Workshop on Jet Exhaust Noise Reduction for Tactical Aircraft - NASA Perspective · · 2013-04-10Workshop on Jet Exhaust Noise Reduction for Tactical Aircraft - NASA Perspective

Workshop on Jet Exhaust Noise Reduction for Tactical Aircraft - NASA Perspective

Dennis L. Huff

NASA Glenn Research Center

and

Brenda S. Henderson

NASA Langley Research Center

Jet noise from supersonic, high performance aircraft is a significant problem for takeoff and landing operations near air

bases and aircraft carriers. As newer aircraft with higher thrust and performance are introduced, the noise tends to

increase due to higher jet exhaust velocities. Jet noise has been a subject of research for over 55 years. Commercial

subsonic aircraft benefit from changes to the engine cycle that reduce the exhaust velocities and result in significant

noise reduction. Most of the research programs over the past few decades have concentrated on commercial aircraft.

Progress has been made by introducing new engines with design features that reduce the noise.

NASA has recently started a new program called “Fundamental Aeronautics” where three projects (subsonic fixed

wing, subsonic rotary wing, and supersonics) address aircraft noise. For the supersonics project, a primary goal is to

understand the underlying physics associated with jet noise so that improved noise prediction tools and noise reduction

methods can be developed for a wide range of applications. Highlights from the supersonics project are presented

including prediction methods for broadband shock noise, flow measurement methods, and noise reduction methods.

Realistic expectations are presented based on past history that indicates significant jet noise reduction cannot be

achieved without major changes to the engine cycle. NASA’s past experience shows a few EPNdB (effective

perceived noise level in decibels) can be achieved using low noise design features such as chevron nozzles. Minimal

thrust loss can be expected with these nozzles (< 0.5%) and they may be retrofitted on existing engines. In the long

term, it is desirable to use variable cycle engines that can be optimized for lower jet noise during takeoff operations

and higher thrust for operational performance. It is also suggested that noise experts be included early in the design

process for engine nozzle systems to participate in decisions that may impact the jet noise.

https://ntrs.nasa.gov/search.jsp?R=20080005558 2018-06-20T19:12:48+00:00Z

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National Aeronautics and Space Administration

www.nasa.gov

Workshop on Jet Exhaust NoiseReduction for Tactical Aircraft

- NASA Perspective

November 27, 2007

by Dennis L. Huff and Brenda S. Henderson

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www.nasa.gov

Good News: High performance military aircraft noise isdominated by a single source called “jet noise”(commercial aircraft have multiple sources)

Bad News: This source has been the subject of resear chfor the past 55 years and progress has beenincremental.

• Major jet noise reduction has been achieved through changingthe cycle of the engine to reduce the jet exit velo city.

• Smaller reductions (a few EPNdB) have been achieved usingsuppression devices like mixing enhancement, acoust ic liners.

• Significant jet noise reduction without any perform anceloss is probably not possible!

History Shows The Problem Is Difficult To Solve

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777-200

A330-300

MD-90-30

MD-11

A320-200

747-400

A300-600R

767-300ERA310-300757-200

MD-87MD-82

B-747-300A300B4-620

A310-222

MD-80

B-747-200

B-747-SPDC-10-40

B-747-200

A300

B-747-200

B-747-100

B-737-200B-737-200

B-727-200DC9-10

B-727-100

B-727-100

20.0

-10.0

0.0

10.0

1960 1970 1980 1990 2000 2010 2020Year of Entry (Approximate)

Average NoiseLevel Relativeto Stage 3(EPNdB)

Stage 2

Stage 3

Stage 4

Averagein Service

Aircraft Noise Trends

F15

F16

F14

F18Military, After BurnerMilitary, Dry

NASA Technology Goal(-42 dB Cum)

B-737-800B-737-900

A320-232

A340-541

A318-112

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Supersonic Jet Noise Sources

Tam, C.K.W., Directional Acoustic Radiation From a Supersonic Jet Generated by Shear LayerInstability, Journal of Fluid Mechanics , Vol. 46, Pt. 4, Apr. 27, 1971, pp. 757-768.

