Sealing assembly

A sealing assembly is provided for sealing against a component. The sealing assembly comprises a seal carrier and a continuous seal element that is attached to the seal carrier at at least two discrete positions of attachment. The seal element is provided with a sealing surface that is arranged to seal against the component. The seal element is further provided with a thermal expansion slot that is located between the discrete positions of attachment and which extends from a first edge of the seal element over a portion of the width of the seal element. This allows the seal carrier and seal element to thermally expand in the length direction at different rates.

The invention relates to a sealing assembly, and particularly, although not exclusively, to a sealing assembly for providing a seal against a liner panel in the exhaust system of a gas turbine engine.

The exhaust system of a gas turbine engine includes a substantially annular casing having an annular arrangement of liner panels disposed therein. The arrangement of liner panels comprises a plurality of rings (or annuluses) of liner panels located axially next to one another with a gap between adjacent rings. Alternatively an exhaust system of a gas turbine engine may include a non circular casing (for example of elliptical cross section or polygonal cross section) having an arrangement of liner panels disposed therein which define a non circular gas flow path (for example of elliptical cross section or polygonal cross section respectively).

A cooling air duct is defined between the casing and the arrangement of liner panels and an exhaust gas duct is defined radially within the arrangement of liner panels. In use, cooling air flows within the cooling air duct and hot exhaust gases flow within the exhaust gas duct.

It is necessary to provide a sealing assembly that seals between adjacent rings of liner panels in order to prevent the mixing between the cooling air flow and the hot exhaust gas flow. Due to the thermal gradient across the sealing assembly it is necessary for it to be able to withstand differential thermal expansion between parts of the sealing assembly, whilst still providing a satisfactory seal. Existing sealing assemblies that achieve this objective comprise a relatively large number of discrete parts and are therefore expensive and time consuming to manufacture and install.

It is therefore desirable to provide a sealing assembly that can withstand differential thermal expansion between components whilst still providing a satisfactory seal.

The present invention is defined in the attached independent claim to which reference should now be made. Further, preferred features may be found in the sub-claims appended thereto.

According to an aspect of the invention there is provided a sealing assembly for providing a seal against a component, comprising: a seal carrier; and a continuous seal element attached to the seal carrier at at least two discrete positions of attachment, the seal element having a sealing surface that is arranged to seal against the component; wherein the seal element is provided with a first thermal expansion slot that is located between the discrete positions of attachment and which extends from a first edge of the seal element over a portion of the width of the seal element so as to allow the seal carrier and seal element to thermally expand in the length direction at different rates. The seal element may be provided with a first thermal expansion slot between each pair of adjacent discrete positions of attachment. The sealing assembly may be arranged to seal between a hotter region and a cooler region and therefore there may be a thermal gradient across the sealing assembly.

The seal element may be further provided with a second thermal expansion slot which is located adjacent to the or each first thermal expansion slot and which extends from a second edge of the seal element over a portion of the width of the seal element. The first and second thermal expansion slots may be spaced from one another (in the length direction) and overlap in the width direction of the seal element.

The first and/or second thermal expansion slots may extend in substantially the width direction of the seal element.

The end of the first and/or second thermal expansion slot located away from the edge of the seal element may have an enlarged width (when compared to the width of the rest of the thermal expansion slot).

The seal element may comprise a seal element flange and the seal carrier may comprise a seal carrier flange to which the seal element flange is attached such that they overlap.

The seal carrier may be provided with a seal carrier thermal expansion slot that is located between the discrete positions of attachment. The seal carrier thermal expansion slot may be provided in the seal carrier flange. The seal carrier thermal expansion slot may extend in substantially the width direction of the seal carrier.

The seal element may be attached to the seal carrier by rivets.

According to a further aspect of the invention there is provided a gas turbine engine comprising: a casing; a liner panel disposed within the casing, wherein a cold flow region is defined between the casing and the liner panel and a hot flow region is defined inside the liner panel; and a sealing assembly in accordance with any statement herein, wherein the seal carrier is attached to the casing and extends across the cold flow region, and wherein the sealing surface of the seal element seals against the liner panel.

