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Category :
Languages : en
Pages : 171
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Experimental investigations were conducted of suppression principles, including developing an experimental data base, developing a better understanding of jet noise suppression principles, and formulating empirical methods for the acoustic design of jet noise suppressors. Acoustic scaling has been experimentally demonstrated, and five 'optimum' nozzles have been selected for subsequent anechoic free-jet testing. Several studies were conducted to attempt an optimization of suppressor concepts. Trade studies of performance versus suppression, aircraft integration studies, and development of a figure- of-merit method of analysis all make up the activities in this 'optimization' process. The end product of this effort was to design five nozzles for static and free-jet testing. Demonstration of acoustic scaling for several suppressor configurations was conducted to assure the adequacy of using scale-model results to project full-scale suppression levels. Full-scale data were obtained on several suppressor configurations using J79 and J85 engines. Scale-model data were obtained for these same configurations to allow comparison of scale-model and full-scale results.
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Category :
Languages : en
Pages : 370
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Book Description
Experimental investigations of suppression principles were conducted including developing an experimental data base, developing a better understanding of jet noise suppression principles, and formulating empirical methods for the acoustic design of jet noise suppressors. Acoustic scaling has been experimentally demonstrated, and five 'optimum' nozzles have been selected for subsequent anechoic free-jet testing. This report is organized into four volumes under separate cover: Volume I - Verification of Suppression Principles and Development of Suppression Prediction Methods, Volume II - Parametric Testing and Source Measurements, Volume III - Suppressor Concepts Optimization, and Volume IV - Laser Velocimeter Time-Dependent Cross Correlation Measurements. The experimental studies reported in Volume II involved acquisition of detailed far-field, acoustic data and of aerodynamic jet-flow-field data on several baseline and noise-abatement nozzles. These data were used to validate the theoretical jet noise prediction method of Task 2 and to develop and validate the empirical noise-prediction method presented herein. A series of seven suppressor configurations (ranging from geometrically simple to complex) were tested to establish the relative importance of four jet noise mechanisms (fluid shielding, convective amplification, turbulent mixing, and shock noise). In general, mechanical suppressors exhibit a significant reduction in shock noise relative to a baseline conical nozzle, reduce the effectiveness of fluid shielding (increase rather than suppress noise), reduce the effectiveness of convective amplification (reduce noise), and produce a modest reduction in turbulent mixing noise.
Author: P. R. Knott
Publisher:
ISBN:
Category :
Languages : en
Pages : 155
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Book Description
Experimental investigations were conducted of suppression principles; including developing an experimental data base, developing a better understanding of jet noise suppression principles, and formulating empirical methods for the acoustic design of jet noise suppressors. Acoustic scaling has been experimentally demonstrated, and five 'optimum' nozzles have been selected for subsequent anechoic free-jet testing. In-jet/in-jet and in-jet/far-field exhaust noise diagnostic measurements were conducted using a Laser Velocimeter (LV). Measurements were performed on a conical nozzle and a coannular plug nozzle. Two-point, space/time measurements using a two-LV system were completed for the conical nozzle. Measurements of mean velocity, turbulent velocity, eddy convection speed, and turbulent length scale were made for a subsonic ambient jet and for a sonic heated jet. For the coannular plug nozzle, a similar series of two-point, laser-correlation measurements were performed. In addition, cross correlations between the laser axial component of turbulence and a far-field acoustic microphone were performed. This volume is part of the four volume set that constitutes the Task 3 final report. The other volumes are: Volume I-Verification of Suppression Principles and Development of Suppression Prediction Methods, Volume II-Parametric Testing and Source Measurements, Volume III-Suppressor Concepts Optimization. (Author).
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ISBN:
Category : Computer programming
Languages : en
Pages : 198
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Category : Pollution
Languages : en
Pages : 656
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Category : Science
Languages : en
Pages : 1226
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Category :
Languages : en
Pages : 942
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Category :
Languages : en
Pages : 28
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ISBN:
Category : Aeronautics
Languages : en
Pages : 1368
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Author:
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ISBN:
Category : Jet planes
Languages : en
Pages : 536
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