Abstract:
A centrifugal compressor bundle that is provided with a bundle main body in which is formed an annular intake flow channel (FC 1 ) that is centered on an axis line (O) and that leads a process gas (G) into a flow channel (FC) of an impeller, and in which is also formed an annular discharge flow channel (FC 2 ) that is centered on the axis line (O) and that discharges the process gas (G) from the flow channel (FC) of the impeller. The bundle main body has a plurality of diaphragms that are aligned in the direction of the axis line (O) and that are bonded to each other. From among the plurality of diaphragms, an intake diaphragm in which the intake flow channel (FC 1 ) is formed is partitioned so as to have an upper-half part and a lower-half part that sandwich, from above and below, a horizontal plane that includes the axis line (O). The upper-half part and the lower-half part have the same rigidity in the direction of the axis line (O).

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a bundle in a centrifugal compressor and a centrifugal compressor having the bundle. 
       BACKGROUND ART 
       [0002]    For example, in order to compress a process gas in various plants, a centrifugal compressor is used. In the centrifugal compressor, the process gas entering a bundle from a suction port is compressed in a flow channel of an impeller by rotating the impeller along with a rotary shaft, and the process gas is ejected to the outside of the bundle from the discharge port. 
         [0003]    Meanwhile, a centrifugal compressor bundle is formed by connecting a plurality of disk-shaped members (diaphragms) such as an intake casing, a discharge casing, and an impeller housing disclosed in PTL 1 in a direction of a rotary shaft. Each diaphragm is divided into two portions on the horizontal plane in a vertical direction. 
       CITATION LIST 
     Patent Literature 
       [0004]    [PTL 1] Japanese Unexamined Patent Application Publication No. 10-318191 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0005]    In a centrifugal compressor, since a fluid is compressed from an intake side toward a discharge side so as to increase a pressure of the fluid, a pressing force is applied in a direction of an axis line of a rotary shaft from a discharge diaphragm (discharge side diaphragm) toward an intake diaphragm (intake side diaphragm). Here, in the intake diaphragm, a shape of a side to which a suction port is connected is different from a shape of a side to which the suction port is not connected. That is, since shapes of an upper-half portion and a lower-half portion which are divided into two portions are different from each other, if the pressing force is applied to the portions, and there is a difference in deformation amounts of the upper-half portion and the lower-half portion in the direction of the axis line. As a result, if the pressing force is applied to the intake diaphragm, the diaphragm is deformed to be bent with respect to the axis line, and an operation of the compressor is likely to be failed. 
         [0006]    The present invention provides a centrifugal compressor bundle capable of decreasing a bending deformation and a centrifugal compressor having this bundle. 
       Solution to Problem 
       [0007]    According to a first aspect of the present invention, there is provided a centrifugal compressor bundle, including: a bundle main body which includes a rotary shaft, an intake flow channel which rotatably supports an impeller which is fixed to the rotary shaft and rotates along with the rotary shaft about an axis line of the rotary shaft, introduces a fluid in a flow channel of the impeller, and is annularly formed about the axis line, and a discharge flow channel which discharges the fluid from a flow channel of the impeller and is annularly formed about the axis line, in which the bundle main body includes a plurality of diaphragms which are aligned in the direction of the axis line and are connected to each other, and among the plurality of diaphragms, an intake diaphragm in which the intake flow channel is formed includes an upper-half portion positioned on an upper side and a lower-half portion positioned on a lower side configured by dividing the intake diaphragm into two portions such as the upper side and the lower side in a state where a horizontal plane including the axis line is interposed therebetween, and the upper-half portion and the lower-half portion have the same rigidity as each other in the direction of the axis line. 
         [0008]    According to the centrifugal compressor bundle, a pressing force is applied to the intake diaphragm of the bundle main body in the direction of the axis line from a rear stage side toward a front stage side by the compressed fluid. In this case, since the rigidities of the upper-half portion and the lower-half portion of the intake diaphragm are the same as each other in the direction of the axis line, the upper-half portion and the lower-half portion are deformed by the same amount as each other in the direction of the axis line. Accordingly, the intake diaphragm is not deformed to be inclined with respect to the horizontal plane including the axis line, and the intake diaphragm is deformed in only the direction of the axis line. 
