GREEN AVIATION PROPULSION SYSTEM CHALLENEGES & …

GREEN AVIATION

PROPULSION SYSTEM CHALLENEGES & SOLUTIONS

Jayant Sabnis

Chief, System Functional Design

Pratt & Whitney

NASA Green Aviation Summit

September 8-9, 2010

Mountain View, CA

© 2010 United Technologies Corporation. All rights reserved. No part of this publication may be

reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic,

photocopying, recording or otherwise without the prior written permission of the copyright owners

Powering Change

Powering Change

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© 2010 United Technologies Corporation.Subject to restrictions on the title page

PROPULSION SYSTEM REQUIREMENTSNoise And Fuel Burn Reduction

Reduced Fuel Burn

Reduced TSFC

Reduced Propulsion System Weight

Reduced Propulsion System Drag

Reduced Propulsion System Noise

Lower Jet Velocity

Lower Fan Tip speed

Lower Turbine Noise

Reduced Emissions

2

Powering Change

Com

bust

or

Jet

Eng

ine

Tota

l

Airc

raft

Tota

l

Turb

ine

Com

pres

sor

Fan

ENGINE SOURCE NOISE COMPONENTS


Fan and Jet Mixing Noise Are the Dominant Engine Sources

Fan Noise ~ V 5tip Jet Noise ~ Vjet6

Airf

ram

e5 dB

Com

bust

or

Jet

Eng

ine

Tota

l

Airc

raft

Tota

l

Airf

ram

e

Turb

ineC

ompr

esso

Fan

5 dB

Low Noise Requires Low Jet Velocity (hence Low FPR) anr d Low Fan Tip Speed

Typical Takeoff Distribution(Fan, Jet)

Typical Approach Distribution(Fan, Turbine, Airframe)

3

Powering Change

FUNDAMENTAL PROPULSION SYSTEM CHARACTERISTIC


Fuel Burn Reduction And Noise Reduction At Conflict With Each Other!

Fuel Burn

Fan Diameter

Noise

(Higher FPR) (Lower FPR)

Low

High

State-of-

The-ArtNoise

Fuel

Burn Advanced

Components

A380 Engines

4

Powering Change

FUNCTIONAL DESIGN CHALLENGE

Reducing Fuel Burn AND Noise

Powering Change

•

FUNCTIONAL ELEMENTS OF AIRCRAFT ENGINE

Propulsor, Gas Generator & Power Turbine

PROPULSOR (PR)

– Produce Thrust from Shaft Power (By Pushing on Air)

aka Fan / Propeller / Air Screw / Prop Fan / UDF / Open Rotor–

• POWER PLANT

– Produce Shaft Power from Chemical Fuel Energy

GAS GENERATOR (GG)

o “Heat Engine” to Convert Fuel Energy into Fluid Power

Delivers High-Pressure, High Temperature Gas (Drives PT)o

POWER TURBINE (PT)

o Convert Fluid Power to Mechanical (Shaft) Power

Drives Propulsoro


6

Powering Change

PERFORMANCE MODEL FOR TURBOFAN ENGINE


V0 VJ

7

Powering Change


Three-Step Power Conversion Process

• Step 1 : Gas Generator (GG)– Convert Ambient Air Into High-Pressure High-Temperature Gas

Thermal Efficiency (ηth = GG Power / Fuel Heat Release)–


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Powering Change




– Thermal Efficiency (ηth = GG Power / Fuel Heat Release)

• Step 2 : Shaft Power– Convert GG Power Into Shaft Power To Propulsor

Transfer Efficiency (ηx = Shaft Power / GG Power )–


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Powering Change




– Thermal Efficiency (ηth = GG Power / Fuel Heat Release)

• Step 2 : Shaft Power– Convert GG Power Into Shaft Power To Propulsor

– Transfer Efficiency (ηx = Shaft Power / GG Power )

