Abstract:
A gas turbine includes a turbine section; an annular combustor disposed upstream of the turbine section and configured to discharge a hot gas flow on an outlet side to the turbine section; an outer shell delimiting the combustor and splittable at a parting plane; a plenum enclosing the outer shell; a rotor; a turbine vane carrier encompassing the rotor; a plurality of stator vanes disposed on the vane carrier, and at least two sealing segments forming a ring, each of the at least two sealing segments having an inner edge and a head and a foot section and being movably mounted on the inner edge by the foot section to the outer shell and by the head section to the turbine vane carrier so as to mechanically connect the combustor to the turbine vane carrier.

Description:
CROSS REFERENCE TO PRIOR APPLICATIONS 
       [0001]    This application is a continuation of International Patent Application No. PCT/EP2009/051518, filed on Feb. 10, 2009, which claims priority to Swiss Application No. CH 00246/08, filed Feb. 20, 2008. The entire disclosure of both applications is incorporated by reference herein. 
     
    
     FIELD 
       [0002]    The present invention relates to the field of thermal machines. 
       BACKGROUND 
       [0003]    Modern industrial gas turbines (IGT) as a rule are designed with annular combustors. In most cases, smaller IGTs are constructed with so-called “can-annular combustors”. In the case of an IGT with annular combustor, the combustion chamber is delimited by the side walls and also by the inlet and outlet planes of the hot gas. Such a gas turbine originates from  FIGS. 1 and 2 . The gas turbine  10  which is shown in detail in  FIGS. 1 and 2  has a turbine casing  11  in which a rotor  12  which rotates around an axis  27  is housed. On the right-hand side, a compressor  17  for compressing combustion air and cooling air is formed on the rotor  12 , and on the left-hand side a turbine  13  is arranged. The compressor  17  compresses air which flows into a plenum  14 . In the plenum, an annular combustor  15  is arranged concentrically to the axis  27  and on the inlet side is closed off by means of a front plate  19  which is cooled with front-plate cooling air  20 , and on the outlet side is in communication via a hot gas passage  25  with the inlet of the turbine  13 . 
         [0004]    Burners  16 , which for example or preferably are designed as premix burners and inject a fuel-air mixture into the combustor  15 , are arranged in a ring in the front plate  19 . Such premix burners originate for example from EP-A1-321 809 or from EP-A1-704 657, wherein these publications and the development which is derived from them form an integrated constituent part of this application. The hot air flow  26  which is formed during the combustion of this fuel-air mixture reaches the turbine  13  through the hot gas passage  25  and is expanded in the turbine, performing work. The combustor  15  with the hot gas passage  25  is enclosed on the outside, with a space, by an outer and inner cooling shroud  21  or  31  which by means of fastening elements  24  are fastened on the combustor  15 ,  25  and between which and the combustor  15 ,  25  an outer and inner cooling passage  22  or  32  is formed. In the cooling passages  22 ,  32 , cooling air, flows in the opposite direction to the hot gas flow  26  along the walls of the combustor  15 ,  25  into a combustor dome  18 , and from there flows into the burners  16 , or as front plate cooling air  20 , flows directly into the combustor  15 . The outer cooling shroud  21 , as shown in  FIG. 3 , can be extended by means of an impingement cooling plate  30  which is provided with holes through which the cooling air jets enter the cooling passage  22  and impinge perpendicularly upon the outer shell  23 . 
         [0005]    The side walls of the combustor  15 ,  25  in this case are constructed either as shell elements or are formed as complete shells (outer shell  23 , inner shell  33 ). When using complete shells, for installation reasons the necessity arises of providing a parting plane ( 34  in  FIG. 4 ) which allows an upper half of the shell  23 ,  33  ( 23   a  in  FIG. 4 ) to be detached from the remaining lower half of the shell ( 23   b  in  FIG. 4 ), for example in order to install or to remove the gas-turbine rotor  12 . The parting plane  34  correspondingly has two parting-plane welded seams which in the example of the gas turbine are located at the level of the machine axis  27  ( FIG. 1 ). 
         [0006]    A flange  28  with an encompassing groove  29  ( FIG. 3 ) is attached at the ends of the shells  23 ,  33  and for reasons of mechanical strength can be reinforced by means of a connecting element in the form of a bridge  37  ( FIG. 4 ) which reaches across the parting plane  34 . 
