Patent Publication Number: US-9835055-B2

Title: Pullable drawer for a turbine and turbine with such a drawer

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to European application 14160808.3 filed Mar. 20, 2014, the contents of which are hereby incorporated in its entirety. 
     TECHNICAL FIELD 
     The present invention relates to turbines, especially gas turbines. It refers to a pullable drawer according to the preamble of claim  1 . It further refers to a gas turbine with such a pullable drawer. 
     BACKGROUND 
     Gas turbines, especially of the stationary or industrial type, usually have an outer housing, which coaxially extends along a machine axis and surrounds a concentric inner carrier, which carries the vanes of the turbine. The outer housing and the inner carrier are separate units, each comprising an upper part and a lower part, both having the form of a half cylinder, which are connected by means of a flanged connection at a common parting plane. 
     For positioning the inner carrier relative to the outer housing a mechanical connection is established between both parts by means of a plurality of drawers, which extend at certain places through the outer housing to make mechanical contact with the inner carrier. 
     Document U.S. Pat. No. 3,628,884 A discloses a rotary machine, such as a turbine. The machine comprises a tubular outer casing and a tubular inner casing disposed within the outer casing. The inner casing encompasses a rotating rotor structure. 
     Hot motive gases, derived from fuel combustion, are expanded as they flow through the machine to drive the rotor structure, as well known in the art. 
     A plurality of apertures is radially disposed in the outer casing and a plurality of corresponding key slots is disposed on the periphery of the inner casing. After the outer and inner casings are aligned concentrically relative to the axis of rotation of the rotor, a plurality of eccentric bushing structures are radially disposed in the apertures and adjusted to fit the slots to support the inner casing concentrically relative to the axis of rotation of the rotor. 
     Document U.S. Pat. No. 6,224,332 B1 discloses a turbine having an outer structural shell and an inner shell supported by the outer shell. The inner shell carries an array of nozzles and forming parts of first and second stages, respectively, of the turbine. 
     To connect the inner and outer shells to one another, each of the forward and aft portions of the inner shell are provided with circumferentially spaced recesses. Support pins pass through access openings through the outer shell for connection with the forward portion of the inner shell. Similar pins interconnect the outer shell with the all portion of the inner shell. Preferably, the pins lie at eight pin locations in each radial plane and are spaced approximately 45° one from the other about the rotor axis. The support pins are also spaced from the horizontal split line of the inner shell. The support pins include an enlarged head having a bolt circle with a plurality of bolt openings, a cylindrical shank and end projections. The support pins support the inner shell from the outer shell for radial and axial expansion and contraction, with the pins carrying only circumferential loadings. 
     Document US 2009/0226313 A1 discloses a turbine casing structure having an outer casing, and an inner casing disposed in the outer casing, comprising a bush disposed in a concave portion formed in the inner casing; an eccentric shaft inserted into a communication hole formed in the outer casing, and having a front end disposed in contact with the bush; and a fixing member disposed in engagement with the eccentric shaft, and fixed to the outer casing. 
     Document US 2013/0017082 A1 describes an alignment assembly for mounting and aligning an inner shell within an outer shell. The alignment assembly generally includes a first bushing and a second bushing configured to be received within at least one of an arm extending radially between the inner and outer shells and a boss of the outer shell. The first bushing may generally have an eccentric configuration and the second bushing may include an eccentric portion extending within the first bushing. Additionally, the alignment assembly may include a connection member extending within at least one of said first bushing and said second bushing. 
     Other assemblies of inner vane carriers and outer housings or casings of turbine are known from documents DE 25 32 537 A1 and DE 42 30 235 A1. 
     The known solutions have some severe disadvantages:
         Due to a lack of mechanical decoupling, requirements on machining precision are very high in order to avoid an unwanted force impact on sensitive portions of the pullable drawers;   Although designs of pullable drawers accessible from outside do exist, these existing designs show often problems due to unwanted force impact on sensitive portions of the drawer.       