According to yet a further aspect of the invention there is provided a sealing assembly for providing a seal between first and second components, comprising: a first sealing assembly comprising a sealing assembly in accordance with any statement herein, wherein the sealing surface of the seal element is arranged to seal against the first component; and a second sealing assembly comprising a sealing assembly in accordance with any statement herein, wherein the sealing surface of the seal element is arranged to seal against the second component. The seal carriers of the first and second sealing assemblies may be coupled to one another such that the seal elements of the first and second sealing assemblies extend in opposing directions. The seal carriers of the first and second sealing assemblies may be integrally formed or attached to one another. The seal carrier of the first and second sealing assemblies may be the same component.

According to another aspect of the invention there is provided a gas turbine engine comprising: a casing; first and second liner panels disposed within the casing and spaced from one another, wherein a cold flow region is defined between the casing and the liner panels and a hot flow region is defined inside the liner panels; and a sealing assembly in accordance with the preceding statement, wherein the seal carriers of the first and second sealing assemblies are attached to the casing and extend across the cold flow region, and wherein the sealing surface of the first sealing assembly seals against the first liner panel and the sealing surface of the second sealing assembly seals against the second liner panel, thereby restricting the flow between the cold flow region and the hot flow region.

The invention also concerns a gas turbine engine comprising a sealing assembly in accordance with any statement herein.

The invention may comprise any combination of the features and/or limitations referred to herein, except combinations of such features as are mutually exclusive.

FIG. 1Ashows a cross-sectional view through the exhaust system of a gas turbine engine1. The exhaust system includes a substantially annular casing2having an annular arrangement of liner panels3disposed therein. The arrangement of liner panels comprises a plurality of rings (or annuluses) of liner panels located axially next to one another with a gap between adjacent rings.FIG. 1only shows first and second axially adjacent liner panels4,6of adjacent rings with a gap5between the first and second panels4,6. Each ring of liner panels may be a continuous annular liner panel or may comprise a plurality of segments of liner panels circumferentially arranged so as to form an annulus.

An annular cooling air duct8is defined between the casing2and the annular arrangement of liner panels3. An exhaust gas duct10is defined radially within the annular arrangement of liner panels3. In use, cooling air flows in direction C within the cooling air duct8and hot exhaust gases flow in direction H within the exhaust gas duct10.

In order to prevent the hot exhaust gases flowing from the exhaust gas duct10, through the gap5between the first and second liner panels4,6and into the cooling air duct8, two sealing assemblies12,14are provided that together seal the gap5between the first and second panels4,6. The sealing assemblies12,14also prevent the flow of cooling air into the exhaust gas duct10. The first sealing assembly12seals against the first liner panel4and the second sealing assembly14seals against the second liner panel6. The first and second sealing assemblies12,14are substantially identical, although they are mirror images of one another, and together form a composite sealing assembly. Although it has been described that the first and second sealing assemblies12,14are formed separately, as will be readily apparent to one skilled in the art, the first and second sealing assemblies may be integrally formed.

In this embodiment the first and second sealing assemblies12,14are annular and seal a circumferentially extending gap5between axially spaced rings of liner panels. References to length are in the circumferential direction and references to width are in the axial direction. Although in this embodiment the seal carrier and seal element extend in the circumferential direction, in other embodiments having Cold and Hot (“C” and “H”) flow paths in the same relative direction to the features of the sealing assembly, the seal carrier and seal element may be linear.

In a further embodiment shown inFIG. 1B, the Cold and Hot (“C” and “H”) flows are in a different direction relative to the features of the sealing assembly to that shownFIG. 1A.FIG. 1Bshows a cross-sectional view looking downstream through the exhaust system of a gas turbine engine101. The exhaust system includes a non circular casing102having a linear arrangement of liner panels103disposed therein. The casing may be polygonal in cross-section. The arrangement of liner panels comprises a plurality of linear liner panels located axially next to one another with a gap between adjacent panels.FIG. 1Bonly shows first and second adjacent liner panels104,106of adjacent panels with a gap5between the first and second panels104,106.