         [0007]    For the mechanical connection between the annular combustor  15 ,  25  and a subsequent turbine vane carrier TVC (pos.  47  in  FIGS. 8 to 13 ), which carries the stator vanes of the subsequent turbine  13 , and for dividing the plenum  14  into different chambers, sealing segment are provided, which are hooked on the combustor and on the turbine vane carrier in a movable manner and together form a sealing ring, which is arranged concentrically to the axis  27 , between combustor and turbine vane carrier. 
         [0008]    The sealing segments (similar to pos.  35 ′ in  FIG. 4  and to pos.  35  in  FIG. 5 ) should ideally feature the following functions or characteristics:
       They seal two chambers of the plenum.   They should therefore also seal in relation to each other (requiring installation of a sealing lip between adjacent segments).   They mechanically interconnect two construction modules (combustor vs. turbine vane carrier).   They form an intermediate piece/transition piece between two construction modules (combustor vs. turbine vane carrier).   They are axially-symmetrically constructed (with exception of the segments on the parting plane).   They are able to have cooling holes/bores (for a specific mass flow of cooling air).   They should absorb large axial and radial forces.   They should have a large axial and radial movement clearance, especially during transient operations.   They should be resistant to temperature (fatigue strength-creep strength).   They should be simply and inexpensively producible.   They must not rotate in the circumferential direction during operation—this necessitates the installing of circumferential locking means.       
 
         [0020]    The sealing segments are to be installed before inserting the outer shells  23  into the flange  28  which is provided for it, but they could also first be installed in the gas turbine. The sealing segments can have a circumferential locking means. For the circumferential locking means, for example a groove is provided and a locking pin, having already been welded in, is located in the flange  28  of the outer shell  23 . 
         [0021]    The sealing segments can furthermore have a groove or a slot for narrow seals (knife-edge seals) in the side faces (“wedge faces”). During installation, these seals also have to be inserted. The inserting of the seals into the grooves, and additionally the inserting of the sealing segments into the flange which is provided for them, can prove to be exceptionally awkward and is directly dependent upon the geometric design of the sealing-segment foot (pos.  44  in  FIG. 4 ), and also upon the design of the outer-shell flange  28 . The outer shells  23 , which are thermally very severely stressed, move transiently axially and radially; in doing so, high compressive and tensile stresses ensue. 
         [0022]    The sealing segment forms the (mechanical) linking element from the combustor  15 , to the turbine vane carrier  47 , which element moves transiently in a predominantly axial manner. The operating period which is required by the outer shell  23  is typically two so-called service intervals (“service intervals/service cycles”). An operating interval describes the time between the (re-)commissioning of the combustor and the reconditioning of the components. 
       SUMMARY OF THE INVENTION 
       [0023]    It has now become apparent in practice that during operation the outer shells  23  begin to break down, often at the end of the parting-plane welded seams. It is assumed that the breaking down can also be caused by the outer shell, especially during the transient movements, not having adequate clearance and additional mechanical stresses acting upon the outer shell as a result. 
         [0024]    An aspect of the invention is to create a thermal machine, especially a gas turbine, which avoids the aforementioned disadvantages of known machines and absolutely minimizes by constructional measures the risk of breaking down of the welded combustor shells. 
         [0025]    In an embodiment, the sealing segments are mounted so that the combustor or the outer shell can move relative to the turbine vane carrier independently of each other in the axial direction and in the radial direction. 
         [0026]    One development of the gas turbine according to the invention is characterized in that the sealing segments are mounted by the head in a locating space on the turbine vane carrier in such a way that they are radially movable there and pivotable around the head. In particular, the sealing segments can be mounted by the foot on the outer shell of the combustor in such a way that they are pivotable around the foot. 
         [0027]    Another development of the invention is characterized in that the outer shell at the turbine-side end has a flange, in that the flange on the outer side is provided with an encompassing groove, and in that the sealing segments are pivotably mounted by the foot in the groove. The groove preferably has an L-shaped cross-sectional profile with an undercut, wherein the foot is formed in the shape of a hook and fits behind the undercut. 
         [0028]    Furthermore, the foot can advantageously have first means for circumferential locking which especially comprise a locking groove which is provided in the foot, extends in the axial direction, and in which engages a locking pin which is fixed on the flange. 
         [0029]    A further development of the invention is characterized in that the foot has second means for it, which preferably comprise a multiplicity of cooling slots which are arranged in the foot next to each other in the circumferential direction. 
