ABRADABLE STRUCTURE FOR A TURBOMACHINE, TURBOMACHINE HAVING AN ABRADABLE STRUCTURE, AND METHOD FOR MANUFACTURING AN ABRADABLE STRUCTURE

Abstract

An abradable structure (10) for a turbomachine (40) that is designed to be at least partially deformed and/or at least partially abraded by at least one abrading element (44, 47) of the turbomachine (40) during operation thereof; the at least one abradable structure (10) being formed at least regionally of structural elements (12, 14, 16, 18) that have a respective polygonal cross section (20, 22) that is oriented in a rub direction (X_A) of the abradable structure (10). The structural elements (12, 14, 16, 18) have a greater extent (X.sub.h, X.sub.r) in the rub direction (X_A) than in a direction of the abradable structure (10) that is orthogonal to the rub direction (X_A). Other aspects of the present invention relate to a turbomachine (40) having an abradable structure (10), as well as to a method for manufacturing an abradable structure (10).

Claims

1-11. (canceled)

12. An abradable structure for a turbomachine, the abradable structure designed to be at least partially deformed or at least partially abraded by at least one abrading element of the turbomachine during operation thereof; the at least one abradable structure comprising: at least regionally, structural elements having a respective polygonal cross section oriented in a rub direction of the abradable structure, wherein the structural elements have a greater extent in the rub direction than in a direction of the abradable structure orthogonal to the rub direction.

13. The abradable structure as recited in claim 12 wherein, at at least one respective structural element end in the rub direction, the structural elements have structural element walls converging in the rub direction and forming an acute interior angle.

14. The abradable structure as recited in claim 13 wherein the acute interior angle corresponds to an angle of between 10 and 80.

15. The abradable structure as recited in claim 14 wherein the acute interior angle corresponds to an angle of between 30 and 60

16. The abradable structure as recited in claim 15 wherein the acute interior angle corresponds to an angle of between 38 and 55.

17. The abradable structure as recited in claim 12 wherein the structural elements have at least two spaced apart element walls oriented along the rub direction.

18. The abradable structure as recited in claim 12 wherein at least one structural element of the structural elements has a hexagonal cross section or a diamond cross section.

19. The abradable structure as recited in claim 12 wherein mutually adjoining structural elements of the structural elements at least form a shared wall.

20. The abradable structure as recited in claim 19 wherein the mutually adjoining structural elements overlap at the shared wall.

22. The abradable structure as recited in claim 12 further comprising at least one carrier element adapted for attaching the abradable structure to the turbomachine.

20. The abradable structure as recited in claim 12 wherein the abradable structure is formed in one piece.

21. A turbomachine comprising the abradable structure as recited in claim 12.

22. A method for manufacturing the abradable structure as recited in claim 12 wherein the abradable structure is produced by an additive manufacturing process.

23. A method for manufacturing the abradable structure as recited in claim 12 wherein the abradable structure is produced by selective laser melting.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Further features of the present invention will become apparent from the claims and the exemplary embodiments. The features and feature combinations mentioned above in the description, as well as the features and feature combinations mentioned below in the exemplary embodiments and/or described in isolation may be used not only in the particular stated combination, but also in other combinations or alone, without departing from the scope of the present invention. Thus, variants of the present invention are also considered to have been included and described herein that are not explicitly described and explained in the exemplary embodiments, but derive from and may be produced by separate combinations of features from the stated variants. Embodiments and combinations of features are also considered to be disclosed herein that, therefore, do not have all of the features of an originally formulated independent claim. In the drawing,

[0023] FIG. 1a shows a cross-sectional view of a portion of a turbomachine, an abradable structure being accommodated on a casing of the turbomachine to enable a tip of a blade element acting as an abrading element to rub into the abradable structure;

[0024] FIG. 1b shows a cross-sectional view of a portion of the turbomachine, the abradable structure being accommodated on a rotor to enable the blade element acting as an abrading element to rub against the abradable structure;

[0025] FIG. 1c shows a cross-sectional view of a portion of the turbomachine, the abradable structure being accommodated on a stator to enable sealing fins acting as abrading elements to rub against the abradable structure;

[0026] FIG. 2a is a plan view of two structural elements of the abradable structure, the structural elements having a hexagonal cross section;

[0027] FIG. 2b is a plan view of a portion of the abradable structure having a plurality of adjacently disposed structural elements that have the hexagonal cross section;

[0028] FIG. 3a is a plan view of another structural element of the abradable structure, the further structural element having a diamond cross section; and

[0029] FIG. 3b is a plan view of an array of a plurality of structural elements that feature the diamond cross section.

