Patent Publication Number: US-2023151739-A1

Title: Brush seal comprising a rubbing-tolerant support ring structure

Description:
STATEMENT REGARDING SPONSORED RESEARCH OR DEVELOPMENT 
     The work leading to this invention was funded in accordance with Grant Agreement No. CS2-ENG-GAM-2014-2015-01 in the course of the European Union&#39;s Seventh Framework Programme (FP7/2007-2013) for the Clean Sky Joint Technology Initiative. 
     CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit to German Patent Application No. DE 102021129985.3, filed on Nov. 17, 2021, which is hereby incorporated by reference herein. 
     FIELD 
     The present disclosure relates to a brush seal for a gas turbine, in particular an aircraft gas turbine, having a support ring structure. 
     BACKGROUND 
     Currently, a support ring structure or support ring of a brush seal for a gas turbine is configured such that there is no contact with the rotating part or rotor portion of the sealing system while the gas turbine is in operation. The diameter of the support ring, or of the rotating part or rotor portion, is thus selected so that the two components are prevented from rubbing against each other, as any such rubbing would cause damage to the rotating part or rotor portion. If a radial and/or axial relative movement of the rotor portion and support ring structure in a gas turbine is or becomes greater, a larger diameter of the support ring structure or support ring has to be selected accordingly. In the process, a large gap between the support ring and the rotor portion leads to a larger leakage surface area of the bundle of bristles. In addition, when the support ring has a larger diameter, the wire overhang of the bundle of bristles at the radially inner edge of said support ring becomes larger, as a result of which the “blow-over effect” of the bundle of bristles (bending of bristles underneath the support ring) occurs sooner. Consequently, a brush seal of this kind cannot be used in as many applications, or a bundle of bristles having greater axial rigidity has to be used. The latter option, however, has drawbacks in terms of the admission of heat and abrasive wear. 
     For the design of various brush seals, reference is made, by way of example, to the following documents: EP 0 453 315 B1, U.S. Pat. Nos. 5,308,088 A, 5,351,871 A, 7,461,847 B2, 6,471,212 B1, and 10,024,192 B2. 
     SUMMARY 
     In an embodiment, the present disclosure provides a brush seal that can be used for a gas turbine. The brush seal includes a support ring structure; and at least one bundle of bristles that is arranged in an axial direction on the support ring structure. The support ring structure has a basis portion arranged radially on the outside, and a supporting portion arranged radially on the inside. The supporting portion has a supporting surface that faces the bundle of bristles and supports the bundle of bristles in the axial direction. The supporting portion has a radially inner edge portion that faces a rotor portion of the gas turbine when the brush seal is in an assembled state. Starting from the radially inner edge portion, the supporting portion has a radial supporting-portion length together with a substantially constant axial supporting-portion width, the supporting-portion length being greater than the supporting-portion width by at least a factor of four. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Subject matter of the present disclosure will be described in even greater detail below based on the exemplary figures. All features described and/or illustrated herein can be used alone or combined in different combinations. The features and advantages of various embodiments will become apparent by reading the following detailed description with reference to the attached drawings, which illustrate the following: 
         FIG.  1    is a schematic representation of the general structure of an aircraft gas turbine; 
         FIG.  2    is a schematic sectional view of an example of a brush seal; 
         FIG.  3    is a schematic sectional view of a further example of a brush seal; and 
         FIG.  4    is a schematic sectional view of a further example of a brush seal. 
     
    
    
     DETAILED DESCRIPTION 
     Aspects of the present disclosure provide a brush seal in which the above drawbacks can be avoided. 
