GB868963A - Improvements in or relating to exhaust gas stream silencers for use with gas turbineengines - Google Patents

Abstract

868,963. Exhaust silencers. BRISTOL SIDDELEY ENGINES Ltd. June 19, 1957 [June 21, 1956], No. 19312/56. Class 7(2). The exhaust from an aircraft gas turbine engine is silenced on the ground by a unit comprising a frusto-conical convergent member 22 of steel plate having preferably nozzleshaped perforations 33 and surrounded by a diffuser 24 of steel plate mounted on a wheeled carriage (not shown), the inlet area of the member 22 being adjustable as by a restrictor plate 23a which may itself have an adjustable central aperture or may have a fixed central aperture in which case the plate 23a is replaceable by a plate of different aperture and may have a bell-mouth extension on its upstream side. The member 22 and plate 23a may as shown replace the nozzle of an engine jet pipe 12, when the effective discharge area of the member 22 is equal to the nozzle discharge area, or the nozzle may be retained, when the member 23a surrounds it with a clearance for air entrainment and the member 22 has an effective discharge area equal to at least one and a half times the sum of the nozzle discharge area and the clearance area, the member 22 being secured to the member 24 at its upstream end by bolted-up flanges. The effective discharge area of the member 22 may be selected by using a suitably apertured throttle plate 28, or one of variable aperture or an axially displaceable exhaust bullet. A perforated extension 29 and cap 30 of total effective discharge area equal to that of the unrestricted downstream end of the member 22 may be used, or the end may be entirely blanked off. The members 22, 29 and, according to the Provisional Specification, 24 may be made in sections to allow variation of their lengths. Water may be sprayed on to the member 22. The silencer unit may be used in a test house in series between an engine and an air-entraining diffuser of a further silencer. The Provisional Specification describes two embodiments not having a plate 23a, in one of which there is no wheeled carriage and both the members 22, 24 are bolted to the pipe 12, the perforations 33 being plain holes.