Abstract:
The present invention provides a centering mechanism capable of improving the efficiency of centering work and reducing the work time and the cost. The centering mechanism centers an inner member located inside in a radial direction, with respect to an outer member arranged to surround the inner member in a circumferential direction, and includes a vertical-direction positioning unit which positions the inner member in a vertical direction in a non-stepwise manner.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a centering mechanism that performs centering of an inner casing in a turbine or a blade ring in a rotary machine such as a compressor or a turbine. 
         [0003]    This application is based on Japanese Patent Application, Publication No. 2008-115720, the content of which is incorporated herein by reference. 
         [0004]    2. Description of Related Art 
         [0005]    Centering of an inner casing in a turbine or a blade ring in a rotary machine such as a compressor or a turbine is conventionally performed with the use of a pin in the horizontal direction and a key (liner) in the vertical direction (see Japanese Unexamined Patent Application, Publication No. 2005-171783 (FIGS. 2 and 3), for example). 
         [0006]    In this case, for centering in the vertical direction, a key having a thickness larger than a planned value is made in advance, and is cut down to reduce the thickness to fit the actual inner casing or blade ring at the time of assembly and adjustment. The inner casing and the blade ring need to be adjusted such that gaps produced between moving blades and fins during operation are prevented, as much as possible, from being nonuniform in the circumferential direction, while the deformation of the casing and a bearing stand and the deflection of a rotor caused by its weight are taken into account. 
         [0007]    However, after testing, when the deformation of the casing and the bearing stand and the deflection of the rotor caused by its weight are different from those predicted, the centering of the inner casing and the blade ring in the vertical direction and in the width direction needs to be readjusted. However, the frequency of readjusting the positions of the inner casing and the blade ring in the width direction is relatively low. Therefore, the centering in the vertical direction is mainly performed as readjustment work. 
         [0008]    In such a case, there has been a problem in that it is necessary to make a key having a new size and to change to it, thereby taking a long time for the centering of the inner casing and the blade ring, and increasing the cost. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a centering mechanism capable of improving the efficiency of centering work and reducing the time and cost involved with such work. 
         [0010]    The present invention employs the following solutions in order to solve the above-described problems. 
         [0011]    According to a first aspect, the present invention provides a centering mechanism that centers an inner member located inside in a radial direction, with respect to an outer member arranged to surround the inner member in a circumferential direction, the centering mechanism including a vertical-direction positioning unit which positions the inner member in a vertical direction in a non-stepwise manner. 
         [0012]    According to the centering mechanism described above, the inner member is centered in the vertical direction in a non-stepwise manner. Specifically, during the centering work (for example, at the time of assembly and adjustment), the inner member is moved in the vertical direction in a non-stepwise manner and is positioned at a desired position by the vertical-direction positioning unit. 
         [0013]    Therefore, it is possible to easily and quickly position the inner member in the vertical direction, to improve the efficiency of the centering work, and to reduce the work time. 
         [0014]    Unlike the conventional technology, it is unnecessary to prepare a new key (liner) every time the centering work is performed. Therefore, the cost and the work time required for the centering work can be substantially reduced. 
         [0015]    The centering mechanism may further include an oblique member on which the inner member is placed and which extends obliquely with respect to a horizontal direction, in which the oblique member is moved in the horizontal direction to perform the positioning in the vertical direction. 
         [0016]    According to the centering mechanism described above, when the oblique member is moved in the horizontal direction, the inner member placed on the oblique member (more specifically, on the upper face of the oblique member) is thus moved in the vertical direction, thereby positioning the inner member in the vertical direction. 
         [0017]    In the above-described structure, it is more preferred that an angle formed by a horizontal plane and the upper face of the oblique member, on which the inner member is placed, be equal to or larger than a friction angle of the inner member. 
         [0018]    According to the centering mechanism described above, since the inner member is prevented from being moved in the axial direction, the inner member can be maintained at the desired position where the inner member is always centered. 
         [0019]    In the above-described structure, it is more preferred that a low-pressure-side end face of the inner member and a high-pressure-side end face of the outer member be structured to be always in contact. 
