Message & Goals - Noise Solutions

1

©2007 CMI - Silent Aircraft Initiative

The information in this document is the property of the CMI Silent Aircraft Initiative and may not be copied or communicated

to a third party without prior written consent.

INTEGRATION OF NOISE CONTROL INTO THE

PRODUCT DESIGN PROCESS: A CASE STUDY –

THE SILENT AIRCRAFT INITIATIVE

Andrew Faszer

Noise Solutions Inc.

2007 Spring Conference on

Environmental & Occupational

Noise

22-25 May 2007

301, 206 – 7th Ave SW

Calgary, AB T2P 0W7

[email protected]

©2007 CMI - Silent Aircraft Initiative Slide 2, 22-25 May 2007

The information in this document is the property of the CMI Silent Aircraft Initiative and may not be

copied or communicated to a third party without prior written consent.

Message & Goals

� With high risk of technologies used in conceptual design,

objectives of “silent” and fuel efficient aircraft are met

� Roll out conceptual Silent Aircraft design:

- High level design overview (what)

- New ideas and enabling concepts (how and why)

- Risk assessment and mitigate (what if)

2




CUED/MIT Silent Aircraft Team ~ 35 Researchers

H.-C. Shin -

Acoustic Measurements

& Phased Array Design

High-Lift:

C. Andreou - Slats / Suction

A. Townsend - L.E. Rot Cylinder

Y. Liu -

Scattering Effects:

Surface finish

A. Quayle -

Undercarriage

A. Faszer -

Aerofoil Trailing Edge

J. Hileman - 3D Aero Design

A. Jones - Optimization

A. Agarwal – Acoustic Shielding

Former Members:

A. Diedrich - SAX10 planform

P. Freuler - Inlet Design

D. Tan - Noise propagation modeling

G. Theis – Economics

N. Sizov – Operations

R. Morimoto - Economics

C. Hope – Economics

K. Sakaliyski – Drag Rudders / Spoilers

P. Collins - KIC Manager

Faculty: A. Dowling, E. Greitzer, H Babinsky, P. Belobaba,

J.-P. Clarke, M. Drela, C. Hall, W. Graham , T. Hynes, K. Polenske,

Z. Spakovszky, I. Waitz, K. Willcox, L. Xu

E. de la Rosa Blanco - In-depth engine analysis/design

D. Crichton - Fan & variable nozzle design

R. Tam - Economics

T. Reynolds - Operations

P. Shah, D. Mobed - Engine air brake

T. Law - Exhaust nozzle design

S. Thomas - Vectored thrust / Aircraft control

V. Madani - Inlet design

A. Plas - Effect of boundary layer ingestion on fuel burn

M. Sargeant - Inlet/airframe integration / 3D Airframe CFD

Chief Engineers: J. Hileman and Z. Spakovszky




Key Questions Addressed

Existence of Solution?

Starting with a blank piece of paper, could one design a mid-range

passenger aircraft that is inaudible outside a typical airport?

Comparability?

How does this ‘silent aircraft’ compare to existing and next

generation aircraft in terms of fuel burn and emissions?

3




The Challenge

20251975 201520051995198519651955

20 dB

Turbojets

ACARE 2020 target

Silent Aircraft Initiative Target

Entry into service date

Perc

eiv

ed

No

ise

Le

ve

l

SAX-

40

Year of Introduction

Boeing 777

1955 1965 2005199519851975 2015 2025

3

2

1

0

data cited from Lee, Lukachko,

Waitz, and Schafer (2001)E

nerg

y U

se

, M

J/A

SK

?

Noise Reduction Goal Fuel Burn Competitiveness

Comparability?Existence of Solution?

?2025

2025




Enabling Technologies

� Advanced, highly efficient airframe centerbody design

� Advanced airfoil trailing edge treatment

� Faired undercarriage

� Deployable drooped leading edge

� Quiet drag via increased induced drag

� Embedded, boundary layer ingesting, distributed propulsion system

� Variable area exhaust nozzle and ultra-high bypass ratio engines

� Airframe shielding and optimized extensive liners

� Optimized take-off thrust management

4




� Engines close to c.g.

