1、NASA Contractor Report 18“185“1Evaluation of Analysis Techniques for LowFrequency Interior Noise and Vibrationof Commercial AircraftA. E. Landmann, H. F. Tillema, and S. E. MarshallBoeing Commercial AirplanesRO. Box 3707Seattle, Washington 9812.4-2207Contract NASI-18027October 1989N/ .SANational Aer
2、onautics andSpace AdministrationLangley Research CenterHampton, Virginia 23665-5225(NASA-CF_-I61_,I) LVALUATION OF ANALYSISTECHNI(_UES FOR. LOW FRF_ULNCY INTEQIOR NnlStANO VI_RATIqN uF C_MMERCIAL AIRCRAFT(hoeing Commercial Airplane Co.) -/3 pCSCL 20A c3/rlNgO-I ko66uncl as0234097Provided by IHSNot f
3、or ResaleNo reproduction or networking permitted without license from IHS-,-,-H8U9ddU|HU|iiH|Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-i Af“_-“ “,1 FOREWORDmmLmmiwLu- 1|mK_mmThis report contains comparisons of predicted and measured vibration a
4、nd interior noise levels for anaircraft, with aft mounted propeller engines. Based on these comparisons, recommendations are madefor modeling and analysis techniques for evaluation of low-frequency engine noise and vibration in thepassenger cabin. This work was conducted under NASA contract NAS1-180
5、27 from January, 1987through February, 1989. Work was managed by the Acoustics Division at the NASA Langley ResearchCenter. During 1987 work, Mr. H. Morgan was the chief of the Acoustics Division and Mr. D. G. Ste-phens was the technical monitor for the contract. During the 1988 and early 1989 work,
6、 Mr. D. G. Ste-phens was chief of the Acoustics Division at NASA and Dr. K. Shepherd was the technical monitor forthe contract.All analytical work was performed under the direction of the Noise Research staff of the Boeing Com-mercial Airplanes. A number of engineering organizations and subcontracto
7、rs contributed to thesuccessful completion of the project as planned. Key contractor personnel responsible for this effortwereNoise Technolo_,L. M. ButzelL. W. CraigC. G. HocJgeA. E. LandmannS. E. MarshallG. K. OueitzschP. M. SeratiSlructures Technolo_K. H. DickensonR. L. DreisbachR. R. EnsmingerM.
8、T. HutchinsonH. J. JamshidiatE. E. MeyerH. E TillemaPropulsion Technolotw.M. A. HeidariR. L. MartinJ. L. WhiteT. E YantisWeights Technolo_D. E. CookD. J. RobertsSubcontractorsA. C. Aubert - Cambridge Collaborative, Inc.J. E. Manning - Cambridge Collaborative, Inc.L. D. PopemProvided by IHSNot for Re
9、saleNo reproduction or networking permitted without license from IHS-,-,-.Lwwimi|Hii-imdImiil !mE _iJiiR i|mRelmamIi !|n m|iProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-mMuTABLE OF CONTENTSFOREWORD . iTABLE OF CONTENTS iiiLIST OF TABLES . vLIST OF
10、 FIGURES vii1.0 SUMMARY . 12.0 INTRODUCTION . 3iWL-3.04.0APPROACH 53.1 Noise and Vibration Tests . 53.2 Analysis Model Development 73.2.1 Finite Element Model . 83.2.2 Statistical Energy Analysis Model . 93.2.3 PAIN Model . 13RESULTS4.14.24.34.44.54.64.74.84.94.104.114.12oo . o,oo ,o,ooo,ooo,oooo,oo