DETAILED DESCRIPTION

[0030] FIGS. 1a and 1b each show a cross-sectional view of a portion of a turbomachine 40, it being possible for turbomachine 40 to be configured as an engine, for example. In FIG. 1a, an abradable structure 10 is configured on a casing 42, whereas abradable structure 10 in FIG. 1b is configured on a rotor 48 of turbomachine 40. In the present case, abradable structure 10 is formed in one piece and has a carrier element 36 that is adapted for attaching abradable structure 10 to turbomachine 40, thus to casing 42 (FIG. 1a) or to rotor 48 (FIG. 1b).

[0031] Turbomachine 40 has a plurality of blade elements, of which a blade element 44 having a blade tip 46 is shown in FIGS. 1a and 1b. FIG. 1a shows blade element 44 as a rotor blade, whereas FIG. 1b shows blade element 44 as a guide vane. During operation of turbomachine 40, blade element 44, formed as a rotor blade in FIG. 1a, rotates about an axis of rotation 50, abradable structure 10 permitting a rubbing in and thus a rubbing contact of blade tip 46 against abradable structure 10 or against a structural surface of abradable structure 10 facing blade tip 46. In FIG. 1b, abradable structure 10 permits a rubbing contact in the form of blade tip 46 and the structural surface of abradable structure 10 facing blade tip 46 rubbing against one another. Thus, the rubbing contact may be in the form of a rubbing in, as shown in FIG. 1a, or in the form of a rubbing against, as shown in FIG. 1b, depending on whether abradable structure 10 is accommodated on casing 42 or on rotor 48. Thus, generally, abradable structure 10 may allow a rubbing contact in the form of the rubbing in as shown in FIG. 1a, as well as a rubbing contact in the form of the rubbing against as shown in FIG. 1b.

[0032] FIG. 1c shows another sectional view through a turbomachine 40. This view shows an inner band 13, 15 of the rotor, upon which sealing fins 47, formed as abrading elements, are configured upstream of a rotor blade 44a and downstream thereof. Together with an abradable coating 10 of preceding upstream and downstream configured stator 44b, they produce a sealing action. Sealing fins 47 thereby rub into abradable coating 10 when the rotor expands in response to centrifugal forces or high temperatures. It may also be provided that sealing fins 47 rub into abradable structure 10 upon a start-up of the turbomachine. This may advantageously reduce or prevent a leakage in the operating state of turbomachine 40.

[0033] Abradable structure 10 is designed to be at least partially deformed by respective blade element 44 in response to a rubbing contact process carried out between blade element 44, respectively blade tip 46 and abradable structure 10 during operation of turbomachine 40 and, in addition or, alternatively, to be at least partially abraded. In this case, abradable structure 10 may be constituted of structural elements 12, 14, 16, 18 that may be adjacently disposed and, together, form the structural surface as an abradable liner. During operation of turbomachine 40, at least some of structural elements 12, 14, 16, 18 may become deformed and, additionally or alternatively, abraded, to keep a gap between blade tip 46 and abradable structure 10 as small as possible and, accordingly, be able to operate turbomachine 40 at a high level of efficiency. From the overall view of FIGS. 2a, 2b, 3a and 3b, it is discernible that structural elements 12, 14, 16, 18 may feature a respective polygonal cross section 20, 22 that is oriented in a rub direction X_A of abradable structure 10. The rubbing contact between abradable structure 10 and blade tip 46 may occur here in rub direction X_A; rub direction X_A being illustrated by an arrow in FIG. 2a through 3b. In the present case, polygonal cross section 20 is in the form of a hexagonal cross section, whereas polygonal cross section 22 is in the form of a diamond cross section. Thus, at least some of structural elements 12, 14, 16, 18 of abradable structure 10 may have a hexagonal cross section or a diamond cross section. Structural elements 12, 14, 16, 18 shown in FIG. 2a and, respectively, 2b feature the hexagonal cross section here, whereas structural elements 12, 14, 16, 18 shown in FIGS. 3a and 3b feature the diamond cross section. The hexagonal cross section is preferably in the form of a hybrid of honeycomb and diamond geometry, as is discernible, in particular, in FIG. 2a.

