engine noise reduction technologies and strategies … · 17.11.2005 · engine noise reduction...

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National Aeronautics and Space Administration

www.nasa.gov

Engine Noise Reduction Technologies AndStrategies for Commercial Applications

Dennis L. HuffNASA Glenn Research Center

Cleveland, Ohio

Fellows Lecture SeriesPratt & Whitney, United Technologies

November 17, 2005

Thanks to Drs. James Bridges, Edmane Envia, Daniel Sutliff and Joe Grady

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Outline

• Introduction to Engine Noise Research at NASA

• Fan Noise

• Jet Noise

• Engine Noise and Future Opportunities

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Introduction to Engine Noise Research at NASA

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Technology Benefit: Reduced Noise Exposure

1997 BaselineKey

55 dB

65 dB

Airport

0 10Miles

20

10

5

• 5 dB Reduction (TRL 6)• Doesn’t meet public

expectations• Constrained growth

AST Technology Benefit(Advanced Subsonic Technology)

20

10

5

20

10

5

• 10 dB reduction • 65 dB contour is within airport• Enables projected air travel growth• Reduces community noise impact

QAT Technology Benefit(Quiet Aircraft Technology)

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Quiet Aircraft Technology (QAT) Sub-Projects

Engine Noise• Fan Noise• Jet Noise

Aircraft Operations

Aircraft Goal: 10 dB Quieter than 1997 Technology

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Engine Noise Sources

(PW8000)

(P&W PW8000 Engine, Conceptual)

FanStator

Compressor

Combustor

Turbine

Exhaust

Inlet

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Major Engine Noise Test Facilities at NASA Glenn

9x15 Wind Tunnel

W8 Fan Rig

AeroAcoustic Propulsion Lab

Test Facilities Provide Component-Level Noise Assessments

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Fan Noise

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Power (dB)Power (dB)Mode: (m,n)Mode: (m,n)Power (dB)Power (dB)Mode: (m,n)Mode: (m,n)

TotalTotal

((--4,1)4,1)

((--4,0)4,0)

CutCut--On Stator (1xBPF)On Stator (1xBPF)

114 114 112112

102 102 9898

101 101 103103

100 100 9797

113 113 111111

CutCut--Off Stator (2xBPF)Off Stator (2xBPF)

TotalTotal

((--10,3)10,3)

((--10,2)10,2)

((--10,1)10,1)

((--10,0)10,0)

125 125 125125

120 120 120120

124 124 124124

Downstream Tone LevelsDownstream Tone LevelsPrediction Prediction DataData

CutCut--Off Stator (54Off Stator (54--Vanes)Vanes) CutCut--On Stator (26On Stator (26--Vanes)Vanes)Fan Noise Prediction (LINFLUX Code)

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Goal:Goal: Develop a 3D timeDevelop a 3D time--accurate nonlinear fan noise prediction code.accurate nonlinear fan noise prediction code.

Status:Status: The development of the 3D code is completed and the code isThe development of the 3D code is completed and the code isbeing validated using wind tunnel data.being validated using wind tunnel data.

1xBPF1xBPF 2xBPF2xBPF 3xBPF3xBPF

m =

m

= -- 1

010

m =

m

= -- 1

010

m =

+12

m =

+12

m =

m

= -- 4

242

CutCut

-- offoff

CutCut

-- offoff

Re (pRe (p’’))

++

--

Computed Solution for a 2D Benchmark ProblemComputed Solution for a 2D Benchmark Problem

State-of-the-Art Capability

Fan Noise Computational Aero Acoustics (BASS Code)

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Weight FlowWeight Flow

Pre

ssur

e R

atio

Pre

ssur

e R

atio

Fixed Fan Nozzle AreaFixed Fan Nozzle Areaoptimum incidence at design point onlyoptimum incidence at design point only

Variable Fan Nozzle AreaVariable Fan Nozzle Areaoptimum incidence at offoptimum incidence at off--design pointsdesign points

50%50%

100%100%

Max Efficiency LocusMax Efficiency Locus

Motivation: Motivation: Improved Incidence Improved Incidence →→ Less Noise Less Noise Benefits:Benefits: Reduced Noise / Enhanced PerformanceReduced Noise / Enhanced Performance

nominalnominalopenopen

Fan Noise Reduction: Variable Area Nozzle

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Noise Benefit: 2.0 dB (unNoise Benefit: 2.0 dB (un--optimized)optimized)

400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600Corrected Stage Thrust, lbf

