Patent Publication Number: US-2009226313-A1

Title: Turbine casing structure

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to the turbine casing structure of a turbine, such as a gas turbine or a steam turbine. 
     2. Description of the Related Art 
     With a turbine such as an industrial gas turbine or steam turbine of a large size, its interior is at a high temperature. Thus, a temperature difference between its interior and its exterior exerts a great influence. As a result, thermal deformation of the stationary portion occurs, causing oval deformation, etc. and thus necessitating a larger gap between the stationary side (stationary blades assembled to an inner casing to be described later) and the rotating side (moving blades assembled to a rotor). To diminish the thermal influence, use is made of a structure of a turbine casing in whose interior a casing (inner casing) is further provided (namely, a double-casing structure). This structure has a single air layer provided between a gas channel portion, through which a high temperature gas flows, and the air outside the turbine casing. 
     The inner casing has a structure supporting the blades on the stationary side, and the inner casing is supported by and fixed to an outer casing. 
     An example of a turbine having such a structure is a turbine having a turbine casing structure  30  as shown in  FIG. 10 . With the turbine casing structure  30 , supporting and positioning (alignment adjustment) of an inner casing (blade ring)  32  with respect to an outer casing  31  are performed by torque pins  33  in a right-and-left direction (lateral direction), and by horizontal keys  34  in an up-and-down direction (vertical direction), respectively, when viewed from the upstream side of the turbine. As shown in  FIG. 11 , the horizontal key  34  is fixed to a parting surface  32   b  of a lower-half inner casing  32   a  by a bolt  35 , and has a front end portion  34   a  installed between an upper liner  36  and a lower liner  37  provided in the vicinity of a parting surface  31   a  of the outer casing  31 . 
     Another example of a turbine having the aforementioned double-casing structure is a turbine having a positioning mechanism for a turbine casing as described in Japanese Patent Application Laid-Open No. 2004-162536 (hereinafter referred to as Patent Document 1). With this turbine casing positioning mechanism, an eccentric pin is inserted into an adjusting hole formed in an engine casing (outer casing) A trunk portion of the eccentric pin is disposed in the adjusting hole, while a front end portion of the eccentric pin eccentric with respect to the trunk portion is disposed in an adjusting groove formed in the turbine casing (inner casing) while extending in an axial direction. A parallel pin is mounted to whirl-stop the eccentric pin with respect to the adjusting hole, and the eccentric pin is fixed to the engine casing by a cover body disposed in contact with the head of the eccentric pin. 
     Japanese Patent Application Laid-Open No. 2001-107922 (hereinafter referred to as Patent Document 2) discloses a flangeless casing fastening structure for fastening upper and lower casings. With the flangeless casing fastening structure, bolt holes are formed in the upper and lower casings, and a cylindrical sleeve is mounted by screwing an outside screw, which is formed in an outer periphery thereof, into a tapped hole provided in the vicinity of a joining surface at the bolt hole of the upper casing. A large-diameter portion to be joined to an upper end surface of the sleeve when a bolt is fastened into the bolt hole of the lower casing is formed in the bolt, and the bolts are inserted into the bolt holes to fix the upper and lower casings. 
     Japanese Patent Application Laid-Open No. 1997-112204 (Patent Document 3) discloses an upper-lower bolt tightening structure for coupling type 180°-divided stationary blades which fixes a stationary blade ring to a turbine casing. With the upper-lower bolt tightening structure for coupling type 180°-divided stationary blades, upper and lower stationary blades are integrated by bolts with holes, and keys fixed in the holes of the bolts with the holes are disposed between upper and lower liners provided in the turbine casing to fix the stationary blade ring to the turbine casing. 