� Tail required for pitch trim

� Wing and tail fuel tanks

� Draggy fuselage – no lift

Noise Reduction Challenge – Conventional A/C

Approach configuration Cruise configuration

Advanced wing design




� Noise reduction challenge: jet

and turbomachinery noise,

airframe lift discontinuities,

cavities and edges

� Limited low speed

performance

Noise Reduction Challenge – Conventional A/C

Approach configuration

5




� Start with conventional wings (e.g. supercritical airfoils)

Roadmap to a Silent Aircraft




� Start with conventional wings (e.g. supercritical airfoils)

� Transform fuselage into lifting surface


6




� Embed the propulsion system to shield turbomachinery noise and to ingest

airframe boundary layers





� Issue: highly loaded outer wing yields nose down moment – re-cambered

profiles and relatively large control surfaces yield performance penalty


Cruise configuration

7




� Camber LE and twist outer wing to balance moments on cruise and achieve

elliptical lift distribution


Cruise configuration

0.0

0.1

0.2

0.3

0.0 0.2 0.4 0.6 0.8 1.0

Spanwise Coordinate (Eta)

CL

* C

/ C

ref




� Balance pitching moment with centerbody camber and unload trailing edge

on approach increased induced drag for quiet, low speed approach


Cruise configurationApproach configuration

0.0

0.1

0.2

0.3

0.0 0.2 0.4 0.6 0.8 1.0

Spanwise Coordinate (Eta)

CL

* C

/ C

ref

8




SAX Genealogy

Granta-252 (4 Engines)

SAX-10

SAX-10: First Generation Design

� Based on Boeing PW planform design tool

� Optimized on maximum take-off weight

� 4 Granta-252 engines

� First industry non advocate reviews

SAX-20: Second Generation Design

� 3D airframe design methodology

� Design for low stall speed for to reduce noise

� 3 Granta-3201 clusters

� Boeing Phantom Works design review and

3D viscous analysis

SAX-40: Third Generation Design

� Optimized outer wing using 3D design methodology

� Elliptical lift distribution

� Distributed propulsion: 3 Granta-3401 clusters

� Second industry non-advocate reviews

Geared Low Pressure Turbine

No Boundary Layer Ingestion




SAX Genealogy

SAX-20












3D viscous analysis





� Second industry non-advocate reviewsBoundary Layer Ingestion

Gear and Transmission Concepts

9




SAX Genealogy











3D viscous analysis





� Second industry non-advocate reviews

SAX-40


Boundary Layer Ingestion

Detailed Transmission Concepts




Silent Aircraft Conceptual Design – SAX-40

Design process iterative, optimized for low noise and improved fuel burn

Fuel Burn potential of 149 pax-miles per imperial gallon (121 for B777)

Noise estimated as 63 dBA outside airport perimeter (background noise)

10




SAX-40 Major Design Features

Cruise:

Mach: 0.8

Altitude: 40,000 – 45,000 ft

(12,190 – 13,720 m)

L/D: 25.1 – 23.5

Static margin: 5.9% – 9.5%

CG travel: 1.3 ft (0.4 m)

Deployable

Drooped L.E.

Elevons

Winglet

Rudder

Thrust Vectoring,

Variable Area Nozzle

SAX-40 Cruise ML/D: 20.1

Boeing PW BWB ML/D : 17-18 1

Boeing 777 ML/D : 17 2

Span: 221.6 ft (67.54 m) incl. winglet

Gross Area: 8,998 ft2 (835.9 m2)

MTOW: 332,560 lbs (150,850 kg)

OEW: 207,660 lbs (94,190 kg)

Structure: 104,870 lbs (47,570 kg)

Payload: 51,600 lbs (23,400 kg)

Fuel: 73,310 lbs (33,250 kg)

Faired

Undercarriage

Centerbody BLI

Centerbody

LE CamberRange: 5,000 nm

Pax: 215 (3 class)

1. Liebeck, R., Journal of Aircraft, vol. 41, no. 1, 2004.

2. Boeing communication, 2006




Granta-3401 Major Design Features

High Capacity,

Low Speed Fan

Distributed propulsion

system

Transmission system to transmit

power from Low Pressure Turbine

Low noise Low Pressure

Turbine - 5 stages

Variable area nozzle

Low Idle Thrust

Extended

acoustics liners

Ingestion of centerbody

boundary layer

Axial-radial compressor

Fan Diameter: 1.20 m

Engine Length: 2.46 m

Cruise Fuel Flow: 0.86 kg/s

Bare weight: 2,978 kg / cluster (6,566 lbs)

