Brush seal with support plate tooth

Abstract

Brush seal arrangement (10), comprising: a sealing surface (48) which is an outer surface of a rotating element (20); a side plate (26); a support plate (28) selectively disposed in a stationary position and having a support tip (60) and at least one support tooth (52) projecting as projections radially inwardly from an outer surface (62) of the support plate (28) toward the sealing surface (48) and axially spaced from one another, the at least one support tooth (52) having a tooth surface (66) and the support tip (60) having a tip surface (68), a tooth pitch (C1) being measured between the tooth surface (66) and the sealing surface (48) and a tip pitch (C2) being measured between the tip surface (68) and the sealing surface (48), the tooth pitch (C1) being smaller than the tip pitch (C2); a plurality of bristles (30) disposed between the side plate (26) and the support plate (28), the plurality of bristles (30) including an end portion (42) for sealing against the sealing surface (48), the support tip (60) directly abutting and providing axial support to the end portion (42) of the plurality of bristles (30); and a biasing element (32) for exerting a biasing force (F) on the support plate (28) in a direction radially inwardly towards the sealing surface (48), wherein the at least one support tooth (52) is adapted to selectively contact the sealing surface (48), wherein the contact between the at least one support tooth (52) and the sealing surface (48) urges the support plate (28) from the stationary position and towards the biasing element (32) and the biasing force (F) opposes movement of the support plate (28) radially outwardly away from the sealing surface (48).

Description

Background of the invention

[0001] The subject of the invention described herein is a brush seal assembly and, in particular, a brush seal assembly having a backing plate including at least one backing tooth for selectively contacting a seal surface.

[0002] Brush seals are commonly found in a variety of applications, such as gas and steam turbines, and are typically used to seal a gap between a rotating shaft and a stationary element. Brush seals have multiple bristles enclosed between a front plate and a backing plate. The brushes extend toward a sealing surface and provide a seal between the rotating shaft and the stationary element.

[0003] The backing plate of the brush seal provides axial support for the bristles and also partially blocks the gap between the rotating shaft and the stationary member. A gap is located between the backing plate and the rotating shaft to essentially prevent contact of the backing plate with the rotating shaft during operation. This gap is sometimes referred to as the backing plate fence height. The backing plate fence height is typically larger than the conventional metal-to-metal gap. To improve the compressive strength of the brush seal and reduce brush wear, the fence height is reduced so that the brushes have increased support and are subjected to less bending stress from the compressive load. However, reducing the fence height can increase the risk of rubbing against the rotating shaft during transient conditions, such aswhen the system experiences resonance speeds or when thermal equilibrium between components is not achieved. If the fence height is insufficient, the support plate facing the rotating shaft may enlarge or become smeared as it rubs against the rotating surface of the rotating shaft during transient conditions.

[0004] When friction occurs on a backing plate, the edges of the backing plate can become irregular and intermittent. This can create a difficult situation, as the bristles cannot easily slide along the backing plate. If the bristles catch on the irregular edge of the backing plate, the brushes will bend and wear where the rotating shaft deflections occur. Thus, the backing plate should provide axial support for the bristles while simultaneously avoiding contact with the rotating shaft.

[0005] There are currently several approaches to reducing or preventing the backing plate surface from coming into contact with the rotating element while still providing axial support for the brushes. For example, in one approach, the backing plate surface is coated with a tribologically compatible coating or backing layer to be more tolerant of friction. Another approach could use a material that allows rubbing between the backing plate and the rotating surface, also essentially eliminating the need to increase the size of the backing plate tip. However, these approaches can add cost and complexity to the brush seal.In another approach, the front plate is adjusted to a relatively narrow gap to serve as a stop element to protect the backing plate. However, this is typically not a feasible option because this approach creates a jet flow that can destabilize the brush seal bristles by causing flutter and relatively rapid wear. Therefore, it would be desirable to provide a cost-effective system for reducing contact between the backing plate of a brush seal and a rotating shaft.

[0006] US 2006 / 0 038 351 A1 describes a brush seal assembly including a sealing surface, a side plate, a backing plate, a plurality of bristles, and a biasing element. The sealing surface is an outer surface of a rotating element. The backing plate has a backing tooth and a backing tip, which protrude radially inward from an outer surface of the backing plate toward the sealing surface and are axially spaced from one another. The backing tip is disposed on the side of the brush seal assembly toward the side plate, axially spaced from the end of the plurality of bristles. The backing tooth is disposed on the side of the brush seal assembly away from the side plate and abuts the end of an adjacent bristle pack.The support tooth has a tooth pitch, measured between its radially inner tooth surface and the sealing surface, that is smaller than the crest pitch, measured between the radially inner crest surface and the sealing surface. The bristles are located between the side plate and the support plate and include an end portion for sealing against the sealing surface. The biasing element is configured to exert an axial biasing force on the side plate to seal an axial end face of the side plate against an end face of a machine housing.