     With the aforementioned turbine casing structure  30 , an improvement in the accuracy of setting a clearance between the rotating side and the stationary side has been desired in recent years from the aspects of improved performance and reliability. Thus, after the inner casing  32  is mounted in the outer casing  31 , the clearance between the inner casing  32  and the outer casing  31  is measured. If the measured value is not within the tolerance of the design value, the inner casing  32  is taken out of the outer casing  31 , and the horizontal keys  34  are machined to optimize the clearance. Using the machined horizontal keys  34 , the inner casing  32  is assembled again into the outer casing  31 . With the conventional turbine casing structure  30 , therefore, the position in the up-and-down direction (vertical direction) of the inner casing  32  with respect to the outer casing  31  cannot be adjusted from the outside. This poses the problem of impairing the efficiency of an adjusting operation, thereby increasing the cost of the operation. 
     With the turbine casing positioning mechanism described in Patent Document 1, the positioning mechanisms are disposed at upper and lower portions of the engine casing and the turbine casing, whereby the position in the right-and-left direction of the turbine casing with respect to the engine casing is restrained by the upper portion and the lower portion thereof. Thus, even if the turbine casing is thermally expanded, its central position is not displaced in the right-and-left direction with respect to the engine casing, and the concentric relationship between the engine casing and the turbine casing can be maintained. Even with the use of this positioning mechanism, however, the position in the up-and-down direction of the turbine casing with respect to the engine casing cannot be adjusted. Even if the positioning mechanisms are disposed in the vicinity of the parting surfaces of the engine casing and the turbine casing, the position in the up-and-down direction of the turbine casing with respect to the engine casing cannot be adjusted. With the turbine casing positioning mechanism, therefore, like the turbine casing structure  30 , the optimal adjustment of the clearance between the engine casing and the turbine casing requires that the turbine casing be taken out of the engine casing, and the positioning mechanism and the positioning mechanism for the vertical position be machined for adjustment. This poses the problem that the position in the up-and-down direction of the turbine casing with respect to the engine casing cannot be adjusted from the outside. 
     With the flangeless casing fastening structure described in Patent Document 2, the inner casings or the outer casings divided into upper and lower portions can be coupled. However, the problem arises that the position in the up-and-down direction of the inner casing with respect to the outer casing cannot be adjusted from the outside. 
     With the upper-lower bolt tightening structure for coupling type 180°-divided stationary blades described in Patent Document 3, the keys fixed to the hole-formed bolts coupling the upper-half and lower-half stationary blades are disposed between the upper and lower liners provided in the turbine casing. By so doing, the inner casing can be locked at a predetermined position with respect to the outer casing. However, the adjustment of the position in the up-and-down direction of the inner casing with respect to the outer casing requires machining of the keys. This presents the problem that the position in the up-and-down direction of the inner casing with respect to the outer casing cannot be adjusted from the outside. 
     The present invention has been accomplished in light of the above-described problems. It is an object of the invention to provide a turbine casing structure in which the position in the up-and-down direction of the inner casing with respect to the outer casing can be adjusted from the outside. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention is 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. 
     An example of the eccentric shaft is a shaft having a shaft center on the front end side thereof and a shaft center on the head side thereof eccentric with respect to each other. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
         FIG. 1  is a schematic sectional view of a turbine having a turbine casing structure according to a first embodiment of the present invention applied thereto; 
         FIG. 2  is an enlarged view of a portion enclosed with a line II in  FIG. 1 ; 
         FIG. 3  is a view taken on line III-III in  FIG. 2 ; 
         FIG. 4  is a view taken along line IV in  FIG. 2 ; 
         FIG. 5  is an explanation drawing of a position adjusting mechanism possessed by the turbine casing structure according to the first embodiment of the present invention; 
         FIG. 6  is a bottom view of a cover member possessed by the turbine casing structure according to the first embodiment of the present invention; 
