GB1449186A - Vortex air cleaner-acoustic attenuator assembly - Google Patents

Abstract

1449186 Vortex air cleaner PALL CORP 11 Dec 1973 [18 Dec 1972] 57422/73 Heading B2P [Also in Division Fl] An air cleaner-acoustic attenuator assembly for connection to the air intake of a gas turbine engine comprises an array of vortex air cleaners 10 and an array of spaced soundabsorbing sheets 40, 40a, 40b defining passages 44 arranged to receive clean air from adjacent air cleaners and deflect such air at least once from the surface of the sheets. The air cleaners 10 are mounted between plates 12 and 13 of a housing 11 which is airtightly connected to the acoustic attenuator housing 16 through rubber seals 17 and bolts 18. Each air cleaner comprises a tube 23 made of asbestos or glass-filled polypropylene, a helical vortex generating member 29 made of filled polypropylene and resin-bonded in the inlet end of the tube and an outlet tube 27 for clean air which defines with the tube 23 an annular space 30 for the discharge of dirt particles into the interior of the housing 11 which is connected via a duct to a scavenging blower or injector. The sheets 40, 40a, 40b of the acoustic attenuator, in cross-section, may be dog-legged, as shown, curved (e.g. sinussoidal), zig-zag or straight (in this case they are set at an angle to the axis of the vortex air cleaners). The sheets may be made of, or surfaced with, sound-absorbing material. They may be of metal or plastics. As shown, each sheet is a sandwich of two metal plates 41, which may be perforated or in mesh form, with soundabsorbing material 43, e.g. non-woven glass fibre mat, therebetween. The sandwich may also be surfaced with sound-absorbing fabric and may be enclosed in a thin plastics membrane for moisture-proofness. The attenuator housing 16 is secured by rivets 64 to one side of the duct 5 at the air intake of the gas turbine engine. A similar cleaner-attenuator assembly is secured to the other side of the duct, Figs. 1 and 2 (not shown). In operation, clean air emerging from the outlet tubes 27 of the vortex air cleaners enters the passages 44 between the sheets 40, 40a, 40b, is deflected twice upon the dog-legs 44a, 44b and is guided by baffles 8, 8a in the duct 5 towards the engine intake. Sound pressure waves propagate from the engine intake and are deflected in turn by the baffles 8, 8a and upon the dog-legs 44b, 44a and pass through the air cleaners. Sound attenuation of the order of 10%, 70% and 20% is obtained by the baffles, dog-legs and cleaners respectively.