JP2008038898A - Aspirating labyrinth seal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a face seal having low leakage and high durability. <P>SOLUTION: A seal body 48 includes an annular, axially extending portion 72; a radially extending portion 70 defining a primary sealing surface 50, and cooperating with the axially extending portion 72 to define a generally L-shaped cross section; and at least one annular axially-extending seal tooth 88. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates generally to end face seals for rotating machinery, and more particularly to an intake or gas balanced end face seal.

  End face seals are used to minimize leakage from the high pressure region to the low pressure region through the spacing between the two components. Such seals have been used in rotating machines such as steam turbines and gas turbines.

  In gas turbines, end face seals are used between stationary hardware, between rotating elements and stationary elements, and may be used between different rotating elements. The spacing between these different components, i.e. the leakage path, must be sealed, and the seal applied can compensate for variations in spacing due to thermal and mechanical differences in the components that develop during the machine operating cycle. It needs to be possible.

  The variable spacing to be sealed provides a resilient contact maintained between the components, for example using a brush seal or leaf seal, or results in a decrease in pressure loss and thus a flow rate, for example using a labyrinth seal It is generally adjusted by forming a complex leakage path. In the labyrinth seal between the rotating element and the stationary element, the final means of closing the spacing may be adjusted by creating friction of the labyrinth rotating teeth against a soft ("wearable") stationary base. Neither of these seals can meet all performance and durability requirements because of the initial spacing and because of the contact between the adjacent surface and the seal.

As an example, FIG. 1 illustrates a gas turbine engine that includes a rear portion of a compressor 10, a diffuser 12, an annular combustor 14, and a high pressure turbine 16 that includes a rotating nozzle blade 20 carried on a stationary nozzle 18 and a turbine rotor 22. A part of FIG. The compressor 10 is driven by the turbine 16 via the shaft 24. The space between the hot gas primary flow path “F” and the shaft 24 defines a secondary flow path. For various reasons, such as maximizing efficiency and avoiding wear, it is desirable to control leakage from the secondary flow path as much as possible. This is done by including one or more seal assemblies that reduce or block flow therefrom. In the illustrated example, a compressor exhaust pressure (CDP) seal assembly 26 that includes a rotating member 28 having a plurality of radially outwardly extending annular seal teeth 30 located on the opposite side of the wearable fixation member 32 includes a diffuser. 12 is arranged inside. A forward outer seal (FOS) 34 including a rotating member 36 having a plurality of radially outwardly extending annular seal teeth 38 located on the opposite side of the wearable securing member 40 is disposed within the turbine nozzle 18. . End face seals are used elsewhere as well as engines. Both CDP seal assembly 26 and FOS 34 are subject to degradation due to long-term operation as described above.
US Pat. No. 5,284,347 US Pat. No. 5,311,734 US Pat. No. 5,975,537 US Pat. No. 6,045,134 US Pat. No. 6,105,967 US Pat. No. 6,676,369 US Pat. No. 6,719,296 US Pat. No. 6,758,477

  The present invention provides an end face seal that has low leakage and high durability. The spacing between the sealing elements is controlled so that the seal teeth do not rub against the seal rotor. This also provides an efficient seal at the time of engine manufacture and after prolonged use. It is estimated that leakage through the primary seal surface can be reduced by about 25% compared to prior art end face seals.

  According to one aspect, the present invention defines a first annular element defining a first primary seal surface facing generally axially and a second primary seal surface facing generally axially, the first A second annular element mounted in an axially movable relationship with respect to the seal support such that two primary seal surfaces are disposed facing the first primary seal surface, A seal assembly is provided having at least one annular seal tooth from which at least one of the first primary seal surface and the second primary seal surface extends axially therefrom.

  According to another aspect of the invention, a seal body for a seal assembly disposed about an axis defines an annular axially extending portion and a primary seal surface and cooperates with the axially extending portion. A radially extending portion defining a generally L-shaped cross section and at least one annular seal tooth extending axially from the primary seal surface.

  In accordance with another aspect of the invention, a seal assembly disposed about an axis for a gas turbine engine is disposed adjacent to the rotor having a first primary seal surface facing axially. A fixed seal support, an axial direction attached to the seal support, disposed between the rotor and the seal support, axially movable relative to the seal support and opposite the first primary seal surface An annular seal body including a generally radial extension and a generally axial extension defining a second primary seal surface facing the at least one of the first primary seal surface and the second primary seal surface. One has at least one annular seal tooth extending axially therefrom.