-10

-5

0

5

DeltaOverallSound PowerLevel,

dB

Nozzle areaFlight nozzle - zero reference+5% flow area+7.5% flow area

Increasednoise

Decreasednoise

nominalapproach

|

nominalcutback

|

nominaltakeoff

|ApproachApproach CutbackCutbackTakeoffTakeoff

Stage Thrust, Stage Thrust, lbflbf

Nominal Nozzle (Baseline)Nominal Nozzle (Baseline)+5.4% Open+5.4% Open+10.9% Open+10.9% Open

NoiseNoiseDecreaseDecrease

NoiseNoiseIncreaseIncrease

9 x 15 Wind Tunnel Test Results

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Motivation: Motivation: Reduce rotorReduce rotor--stator interactionstator interactionnoise by reducing vane pressure fluctuationsnoise by reducing vane pressure fluctuations

Benefits:Benefits: Passive SystemPassive System

Hollow ChambersHollow ChambersFilled ChambersFilled Chambers(Porous Beads)(Porous Beads)

Porous SurfacePorous Surfacewith Cover Sheetwith Cover Sheet

Sketch of Soft Vane CrossSketch of Soft Vane Cross--SectionSection

“Soft” Stator Vanes

Testbed: ANCF Fan Rig

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54555657585960616263646566

0 8 16 24 32 40 48 56 64 72 80 88 96 104

SPL (dB)

Shaft Order

AlV

SV

56575859606162636465666768

0 250 500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000

SPL (dB)

Freq (Hz)

AlV

SV

FWD (38.6°)

AFT (135°)

HardwareHardware Fan Rig DataFan Rig Data

Measured Noise Benefit: 1.5 dB (un-optimized)

Low-Speed Fan Rig Results

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Trailing Edge Blowing

blowing air

internal blade passages

Testbed: ANCF Fan Rig (TRL 3)

Testbed: 9x15 Wind Tunnel

Benefits:Reduced Fan Noise

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Trailing Edge Blowing – ANCF Demo

Click Here for Audio Demo

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Benefits:Reduced Fan NoisePassive System

Fan Aft Duct Acoustic Splitter

Test completed in the 9x15 Wind Tunnel

Treated Splitter

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d

1.67d

One-inch Chevrons(d = 10%c)

Half-inch Chevrons(d = 5%c)

Baseline Blade

Motivation: Motivation: Enhance rotor wake mixing to reduce rotorEnhance rotor wake mixing to reduce rotor--stator stator interaction noiseinteraction noise

Benefits:Benefits: Passive SystemPassive System

Fan Trailing Edge Chevrons (GE)

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Wake Harmonic ContentWake Harmonic Content

1BPF 2BPF 3BPF 4BPF 5BPF0

20

40

60

80

100

1BPF 2BPF 3BPF 4BPF 5BPF-25

-20

-15

-10

-5

0

5

Am

plitu

de, d

B

Am

plitu

de R

el. t

o B

asel

ine,

dB

80

Baseline5%5% droop10%10% droop

Potential for Tone Noise Reduction

Fan Trailing Edge Chevrons - Cascade Test Results

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Over-the-Rotor Acoustic TreatmentHaynes 25 Metal Foam

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Haynes 25 Foam “Flight Worthiness” Tests

• Flammability test: HA25 foam unaffected by 1000oC/30 min in a burner rig. Long life in oxidizing environment to at least 800oC.

• Immersion tests: HA25 foam specimens with a variety of size and shapes in various fluids such as water, skydroll, advanced hydraulic fluid and jet fuel (2 hr immersion + 2 hr ambient drying). Does not readily absorb fluids.

• Stress Tests : Mechanical properties surveyed, including compression, bending, tensile (w/face sheets). Can withstand expected mechanical loads.

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Haynes 25 Broadband Noise Spectra

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Jet Noise

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FlowInstabilities

EnergyConversion?

Propagation

Current Jet Noise Paradigm

Thrust

Turbulence

Acoustic Source Strength

Noise

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Good prediction of cold jet noise spectra at 90°

…and at aft angles!

After QAT: JeNo

New Advanced Jet Noise Prediction Code: JeNo

• Improvements rolled into new prediction code– CFD Turbulence– Acoustic Source Models– Adjoint Green’s Function Propagation

Before QAT

Ma=0.9 cold

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Advancements in Turbulence Measurements

• Particle Image Velocimetry (PIV, Wernet & Bridges)• Turbulence measurements in hot jets• Two-point space-time velocity correlations in hot jets• Cross-Stream Stereoscopic PIV

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Time-Dependent PIV

Time-dependent PIV setup in AAPL

QuickTime™ and aBMP decompressor

are needed to see this picture.