[0034] Polygonal cross sections 20, 22 preferably have an irregular form. In other words, polygonal cross sections 20, 22 have an irregular polygonal contour, as shown in the present case.

[0035] To obtain an especially favorable rub direction, as well as favorable sealing properties during operation of turbomachine 40, structural elements 12, 14, 16, 18 feature a greater extent X.sub.h, X.sub.r in rub direction X_A than in a direction X_S of abradable structure 10 that is orthogonal to rub direction X_A. Orthogonal direction X_S is likewise shown in FIG. 2a through 3b by an arrow that is oriented orthogonally to rub direction X_A.

[0036] Within the scope of the present description, the subscript h denotes a dimension that refers to the hexagonal cross section (see FIGS. 2a and 2b), whereas subscript r denotes a dimension that refers to the diamond cross section (see FIGS. 3a and 3b). Accordingly, extent X.sub.h denotes the extent of the structural elements, which have the hexagonal cross section, in rub direction X_A, whereas extent X.sub.r denotes the extent of structural elements 12, 14, 16, 18, which have the diamond cross section, in rub direction X_A.

[0037] At at least one respective structural element end 24 in rub direction X_A, structural elements 12, 14, 16, 18 feature structural element walls 26, 28 that converge in rub direction X_A and form a respective acute interior angle .sub.h, .sub.r. Respective acute interior angle .sub.h, .sub.r may thereby correspond to an angle of between 10 and 80, preferably of between 30 and 60, and especially of between 38 and 55. Especially beneficial rubbing and sealing properties of abradable structure 10 are attainable at an angle of between 38 and 55, in particular.

[0038] Structural elements 12, 14, 16, 18 may have at least two spaced apart element walls 30, 32 that are oriented along rub direction X_A. As shown in FIG. 2a, element wall 30, that is directly contiguous to structural element wall 26, may be joined thereto, whereas element wall 32, that is directly contiguous to structural element wall 28, may be joined thereto. In the case of structural element 12 having polygonal cross section 20 (hexagonal cross section), as shown in FIG. 2a, spaced apart element walls 30, 32 may have an extent in rub direction X_A having a side length a.sub.h. In the case of structural element 12 having polygonal cross section 22 (diamond cross section), as shown in FIG. 3a, element walls 30, 32 may be in the form of connecting pieces of the wall. On one side, element wall 30 is joined to structural element wall 26 and, on the other side, to a wall portion 38. On one side, element wall 32 is joined to structural element wall 28 and, on the other side, to a wall portion 39. Altogether, structural element walls 26, 28, as well as element walls 30, 32 and wall portions 38, 39 bound respective polygonal cross section 20, 22 of respective structural elements 12, 14, 16, 18.

[0039] FIGS. 2b and 3b show that mutually adjoining structural elements 12, 14, 16 are at least able to form a shared wall 34. Mutually adjoining structural elements 12, 14, 16 thereby overlap at shared wall 34, for example, in direction X_S that is orthogonal to rub direction X_A. This overlapping produces an offset in the array pattern of structural elements 12, 14, 16, 18 shown in FIG. 3b, so that, altogether, merely three structural element walls 26, 28 or element walls 30, 32 of structural elements 12, 14, 16 meet at nodal point 35. In comparison to related art structures, where four structural walls meet at one end of a honeycomb structure, for example, enhanced rubbing properties may be achieved by three structural element walls 26, 28 or element walls 30, 32 provided here coming together since less material of structural elements 12, 14, 16 is accumulated at nodal point 35 and, accordingly, a rubbing contact in rub direction X_A having a lower frictional resistance is made possible than in the case of related art structures.

[0040] In FIG. 2a, the respective dimensions of structural element 12 show a side length a.sub.h, a wall web thickness d.sub.h, an overhang angle .sub.h, an extent X.sub.h of the hexagonal cross section along rub direction X_A and a transverse extent L.sub.h along orthogonal direction X_S. As the respective dimensions of structural element 12 having the diamond cross section, FIG. 3a shows a side length a.sub.r, a wall web thickness d.sub.r, an overhang angle .sub.r, an extent X.sub.r of the diamond cross section along rub direction X_A, as well as a transverse extent L.sub.r along orthogonal direction X_S. In the present case, transverse extent L.sub.h, L.sub.r represents a cell width of respective structural elements 12, 14, 16, 18.

