Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16J—PISTONS; CYLINDERS; SEALINGS
  • F16J15/00—Sealings
  • F16J15/16—Sealings between relatively-moving surfaces
  • F16J15/32—Sealings between relatively-moving surfaces with elastic sealings, e.g. O-rings
  • F16J15/3284—Sealings between relatively-moving surfaces with elastic sealings, e.g. O-rings characterised by their structure; Selection of materials
  • F16J15/3288—Filamentary structures, e.g. brush seals

Definitions

• Embodiments of the invention relate to brush seals for sealing a gap between a high pressure and a low pressure area.
• brush seals for sealing gaps, such as those found in gas turbine engines, is known in the art.
• brush seals are often utilized to minimize leakage of fluids at circumferential gaps, such as between a machine housing and a rotor, around a rotary shaft of the engine, and between two spaces having different fluid pressure within the engine.
• the fluid pressure within the system which may be either liquid or gas, is greater than the discharge pressure (the pressure outside the area of the engine housing, toward which the fluid will tend to leak), thus creating a pressure differential in the system.
• the system pressure side of the brush seal is referred to as the high pressure side
• the discharge pressure side of the brush seal is referred to as the low pressure side.
• Conventional brush seals include a bristle pack which is traditionally flexible and includes a plurality of bristles for sealing the gap, the bristles having a free end for contacting one component, such as the rotor.
• Circular brush seals have been utilized in gas turbine engine applications to minimize leakage and increase engine fuel efficiency.
• Conventional brush seals are made from metallic fibers, which are typically cobalt or nickel-base high temperature superalloy wire products suitable for elevated temperature operation. Because brush seals are contacting seals where bristle tips establish sealing contacts against the rotor surface, their applications are generally limited to surface speeds of less than about 1200 ft/sec and temperatures below about 1500 0 F and usually below about 1200-1300 0 F. At extremely high surface speeds and temperatures, metallic brush seals have been found to suffer from excessive wear resulting from bristle tip melting. There are many areas in existing gas turbine
• balance piston and other secondary flow areas near the gas path where surface speed and temperature conditions are typically beyond the capabilities of conventional metallic brush seals.
• these locations are generally sealed by large-gap labyrinth seals which have been found to have high levels of leakage during use as compared to contacting seals such as carbon seals and metallic brush seals.
• Rotating intershaft seals for both co-rotating and counter-rotating shafts, for example in advanced military aircraft engines, are also generally labyrinth type seals.
• Metallic brush seals are also traditionally not used for sealing buffer air near the bearing cavity. Buffer air is used to seal the bearing lubricant by pressurizing the buffer air higher than that of bearing lubricating oil pressure. Metallic brush seals are not used because of metallic debris could reach the interface between the bearing elements (e.g., balls, pins, etc.) and races causing bearing and rotor damage and possibly failure. Again, current seals used at these locations are generally high- leakage labyrinth seals. Higher leakage for bearing oil seals is not desirable because of contamination of downstream components and cabin air that can be introduced through the leak path. Appropriate carbon seals have not yet been developed for such applications because of their fragile characteristics and low damage tolerance.
• a contacting brush seal including a plurality of fibers fabricated from non-metallic materials, the fibers being twisted or braided together substantially along their length (L).
• the fibers may be particularly made from ceramic or polymeric materials, and in one embodiment are more particularly fabricated from NOMEX®, a synthetic aromatic polyamide polymer, manufactured by DuPont for high temperature applications.
• NOMEX® a synthetic aromatic polyamide polymer, manufactured by DuPont for high temperature applications.
• the non-metallic ceramic brush seals disclosed herein have melting points much higher than those of nickel and cobalt base superalloys and, therefore, should prevent the tips from melting under most conditions.
• brush seals made from softer high strength polymeric fibers with moderate (about 500-700 0 F) temperature capability may also be used for high performance bearings such as counter-rotating bearing cavities of advanced gas turbine engines.
