FR2902172A1 - SUCTION LABYRINTH SEAL - Google Patents

Abstract

A seal body (48) comprising an axially extending annular portion (72), a radially extending portion (70) defining a main sealing surface (50), and cooperating with the axially extending portion (72) to define a cross section of generally L-shaped; and at least one annular sealing tooth (88) with axial extension.

Description

B07-2262EN Company known as: GENERAL ELECTRIC COMPANY JOINT A LABYRINTH

VACUUM

  Invention of: HERRON William L. ALBERS Joseph C. GLYNN Christopher C. CRUDGINGTON Peter.

  Priority of two patent applications filed in the United States of America on June 10, 2006 under No. 60 / 804,432 and July 20, 2006 under No. 11 / 458,764. 1 SUCTION LABYRINTH SEAL

  The present invention generally relates to seals with radial faces for rotating machines and, more particularly, seals 5 with suction radial faces or gas equilibrium. Radial-sided seals are used to minimize leakage through a space between two rooms, which leaks from an area at a higher pressure to a lower pressure area. Such seals have been used in rotating machines, for example steam turbines and gas turbines. In gas turbines, radial face seals are used between static materials, between rotor and stator parts and can be used between different rotating parts. The gaps or leak passages between these different parts must be hermetically sealed, and the seals applied must be able to compensate for dimensional variations of the spaces under the effect of differences in thermal and mechanical expansion of the parts during the operating cycle. of the machine. The variable space is hermetically sealed by either creating a flexible contact held between the pieces, for example by means of a brush seal or a sheet joint, or by creating a complex leak path that creates pressure losses, and therefore a reduced flow, for example using a labyrinth seal. In a labyrinth seal between rotating parts and static parts, the extremes when closing the gap can be absorbed by allowing rotor labyrinth teeth to rub against a softer ("abradable") stator matrix. Because of the initial gaps, and because of the contact of the seals against adjacent surfaces, none of these seals can meet all performance and service life requirements. By way of example, FIG. 1 shows a part of a gas turbine engine comprising the rear end of a compressor 10, a diffuser 12, an annular combustion chamber 14 and a high pressure turbine 16 which comprises a fixed distributor 18 and rotating vanes 20 of turbine carried by a turbine rotor 22. The compressor 10 is driven by the turbine 16 through a shaft 24. The gap between the primary flow path "F" of the hot gases and the shaft 24 defines a secondary flow path. For a variety of reasons, including maximizing yield and preventing wear, it is desirable to minimize leakage through the secondary flow path as much as possible. For this, there is provided one or more sets of seals which reduce or prevent flow through them. In the illustrated example, a compressor discharge pressure (PRC) seam assembly 26 including a rotatable member 28 having a plurality of radially outwardly extending annular sealing teeth 30 placed opposite an element fixed abradable 32, is disposed towards the interior of the diffuser 12. A front outer seal (JEA) 34 comprising a rotary element 36 having a plurality of annular sealing teeth extending radially outwards, placed opposite an element fixed abradable 40, is disposed towards the inside of the turbine distributor 18. Radial-face gaskets are also elsewhere in the engine. The PRC gasket assembly 26 and JEA 34 are degraded during prolonged operation as described above.

  The present invention provides a radial-face seal with low leakage and long life. The space between the sealing elements is controlled so that the sealing teeth do not rub against the rotor. This ensures sealing efficiency both during the manufacture of the engine after a long period of operation. It is estimated that leakage through the face of a primary seal can be reduced by about 25% compared to prior art radial face seals. According to a first aspect, the invention provides a seal assembly, comprising: a first annular element defining a first substantially axially oriented main sealing surface; and a second annular element defining a second substantially axially oriented main sealing surface, the second annular member being axially movable relative to a seal support so that the second major sealing surface is disposed look at the first main sealing surface; at least one of the first main sealing surface and the second main sealing surface having at least one annular sealing tooth extending axially therefrom. According to another aspect of the invention, a seal body for a seal assembly disposed about an axis comprises: an axially extending annular portion; a radially extending portion defining a main sealing surface and cooperating with the axially extending portion to define a generally L-shaped cross section; and at least one annular sealing tooth extending axially from the main sealing surface. According to another aspect of the invention, a gasket assembly disposed about an axis for a gas turbine comprises: a rotor having a first axially oriented main sealing surface; a fixed seal support disposed in the immediate vicinity of the rotor; an annular seal body attached to the seal carrier and disposed between the rotor and the seal carrier, the seal body being movable axially with respect to the seal carrier, the annular seal body having a generally radially extending portion which defines a second axial-facing main sealing surface facing the first main sealing surface, and a generally axial extending portion; at least one of the first main sealing surface and the second main sealing surface having at least one annular sealing tooth extending axially therefrom. The axially extending portion of the seal body 48 carries a secondary seal which is in contact with the secondary sealing surface while permitting axial movement of the seal body. At least one of the sealing teeth may have a conical cross-sectional profile. The other of the first and second main sealing surfaces may comprise an annular sealing groove, the sealing groove being placed opposite the sealing teeth. The second main sealing surface may comprise a generally flat inner part and an outer part arranged radially outside the inner part and carrying the sealing teeth.