         [0009]    In addition, in the centrifugal compressor bundle according to a second aspect of the present invention, in the first aspect, areas of contact surfaces between the intake diaphragm and the diaphragms which are adjacent to the intake diaphragm on the discharge flow channel side in the direction of the axis line may be the same as each other in the upper-half portion and the lower-half portion. 
         [0010]    In this way, since the area of the contact surface with the adjacent diaphragm is the same in the upper-half portion and the lower-half portion, when the pressing force is applied to the intake diaphragm in the direction of the axis line by the compressed fluid, surface pressures on the contact surfaces of the upper-half portion and the lower-half portion can be the same as each other. Accordingly, since the intake diaphragm is deformed to be equally compressed in the direction of the axis line by the pressing force, the intake diaphragm is not deformed to be inclined with respect to the horizontal plane including the axis line, and the intake diaphragm is deformed in only the direction of the axis line. 
         [0011]    In addition, in the centrifugal compressor bundle according to a third aspect of the present invention, in the first or second aspect, an inlet of the intake flow channel may be formed in the upper-half portion, the upper-half portion may include a first straightening plate which is provided in the inlet and extends in the radial direction, and a pair of second straightening plates which is disposed on both sides in a peripheral direction of the rotary shaft with respect to the first straightening plate and is provided to be separated from the first straightening plate toward the inside in the radial direction, and surfaces of the first straightening plate and the second straightening plate facing the direction of the axis line may configure a portion of the contact surface. 
         [0012]    In this way, since the first straightening plate and the second straightening plate configure the contact surface with a head adjacent to the intake diaphragm in the direction of the axis line, it is possible to equalize deformation amounts of the upper-half portion and the lower-half portion without disturbing the flow of the fluid entering from the suction port to the intake flow channel. 
         [0013]    In addition, in the centrifugal compressor bundle according to a fourth aspect of the present invention, in the third aspect, the contact surfaces of the intake diaphragm may be formed at positions separated by 90° around the axis line based on the position of the first straightening plate. 
         [0014]    In this way, since the contact surfaces are formed at the positions every 90° in the peripheral direction, it is possible to approximately equally distribute the pressing force from the compressed fluid in the peripheral direction, and deformation of the upper-half portion and the lower-half portion can be generated in the direction of the axis line. Accordingly, it is possible to prevent the deformation of the intake diaphragm which is inclined with respect to the horizontal plane including the axis line, that is, it is possible to prevent generation of bending deformation. 
         [0015]    In addition, according to a five aspect of the present invention, there is provided a centrifugal compressor, including: the centrifugal compressor bundle according to any one of the first to fourth aspects; a rotary shaft which is supported by the bundle so as to be rotatable with respect to the bundle; and an impeller which is fixed to the rotary shaft and rotates in the bundle main body along with the rotary shaft. 
         [0016]    According to the centrifugal compressor, since the centrifugal compressor includes the bundle, when the pressing force is applied to the intake diaphragm of the bundle main body in the direction of the axis line from the rear stage side toward the front stage side by the compressed fluid, the upper-half portion and the lower-half portion are deformed by the same amount as each other in the direction of the axis line. Accordingly, the intake diaphragm is not deformed to be inclined with respect to the horizontal plane including the axis line, and the intake diaphragm is deformed in only the direction of the axis line. 
       Advantageous Effects of Invention 
       [0017]    According to the centrifugal compressor bundle and the centrifugal compressor, since the rigidities of the upper-half portion and the lower-half portion of the intake diaphragm are the same as each other in the direction of the axis line, it is possible to prevent the bending deformation of the bundle main body. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0018]      FIG. 1  is a longitudinal sectional view showing a schematic configuration of a centrifugal compressor in an embodiment of the present invention. 