  The invention can best be understood by referring to the following description in conjunction with the accompanying drawings.

  Referring to the drawings in which the same reference numerals refer to the same elements in the various figures, FIGS. 2 and 3 illustrate the leakage between the relatively high pressure region P (high) and the relatively low pressure region P (low). An exemplary seal assembly 42 for sealing is shown. In this particular example, the seal assembly 42 replaces the compressor exhaust pressure (CDP) seal as described above and is disposed between the core shaft 24 'and the diffuser casing 12'. It should be understood that it can be used in all applications where end face seals are required. The basic components of the seal assembly 42 can include a rotor 44, a fixed seal support 46, and a seal body 48 (sometimes referred to as a "slider"), all around the longitudinal axis of the engine. Be placed. The rotor 44 is substantially disc-shaped and defines a first primary sealing surface 50 facing in the axial direction.

  The seal support 46 is a non-rotating axially extending element and defines a radially facing secondary seal surface 47. Although it is a continuous 360 degree ring in the illustrated example, it can be configured as a segmented annular structure or an array of individual supports. The rear portion 52 has a radially extending flange 54 that is secured to the diffuser 12 ′ by one or more fasteners 56. Its front portion 58 carries one or more spring seats 60. In this example, there are five spring seats that are equally spaced around the periphery of the seal support 46, but instead the spring seat 60 may be configured as a continuous or segmented annular structure. As best seen in FIG. 3, the spring seat 60 has a generally cylindrical body 62 and an arcuate flange 64 that defines a pair of mounting ears 63 extending in the lateral direction. The spring seat is secured to the seal support 46 by one or more fasteners 65. Cylindrical body 62 includes a radially inwardly extending array rail 66 that is received within a complementary array slot 68 of seal body 48 to provide a desired relative angular alignment of seal support 46 and seal body 48 or Maintain “clocking”. Accordingly, the seal body 48 is carried by the seal support 46, so that it can move in the axial direction but not in the lateral direction.

  The seal body 48 is an annular element that may be continuous or segmented and has a generally L-shaped cross section with a radially extending portion 70 and an axially extending portion 72.

  The plurality of retracting springs 73 are disposed between the spring seat 60 and the radially extending flange 74 of the seal body 48. The rear of each pullback spring 73 is positioned in the spring pocket 76 of the flange 74 or other suitable positioning mechanism. The pull-back spring 73 serves to move the seal body 48 away from the rotor 44. This function is described in more detail below. In the illustrated example, there are five compression coil springs, but springs of different types and numbers may be used.

  A secondary seal 78, for example a known type of piston ring, is disposed in the groove 80 of the flange 74 and seals the axially facing secondary seal surface 47 of the spring support assembly 46. The piston ring may be of a known type that provides a continuous (or nearly continuous) circumferential seal. The purpose of the secondary seal 78 is to prevent leakage from the path between the seal body 48 and the seal support 46, which is affected by the same pressure difference as the primary seal, while moving the seal body 48 in the axial direction. is there. The specific shapes of the sealing element and the mounting structure are not important, and may be changed according to a specific application without affecting the functional aspect of the seal assembly 42.

  As shown in FIGS. 4 and 5, the radially extending portion 70 of the seal body 48 defines an axially facing second primary seal surface 82. The second primary seal surface 82 is disposed close to the rotor 44 and faces the first primary seal surface 50. Circumferential seal teeth 84, commonly referred to as “start seals”, extend axially from the outer end of the radially extending portion 70 to the outside of the rotor 44, and in a particular example are angled radially inward. . The fluid passages 86, 87 are formed through the radially extending portion 70 in a known manner as required for static pressure balance of the seal body 48 during operation (described in more detail below).

  The second primary sealing surface 82 includes a planar inner portion 82A and an outer portion 82B separated by an annular groove 83. The outer portion 82B has a plurality of annularly and radially spaced axial extensions to flow at least one, and optionally, a continuous or serpentine flow path in the radial direction. A seal tooth 88 is included to restrict the flow from the primary flow path to the secondary flow path. In the illustrated example, there are two seal teeth 88A and 88B having a tapered cross-sectional shape separated by an annular round bottom groove 90. The teeth 88 can also protrude from the planar surface if desired. It should also be understood that the seal tooth shape can be reversed, i.e., the seal teeth 88 can instead be formed on the first primary seal surface 50.