[0007] Further configurations of brush seal assemblies with a sealing surface, a side plate, a support plate and a plurality of bristles are known, for example, from US 2001 / 0 004 145 A1, EP 0 979 963 A2 and US 2004 / 0 007 822 A1. Brief description of the invention

[0008] According to one aspect of the invention, a brush seal assembly is provided that includes a sealing surface, a side plate, a backing plate, a plurality of bristles, and a biasing member. The sealing surface is an outer surface of a rotating member. The backing plate is selectively located in a stationary position and has at least one backing tooth and a backing tip projecting radially inwardly from an outer surface of the backing plate toward the sealing surface and axially spaced from each other. The at least one backing tooth has a tooth surface, and the backing tip has a tip surface. A tooth pitch is measured between the tooth surface and the sealing surface. A tip pitch is measured between the tip surface and the sealing surface. The tooth pitch is less than the tip pitch. The bristles are located between the side plate and the backing plate.The bristles include an end portion for sealing against the seal surface, with the support tip directly abutting the end portion of the plurality of bristles and providing axial support therefor. The biasing member exerts a biasing force on the support plate in a direction radially inward toward the seal surface. The support tooth is configured to selectively contact the seal surface. Contact between the support tooth and the seal surface urges the support plate from the stationary position and toward the biasing member. The biasing force resists movement of the support plate radially outward away from the seal surface.

[0009] These and other advantages and features of the present application will become more apparent from the following description taken in conjunction with the drawings. Brief description of the drawings

[0010] The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: Fig. 1 is an exemplary cross-sectional view of a brush seal assembly; and Fig. 2 a view of a section of the Fig. 1 shown brush seal arrangement.

[0011] The detailed description explains embodiments of the invention together with advantages and features by way of example with reference to the drawings. Detailed description of the invention

[0012] Fig. 1 illustrates an exemplary brush seal assembly 10 located between a rotating member 20 and a machine housing 22. The brush seal assembly 10 can be used in any application requiring sealing between two areas of varying pressure. For example, the brush seal assembly 10 can be used in a gas or steam turbine, a compressor, or a pump. The brush seal assembly 10 includes a side plate 26, a backing plate 28, a plurality of sealing bristles 30, and a biasing member 32. The sealing bristles 30 are received between the side plate 26 and the backing plate 28. The sealing bristles 30 are typically made of a stainless steel alloy, Haynes ® 25, or a nickel / cobalt alloy, although it is understood that other materials can also be used.

[0013] The sealing bristles 30 have a first end portion 40 and a second end portion 42. The first end portion 40 is received between two side rails 44, 46 where a first side rail 44 is attached to the side plate 26 and the second side rail 46 is attached to the support plate 28. The side rails 44, 46 exert a compressive force to secure and position the sealing bristles 30 in place. In one embodiment, the side rails 44, 46 are attached to the sealing bristles 30 by welding. The second end portion 42 of the sealing bristles 30 is configured to provide a seal against a sealing surface 48 of the rotating member 20. In one embodiment, the second end portion 42 of the sealing bristles 30 may contact the sealing surface 48 while the rotating member 20 operates. The sealing bristles 30 may be angled in the direction of rotation. In particular, according to Fig. 2 the sealing bristles 30 are arranged in a direction of rotation R of the rotary element 20.

[0014] According to further reference to Fig. 1, the brush seal assembly 10 includes a substantially annular configuration. In one embodiment, the brush seal assembly 10 may have a segmented structure, wherein the plurality of seal brushes 10 are segmented into discrete sections or segments 50 arranged around the periphery of the brush seal assembly 10. The segments 50 may facilitate assembly of the brush seal assembly 10 between the rotating member 20 and the machine housing 22. The brush seal assembly 10 may include any number of brush seal bristle segments 50, such as four discrete segments, six discrete segments, or eight discrete segments. Both according to Fig. 1 as well as Fig. 2, the biasing element 32 is located in a recess 51 of the machine housing 22 between the brush seal assembly 10 and the machine housing 22. The biasing element 32 is placed between a lower surface 53 of the recess and an upper surface 55 of the support plate 28. Each segmented section 50 of the brush seal assembly 10 can have at least one corresponding biasing element 32. In the illustrated embodiment, the biasing element 32 is a leaf spring, but it should be understood that other types of biasing elements may also be used. For example, in another embodiment, the biasing element 32 could be a wave spring or coil spring.