Installed weight: 5,469 kg/ cluster (12,058 lbs) 24.248.8OPR

18.312.3BPR

1.191.50FPR

Take-offTop of Climb

11




SAX-40 Four-View Rendering

144.3 ft / 43.98 m35.4 ft / 10.79 m

221.6

ft

/ 67.5

4 m




SAX Noise Overview

Analyzed noise from SAX taking off / landing at a hypothetical

runway, typical of a large international commercial airport

SAX airport: 1.0 km - 3.0 km runway - 1.0 km, 0.45 km to side

LHR airport: 0.7 km - 3.9 km runway - 1.0 km, 0.45 km to side

Airport Perimeter

Runway: 3,000 m

Approach 2.0 km from

displacedthreshold

Displaced Threshold

1,000 m beyond runway start

Landing Field Length: 1,900 m; 118.2 knots

Distances for Approach Noise Analysis

Temp: ISA+12°C

Airport Perimeter

4.0 km from brakes off

Perimeter: 1,000 m

from end of runway

Runway: 3,000 m

Sideline

Cutback

Perimeter: 1,000 m from

beginning of runway 450 m from runway edge

Distances for Takeoff Noise Analysis

ICAO/FAA Cert. Point6.5 km from brakes off

12




Sideline Noise Estimate

Challenge at Outset:

� Sideline noise

dominated by jet

and fan buzz-saw

Solution:

� High thrust and low

jet velocity using

variable area nozzle

� Extensive liners

� Airframe shielding

� Airframe design for

enhanced low

speed performance

63 dBA




Cutback Noise Estimate

61 dBA Challenge at Outset:

� Jet noise reduction

with steep, low

speed climb-out.

Solution:

� Takeoff power

management and

variable area nozzle

� Extensive liners

� Airframe shielding


enhanced low

speed performance

13




Approach Noise Estimate

63 dBAChallenge at outset:

� Airframe, fan, and

turbine noise.

Solution:

� No flaps or slats.

� Displaced threshold.

� Undercarriage fairing.


enhanced low speed

performance.

� Deployable drooped

leading edge.

� Low noise LPT design.

� Trailing edge brushes.

� Low engine idle thrust.




Boeing 777

SAX-40

Year of Introduction

1955 1965 2005199519851975 2015 2025

En

erg

y U

se, M

J/A

SK

3

2

1

0

Fuel Efficiency

Non-SAX data cited from Lee,

Lukachko, Waitz, and Schafer (2001)

In addition to quiet, analysis

suggests high fuel efficiency.

14




Emission predictions: total Carbon and NOx

Total CO2 emission is 89.5 g per pass-nm

Total NOX emission is 0.22 g per pass-nm

Low noise solution expected to have low pollutant emission

Low pollutant emission primarily a result of low aircraft fuel burn

SAX- 40

Silent Aircraft carbon emission

compared to other transport

(adapted from the IPCC, 1999)

Single Occupant Light TruckTwo Occupant Small Car

Cars/Light Trucks

Buses/Trams

Passenger Trains

Air Travel

Short HaulMedium HaulLong Haul

High-Speed Trains, Coal-Fired ElectricityNon-Fossil Electricity

City Bus Low-Occupancy, High Comfort

g C per passenger-km




Silent Aircraft

Enabling

Technologies

1. Advanced Operations

2. Quiet Airframe Design

3. Engine-Airframe Integration

4. Engine Design

15




Enabling Technologies 1: Advanced Operations

Low noise approach procedures:

� Slow approach = reduced V

� Displaced threshold = increased d

� Continuous Descent Approach

(CDA) = increased d & lower engine

engine thrust

Departure procedures

� Thrust-managed take-off =

optimised jet V and d

2

n

d Distance,

V Velocity,SPL Noise, ∝

� Aircraft noise scales with velocity (raised to a power, n≥5) and

inversely with the squared distance from the aircraft to the ground




Idea

� Displace the landing threshold 1 km down the

runway compared to a standard approach

Benefits

� Increases the aircraft altitude at the airport

perimeter by 170 ft (52m) = 5 dBA reduction.