           [0019]      FIG. 2  is a perspective view showing an intake diaphragm which forms an intake flow channel of the centrifugal compressor in the embodiment of the present invention. 
           [0020]      FIG. 3  is a view showing the intake diaphragm which forms the intake flow channel of the centrifugal compressor in the embodiment of the present invention and is a sectional view showing an A-A cross section of  FIG. 1 . 
           [0021]      FIG. 4  is a view showing an intake diaphragm of a first example of examples of the centrifugal compressor, and a sectional view at a position corresponding to the A-A cross section of  FIG. 1 . 
           [0022]      FIG. 5  is a view showing an intake diaphragm of a second example of examples of the centrifugal compressor, and a sectional view at the position corresponding to the A-A cross section of  FIG. 1 . 
           [0023]      FIG. 6  is a view showing an intake diaphragm of a third example of examples of the centrifugal compressor, and a sectional view at the position corresponding to the A-A cross section of  FIG. 1 . 
           [0024]      FIG. 7  is a view showing an intake diaphragm of a fourth example of examples of the centrifugal compressor, and a sectional view at the position corresponding to the A-A cross section of  FIG. 1 . 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0025]    Hereinafter, a centrifugal compressor  1  of an embodiment of the present invention will be described. 
         [0026]    As shown in  FIG. 1 , in the present embodiment, as an example of the centrifugal compressor  1 , a multi-stage centrifugal compressor will be described, in which a pair of three-stage impeller groups  4  which rotates about an axis line O is symmetrically disposed on one side and the other side in the direction of the axis line O. 
         [0027]    The centrifugal compressor  1  includes a rotary shaft which rotates about the axis line O, a plurality of impellers  3  which are fixed to the rotary shaft  2 , a bundle  5  which rotatably supports the rotary shaft  2  and the impellers  3 , and an outside casing  6  which covers the bundle  5  from the outer peripheral side. 
         [0028]    The rotary shaft  2  is formed in a columnar shape about the axis line O. 
         [0029]    The plurality of impellers  3  (six impellers in the present embodiment) are arranged to be separated from each other in the direction of the axis line O. 
         [0030]    Each of the impellers  3  has an approximately disk shape, is fitted to the rotary shaft  2 , and is rotatable about the axis line O along with the rotary shaft  2 . In addition, a flow channel FC through which a process gas G (fluid) can flow is formed in each impeller  3 . 
         [0031]    In three impellers  3  which are disposed on one side (a left side toward a paper surface of  FIG. 1 ) in the direction of the axis line O, an inlet of the flow channel FC of each impeller  3  is disposed toward the one side in the direction of the axis line O, and the three impellers  3  configure one impeller group  4  (hereinafter, referred to as a first impeller group  4 A). 
         [0032]    In three-stage impellers  3  which are disposed on the other side (the right side toward the paper surface of  FIG. 1 ) in the direction of the axis line O, an inlet of the flow channel FC of the impeller  3  is disposed toward the other side in the direction of the axis line O, and the three-stage impellers  3  configure one impeller group  4  (hereinafter, referred to as a second impeller group  4 B). 
         [0033]    The bundle  5  includes a plurality of diaphragms  11  which are formed in disk shapes about the axis line O and a bundle main body  10  having heads  12 . 
         [0034]    The plurality of diaphragms  11  and the heads  12  are connected in the direction of the axis line O by bolts (not shown) to form the bundle main body  10 . That is, the bundle main body  10  has a structure which is divided into a plurality of portions on a cross-section orthogonal to the axis line O. 
         [0035]    A pair of heads  12  is provided such that the plurality of diaphragms  11  are interposed between both ends of the axis line O in the direction of the axis line O, and each head is a member which is formed in a disk shape about the axis line O. 
         [0036]    Each diaphragm  11  has a structure which is divided into two portions in a vertical direction on a horizontal plane including the axis line O. 