A cooling air duct108is defined between the casing102and the liner panels103. An exhaust gas duct110is defined within the liner panels103. In use, cooling air flows in direction C (i.e. into the plane of the figure) within the cooling air duct108and hot exhaust gases flow in direction H within the exhaust gas duct110(i.e. into the plane of the figure).

In order to prevent the hot exhaust gases flowing from the exhaust gas duct110, through the gap105between the first and second liner panels104,106and into the cooling air duct108, two sealing assemblies112,114are provided that together seal the gap105between the first and second panels104,106. The sealing assemblies112,114also prevent the flow of cooling air into the exhaust gas duct110. The first sealing assembly112seals against the first liner panel104and the second sealing assembly114seals against the second liner panel106. The first and second sealing assemblies112,114are substantially identical, although they are mirror images of one another, and together form a composite sealing assembly. Although it has been described that the first and second sealing assemblies112,114are formed separately, as will be readily apparent to one skilled in the art, the first and second sealing assemblies may be integrally formed.

The first sealing assembly12as presented inFIG. 1Ais shown inFIG. 2Aand comprises a seal carrier16and a seal element18. In this embodiment the seal carrier16and seal element18are manufactured from sheet metal. However, as will be readily apparent to one skilled in the art, other suitable materials may be used. The seal carrier16comprises a radially extending portion20, that is attached to the casing2at its radially outer end by a bolt, and an axially extending portion22that extends from the radially inner end of the radially extending portion20. The radially extending portion20extends radially inwards from the casing2across the cooling air duct8, through the gap5between the first and second liner panels4,6to a position within the exhaust gas duct10. The axially extending portion22of the first sealing assembly12is positioned within the exhaust gas duct10and axially extends towards the first liner panel4. The axially extending portion22of each sealing assembly forms a seal carrier flange to which the seal element18is attached.

The seal element18is elongate in the circumferential direction and comprises a seal element flange24that overlaps the seal carrier flange22and which is attached thereto by a plurality of rivets. The seal element18also comprises a flexible seal portion26that extends towards the first liner panel4and which has a sealing surface28on a radial outer surface thereof. The sealing surface28is in contact with the radial inner surface of the first liner panel4and therefore provides a seal against the first liner panel4.

An alternative embodiment of the first sealing assembly112is shown inFIG. 2B, which corresponds to the arrangement ofFIG. 1B. In most respects this embodiment is exactly as that described in relation toFIG. 2A, other than it refers to a linear, rather than annular, arrangement of liner panels104. The first sealing assembly112comprises a seal carrier116and a seal element118. The seal carrier116comprises a transverse extending portion120, that is attached to the casing102at its outer end by a bolt, and an laterally extending portion122that extends from the free (or “inner”) end of the transverse extending portion120. In this embodiment, the axis of the duct110extends into the plane of the figure. The transverse extending portion120extends inwards from the casing112across the cooling air duct108, through the gap105between the first and second liner panels114,116to a position within the exhaust gas duct110. The laterally extending portion122of the first sealing assembly12is positioned within the exhaust gas duct110and extends towards the first liner panel14. The laterally extending portion122of each sealing assembly forms a seal carrier flange to which the seal element118is attached.

The seal element118is elongate in the lateral direction and comprises a seal element flange124that overlaps the seal carrier flange122and which is attached thereto by a plurality of rivets. The seal element118also comprises a flexible seal portion126that extends towards the first liner panel104and which has a sealing surface128on an outer surface thereof. The sealing surface128is in contact with the inner surface of the first liner panel104and therefore provides a seal against the first liner panel104.

