Abstract:
A component of a turbine includes a vane, a carrier element and at least four interfaces between the vane and the carrier element. The at least four interfaces are sealed via leaf seals. A method for sealing against leakage between a vane and a carrier element of the above-mentioned turbine component includes sealing the at least four interfaces by way of leaf seals.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is the US National Stage of International Application No. PCT/EP2011/061641, filed Jul. 18, 2011 and claims the benefit thereof. The International Application claims the benefits of European application No. 10171961.5 EP filed Aug. 5, 2010. All of the applications are incorporated by reference herein in their entirety. 
     FIELD OF INVENTION 
     The present invention relates to a component of a turbine. It further relates to a method for sealing against leakage between a vane and a carrier element of a turbine component. 
     BACKGROUND OF INVENTION 
     The air leakage between a turbine vane axial face and the corresponding feature of the carrier ring is required to be limited to a minimum. The turbine vane and carrier rings are subjected to thermal and mechanical loads which induce distortion and relative movement. Therefore, leakage between a turbine vane and the corresponding feature of the carrier ring may occur. 
     Previously, air leakage has been minimised with direct face-to-face contact, but has been prone to an unknown rate of leakage during service. 
     In U.S. Pat. No. 4,815,933 a boltless turbine nozzle and a nozzle support assembly that includes a turbine nozzle mounting flange seated in a nozzle seat forming a part of the nozzle support are disclosed. A pressure actuated pliable seal is affixed to the turbine nozzle adjacent to the nozzle seat in order to provide an air seal across the completed assembly. 
     In EP 1 340 885 A2 a leaf seal support for a gas turbine engine nozzle vane is described. The turbine nozzle assembly includes a plurality of segments joint together to form an outer band and a plurality of segments joined together to form an inner band. At least to one airfoil is positioned between the outer and inner bands. A leaf seal is attached to each inner band segment by at least one pin member and a leaf seal is attached to each outer band segment by at least one pin member. 
     In U.S. Pat. No. 5,118,120 an apparatus for effecting a seal between two structural components of a turbo machine or similar device is disclosed. The apparatus comprises a leaf seal located in the space between the two components. 
     In U.S. Pat. No. 5,797,723 and EP 0 526 058 A1 a turbine seal is disclosed. The turbine seal includes a first arcuate segment defining a flowpath boundary between combustion gases and air and includes a radially outwardly extending rail at one end thereof. A second arcuate segment is disposed coaxially with the first segment for defining a continuation of the flowpath boundary. It has a radially extending face adjoining the rail. A leaf seal bridges the rail and the face for sealing leakage there between. A plurality of pins extended through the leaf seal for providing the mounting to the rail. 
     In EP 1 445 537 A2 an assembly for providing a seal at an aft end of a combustor liner for a gas turbine engine is described. The sealing assembly includes a substantially annular first sealing member positioned between an aft portion of a support member and the liner aft end so as to seat on a designated surface portion of the liner aft end. A substantially annular second sealing member is positioned between the support member aft portion and a turbine nozzle located downstream of the liner aft end so as to seat on a designated surface portion of the support member aft portion. The first and second sealing members are maintained in their respective seating positions as the support member aft portion moves radially or axially with respect to the liner aft end and radially or axially with respect to the turbine nozzle. The first and second sealing members allow for axially and radially movement of the adjacent components. 
     In DE 103 06 915 A1 a sealing arrangement for gas turbines is disclosed. The described sealing member comprises a number of openings through which a fluid can pass the sealing member. 
     In WO 2005/033558 A1 a seal which comprises a first and a second component is disclosed. The seal is applied to a combustion chamber for a gas turbine. It comprises a spring load which provides a seal also in the case of vibrations in the combustion chamber. The seal is further applied to the sealing between adjacent stationary blade platforms in gas turbines. The seal comprises a number of openings for leading a fluid through the seal. 
     U.S. Pat. No. 5,343,694 a gas turbine nozzle including a plurality of nozzle segments having a pair of nozzle vanes supported by inner and outer shroud segments is disclosed. The outer shroud segment includes a generally axially extending platform with a circumferentially extending seal member attached to the upstream end thereof to seal with the combustor liner flange against the leakage there between. Moreover, a radially extending circumferential projection is attached to the downstream end of the platform for providing an engagement surface for a W seal to prevent leakage between the outer rotor casing and the shroud segment. 