         FIGS. 7(   a ) and  7 ( b ) are views, in tabular form, showing the relationship between an engagement combination of the cover member and an eccentric shaft possessed by the turbine casing structure according to the first embodiment of the present invention, and the amount of movement in the up-and-down direction (vertical movement) of an inner casing; 
         FIG. 8  is a view showing the state of assemblage of the turbine casing structure according to the first embodiment of the present invention; 
         FIG. 9  is a side view of a shaft adjusting jig for the eccentric shaft which is possessed by the turbine casing structure according to the first embodiment of the present invention; 
         FIG. 10  is a schematic sectional view of a turbine having a conventional turbine casing structure applied thereto; and 
         FIG. 11  is an enlarged view of a portion encircled with line XI in  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The best mode for putting the turbine casing structure according to the present invention into practice will be described in detail based on the following embodiments with reference to the accompanying drawings. 
     First Embodiment 
       FIG. 1  is a schematic sectional view of a turbine having a turbine casing structure according to the first embodiment of the present invention applied thereto.  FIG. 2  is an enlarged view of a portion enclosed with line II in  FIG. 1 .  FIG. 3  is a view taken on line III-III in  FIG. 2 .  FIG. 4  is a view taken along line IV in  FIG. 2 .  FIG. 5  is an explanation drawing of a position adjusting mechanism possessed by the turbine casing structure.  FIG. 6  is a bottom view of a cover member possessed by the turbine casing structure.  FIGS. 7(   a ) and  7 ( b ) are views, in tabular form, showing the relationship between an engagement combination of the cover member and an eccentric shaft possessed by the turbine casing structure, and the amount of vertical movement of an inner casing,  FIG. 7(   a ) showing a case where the eccentric position of the eccentric shaft (the position of the shaft center of a front end portion with respect to the shaft center of a head portion) is located on an upstream side, and  FIG. 7(   b ) showing a case where the eccentric position of the eccentric shaft is located on a downstream side.  FIG. 8  is a view showing the state of assemblage of the turbine casing structure.  FIG. 9  is a side view of a shaft adjusting jig for the eccentric shaft which the turbine casing structure has. 
     A turbine casing structure  10 , as shown in  FIG. 1 , has an outer casing  1  divided into two portions, i.e., an upper portion and a lower portion, and an inner casing  2  disposed within the outer casing  1  and divided into two portions, i.e., an upper portion and a lower portion. When viewed from the upstream side of a turbine, torque pins (circumferential movement restraining means)  3  are mounted on the upper portion and the lower portion of the outer casing  1 . Position adjusting mechanisms  4  are mounted in the vicinity of a parting surface  1   a  in the lower half of the outer casing  1 , and in right-hand and left-hand opposite side portions of the outer casing  1  when viewed from the upstream side of the turbine. A plurality of stationary blades (not shown), which are arranged between moving blades (not shown) rotatably supporting a rotor (not shown) and assembled in multiple stages to the rotor, are assembled to the inner casing  2 . 
     The torque pins  3  adjust the position in the right-and-left direction of the inner casing  2  with respect to the outer casing  1  to restrain the movement in the circumferential direction of the inner casing  2  with respect to the outer casing  1 . The position adjusting mechanisms  4  adjust the position in the up-and-down (vertical) direction of the inner casing  2  with respect to the outer casing  1 . Measuring gauges  5 , which measure the position of the inner casing  2  with respect to the outer casing  1 , are mounted in the vicinity of the torque pins  3  and the position adjusting mechanisms  4 . 
     As shown in  FIGS. 2 to 4 , the position adjusting mechanism  4  has a bush  7  disposed in a concave portion  12  depressed toward the interior of the inner casing  2 , an eccentric shaft  8  which is inserted into a communication hole  1   b  formed opposite the concave portion  12  of the inner casing  2  for establishing communication between the inside and outside of the casing and which has a front end  8   a  located in contact with the bush  7 , and a cover member  11  as a fixing member which is disposed in contact with a head  8   b  of the eccentric shaft  8  and fixed to the outer casing  1  by bolts  9 . As shown in  FIG. 3 , the bush  7  is fixed into the concave portion  12  by bolts  6  and thereby inhibited from being dislodged from the concave portion  12 , and is in such a shape as to contact an upper part  12   a  and a lower part  12   b  of the concave portion  12  of the inner casing  2 , but not to contact side parts  12   c ,  12   d  of the concave portion  12 . Thus, the bush  7  is configured to be inhibited from moving in the up-and-down direction within the concave portion  12 , but be free to move in the right-and-left direction within the concave portion  12 . 