11、o,ooo.ooo,o ,. o. oooo 15Finite Element Analysis Results CFY 1987) . 15Finite Element Model Improvements (FY 1988) . 20Finite Element Analysis Results (FY 1988) . 22Statistical Energy Analysis Results (FY 1987) . 33Review of SEA Procedures for Low-Frequency Problems 384.5.1 Acoustic Space Modal Dens
12、ity Estimate 384.5.2 Structure Modal Density Estimates 394.5.3 Use of Finite Element Models to Verify SEA Parameters . 39SEAM TM Code Improvements 41SEA Low-Frequency Model Improvements . 434.7.1 Input Power Estimate . 434.7.2 Modal Density Estimates . 444.7.3 Strut Connection Modeling 444.7.4 Strut
13、 Loss Factor 46Midfrequency Model Improvements . 47Statistical Energy Analysis Results (FY 1988) . 49PAIN Analysis Resuts (FY 1987) 55PAIN Analysis Results (FY 1988) 57PAIN Improvements and Feasibility Studies . 62,o111PRECEDING PAGE BLANK NOT FILMEDProvided by IHSNot for ResaleNo reproduction or ne
14、tworking permitted without license from IHS-,-,-5.0eag_CONCLUSIONS AND RECOMMENDATIONS . 655.1 Finite Element Analysis . 655.2 Statistical Energy Analysis 665.3 PAIN Analysis . 66m=JZzIII|mmiII!Ei1!m,BIWIIImmtllw=IR _;l!n el -Illivwl, |w |!-=iProvided by IHSNot for ResaleNo reproduction or networkin
15、g permitted without license from IHS-,-,-LLmE JRITableLIST OF TABLESr_ag_727 Demonstrator Airplane Ground Vibration Test (GVT) Shake Conditions . 5727 Demonstrator Airplane Flight Conditions . 7Modeling Time and Cost Comparison for 727 Demonstrator Airplane FiniteElement Models 33LwluFProvided by IH
16、SNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-viwliUiiimnliimlriNI!1mIiilIii|_ JIiiRIillmilm _iEl -“Iil -Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-IwMmw12345678910111213141516171819202122232425LIST OF“ FIGU
17、RESEa_Prediction Program Comparisons and Comments . 1727 Demonstrator Airplane-General Arrangement . 6BS 1010 Microphone and Accelerometer Locations 7727 Demonstrator Airplane-Finite Element Model Finite Element Method 8GE36 Demonstrator Engine Finite Element Model . 1025-Element Low-Frequency SEAM
18、TM Model (20- to 100-Hz Range) 11100-Element Midfrequency SEAM TM Model (100-to 400-Hz Range) 12Propeller Aircraft Interior Noise Model . 14727 Demonstrator Airplane Predicted Versus Measured Frame ModeShape at BS 1010-21.5 Hz 15727 Demonstrator Airplane GVT-Roving Microphone Data 16727 Demonstrator
19、 Airplane GVT Accelerometer Data Frame VersusCeiling Panel Response at Stringer 4 17Finite Element Prediction Versus 727/GE36 Demonstrator Test;GVT-Front Mount Vertical Shake . 18Finite Element Prediction Versus 727/GE36 Demonstrator Test;GVT-A.ft Lower Mount Lateral Shake . 20Original and Revised C
20、eiling Panel Weight Distribution . 21Original and Revised Hat Rack Weight Distribution 21Acoustic Mesh Typical Cross Section . 23727 Demonstrator Airplane-Reduced Finite Element Models . 24Finite Element Prediction Versus 727/GE36 Demonstrator Test;Ground Vibration Test-Front Mount Vertical Shake .