     According to an aspect of the present disclosure, a brush seal for a gas turbine, in particular an aircraft gas turbine, is provided. The brush seal may include a support ring structure and at least one bundle of bristles that is arranged in the axial direction on the support ring structure, the support ring structure having a basis portion arranged radially on the outside and a supporting portion arranged radially on the inside, the supporting portion having a supporting surface which faces the bundle of bristles and supports the bundle of bristles in the axial direction, and the supporting portion having a radially inner edge portion that faces a rotor portion of the gas turbine when the brush seal is in an assembled state. According to an aspect of the present disclosure, starting from the radially inner edge portion, the supporting portion has a radial supporting-portion length together with a substantially constant axial supporting-portion width, the supporting-portion length being greater than the supporting-portion width by at least a factor of four. 
     A configuration of this kind provides a support ring that does not cause critical damage to the rotating component or rotor portion if any rubbing occurs. In other words, the support ring is configured to be significantly thinner at its radially inner supporting portion in order to ensure that the damage to the rotor portion is minimized in the event of rubbing. The supporting portion or support ring structure can thus also be described as being rubbing-tolerant. Despite its minimized axial supporting-portion width compared with known support rings, in conventional areas of operation of a gas turbine the support ring takes on the sealing action and also the action of supporting the bundle of bristles. 
     In the brush seal, a transitional portion may adjoin the supporting portion radially on the outside, which transitional portion has at least one curve contour that diverges from the radial direction. By means of a curve contour of this kind, forces acting on the relatively thin supporting portion in the axial direction can be optimally transmitted to the support ring structure or basis portion without any undesirable peak stresses occurring in the transition region, which poses a risk of cracks forming. 
     In the process, the transitional portion may have an axial transitional width that is greater than the supporting-portion width. The axial transitional width may also increase in the radial direction either constantly or discretely. 
     In the brush seal, the supporting portion, the transitional portion, and the basis portion of the support ring structure may be formed in one piece. In particular, in this case the support ring structure may be manufactured as a turned part, a sheet metal part, or additively. 
     Alternatively, in the brush seal the supporting portion and the transitional portion may be configured as a single-piece supporting element that is connected to the basis portion of the support ring structure. In particular, in this case the support ring structure may be manufactured or formed by two sheet metal parts. 
     In the brush seal, the supporting-portion length may be greater than the supporting-portion width by at most a factor of twenty. In particular, the supporting-portion length may be greater than the supporting-portion width by a factor of five to fifteen. 
     In the brush seal, the supporting-portion length may be approximately 1 mm to 4 mm, in particular 2 mm to 3 mm, and the supporting-portion width may be approximately 0.1 mm to 0.8 mm, in particular 0.2 mm to 0.6 mm. 
     The brush seal may have a cover ring structure, the bundle of bristles being received between the cover ring structure and the support ring structure in the axial direction. 
     According to an aspect of the present disclosure, a gas turbine, in particular an aircraft gas turbine, is also provided. The gas turbine may include at least one above-described brush seal surrounding a rotor portion of the gas turbine. In particular, the brush seal can be used in the region of a low-pressure turbine. Other installation sites in the gas turbine are also conceivable, for example the high-pressure compressor and the like. 
     In the gas turbine, the rotor portion surrounded by the brush seal may have, in a rubbing region facing the brush seal, a radial rotor-portion thickness that is greater than the radial rotor thickness outside the rubbing region. A wall thickness of the rotor portion is greater in the rubbing region so that the rotor is designed to be more robust against any potential rubbing by the supporting portion. 
     Alternatively or additionally, in the gas turbine the rotor portion may have a coating, located radially on the outside, in the rubbing region. In particular, a coating of this kind may be made of a material that is more resistant than the material from which the rotor portion is made. 
     Aspects of the present disclosure will now be described by way of example, and not by way of limitation, with reference to the accompanying drawings. 
     In the present disclosure directional words such as “axial,” “axially,” “radial,” “radially,” and “circumferential” should be taken with respect to the machine axis of the gas turbine, unless explicitly or implicitly indicated otherwise by the context. 