• Turbulent Jet Mixing• Broadband Shock Noise• Screech

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Recent NASA Noise Reduction Research Programs

High Speed Research (HSR) Program• 1990 - 1999• Focused research on specific engine & mission (mixe d-flow turbofan)

Advanced Subsonic Technology (AST) Noise Reduction Program• 1993 - 2001• Applied research for commercial turbofan engines wi th emphasis

on fan and jet noiseQuiet Aircraft Technology (QAT) Project

• 2001 - 2005• Research for new subsonic commercial engines to mee t aggressive 10 dB

and 20 dB noise reduction goals (relative to 1997 b est-in-fleet technology)Fundamental Aeronautics (FA) Program

• 2006 - present• Supersonic & subsonic fundamental research aimed at understanding

noise sources, also working on rotorcraft noise• Emphasis on Multi-Disciplinary Design and Optimizat ion (MDAO) tool

development

Noise research for subsonic applications outpaces supersonic work by a large margin!

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NASA Lear 25 Flight Demonstrationof Turbojet Noise Reduction

Objectives

• Confirm model scale test results• Determine flight effects of installed

chevron nozzle• Investigate chevron nozzles for

supersonic jet exit velocities

6 and 12 Point Chevron Nozzles

Approach• Completed model scale acoustic and

performance tests • Demonstrated 3 EPNdB jet noise

reduction with 0.5% thrust loss• Flight test in March 2001 on

Learjet 25 with CJ610-6 enginesshowed ~2 EPNdB jet noise reduction

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NASA Lear 25 Flight Demonstrationof Turbojet Noise Reduction

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NASA’s Fundamental Aeronautics Program

Overcome today’s national challenges in air transpo rtation

• Invest in fundamental core competencies

• Involve external aeronautics community to support b est technological talent and ideas

• Widely disseminate research results

Four projects

• Subsonic Fixed Wing

• Subsonic Rotary Wing

• Supersonics

• Hypersonics

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Supersonics Project

Major technical challenges• Efficiency

• Environment

•Airport noise

•Sonic boom

•High-altitude emissions

• Performance

• Entry descent and landing

• Multidisciplinary design, analysis, and optimization

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• Enable vehicles capable of economical supersonic flight to be acoustically compatible with existing fleet around airports.

• Envision noise reduction technologies which break current overall noise trends of noise vs specific thrust.

• Create design and analysis tools to evaluate and optimize noise along with other aircraft performance measures.

Airport Noise - Technical Challenge

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Airport Noise - Technical Approach

•Elements

– Prediction

– Diagnostics

– Engineering

•Significant interaction between elements

• Internal and external NASA Research Announcement (NRA) research folded into program to meet project objectives

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Prediction

•Statistical modeling in supersonic jet noise

– Mixing noise, shock noise, and Mach wave emission

•Time-resolved CFD/CAA for jet aeroacoustics

– LES for non-compact sources, LEE for complex propagation in shocked flow

•Assessment of supersonic noise prediction tools

– Empirical, statistical, and time-resolved codes

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90

85

80

75

70

65

60

55 10.00 5.00 1.00 0.50 0.10 0.05 0.01

70 deg

Strouhal number

SP

L -

10 L

og (

A)

- 52

.5 L

og (

Vj/a

), d

B

Tt / Ta = 3.2

M=1.38

• No method exists to predict broadband shock-associated noise for general jet geometries and conditions

• Acoustics and flow-field measurements to be performed at small and moderate scale

• Steady RANS flow simulation coupled with source modeling based on measured unsteady flow properties will provide noise prediction

• Separation of shock-associated noise from other jet noise sources accomplished using new empirical method

• Close collaboration between Penn State, Boeing and NASA – good progress in all sub-tasks

Schlieren image of jet shock cell structure

RANS predictions of shock-containing jets

Separation of mixing and shock noise

Shock noise

Mixing noise

Prediction and Measurements of Broadband Shock-Associated Noise

PI: Philip J. Morris, Penn State U.

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Diagnostics

•Phased array diagnostics for source distribution

– Combine flow and acoustic array measurements

•Turbulence statistics for noise prediction codes

– Mixing noise, shock noise, Mach wave emission

•Supersonic aeroacoustic database

– Far-field noise and source distribution for range of geometries (dual stream, round, rectangular, twin)

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JES

Linear ArrayPhased Array

Wall Mic

LSAWT Phased Array Experiment

• Detailed source distribution maps obtained for subsonic and supersonic jets using conventional beamforming

• Next step - DAMAS deconvolution to resolve shock noise source distribution in plume

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Application of Time-Resolved PIV to Supersonic Hot Jets

Advanced turbulent velocity measurements yield space-time statistics required to model jet noise sources and validate CFD-based prediction codes.

