Abstract:
A gas turbine ( 10 ) has an annular exhaust gas casing ( 16 ) which is arranged at the outlet of the turbine at a distance from the supporting foundation ( 22 ) and includes an outer shell ( 20   a ). Sagging of the exhaust gas casing ( 16 ) is avoided by supporting devices ( 26, 27, 28 ), each with a predetermined supporting direction, being arranged between the foundation ( 22 ) and the outer shell ( 20   a ) of the exhaust gas casing ( 16 ) for absorbing deformations of the exhaust gas casing ( 16 ), which are fastened by one end on the outer shell ( 20   a ) of the exhaust gas casing ( 16 ) and supported by the other end on the foundation ( 22 ), and by each of the supporting devices ( 26, 27, 28 ) having a pre-loaded spring support ( 30 ) which acts in a supporting direction.

Description:
[0001]    This application claims priority under 35 U.S.C. §119 to U.S. Provisional application No. 61/227,161, filed 21 Jul. 2009, the entirety of which is incorporated by reference herein. 
     
    
     BACKGROUND 
       [0002]    1. Field of Endeavor 
         [0003]    The present invention relates to the field of gas turbine technology, to a gas turbine with an annular exhaust gas casing which is arranged at the outlet of the turbine at a distance from the supporting foundation, and to a method for its production. 
         [0004]    2. Brief Description of the Related Art 
         [0005]    For a long time, large stationary gas turbines have proved successful in power generation in combined cycle power plants or in another environment (see, for example, D. K. Mukherjee, State-of-the-art gas turbines—a brief update, ABB Review 2/1997, p. 4-14 (1997)). One of the gas turbines constructed there, the GT13E2 with an output of 165 MW, is reproduced in  FIG. 1  in a partially sectioned perspective view. 
         [0006]    The gas turbine  10  from  FIG. 1  includes a rotor which is rotatably mounted around a machine axis  49 , with a rotor shaft  17  and blading which, on the one hand, is part of a compressor  11  for the inducted combustion air and, on the other hand, is part of a turbine  14  for expanding the hot gas which is produced. Between compressor  11  and turbine  14  a combustion chamber  13  is arranged, into which an annular arrangement of burners  12  injects a fuel-air mixture for combustion. The combustion chamber  13  and the subsequent turbine  14  are enclosed by an outer casing  15  to which an annular exhaust gas casing  16  is flanged. The exhaust gas casing  16 , which is shown in  FIG. 2  in its details, includes an outer shell  20   a  and an inner shell  20   b  in a concentric arrangement and interconnected by radially oriented struts  21  which are arranged in a distributed manner around the periphery. 
         [0007]    As a stationary turbine, the gas turbine  10  is built on a stable foundation ( 22  in  FIG. 2 ) and in the outlet region is supported on a bearing pedestal  23  by supports (not shown in  FIG. 2 ) which act upon the outer casing  15 . The exhaust gas casing  16  itself is not supported in the prior art. On account of the compactness and the weight of the exhaust gas casing  16 , sagging of the casing can possibly occur, which can lead to decentralizing of the bearing and to rubbing of the rotor blades. There thus remains a need to safely exclude such sagging in the case of such casing configurations. 
       SUMMARY 
       [0008]    One of numerous aspects of the present invention includes a gas turbine which can avoid the aforementioned disadvantages of previous gas turbines and can be characterized by increased stability of the casing in the exhaust gas region, which can also be subsequently brought about in a simple manner in already existing gas turbines, and also methods for producing or installing such gas turbines. 
         [0009]    Another aspect of the present invention relates to absorbing deformations of the exhaust gas casing with supporting devices, with a predetermined supporting direction in each case, which are arranged between the foundation and the outer shell of the exhaust gas casing and are fastened by one end on the outer shell of the exhaust gas casing and supported by the other end on the foundation, so that the supporting devices in each case have a pre-loaded spring support which acts in the supporting direction. 
         [0010]    A further development relates to a plurality of supporting devices provided with different supporting directions which are arranged symmetrically to a vertical center plane which runs through the machine axis. 
         [0011]    Three separate supporting devices are preferably provided, of which the center supporting device lies in the vertical center plane which runs through the machine axis, while the two other supporting devices have supporting directions which, by an angle of between 30° and 40°, preferably of about 36°, are inclined from the vertical center plane which runs through the machine axis. 
         [0012]    In order to absorb thermal expansions it is advantageous in this case if, in the cold state of the gas turbine, the supporting direction of the center supporting device is inclined from the vertical by a few degrees, preferably 6.9°, and the supporting directions of the two other supporting devices are inclined from the radial direction by a few degrees, preferably 6°. 