A 13x75mm region spanning from jet centerline through fan-core shear layer to outer fan stream shear layer is captured just downstream of plug of separate flow nozzle at takeoff conditions. Two components of velocity are captured at 150 points at 10kHz for 1.1 second (~0.1s shown here). Mean velocity subtracted to highlight unsteady flow. Click Here for Demo

Flow Direction

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Advancements in Source Distribution Measurement

Near-Field Emission Array*

RRC Polar Correlation Array

Internal Mode Propagation Array*3D Phased Array*

1D Phased Array

2D Array at GE Engine Stand

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M=0.9, cold, 90° observer

PredictionPhased Array

Jet Noise Source DistributionPhased Array vs Prediction

• Phased array provides detailed diagnostic on prediction process

• Shows where noise reduction efforts should be concentrated

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Freq (Hz)1/

3O

ctav

eS

PL

(dB

)102 103 10450

60

70

80BaselineAlt Chevron

φ=90°Far-field Sound Spectra

Developing Mixing Enhancement Concepts

• Balance among competing factors:– decreased low frequency noise– increased high frequency noise – maintaining thrust performance

Turbulent Kinetic EnergyBaseline

Alt Chevron

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Flow Shielding Concepts

• Use non-axisymmetric plume and refraction to give favorable directivity

• Fan-stream vanes, wedge (U Cal Irvine), S-duct (LaRC)

101

102

103

30

40

50

60

70

80

Full-Scale Frequency (Hz)

φ=135°

Baseline

Vanes

UC Irvine Results

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Validating Small Scale Results

• Fan Vanes at Bypass ratio 5

f (Hz)

SPL

(dB/

Hz)

102 103 104

70

80

90

100

110

120

3BB 4V θ=150 Baseline3BB 4V θ =150 'towards vanes'

NASA GRC

θ = 150°

f (Hz)S

PL(d

B/H

z)

102 103 104

70

80

90

100

110

120

UCI 3BB 4V θ =150 'towards vanes'UCI 3BB θ =150 Baseline

UCI

Baseline

Vanes

Fair confirmation for vanes at BPR 5

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Extend Results to Higher BPR

• Fan Vanes at Bypass ratio 8

f (Hz)

SP

L(d

B/H

z )

102 103 10470

80

90

100

θ = 90°

f (Hz)

SP

L(d

B/ H

z )

102 103 104

70

80

90

100

110

120

θ = 150°

Baseline

Vanes

Benefit reduced for vanes at BPR 8… 0.4 EPNdB reduction best achieved

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Engine Noise and Future Opportunities

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Jet Noise Reduction With Chevron Nozzles

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Engine Noise Diagnostic Testing at Honeywell

Engine:Honeywell HTF7000 Tech Demonstrator

2005/06 Engine Tests Include:• Internal flow measurements • Microphone arrays to map

engine acoustic field • Fan noise modal measurements • In-situ impedance measurement

Noise Reduction Technologies:• Forward-Swept Fan • Advanced acoustic liners

Small Demonstrator Supports Business & Regional Jet Applications

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VANTake-Off

CruiseLow Noise Because of:• Low fan tip speed• Low jet exhaust velocity

Enabling Technologies:• Fan drive gear system

• Variable area fan nozzle

Additional Noise Reduction Advanced Technologies

Wind Tunnel Fan Operability Test Planned for 2006

Ultra-High Bypass “Advanced Geared Turbofan”

Design of Low Noise Engine Initiated at P&W

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Quiet Airplanes of the Future - Takeoff

Advanced Engines & Airframe• Lower Fan Tip Speeds• Lower Jet Exit Velocities• Variable Area Nozzle• “Soft” Fan Stator Vanes• Fan Trailing Edge Blowing• Bypass Acoustic Splitter• “Toboggan” Landing Gear

Fairings• Continuous Mold Line Flap• Slat Cove Filler

Airport BoundaryProjected level required for objectionable noise to be contained within airport boundary.

Predicted Source Noise ReductionRelative to Current Fleet Average

Take-Off Condition

-24

-20

-16

-12

-8

-4

0Current Fleet Advanced

Engines &Airframe

AirportBoundary

EPN

dB

Click on picture to play sound demo:

Inlet Aft

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Quiet Airplanes of the Future - Approach

Advanced Engines & Airframe• Lower Fan Tip Speeds• Lower Jet Exit Velocities• Variable Area Nozzle• “Soft” Fan Stator Vanes• Fan Trailing Edge Blowing• Bypass Acoustic Splitter• “Toboggan” Landing Gear

Fairings• Continuous Mold Line Flap• Slat Cove Filler

Airport BoundaryProjected level required for objectionable noise to be contained within airport boundary.

