1、NASA / CR-1999-209002Advanced Turbofan Duct Liner ConceptsGerald W. Bielak and John W. PremoBoeing Commercial Airplane Group, Seattle, WashingtonAlan S. HershHersh Acoustical Engineering, Inc., Westlake Village, CaliforniaNational Aeronautics andSpace AdministrationLangley Research CenterHampton, Vi
2、rginia 23681-2199Prepared for Langley Research Centerunder Contract NAS1-20090February 1999Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-The use of trademarks or names of manufacturers in the report is for accurate reporting and does not constitute
3、 anIofficial endorsement, either expressed or implied, of such products or manufacturers by the National AeronauticsI and Space Administration.Available from:NASA Center for AeroSpace Information (CASI)7121 Standard DriveHanover, MD 21076-1320(301) 621-0390National Technical Information Service (NTI
4、S)5285 Port Royal RoadSpringfield, VA 22161-2171(703) 605-6000Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Table Of ContentsLIST OF FIGURESLIST OF TABLES1.0 Summary2.0 Introduction2.1 Technical Approach2.2 Report Organization3.0 Passive Acoustic L
5、iners3.1 Acoustic Liner Characteristics3.2 Summary Of Preliminary NASA/FAA ContractInvestigating Broadband Liner Concepts3.3 Passive Liner Tests.3.3.1 Grazing Flow ImpedanceMeasurement Technique3.3.2 Grazing Flow ImpedanceMeasurements For Passive ElementLiners3.3.3 Bulk Absorber Materials Study3.3.4
6、 Linear Liners4.0 Adaptive Liners4.1 Introduction4.2 Bias Flow Adaptive Liner Designs4.3 High Temperature Adaptive Liner Design5.0 ADP Model Fan Acoustic Liner Design5.1 Aft Liner Depth ConstraintsPageVoVlll155688810111213153.3.4.1 Slot Linear Liners 163.3.4.2 Micro-perforate LinearLiners 1619191920
7、21215.2 Target ADP 22“ Fan Rig Hardwall Fan Noise Spectra 225.2.1 ADP Demo Hardwalled Aft FanSpectra 235.2.2 22“ ADP Fan Rig HardwalledSpectra 235.3 Liner Design Points for the Aft Fan 24Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-5.4 SourceNoise
8、ModalEnergyAssumptions 245.5 OptimumLiner Impedancesfor theAft Fan 255.6DesignMethodologiesfot theAft Duct 265.6.1OptimizeLining ParameterstoMatchAdmittance 265.6.2OptimizePNLTAttenuations(bothsidesthesame) 285.6.3OptimizePNLTAttenuations(allowtwo sidesto bedifferent) 285.6.4CalculatetheCross-Perfor
9、mance 285.7PredictedLiner Attenuationsfor theAFT Fan 285.8Conclusions 296.0Evaluationof BroadbandLinersfor aMid-SizedTwinEngineAirplane 316.1ProgramOverview 316.1.1Airplane/EngineDefinition 316.1.1.1AirplaneDefinition 316.1.1.2EngineDefinition 326.1.1.3NaelleDefinition-Inlet 326.1.1.4NacelleDefiniti
10、on-Aft Duct 326.1.2TargetSpectra 326.1.2.1Inlet Noise 326.1.2.2AftFanNoise 336.1.3Typesof NacelleNoiseSuppressionTechnologies 336.1.4Linings Evaluatedin theStudy 346.2 Inlet TradeStudies 346.2.1TechnologiesEvaluated 356.2.2Liner DepthConstraints 356.2.3SourceAssumptions 356.2.4 Optimum Liner Impedan
11、ces 356.2.5 Evaluation Process 366.2.5.1 Optimize LiningParameters to MatchAdmittance 36Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-6.2.5.2 Run Rdiff Code toDetermine LiningAttenuations 366.2.5.3 Add Attenuations toHardwall Data 376.2.5.4 Extrapo
12、late Dats toFAR 36 Condition 376.2.6 Trade Study Results 376.2.6.1 Impedance TradeStudy 376.2.6.2 Lining Area andConfiguration TradeStudy6.2.7 Conclusions6.3 Aft Duct Trade Studies6.3.1 Technologies Evaluated6.3.2 Liner Depth Constraints6.3.3 Source Modal Energy Assumptions6.3.4 Optimum Liner Impeda
13、nces6.3.5 Evaluation Process6.3.5.1 Optimize LiningParameters to MatchAdmittance 446.3.5.2 Optimize PNLTAttenuations Using theYMATCH startingpoints 456.3.5.3 Choose Best LiningBased on PNLTAttenuations 456.3.5.4 Calculate the Off-Design Perfromance 466.3.6 Trade Study Results 466.3.6.1 Approach Desi