  The shape of the second primary seal surface 82 can be defined in part by various characteristics of the seal teeth 88, including the number of seal teeth 88, the axial height "H", the tip height. Spread in / out of an axial direction called width “W”, cross-sectional tip angle “A”, tilt angle “S” (note that this angle is very small in the example shown), radial spacing or pitch “P” , And the radial extent or total length of the entire seal tooth 88 indicated by “L”. Non-limiting examples of these dimensions are as follows: tooth height H is about 0.38 mm (0.015 inch), tooth angle A is about 10 degrees, and slope angle S is about 0 degrees. About 45 degrees, tip width W is about 0.13 mm (0.005 inch) to about 0.76 mm (0.030 inch), and pitch P is about 1.3 mm (0.05 inch) to 3.8 mm ( 0.15 inch). These values may be changed for specific applications.

  In the illustrated example, the first primary sealing surface 50 has a distance “D” that is substantially equal to the axial distance from the inner portion 50A and the tip of the seal teeth 88 of the second primary sealing surface 82 to the inner portion 82A. (See FIG. 2) and an outer portion 50B that is offset forward in the axial direction of the inner portion 50A. With this shape, a “step” to reduce radial flow is defined at the bifurcation point of the inner portion 50A and the outer portion 50B of the first primary seal surface 50, and during operation, the distal portion of the seal teeth 88 is the first primary seal surface. 50 is disposed between the inner portion 50A and the outer portion 50B in the axial direction.

  During operation, the seal body 48 forms a seal that cooperates with the rotor 44. The pull back spring 73 holds the seal body 48 away from the rotor 44 to prevent contact between the two components when the engine is stopped. As the engine operating speed increases, the fluid pressure in the primary and secondary flow region of the engine increases, and the seal assembly 42 receives a rising pressure acting on its axially facing surface accordingly, thereby causing the seal body 48 to It will be moved toward the rotor 44. By selecting the relative surface area of the various portions of the seal body 48, the number and size of the passages 86, 87, and the size of the retract spring 73 in a known manner, the seal assembly 42 is fluidized at selected operating conditions. Static pressure balance is maintained. Thus, the second primary seal surface 82 never contacts the first primary seal surface 50, but a slight axial direction, for example, from about 0.05 mm (0.002 inch) to about 0.13 mm (0.005 inch). Operates at intervals. The small operating spacing of the intake-type seal assembly 42 passes through the seal teeth 88 and is combined with a complex flow path between the first and second primary seal surfaces 50 and 82 to minimize leakage.

  FIG. 6 illustrates another seal assembly 142 that includes a rotor 144, a seal support 146, and a seal body 148 that includes a radially extending portion 170 and an axially extending portion 172, respectively. The seal assembly 142 is similar in structure to the seal assembly described above, but the first and second primary seal surfaces 150 and 182 are different in shape. The circumferential start seal 184 extends axially from the outer end of the radially extending portion 170. The fluid passages 186, 187 may be formed through the radially extending portion 170 in a known manner as required for static pressure balance of the seal body 148.

  The second primary seal surface 182 includes at least one and optionally a plurality of annular, radially spaced axially extending seals to form a radially continuous or serpentine flow path. Teeth 188 are included. In the example shown, there are three seal teeth 188A, 188B, 188C having a tapered cross-sectional shape separated by an annular round bottom groove 190.

  The characteristics of the seal between the first and second primary seal surfaces 150 and 182 may be varied for a particular application in a manner similar to that described above with respect to the seal assembly 48.

  An annular seal groove 92 having a round bottom is formed in the first primary seal surface 150. The corresponding seal teeth 188C have a greater height than the other seal teeth 188A and 188B and project into the seal groove 92 to further reduce leakage during operation.

  These seal assemblies reduce leakage compared to flat end seals by providing a complex leak path called a labyrinth seal. However, in contrast to prior art labyrinth seals, which can rub adjacent components, the spacing between the seal elements is controlled so that the seal teeth do not rub against the seal rotor. This also provides an efficient seal at the time of engine manufacture and after prolonged use.