         [0013]    Another development includes that the supporting devices are pivotably connected by their ends to the outer shell of the exhaust gas casing and to the foundation for absorbing thermal expansions. 
         [0014]    A further development is characterized in that a foundation plate is fastened on the upper side of the foundation, and that a baseplate, which for each of the supporting devices carries a corresponding support block which is matched to the respective supporting direction, is arranged on the foundation plate, and that the supporting devices are pivotably connected to the support blocks. 
         [0015]    In order to pivotably connect the supporting devices to the support blocks, a fork-head jackscrew is especially provided, wherein the fork-head jackscrew is mounted in the support block in a displaceable manner in the supporting direction and supported on the support block via support devices which are adjustable in the supporting direction relative to the fork-head jackscrew. 
         [0016]    Another development includes that the fork-head jackscrews are each provided with a male thread, and the support devices each include a locking ring which, by a corresponding female thread, is screwed onto the fork-head jackscrew. 
         [0017]    Devices for hydraulic pre-loading of the supporting devices are preferably provided in each of the support blocks. 
         [0018]    The hydraulic pre-loading devices especially include access openings in the support blocks into which a hydraulic piston can be inserted for hydraulic displacement of the fork-head jackscrews in the supporting direction. 
         [0019]    According to another development, the spring supports are formed as angulating spring supports. 
         [0020]    A further development includes that, for each of the supporting devices, provision is made for an adapter block which abuts against, and is fastened on, the outer shell of the exhaust gas casing, and the supporting devices are pivotably connected to the adapter blocks. 
         [0021]    An exemplary method embodying principles of the present invention for producing a gas turbine is characterized in that, in a first step, means for fastening the supporting devices are installed on the foundation and on the outer shell of the exhaust gas casing, in that in a second step the supporting devices are connected without pre-loading to the fastening means, in that in a third step the supporting devices are pre-loaded, and in that in a fourth step the supporting devices are fixed in the pre-loaded state. 
         [0022]    In this case, the procedure is preferably carried out so that in the first step the fastening means are fastened by screws on the foundation and on the outer shell of the exhaust gas casing, and so that in the third step the supporting devices are hydraulically pre-loaded by an insertable hydraulic piston. 
         [0023]    In the fourth step, the fixing of the supporting devices in the pre-loaded state is especially carried out by rotating a locking ring which is seated on a thread. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    The invention shall subsequently be explained in more detail based on exemplary embodiments in conjunction with the drawing. In the drawing 
           [0025]      FIG. 1  shows in a partially sectioned perspective view an exemplary gas turbine (GT13E2), as is suitable for the application of the invention; 
           [0026]      FIG. 2  shows the outlet-side part of the gas turbine from  FIG. 1  with the associated foundation and an additional support of the exhaust gas casing according to an exemplary embodiment of the invention; 
           [0027]      FIG. 3  shows an enlarged view of the additional support from  FIG. 2  as seen in the direction of the machine axis; 
           [0028]      FIG. 4  shows, in an enlarged detail from  FIG. 3 , the connection between foundation plate and baseplate of the additional support; 
           [0029]      FIG. 5  shows, in an enlarged detail from  FIG. 3 , the pivotable connection of the right-hand supporting device to the outer shell of the exhaust gas casing; 
           [0030]      FIG. 6  shows, in an enlarged detail from  FIG. 3 , the pivotable and adjustable connection of the center supporting device to the associated support block; 
           [0031]      FIG. 7  shows, in an enlarged detail from  FIG. 3 , the pivotable and adjustable connection of the right-hand supporting device to the associated support block; 
           [0032]      FIG. 8  shows the fork-head jackscrew and the associated locking ring of the center supporting device from  FIG. 3 ; 
           [0033]      FIG. 9  shows the fork-head jackscrew and the associated locking ring of the side supporting devices from  FIG. 3 ; 
           [0034]      FIG. 10  shows the inclination of the supporting devices from the radial direction in the case of the additional support according to  FIG. 2  or  3 ; 
           [0035]      FIG. 11  shows the procedure when pre-loading the center supporting device from  FIG. 3 ; 
           [0036]      FIG. 12  shows the procedure when pre-loading the right-hand supporting device from  FIG. 3 ; and 
           [0037]      FIG. 13  shows, as a variant of  FIG. 10 , the fastening of the adapter block of the supporting device with a plurality of flange clamps. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0038]    In  FIG. 2 , the outlet-side part of the gas turbine from  FIG. 1  with the associated foundation and an additional support of the exhaust gas casing according to an exemplary embodiment of the invention is reproduced. Of the gas turbine  10 , only the outer casing  15 , which encloses the turbine and a part of the combustion chamber, and also the exhaust gas casing  16 , which follows in the direction of flow, are shown for greater clarity. For the exhaust gas casing  16  which in earlier gas turbines is unsupported, provision is now made here for three supporting devices  26 ,  27 , and  28  which act in a specific supporting direction in each case and support the exhaust gas casing  16  against the underlying foundation  22  of the gas turbine  10  and so prevent a noticeable sagging of the heavy casing. 
