GB865421A - Improvements in or relating to apparatus for attenuating noise vibrations from a gaseous exhaust - Google Patents

Abstract

865,421. Silencing and cooling exhaust. HIRSCHORN, M. Aug. 6, 1957 [Aug. 13, 1956; April 17, 1957], No. 24797/57. Class 7(2). A tube 10, Fig. 4, receiving exhaust from a jet engine nozzle 12 is connected substantially at a point of maximum pressure recovery directly to a silencer 18 not employing sound absorptive material and preferably of the kind described in Specification 806,385. The tube inlet, which may have a throttling plate or nozzle, may be belled and spaced by an air gap from the nozzle 12, or be floatingly connected thereto by a vertically split adapter 26 allowing air entry and having internally fibre-glass 54 lined with perforated sheet steel, soft resilient sealing 48 being provided where the split adapter sections abut each other and the nozzle 12. Water may be injected through hub and blade perforations in a stationary propeller 60, Fig. 6. In Fig. 7, the tube 10 and silencer 18 are mounted in a test house 70 for a jet engine 78. Modifications of the adapter 26 for ground use with aircraft having tail and wing-mounted engines are described. Fig. 13 shows adapter halves 101 pivoted about the rear adapter flange 105, having flattened-off top surfaces to avoid the aircraft tail fins and forming a slot 137 accommodating the aircraft rudder and rearwardly widened to allow rudder movement, whilst brackets 121 for the springs on which the nozzle-engaging adapter portion is hung are engageable by brackets on this portion to limit the amount of "float"; the sealing 133 is of foam rubber covered with asbestos cloth, and the halves 101 are held closed by a crank-operated catch (not shown). Fig. 21 shows an adapter cut away on one side to accommodate an aircraft fuselage and having on the other side partannular air inlets 309 allowing the use of labyrinth sealing 319 between the adapter portions 301, 303; the adapter portion 301 engaging the jet nozzle does so via a resilient seal 302 urged forwardly by coil springs (not shown) in an annular recess 327. In Fig. 16, to simulate flight conditions on the ground, air entry is restricted by a perforated plate 263, whilst a labyrinth seal 257 between the adapter portions 215, 201 has a resilient guard ring 261.