     SUMMARY 
     It is an object of the present invention to provide pullable drawers for turbine housing assemblies, which avoid the disadvantages of the known designs and are easily assembled and disassembled in a very fast and failure-proof way. 
     It is another object of the invention to provide a gas turbine with such a pullable drawer. 
     These and other objects are obtained by a pullable drawer according to claim  1  and a gas turbine according to claim  11 . 
     The pullable drawer according to the invention is provided for removably protruding in a radial direction into an outer housing of a turbine, especially gas turbine, in order to make mechanical contact with an inner carrier being concentrically arranged within said outer housing, whereby said pullable drawer has an essentially cylindrical body, which extends along a longitudinal drawer axis. 
     It is characterized in that said pullable drawer is divided along said longitudinal drawer axis into at least separate first and second parts, which first and second parts are coupled with each other by means of a releasable mechanical joint. 
     According to an embodiment of the pullable drawer of the invention said mechanical joint has at least one degree of freedom for the movement of said first and second parts relative to each other. 
     According to another embodiment of the pullable drawer of the invention said at least one degree of freedom is along a second axis perpendicular to said longitudinal drawer axis. 
     According to another embodiment of the pullable drawer of the invention said mechanical joint is a dovetail joint having a dovetail joint axis, and said dovetail joint axis is identical with said second axis. 
     According to a further embodiment of the pullable drawer of the invention said dovetail joint comprises a pin and a dovetail for receiving said pin in a sliding movement along said dovetail joint axis, said pin is provided at said first part of said pullable drawer, and said dovetail is provided at said second part of said pullable drawer. 
     According to another embodiment of the pullable drawer of the invention a spring is arranged within said dovetail joint between said pin and said dovetail in order to exert a separating force in axial direction between said first and second parts of said pullable drawer. 
     According to just another embodiment of the pullable drawer of the invention said spring is a leave spring, and a spring groove extending along said dovetail joint axis for receiving said leave spring is provided at the front face of the pin of the dovetail joint. 
     According to a further embodiment of the pullable drawer of the invention the leave spring comprises means for laterally fixing said leave spring in said spring groove. 
     According to another embodiment of the pullable drawer of the invention said fixing means comprises a vertical pin, which fits into a hole at the bottom of said spring groove. 
     According to just another embodiment of the pullable drawer of the invention said first part of said pullable drawer comprises a flat head the plane of which is oriented perpendicular to said dovetail joint axis. 
     The gas turbine according to the invention comprises a hollow cylindrical outer housing, which is coaxial with and extends along, a machine axis, and which is divided at a parting plane into an upper part and a lower part, and further comprises an inner carrier, which is concentrically surrounded by said outer housing, and which is divided at said parting plane into an upper part and a lower part, whereby said outer housing and said inner carrier are mechanically coupled by a plurality of pullable drawers, which extend through said outer housing to contact said inner carrier. 
     It is characterized in that said pullable drawers are drawers according to the invention. 
     According to an embodiment of the inventive gas turbine said pullable drawers are arranged pair wise and symmetrically with regard to said parting plane. 
     According to another embodiment of the inventive gas turbine said upper part and lower part of said outer housing are connected in said parting plane by means of a flanged connection, and said pairs of pullable drawers are each arranged within said flanged connection. 
     According to just another embodiment of the inventive gas turbine said upper part and lower part of said inner carrier are connected in said parting plane by means of a flanged connection, and said pairs of pullable drawers have mechanical contact with said inner carrier at said flanged connection. 
     According to a further embodiment of the inventive gas turbine radially extending holding blocks are provided at said flanged connection of said inner carrier, and each pair of pullable drawers makes mechanical contact with a respective holding block at opposite sides of said holding block. 
     According to another embodiment of the inventive gas turbine said pullable drawers are retained within said flanged connection by means of covers mounted on the outside of said flanged connection. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is now to be explained more closely by means of different embodiments and with reference to the attached drawings. 
