Patent GB-1201096-A (GB)
Title: Air particle separator
IPC: F02M35/08
Filed: 1967-10-20
Abstract: 1,201,096. Centrifugal separators; Air filters, UNITED AIRCRAFT CORP. 20 Oct., 1967 [15 Nov., 1966 (2)], No. 47826/67. Headings B2P and BIT. [Also in Division F1] A separator for removing foreign particles from air entering the inlet of an aircraft, e.g. helicopter, engine comprises a plurality of filter panels joined together to form a passageway for connection to the engine inlet, each panel consisting of spaced walls defining a chamber in which are mounted a number of centrifugal separator tube members communicating with the atmosphere, the chamber and the passageway, the chamber being provided with scavenge means for removing particles separated from the air after its passage through the separator tube members. As shown in Fig. 1, two separators 24, 26 are supported by mounts 28, 30 on an helicopter fuselage 12 in front of engines 20, 22 which may be of the turbine type. Alternatively, a single separator, Fig. 3 (not shown), may be provided for both engines. Each separator, Figs. 2 and 4, consists of a number of filter panels, such as 32, 34, which are joined together to define a central passageway 66 which is in communication with the respective engine inlet. A filter panel may be used at the front of the separator but preferably, as shown in Fig. 2, a by-pass door 36 having a pair of swivelling door members is mounted in an aperture 38 at the front of the separator and is operated by means of cable 160 or 162 Fig. 1, connected to a swivelling door actuating member 131 and to a handle 164 in the pilot's cabin 18 whereby the passage of air to the engine either directly through the aperture 38 and the passageway 66 or via the filter panels and the passageway may be controlled. A presure probe unit 262, Fig. 4, is mounted in passageway 66 and is connected to a presure gauge 265 and a warning light in the pilot's cabin to indicate whether the flow in passageway 66 is normal or is reduced due to filter blockage. Each filter panel comprises outer and inner walls 44, 46, defining between them a chamber 64, Fig. 6, forming part of a scavenge duct 50 and in which are mounted centrifugal separator tube members 42. An outer coarse filter screen member 40 covers the outer wall 44 of each panel. Alternatively, Fig. 18 (not shown), a moulded screen insert is mounted in the inlet of each separator tube. Each tube, Fig. 6, has swirl vanes 72 and communicates with the chamber 64 through an annular passage 74 for the discharge of dirty air containing separated particles and with the central passageway 66 through a hollow member 70 for the discharge of clean air. The scavenge duct 50 is connected through ducting 56 to blowers 52, 54 which may be operated by electric motors or, as shown in Fig. 1, by compressed air bled from the engine 20 and fed through line 270, pilot-operated solenoid valve 272 and lines 274, 276. A pressure indicator which may communicate a signal to the cockpit is mounted in the duct 50. The separator includes or is attached rearwardly to a member 114 which is sealingly mounted in the engine inlet 112 by means of a plastics seal member allowing axial or circumferential relative motion between the separator and the engine inlet. In another arrangement, Fig. 5 (not shown), an inflatable seal is provided between the inlet 112 and the member 114, inflation or deflation of the seal being controlled by the pilot for blocking or allowing air flow through the space betwen the inlet and the member. In the separator of Fig. 3 (not shown) the by-pass door is constituted by a single member hinged about a pivot arm actuated from a pilot-operated motor through rack and pinion. In another modification, Fig. 15 (not shown), the by-pass door is of the venetian-blind type. In Fig. 11, the separator has outer and inner cylindrical walls defining between them a single chamber 64 which constitutes the scavenge duct communicating with the blower 52. A screen member 40 surrounds the tube separators which are canted to the separator axis and through which the air is directed by means of cowl flaps 172 pivotably actuated by the pilot through a manually operated lever or through a motor. A by-pass door 203 having overlappable sections 205, 207 is actuated through gearing 199 by a pilot-operated motor 211. Hot-air de-icing of the centrifugal separator tubes is provided by directing air through a duct 190 which communicates with the chamber 64 and in which is mounted an auxiliary blower 55 and a heater 200. The latter may be eliminated if the duct 190 is connected to the compressor section of the engine 20. In a modification, Fig. 9 (not shown), the deicing equipment is dispensed with and a different type of pivotable single member door is provided. In Fig. 14, the separator 24 is movable with respect to the inlet of engine 20 by means of a pilot-operated hydraulic cylinder-piston mechanism 204, pivotable link members 210, 212 being connected between the separator and the fuselage 12. A pivotable by-pass door is shown at 60. In the position shown, with by-pass door 60 closed, during flight the air enters the engine through the gap 202 travelling in a circuitous path with right angle turns whereby large particles, such as ice particles, get separated from the air before it enters the engine inlet. In the position wherein the separator is sealingly engaged with the engine inlet by means of a seal ring 200 and the door 60 is open ram air enters the passageway 66 and hence the engine inlet directly and no de-icing takes place. In another embodiment, Figs. 16 and 17 not shown, the separator is of D-shaped crosssection made up of a number of jointed arcuate double-walled panels. The cross-sectional area of the filter increases from the inlet to a certain point along its length and then decreases towards the outlet. In Fig. 21, a separator for use with an annular engine inlet 112 has, in addition to the outer and inner walls 44, 46, a third wall 312 defining with the wall 46 the ram-air passageway 66, the inlet opening of which is controlled by an annular by-pass door 340 mounted on bracket members 342 and actuable by fluid power cylinders 344. A fourth wall 314 defines a cooling air passageway 330 whereby ram air during forward motion of the aircraft is directed over engine or aircraft accessories 320 in a cooling chamber 322 and then released to atmosphere through an outlet 324. When the aircraft is stationary cooling air is drawn in by a blower 326. In a further embodiment, Figs. 22-24 (not shown), a separator axially adjustable with respect to the engine inlet is dome-shaped being made up of a number of sealably joined, arcuate segments. In a still further embodiment Fig. 26 (not shown), two filter panels acting as a by-pass door are pivotably mounted in the passageway 66 so as to form in the blocking position a V-shaped dam across the passageway. An ice deflector is removably positioned in front of the separator inlet. In other modifications of the separator, Figs. 27-29 (not shown), a by-pass aperture is fabricated into a side panel of the separator and may be controlled by (a) an axially slidable door; (b) a door made up of upwardly and downward pivotable door members; or (c) a single-member pivotable door opening towards the inlet of the separator. Further modifications including pivotable side or top panels to provide by-pass apertures for the air and pivotable separator back wall members are described.