Experimental study of the sound reduction for the side air-intake of a helicopter turboshaft engine
AbstractHelicopters are of considerable interest for short haul flights especially between airports and downtown. However, the high sound levels involved represent one of the main obstacles to the development of this very promising market. The paper deals with the use of a lining for reducing the noise radiated by the inlet of a turboshaft engine at the blade passing frequency of the compressor (8 to 10 Hz). The inlet is perpendicular to the shaft axis. The used liners consists of a solid backplate and a layer of feltmetal material separated by an internal partition in the form of a honeycomb. The efficiency of the acoustic treatment is evaluated in an anechoic room by comparing the total power radiated by full-scale models of the inlet with both reflecting and absorbent walls. It is shown that a 12 dB reduction of the BPF tone can be achieved by using the proposed lining
Copyright on articles is held by the author(s). The corresponding author has the right to grant on behalf of all authors and does grant on behalf of all authors, a worldwide exclusive licence (or non-exclusive license for government employees) to the Publishers and its licensees in perpetuity, in all forms, formats and media (whether known now or created in the future)
i) to publish, reproduce, distribute, display and store the Contribution;
ii) to translate the Contribution into other languages, create adaptations, reprints, include within collections and create summaries, extracts and/or, abstracts of the Contribution;
iii) to exploit all subsidiary rights in the Contribution,
iv) to provide the inclusion of electronic links from the Contribution to third party material where-ever it may be located;
v) to licence any third party to do any or all of the above.