K. Knowles

The practical possibility of reducing shock-associated noise and controlling mass flow in a supersonic jet is explored. It has previously been shown analytically that introducing swirl into an underexpanded jet can significantly reduce, or even completely eliminate shock-associated noise. It has similarly been shown that swirl can be used to control mass flow with no thrust loss compared with an equivalent variable-area nozzle. A brief review of the evidence for swirl as a noise reduction mechanism shows that the available experimental results are not particularly favourable, but nor are they definitive. The most promising experiments confirm that swirl can reduce supersonic jet noise, but the frequencies and directivities were not practically useful for reducing the EPNL of an SST at flyover. Some new analytical results are presented showing the possibilities of combined noise and mass flow control in supersonic jets. Two important points are emphasised: nozzle performance need not be degraded by the introduction of swirl (specific thrust can be increased with swirl); swirl velocity profile, however, needs to be carefully controlled. It is recommended that specific case studies should be made so that swirl can be considered in concert with variable engine cycles.

DGLR/AIAA 14th Aeroacoustics Conference, 1992

Conference Paper

englisch

21,0 x 29,7 cm, 6 Seiten

DGLR-Bericht, 1992, 1992-03, DGLR/AIAA 14th Aeroacoustics Conference - Proceedings; S.746-751; 1992; Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn

NA

aeroacoustics

Bibliothek

1992