     The cover member  11  has bolt holes  11   a  for insertion of the bolts  9 , and an engaging portion  13  for engagement with an engaged portion  14  of the eccentric shaft  8  to be described later, as shown in  FIGS. 2 and 4  to  6 . The bolt holes  11   a  are formed at predetermined intervals along the outer periphery of the cover member  11 , and seven of the bolt holes  11   a  are formed here. The engaging portion  13  of the cover member  11  is tubular, and is formed in the interior of the cover member  11 . The engaging portion  13  consists of convexities  13   a  convex outward, and concavities  13   b  located between the adjacent convexities  13   a . In the engaging portion  13 , twelve of the convexities  13   a  and twelve of the concavities  13   b  are formed. A confirmation hole  11   b  is formed in the cover member  11 , and this hole  11   b  makes it possible to confirm letters described on the head  8   b  of the eccentric shaft  8  in correspondence with shaft convexities  14   a  of the engaged portion  14  of the eccentric shaft  8 . 
     As shown in  FIG. 5 , the engaged portion  14  to be brought into engagement with the engaging portion  13  of the cover member  11  is formed in the head  8   b  of the eccentric shaft  8 . The engaged portion  14  of the eccentric shaft  8  is in the shape of a gear consisting of the shaft convexities  14   a  convex outward, and shaft concavities  14   b  located between the adjacent shaft convexities  14   a . In the engaged portion  14 , twelve each of the shaft convexities  14   a  and the shaft concavities  14   b  are formed. However, the shaft center C 1  of the head  8   b  of the eccentric shaft  8  is eccentric by a distance L with respect to the shaft center C 2  of the front end  8   a , as shown in  FIG. 4 . Here, the distance L is 0.8 mm. 
     Thus, according to the eccentric shaft  8  having such a shape, when the eccentric shaft  8  is rotated, the front end  8   a  of the eccentric shaft  8  draws a circle of a predetermined size (i.e., the front end  8   a  moves in the right-and-left direction and the up-and-down direction). At the front end  8   a  of the eccentric shaft  8 , its movement in the right-and-left direction is cancelled by the bush  7 , but its movement in the up-and-down direction acts on the inner casing  2  via the bush  7 , so that the position in the up-and-down direction of the inner casing  2  with respect to the outer casing  1  can be adjusted from the outside. As a result, the work efficiency can be increased. 
     One of the bolt holes,  11   a , and the confirmation hole  11   b  of the cover member  11  are located in the direction of 12 o&#39;clock, and the shaft center C 2  of the front end  8   a  of the eccentric shaft  8  is located in the direction of 9 o&#39;clock. In this state, the bolt hole  11   a  located in the direction of 12 o&#39;clock (the direction of the turbine casing reference axis) is designated as A, and the shaft convexity  14   a  located in the same direction (visible through the confirmation hole  11   b ) is designated as a. The respective bolt holes  11   a  are sequentially marked the symbols A to G counterclockwise. Similarly, the respective shaft convexities  14   a  are sequentially marked the symbols a to h and j to m counterclockwise. 
     The procedure for assembling the turbine casing structure  10  according to the first embodiment of the present invention will be described below. 
     (1) First, as shown in  FIG. 8 , a holding plate  15  is disposed in contact with a parting surface  2   b  of a lower-half inner casing  2   a . Also, a bolt hole  2   c  formed in the parting surface  2   b  of the lower-half inner casing  2   a  and a through-hole  15   a  formed in the holding plate  15  are disposed in alignment with each other, and a collar  16  as a tubular body is inserted into the through-hole  15   a  and the bolt hole  2   c . Then, a bolt  17  is inserted into the collar  16  and the bolt hole  2   c , and a cap nut  18  is attached to the head of the bolt  17  to fix the holding plate  15  to the lower-half inner casing  2   a . The lower-half inner casing  2   a  having the holding plate  15  fixed thereto in this manner is assembled to a lower-half outer casing  1   c.  
 