     In WO 2009/085949 A1 and US 2009/0169370 A1 a turbine nozzle segment including a band having a plurality of tabs is disclosed. An airfoil extending from the band and a support structure attached to the tabs is described. The support structure has a plurality of biasing structures. 
     In US 2009/0074562 A1 a turbine nozzle guide vane with passages leading from a hollow core to respective seal strip slots to deliver cooling air to abutment faces on each end of the vane is disclosed. 
     In EP 2 180 143 A1 a gas turbine nozzle arrangement is disclosed. It comprises at least one seal strip which is present between a radially outer surface of a carrier ring section and inner surface of an inner platform and comprises openings for allowing cooling fluid to flow through the seal strip. 
     The document EP 1 296 023 A1 discloses a devise for holding strip sealing gaskets on a turbo machine nozzle. 
     The document WO 2009/158554 A2 describes a seal for containment of fluids or gases during high temperature applications. 
     In U.S. Pat. No. 5,118,120 entitled “leaf seal” an apparatus for effecting a seal between two structure components of a turbo machine is taught, comprising a leaf seal located in the space between the two components and a spring which continuously biases the leaf seal into a sealing position against the components regardless of the pressure differential across the leaf seal. 
     SUMMARY OF INVENTION 
     It is a first objective of the present invention to provide a component of a turbine with a reduced leakage between a vane and a carrier element. It is a second objective of the present invention to provide a method for sealing against leakage between a vane and a carrier element of a turbine component. 
     The above objectives are achieved by the features of the independent claim(s). The depending claims define further developments of the invention. 
     The inventive component of a turbine comprises a vane, a carrier element and at least four interfaces between the vane and the carrier element. The at least four interfaces are sealed by means of leaf seals. For example, the component may comprise at least four leaf seals for connecting the vane and the carrier element at the at least four interfaces. Sealing all four interfaces has the advantage, that a leakage between the vane and the carrier element, for example a carrier ring, can effectively be reduced. At the same time the inventive design allows for relative movement between the vane and the carrier element, whilst maintaining a known sealing performance. Preferably, the leaf seals are a sheetmetal leaf seals. 
     The turbine may comprise a carrier ring which comprises the carrier element. Alternatively, the carrier element can be designed as carrier ring. 
     Generally, the leaf seals can be connected to the vane and/or to the carrier element. Advantageously, the leaf seals may be connected to the vane and/or to the carrier element such that a movement between the vane and the carrier element is possible. For example, the turbine may comprise a rotation axis. At least one leaf seal can be connected to the vane and/or to the carrier element such that a movement between the vane and the carrier element in axial direction and/or tangential direction and/or radial direction relative to the rotation axis is possible. Preferably, at least one leaf seal can be connected to the vane and/or to the carrier element by means of at least one location pin. At least one leaf seal can allow for free movement by using location pins, for example with axial and tangential clearance. 
     At least one leaf seal may comprise means for leading a fluid through the seal. For example, at least one leaf seal may comprise at least one opening, preferably a number of openings, for leading a fluid through the seal. The vane may comprise a platform with an underside where the vane is connected to the carrier element and which may possibly be exposed to hot gases. For example, the leakage across one of the seals can be allowed to be a higher value compared with one of the other seals in order to supply cooling air to the underside of the platform of the vane. This allows for cooling the underside of the platform. 
     The turbine can comprise a rotation axis and the vane can comprise a trailing edge, a leading edge, a radially outer platform with a leading edge side and a trailing edge side, and a radially inner platform with a leading edge side and a trailing edge side. A first interface can be located at the leading edge side of the radially outer platform. A second interface can be located at the leading edge side of the radially inner platform. A third interface can be located at the trailing edge side of the radially outer platform. A fourth interface can be located at the trailing edge side of the radially inner platform. These four interfaces can each be sealed by means of a previously described leaf seal. 
     Generally, the turbine can be a gas turbine or a steam turbine. 
     The inventive method for sealing against leakage between a vane and a carrier element of a turbine component regards to a turbine component which comprises at least four interfaces between the vane and the carrier element. The at least four interfaces are sealed by means of leaf seals. The inventive method can be performed by means of the inventive component as previously described. Therefore, the inventive method has the same advantages as the inventive component. 
     Generally, the at least four interfaces may comprise the formerly described first interface and/or second interface and/or third interface and/or fourth interface. 