21、25Longitudinal Variations Around BS 1010-GE Side Window SeatMicrophone Prediction 26Finite Element Prediction Versus 727/GE36 Demonstrator Test;Ground Vibration Test-Aft Lower Mount Lateral Shake . 27Finite Element Predictions Versus 727/GE36 Demonstrator Test;Ground Vibration Test-Front Mount Verti
22、cal Shake . 28Finite Element Predictions Versus 727/GE36 Demonstrator Test;Ground Vibration Test-Aft Lower Mount Fore-Aft Shake 29Finite Element Predictions Versus 727/GE36 Demonstrator Test;Ground Vibration Test-Aft Lower Mount Vertical Shake . 30Finite Element Predictions Versus 727/GE36 Demonstra
23、tor Test;Ground Vibration Test-Aft Lower Mount Lateral Shake . 32SEA2kfr,_ Predicted Levels Versus 727 Demonstrator Test Data:GVT-Forward Mount Lateral Shake . 34PRECEDING PAGEviiBLANK NOT FILMEDProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Ii2Je,2
24、62728293O313233343536373839404142434445464748495OLae, Low-Frequency SEAM TM Model Predicted Levels Versus 727 DemonstratorTest Data; GVT-Forward Mount Vertical Shake . 35Midfrequency SEAM TM Model Predicted Levels Versus 727 DemonstratorTest Data; GVT-Forward Mount Vertical Shake . 37Asymptotic Moda
25、l Densities for the Low-Frequency SEA Model . 40Input Power Comparisons 42Response Predictions for the Low-Frequency Baseline ModelUsing Measured Input Power-Vertical Shake 43Composite Strut Modal Density Based on Spacing Between Peaksin the Measured Vertical Shake Input Power . 45Instantaneous Moda
26、l Density for the Cabin Acoustic Space 46Comparison of Modal Density Prediction Procedures-InteriorAcoustic Space 47Midfrequency SEAM Model Variable Panel Density . 48Response Predictions for the Low-Frequency Improved Model-Vertical Shake 50Response Predictions for the Low-Frequency Improved ModelU
27、sing Measured Input Power Vertical Shake . 51Response Predictions for the Low-Frequency Improved Model-Fore-Aft Shake 52Response Predictions for the Low-Frequency Improved ModelUsing Measured Input Power Fore-Aft Shake . 53Response Predictions, Midfrequency Model Side-of-Body Shake,Improved Model 54
28、Measured Minus Predicted SPL Using Impioved Midfrequency Model 55Power Flow Diagram for Elements of PAINUDF Model . 56Measured Versus PAINUDF Predicted Levels 57Average of Seat Measurements Versus PAINUDF Space Average Prediction . 58Propeller Wavefronts for Blade Downsweep (Forward Rotor) and Blade
29、Upsweep (Aft Rotor) at _ = 105 59Propeller Wavefronts for Blade Downsweep (Forward Rotor) and BladeUpsweep (Aft Rotor) at O _ 800 59Measured and PAINUDF Predicted Levels for Open Panel andConical Empennage Models . 60Measured and PAINUDF Predicted Levels Phase Sensitivity Study . 60Comparison of Pro
30、peller Field Phase Contours ANOPP Phase VersusDummy Phase . ., -,. , . . . 61Measured and PAINUDF Predicted Levels PAINUDF SensitivityStudy to Excitation Models (Mach - 0.80 at 35 000 ft) 62Example of Sidewall Layer Configurations . 63B,IVlllMmfMmJnNlj i=_-.am- i!i|. , =!BmI IBProvided by IHSNot for
31、 ResaleNo reproduction or networking permitted without license from IHS-,-,-1.0 SUMMARYL_=t_JNThis document summarizes a 2-year effort to evaluate the application of selected analysis techniques tolow-frequency cabin noise associated with advanced propeller engine installations. Work was funded bya
32、NASA contract, NAS1-18027.Three design analysis techniques were chosen for evaluation including finite element analysis, statisticalenergy analysis (SEA), and a power flow method using elements of SEA (computer program PropellerAircraft Interior Noise (PAIN). An overview of the three procedures is p
33、rovided in figure 1. Data fromtests of a 727 airplane (modified to accept a propeller engine) were used to compare with predictions.Comparisons of predicted and measured levels at the end of the first years effort showed reasonableagreement leading to the conclusion that each technique had value for
34、 propeller engine noise predictionson large commercial transports. However, variations in agreement were large enough to remain cautiousand led to recommendations for further work with each technique. This recommended work was accom-plished in the second years effort.Assessment of the second years r