14、gn PointImpedance Study 466.3.6.2 Cutback Design PointImpedance Study 466.3.6.3 Off-Design PointStudy 473940414243434344.111Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-7.0 References6.3.7 Conclusions 4749AppendicesA1. “Theory And Design Of Helmho
15、ltz Resonators Constructed WithSlot Perforates“ Allen Hersh and Bruce Walker111A2. “Theory And Design Of Helmholtz Resonators To SuppressAircraft Engine Noise“ Allen Hersh and Bruce WalkerA3. “Theory And Design Of Helmholtz Resonators ConstructedWith Micro-Diameter Perforates“ Allen Hersh, Joseph W.
16、 Celanoand Bruce WalkerA4. Impedance Models.ivProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Fig. No.2.3.45.6.7.8.9.10.11.12.13.14.15.16.17.18.19.20.21.22.23.24.25.List of FiguresFig. Title PageSingle Layer Acoustic Liners 50Double M=0.0, 0.33, and
17、0.50 64Measured And Predicted Impedances Compared To TargetImpedance, M=0.33 65Measured vs. Predicted Surface Impedance - Fiberglass Bulk Absorber 66Measured Surface and Characteristic Impedance 67Measured vs. Predicted Characteristic Impedance 68Measured vs. Predicted Attenuation Constant 69Measure
18、d vs. Predicted Phase Speed Ratio 70Effect Of Orifice Number, Grazing Flow Speed and SPL onResonator Tuned Resistance 71Effect Of Orifice Number and Grazing Flow Speed on ResonatorFace-Sheet Mass Reactance: SPL=135 dB 72Comparison Of Effect Of Grazing Flow AND SPL Changes OnAcoustic Resistance Of Cu
19、rrently Used Perforates With Micro-Perforate 73Comparison Of Acoustic Mass Reactance For Currently UsedPerforates With Micro-Perforate 74VProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-26.27.28.2930313233343536373839404142434445.46474849505152535455
20、565758Adaptive Liner Test DesignsBias Flow Impedance Changes For Test LinerComparison Of Predicted Impedance Spectra For The Bias Flow TestLiner With The Original and Updated Bias Flow Impedance Models.High Temperature Liner Impedance and AttenuationCartoon of Lining SegmentsComparison of the Design
21、 ADP Hardwalled Data PredictionsHardwall Target Spectra Based On ADP Demo DataComparison of Hardwalled 22“ ADP DataHardwall Target Spectra Based On ADP Model Fan DataRepresentation of the Fan Duct with the MELO ProgramOptimum Lining Impedance for the ADP Fan DuctPreliminary Ideal Impedance Calculati
22、ons for the ADP Fan DuctIdeal Impedance Calculations for the ADP Fan DuctComparison of Boundary Layer Effect on Optimum ImpedancesBlock Diagram of the Design ProcessMELO Predicted Lining Attenuations vs the Optimum AttenuationsPredicted Lining Impedance vs the Optimum Impedance (1 layer)Predicted Li
23、ning Impedance vs the Optimum Impedance (2 layer)Conventional and Scarf InletsMELO Representation of the Fan Duct NacelleInlet Spectra for the Approach, Cutback and Sideline ConditionsAft Duct Spectra for the Approach, Cutback and Sideline ConditionsExamples of Linings Considered in the Trade StudyB
24、lock Diagram of the Evaluation Process for the InletResults of the Impedance Study for the Inlet ComponentImpedance of the Inlet Liners (at the approach condition)Ray Acoustic Argument for Low Inlet AttenuationsImpedance of the Inlet Liners (at the cutback condition)Comparison of Lining Area Technol
25、ogiesConventional and Scarf Inlet NacellesInlet Lining Area and Configuration StudyMELO Predicted Ideal ImpedancesBlock Diagram of the Evaluation Process for the Aft Duct75767778798081828384858687888990919293949596979899100101102103104105106107viProvided by IHSNot for ResaleNo reproduction or networ