     Advantageously a fluid is led through the leaf seal, for example through openings of the leaf seal. Advantageously, air, especially cooling air, may be led through the leaf seal. This provides for an effective cooling of the sealed portions, especially of the underside of the platform of the vane. 
     In the context of the present invention the term “leaf seal” is used with the same meaning as the term is used in the cited state of the art documents, for example in U.S. Pat. No. 5,118,120, WO 2009/085949 A1 or US 2009/0169370 A1. The leaf seal may for instants be an apex seal, a seal face, a sealing strip, a lip seal, a gasket, a sealing washer or a seal washer. 
     In the present invention, the term “carrier element” is defined as an element to which the vane is connected. The carrier element may hold the vane in its correct position, for example in a turbine. A vane may typically be connected to at least two carrier elements. The vane may comprise a radially inner platform, an airfoil portion and a radially outer platform. The airfoil portion is located between the two platforms. Preferably, each platform is connected to a carrier element. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features, properties and advantages of the present invention will become clear from the following description of an embodiment in conjunction with the accompanying drawings. All mentioned features are advantageous alone or in any combination with each other. 
         FIG. 1  schematically shows a gas turbine. 
         FIG. 2  schematically shows an inventive component of a turbine in a sectional view. 
         FIG. 3  schematically shows a leaf seal connected to the platform of a vane in a perspective view. 
     
    
    
     DETAILED DESCRIPTION OF INVENTION 
     An embodiment of the present invention will now be described with reference to  FIGS. 1 to 3 . 
       FIG. 1  schematically shows a gas turbine. A gas turbine comprises a rotation axis with a rotor. The rotor comprises a shaft  107 . Along the rotor a suction portion with a casing  109 , a compressor  101 , a combustion portion  151 , a turbine  105  and an exhaust portion with a casing  190  are located. 
     The combustion portion  151  communicates with a hot gas flow channel which may have a circular cross section, for example. The turbine  105  comprises a number of turbine stages. Each turbine stage comprises rings of turbine blades. In flow direction of the hot gas in the hot gas flow channel a ring of turbine guide vanes  117  is followed by a ring of turbine rotor blades  115 . The turbine guide vanes  117  are connected to an inner casing of a stator. The turbine rotor blades  115  are connected to the rotor. The rotor is connected to a generator, for example. 
     During operation of the gas turbine air is sucked and compressed by means of the compressor  101 . The compressed air is led to the combustion portion  151  and is mixed with fuel. The mixture of air and fuel is then combusted. The resulting hot combustion gas flows through a hot gas flow channel to the turbine guide vanes  117  and the turbine rotor blades  115  and actuates the rotor. The rotation axis of the turbine is designated by reference numeral  102 . 
       FIG. 2  schematically shows part of a turbine in a sectional view. The axial direction is designated by reference numeral  50 , the radial direction is designated by reference numeral  51  and the tangential direction is designated by reference numeral  52 . In  FIG. 2  a vane  117  is connected to a number of carrier elements  6 ,  7 ,  8 ,  9 . The vane  117  comprises a leading edge  4  and a trailing edge  5 . The flow direction of the driving medium, for example gas or steam is indicated by an arrow  1 . 
     The vane  117  comprises a radially outer platform  2  and a radially inner platform  3 . The radially outer platform  2  comprises a leading edge side  45  corresponding to the leading edge  4  of the vane  117  and a trailing edge side  47  corresponding to the trailing edge  5  of the vane  117 . The radially inner platform  3  comprises a leading edge side  46  corresponding to the leading edge  4  of the vane  117  and a trailing edge side  48  corresponding to the trailing edge  5  of the vane  117 . By connecting the vane  117  to a number of carrier elements  6 ,  7 ,  8 ,  9  a number of interfaces between the vane  117  and the carrier element  6 ,  7 ,  8 ,  9  are established. 
     The radially outer platform  2  comprises a first protrusion  41  which is located at the leading edge side  45  of the radially outer platform  2  and a second protrusion  43  which is located at the trailing edge side  47  of the radially outer platform  2 . The radially inner platform  3  comprises a first protrusion  42  at the leading edge side  46  and a second protrusion  44  at the trailing edge side  48 . 
     A first interface is formed between a radially outer surface  31  of the first protrusion  41  of the radially outer platform  2  and a corresponding surface  21  of the carrier element  7 . This first interface is sealed by means of a first leaf seal  11 . 