� Helps wake avoidance with operations on

closely spaced parallel runways (e.g. Frankfurt)

Requirements

� Additional runway lights, markings, guidance

systems (e.g. Instrument Landing System [ILS],

Precision Approach Path Indicator [PAPI]).

� Further research into effects on operations

Displaced Threshold T. Reynolds

26L threshold

25L threshold

25L approach

lights

26L approach lights

25L PAPI

26L PAPI

Adapted

from

[Fraport

(2006)]

[adapted from

Fraport (2006)]

RiskFuelNoise

16




Thrust-managed take-off D. CrichtonFuelNoise Risk

0 1000 2000 3000 4000 50000

2

4

6

8

10

Distance from brakes off, m

Clim

b a

ng

le, d

eg

ree

s

Aircraft

Engine out limit

Idea

� Continuously vary thrust, climb angle and nozzle area during take-off to maintain set noise level outside airport boundary

Benefits

� Significant reduction in take-off noise

� Ensures noise level met at all timeduring departure

� Matches sideline and flyover noise levels

Requirements (for maximum benefit)

� High cruise altitude and enhanced

airframe take-off performance

� Multiple engine configuration (3 or more)




Enabling Technologies 2: Quiet Airframe Design

Source treatment and elimination

Enhanced low speed performance

Centerbody

design

Undercarriage

Fairing & Simplification

Deployable Drooped

Leading Edge

Thrust Vectoring /

ElevonsFlap Elimination

Trailing Edge

Brushes

17




Idea

� Cambered leading edge balances

aerodynamic forces without tail.

Benefits

� Low approach speed with minimal cruise

performance penalty.

� Elliptical lift distribution and zero trim drag

to minimize cruise drag.

� Improved aircraft stability.

� Reduced elevator power requirement.

Challenges

� Non-circular pressure vessel.

� Accurate structural weight estimation.

� Low speed aerodynamic analysis.

Centerbody Design J. Hileman

Boeing

CFD

Solution

SAX-29

Design

Method

Solution

Span

Lif

t

RiskFuelNoise




Idea

� Deploy drooped leading edge to

achieve required lift during low

speed operations

Benefits

� Elimination of slat noise

� Achieves SAX-40 high lift requirements

� Stowed in cruise for optimum performance

� Deployment power levels comparable

to a conventional slat

Requirements

� For low speed approach, airframe design

must compensate for slightly lower lift

� In service on the Airbus A380

Drooped Leading Edge C. AndreouRiskFuelNoise

0 2000 4000 6000 8000

Frequency

Slat

Stowed

Drooped

20

dB

18




Benefits

� Remove flap noise, intense

airframe noise source.

Requirements

� Need significant quiet drag

generation.

� Advanced cockpit display for

runway visibility at high cabin

angle.

Flap Elimination J. Hileman

Idea

� Instead of flaps, use large wing area and high angle

of attack to achieve low approach speed.

Current

Technology

RiskFuelNoise




Idea

� Use combination of elevons and thrust vectoring

to increase induced drag while trimming aircraft.

Benefits

� Provides pitch and drag trim without deployable

drag generation device.

� Combination enables take-off rotation.

Requirements

� Continuous moldline technology for

low noise elevon.

� Thrust vectoring nozzle with

range of motion between -25° and 25°.

Elevon Deflection / Thrust Vectoring

Deployable

Drooped L.E.

Elevons

Thrust Vectoring

Cruise Configuration

Approach Configuration

Span

Lif

t

S. Thomas

RiskFuelNoise

19




Idea

� Enhanced controller to enable low speed

handling.

Benefits

� During a low speed approach, the aircraft is

robust to disturbances and pilot variability.

� Silent approach: the aircraft can land safely

and quietly, even in moderately windy

conditions.

Requirement

� During high gust conditions, a faster

approach speed is necessary to ensure safe

operation (+3 dBA).