[0015] According to further reference to Fig. 1, the machine housing 22 includes a hook or shoulder 54, the shoulder 54 being used to engage and provide support to a corresponding portion 56 of the support plate 28. The support plate 28 includes at least one support tooth 52 and a support tip 60. The support tooth 52 and the tip 60 are protrusions each projecting from an outer surface 62 of the support plate 28. The support tip 60 is positioned along the support plate 28 to abut and provide axial support to the sealing bristles 30. The support tooth 52 is disposed closer to the sealing surface 48 of the rotating member 20 than the support tip 60. In particular, the support tooth 52 includes a tooth surface 66, and the support tip 60 includes a tip surface 68.A tooth pitch C1 is measured between the tooth surface 66 and the seal surface 48, and a peak pitch C2 is measured between the peak surface 68 and the seal surface 48. The tooth pitch C1 is smaller than the peak pitch C2. In an exemplary embodiment, the peak pitch C2 ranges from approximately 0.63 mm (0.025 inches) to approximately 3.42 mm (0.135 inches), and the tooth pitch C1 ranges from approximately 0.38 mm (0.015 inches) to approximately 3.05 mm (0.12 inches). That is, the difference between the tooth pitch C1 and the peak pitch C2 ranges from approximately 0.25 mm (0.010 inches) to approximately 0.38 mm (0.015 inches).

[0016] The buttress tooth 52 is configured to selectively contact the sealing surface 48 of the rotating member 20. That is, the buttress tooth 52 is positioned such that when the buttress plate 28 comes into close proximity to the sealing surface 48 of the rotating member 20, only the buttress tooth 52 is configured to contact the sealing surface 48. Thus, contact between the buttress tip 60 and the sealing surface 48 is generally avoided. The buttress tooth 52 of the buttress plate 28 typically contacts the sealing surface 48 during rotating member deflection, which may occur due to thermal transients or rotor vibration when passing through a resonant speed. The functions of the buttress tooth 52 are typically twofold. First, the buttress tooth 52 essentially provides protection for the buttress plate tip 68 in the event of rotor deflection or thermal jamming.The second function of the support tooth 52 is to act as a reserve seal.

[0017] In the Fig. 1, the support plate 28 is selectively located in a stationary position S. The support plate 28 remains in the stationary position S during normal operation until the support tooth 52 contacts the sealing surface 48 of the rotating element 20 during transient thermal operating conditions, such as during startup and shutdown. Contact between the support tooth 52 and the sealing surface 48 causes the support plate 28 to be pushed out of the stationary position S and pushes the support plate 28 in a first direction D1 toward the biasing element 32. In particular, according to the Fig.1 - 2, the contact between the support tooth 52 and the sealing surface 48 causes the segmented portion 50 of the brush seal assembly 10 to be forced out of the stationary position S and radially away from the rotating member 20 so that the support plate tip 60 generally does not rub against the rotating shaft 20.

[0018] The biasing element 32 exerts a preload force F on the support plate 28. The preload force F is directed toward the sealing surface 48 of the rotating element 20. When the support tooth 52 contacts the sealing surface 48 of the rotating element 20, the corresponding segmented portion 50 of the brush seal assembly 10 is urged radially outward and toward the biasing element 32. The biasing element 32 exerts the preload force F on the sealing surface 48 of the rotating element 20, which repositions the segment 50 in the stationary position S.

[0019] The support tooth 52 is used to substantially reduce or eliminate contact between the support tip 60 and the rotor 20, while also reducing the tip clearance C2 between the support tip 60 and the seal surface 48. In particular, the tip clearance C2 of a support plate 28 utilizing the support tooth 52 is generally smaller than the tip clearance C2 of a support plate 28 not utilizing the support tooth 52. The tip clearance C2 should be reduced to the smallest possible dimension to provide axial support to the seal bristles while substantially avoiding contact with the rotating shaft 20 by sacrificing the support tooth 52 in a friction situation. Furthermore, the support tooth 52 can also function as a backup seal.