       FIG.  1    is a schematic representation of an aircraft gas turbine  10 , illustrated merely by way of example as a turbofan engine. The gas turbine  10  comprises a fan  12 , which is surrounded by a schematically indicated duct  14 . A compressor  16  adjoins the fan  12  in the axial direction AR of the gas turbine  10  and is received in a schematically indicated inner casing  18  and may be single-stage or multi-stage. The combustor  20  adjoins the compressor  16 . Hot exhaust gas flowing out of the combustor then flows through the adjoining turbine  22 , which may be single-stage or multi-stage. In this example, the turbine  22  comprises a high-pressure turbine  24  and a low-pressure turbine  26 . A hollow shaft  28  connects the high-pressure turbine  24  to the compressor  16 , in particular a high-pressure compressor  29 , such that they are jointly driven or rotated. A shaft  30  located further inward in the radial direction RR of the turbine connects the low-pressure turbine  26  to the fan  12  and to a low-pressure compressor  32  such that they are jointly driven or rotated. Adjoining the turbine  22  is an exhaust nozzle  33 , which is only schematically indicated here. 
     In the illustrated example of an aircraft gas turbine  10 , a turbine center frame  34  is arranged between the high-pressure turbine  24  and the low-pressure turbine  26  and arranged around the shafts  28 ,  30 . Hot exhaust gases from the high-pressure turbine  24  flow through the turbine center frame  34  in its radially outer region  36 . The hot exhaust gas then flows into an annular space  38  in the low-pressure turbine  26 . The compressors  28 ,  32  and turbines  24 ,  26  are represented, by way of example, by rotor blade rings  27 . For the sake of clarity, the usually present stator vane rings  31  are shown, by way of example, only for the compressor  32 . 
     Examples of brush seals which can be inserted or arranged in particular in the region of a turbine  22 , in particular a low-pressure turbine  26 , or a compressor  16 , in particular a high-pressure compressor  29 , will be described in the following. 
       FIG.  2    is a simplified and schematic sectional view of a brush seal  40 . The brush seal  40  comprises a cover ring structure  42 , which can also be referred to simply as a cover ring  42 . In addition, the brush seal  40  has a support ring structure  44 , which in simpler terms can also be referred to as a support ring. A bundle of bristles  46  is arranged or received between the cover ring structure  42  and the support ring structure  44  in the axial direction AR. 
     The support ring structure  42  has a basis portion  48  arranged radially on the outside and a supporting portion  50  arranged radially on the inside. The supporting portion  50  has a supporting surface  52  that faces the bundle of bristles  46  and supports the bundle of bristles  46  in the axial direction AR. The supporting portion  50  also has a radially inner edge portion  54  that faces a rotor portion  56  of the gas turbine  10  when the brush seal  40  is in an assembled state. By way of example, the rotor portion  56  may be connected to a shaft  28  or to a shaft  30  of the gas turbine  10  ( FIG.  1   ). 
     Starting from the radially inner edge portion  54 , the supporting portion  50  has a radial supporting-portion length SL together with a substantially constant axial supporting-portion width SB. In this case, the supporting-portion length SL is greater than the supporting-portion width SB by at least a factor of four. As a result, a support ring structure  44  is provided that does not cause critical damage to the rotating component or rotor portion  56  if any rubbing against the rotor portion  56  occurs. In other words, the support ring structure  44  is configured to be significantly thinner at its radially inner supporting portion  50  in order to ensure that the damage to the rotor portion  56  is minimized in the event of rubbing. Despite this minimized axial supporting-portion width SB compared with known support rings, in conventional areas of operation of a gas turbine the support ring structure takes on the sealing action and also the supporting action for the bundle of bristles  46 . 
     A transitional portion  58  adjoins the supporting portion  50  radially on the outside and has at least one curve contour  60  that diverges from the radial direction RR. In the example in  FIG.  2   , the two curved contours  60  have a convex and a concave curvature, respectively, formed one after the other. 