Low Speed Handling S. ThomasRiskFuelNoise

Distance Along Ground, m

He

igh

t, m

Flight Path

Gust Height

300

200

10000 2000




T.E. Brushes

Idea

� During approach, use trailing edge brushes to

reduce scattering of turbulence from airfoil trailing

edges. Similar technolody to owls.

Benefits

� Reduce airfoil trailing edge noise by 4 dBA.

� Minimal impact on aerodynamics.

Requirements

� Brush length of 3.8% of local chord.

� Split elevons on outer wings to

allow for brush deployment.

Based upon analysis of Herr and Dobrzynski, AIAAJ Vol. 43, 2005.

Trailing Edge Brushes A. FaszerRiskFuelNoise

20




Undercarriage – clean-up / fairings

(250Hz)

A. QuayleRiskFuelNoise

Idea

� Noise reduction due to smooth flow around landing gear

Benefits

� Eliminate all surface details

(7 dBA at high frequencies).

� Partially enclose wheels and axles to eliminate noise sources

(6 dBA at low-mid frequencies).

Requirements

� Alternative drag sources (during approach)

� Low weight fairing

� Alternative to visual inspection

� Brake cooling




� Distributed propulsion arrangement allows for small fan diameter (Df).

� Extended acoustic liners ahead

and behind the engine made

feasible by small fan diameter.

� Embedded configuration

enhances airframe shielding

and enables boundary

layer ingestion.

Enabling Technologies 3: Engine-Airframe Integration

Acoustic Liners

EngineNozzle

2Df2Df2Df 0.5Df

21




Idea

� Placing the engines above the

airframe prevents engine noise

from reaching the observer

Benefits

� Engine forward noise sources

virtually eradicated on the

ground

Requirements

� Engines located above the wing

� Source needs to be moved close

to wing for maximum benefit

Airframe Noise Shielding A. Agarwal

SAX 40 Fan Forward Noise at Flyover

RiskFuelNoise




Idea

� Embed the engines within the airframe

Benefits

� Enables extensive liner use

� Enhances engine noise shielding

� Enables boundary layer ingestion

� Reduces propulsion system weight

� Reduces installation drag

Requirements

� Intake design which is matched

to the airframe

� Engine access

Propulsion System Integration M. SargeantRiskFuelNoise

22




Idea

� Ingest centerbody boundary layer

Benefits

� Improves engine propulsive efficiency

� Reduces fuel burn

Requirements

� Fan design which can cope with the

distortion caused by the boundary layer flow

� For maximum benefit, need distributed

propulsion system

Boundary Layer Ingestion M. Sargeant

Begin Cruise

A. Plas

RiskFuelNoise




Distributed propulsion systemE. de la Rosa Blanco

RiskFuelNoise

Idea

� Embedded, multiple fan, engine configuration with aft transmission system

Benefits (relative to single fan –single core)

� Reduced fan rearward and forward noise

� Reduced fuel burn

� Reduced fan diameter for improved acoustic liners

� Reduced system weight and length

Requirements / Challenges

� Transmission system to split the power from the LPT into the three fans

23




Idea

� <summarise idea here>

Benefits

� <add benefits here>

Requirements

� <add requirements here>

Inlet Ducts V. Madani

Idea

� Fully integrated intakes designed for

minimum fan-face flow-distortion.

Benefits

� Reduces drag and enables boundary

layer ingestion.

� Mitigates aerodynamic and mechanical

problems associated with inlet distortion.

Requirements/Challenges

� Difficult to balance competing acoustic,

distortion and loss requirements.

� Distortion levels still a challenge.94.6% Pressure Recovery

RiskFuelNoise




Idea

� Optimized multi-segment acoustic

liner for engine installation

Benefits

� Significant reduction of engine

noise sources (20 dBA)

Requirements

� Noise benefits improve as fan

diameter is reduced.

� Airframe capable of housing the

duct geometry

� Performance losses due to the

long nozzle must be acceptable

Acoustic Liners T. Law

SAX 40 Fan Rearward Noise at Flyover

RiskFuelNoise

24




Enabling Technologies 4: Engine Design

Distributed

propulsion

system

Transmission system to split

the power from the LPT

Low noise Low

Pressure Turbine

Variable area nozzle

Low Idle Thrust

High Capacity,

Low Speed Fan




0 2000 4000 600020

25

30

35

40

45

50

Distance from brakes off, m

% in

cre

ase

in

no

zzle

are

a r

ela

tive

to

To

C

Idea

� Increase nozzle area during take-off to provide high mass flow and low

jet velocity. Reduce nozzle area at top of climb and cruise to provide

required thrust.