         [0030]    Another development is characterized in that between adjacent sealing segments sealing means are provided for sealing the gaps between the sealing segments. The sealing means preferably comprise sealing grooves in the side faces and knife-edge seals which are inserted in the sealing grooves. 
         [0031]    According to a further development of the invention, the locating space on the turbine vane carrier is formed between the turbine vane carrier and a holding plate which is fastened on the turbine vane carrier (pos.  47  in  FIG. 8 ), wherein the locating space has a rectangular cross section and an opening which extends inwards in the radial direction and through which the sealing segments extend by their head into the locating space, wherein the axial width of the locating space is approximately equal to the width of the head of the sealing segments, and wherein the radial height of the locating space is a multiple of the radial height of the head, and the locating space in the region of the opening is formed so that the sealing segments in the installed state are secured against slipping out of the locating space. Rectangular as used herein means essentially rectangular. In particular, the locating space in the region of the opening has a shoulder, behind which the sealing segments are hooked in by the head. 
         [0032]    The sealing segments preferably have abutment faces on the head which abut against the walls of the locating space and are constructed in a cambered manner. The turbine-side abutment face in this case is advantageously constructed so that it has a straight contact line with the wall of the locating space. In this case, this straight contact line is machined so that it is ensured that the sealing segment can roll upon it as a result. 
         [0033]    Another development is characterized in that bridges which overlap the parting plane are arranged in the groove of the flange for mechanical stabilization of the welded outer shell, and in that the sealing segments which are adjacent to the parting plane have a corresponding recess for adapting to the bridges. 
         [0034]    Furthermore, according to requirement provision can be made for the sealing segments to be equipped with cooling holes, which are arranged in the segment surface, for the passage of cooling air. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0035]    The invention is to be explained in more detail in the following based on exemplary embodiments in conjunction with the drawing. All features which are not essential for the direct understanding of the invention have been omitted. Like elements are provided with the same designations in the various figures. The flow direction of the media is indicated with arrows. In the drawing 
           [0036]      FIG. 1  shows the longitudinal section through a cooled annular combustor of a gas turbine according to the prior art; 
           [0037]      FIG. 2  shows in detail the annular combustor from  FIG. 1  with the cooling shrouds fastened on the outside; 
           [0038]      FIG. 3  shows in longitudinal section the turbine-side end of the outer shell of the combustor from  FIG. 1  with the flange fitted; 
           [0039]      FIG. 4  shows in a detail the halves of an outer shell, which abut against each other in a parting plane, according to  FIG. 3 , with the specially formed sealing segments which are adjacent to the parting plane, according to a preferred exemplary embodiment of the invention; 
           [0040]      FIG. 5  shows in a perspective view a sealing segment, which is similar to  FIG. 4 , which is not adjacent to the parting plane; 
           [0041]      FIG. 6  shows the sealing segment according to  FIG. 4  from another angle of view; 
           [0042]      FIG. 7  shows the sealing segment according to  FIG. 4  as seen from the bottom; and 
           [0043]      FIGS. 8-13  for illustrating the large movement clearance, show in longitudinal section different positions of combustor and turbine vane carrier relative to each other, and the associated position of a sealing segment according to  FIGS. 5-7 . 
       
    
    
     DETAILED DESCRIPTION 
       [0044]    A new-type sealing segment with an additional, widened movement clearance with simultaneous ensuring of adequate mechanical strength and required aerodynamic air-tightness, is disclosed. The sealing segment is constructed so that on the foot of the segment it is locally cooled in a directed manner over the entire circumference of the flange. The mass flow of cooling air in this case in no longer interrupted, not even in the transient extreme positions of the sealing segment. 
         [0045]    As already mentioned above, the new-type sealing segments are characterized by the following constructional details:
       They can be cast   They seal in relation to each other, wherein the installation of a sealing lip is required for this.   They mechanically interconnect two constructional modules (combustor vs. turbine vane carrier).   They form an intermediate piece/transition piece between two constructional modules (combustor vs. turbine vane carrier).   They are axially symmetrically constructed, with exception of the segments on the parting plane.   They are able to have cooling holes (for a specific mass flow of cooling air).   They absorb large axial and radial forces.   They have a large axial and radial movement clearance, especially in the transient ranges.   They are resistant to temperature (fatigue strength-creep strength).   They have circumferential locking means.       
