Turboshaft engines can be the main source of noise due to a helicopter at takeoff. Some new silencing designs of the inlets and of the ejector were tested on a Turbomeca Arrius 2B2 engine in an open-air static facility. Intake and exhaust are not axisymmetric, and conventional directivity patterns of sound field on a horizontal arc of circle are insufficient. A special microphone array on a vertical half-circle translating axially was built. Data processing has been implemented to plot maps of sound pressure levels in third-octave bands and to compute sound power levels. Intake and exhaust radiations are separated thanks to mufflers on the other side. The lined fins in the secondary lateral inlet well reduce the compressor tone, which is largely dominant in intake radiation. Its sound power level is decreased by 7 dB. The novel ejector is also successful to reduce exhaust broadband noise above 1 kHz with a gain of 5 dB on sound power level. Finally, the benefit on the acoustic emission of the helicopter in flight is appraised.
Three-dimensional sound directivity around a helicopter turboshaft engine
Dreidimensionale Richtcharakteristik des vom Turbomotor eines Hubschraubers erzeugten Schallfeldes
Journal of the American Helicopter Society ; 57 , 4 ; 042002/1-042002/10
2012
10 Seiten, 21 Bilder, 2 Tabellen, 9 Quellen
Aufsatz (Zeitschrift)
Englisch
Three-Dimensional Sound Directivity around a Helicopter Turboshaft Engine 042002
Online Contents | 2012
|HELICOPTER MISSION ANALYSIS FOR A REGENERATIVE TURBOSHAFT ENGINE
British Library Conference Proceedings | 2013
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