[0041] Respective overhang angle .sub.h, .sub.r indicates an inclination of respective structural element wall 28 relative to orthogonal direction X_S. In the present case, the following angular relationships may apply for respective angles .sub.h, .sub.r and .sub.h, .sub.r:

2.sub.h+.sub.h=180

2.sub.r+.sub.r=180.

[0042] Especially favorable values for the rubbing and sealing properties are derived for structural elements 12, 14 having polygonal cross section 20 when the following dimension values are known:

.sub.h=70; .sub.h=40; L.sub.h/a.sub.h=0.868.

[0043] Accordingly, the rubbing and sealing properties are also favorable in the case of geometrically similar structural elements. Thus, transverse extent L.sub.h may correspond, for example, to L.sub.h=0.868 mm orin the case of geometrically similar formsto a multiple thereof. The same holds for side length a.sub.h that may correspond to a value of a.sub.h=1 mm.

[0044] Generally, the sealing action and rubbing properties may be enhanced in response to an increasing overhang angle .sub.h, .sub.r (and thus a smaller interior angle .sub.h, .sub.r). Generally, the sealing action is made possible by reducing side length a.sub.h, a.sub.r since this yields particularly small leakage areas. The rubbing properties are enhanced by enlarging side length a.sub.h, a.sub.r.

[0045] Especially effective rubbing and sealing properties are attainable for structural elements 12, 14, 16, 18 having the diamond cross section (polygonal cross section 22) when the following dimension values are provided:

.sub.r=63.5; .sub.r=53; L.sub.r/a.sub.r=0.894.

[0046] In summary, the present invention describes an abradable structure 10 having structural elements 12, 14, 16, 18, which, with respect to the geometry thereof (polygonal cross section 20, 22), are optimized to achieve especially favorable rubbing and sealing properties during operation of turbomachine 40 having abradable structure 10 or having a plurality of such abradable structures. In comparison to related art honeycomb structures, respective structural elements 12, 14, 16, 18 may have a greater wall thickness (wall web thickness d.sub.h, d.sub.r) and, accordingly, are particularly suited for manufacturing in the scope of an additive manufacturing process, for example, by selective laser melting. The honeycomb web distances (transverse extent L.sub.h, L.sub.r) which are narrow in comparison to related art honeycomb structures make it possible to achieve an especially favorable sealing action, thus especially favorable sealing properties. Elongating structural elements 12, 14, 16, 18 in rub direction X_A also makes it possible to manufacture wall web thicknesses d.sub.h, d.sub.r having values of d.sub.h130 m or d.sub.r130 m without the rubbing properties being degraded in comparison to the related art honeycomb structures. The production by an additive manufacturing process makes possible a single-piece manufacturing of entire abradable structure 10, thus, for example, a one-piece manufacturing of structural elements 12, 14, 16, 18 and of carrier element 36 which may be adapted to attach abradable structure 10 to turbomachine 40. Forming abradable structure 10 in one piece makes it possible to economize on production time and on the manufacturing costs of abradable structure 10. Inconel 718 may be used, for example, as material for abradable structure 10. This material may first be prepared in powder form and be bonded to abradable structure 10 by the additive manufacturing process.

REFERENCE NUMERAL LIST

[0047] 10 abradable structure [0048] 12 structural element [0049] 13 upstream inner band [0050] 14 structural element [0051] 15 downstream inner band [0052] 16 structural element [0053] 18 structural element [0054] 20 polygonal cross section [0055] 22 polygonal cross section [0056] 24 structural element end [0057] 26 structural element wall [0058] 28 structural element wall [0059] 30 element wall [0060] 32 element wall [0061] 34 shared wall [0062] 35 nodal point [0063] 36 carrier element [0064] 38 wall portion [0065] 39 wall portion [0066] 40 turbomachine [0067] 42 casing [0068] 44 abrading element; blade element [0069] 44a rotor blade or turbine blade [0070] 44b stator blade or guide vane [0071] 46 blade tip [0072] 47 sealing fin [0073] 48 rotor [0074] 50 axis of rotation [0075] a.sub.h side length [0076] a.sub.r side length [0077] d.sub.h wall web thickness [0078] d.sub.r wall web thickness [0079] .sub.h overhang angle [0080] .sub.r overhang angle [0081] .sub.h acute interior angle [0082] .sub.r acute interior angle