• a brush seal includes a plurality of metallic bristles and a support member that mechanically captures the plurality of metallic bristles, hi one arrangement, the support member includes a pair of relatively rigid front and back plates and a pair of relatively flexible front and back plates, the plurality of metallic bristles, such as formed as a flexible bristle pack, being disposed between the front and back plates.
• the support member provides a level of rigidity to the flexible fiber pack, hi one arrangement, the support member is configured to hold the flexible fiber pack in an axially inclined position such that the flexible fiber pack is coned either toward a low pressure area or a high pressure area in a brush seal system.
• a brush seal in one arrangement, includes a plurality of metallic bristles having a bristle length and a support member constructed and arranged to support the plurality of metallic bristles.
• the support member includes at least one flexible plate extending at least substantially along the bristle length of the plurality of bristles.
• a brush seal system includes a contact rotor and a Attorney Docket No. : 1039-012 Express Mail Label No.: EV 967 019 635 US
• the brush seal system also includes a brush seal disposed between the contact rotor and the rotatable shaft to divide the pathway into a high pressure side and a low pressure side.
• the brush seal includes a plurality of metallic bristles having a bristle length and a support member constructed and arranged to support the plurality of metallic bristles.
• the support member has at least one flexible plate extending at least substantially along the bristle length of the plurality of bristles.
• a brush seal in one arrangement, includes a plurality of brush seal members having a brush seal member length and a support member constructed and arranged to support the plurality of brush seal members.
• the support member includes at least one flexible plate extending at least substantially along the brush seal member length of the plurality of brush seal members.
• the plurality of brush seal members is configured as a brush seal pack.
• the support member is constructed and arranged to mount to a base and to orient the brush seal pack in an axially inclined position relative to the base.
• Figure 1 is a perspective view of a mechanically captured brush seal.
• Figure 2 is schematic illustration of a brush seal design including a flexible front and back plate.
• Figure 3 is a schematic illustration of the flexible front and back plates of Figure 2 including radial slots.
• Figure 4 is a photograph of twisted NOMEX® brand fibers such as used for the brush seal of Figure 2.
• Figure 5 illustrates a configuration of a support member of Figure 2 having a single flexible plate.
• Figure 6 illustrates a configuration of a support member of Figure 2 positioning a fiber pack toward a high pressure area.
• Figure 7 illustrates a configuration of a support member of Figure 6 having a single flexible plate.
• a brush seal 10 including a brush strip or pack 17 having a plurality of brush seal members 12 supported around a rod or core 14.
• the plurality of brush seal members 12 can be formed of a ceramic or polymeric material (e.g., non-metallic fibers) to form a fiber pack.
• the plurality of brush seal members 12 can also be formed of a metallic material (e.g., metallic bristles) to form a bristle pack.
• the brush seal members 12 are mechanically captured and secured as part of the brush strip 17.
• the brush seal members 12 may be folded or wound about the core 14 as shown schematically in Figure 1.
• a clamping channel 13 such as the conventional channel or U-ring, may be utilized to further secure the brush seal members 12 to the core wire 14 by crimping the channel 13 over the wound brush seal members 12.
• the brush seal members 12 may be glued or cemented to the rod 14 in the mechanically captured condition, as desired.
• the metallic bristles can be welded to the core 14 to form the brush seal.
• the ceramic or polymeric fibers are preferably twisted or braided, as illustrated in Figure 4, into thicker diameter filaments about 0.02"-0.05" in diameter.
• Brush seals 10 can be fabricated from these braided filaments as described below.
• Ceramic fibers may be made from suitable high temperature ceramic filaments, including, but not limited to: Aluminum Oxide/Silicon Oxide/Boron Oxide or NextelTM fiber (3M, St. Paul, MN); Silicon carbide fiber; other ceramic fibers generally made for ceramic/metal or ceramic/ceramic composites.