As shown inFIG. 1AandFIG. 1B, the second sealing assembly14,114is a mirror image of the first sealing assembly12,112and is located next to the first sealing assembly12,112. The seal carriers16,116of the first and second sealing assemblies12,112,14,114are attached to the casing2,102at substantially the same position. The radially/transversely extending portion20,120of the second sealing assembly14,114is adjacent to the radially/transversely extending portion20,120of the first sealing assembly and extends radially/transversely inwardly to a position within the exhaust gas duct10,110. The axially/laterally extending portion22,122of the second sealing assembly14,114is positioned within the exhaust gas duct10,110and extends towards the second liner panel6,106. The sealing surface28,128of the second sealing assembly14,114seals against the second liner panel6,106and therefore the composite sealing assembly comprising the first and second sealing assemblies12,112,14,114provides a seal between the first and second adjacent liner panels4,104,6,106and prevents (or at least restricts) flow between the exhaust gas duct10,110and the cooling air duct8,108.

Although it has been described that the first and second sealing assemblies12,112,14,114are separate and each have a respective seal carrier16,116, it is possible that the first and second sealing assemblies12,112,14,114are integrally formed and therefore have a common seal carrier. In other words, the seal carrier16,116of the first sealing assembly12,112may be the same as the seal carrier16,116of the second sealing assembly.

FIG. 3Ashows an enlarged view of the first sealing assembly12, although it should be noted that the second sealing assembly14is substantially identical to the first sealing assembly12. In this embodiment the seal carrier16and seal element18are shown as linear. As previously described with reference toFIG. 1AandFIG. 2Athe seal carrier16and seal element18may be curved to define an annular flow path arrangement. The transversely/radially extending portion20of the seal carrier16is provided with a plurality of apertures (or through-holes)30. In use, this allows cooling air to flow within the cooling air duct8in direction C past the radially extending portions20of the first and second sealing assemblies12,14, by flowing through the apertures30. In this embodiment the air flow directions C,H are across the sealing assembly, i.e. from left to right inFIG. 3A. The seal element flange24is attached to the laterally/axially extending portion22(or seal carrier flange) of the seal carrier16by rivets that are provided at a plurality of discrete positions32.

FIG. 3Bshows an enlarged view of the first sealing assembly112as shown inFIGS. 1B and 2B, although it should be noted that the second sealing assembly114is substantially identical to the first sealing assembly112. In this embodiment the air flow directions C,H are along the sealing assembly, i.e. parallel to the plane of the transversely extending portion120and along the length of the laterally extending portion122. The transversely extending portion120of the seal carrier116is provided with a plurality of apertures (or through-holes)130. In use, this allows cooling air to flow across the transversely extending portions120of the first and second sealing assemblies112,114, by flowing through the apertures130. However, the bulk of the air flow is in the direction indicated by arrows C,H along the sealing assembly. The seal element flange124is attached to the transversely extending portion122(or seal carrier flange) of the seal carrier116by rivets that are provided at a plurality of discrete positions132.

With reference to bothFIG. 3AandFIG. 3B, The seal carrier16,116is also provided with a plurality of seal carrier thermal expansion slots31which are spaced along the length of the seal carrier16,116and extend in the width direction of the seal carrier16,116. A seal carrier thermal expansion slot31is disposed between the discrete positions at which the seal element18,118is attached (by riveting) to the seal carrier16,116. Each seal carrier thermal expansion slot31is continuous and has a first portion31athat is provided in the axially/laterally extending portion22,122and a second portion31bthat is provided in the radially/transversely extending portion20,120. The first portion31aextends though the axially/laterally extending portion22,122of the seal carrier16,116and the second portion partially extends through the radially extending portion20,120of the seal carrier16,116and opens into an aperture30,130. In other words, the seal carrier thermal expansion slot31extends from the free edge of the axially/laterally extending portion22,122and opens into an aperture30,130provided in the radially/transversely extending portion20,120.

The seal element18,118is provided with a plurality of thermal expansion regions, each thermal expansion region being located between adjacent discrete positions at which the seal element18,118is attached to the seal carrier16,116. Each thermal expansion region comprises first and second thermal expansion slots34,36that are adjacent to one another. The first thermal expansion slot34extends from a first edge of the seal element18,118over a portion of the width of the seal element16,116. The second thermal expansion slot36extends from a second opposite edge of the seal element18,118over a portion of the width of the seal element18,118. The first and second thermal expansion slots34,36are located side-by-side in the length direction of the seal element18,118and overlap in the width direction of the seal element18,118. The first and second seal elements34,36overlap in the region where the seal element flange24,124overlaps the seal carrier flange22,122. In this embodiment the first and second seal thermal expansion slots34,36extend in the width direction of the seal element18. The end of each thermal expansion slot34,36is provided with an enlarged portion35,37.

