1、NASACONTRACTOR REPORT INVESTIGATION OF DC-8 NACELLE MODIFICATIONS TO REDUCE FAN-COMPRESSOR NOISE IN AIRPORT COMMUNITIES Part I1 - Design Studies and Duct-Lining Investigations by Alun H. Marsh, R. L. Fruscu, D. K. Gordon, C. A. Henry, G. L. Luurie, dnd L. T. Kurnei Prepared by MCDONNELL DOUGLAS CORP
2、ORATION Long Beach, Calif. 70801 for Langley Research Center NATIONAL AERONAUTICS AND SPACE ADMINISTRATION WASHINGTON, D. C. DECEMBER 1970 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-!H I NASA CR-1706 I. Report No. I 4. Title and Subtitle I 2. Go
3、vernment Accession No. I. Investigation of DC-8 Nacelle Modifications to Reduce Fan-Compressor Noise in Airport Communities. Part 11 - Design Studies and Duct-Lining Investigations 7. Author(s) Alan H. Marsh, R. L. Frasca, D. K. Gordon, C. A. Henry, G. L. Laurie, L and L. T. Kamei 9. Performing Orga
4、nization Name and Address Douglas Aircraft Company McDonnell Douglas Corporation Long Beach, California 90801 12. Sponsoring Agency Name and Address National Aeronautics and Space Administration Langley Research Center Hampton, Virginia 23365 3. Recipients Catalog No. I December 1970 5. Report Date
5、- 6. Performing Organization Code 8. Perfornling Organization Report No. IO. Work Unit No. Contract or Grant No. NAS 1-7 I30 13. Type of Report and Period Covered Contractor Report for Period May 1967 to October I969 14. Sponsoring .Agency Code 1 “ 15. Supplementary Notes Distribution of this report
6、 is provided in the interest of information exchange. Responsibility for tllc contents resides in the authors or organization that prepared it. - 16. Abstract . “ Designs for two Pdn-exhaust ducts and eight inlet ducts applicable to the JT3D turboran engines on DC-8-50/61 airplane?, were studied. Th
7、e designs were evaluated in terms of (I) their estimated ability to product. a 7 to 10 PNdB reduction in perceivcd noise level during landing approach and (2) their estimated impact on direct opcrating costs. Two inlet-duct designs and one fan-exhaust-duct design were selected for ground static tcst
8、ing. One of the inlet dcsigns incorporated acoustically absorptive linings on the walls of a revised inlet duct. two concentric ring vanes. and a Icngthcncd centerbody. The other design had treatment on the walls of a lengthened inlet duct. one concentric rmg vane, and an enlarged lightbulb-shaped c
9、enterbody. The fansxhaust duct design provided acoustical linings in an exhaust duct 24 inches longcr than the. existing ducts, thus requiring a new fan thrust reverser but prcscrving the existing primary thrut rcvcrscr. Acoustical duct-lining studies consisted of flow resistance; :Icoustic absorpti
10、on and impedance: duct.tr;lnnlition-los; ad sonic-fatigue tests. Structural duct-lining studies consisted of: determination of slructtlral dcign criteria for duct linings; structural tests of bondcd honeycomb sandwich structures; and development of fabrication procedures for duct linings. Thc result
11、 of these :Icoustical and structural studies wac. the selection of the matcrialc and fabrication proccsc ucd in constructing the test mticles for the ground static tests. 17. Key Words Suggested by Author(s) hlcDonnell Douglas DC-8-50/61 airplancs JT3D turbofan engines Acoustically treated engine na
12、celles Flyover noise reduction Acoustically absorptive duct linings 18. Dislribution Statement “ Unclassificd - Unlimitcd 19. Security Classification (of this report) 20. Security Classification (of Illis page)/ 21. Unclassified Unclassified * For sale by the National Technical Information Service,
13、Springfield, Virginia 22151 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-.- “.I “. I “.-.,“- Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-. . .- . CONTENTS Page . SUMMARY . 1 INTRODUCTION 2 SYMB
14、OLS . 3 NACELLE MODIFICATION DESIGN STUDIES 4 Existing Nacelles 4 Design Goals . 5 Preliminary Considerations 6 Treated Area Requirements 7 Fan-Exhaust Ducts . 8 Inlet Ducts 11 Variable-Area Primary-Exhaust Nozzle 13 Flow Resistance 15 Acoustic Absorption and Impedance 18 Duct Transmission-Loss Test
15、s . 20 Sonic Fatigue . 31 Design Criteria . 37 Adhesive-Bonding Technique . 40 Structural Tests 41 Application of Results of Mechanical Property Tests . 46 Repair Methods 47 CONCLUSIONS . 47 REFERENCES . 51 APPENDIX A 55 APPENDIX B 57 APPENDIX C 59 APPENDIX D 63 DUCT-LINING ACOUSTICAL INVESTIGATIONS
16、 . 14 DUCT-LINING STRUCTURAL INVESTIGATIONS . 37 iii Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-INVESTIGATION OF DC-8 NACELLE MODIFICATIONS TO REDUCE FANCOMPRESSOR NOISE IN AIRPORT COMMUNITIES PART I1 -DESIGN STUDIES AND DUCT-LINING INVESTIGATIO
17、NS By Alan H. Marsh, R. L. Frasca, D. K. Gordon, C. A. Henry, G. L. Laurie, and L. T. Kamei SUMMARY In May 1967, the NASA initiated a program with the McDonnell Douglas Corporation to investigate turbofan-engine nacelle modifications designed to reduce fan-compressor noise from the JT3D engines on D