35、esults leads to the conclusion that the selected techniques can accu-rately predict trends and can be useful to a designer, but that absolute level predictions remain unreli-able due to complexity of the aircraft structure and low modal densities. The extremely complex natureof the modified 727 demo
36、nstrator airplane may be largely responsible for this conclusion. It would beworthwhile to apply these techniques to more conventional aircraft structure cases.= _,l=wLmFrequency range(this study)CalculationsAdvantagesDisadvantagesUseFEMRotorModes, display, SPLversus position andfrequencyGood detail
37、 versusfrequency, positionExpensive, hardto change modelDetailed predictionsdesign work forexi_ng or newairplanesSEAMLow-frequency model High-frequency modelRotor and rotor Rotor harmonics and BPFharmonics ( 100 Hz)Power, modal densities coupling lossfactors, space average display and SPLInexpensive
38、/quick modelchanges/power flow analysis/variance estimatesLack of spatial details/highestimate vadance for low modaldensity casesPower flow analysis for existingairplanesPreliminary designPAINBPFPower structural modesspace average SPLModerate expGood trim definitionlack of spatial details,excitation
39、 fieldcomplexityPreliminan/designFigure 1. Prediction Program Comparisons and CommentsUgO 196RI-4wProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-iiNimM(In !imuIgUiugniiiJiProvided by IHSNot for ResaleNo reproduction or networking permitted without l
40、icense from IHS-,-,-Lu= =rmmm-SmZ-L_z2.0 INTRODUCTIONThe primary sources of cabin noise on advanced propeller-powered aircraft are low- to mid-frequency(i.e., below 500 Hz) structure borne noise (caused by engine unbalances) and engine-radiated propellertones. Conventional sound proofing treatments,
41、 such as damping tapes or fiberglass blankets, are notvery effective in this frequency range. Also, most low- to mid-frequency design tools tend to be based onidealized cylindrical models of the aircraft fuselage, which ignore effects of tapered empennage sections,pressure bulkheads, floors, etc. Ef
42、fective reduction of low- to mid-frequency noise requires the develop-ment of improved design analysis tools. These improved tools will lead to a better understanding of themechanisms involved and provide guidance for developing new suppression concepts.The objective of the FY 1987 task under contra
43、ct NAS 1-18027 was to evaluate the ability of three analysistechniques (contained in existing computer programs) to predict cabin noise and vibration. Specificsteps of this effort were as follows:1. Predict cabin noise, together with vibration levels of the floor, cabin sidewall, pressure bulkhead,e
44、mpennage, and strut at rotor (once per revolution) and propeller-blade-passage frequencies. Compare predicted levels with measured levels from a 727 demonstrator aircraft modified to accepta GE36 counter-rotating propeller engine. Make predictions and comparisons for ground vibrationtest and infligh
45、t conditions.3. Determine strengths and shortcomings of prediction program procedures and/or modeling tech-niques and identify potential means for improvements.The objectives of the FY 1988 task were to incorporate recommended improvements, repredict noiseand vibration levels, compare the new predic
46、tions to measured levels, assess results, and make recom-mendations for future use of these procedures.L_=kt =PRECEDING PAGE BLANK NOT FILMEDProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-4mIUmmmBlmmglJimEBJIm!nBmmIimm|Rii|Provided by IHSNot for Res
47、aleNo reproduction or networking permitted without license from IHS-,-,-|:=:_k :=IBww3.0 APPROACHWhile the NASA contract focused on predictions and comparisons with test data, preliminary workincluding 727 test descriptions and analysis model development is also included in this report.3.1 NOISE AND
48、 VIBRATION TESTSNoise and vibration testing on a 727 aircraft, modified for installation of a GE36 counter-rotating pro-peller engine, provided the database with which to compare predictions. During ground vibration tests,before engine installation, the strut was excited by a shaker to determine airframe and cabin response toengine mount vibration. Response to shaker inputs at each engine mount location was re