         [0037]    In the bundle main body  10 , the diaphragms  11  of one end portion and the other end portion in the direction of the axis line O become intake diaphragms  11 A. In each intake diaphragm  11 A, an intake flow channel FC 1  which is annually formed about the axis line O and through which the process gas G can be introduced to the flow channel FC of the impeller  3  is formed. In the intake flow channel FC 1 , an intake flow channel opening OP 1  (inlet) is formed, which is open to the outside in the radial direction on a portion (the upper portion in the present embodiment) in the peripheral direction in the intake diaphragm  11 A. 
         [0038]    The intake diaphragm  11 A is divided in the vertical direction, and includes an upper-half portion  20  which is formed in a semi-disk shape and is positioned on the upper side, and a lower-half portion  30  which is formed in a semi-disk shape and is positioned on the lower side. The details of the upper-half portion  20  and the lower-half portion  30  will be described later. 
         [0039]    In the bundle main body  10 , the diaphragm  11  which covers the initial stage (first stage) impeller  3 ( 3 A) in each of the first impeller group  4 A and the second impeller group  4 B becomes a first intermediate diaphragm  11 B. In the first intermediate diaphragm  11 B, a return flow channel FC 3  which communicates with an outlet of the flow channel FC of the initial stage impeller  3  ( 3 A) and an inlet of a flow channel FC of an intermediate stage (second stage) impeller  3  ( 3 B) is formed. 
         [0040]    Similarly, in the bundle main body  10 , the diaphragm which covers the intermediate stage (second stage) impeller  3 ( 3 B) in each of the first impeller group  4 A and the second impeller group  4 B becomes a second intermediate diaphragm  11 C. In the second intermediate diaphragm  11 C, a return flow channel FC 4  which communicates with an outlet of the flow channel FC of the intermediate stage impeller  3  ( 3 B) and an inlet of the flow channel FC of a final stage (third stage) impeller  3  ( 3 C) is formed. 
         [0041]    In the second intermediate diaphragm  11 C, a portion of a discharge flow channel FC 2  which is annularly formed about the axis line O and can discharge the process gas G from the flow channel FC of the impeller  3  is formed. 
         [0042]    In the bundle main body  10 , the diaphragm  11  which covers the final stage (third stage) impeller  3  ( 3 C) in each of the first impeller group  4 A and the second impeller group  4 B becomes a discharge diaphragm  11 D. In the discharge diaphragm  11 D, a portion of the remainder of the discharge flow channel FC 2  which is annularly formed about the axis line O and can discharge the process gas G from the flow channel FC of the impeller  3  is formed. 
         [0043]    That is, the discharge flow channel FC 2  is formed by the discharge diaphragm  11 D and the second intermediate diaphragm  11 C. In the discharge flow channel FC 2 , a discharge flow channel opening OP 2  (outlet) is formed, which is open to the outside in the radial direction at a portion (the upper portion in the present embodiment) of the second intermediate diaphragm  11 C and the discharge diaphragm  11 D in the peripheral direction. 
         [0044]    In the bundle main body  10 , the diaphragm  11  which is disposed at a position interposed between the first impeller group  4 A and the second impeller group  4 B becomes a diaphragm  11 E between final stages. In the diaphragm  11 E between final stages, a seal device  15  which seals the flow of the process gas G between the first impeller group  4 A and the second impeller group  4 B is provided on the outer peripheral side of the rotary shaft  2 . 
         [0045]    The outside casing  6  is formed in a cylindrical shape, covers the bundle main body  10  from the outer peripheral side, and fixes the bundle main body  10 . A pair of suction ports  6   a  which extends in the radial direction, is open to the outside, and communicates with the intake flow channel opening OP 1  is formed in the outside casing  6 . In addition, a pair of discharge ports  6   b  which extends in the radial direction, is open to the outside, and communicates with the discharge flow channel opening OP 2  is formed in the outside casing  6 . 
         [0046]    In the present embodiment, the suction ports  6   a  and the discharge ports  6   b  are formed on the upper portion of the outside casing  6  so as to extend upward. 
         [0047]    Next, the details of the upper-half portion  20  and the lower-half portion  30  of the intake diaphragm  11 A will be described with reference to  FIGS. 2 and 3 . 