     A second interface is formed between a radially inner surface  32  of the first protrusion  42  of the radially inner platform  3  and a corresponding surface  22  of the carrier element  9 . This second interface is sealed by means of a second leaf seal  12 . 
     A third interface is formed by a radially outer surface  33  of the second protrusion  43  of the radially outer platform  2  and a corresponding surface  23  of the carrier element  6 . This third interface is sealed by means of a third leaf seal  13 . 
     A fourth interface is formed between a radially inner surface  34  of the second protrusion  44  of the radially inner platform  3  and a corresponding surface  24  of the carrier element  8 . This fourth interface is sealed by means of a fourth leaf seal  14 . 
     The first leaf seal  11  can be connected to the carrier element  7  and/or to the radially outer platform  2 , preferably to the first protrusion  41  of the radially outer platform  2 , by means of retaining pins  15 . The second leaf seal  12  can be connected to the carrier element  9  and/or to the radially inner platform  3 , preferably to the first protrusion  42  of the radially inner platform  3 , by means of retaining pins  15 . The third leaf seal  13  can be connected to the carrier element  6  and/or to the radially outer platform  2 , preferably to the second protrusion  43  of the radially outer platform  2 , by means of retaining pins  15 . The fourth leaf seal  14  can be connected to the carrier element  8  and/or to the radially inner platform  3 , for example to the second protrusion  44  of the radially inner platform  3 , by means of retaining pins  15 . 
     All leaf seals  11 ,  12 ,  13 ,  14  can advantageously be sheetmetal leaf seals. Preferably, the retaining pins or location pins  15  which are used for connecting the leaf seals  11 ,  12 ,  13 ,  14  to the platforms  2 ,  3  and/or to the carrier elements  6 ,  7 ,  8 ,  9 , are constructed such that a free movement between the platforms  2 ,  3  and the carrier elements  6 ,  7 ,  8 ,  9  is possible. Preferably, location pins with axial and tangential clearance are used. Retaining pins or location pins  15  allow for relative movement between the vane  117  and the corresponding carrier elements  6 ,  7 ,  8 ,  9 , whilst the sealing performance is maintained. 
     Generally, the carrier elements  6 ,  7 ,  8 ,  9  can be part of carrier rings. For example, the carrier element  6  and/or the carrier element  7  can be part of a radially outer carrier ring. The carrier element  8  and/or the carrier element  9  can be part of a radially inner carrier ring. 
     Radially outside of the radially outer platform  2  a space  10  is formed under the radially outer platform  2 . Radially inside of the radially inner platform  3  a space  20  is formed under the radially inner platform  3 . The leaf seals  11 ,  12 ,  13 ,  14  effectively prevent a leakage of hot gases from a combustion chamber of the gas or steam turbine into the spaces  10  and  20  under the platforms  2  and  3 . At the same time a movement between the vane  117  and the carrier element  6 ,  7 ,  8 ,  9 , for example due to vibrations, is possible, whilst the sealing function of the leaf seals  11 ,  12 ,  13 ,  14  is maintained. 
       FIG. 3  schematically shows a leaf seal connected to a platform of a vane in a perspective view. In  FIG. 3  the trailing edge side  48  of the radially inner platform  3  is shown as an example. The leaf seal  14  is connected to the second protrusion  14  of the radially inner platform  3  by means of retaining pins or location pins  15 . 
     Additionally, a number of openings  17  are shown, which are located in an impingement plate  18  at the underside of the platform  3 . These openings  17  can be used for cooling the underside of the platform  3  and/or for cooling vane  117 . 
     The leaf seal  14  further comprises a number of openings  16 . These openings  16  preferably have a smaller diameter than the openings  17  in the impingement plate at the underside of the platform  3 . The openings  16  of the leaf seal  14  can be used for supplying cooling air or any other cooling medium to the underside of the platform  3 . Preferably, the leakage across one of the seals  11 ,  12 ,  13 ,  14  can be allowed to be of a higher value in order to supply cooling air to the underside of the platform  3 . 
     The arrangement shown in  FIG. 3  has the advantage that a sealing against leakage of hot combustion gasses is provided, whilst at the same time a cooling of the underside of the platform  3  can be performed. 
     The other three leaf seals  11 ,  12 ,  13  can be constructed and connected in the same way as shown in  FIG. 3 .