         FIG. 1  shows part of a gas turbine assembly according to an embodiment of the invention with an outer housing and an inner carrier ( FIG. 1( a ) ), and an enlarged detail of the flanged connections of the outer housing comprising pullable drawers according to an embodiment of the invention ( FIG. 1( b ) ); 
         FIG. 2  shows the inner carrier of  FIG. 1  and the mechanical contact with the pairs of pullable drawers ( FIG. 2( a ) ), and one side of the inner casing with one pair of pullable drawers in an enlarged detail ( FIG. 2( b ) ); 
         FIG. 3  shows a pullable drawer according to an embodiment of the invention, which is used in the assemblies of  FIGS. 1 and 2 ; 
         FIG. 4  shows in detail the enclosure of a pair of pullable drawers in the flanged connection of the outer housing; 
         FIG. 5  is a photograph of the assembled pullable drawer of  FIG. 3  in comparison with a writing pen; 
         FIG. 6  is a photograph of the disassembled pullable drawer of  FIG. 5  in comparison with a writing pen; and 
         FIG. 7  is a photograph of an enlarged detail of the disassembled pullable drawer of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows part of a gas turbine assembly according to an embodiment of the invention. The assembly of gas turbine  10  of  FIG. 1( a )  comprises a section of a hollow cylindrical outer housing  11 , which is coaxial with and extends along, a machine axis A (the axis of rotation of a rotor not shown). The outer housing  11  is divided at a parting plane  13 , which contains the machine axis A, into an upper part  11   a  and a lower part  11   b . Gas turbine  10  further comprises an inner carrier  12 , which is provided for carrying a plurality of vanes, which are mounted in respective circumferential vane receiving grooves  14  and extend radially into the interior of inner carrier  12 . Inner carrier  12  is concentrically surrounded by outer housing  11 , and is divided at said parting plane  13  into an upper part  12   a  and a lower part  12   b.    
     Upper part  11   a  and lower part  11   b  of outer housing  11  are connected in parting plane  13  by means of a first flanged connection  16 . Upper part  12   a  and lower part  12   b  of inner carrier  12  are connected in parting plane  13  by means of a second flanged connection  15 . Outer housing  11  and inner carrier  12  are mechanically coupled by a plurality of pullable drawers  18 , which extend through outer housing  11  to make mechanical contact with inner carrier  12 . Only one pair of pullable drawers  18  is shown in  FIG. 1( a )  and the enlarged detail of  FIG. 1( b ) . 
       FIG. 2  shows the inner carrier  12  of  FIG. 1  and its mechanical contact with the two pairs of pullable drawers  18   a,b  and  18   c,d  ( FIG. 2( a ) ), and one side of the inner casing with one pair of pullable drawers  18   a,b  in an enlarged detail ( FIG. 2( b ) ). Pullable drawers  18   a,b  and  18   c,d  are mounted with a rear (cylindrical) part ( 33  in  FIGS. 3 and 5-7 ) in respective bores in the flanged connection  16  of the outer housing (see  FIG. 1 ) and make contact on opposite sides of a holding block  34 , which is part of flanged connection  15  of inner carrier  12 , by means of a head portion ( 32  in  FIGS. 3 and 5-7 ). Mounted pullable drawers  18  are—as shown in  FIG. 4 —enclosed in their bores in flanged connection  16  by means of covers  19   a  and  19   b , which are each bolted to flanged connection  16  by four screws  20  extending through respective screw holes  21  (see  FIG. 3 ). 
     The technical problems that had to be solved are:
         A mechanical decoupling of independent portions of a pullable drawer;   temperatures up to 500° C. must be tolerated;   ambient fluid pressure up to 30 bar must be tolerated;   a suppression of probable vibrations should be possible;   the drawer should be maintenance friendly, have few parts, be of robust design, and be failure-proof.       

     The basic idea of the invention is now a mechanical decoupling of the pullable drawers  18   a - d , which protrude into the outer housing  11  of gas turbine  10 . At the same time a suppression of vibrations may take place within the drawers. 