     In this case, the transitional portion  58  has an axial transitional width UB that is greater than the supporting-portion width SB. In particular, the axial transitional width UB increases constantly in the radial direction RR in the example in  FIG.  2   . It can also be seen in  FIG.  2    that the supporting portion  50 , the transitional portion  58 , and the basis portion  48  of the support ring structure  44  are formed in one piece. In particular,  FIG.  2    shows a support ring structure  44  that is manufactured either as a turned part or additively. The division of the support ring structure  44  into the supporting portion  50 , the transitional portion  58 , and the basis portion  48  is qualitatively indicated by the dash-dot lines in  FIG.  2   . 
     It can also be seen in  FIG.  2    that the rotor portion  56  surrounded by the brush seal  40  has, in a rubbing region  62  facing the brush seal, a radial rotor thickness RDA that is greater than the radial rotor thickness RDN outside the rubbing region  62 . Enlarging the rotor thickness in this way is optional and brings the advantage whereby the wall thickness RDA of the rotor portion  56  is greater in the rubbing region  62  so that the rotor is designed to be more robust against any potential rubbing by the supporting portion  50 . 
       FIG.  2    also shows another optional feature of the rotor portion  56 . The rotor portion  56  may have a coating  64 , located radially on the outside, in the rubbing region  62 . 
     It should be noted that the greater radial thickness or wall thickness RDA of the rotor portion  56  in the rubbing region  62  and the coating  64  may be provided in combination, each by themselves, or not at all. This applies to the example in  FIG.  2    and also to the examples in  FIGS.  3  and  4    to be described below. 
       FIG.  3    is a schematic sectional view of a further example of a brush seal  40 . The brush seal  40  comprises a cover ring structure  42 , which can also be referred to simply as a cover ring  42 . In addition, the brush seal  40  has a support ring structure  44 , which in simpler terms can also be referred to as a support ring. A bundle of bristles  46  is arranged or received between the cover ring structure  42  and the support ring structure  44  in the axial direction AR. 
     In this example too, the support ring structure  42  has a basis portion  48  arranged radially on the outside and a supporting portion  50  arranged radially on the inside. The supporting portion  50  has a supporting surface  52  that faces the bundle of bristles  46  and supports the bundle of bristles  46  in the axial direction AR. The supporting portion  50  also has a radially inner edge portion  54  that faces a rotor portion  56  of the gas turbine  10  when the brush seal  40  is in an assembled state. By way of example, the rotor portion  56  may be connected to a shaft  28  or to a shaft  30  of the gas turbine  10  ( FIG.  1   ). 
     In this example too, starting from the radially inner edge portion  54 , the supporting portion  50  has a radial supporting-portion length SL together with a substantially constant axial supporting-portion width SB. In this case, the supporting-portion length SL is greater than the supporting-portion width SB by at least a factor of four. As a result, a support ring structure  44  is provided that does not cause critical damage to the rotating component or rotor portion  56  if any rubbing against the rotor portion  56  occurs. In other words, the support ring structure  44  is configured to be significantly thinner at its radially inner supporting portion  50  in order to ensure that the damage to the rotor portion  56  is minimized in the event of rubbing. Despite this minimized axial supporting-portion width SB compared with known support rings, in conventional areas of operation of a gas turbine the support ring structure takes on the sealing action and also the supporting action for the bundle of bristles  46 . 
     A transitional portion  58  adjoins the supporting portion  50  radially on the outside and has at least one curve contour  60  that diverges from the radial direction RR. In the example in  FIG.  3   , the two curved contours  60  have a convex and a concave curvature, respectively. 
     In this case, the transitional portion  58  has an axial transitional width UB that is greater than the supporting-portion width SB. In particular, the axial transitional width UB increases constantly in the radial direction RR in the example in  FIG.  3   . It can also be seen in  FIG.  32    that the supporting portion  50 , the transitional portion  58 , and the basis portion  48  of the support ring structure  44  are formed in one piece. In particular,  FIG.  3    shows a support ring structure  44  that is manufactured as a formed sheet metal part. The division of the support ring structure  44  into the supporting portion  50 , the transitional portion  58 , and the basis portion  48  is qualitatively indicated by the dash-dot lines in  FIG.  3   . 
