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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS2021

A History of Jet Noise Research at the National Aeronautics and Space Administration

This paper reviews jet noise research conducted at the National Aeronautics and Space Administration (NASA) from the early 1950s to the present day. Research conducted by NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA), and early years of NASA focused on turbojet noise, where a common approach for reducing jet noise was to limit the jet exit velocity to speeds that provided acceptable noise levels. Suppressors tested during this time resulted in thrust losses that were too severe to be implemented. With the introduction of turbofan engines in the 1960s, NASA shifted research to programs for both subsonic and supersonic aircraft applications with specific noise reduction goals. Subsonic research focused on increasing the bypass ratio of the engine to reduce the jet exit velocity of the core exhaust and adding mixers to the dual exhaust streams. Advances in computational methods improved aerodynamic designs and jet noise prediction tools. Supersonic applications proved to be more troublesome as programs aimed at large commercial transports required higher specific thrust engines. Changing the engine cycle to reduce jet noise was not compatible with mission range and speed requirements. Research for supersonic commercial aircraft remains an area of interest today at NASA.

Jet Noise↗
NASA NTRS1981

Technology development status at McDonnell Douglas

The significant technology items of the Concorde and the conceptual MCD baseline advanced supersonic transport are compared. The four major improvements are in the areas of range performance, structures (materials), aerodynamics, and in community noise. Presentation charts show aerodynamic efficiency; the reoptimized wing; low scale lift/drag ratio; control systems; structural modeling and analysis; weight and cost comparisons for superplasticity diffusion bonded titanium sandwich structures and for aluminum brazed titanium honeycomb structures; operating cost reduction; suppressor nozzles; noise reduction and range; the bicone inlet; a market summary; environmental issues; high priority items; the titanium wing and fuselage test components; and technology validation.

Rowe, W. T.↗
NASA NTRS1990

Noise measurements from an ejector suppressor nozzle in the NASA Lewis 9- by 15-foot low speed wind tunnel

Acoustic results are presented on nozzle test experiments conducted in the NASA Lewis 9 x 15-ft anechoic wind tunnel on a 'hypermix' nozzle concept, a two-dimensional lobed mixer nozzle followed by a short ejector section designed to promote rapid mixing of the nozzle flow with the flow induced by the ejector. Acoustic and aerodyanmic measurements were carried out to determine the amount of ejector pumping, the degree of mixing, and the noise reduction achieved. Spectra from various nozzle configurations were compared to show the effect of the nozzle geometry on nozzle-alone noise, the benefit of adding an ejector to the mixer nozzles, and the effect of the ejector geometry on ejector/suppressor noise level.

Krejsa, Eugene A.↗
NASA NTRS1965

Sound suppression technology research at Marshall Space Flight Center

This report describes some of the development tests conducted at Marshall Space Flight Center on sound suppressor models. These devices are designed to reduce the sound radiated into the atmosphere from the exhaust jets of large rocket engines. From theoretical considerations, the overall sound reduction capability of the tested models was expected to amount to 40 decibels. However, residual sound, radiated from the rocket engine and its installation, limited the attainable overall suppression to 24 decibels. Suppression of very low sound frequencies remains a special area of endeavor in future investigations. The models were designed to be self-contained. They proved to possess very good operational characteristics.

ROCKET ENGINE NOISE↗
NASA NTRS1974

Flight velocity effects on jet noise of several variations of a 48-tube suppressor installed on a plug nozzle

Because of the relatively high takeoff speeds of supersonic transport aircraft, it is important to know if the flight velocity affects the noise level of suppressor nozzles. To investigate this, a modified F-106B aircraft was used to conduct a series of flyover and static tests on a 48-tube suppressor installed on an uncooled plug nozzle. Comparison of flyover and static spectra indicated that flight velocity had little effect on the noise suppression of the 48-tube suppressor configuration. However, flight velocity adversely affected noise suppression of the 48-tube suppressor with an acoustic shroud and plug installed.

Burley, R. R.↗
NASA NTRS1974

Flight velocity effects on the jet noise of several variations of a 104-tube suppressor nozzle

At the relatively high takeoff speeds of supersonic transport aircraft, an important question concerns whether the flight speed affects the noise of suppressor nozzles. To answer this question, flyover and static tests using a modified F-106B aircraft were conducted on a 104-tube suppressor nozzle. Comparison of adjusted flyover and static spectra indicated that flight velocity had a small adverse effect on the suppression of the 104-tube suppressor. The adverse effect was larger with the acoustic shroud installed than without it.

Burley, R. R.↗
NASA NTRS1977

Summary of forward velocity effects on fan noise

Available experimental data comparing the in-flight and static behavior of fan noise are reviewed. These results are then compared with recent data obtained for a fan stage tested with forward velocity in a low speed wind tunnel. Tentative conclusions are presented about the significance and nature of the changes in noise observed when a forward velocity is imposed. Finally, the implications of the emerging picture of in-flight fan source noise for suppressor design are discussed.

Feiler, C. E.↗