 
         [0056]    The feet of the sealing segments are designed so that these accurately fit into the respective flange geometry, and during operation, despite the thermal deformation of the shells and of the flange, are furthermore able to support the flange and at the same time allow an adequate mass flow of cooling air. 
         [0057]    The head of the sealing segment is constructed so that on the rear side the cambered (convex) face can roll linearly on the turbine vane carrier. The front side, on the other hand, ordinarily sometimes hangs transiently in the retaining plate which in its turn is screwed to the turbine vane carrier. This greatly increased movement clearance, with the same functionality of the sealing segment in its extreme positions, in this case is the center of interest of the present invention. 
         [0058]    The exemplary embodiment which is shown in  FIGS. 4 to 13  refers to the use of the invention in the outer shell of a gas turbine. Uses are shown here which can be applied during various transient states of the gas turbine. The design principles according to the invention, however, naturally also apply to a comparable use in the case of a constructionally new design. 
         [0059]    As already further explained in the above, in the case of a gas turbine with annular combustor  15 ,  25  the combustion chamber is delimited by the side walls  23 ,  33  and also by the inlet and outlet planes of the hot gas ( FIGS. 1 ,  2 ). The combustor side walls in this case are constructed either as shell elements or as complete shells. When using complete shells, for installation reasons the necessity of a parting plane ( 34  in  FIG. 4 ) arises, which allows the upper section (for example the upper half  23   a  of the outer shell  23 ) to be detached, for example in order to install or to remove the gas-turbine rotor  12 . The parting plane  34  correspondingly has two parting-plane welded seams which in the example of a gas turbine are located at the level of the machine axis  27 . The parting-plane flange  28 , especially in the case of these gas turbines, is reinforced with bridges (pos.  37  in  FIG. 4 ) and so the adjacent sealing segments  35 ′ at the level of the bridges  37  must have a corresponding recess. Therefore, there are a greater number of normal sealing segments  35  ( FIGS. 5-7 ) in the circumference, and on the parting plane  34  there are two so-called parting-plane sealing segments  35 ′ which are arranged on the left and on the right of the parting plane  34  ( FIG. 4 ). 
         [0060]    The sealing segments  35 ,  35 ′ according to  FIGS. 4-7  have the form of circular segments which at the lower end have a foot which is formed in the shape of a hook, and at the upper end have a head  38  which is formed in the shape of a hook. Head  38  and foot  44  are connected via a wall which in the upper section extends in a straight line and in the lower section is double-curved. In the region of the upper first curve, cooling holes  42 , which are distributed in the circumferential direction and through which the cooling air can pass, are arranged in the wall. In the region of the lower second curve, a strip which projects to the side is provided, which in specific operating states ( FIG. 10 ) forms a stop. 
         [0061]    The sealing segments  35 ,  35 ′ according to  FIGS. 4-7  have a circumferential locking means. For the circumferential locking means, a locking groove  45  is provided on the underside of the foot  44  (see especially  FIG. 7 ). In the installed state of the sealing segments, a locking pin, which is not shown in the figures and which, having already been welded in, is located in the flange  28  of the outer shell  23 , engages in the locking groove  45  ( FIG. 4 ). 
         [0062]    In the side faces (“wedge faces”), the sealing segments  35 ,  35 ′ have a sealing groove (slot) for narrow seals (knife-edge seals  51 ,  FIG. 4 ). During installation, the knife-edge seals  51  must also be inserted.  FIG. 4  shows the knife-edge seals in the installed state.  FIGS. 5-7  show the sealing grooves  41 , which are made for the knife-edge seals, in the side faces. 
         [0063]    As already further mentioned above, the inserting of the knife-edge seals  51  into the sealing grooves  41 , and additionally the inserting of the sealing segments  35 ,  35 ′ into the flange  28  which is provided for them, can prove to be exceptionally awkward, and it is directly dependent upon the geometric design of the sealing-segment foot  44  ( FIGS. 5-7 ) and also upon the design of the outer-shell flange  28 . The cross-sectional profiles and the geometry of the two parts are evident for example from  FIG. 9 . 