NASA Glenn AeroAcoustic Propulsion Lab

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S-DuctY-Duct

Angle Adapter

Twin Jet

Investigate• Jet plume interactions• Noise characteristics of

rectangular nozzles

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Engineering

•Broadband shock noise reduction through shock modifications

– Air injection

•Offset stream nozzles for noise reduction

•Unsteady actuator for time-dependent jet control

– LES-optimized temporal control of jet instabilities and medium-scale testing

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Strategic Environmental Research & Development Program

Investigate• Noise characteristics of

realistic nozzle geometries• Impact of bypass flow on

acoustic radiation and noise reduction devices

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Air Injection

Noise reduction can be achieved in single and dual stream jets

Fan Nozzle Core Fluidic Chevron Nozzle

Air Supply

30

40

50

60

70

80

90

100 1000 10000 100000Frequency (Hz)

SP

L (d

B)

IPR = 1.0IPR = 2.0IPR = 4.0

NPRc = 2.17

θ = 61o

40

50

60

70

80

90

100

100 1000 10000 100000

Frequency (Hz)

SP

L (d

B)

IPR = 1.0

IPR = 2.5

IPR = 4.0

NPRc = 1.61

NPRf = 2.23

θ = 61o

Shock Noise

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Realistic Expectations

• With history as a guide, don’t expect this problem to be solved soon.

• High performance aircraft cannot rely on engine cyc le benefits the waycommercial aircraft have met large noise reduction targets.

• Commercial aircraft have benefited from sustained n oise reductionresearch. This has not been done for high performa nce aircraft engines,which means the foundation for this research is les s mature.

• Small reductions in jet noise (a few EPNdB) are exp ected to be possible withsmall performance penalties (< 0.5%). Retrofitable solutions may be possible(i.e. Chevron Nozzles).

• Large reductions in noise will require a long-term research commitment andconsideration for noise during initial design of en gine. Variable cycleengines are needed to make significant progress.

• Modified aircraft operations for noise abatement is a good solutionfor community noise problems. Barriers, acoustic e nclosures, and earprotection are the most practical solutions for nea r field noise problems.

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(Back-Up Slides)

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Pinker, R.A., “A Brief Review of the Source Noise TechnologyApplicable to Fixed-Wing Military Aircraft”, AGARD- CP-512, Combat Aircraft Noise, 1991)

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Highlights From NASA’s HSR Program

Noise research focused on improving low bypass rati o turbofans with variablegeometry mixer-ejector nozzles

• Mixer on primary flow reduces low frequency jet noi se• Acoustic liners absorb high frequency noise• Fan inlet noise issue during approach, addressed th rough improved design

Major Technology Improvements

• Better mixer designs aided by 3-D CFD (reduced thru st loss)• Improved acoustic liners (higher temperature, lower weight)• Technology available to provide engine that can mee t commercial

certification requirements (Stage III with ~2-4 dB margin => Stage IV)• Improved materials technology beat original engine weight goals

Jet noise reduction achieved, but required heavy mixer-ejector nozzle

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High-Speed Civil Transport Jet NoiseModel Test Data Projections

Gross Thrust Loss

PRE 1972TECHNOLOGY

(SST)

POST 1990TECHNOLOGY

(HSCT)

Sid

elin

e N

oise

Sup

pres

sion Des

ired tr

end

Projections

1/2-Scale Model data

1/7-Scale Model data

GOAL

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F-15 ACTIVE ACOUSTIC FLIGHT TESTEFFECTS OF FLIGHT SPEED ON JET NOISE

Fully expanded Mach number M j = 1.45 Nozzle exit Mach number M e = 1.73

Upstream OASPLdominated by jetbroadband shocknoise, increases with aircraft Machnumber by factor

5.2)cos1( −− ψfM

Downstream OASPLdominated by jet mixing noise,decreases with aircraft speed by factor 5)( fj VV −

ShockNoise

MixingNoise

angle from inlet ψ°ψ°ψ°ψ°

OA

SP

L at

sou

rce,

dB

Mf = .77

Mf = .61

Mf = .46

Mf = .34

From T. Norum, NASA Langley Research Center

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Higher Bypass Ratio Swept/Leaned StatorsScarf Inlets

Act ive Vanes Installed on the NASA,Glenn Act ive noise Cont rol Fan

Rotor Blade

Stator Vane

Active Noise ControlNoise PredictionChevron Nozzles

Forward-Swept Fans

Highlights From NASA’s Subsonic Research

Documents

Workshop on Jet Exhaust Noise Reduction for Tactical Aircraft - NASA Perspective · · 2013-04-10Workshop on Jet Exhaust Noise Reduction for Tactical Aircraft - NASA Perspective