18、C-8-50/61 aircraft. The program was directed at the definition of nacelle modifications that could reduce the landing-approach flyover perceived noise level by 7 to 10 PNdB with no increase in takeoff noise level. The program was conducted in five phases: (1) nacelle design studies and duct lining i
19、nvestigations, (2) ground static tests of noise-suppressor configurations, (3) flyover noise and cruise performance tests, (4) studies of the economic implications of retrofit, and (5) an evaluation of human response to the flyover noise of the modified nacelles. This document reports the results of
20、 the investigations of the first phase and the resultant selection of the articles tested in the succeeding ground static test phase of the program. Eight inlet-duct and the two fan-exhaust-duct designs were studied and evaluated. Two inlet-duct designs and one fan-exhaust-duct design were selected
21、for ground static testing. One of the selected inlet designs incorporated acoustically absorptive linings on the walls of a revised inlet duct, two concentric ring vanes, and a lengthened centerbody. The other design had treatment on the walls of a lengthened inlet duct, one concentric ring vane, an
22、d an enlarged lightbulb-shaped centerbody. The selected fan-exhaust duct design provided acoustical linings in an exhaust duct 24 inches longer than the existing ducts, thus requiring a new fan thrust reverser but preserving the existing primary thrust reverser. An alternate nacelle modification des
23、ign using a variable-area primary nozzle to reduce the rotational speed of the fan stages during landing was also studied and recommended for ground static testing. The duct-lining investigations included acoustical and structural studies. The acoustical studies consisted of: flow resistance; acoust
24、ic absorption and impedance; duct transmission-loss; and sonic-fatigue tests. The structural studies consisted of: determination of structural design criteria for duct linings; structural tests of bonded honeycomb sandwich structures; and development of fabrication procedures for duct linings. The r
25、esult of these acoustical and structural studies was the selection of the materials and fabrication processes used in constructing the test articles for the ground static tests. n Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-INTRODUCTION The total
26、 human annoyance from operations of commercial jet transports has increased simultaneously with the growth of the air transportation industry and the number of people living in communities around airports. This increased annoyance has stimulated efforts to find means to alleviate the problem through
27、 reducing the level of the noise radiated from the aircraft, modifying aircraft operational procedures, and achieving compatible usage of the land around airports. The alleviation efforts have been conducted as part of a coordinated industry-government research program. In 1965, the NASA extended it
28、s research programs to supplement those of industry in the development of practical nacelle modification concepts for reducing fancompressor noise (ref. 1 ). In May 1967, the Langley Research Center of the NASA contracted with the McDonnell Douglas Corporation and The Boeing Company to investigate n
29、acelle modifications for operational McDonnell Douglas and Boeing transports powered by four Pratt and Whitney Aircraft*(P Part 11, a report of the nacelle modification design studies and duct lining investigations (presented in this document); Part 111, a report of ground static tests of suppressor
30、 configurations (ref. 9); Part IVY a flight investigation of the acoustical and performance effects of the selected design of modified nacelles on a DC-8-55 airplane (ref. 10); Part V, a study of the economic implications of retrofit of the selected design (ref. 11); and Part VI, an evaluation of hu
31、man response to the flyover noise of the modified nacelles (ref. 12). This Part I1 of the report consists of three major sections: nacelle modification design studies, duct-lining acoustical investigations, and duct-lining structural investigations. The first section presents the goals and constrain
32、ts of the program, discusses the preliminary considerations and the 2 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,- c. requirements for treated area, and shows the development of the designs for fan-exhaust ducts, inlet ducts, and a variable-area
33、primary exhaust nozzle. The second and third sections present the results of the acoustical and structural studies conducted to select the duct-lining design and the fabrication processes used in constructing the static-test inlet and fanexhaust ducts. Flexural-fatigue tests of samples of fibermetal