         [0064]    The feet  44  of the sealing segments  35 ,  35 ′ must be designed so that these fit accurately into the respective flange geometry of the flange  28  and during operation, despite the thermal deformation of the shells  23 ,  33  and of the flange  28 , are furthermore “able to support” the flange  28  and consequently the combustor, and allow a mass flow of cooling air. From  FIGS. 8-13 , which refer to different operating states of the gas turbine and are correspondingly characterized by different axial and radial distances B, C and A between combustor  15 ,  25  and turbine vane carrier  47  (B, C), or sealing segment  35 ,  35 ′ and turbine vane carrier  47  (A), the associated positions of the sealing segments  35 ,  35 ′ are apparent. 
         [0065]    In the operating states according to  FIGS. 9 and 10 , the axial distance B between flange  28  and turbine vane carrier  47  is zero, whereas the radial distance A between the head  38  of the sealing segments  35 ,  35 ′ and the top of the locating space  49 , as well as the radial distance C between combustor and turbine vane carrier, are maximum ( FIG. 9 ) or minimum ( FIG. 10 ). In the case of the minimum distance A=0, the sealing segments  35 ,  35 ′ make contact with the head  38  and with the strip  43  ( FIG. 10 ). In the case of the maximum distance A ( FIG. 9 ), the sealing segments  35 ,  35 ′ hang by their hook-shaped head  38  on the shoulder  50  in the locating space  49 . 
         [0066]    In the operating state according to  FIG. 8 , the axial distance is B&gt;0, whereas the radial distance C is slightly reduced compared with  FIG. 9 . The sealing segments  35 ,  35 ′ are slightly tilted to the left, which corresponds to a pivoting around the foot  44 . 
         [0067]    In the operating state according to  FIG. 11 , the axial distance B has been further increased and the radial distance is once again reduced. The sealing segments  35 ,  35 ′ are tilted further to the left until at the top they abut by the head  38  in the locating space  49  and by the straight part of the wall abut against the lower end of the holding plate  48 . 
         [0068]    A further (maximum) tilting according to  FIG. 12  is then possible if at the same time the radial distance C is maximum. 
         [0069]    An average operating state is finally shown in  FIG. 13 , all the distances A, B and C having an average value in this case. 
         [0070]    The head  38  of the sealing segment  35 ,  35 ′ is constructed so that (on the rear side) the cambered (convex) sealing face  39  can roll linearly on the turbine vane carrier  47  ( FIG. 8 ). The front side, specifically the hooking strip  40 , on the other hand ordinarily sometimes “hangs” transiently in the holding plate or retaining plate  48  which in its turn is screwed to the turbine vane carrier  47  ( FIG. 9  and  FIG. 12 ). 
         [0071]    The sealing segment  35 ,  35 ′ in this case is constructed so that on the foot  44  of the segment it is locally cooled in a directed manner over the entire circumference of the flange  28 . The mass flow of cooling air is no longer interrupted, even in transient extreme positions of the sealing segment  35 ,  35 ′ ( FIG. 12 ). This is achieved inter alia by a multiplicity of cooling slots  46  being provided in the foot  44  and distributed in the circumferential direction, and by the foot  44  being delimited on the underside by means of a corrugated surface which leaves room for the cooling air flow between flange  28  and foot  44 . 
       LIST OF DESIGNATIONS 
       [0000]    
       
           10  Gas turbine 
           11  Turbine casing 
           12  Rotor 
           13  Turbine 
           14  Plenum 
           15  Combustor 
           16  Burner (double-cone burner or EV-burner) 
           17  Compressor 
           18  Combustor dome 
           19  Front plate 
           20  Front-plate cooling air 
           21  Outer cooling shroud 
           22  Outer cooling passage 
           23  Outer shell 
           23   a  Upper half of the outer shell 
           23   b  Lower half of the outer shell 
           24  Fastening element 
           25  Hot gas passage 
           26  Hot gas flow 
           27  Axis 
           28  Flange 
           29  Groove (flange) 
           30  Impingement cooling plate 
           31  Inner cooling shroud 
           32  Inner cooling passage 
           33  Inner shell 
           34  Parting plane 
           35 ,  35 ′ Sealing segment 
           36  Recess 
           37  Bridge (connecting element) 
           38  Head (sealing segment), head section 
           39  Sealing face 
           40  Hook-in strip 
           41  Sealing groove 
           42  Cooling hole 
           43  Strip 
           44  Foot (sealing segment), foot section 
           45  Locking groove 
           46  Cooling slot 
           47  Turbine vane carrier 
           48  Holding plate 
           49  Locating space 
           50  Shoulder 
           51  Knife-edge seal 
         A, B, C Distance