Requirements

I D8.6 N+3 conceptual aircraft, engine bypass ratio (BPR) ⇠ 20

I Low drag (low thrust), high pressure ratio imply decrease incompressor exit corrected flow, flow area, to 1.5 lbm/s (CFM 56 has7 lbm/s)

m

pT

t

Ap

t

= f (Mexit) or corrected flow = Aexitf (Mexit)

I Implies blade heights < 0.4” – with conventional architecture


High E�ciency, High OPR Small Core Compressors

I What mechanisms limit small core compressor e�ciency?I Low Reynolds numberI Tip gaps relative to chordI Manufacturing accuracy

I How can we mitigate e↵ects of size on e�ciency?

I What are mechanical constraints for engine layout and rotordynamics?

I Big fan – small core



Task 2: high e�ciency, high pressure ratio small core engines

I Limits to performance

I Technology opportunities for performance enhancement

I Innovative propulsion system architectures



© 2013 United Technologies Corporation!This document has been publicly released.

(c) 2013 United Technologies Corporation!Not subject to the EAR per 15 C.F.R. Chapter 1, Part 734.3(b)(3).

Cores Shrink As Efficiency Improves!

Year of Introduction

0

0.2

0.4

0.6

0.8

1

1.2

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1970 1980 1990 2000 2010 2020 2030

Efficiency

Relative Core Size, 1974=1

0.4

0.2

0

0.6

0.8

Core Sizeat constant thrust

lines are curve fits to data!

page 4!

Efficien

cy(

Rela,ve(Core(Size(1974(=(1(

[Epstein, 2013]

1

Cores Shrink As Efficiency Improves [Epstein 2013]

High E�ciency, High OPR, Small Core Challenges

I Disk burst “1-in-20 rule”

I Close-coupled exhausts

I Propulsive e�ciency with BLI

I Performance of small core turbomachinery

I Engine architecture and structural integration


Accomplishments 1/2

I Determined BLI benefit in first back-to-back BLI vs non-BLIcomparison

10.5±0.7% at equal mass flow8.4±0.7% at equal nozzle area

I Scaling for experimental BLI quantificationI BLI benefit quantification and uncertainty assessmentI No show-stoppers for D8 concept

I Determined propulsor inlet distortion for BLI aircraft

I Observed fan e�ciency loss to be much less than total BLI benefit(1–2% versus 15%)


Accomplishments 2/2

I Defined approaches to mitigate e↵ects of distortion onturbomachinery performance

I Tradeo↵s di↵erent than for “conventional” fan operation

I Identified mechanisms and drivers for small core, high e�ciency, highOPR compressor technology

I Carried out conceptual design of small core engineI Architecture enables flow path with decreased non-dimensional tip

clearanceI Architecture enables meeting of 1-in-20 rule


Acknowledgments

Funding

NASA Fundamental Aeronautics Program, Fixed Wing Projectunder Cooperative Agreement NNX11AB35A

Thanks to

Sta↵ at NASA Langley 14⇥22 Foot Subsonic Wind Tunnel

NASA Fixed Wing Project management

N. Cumpsty, Y. Dong, A. Epstein, E. Gallagher, A. Murphy, J. Sabnis,G. Tillman, H. Youngren


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