  The first main sealing surface has an inner portion, and an outer portion axially offset in front of the inner portion so that a step opposing a radial flow is defined at a junction of the inner and outer portions. A distal portion of at least one of the sealing teeth may be axially disposed between the inner and outer portions of the first major sealing surface. The seal may further include an annular starter seal extending generally axially from the second major seal surface.

  The seal may further include at least one return spring disposed between the seal body and the seal carrier to bias the seal body away from the rotor.

  The invention will be better understood on studying the detailed description of an embodiment taken by way of nonlimiting example and illustrated by the appended drawings in which: FIG. 1 is a schematic side view of a portion of a gas turbine according to the prior art; FIG. 2 is a schematic sectional side view of a radial-face seal assembly constructed in accordance with one embodiment of the invention; FIG. 3 is a front view of a portion of the radial-face gasket assembly of FIG. 2; FIG. 4 is an enlarged sectional view of a portion of the radial-sided seal assembly of FIG. 2; FIG. 5 is another enlarged sectional view of a portion of the radial-face seal assembly of FIG. 2; and FIG. 6 is a schematic sectional side view of another example of a radial-face seal assembly. Referring to the drawings, in which like reference numerals designate the same elements in all the various views, Figs. 2 and 3 show an example of a seal assembly 42 which prevents leaks between a relatively high pressure zone P (high) and a relatively low pressure zone P (low). In this particular example, the seal assembly 42 replaces a compressor discharge pressure (PRC) seal described above and is disposed between a central axis 24 'and a diffuser housing 12', however it should be understood that the details of the seal assembly 42 may be used in any application where a radial-face seal is required. The essential members of the seal assembly 42 may include a rotor 44, a fixed seal support 46 and a seal body 48 (sometimes referred to as a "slider"), all disposed about a longitudinal axis of the engine. The rotor 44 is generally disk-shaped and defines a first axially oriented main surface 50. The seal support 46 is a non-rotating, axially extending member and defines a radially-oriented secondary sealing surface 47. In the illustrated example, it is a continuous ring 360, but it could be designed as a segmented annular structure, or a series of individual supports. Its rear end 52 has a radial flange 54 attached to the diffuser 12 'by one or more fasteners 56. Its front end 58 carries one or more seats 60 of springs. In the present example, five spring seats are spaced equidistantly around the periphery of the seal support 46; however, the spring seats 60 could also be in the form of a continuous or segmented annular structure. As can be seen most clearly in FIG. 3, the spring seat 60 has a generally cylindrical body 62 and an arcuate flange 64 which defines a pair of laterally extending mounting lugs 63. The spring seat is secured to the seal support 46 by one or more fasteners 65. The body 62 includes an inwardly radially extending alignment rail 66, which is received in a complementary alignment groove 68 of the seal body 48 to maintain the desired relative angular alignment or "wedging" of the seal support 46 and the seal body 48. The seal body 48 is thus carried by the seal support 46 so as to be able to move axially but not laterally. The seal body 48 is an annular element which 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. As shown in FIG.

  A plurality of return springs 73 are disposed between the seats 60 of springs and a collar 74 of the radially outward extending joint body 48. The rear end of each return spring 73 is in a spring housing 76 of the flange 74, or in another suitable positioning means. The return springs 73 serve to move the seal body 48 away from the rotor 44. This function is described in more detail below. As illustrated, there are five compression type coil springs, but it is possible to use other types and numbers of springs. A secondary seal 78, for example a piston ring of a known type, is disposed in a groove 80 of the flange 74 and seals against the axially oriented, secondary sealing surface 47 of the set of spring support 46. The piston ring may be of a known type constituting a continuous (or nearly continuous) circumferential seal. The function of the secondary seal 78 is to prevent leakage along a path between the seal body 48 and the seal support 46, which undergoes the same pressure difference as the primary seal, while permitting axial movement of the body 48 of the seal. seal. It should be noted that the specific configuration of the gasket parts and mounting structure described above is not essential and can be modified to suit a particular application without affecting the functional aspects of the gasket assembly. As shown in FIGS. 4 and 5, the radially extending portion 70 of the seal body 48 defines a second axially oriented main sealing surface 82. This second main sealing surface 82 is disposed close to the rotor 44 and facing the first main sealing surface 50. A peripheral sealing tooth 84, commonly referred to as a "starter seal", extends axially from the the outer end of the radially extending portion 70 outwardly of the rotor 44 and, in this particular example, is inclined radially inwardly. Fluid passages 86, 87 are formed through the radially extending portion 70, in a known manner, according to the needs of the hydrostatic equilibrium of the joint body 48 in operation (which will be described in more detail below). ).