(2) Then, as shown in  FIGS. 2 and 8 , the eccentric shaft  8  and the cover member  11  are temporarily assembled. That is, the eccentric shaft  8  is inserted into the communication hole  1   b  of the outer casing  1 , and its front end  8   a  is brought into contact with the bush  7  disposed in the concave portion  12  of the inner casing  2 . The engaging portion  13  of the cover member  11  is engaged with the engaged portion  14  of the eccentric shaft  8 , and the cover member  11  is fixed to the outer casing  1  by the bolts  9 . At this time, the position of the symbol d of the eccentric shaft  8  (eccentric position of the eccentric shaft  8 ) is confirmed.
 
(3) The current combination of the engaged portion  14  of the eccentric shaft  8  and the engaging portion  13  of the cover member  11  is recorded.
 
(4) Then, the holding plate  15 , the collar  16  and the cap nut  18  are detached from the lower-half inner casing  2   a , an upper-half inner casing is assembled to the lower-half inner casing  2   a , and an upper-half outer casing is assembled to the lower-half outer casing  1   c.  
 
(5) Then, the cover member  11  is detached and, as shown in  FIG. 9 , a shaft adjusting jig  19  capable of adjusting the position of the eccentric shaft  8  is assembled to the eccentric shaft  8 .
 
     Next, an explanation will be offered for the procedure for adjusting the position in the up-and-down direction of the inner casing  2  by the position adjusting mechanism  4  possessed by the turbine casing structure according to the first embodiment of the present invention. 
     (i) The amount of vertical movement (movement in the up-and-down direction), which is the closest to the required amount of movement, is read from the tables described in  FIGS. 7(   a ),  7 ( b ), and recorded. That is, if the eccentric position of the eccentric shaft  8  is located on the upstream side when viewed from the upstream side of the turbine during temporary assemblage of the eccentric shaft  8  and the cover member  11 , the amount of vertical movement is read from the table in  FIG. 7(   a ) and recorded. If the eccentric position of the eccentric shaft  8  is located on the downstream side, on the other hand, the amount of vertical movement is read from the table in  FIG. 7(   b ) and recorded.
 
(ii) The current position of the inner casing  2  is measured with the measuring gauge  5 , and recorded.
 
(iii) Then, the inner casing  2  is supported by push-up bolts  20 , the push-up bolts  20  are fixed to the outer casing  1 , and the eccentric shaft  8  and the cover member  11  are detached from the outer casing  1 .
 
(iv) Then, the amount of vertical movement is confirmed and, with the measuring gauge being seen, the inner casing  2  is moved by the push-up bolts  20 .
 
(v) Then, the eccentric shaft  8  and the cover member  11  are assembled so that their combination coincides with the engagement combination No. recorded in (i). If it is difficult to assemble the eccentric shaft  8  and the cover member  11  as in the tabulated combination, however, the position of the inner casing  2  may be adjusted using the push-up bolts  20 .
 
(vi) Upon completion of the operation for adjusting the position in the up-and-down direction of the inner casing  2  with respect to the outer casing  1 , a stop plug (not shown) or the like is assembled into the confirmation hole  11   b  of the cover member  11 .
 
     According to the turbine casing structure  10  concerned with the first embodiment of the present invention, therefore, the position in the circumferential direction of the eccentric shaft  8  is adjusted, and fixed by the cover member  11 . By so doing, at the front end  8   a  of the eccentric shaft  8 , its movement in the right-and-left direction is cancelled by the bush  7 , but its movement in the up-and-down direction acts on the inner casing  2  via the bush  7 . Thus, the position in the up-and-down direction of the inner casing  2  with respect to the outer casing  1  can be adjusted from the outside. As a result, the work efficiency can be increased. Moreover, the eccentric amount of the eccentric shaft  8 , and the combination of the engaged portion  14  of the eccentric shaft  8  and the engaging portion  13  of the cover member  11  are recorded during manufacture, whereby the turbine casing structure can be easily assembled in the same state as that during manufacture when the turbine is installed in situ. Furthermore, the position in the up-and-down direction of the inner casing  2  with respect to the outer casing  1  can be set with high accuracy. Since the position of the engaged portion  14  of the eccentric shaft  8  can be confirmed through the confirmation hole  11   b , the combination of the engaged portion  14  and the engaging portion  13  of the cover member  11  can be easily adjusted, thus increasing the work efficiency. 
     The above descriptions have been offered in connection with the use of the cover member  11  which is disposed in engagement with the head  8   b  of the eccentric shaft  8  and is fixed to the outer casing  1 . However, any member, which can engage and stop the eccentric shaft  8  and can be fixed to the outer casing  1 , is acceptable. If the eccentric amount of the eccentric shaft  8  is increased, the range of vertical movement of the inner casing  2  with respect to the outer casing  1  can be expanded. If the numbers of the convexities and the concavities of the engaging portion  13  of the cover member  11  and the convexities and the concavities of the engaged portion  14  of the eccentric shaft  8  are increased, the inner casing  2  can be adjusted with a fine pitch within the above range of vertical movement. If the numbers of the convexities and the concavities of the engaging portion  13  of the cover member  11  and the convexities and the concavities of the engaged portion  14  of the eccentric shaft  8  are decreased, the inner casing  2  can be adjusted with a rough pitch within the above range of vertical movement. 
     As described above, the present invention can be used for a turbine casing structure. 
     The invention thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.