26、king permitted without license from IHS-,-,-596061Comparisonof Aftfan PNLTAttenuationsat Approach 108Comparisonof Aftfan PNLTAttenuationsatCutback 109Comparisonof Aftfan PNLTAttenuations(summedapproachandcutbackcondition) 110viiProvided by IHSNot for ResaleNo reproduction or networking permitted wit
27、hout license from IHS-,-,-TableNo.3.456789.10.11.12.13.14.15.16.17.18.List of TablesTable TitleBulk Absorber Acoustic Materials Candidates Identified ByBoeing Materials TechnologyFluid Renention Properties Of Bulk Absorber Material CandidatesSummary Of Micro-Diameter Resonator GeometryPreliminary 22
28、“ Fan Rig Lining Depth ConstraintsDefinition of the ADP Demo Aft LinerFrequency Weightings Used for YMATCH by Band NumberSingle Layer/Single Layer Final DesignsDouble Layer/Double Layer Final DesignsFAR 36 Operating Conditions for Trade Study AirplaneYMATCH Frequency Weightings for the InletResults
29、of the Impedance Study for the Inlet ComponentResults of the Lining Area and Configuration Study for theInlet ComponentFrequency Weightings Used for the Narrow Chord Fan at ApproachFrequency Weightings Used for the Narrow Chord Fan at CutbackFrequency Weightings Used for the Wide Chord Fan at Approa
30、chFrequency Weightings Used for the Wide Chord Fan at CutbackResults of the Impedance Study for the Aft Component at ApproachResults of the Impedance Study for the Aft Component at CutbackPage121316202226272731353639434343444546viiiProvided by IHSNot for ResaleNo reproduction or networking permitted
31、 without license from IHS-,-,-1. SummaryThe Advanced Subsonic Technology (AST) Noise Reduction Program goal is to reduce aircraftnoise by 10 EPNdB by the year 2000, relative to 1992 technology. Interim goals have beenestablished which include a goal to validate concepts to improve nacelle duct treat
32、menteffectiveness by 25% relative to 1992 technology by the second quarter of fiscal year 1997. TheAdvanced Turbofan Duct Liner Concepts Task (Task 1 NAS-20090) work by Boeing wassupporting this goal. The duration of this contract was February 1994 to September 1996.The technical approach was to inv
33、estigate methods for increasing the attenuation bandwidth ofnacelle acoustic linings. The primary motivation for this approach is the character of the fannoise spectrum generated by modem wide chord fan engines. The wide chord fans haveapproximately 50% fewer blades and run at slightly reduced tip s
34、peeds compared to oldernarrow chord fans. As a result, the fan blade passing harmonic frequencies are significantlylower than for narrow chord fans. For example, blade passing frequency (BPF) at landing forthe engines powering the Boeing 777 airplane is in the 630 to 800 Hz I/3 octave band range.The
35、 broadband fan noise spectrum however is very similar for the narrow and wide chord fanswith the peak Noy weighted levels in the 3 kHz to 4 kHz region. Therefore, for effective PNLTattenuation, approximately 3 octave bandwidth lining attenuation is required for wide chordfans in order to attenuate t
36、he peak NOY region of the spectrum and reduce the tone correctionresulting from the BPF.The basis for the technical approach was a Boeing study conducted in 1993-94 underNASA/FAA contract NAS 1-19349, Task 6 investigating broadband acoustic liner concepts. Asa result of this work, it was recommended
37、 that linear double layer, linear and perforate triplelayer, parallel element, and bulk absorber liners be further investigated to improve nacelleattenuations. NASA Langley also suggested that “adaptive“ liner concepts, which would allow“in-situ“ acoustic impedance control, be considered. As a resul