         [0039]    The three supporting devices  26 ,  27  and  28  preferably lie in each case in a plane which is defined by corresponding radial struts  21  between the inner shell  20   b  and the outer shell  20   a  of the exhaust gas casing  16 . They are arranged and oriented at the same time symmetrically to a vertical center plane which runs through the machine axis  49 . The planes of the side supporting devices  26  and  28  with the center plane include an angle of 36° in each case. The supporting devices  26 ,  27  and  28  in each case establish a supporting direction which is inclined downstream from the radial direction. In the case of the center supporting device  27 , the angle of inclination in the cold state of the machine is preferably 9.6° and at operating temperature increases by 1.7°. In the case of the side supporting devices  26  and  28 , the angle of inclination is preferably 6° and at operating temperature increases by 0.9°. Other machine dimensions in this case require other angles of inclination. 
         [0040]    Each of the supporting devices  26 ,  27 ,  28 , which are of different length for geometric reasons, contain a spring support  30  which acts in the supporting direction and is formed as an angulating spring support. In business, such spring supports are commercially obtainable. A suitable type for example is the type 20-91-14 of the Lisega Company, which can provide up to 100 kN of spring force with a spring constant of 1333 N/mm. In the case of the center supporting device  27 , the spring support  30  can be used directly, in the case of the side supporting devices  26 ,  28  the spring support is used with an extension in each case ( 29  in  FIG. 3  or  38  in  FIG. 12 ). 
         [0041]    The supporting devices  26 ,  27 ,  28  are pivotably connected in the axial direction to associated adapter blocks  40  ( FIGS. 5 ,  10 ) on the exhaust gas casing  16  in order to be able to follow thermal expansions of the exhaust gas casing  16  without any problem. On the foundation side, the supporting devices  26 ,  27 ,  28  are likewise pivotably connected in the axial direction to associated support blocks  31 ,  32 ,  33 . The adapter blocks  40  are arranged on the outer side of the outer shell  20   a  of the exhaust gas casing  16  between the inlet-side flange  19  and an outlet-side flange  18  and fastened by a bolted connection  43 . The adapter blocks are adapted to the curvature of the outer shell  20   a . A fork head  39  ( FIGS. 5 ,  10 ), to which the supporting device  26 ,  27 ,  28  is connected by a hinge bolt  37 , is fastened (for example welded) on each adapter block  40 . 
         [0042]    On the foundation side, the corresponding pivot connections are constructed as follows: a foundation plate  24 , which is formed as a rectangular angle strip, is fastened in the corner which is located downstream between foundation  22  and bearing pedestal  23 . A reinforced baseplate  25  which is fixed on the foundation plate  24  by fixing pins  42  ( FIG. 4 ) lies parallel to the surface of the foundation  22 . Three support blocks  31 ,  32  and  33  are fastened on the baseplate. The support block  32  which is provided for the center supporting device  27  has a horizontal surface. The two support blocks  31  and  33  which are provided for the side supporting devices  26  and  28  have a bevelled surface which is inclined by ±36° and is adapted to the respective supporting direction. 
         [0043]    A bore, which accommodates a fork-head jackscrew  34  or  36  of the type which is shown in  FIG. 8  or  FIG. 9 , is introduced in the support blocks  31 ,  32  and  33  in each case perpendicularly to the upper side. The fork-head jackscrew  34  of the type which is shown in  FIG. 8  is provided for the support block  32  of the center supporting device  27 ; the fork-head jackscrew  36  of the type which is shown in  FIG. 9  is provided for the support blocks  31  and  33  of the side supporting devices  26  or  28 . The fork-head jackscrews  34 ,  36  carry a male thread and at the side have a guide slot  44  which extends in the axial direction and corresponds to a guide pin  41  ( FIGS. 6 ,  7 ) which is inserted in the support blocks  31 ,  32 ,  33  and projects laterally into the bore and guides the fork-head jackscrews  34 ,  36  in a rotation-resisting manner. 