• Polymeric fibers may be made from suitable high temperature polymeric materials, including, but not limited to: KEVLAR® brand filaments for extremely high strength; and NOMEX®
• KEVLAR® and NOMEX® are synthetic aromatic polyamide polymer manufactured by DuPont. Other suitable polymeric materials may be utilized for the twisted or braided filaments for brush seals 10, as would be known to those of skill in the art.
• NOMEX® can be selected for brush seal fabrication because the NOMEX® fibers are generally made into strong fabrics for applications where thermal and flame resistant properties are essential.
• NOMEX® is the high temperature version of KEVLAR® which is as strong as or stronger than high strength steel.
• NOMEX® Other general properties include: 1.) usable in wide range of temperatures from -196°C to over 300 0 C; 2.) broad compatibility with industrially used oils, resins, adhesives and refrigerants; 3.) chemical resistance to acids, alkalis and solvents; 4.) non-toxic; 5.) self-extinguishing; 6.) does not support combustion; and 7.) does not drip or melt when heated or burned.
• NextelTM can be selected for brush seal fabrication.
• NextelTM fibers are very thin, in the range of about 25 ⁇ m to 0.001" in diameter, and have a low modulus of elasticity.
• the fibers are twisted as shown in Figure 4 to fabricate the brush strips.
• the twisted NextelTM fibers are much thicker than the individual fibers, the twisted fibers having a thickness in the range of about 900 ⁇ m to 0.036" in diameter and they are rigid enough to make brush strips using the conventional automatic brush strip manufacturing process.
• the brush member pack 17 is inclined axially, such as in the direction of the fluid flow(e.g., toward a low pressure (Lp) side within an engine).
• the brush seal 10 can be attached to a stator housing or to a rotating shaft 24 at a first end and can contact a rotor 26 at a second to form an intershaft seal configuration.
• the flexible brush member pack 17 is held in an axially inclined position by a support member 19 having a pair of thinner front and back plates 30, 32 which are attached to more rigid front and back plates 34, 36 as shown in Figure 2.
• the support member 19 is configured to provide some rigidity to the brush seal members 12 of the brush member pack 17.
• the flexible plates 30, 32 help to control axial and radial displacements of the brush seal members 12 by supporting the brush member pack 17 against pressure and centrifugal forces within a brush seal system (e.g., engine).
• the front plate 30 may be fabricated from a thin metallic strip which is configured to contact the brush member pack 17 when the brush seal system builds up pressure. Thus, the front plate 30 acts as a flow deflector minimizing brush seal members blow- down on a rotating surface, such as the rotor 26, causing excessive brush member wear.
• the flexible back plate 32 may also be made from a metallic sheet stock. However, the thickness of the flexible back plate 32 may be greater than the front plate thickness 30. The relatively thicker back plate 32 is designed to support the brush member pack 17 under pressure.
• the flexible front and back plates 30, 32 may also be divided into segments 21 by radial slots 20 as shown in Figure 3, thereby allowing the segments 21 to bend.
• the displacement of the brush member pack 17 caused by differential pressure and centrifugal forces at various operating conditions in a brush seal system can be controlled.
• the brush member pack 17 is allowed to bend axially as the differential pressure and centrifugal force within the brush seal system increase with the rotor speed.
• clearance between the ID of the brush seal 10 and an outer diameter (OD) of the rotor 26 or its interference can be maintained relatively constant throughout the engine operating cycle (e.g., after engine excursion).
• the flexible plates 30, 32 can extend a predetermined length 38 of the brush seal members 12 so as to expose only a brush seal members tip area 22, and protect the brush seal members 12 from being damaged during installation and/or mishandling.
• the brush seal 10 may be attached to the rotating shaft 24 at a first end can contact the rotor 26 at a second end with the rotating shaft 24 and the rotor 26 configured to rotate in relatively opposing directions.
• the stresses in the brush seal members 12 resulting from the centrifugal force are minimized as the brush member pack 17 is supported by flexible metallic back plate segment 21.
• the metallic segments 21 are designed to withstand the maximum bending stress due to centrifugal force.
• the term "twisted” as used herein is intended to include braided configurations, or any configuration where the fibers intentionally overlap or are wound about at least a portion of the length of the fibers.
