| 摘要 |
<p>1,236,854. Gas turbine engines - sound suppression. GENERAL ELECTRIC CO. July 30, 1969 [Sept.16, 1968], No.38237/69. Headings F1B, F1C, F1G and F1J. The invention relates to means for suppressing noise generated in the compressor of a gas turbine engine in which sound energy emanating from the compressor blades is reflected from the wall of the duct and brought to a focus at a radially inward point of the duct. The means for bringing the sound energy comprises serially disposed circumferential duct surfaces each having different sound reflection characteristics. In the embodiment shown a ducted fan 12 comprising rotor blades 14 and stator blades 16 is mounted within a duct 10 and it is assumed that sound energy emanates from points on the leading edges of the rotor blades 14, the wall of the duct being shaped so as to form surfaces 28, 30 from which the sound energy is reflected and brought to a focus at a point on the surface 36 of the fairing cone, the surface of the cone in this region being formed of sound absorbing material. Similar reflective surfaces 24 may be provided on the duct inner wall downstream of the fan, the sound energy being brought to a focus at a point in the region 38 of the inner casing 22. The inner surface of the duct 10 may be formed of alternate rings 32, 34 of smoothly finished metal such as aluminium or magnesium and of sound absorbing material respectively. In Fig. 3 the surface elements 40 form the focusing means, the elements being of elliptical form. A layer of sound transparent material 42 is provided so as to provide a smooth surface within the duct.</p> |