         [0048]    The upper-half portion  20  includes a main body portion  22  which is formed in a semi-disk shape about the axis line O and a first straightening plate  23 , second straightening plates  24 , and outer wall portions  25  which protrude from the main body portion  22  toward the head  12  side in the direction of the axis line O. 
         [0049]    A semicircular opening  20   a  which surrounds the rotary shaft  2  from the outer peripheral side is formed at the position inside the main body portion  22  in the radial direction. 
         [0050]    The first straightening plate  23  extends in the radial direction (in the vertical direction) from the intake flow channel opening OP 1  toward the inside in the radial direction, protrudes from the main body portion  22  toward the head  12  side in the direction of the axis line O, and is formed in a vane shape when viewed in the direction of the axis line O. 
         [0051]    That is, after the thickness dimension of the first straightening plate  23  in the peripheral direction gradually increases toward the inside in the radial direction, the thickness dimension gradually decreases. 
         [0052]    In the first straightening plate  23 , an approximately half portion  23   a  on the outside in the radial direction of a surface facing the head  12  side in the direction of the axis line O becomes a portion of a contact surface  40  with the head  12  adjacent to the intake diaphragm  11 A in the direction of the axis line O. 
         [0053]    The second straightening plates  24  are disposed to be separated from the first straightening plate  23 , and are disposed to be inclined so as to be separated from the first straightening plate  23  toward the inside in the radial direction at each of both sides in the peripheral direction with respect to the first straightening plate  23 . 
         [0054]    That is, the process gas G from the suction port  6   a  can flow through a portion between the second straightening plate  24  and the first straightening plate  23 . 
         [0055]    Each second straightening plate  24  protrudes from the main body portion  22  toward the head  12  side in the direction of the axis line O, and is formed in a rectangular shape when viewed in the direction of the axis line O. 
         [0056]    In the second straightening plate  24 , an approximately half portion  24 a on the outside in the radial direction of a surface facing the head  12  side in the direction of the axis line O becomes a portion of a contact surface  40  with the head  12  adjacent to the intake diaphragm  11 A. 
         [0057]    A pair of outer wall portions  25  is provided to be curved along the outer peripheral surface of the main body portion  22  and forms the outer wall of the intake flow channel FC 1 . In addition, the pair of outer wall portions is formed to the position separated from the second straightening plate  24  in the peripheral direction on the upper portion. That is, the process gas G can flow through a portion between the second straightening plates  24 . 
         [0058]    Since the thickness dimension of the outer wall portion  25  in the radial direction gradually increases downward, a flow channel area of the intake flow channel FC 1  gradually decreases downward. 
         [0059]    In the surface of the outer wall portion  25  facing the discharge flow channel FC 2  side in the direction of the axis line O, only a portion  25   a  along the peripheral surface of the main body portion  22  becomes a portion of the contact surface  40  with the head  12 . The width dimension of the portion  25   a  along the peripheral surface in the radial direction is constant in the peripheral direction. 
         [0060]    The lower-half portion  30  includes a main body portion  32  which is formed in a semi-disk shape about the axis line O and an outer wall portion  35  which protrudes from the main body portion  32  toward the head  12  side in the direction of the axis line O. 
         [0061]    In the main body portion  32 , a semicircular opening  30   a  which surrounds the rotary shaft  2  from the outer peripheral side at the position on the inside in the radial direction is formed. A circular opening  11 Aa into which the rotary shaft  2  can be inserted is formed by the opening  30   a  and the opening  20   a  in the main body portion  22  of the upper-half portion  20 . 
         [0062]    The outer wall portion  35  is curved along the outer peripheral surface of the main body portion  32 , is provided on the entire region of the outer peripheral surface of the main body portion  32 , and forms the outer wall of the intake flow channel FC 1 . 
         [0063]    Since the thickness dimension in the radial direction of the outer wall portion  35  gradually increases downward, the flow channel area of the intake flow channel FC 1  gradually decreases downward. 