• non-metallic materials other than those described herein may be utilized for the twisted fibers.
• the brush seal 10 can be attached to a rotating shaft 24 (e.g., base) at a first end for an intershaft seal configuration and can contact a rotor 26 at a second end.
• a rotating shaft 24 e.g., base
• the brush seal 10 is attached to a stationary housing and contacts a rotor operable to rotate about an axis of rotation.
• the brush member pack 17 is held in an axially inclined position toward the low pressure side by a support member 19 having a pair of thinner front and back plates 30, 32 and a pair of more rigid front and back plates 34, 36.
• the support member 19 includes a single flexible plate attached thereto.
• brush member pack 17 is held in an axially inclined position toward the low pressure side by a support member 19 having rigid front and back plates 34, 36 and a single flexible back plate 32, such as formed from a metallic sheet stock, disposed in proximity to the low pressure side.
• the back plate 32 is designed to protect the brush seal members 12 from damage during installation and support the brush member pack 17 while under pressure, for example.
• the brush member pack 17 can be held in an axially inclined position toward the low pressure side by a support member 19 having rigid front and back plates 34, 36 and a single flexible front plate 30, such as formed from a metallic sheet stock, disposed in proximity to the high pressure side.
• the flexible front plate 30 provides a restoring force to the brush seal members 12 to return the brush seal members 12 to a given position after a deformation of the brush seal members 12.
• the brush seal pack 17 can be attached to a rotating shaft 24 (e.g., base) at a first end for an intershaft seal ⁇ "f:W i . :!!!:! ' ⁇ PCT/US200
• the brush seal pack 17 is inclined axially (i.e., coned) in the direction of the fluid flow, i.e., toward the low pressure (Lp) side.
• Lp low pressure
• the support member 19 i.e., the rigid front and back plates 34, 36 and the flexible front and back plates 30, 32
• H p high pressure
• the flexible front and back plates 30, 32 bend to close a sealing gap or increase a seal contact pressure with the rotor 26 to reduce leakage.
• the brush seal 10 can act as a contacting seal for low leakage at relatively lower surface speeds.
• Figure 6 illustrates the brush seal pack 17 as being inclined axially (i.e., coned) by the rigid front and back plates 34, 36 and by the flexible front and back plates 30, 32, toward a high pressure (H p ) side.
• the support member 19 includes rigid front and back plates 34, 36 and a single flexible plate attached thereto.
• the brush seal pack 17 is held in an axially inclined position by rigid front and back plates 34, 36 as well as by a flexible front plate 30, such as formed from a metallic sheet stock.
• the front plate 30 is designed to contact the brush seal pack 17 when the system builds up pressure.
• the front plate 16a can act as a flow deflector minimizing brush seal memeber blow-down on the rotating surface causing excessive brush seal member wear.
• the front plate 30 can provide a restoring force to return the brush seal pack 17 into a sealing configuration after rotor excursion.
• the brush member pack 17 can be held in an axially inclined position toward the high pressure side by a support member 19 having rigid front and back plates 34, 36 and a single flexible back plate 32, such as formed from a metallic sheet stock, disposed in proximity to the low pressure side.
• the brush seal members 12 can be formed from a metallic material which are mechanically captured by the support member 19 and supported r - " 1 If ' ,,"!,,,,!,,;,, PCT/US200i
• the bristles can be formed from a nickel and cobalt based superalloy. In such an arrangement, the metallic bristles can be used in applications requiring surface speeds of less than about 1200 ft/sec and temperatures below about 1500 0 F and usually below about 1200- 1300 0 F.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Sealing Devices (AREA)

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• 2007
  • 2007-04-16 WO PCT/US2007/009227 patent/WO2008127244A1/en active Application Filing
  • 2007-04-16 JP JP2010504024A patent/JP2010525254A/ja active Pending
  • 2007-04-16 EP EP07775451A patent/EP2147237A1/de not_active Withdrawn

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