34、 sheets were conducted at the NASAs Langley Research Center. With the permission of the NASA, some of these results are presented in this document as part of the structural investigation of fibermetal surfaces. An s At, Dl D2 DOC h L/W n NLF PNL PNLM R R - Rf Ri SYMBOLS area of noise source taken as
35、 the projected annular area of the fan inlet or fan exit, square feet effective treated surface area, square feet distance in standing-wave tube from face of sample to fust node, centimeters (eq. 7) distance in standing-wave tube between the first and second nodes, centimeters (eq. 7) direct operati
36、ng cost distance between acoustically treated surfaces, feet for duct transmission-loss tests, the ratio of the axial length of treatment, L, to the width of the duct, W number of test locations for measuring flow resistance on a large sheet of porous material (eq. 14 in Appendix A) nonlinearity fac
37、tor, the ratio of the flow resistance at 5.0 meters/second to the flow resistance at 0.2 meters/second instantaneous perceived noise level, perceived noise decibels (PNdB) maximum value of the instantaneous PNL, PNdB resistive part of the acoustic impedance, dyne-second/cubic centimeters (eq. 8) ari
38、thmetic mean flow resistance of a sheet of porous material, cgs rayls (eq. 13 in Appendix A) flow resistance of a sample of porous material, cgs rayls (eq. 2) flow resistance of a sheet of porous material at a test location i, cgs rayls (eq. 13 in Appendix A) S area used in flow resistance tests, sq
39、uare centimeters (eq. 2) 3 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-“ Sb /sa SFC S/N SPL SWR TL U U V X Z a, AP h PC a All ratio of root-mean-square (rms) stress at time of initial failure in test panel b to the corresponding rms stress in tes
40、t panel a (eq. 12) specific fuel consumption, (pounds/hour)/pound ratio, in decibels, of the level of a signal, S, to the level of the background noise, N (eq. 9) sound pressure level, decibels (dB) re 0.0002 dynes/square centimeter standing-wave ratio in a standing-wave tube test (eq. 4) transmissi
41、on loss, decibels volume rate of airflow through a sample of porous material in a flow resistance test, cubic centimeters/second (eq. 2) linear velocity of airflow through a sample of porous material in a flow resistance test, centimeters/second (eq. 3) equivalent rms velocity of a particle of air m
42、oving through the porous surface of a duct lining, meters/second (eq. 1 ) reactive part of the acoustic impedance, dyne-second/cubic centimeters (eq. 8) acoustic impedance, dyne-second/cubic centimeters (eq. 5) normal-incidence acoustic absorption coefficient (eq. 4) differential pressure through a
43、sample of porous material, dynes/square centimeter (eq. 2) wavelength of sound, feet characteristic impedance of air, cgs rayls (eq. 5) standard deviation of the flow resistance measurements R, from the arithmetic mean flow resistance E, cgs rayls (eq. 14 in Appendix A) NACELLE MODIFICATION DESIGN S
44、TUDIES Existing Nacelles DC-8-50/61 airplanes are equipped with the same basic installation of the P the 4 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,- . . ,. diameter of the centerbody is approximately 18 inches. The inlet has a fixed geometry a
45、nd has been designed with a relatively thick internal lip to provide the engine with airflow having high total pressure recovery at all engine operating conditions including takeoff. As a result, there is considerable volume between the inlet duct surface and the exterior nose-cowl surface. This are
46、a was utilized for the installation of engine-oil and pneumatic-system heat exchangers, the inlet-duct ice-protection system, and related piping, valves and ducting. The auxiliary inlet directly beneath the inlet lower lip admits cooling air to the oil and pneumatic-system heat exchangers. Each fan-
47、exhaust duct, figure 1 (b), has an average radial duct cross-dimension of approximately 6.5 inches and a length of 24 inches. Four full-length flow splitters in each duct divide the duct into five separate flow channels. The thrust reverser for the fan exhaust directs the engine airflow through a ca
48、scade to provide reverse thrust at relatively high reversing efficiency. The hot primary engine airflow is exhausted through a nozzle at the rear of the engine. The reverser for the primary exhaust flow is also a cascade reverser similar to the reverser for the fan air. The cascade cover sleeve is t
49、ranslated aft to expose the cascade when the reverser is operated. The noisiness of JT3D-powered aircraft is dominated by the discrete high-frequency tones radiating from the fan-exhaust and inlet ducts and by the lower-frequency broadband noise radiated from the primary jet exhaust. The discrete tones have frequencies equal to the