         [0064]    The thickness of the upper end portion of the outer wall portion  35  coincides with the thickness of the lower end portion of the outer wall portion  25  of the upper-half portion  20 , and the outer wall portion  35  of the lower-half portion  30  and the outer wall portion  25  of the upper-half portion  20  are smoothly connected to each other without steps. 
         [0065]    In addition, in the surface of the outer wall portion  35  facing the head  12  side in the direction of the axis line O, only a portion of an annular portion  35 a of a half circumference about the axis line O along the outer peripheral surface of the main body portion  32  becomes a portion of the contact surface  40  with the head  12 . 
         [0066]    More specifically, as the contact surface  40  in the lower-half portion  30 , a pair of curved surfaces  41  which is formed from the upper end portion of the lower-half portion  30  to the intermediate position in the vertical direction, and an approximately rectangular lower end surface  42  which is formed on the lower end portion to be separated from the curved surfaces  41  in the peripheral direction are formed on the lower-half portion  30 . 
         [0067]    In the curved surfaces  41  and the lower end surface  42 , the outer wall portion  35  is formed to be recessed in the direction of the axis line O between the curved surface  41  and the lower end surface  42 . 
         [0068]    The width dimensions of the curved surfaces  41  and the lower end surface  42  in the radial direction are the same as the width dimensions in the radial direction of the portions  25   a  along the outer peripheral surface in the outer wall portion  25  of the upper-half portion  20 , and the width dimensions are constant in the peripheral direction. 
         [0069]    Moreover, in the present embodiment, the upper-half portion  20  and the lower-half portion  30  are formed of the same material, and rigidities of the upper-half portion  20  and the lower-half portion  30  are the same as each other. 
         [0070]    In addition, the area of the contact surface  40  of the upper-half portion  20  is the same as the area of the contact surface  40  of the lower-half portion  30 . Moreover, in the present embodiment, the contact surfaces  40  are formed at least positions separated by 90° around the axis line O based on the position of the first straightening plate  23 . 
         [0071]    According to the above-described centrifugal compressor  1 , a force is generated in the direction of the axis line O from the front stage side (discharge diaphragm  11 D side) toward the rear stage side (intake diaphragm  11 A side) by the compressed process gas G, and this force becomes a pressing force and is applied to the intake diaphragm  11 A. 
         [0072]    In this case, since the rigidities of the upper-half portion  20  and the lower-half portion  30  of the intake diaphragm  11 A are the same as each other in the direction of the axis line O, the upper-half portion  20  and the lower-half portion  30  are deformed by the same amount as each other in the direction of the axis line O. Accordingly, the intake diaphragm  11 A is not deformed to be inclined with respect to the horizontal plane including the axis line O, and the intake diaphragm  11 A is deformed in only the direction of the axis line O. Accordingly, it is possible to prevent the intake diaphragm  11 A from being inclined to the horizontal plane and bending-deformed. 
         [0073]    In addition, since the area of the contact surface of the upper-half portion  20  and the area of the contact surface  40  of the lower-half portion  30  are the same as each other, when the pressing force is applied to the intake diaphragm  11 A in the direction of the axis line O by the compressed process gas G, surface pressures on the contact surfaces  40  of the upper-half portion  20  and the lower-half portion  30  can be the same as each other. 
         [0074]    Accordingly, since the intake diaphragm  11 A is deformed to be equally compressed in the direction of the axis line O by the pressing force, it is possible to further prevent the bending deformation of the intake diaphragm  11 A. 
         [0075]    In addition, since the first straightening plate  23  and the second straightening plates  24  configure the contact surface  40  with the head  12 , it is possible to equalize deformation amounts of the upper-half portion  20  and the lower-half portion  30  without disturbing the flow of the process gas G entering from the suction port  6   a  to the intake flow channel FC 1 . 
         [0076]    Particularly, in the present embodiment, since the first straightening plate  23  is formed in a vane shape, it is possible to introduce the process gas G into the intake flow channel FC 1  without separating the process gas G from the suction port  6   a.    