  The second main sealing surface 82 comprises a flat inner part 82A and an outer part 82B, separated by an annular groove 3. The outer part 82B comprises at least one, and possibly several annular sealing teeth 88, with axial extension, radially spaced apart from each other for forming a circuit-shaped or tortuous flow path to limit flow from the main flow path to the secondary flow path. In the example illustrated, there are two teeth 88A and 88B of conical cross sectional profile seal, separated by annular depressions 90 with rounded bottom. The teeth 88 could also, if desirable, project from a flat surface. It should also be understood that the configuration of the sealing teeth could be reversed, i.e. the sealing teeth 88 could instead be formed on the first main sealing surface. The configuration of the second main sealing surface 82 may be defined in part by various characteristics of the sealing teeth 88, including the number of sealing teeth 88, their height "H" in the axial direction, the width "W" of their points, their included angle in cross-section "A", their divergence in an axial direction or deviating from an axial direction, called the angle of inclination "S" (note that this angle is very small in the illustrated example), their spacing or radial pitch "P", and the extension or total radial length of the sealing teeth 88, denoted by "L". The following are non-limiting examples of these dimensions: height H of teeth: approximately 0.38 mm (0.015 '), angle A of the teeth: approximately 10, angle of inclination S: approximately 0 to approximately 45, width W of the tip: about 0.13 mm (0.00%) to about 0.76 mm (0.030%), and not about 1.3 mm (0.05%) to about 3.8 mm (0.15%). . These values can be modified to fit a specific application.

  In the illustrated example, the first main sealing surface 50 has an inner portion 50A and an outer portion 50B, which is axially offset forwardly a distance "D" from the inner portion 50A (see FIG. 2), the distance "D" being substantially equal to the axial distance of the ends of the sealing teeth 88 to the inner portion 82A of the second main sealing surface 82. With this configuration, a "step" which opposed to a radial flow is defined at the junction of the inner and outer portions 50A and 50B of the first main sealing surface 50 and, during operation, the distal portions of the sealing teeth 88 are disposed axially between the inner and outer portions. outer 50A and 50B of the first main sealing surface 50.

  In operation, the seal body 48 creates a seal in cooperation with the rotor 44. The return springs 73 hold the seal body 48 away from the rotor 44 to prevent contact between the two members when the engine is stopped. As the engine operating speed increases, the fluid pressures in the areas of the main and secondary engine flow paths increase, and as a result, the seal assembly 42 is subjected to increasing pressures which act on these axially oriented surfaces, which has the effect of causing the seal body 48 to approach the rotor 44. By choosing in a known manner the relative areas of the different parts of the joint body 48, the number and the dimensions of the passages 86, 87 and the dimensions of the return springs 73, hydrostatic equalization of the pressure of the seal assembly 42 is achieved under selected operating conditions. In this way, the second main sealing surface 82 never touches the first main sealing surface 52, but operates with a small axial clearance, for example from about 0.05 mm (0.002 ') to approximately 0.13 mm. (0.005 '). The low operating clearance of the suction seal assembly 42, combined with the complex flow path passing through the sealing teeth 88 and between the first and second sealing surfaces 50 and 82, greatly limits leakage. Fig. 6 shows another seal assembly 142 comprising a rotor 144, a seal support 146 and a seal body 148 with radially and axially extending portions 170 and 172, respectively. This seal assembly 142 has a similar structure to that of the described seal assembly but differs in the configuration of the first and second main sealing surfaces 150 and 182. A circumferential starter seal 184 extends axially from the end outer portion of the portion 170 radially extending. Fluid passages 186, 187 may be formed in a known manner through the radially extending portion 170, as required, for hydrostatic equilibration of the seal body 148. The second main sealing surface 182 comprises at least one, and optionally a plurality of radially spaced, radially extending annular sealing teeth 188 which are intended to constitute a circuit or tortuous flow path. in the radial direction. In the illustrated example, there are three sealing teeth 188A, 188B and 188C with conical cross section, separated by annular depressions 190 with a rounded bottom. The characteristics of the seal between the first and second main sealing surfaces 150 and 182 can be modified to suit a specific application, in a manner similar to that described above for the seal assembly 48. An annular ring-shaped annular groove 92 is formed in the first primary sealing surface 150. The corresponding sealing tooth 188C has a greater height, in the axial direction, than that of the other sealing teeth 188A and 188B. and will protrude into the seal groove 92 during operation to further reduce leakage. These seal assemblies exhibit the complex leakage path of a labyrinth seal and, in comparison with a flat-face seal, reduce leakage. However, unlike prior art labyrinth seals that can rub against adjacent parts, the clearance between the seal members is limited so that the sealing teeth do not rub against the seal rotor. This allows effective sealing both at the time of engine manufacture and after a long operating time.