         [0044]    Associated with each of the fork-head jackscrews  34 ,  36  is a locking ring  35  with female thread, which can be screwed onto the fork-head jackscrews  34 ,  36 . Furthermore, the fork-head jackscrews  34 ,  36  at the lower end have a transversely extending recess  45  or  46  with rectangular cross-sectional contour, which serve for accommodating a hydraulic piston ( 48  in  FIGS. 11 ,  12 ). The two recesses  45  and  46  are rotated relative to each other by 90° because, in the case of the center support block  32 , the hydraulic piston  48  is inserted from the front ( FIG. 11 ) while, in the case of the side support blocks  31 ,  33 , it is inserted from the side ( FIG. 12 ). 
         [0045]    The upper end of the fork-head jackscrews  34 ,  36  is formed as a fork head  39  to which are connected the supporting devices  26 ,  27 ,  28  by a hinge bolt  37  ( FIGS. 6 ,  7 ). The fork-head jackscrews  34 ,  36  are displaceably mounted in the supporting direction in the bore in the associated support block  31 ,  32 ,  33  and are supported on the upper side of the respective support block  31 ,  32 ,  33  via the screwed-on locking ring  35  ( FIGS. 6 ,  7 ). 
         [0046]    When installing the supporting devices, as is shown in  FIGS. 11 and 12 , the supporting devices are first of all connected to the adapter blocks  40  and to the fork-head jackscrews  34 ,  36  which are seated in the support blocks  31 ,  32 ,  33 , without pre-loading of the spring support  30 . Then, via access openings  47  or  49  in the support blocks  31 ,  32 ,  33 , a hydraulic piston  48  is inserted into the recesses  45 ,  46  at the lower end of the fork-head jackscrews  34 ,  36 . By highly-pressurizing the hydraulic piston  48  in the supporting direction the fork-head jackscrew  34 ,  36  is partially forced out of the bore and compresses and therefore pre-loads the associated spring support  30  of the supporting device. The pre-loading which is created can be calculated by reading off the hydraulic pressure and multiplying it using the effective hydraulic surface of the hydraulic piston  48 . In the pre-loaded state, the locking ring  35  is then screwed down until it abuts against the upper side of the support block and is subsequently secured by a locking bolt  51 . If the pressure is then removed from the hydraulic piston  48  the pre-loaded supporting device is supported on the support block via the locking ring. In this way, the necessary pre-loading can be individually set for each of the supporting devices  26 ,  27 ,  28 . 
         [0047]    Instead of the bolted connection  43  shown in  FIG. 10 , it is however also possible according to  FIG. 13  to use a plurality of flange clamps  50  to fasten the correspondingly adapted adapter block  40  to the flange  18 . The flange clamps  50  are provided in any case if the exhaust-gas diffuser section which is fitted to the exhaust gas casing  16  at the downstream side is flanged to the flange  18  using such flange clamps. 
         [0048]    The advantages of the invention are multifarious and include:
       At prespecified vital points of the casing, an individual adjustable force which counteracts the sagging can be exerted on the casing.   The force permanently stays in effect thanks to the pre-loaded spring support.   The forces are reliably directed into the foundation.   The pivot connection between casing and foundation on the one hand and the supporting device on the other hand neutralize thermal expansions of the machine.   The construction and installation of the supporting devices is very simple.   The installation can be subsequently undertaken from the outside because dismantling or partial dismantling of the machine is not necessary.   Commercially available components can be used which makes the solution altogether cheaper.       
 
         [0056]    List Of Designations
         10  Gas turbine (for example GT13E2)     11  Compressor     12  Burner     13  Combustion chamber     14  Turbine     15  Outer casing     16  Exhaust gas casing     17  Rotor shaft     18 ,  19  Flange     20   a  Outer shell (exhaust gas casing)     20   b  Inner shell (exhaust gas casing)     21  Strut     22  Foundation     23  Bearing pedestal     24  Foundation plate     25  Baseplate     26 ,  27 ,  28  Supporting device     29 ,  38  Extension (spring support)   Spring support (for example Lisega type 20-19)     31 ,  32 ,  33  Support block     34 ,  36  Fork-head jackscrew     35  Locking ring     37  Hinge bolt     39  Fork head     40  Adapter block     41  Guide pin     42  Fixing pin     43  Bolted connection     44  Guide slot     45 ,  46  Recess     47 ,  49  Access opening     48  Hydraulic piston     49  Machine axis     50  Flange clamp     51  Locking bolt       
 
         [0092]    While the invention has been described in detail with reference to exemplary embodiments thereof, it will be apparent to one skilled in the art that various changes can be made, and equivalents employed, without departing from the scope of the invention. The foregoing description of the preferred embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents. The entirety of each of the aforementioned documents is incorporated by reference herein.