  The end face seal assembly has been described above. While particular embodiments of the present invention have been described, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention.

1 is a schematic side view of a portion of a prior art gas turbine engine. 1 is a schematic cross-sectional side view of an end face seal assembly configured in accordance with an embodiment of the present invention. FIG. 3 is a front view of a portion of the end face seal assembly of FIG. 2. FIG. 3 is an enlarged cross-sectional view of a portion of the end face seal assembly of FIG. 2. FIG. 3 is another enlarged cross-sectional view of a portion of the end seal assembly of FIG. FIG. 6 is a schematic cross-sectional side view of another exemplary end face seal assembly.

Explanation of symbols

12 'diffuser casing 24' core shaft 42 seal assembly 44 rotor 46 seal support 47 secondary seal surface 48 seal body ("slider")
50 Primary sealing surface 50A Inner part 50B Outer part 52 Rear part 54 Radially extending flange 56 Fastener 58 Front part 60 Spring seat 62 Cylindrical body 63 Mounting ear 64 Arc-shaped flange 65 Fastener 66 Arrangement rail 68 Arrangement slot 70 Radial extension Present portion 72 Axial extending portion 73 Pull back spring 74 Radially outward extending flange 76 Spring pocket 78 Secondary seal 80 Groove 82 Second primary seal surface 82A Inner portion 82B Outer portion 84 Circumferential seal teeth ("start seal"")
86 Fluid passage 87 Fluid passage 88 Axial extending seal teeth 88A Seal teeth 88B Seal teeth 90 Groove 92 Annular seal groove 142 Seal assembly 144 Rotor 146 Seal support 148 Seal body 150 First primary seal surface 170 Radially extending portion 172 Axial extension portion 182 Second primary seal surface 184 Circumferential start seal 186 Fluid passage 187 Fluid passage 188 Axial extension seal teeth 188A Seal teeth 188B Seal teeth 188C Seal teeth 190 Round bottom groove A Seal teeth cross section angle D Axial distance H Seal tooth height L Seal tooth radial range or total length P Seal tooth radial spacing ("pitch")
S Axial distance angle of seal teeth ("tilt angle")
W Tip width of seal teeth

Claims (10)

A seal assembly disposed about an axis of a gas turbine engine comprising:
A rotor (44) having a first primary sealing surface (50) facing axially;
A stationary seal support (46) disposed adjacent to the rotor (44);
An annular seal body (48) attached to the seal support (46) and disposed between the rotor (44) and the seal support (46);
The seal body (48) is axially movable with respect to the seal support (46) and has a second primary seal surface facing in the axial direction opposite the first primary seal surface (50). 47) a substantially radially extending portion defining a substantially axially extending portion (72);
A seal assembly wherein at least a selected one of the first primary seal surface (50) and the second primary seal surface (82) has at least one annular seal tooth (88) extending axially therefrom. .   The seal assembly of any preceding claim, wherein the seal support (46) defines a radially facing secondary seal surface (47).   The axially extending portion of the seal body (48) carries a secondary seal that contacts the secondary seal surface (47) while moving the seal body (48) in an axial direction. The seal assembly as described.   The seal assembly of any preceding claim, wherein at least one of the seal teeth (88) has a tapered cross-sectional shape.   The seal assembly of claim 1, wherein the first and second primary seal surfaces include an annular seal groove (80) located therein opposite the seal teeth (88). The second primary sealing surface (47),
A substantially planar inner portion (50A);
The seal assembly of claim 1, including an outer portion (50B) disposed radially outward of the inner portion (50A) and carrying the seal teeth (88).   The first primary sealing surface (50) has an inner portion (50A) and an outer portion (50B) offset axially forward of the inner portion (50A) to reduce radial flow, The seal assembly of claim 1, wherein the seal assembly is defined by a bifurcation point (50) between the inner and outer portions.   The at least one end portion of the seal teeth (88) is disposed axially between the inner portion (50A) and the outer portion (50B) of the first primary seal surface (50). Seal assembly.   The seal assembly of any preceding claim, further comprising an annular start seal extending generally axially from the second primary seal surface (82).   At least one pull-back spring (73) disposed between the seal body (48) and the seal support (46) so as to bias the seal body (48) away from the rotor (44). The seal assembly of claim 1, further comprising:

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