• Step 3 : Propulsive Power– Convert Shaft Power Into Propulsive Power

Propulsive Efficiency (ηp = Propulsive Power / Shaft Power)–


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Powering Change




= X X

o TH X P

=

Overall

Efficiency

Thermal

Efficiency

Transfer

Efficiency

Propulsive

Efficiency

GG Power

Fuel Heat Release

Shaft Power

GG Power

Propulsive Power

Shaft Power

11

Powering Change

0.65

0.7

0.75

0.8

0.85

0.9

0.95

1

1 1.1 1.2 1.3 1.4 1.5 1.6 1.7FPR

Fa

n P

rop

uls

ive

Eff

icie

nc

y

M0 = 0.80

fan

Nfan

PfanSHP

VF 0

PROPULSIVE EFFICIENCY FOR FAN BYPASS SYSTEM

Ideal Fan P is Only a Function of FPR

and Flight Speed


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Powering Change

0.65

0.7

0.75

0.8

0.85

0.9

0.95

1

1 1.1 1.2 1.3 1.4 1.5 1.6 1.7FPR

Fa

n P

rop

uls

ive

Eff

icie

nc

y

M0 = 0.80



and Flight Speed


Internal Losses

in Fan Stream

fan

Nfan

PfanSHP

VF 0

13

Powering Change

0.65

0.7

0.75

0.8

0.85

0.9

0.95

1

1 1.1 1.2 1.3 1.4 1.5 1.6 1.7FPR

Fa

n P

rop

uls

ive

Eff

icie

nc

y

M0 = 0.80



and Flight Speed


Internal Losses

in Fan Stream

fan

Nfan

PfanSHP

VF 0

14

Powering Change

0.65

0.7

0.75

0.8

0.85

0.9

0.95

1

1 1.1 1.2 1.3 1.4 1.5 1.6 1.7FPR

Fa

n P

rop

uls

ive

Eff

icie

nc

y

M0 = 0.80



and Flight Speed


Internal Losses

in Fan Stream

fan

Nfan

PfanSHP

VF 0

15

Powering Change

0.65

0.7

0.75

0.8

0.85

0.9

0.95

1

1 1.1 1.2 1.3 1.4 1.5 1.6 1.7FPR

Fa

n P

rop

uls

ive

Eff

icie

nc

y

M0 = 0.80



and Flight Speed


Internal Losses

in Fan Stream

fan

Nfan

PfanSHP

VF 0

16

Powering Change

0.65

0.7

0.75

0.8

0.85

0.9

0.95

1

1 1.1 1.2 1.3 1.4 1.5 1.6 1.7FPR

Fa

n P

rop

uls

ive

Eff

icie

nc

y

M0 = 0.80



and Flight Speed


Internal Losses

in Fan Stream

Aim to Achieve the Propulsive Efficiency

Benefit of Turboprop and Noise Benefit of Turbofan

fan

Nfan

PfanSHP

VF 0

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Powering Change

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 10 20 30 40 50 60 70

Cycle

Th

erm

al

Eff

icie

ncy

OPR

T4/T2 = 8.0

T4/T2 = 5.0

Ideal Cycle

GAS GENERATOR THERMAL EFFICIENCYHigh Th High OPR, High T4.1 & Low-Loss Turbomachinery

Thermal Efficiency Improvements are Reaching Point of Diminishing Returns


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Powering Change

THE POWER TURBINE DILEMMADirect Drive System Limits Potential of Low FPR Low-RPM Fan Engine

Direct Coupling of Low-RPM Fan with LPT Drives Higher Stage Count and Larger Diameter for LPT.

Fan and LPT Efficiencies are Compromised and Weight and Maintenance Costs Increase

LPT Size Challenges Installation

Paradigm Shift

Abandon Direct Drive

Gear System to Get High RPM Power Turbine with Low RPM Fan Fan Diameter

•

•


Lo

w-S

poo

l W

eig

ht D

elta

DDTF

60 70 80 90

1400

1200

1000

800

600

400

200

0

-200

GDTF

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Powering Change

POWER TURBINE / TRANSFER EFFICIENCYHigh-Speed Power Turbine Enables Installation, Low Weight & High Efficiency

Direct-Drive

LPT

High-Speed LPT

Dh/U2

1.5 %

Direct-Drive

LPT

L

PT


2

3

4

5

6

7

8

9

10

1.2 1.3 1.4 1.5 1.6 1.7

SAI DDTF

SAI GDTF

DDTF

GDTFSta

ge

Co

un

t

1.2 1.3 1.4 1.5 1.6 1.7FPR

10

9

8

7

6

5

4

3

2

0.3

0.35

0.4

0.45

0.5

0.55

0.6

0.65

1.2 1.3 1.4 1.5 1.6 1.7

DL

PT/D

FA

N

DDTF*

GDTF

Source:

Flowpath: Janes

FPR: PW est.

1.2 1.3 1.4 1.5 1.6 1.7FPR

0.65

0.60

0.55

0.50

0.45

0.40

0.35

0.30

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Powering Change

FUNDAMENTAL PROPULSION SYSTEM CHARACTERISTIC


Gear Driven Propulsor Enables Improved Fuel Burn AND Lower Noise

Fuel Burn

Fan Diameter

Noise

(Higher FPR) (Lower FPR)

Low

High

State-of-

The-ArtNoise

Fuel

Burn Advanced

Components

Increasing weight of Low-RPM

LPT contributes to increasing

fuel burn

Paradigm

Shift

Noise

Reduction

Fuel Burn

Reduction

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Powering Change

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CHALLENGES AND OPPORTUNITIESLow Pressure Ratio Propulsors Present New Opportunities

Characterize Performance of Low Pressure Ratio Propulsors

– Efficiency, Noise, Distortion Tolerance

• Installation Challenges

– Propulsion system / Aircraft Interaction

• Novel Installation Concepts

• Novel Aircraft Configuration

– Embedded Installation

• Rig / Wind Tunnel Experiments

• System Demonstrators


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GREEN AVIATION PROPULSION SYSTEM CHALLENEGES & …