     According to the present invention and shown in  FIGS. 3 and 5-7  pullable drawer  18  or  18   a - d  is divided along its longitudinal drawer axis A 1  into at least separate first and second parts  32 ,  33 , namely a head portion  32  and a rear part  33 , which first and second parts  32 ,  33  are coupled with each other by means of a releasable mechanical joint  24 . According to the embodiment shown in  FIGS. 3 and 5-7  the mechanical joint  24  has at least one degree of freedom for the movement of said first and second parts  32 ,  33  relative to each other. In the embodiment shown this at least one degree of freedom is along a second axis A 2  perpendicular to said longitudinal drawer axis A 1  (see  FIG. 3 ). 
     In the embodiment shown, said mechanical joint is a dovetail joint  24  having a dovetail joint axis, which is identical with said second axis A 2 . Dovetail joint  24  comprises on one hand a pin  24   a  and on the other hand a dovetail  24   b  for receiving said pin  24   a  in a sliding movement along said dovetail joint axis A 2 . Pin  24   a  is formed at said first part or head portion  32  of pullable drawer  18 , while dovetail  24   b  is formed at said second or rear part  33  of pullable drawer  18 . 
     To have a tight fit of dovetail joint  24  at the same time successfully suppress unwanted vibration, a spring  25  is arranged within dovetail joint  24  between pin  24   a  and dovetail  24   b . Spring  25  exerts a separating force in axial direction between first and second parts  32 ,  33  of pullable drawer  18 . Spring  25  is a leave spring comprising a stack of separate identical leaves. A spring groove  30  extending along dovetail joint axis A 2  for receiving leave spring  25  is provided at the front face of pin  24   a  of dovetail joint  24 . Leave spring  25  is laterally fixed in spring groove  30  by fixing means  29  in form of a vertical pin  29 , which fits into a hole  31  at the bottom of spring groove  30 . 
     At the end of rear part  33  of pullable drawer  18   a  shoulder  26  is provided, which fits into a respective diameter step of the bore, which receives the drawer in order to have a defined axial position of drawer  18  within flanged connection  16 . Drawer  18  is fixed in this position by cover  19  or  19   a, b , respectively. 
     Head portion  32  of drawer  18  comprises a flat head  22  the plane of which is oriented perpendicular to dovetail joint axis A 2 . With flat head  22  drawer  18  abuts against holding block  34  of flange connection  15  of inner carrier  12 , thereby fixing inner carrier  12  in circumferential direction. A circular recess  23  in flat head  22  may be used to fix inner carrier  12  in a radial direction. 
     As can be seen in  FIG. 6 , dovetail joint  24   a,b  may be provided with bores  27  and  28  in order to fix the joint by a bolt extending through these bores. 
     The drawer according to the invention thus comprises three portions: 
     Portion 1: 
     The rear part  33  of the pullable drawer  18 , which represents a carrier of the head portion  32  of pullable drawer  18 . Its purpose is to keep the head portion  32  in place axially, without suppressing a degree of freedom in the movement. This function is called “mechanical decoupling”. 
     Portion 2: 
     The head portion  32  of pullable drawer  18 . Its purpose is to fulfil the actual function of the feature. In the embodiment shown in the Figures it has to define a certain position for inner carrier  12  relative to the outer housing  11  of the gas turbine  10 . 
     Portion 3: 
     Since the mechanical decoupling allows a certain movement in all degrees of freedom, unwanted vibrations are likely. The movement is suppressed by leave spring  25 , which is also part of the solution. 
     The advantages of the present invention are:
         Problems with rigid drawers with unwanted force impact are solved;   assembly and disassembly is easy, very fast and failure proof, which is very important for such a feature;   the pullable drawer of this invention is the first feature, which combines support drawers and accessibility from outside without time-consuming removing of burners, pipes etc., like it&#39;s done today to remove pullable drawers.       

     However, the invention is not limited to those drawers of the embodiment shown. Any item, which protrudes into the gas turbine and has to carry forces within a certain scope and shall be pullable from outside, could be equipped with such a mechanical decoupling.