38、t, bias flow and high temperatureliner concepts were added to the investigation. The following summarizes the specific studiesconducted for Taskl NAS-20090:1. Passive Acoustic Liners. This study investigated liner designs withincreased degrees-of-freedom such as double layer, triple layer andparalle
39、l element liners; liners with linear resistance elements such as thecurrently used woven wire as well as new concepts such as slots andmicro-perforates; and bulk absorber materials such as fiberglass, kevlarfelts and ceramic foam. Subcontracts were given to Hersh AcousticalEngineering (HAE) to study
40、 the linear liner concepts of narrow slots andmicro-perforates.Analysis of the grazing flow impedance test data gathered to verify theimpedance models used for the analytical study of the passive andadaptive liners was not complete at the time this contract concluded.However, passive liner concepts,
41、 which included triple layer and parallelelement liners designed for fan duct application, were tested andpreliminary data analysis was completed. This data indicated that theliners may be slightly better than predicted, but there was sufficient scatterin the data that its accuracy, particularly at
42、grazing flow Mach numbersgreater than 0.3, is questionable.Boeing does not use woven wire resistance elements in the nacelles itProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-buildsbecauseof a numberof concernsassociatedwith manufacturingandin-servi
43、cedurability. However,theabovestudiesshowedimportantpotentialacousticbenefitsfrom useof linearmaterials.Theslotconceptproposedby HershAcousticalEngineeringshowedgoodacousticproperties,butit wasconcludedthatslotshadstrengthandmanufacturingefficiencydifficultieswhichwouldresultin veryheavyliners. Ther
44、efore,theirdevelopmentwasterminatedin favorof micro-perforates.Initialacoustictestingwith micro-perforateswith holesizesdownto .004in.laserdrilled into .040in. thick titaniumplateshowedacousticcharacteristicsvery similarto currentlyusedwovenwire. As aresult,furtherwork with micro-perforatelinersis p
45、lannedfor follow onwork.Althoughanumberof bulk absorbermaterialswerefoundwith goodacousticcharacteristics,nonewereconsideredusablein aircraftenginesbecausefluid absorptiontestingshoweda strongtendencyto absorbhydrocarbonssuchasjet fuel andhydraulicfluid. Furtherbulk absorberinvestigationsweretherefo
46、reterminated.2. Adaptive Acoustic Liners. Two concepts were chosen for investigation.The first was a bias flow concept which uses a steady bias flow (blowingor suction) through the liner to modify the acoustic properties of the liner.The second concept involved increasing the temperature of the line
47、r tomodify its acoustic properties. The design application investigated forbias flow was to design a non-linear liner for the high engine powercondition (high local SPL) and use bias flow to maintain the desiredacoustic resistance at low engine powers (low local SPL). Althoughgrazing flow impedance
48、tests were completed the data analysis has notbeen completed for the adaptive liner concepts.3. ADP Model Fan Acoustic Liner Design. This was the first of twoairplane nacelle design studies conducted. It was a joint study to designand build acoustic liners for testing on the NASA Lewis 22 inchAdvanced Ducted Propeller (ADP) model scale fan. The airplaneapplication was assumed to be a Boeing 747 derivative powered by ADPengines. The scale factor assumed was 5.91. Boeing had responsibilityfor design of the fan duct liners, PW had responsibility for designing theinlet l