  List of Marks 12 Diffuser Housing 24 Center Shaft 42 Seal Kit 44 Rotor 46 Seal Bracket 47 Secondary Sealing Surface 48 Seal ("Slider") Body 50 Main Sealing Surface 50A Internal Part 50B External Part 52 Rear End 54 Radial extension flange 56 Fasteners 58 Front end 60 Spring seats 62 Cylindrical body 63 Mounting ears 64 Arched edges 65 Fastening parts 66 Alignment rail 68 Alignment groove 70 Radial extension part 72 Axially extending part 73 Retraction springs 74 Radial outward collar 76 Spring housing 78 Secondary seal 80 Throat 82 Second main sealing surface 82A Inner part 82B Outer part 84 Circumferential sealing groove (and "starter seal" ") 86 Leakages 87 Leakages 88 Axially extending sealing teeth 88A Sealing teeth 88B Sealing teeth 90 gutter 92 Ring seal groove 142 Gasket set 144 Rotor 146 Gasket bracket 148 Seal body 150 First main sealing surface 170 Radial extension part 172 Axially extending part 182 Second primary sealing surface 184 Circumferential starter seal 186 Fluid passage 187 Fluid passage 188 Axially extending seal teeth 188A Sealing teeth 188B Sealing teeth 188C Sealing teeth 190 Rounded-bottomed depressions A Sealing-tooth angle in cross-section D Axial distance H Height of the sealing teeth L Extension or radial length of the sealing teeth P Radial spacing ("pitch") of the sealing teeth S Angle of the sealing teeth in the axial direction ("angle of inclination" ) W Width of the sealing teeth

Claims (10)

  A gasket assembly disposed about an axis of a gas turbine engine, comprising: a rotor (44) having a first axially oriented main sealing surface (50); a fixed seal support (46) disposed adjacent 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) being axially movable relative to the support (46) seal member, the annular seal body (48) comprising: a generally radially extending portion which defines a second axially oriented main sealing surface (47) facing the first major sealing surface (50), and a portion (72) with a generally axial extension; at least one surface selected from the first major sealing surface (50) and the second major sealing surface (82) having at least one annular sealing tooth (88) extending axially therefrom.   The seal assembly of claim 1, wherein the seal support (46) defines a radially-oriented secondary seal surface (47).   The seal assembly of claim 1, wherein the axially extending portion of the seal body (48) carries a secondary seal which engages the secondary seal surface (47) while permitting displacement. axial joint body (48).   The seal assembly of claim 1, wherein at least one of the sealing teeth (88) has a conical cross section.   The seal assembly of claim 1, wherein the other of the first and second major sealing surfaces has an annular seal groove (80), the seal groove (80) being positioned opposite the teeth of the seal. sealing (88).   The seal assembly of claim 1, wherein the second main sealing surface (47) comprises: a generally planar inner portion (50A); andan outer portion (50B) disposed radially outwardly of the inner portion (50A) and carrying the sealing teeth (88).   The seal assembly of claim 1, wherein the first main sealing surface (50) has an inner portion (50A), and an outer portion (50B) that is axially offset forwardly relative to the portion internal (50A) so that a step which opposes an axial flow is formed at a junction of the inner and outer portions (50).   The seal assembly of claim 7, wherein a portion of at least one of the sealing teeth (88) is disposed between the inner and outer portions of the first major sealing surface (50).   The seal assembly of claim 1, further comprising an annular starter seal extending generally axially from the second major seal surface (82).   The seal assembly of claim 1, further comprising at least one return spring (73) disposed between the seal body (48) and the seal support (46) for biasing the seal body (48). to move away from the rotor (44).