GB806385A - Improvements in or relating to the abatement of noise in gaseous currents - Google Patents

Abstract

806,385. Silencing gaseous currents. HIRSCHORN, M. Feb. 7, 1956 April 13, 1955], No. 3826/56. Class 7(2) A method of abating the noise level of gaseous currents comprises the steps of introducing a gaseous stream into a conduit along the central longitudinal axis thereof, alternately inducing portions of the stream to flow in opposite directions substantially perpendicularly away from the axis of the conduit and inducing those portions to flow in opposite directions substantially perpendicularly toward the axis of the conduit, and concurrently expanding the volume of the gaseous stream at selected points along the direction of stream flow. As shown in Fig. 2, the sound attenuation apparatus comprises a casing 24 circular or rectangular in crosssection and inlet and exhaust tubes 26, 27, the casing defining a chamber 28 centrally and axially of which is suspended by members 30 a divider 29 of circular crosssection and provided with a partition 36 of sine-wave form, the latter forming chambers 37, 38; the walls of the divider are perforated with holes 39 which cover about one fourth of the surface area of the divider. Annular chambers 33, 34, subdivided by radial partitions, are located adjacent the tubes 26, 27, the walls 31, 32 of those chambers having openings 41, 42. The apparatus is mounted on wheels 16, Fig. 1, for manouverability at airports and has an intake portion 18 removably connected to the exhaust 19 of a jet aircraft 21, and a vertical exhaust portion 23; diffusers and watercooling are provided for afterburner operation of the aircraft engine. Two or more of the silencing devices may be disposed in series. In a modification, (a) the silencer has three stages 54, 55 and 56, Fig. 6, arranged in series, the chambers 68, 69 and 72, 73 extending across the casing 53 and being subdivided by partitions, and the intake tube 91 being conical in form, the gas exit comprises two openings 96, 97, and (b) a group of silencers are assembled in series and in parallel, Fig. 8, the gaseous stream being apportioned between the silencers 101 in parallel and each part of the stream flowing upwardly through a series of superposed silencers.