         [0077]    Moreover, in the intake diaphragm  11 A, since the contact surfaces  40  are formed at the positions at least every 90° in the peripheral direction, it is possible to approximately equally distribute the pressing force in the peripheral direction, and deformation of the upper-half portion  20  and the lower-half portion  30  due to the pressing force can be generated in the direction of the axis line O. Accordingly, it is possible to prevent generation of the bending deformation in the intake diaphragm  11 A. 
       EXAMPLE 
       [0078]    Here, with reference to  FIGS. 4 to 7 , a test confirming deformation amounts of the bundle  5  due to the pressing force was performed on examples in which shapes of the upper-half portion and the lower-half portion were different from each other. 
         [0079]    In an intake diaphragm  51 A shown in  FIG. 4 , an upper-half portion  52  includes the main body portion  22 , the first straightening plate  23 , and the outer wall portion  25 , and the lower-half portion  53  includes the main body portion  32  and the outer wall portion  35 . 
         [0080]    In the upper-half portion  52 , the contact surface  40  with the head  12  is configured of approximately the half portion  23   a  (the portion similar to that of the above-described embodiment) on the outside in the radial direction in the surface of the first straightening plate facing the head  12  side in the direction of the axis line O, and the portion  25   a  along the outer peripheral surface of the main body portion  22  in the surface of the outer wall portion  25  facing the head  12  side in the direction of the axis line O. 
         [0081]    In addition, in the lower-half portion  53 , the contact surface  40  is configured of the entire region of an annular portion  53   a  of a half circumference about the axis line O along the outer peripheral surface of the main body portion  32  in the surface of the outer wall portion facing the head  12  side in the direction of the axis line O. The width dimension in the radial direction of the annular portion  53   a  of the half circumference is constant in the peripheral direction. 
         [0082]    In the intake diaphragm  51 A, since the deformation amount of the upper-half portion  52  in the direction of the axis line O was large and the deformation amount of the lower-half portion  53  in the direction of the axis line O was small, the bundle main body  10  was bending-deformed such that the upper-half portion  52  was inclined to the head  12  side with respect to the axis line O. 
         [0083]    Accordingly, as shown in  FIG. 5 , second straightening plates  64  were further provided on both sides in the peripheral direction with respect to the first straightening plate  23  in the upper-half portion  62  of the intake diaphragm  61 A. The thickness dimension of each of the second straightening plate  64  in the peripheral direction is 6 [mm]. In the second straightening plate  64 , an approximately half portion  64   a  on the outside in the radial direction in the surface facing the head  12  side in the direction of the axis line O becomes a portion of the contact surface  40 . 
         [0084]    As result, the deformation amount of the upper-half portion  62  was small in the direction of the axis line O, but a difference between the deformation amount of the lower-half portion  53  in the direction of the axis line O was large, and the bundle main body  10  was still bending-deformed such that the upper-half portion  62  was inclined to the head  12  side with respect to the axis line O. 
         [0085]    In addition, as shown in  FIG. 6 , in an intake diaphragm  71 A, in the portion  53   a  (refer to  FIG. 5 ) forming an annular shape of a half circumference in the outer wall portion  35  of the lower-half portion  73 , the outer wall portion  35  was recessed in the direction of the axis line O in a predetermined region of the lower portion so as to decrease the area of the contact surface  40 , and a pair of curved surfaces  75  was formed in the contact surface  40 . 
         [0086]    As a result, the deformation amount of the lower-half portion  73  in the direction of the axis line O was large, and the bundle main body  10  was bending-deformed such that the lower-half portion  73  was inclined to the head  12  side. 
         [0087]    Accordingly, in the intake diaphragm  81 A shown in  FIG. 7 , in the outer wall portion  35 , an approximately rectangular lower end surface  85  was formed on the lower end portion of the lower-half portion  83  as the contact surface  40  at the position interposed between the pair of curved surfaces  75  in the peripheral direction. Accordingly, the deformation amount of the lower-half portion  83  in the direction of the axis line O and the deformation amount of the upper-half portion  62  in the direction of the axis line O were equalized, and the bending deformation of the bundle main body  10  inclined to the head  12  side was prevented. However, a contact surface pressure of the approximately half portion  64   a  of on the outside of the second straightening plate  24  in the radial direction exceeded allowable stress. 