[0020] Although the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention may be modified to include any number of variations, alterations, substitutions, or equivalent arrangements not previously described, but which remain within the spirit and scope of the invention. In addition, although various embodiments of the invention have been described, it should be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be considered limited by the foregoing description, but is limited only by the scope of the appended claims.

[0021] A brush seal assembly 10 is provided that includes a sealing surface 48, a side plate 26, a support plate 28, a plurality of bristles 30, and a biasing member 32. The support plate 28 is selectively located in a stationary position and has at least one support tooth 52 and a support tip 56. The support tooth 52 has a tooth surface 66, and the support tip 60 has a tip surface 68. A tooth pitch C1 is measured between the tooth surface 66 and the sealing surface 48. A tip pitch C2 is measured between the tip surface 68 and the sealing surface 48. The tooth pitch C1 is less than the tip pitch C2. The bristles 30 are located between the side plate 26 and the support plate 28. The bristles 30 include an end portion 42 for sealing against the sealing surface 48. The biasing element 32 exerts a biasing force F on the support plate 28 in a direction toward the sealing surface 48.The support tooth 52 is configured to selectively contact the sealing surface 48. LIST OF REFERENCE SYMBOLS: 10 Brush seal arrangement 20 Rotation element 22 machine housing 26 Side plate 28 Support plate 30 sealing bristles 32 Preload element 40 first final section 42 second end section 44 first side rail 46 second side rail 48 Sealing surface 50 segments 51 recess 52 supporting tooth 53 lower surface 54 shoulder 55 upper surface 56 corresponding section 60 support tip 62 Exterior surface 66 tooth surface 68 tip surface C1 tooth spacing C2 tip distance F preload force

Claims

[1] Brush seal arrangement (10), comprising: a sealing surface (48) which is an outer surface of a rotating element (20); a side plate (26); a support plate (28) selectively disposed in a stationary position and having a support tip (60) and at least one support tooth (52) projecting as projections radially inwardly from an outer surface (62) of the support plate (28) toward the sealing surface (48) and axially spaced from one another, the at least one support tooth (52) having a tooth surface (66) and the support tip (60) having a tip surface (68), a tooth pitch (C1) being measured between the tooth surface (66) and the sealing surface (48) and a tip pitch (C2) being measured between the tip surface (68) and the sealing surface (48), the tooth pitch (C1) being smaller than the tip pitch (C2); a plurality of bristles (30) disposed between the side plate (26) and the support plate (28), the plurality of bristles (30) including an end portion (42) for sealing against the sealing surface (48), the support tip (60) directly abutting and providing axial support to the end portion (42) of the plurality of bristles (30); and a biasing element (32) for exerting a biasing force (F) on the support plate (28) in a direction radially inwardly towards the sealing surface (48), wherein the at least one support tooth (52) is adapted to selectively contact the sealing surface (48), wherein the contact between the at least one support tooth (52) and the sealing surface (48) urges the support plate (28) from the stationary position and towards the biasing element (32) and the biasing force (F) opposes movement of the support plate (28) radially outwardly away from the sealing surface (48). [2] The brush seal assembly (10) of claim 1, wherein the support tip (60) is positioned along the support plate (28) to provide axial support for the plurality of bristles (30). [3] Brush seal assembly (10) according to any one of the preceding claims, wherein the support tip (60) abuts the plurality of bristles (30). [4] Brush seal assembly (10) according to any one of the preceding claims, wherein the brush seal assembly (10) is substantially annular and includes a segmented structure, wherein the plurality of bristles (30) are segmented into discrete sections around a circumference of the brush seal assembly (10). [5] Brush seal assembly (10) according to any one of the preceding claims, wherein a machine housing (22) is provided for receiving the brush seal assembly (10) and wherein the machine housing (22) includes a shoulder (54) for engagement with a corresponding portion of the support plate (28). [6] Brush seal assembly (10) according to claim 5, wherein the biasing element (32) is arranged in a recess of the machine housing (22). [7] Brush seal arrangement (10) according to one of the preceding claims, wherein the tooth pitch (C1) is in the range of approximately 0.3 mm to approximately 3.0 mm. [8] Brush seal assembly (10) according to any one of the preceding claims, wherein the tip spacing (C2) is in the range of approximately 0.6 mm to approximately 3.4 mm. [9] Brush seal assembly (10) according to any one of the preceding claims, wherein the biasing element (32) is one of a leaf spring, a wave spring and a coil spring.

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