Benefits

� Large jet noise reduction.

� Optimum cruise performance.

� Enables operation at low fan

speed.

Requirements

� High cruise altitude and good airframe

take-off performance.

� Low weight aerodynamic design.

� SAX-40 requires thrust vectoring Variable Area Nozzle.

Variable Area Nozzle D. CrichtonRiskFuelNoise

25




Idea

� Design for use with variable area nozzle.

� Use forward sweep to increase part speed capacity.

� Set design point fan pressure ratio to meet jet noise

target.

Benefits

� Fan can deliver high mass

flow low velocity jet.

� Critical flyover position at

peak fan efficiency

� Reduced fan source noise

Requirements

� Outlet Guide Vanes must support high

incidence range

High Capacity, Low Speed FanD. Crichton

RiskFuelNoise




Idea

� Reduce tonal noise by increasing the Low Pressure

Turbine rotational speed and the number of rotor

blades.

� Avoid noise scattered at low frequencies by using a

blade number ratio around unity.

Benefits

� Reduce tonal noise and avoid scattered noise.

� Significant reduction in axial chord. Therefore,

reduction in turbine length and weight.

Requirements

� Further research on Low Pressure Turbine

broadband noise.

Low Pressure Turbine E. de la Rosa BlancoRiskFuelNoise

26




Idea

� Use variable area nozzle to enable ultra low engine rotational speed during approach and meet go-around manoeuvre requirement

Benefits

� Reduced approach airframe drag requirements

� Reduced rearward fan noise� Engine speed reduced to 45% of design

speed (Top of Climb)

Requirements

� High levels of compressor bleed to ensure operability

� Fan operability sets nozzle area variation

Low Idle Thrust E. de la Rosa Blanco

.9

1

1.1

1.2

1.3

1.4

1.5

1.6

1.7

P1

32

L

300 400 500 600 700

Mass Flow W2RStd [kg/s]

LPC

0. 4

0.5

0.6

0.7

0.8

0.9

1

0.93 0

.92

0.91 0.90 0.88 0.85 0.80 0.70 0.60 0.50 0.40

ToC

ApproachTop of Climb

Approach

Mass Flow

Fan P

ressure

Ratio

RiskFuelNoise




Conventional Engine vs. Granta-3401

27




Risk Assessment

Have considerable risk with propulsion system and

airframe design.

Are these risks justified?

Conducted independent analyses:

1. Assessed technology contributions to noise and fuel

burn, Mountains Chart.

2. Alternative, lower risk podded aircraft design.

3. Sensitivity studies




Technology Assessment

28




Risk Mitigation Plan

� The all-lifting wing airframe leads to lower noise as

well as delivering a large fuel burn reduction

� Embedded, distributed propulsion combined with

boundary layer ingestion enables lower fuel burn as

well as lower noise, but the technology is high risk.

� A lower risk design should have:

- All-lifting wing airframe

- Podded UHBR engines with variable area exhaust nozzles

- Mixed exhaust with extensive acoustic liners

- Power managed take-off and displaced threshold




Requirements for Viability

Market viability

Societal acceptance

Aircraft certification

Technical challenges:

� Propulsion system / airframe integration (inlet distortion noise,

forced vibration issues, gear-drive, etc.)

� Structural analysis and manufacturability of non-circular pressure

vessel

� Mechanical design of thrust vectoring and variable area nozzle

� Low speed aerodynamic performance

� Cabin layout with assessment of interior vibration and noise

� Maintenance considerations

29




Summary

� Have achieved a credible conceptual aircraft design given the high

risk of the technologies used

� Met objectives of a functionally “silent” and fuel efficient aircraft

� New conceptual aircraft has potential for:

- Fuel Burn of 149 pax-miles per imperial gallon (121 for B777)

- Noise of 63 dBA at airport perimeter (background noise)

� Assessed high risk technologies and outlined mitigation plan

Message & Goals - Noise Solutions

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