         [0088]    Accordingly, finally, in the intake diaphragm  11 A of the above-described embodiment shown in  FIG. 3 , the thickness of the second straightening plate  24  in the peripheral direction in the upper-half portion  20  was set to 12 mm, and the width dimension of the lower end surface of the lower-half portion  30  in the peripheral direction was increased to increase the area of the contact surface  40 . 
         [0089]    As a result, the contact surface pressure of the approximately half portion  64   a  of on the outside of the second straightening plate  24  in the radial direction was equal or less than the allowable stress, the deformation amounts of the upper-half portion  20  and the lower-half portion  30  in the direction of the axis line O could be the same as each other, and it was possible to prevent the bending deformation of the bundle main body  10 . 
         [0090]    Hereinbefore, the embodiment of the present invention is described with reference to the drawings, components in each embodiment, a combination thereof, and the like are examples, and addition, omission, replacement, and other modifications of configurations can be applied within a scope which does not depart from the gist of the present invention. In addition, the present invention is not limited by the embodiment and is limited by only claims. 
         [0091]    For example, the first straightening plate  23  may not be formed in a vane shape when viewed in the direction of the axis line O, and may be formed in a rectangular shape similarly to the second straightening plate  24 . 
         [0092]    In addition, similarly to the first straightening plate  23 , the second straightening plate  24  may be formed in a vane shape when viewed in the direction of the axis line O. 
         [0093]    In addition, the number of the first straightening plates  23  and the number of the second straightening plates  24  are not limited. 
       INDUSTRIAL APPLICABILITY 
       [0094]    In the above-described centrifugal compressor bundle and the centrifugal compressor, since the rigidities of the upper-half portion and the lower-half portion of the intake diaphragm in the direction of the axis line are the same as each other, it is possible to prevent the bending deformation of the bundle main body. 
       REFERENCE SIGNS LIST 
       [0095]      1 : centrifugal compressor 
         [0096]      2 : rotary shaft 
         [0097]      3 ,  3 A,  3 B: impeller 
         [0098]      4 : impeller group 
         [0099]      4 A: first impeller group 
         [0100]      4 B: second impeller group 
         [0101]      5 : bundle 
         [0102]      6 : outside casing 
         [0103]      6   a : suction port 
         [0104]      6   b : discharge port 
         [0105]      10 : bundle main body 
         [0106]      11 : diaphragm 
         [0107]      11 A,  51 A,  61 A,  71 A,  81 A: intake diaphragm 
         [0108]      11 Aa: opening 
         [0109]      11 B: first intermediate diaphragm 
         [0110]      11 C: second intermediate diaphragm 
         [0111]      11 D: discharge diaphragm 
         [0112]      11 E: diaphragm between final stages 
         [0113]      12 : head 
         [0114]      15 : seal device 
         [0115]      20 ,  52 ,  62 : upper-half portion 
         [0116]      20   a : opening 
         [0117]      22 : main body portion 
         [0118]      23 : first straightening plate 
         [0119]      24 ,  64 : second straightening plate 
         [0120]      25 : outer wall portion 
         [0121]      30 ,  53 ,  73 ,  83 : lower-half portion 
         [0122]      30   a : opening 
         [0123]      32 : main body portion 
         [0124]      35 : outer wall portion 
         [0125]      40 : contact surface 
         [0126]      41 ,  75 : curved surface 
         [0127]      42 ,  85 : lower end surface 
         [0128]    FC: flow channel 
         [0129]    FC 1 : intake flow channel 
         [0130]    OP 1 : intake flow channel opening 
         [0131]    FC 2 : discharge flow channel 
         [0132]    OP 2 : discharge flow channel opening 
         [0133]    FC 3 : return flow channel 
         [0134]    FC 4 : return flow channel 
         [0135]    O: axis line 
         [0136]    G: process gas (fluid)