     The example in  FIG.  3    also shows the rotor portion  56  having a greater rotor thickness or wall thickness RDA in the rubbing region  62 , albeit without a coating. 
       FIG.  4    shows a similar example of a brush seal  40  to that in  FIG.  3   . Unlike the single-piece configuration of the support ring structure  44  in  FIG.  3    (and also  FIG.  2   ), the support ring structure  44  in  FIG.  4    is configured in multiple parts, in particular two parts. In this case, the supporting portion and the transitional portion  58  are configured as a single-piece supporting element  66  that is connected to the basis portion  48  of the support ring structure. The basis portion  48  and the supporting element  66  are each made from formed sheet metal parts. Otherwise, reference should be made to the above description of  FIGS.  2  and  3    for the other reference signs shown in  FIG.  4   ; said description is also valid for the example of the brush seal  40  in  FIG.  4    and applicable analogously. 
     For all the examples of brush seals  40  disclosed above with reference to  FIGS.  2  to  4   , the following applies in relation to the supporting portion  50  together with its supporting-portion length SL and its supporting-portion width SB: the supporting-portion length SL is greater than the supporting-portion width SB by at most a factor of twenty. By way of example, the supporting-portion length SL may be approximately 1 mm to 4 mm, in particular 2 mm to 3 mm, and the supporting-portion width SB may be approximately 0.1 mm to 0.8 mm, in particular 0.2 mm to 0.6 mm. 
     While subject matter of the present disclosure has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. Any statement made herein characterizing the invention is also to be considered illustrative or exemplary and not restrictive as the invention is defined by the claims. It will be understood that changes and modifications may be made, by those of ordinary skill in the art, within the scope of the following claims, which may include any combination of features from different embodiments described above. 
     The terms used in the claims should be construed to have the broadest reasonable interpretation consistent with the foregoing description. For example, the use of the article “a” or “the” in introducing an element should not be interpreted as being exclusive of a plurality of elements. Likewise, the recitation of “or” should be interpreted as being inclusive, such that the recitation of “A or B” is not exclusive of “A and B,” unless it is clear from the context or the foregoing description that only one of A and B is intended. Further, the recitation of “at least one of A, B and C” should be interpreted as one or more of a group of elements consisting of A, B and C, and should not be interpreted as requiring at least one of each of the listed elements A, B and C, regardless of whether A, B and C are related as categories or otherwise. Moreover, the recitation of “A, B and/or C” or “at least one of A, B or C” should be interpreted as including any singular entity from the listed elements, e.g., A, any subset from the listed elements, e.g., A and B, or the entire list of elements A, B and C. 
     LIST OF REFERENCE SIGNS 
     
         
           10  Aircraft gas turbine 
           12  Fan 
           14  Duct 
           16  Compressor 
           18  Inner casing 
           20  Combustor 
           22  Turbine 
           24  High-pressure turbine 
           26  Low-pressure turbine 
           28  Hollow shaft 
           29  High-pressure compressor 
           30  Shaft 
           31  Stator vane ring 
           32  Low-pressure compressor 
           33  Exhaust nozzle 
           34  Turbine center frame 
           36  Radially outer region 
           38  Annular space 
           40  Brush seal 
           42  Cover ring structure 
           44  Support ring structure 
           46  Bundle of bristles 
           48  Basis portion 
           50  Supporting portion 
           52  Supporting surface 
           54  Edge portion 
           56  Rotor portion 
           58  Transitional portion 
           60  Contour 
           62  Rubbing region 
           64  Coating 
           66  Supporting element 
         AR Axial direction 
         RR Radial direction 
         RDA Rotor thickness or wall thickness 
         RDN Rotor thickness or wall thickness 
         SB Supporting-portion width 
         SL Supporting-portion length 
         UB Transitional width