In these embodiments the seal element18,118is attached to the seal carrier16,116at a large number of discrete positions that are spaced along the length of the seal element18,118. It may be attached at a number of positions greater than 5 or 10, for example. In some embodiments it may be attached at a number of positions greater than 20, or 30, for example. The seal element18,118may have a thermal expansion region comprising at least one thermal expansion slot34,36located between pairs of adjacent discrete positions of attachment. A thermal expansion region may be located between every pair of adjacent discrete positions of attachment. There may be greater than 5, 10, 20, 30 or 40 thermal expansion regions.

In use, the radially/transversely extending portion20,120of the seal carrier16,116is exposed to the cooling air flow C within the cooling air duct8,108, whilst the axially/laterally extending portion22,122of the seal carrier18,118is exposed to the hot exhaust gas flow within the exhaust gas duct10,110. An outer surface of the seal element18,118is exposed to the cooling air flowing within the cooling air duct8,108and an inner surface of the seal element18,118is exposed to the hot exhaust gas flow within the exhaust gas duct10,110. This means that the radially/transversely extending portion20,120, the axially extending portion22,122, and the seal element18,118thermally expand at different rates.

The axially/laterally extending portion22,122thermally expands in the length direction by a greater amount than the radially/transversely extending portion20,120due to the difference in temperature that the two portions are exposed to. The seal carrier thermal expansion slots31accommodate for this difference in thermal expansion which mainly occurs in the area underneath the seal element18,118. The hot side of the seal element18,118(the side exposed to the exhaust gas duct10,110) is held at a similar length to the length of the cold side of the seal element18,118(the side exposed to the cooling air duct8,108). This is necessary in order to maintain acceptable stresses because the (cold) radially/transversely extending portion20,120of the seal carrier16,116cannot thermally expand in the length direction as it is fixedly attached to the casing2,102by bolts.

The thermal expansion regions provided in the seal element18,118allows the seal element18,118and axially/laterally extending portion22,122of the seal carrier16,116to thermally expand at different rates in the length direction of the seal element18,118. With reference toFIGS. 4Aand B, in the cold condition the first and second thermal expansion slots34,36are of substantially constant width. When the engine is running and hot exhaust gas flows through the exhaust gas duct10,110the first and second thermal expansion slots34,36deform in order to accommodate for a difference in thermal expansion between the seal carrier16,116and the seal element18,118. The deformation of the thermal expansion slots34,36absorbs the difference in the change in length between the seal element18,118and the seal carrier16,116in the region between the positions at which the seal element18,118is riveted to the seal carrier16,116. The enlarged portions35,37of the first and second thermal expansion slots34,36allow the thermal expansion slots34,36to deform easily. The thermal expansion regions allow the seal element flange24,124to slide over the seal carrier flange22,122in the region in between the rivets (or discrete positions of attachment). This prevents undesirably high induced stresses being generated due to different thermal expansions. If the thermal expansion slots34,36were not present then the seal element18,118would experience stresses which could cause the seal element flange24to buckle and lift away from the seal carrier flange22,122in between the rivets, thereby compromising the integrity of the seal.

Since the first and second thermal expansion slots34,36extend from opposite sides of the seal element18,118and only extend over a portion of the width of the seal element18,118, the seal element18,118can be made as a continuous piece which makes the seal assembly relatively inexpensive to manufacture and relatively easy to install.

Although it has been described that the sealing assembly is for sealing between an annular casing and an annular arrangement of liner panels in a gas turbine engine, and for sealing between a polygonal casing and a linear arrangement of liner panels in a gas turbine engine, the sealing assembly may be used to provide a seal in other applications. The seal assembly is particularly suitable for providing a seal where there is a temperature gradient across the seal, or where the seal carrier and seal element are manufactured from different components and therefore experience different rates of thermal expansion.