Predicted Source Noise ReductionRelative to Current Fleet Average

Approach Conditions

-24

-20

-16

-12

-8

-4

0Current Fleet Advanced

Engines & Airframe

AirportBoundary

EPN

dB

Click on picture to play sound demo:

Inlet Aft

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Significant noise reduction can be achieved with the combination of engine cycle change and advanced noise reduction technologies

Further cycle changes will be difficult

Quiet Airplanes of the FutureEngine Cycle versus Noise Reduction Technologies

Engine OnlySource Noise Reduction

Relative to Current Fleet Average

-24

-20

-16

-12

-8

-4

0UHB Cycle UHB with

NoiseReduction

Technologies

AirportBoundary

EPN

dB

Take-offApproach

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Dual Fan – Conceptual Applications

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154.2”Fan Diameter

Single Fan On Blended Wing Body (BWB)

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105.1”Fan Diameter

Dual Fan On Blended Wing Body (BWB)

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Summary

• Engine noise reduction research has concentrated on fan andjet components, many ideas have been investigated overthe past 10-15 years.

• Source diagnostic experiments and advanced flow/acousticmeasurement methods have been key to understandingnoise generation, developing prediction tools, and identifyingnoise reduction strategies.

• Significant engine noise reduction will be achieved with theintroduction of Ultra-High Bypass Ratio engines (low-speedfans, low jet velocities), noise reduction technologies will bemore effective.

• We hope to continue our strong partnerships with industryand universities, significant progress has been made workingtogether through programs like AST and QAT.

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Backup Charts

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Progress in Turbofan Engine Noise Research Over Past 10 Years

Fan Noise• Prediction for wake/stator interaction based on 3D sources with realistic mean flows• Improvements in source description due to better understanding of wake disturbances• Reduction methods concentrate on stators, experiments quantify rotor alone source strength• Active noise control successful for multiple tones, but require complex/expensive integration• Duct propagation methods validated for axisymmetric nacelles

Jet Noise• Prediction improvements from CFD/RANS and acoustic source/propagation methods• Significant reduction for separate flow nozzles using chevron mixing devices• Improved space-time correlations with non-intrusive unsteady flow measurements (hot jets)• Phased array source identification methods

Core Noise• Limited progress due to emphasis on fan and jet (dominant sources)• Improved empirical models using engine data• Combustion noise reduction using tailcone Helmholtz resonators

Engine System Noise• Most significant noise reduction comes from newer engine cycles with lower fan

tip speeds and lower jet exhaust velocities (higher bypass ratio engines)• Limited progress in system noise assessment with emphasis on component technologies

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Unsolved Problems for Engine Noise ResearchGeneric• LES/DNS methods for source prediction, hybrid methods => Establish NASA COE across centers• Source identification methods for internal/external flows (phased arrays, etc.)• Trailing edge noise generation physics• Turbulence measurement and prediction methods for hot high-speed flows

Fan Noise• Physical understanding and modeling of rotor generated noise sources• Prediction methods for supersonic fan tip speeds, non-linear prediction method for MPT’s• Reliable rotor transmission/reflection model• Physical/computational predictions for advanced acoustic liners and impedance measurements• Broadband noise prediction

Jet Noise• Hot jet source prediction including mixing and shock noise• Noise reduction strategies without reducing jet exhaust velocities

Core Noise• Non-empirical prediction methods for combustors, compressors and turbines• Source identification methods when other sources like the fan and jet dominate

Engine System Noise• Noise propagation methods for complex geometries and shear flows• Unified component prediction method (start with combining fan/jet source models)• Reliable data base for engine noise sources particularly for newer engines• Noise reduction strategies through engine placement studies and advanced cycles

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“Toboggan” Landing Gear Fairings

Benefits:Reduced Gear Noise

Flight Test In August 2005

Source Identification

Wind Tunnel Test

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Continuous Line Mold Flap & SlatCove Filler

Noise reduction devices mounted on wing in wind tunnel

Low-Noise Wing

Baseline: High Noise Regions

Benefits:Reduced Flap and Slat Noise

engine noise reduction technologies and strategies … · 17.11.2005 · engine noise reduction...

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