         [0020]    According to the centering mechanism described above, for example, in a state where the rotary machine is stopped, or even in a state where gas pressure is low immediately after starting of operation, the low-pressure-side end face of the inner member and the high-pressure-side end face of the outer member are always maintained in contact; in other words, the interface between the low-pressure-side end face of the inner member and the high-pressure-side end face of the outer member is always maintained sealed. 
         [0021]    According to a second aspect, the present invention provides a rotary machine including the centering mechanism capable of easily and quickly positioning the inner member in the vertical direction. Therefore, it is possible to improve the efficiency of work such as new installation and maintenance inspection of a rotary machine and to reduce the work time. 
         [0022]    According to the present invention, it is possible to improve the efficiency of the centering work and to reduce the work time and the cost. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0023]      FIG. 1  is a schematic structural view of the main parts of a gas turbine having a centering mechanism according to an embodiment of the present invention. 
           [0024]      FIG. 2  is a cross-sectional view along the line II-II shown in  FIG. 1 . 
           [0025]      FIG. 3  is a cross-sectional view along the line III-III shown in  FIG. 2 . 
           [0026]      FIG. 4  is a cross-sectional view along the line IV-IV shown in  FIG. 3 . 
           [0027]      FIG. 5  is a perspective view of a key constituting a vertical-direction positioning unit. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0028]    Hereinafter, a centering mechanism according to an embodiment of the present invention will be described with reference to  FIGS. 1 to 5 . 
         [0029]      FIG. 1  is a schematic structural view showing a concrete example in which a centering mechanism  1  according to this embodiment is applied to a turbine (hereinafter referred to as “gas turbine”)  100 .  FIG. 2  is a cross-sectional view along the line II-II shown in  FIG. 1 .  FIG. 3  is a cross-sectional view along the line III-III shown in  FIG. 2 .  FIG. 4  is a cross-sectional view along the line IV-IV shown in  FIG. 3 .  FIG. 5  is a perspective view of a key constituting a vertical-direction positioning unit. 
         [0030]    As shown in  FIG. 1 , the gas turbine (rotary machine)  100  includes, as main components, a compressor  101  which compresses air taken in from outside, combustors  102  which are supplied with the air compressed by the compressor  101  and fuel and which generate combustion gas, and a turbine  103  which is rotated by the combustion gas generated in the combustors  102 . 
         [0031]    Further, the gas turbine  100  includes a rotor  104  having upright moving blades  101   a  and  103   a  on its outer circumference and a casing  105  having upright stationary blades  101   b  and  103   b  on its inner circumference. 
         [0032]    The rotor  104  includes a compressor-side rotor  104   a  which has the moving blades  101   a  used in the compressor  101  and a turbine-side rotor  104   b  which has the moving blades  103   a  used in the turbine  103 . The compressor-side rotor  104   a  and the turbine-side rotor  104   b  are coupled (connected) by an intermediate shaft  104   c.    
         [0033]    The casing  105  is constituted by an upper casing  105   a  and a lower casing  105   b.  The casing  105  covers the outer circumference of the rotor  104 , thereby forming a compressor casing  106  in which the moving blades  101   a  and the stationary blades  101   b  are alternately arranged in the axial direction of the rotor  104 , a combustor casing  107  in which the combustors  102  are arranged at regular intervals in the circumferential direction of the rotor  104 , and a turbine casing  108  in which the moving blades  103   a  and the stationary blades  103   b  are alternately arranged in the axial direction of the rotor  104 . 
         [0034]    In the gas turbine  100  having the above-described structure, when the moving blades  101   a  are rotated in response to the rotation of the compressor-side rotor  104   a,  air taken into the compressor  101  is captured and compressed in spaces between the moving blades  101   a  and the stationary blades  101   b  at respective stages in the compressor casing  106  formed by the compressor-side rotor  104   a  and the casing  105 . Then, when the air compressed in the compressor casing  106  of the compressor  101  flows into the combustor casing  107 , the compressed air is supplied to the combustors  102 . The combustors  102  are supplied with fuel, including fuel gas, and perform combustion using the compressed air supplied from the compressor  101 , thereby generating combustion gas. High-temperature and high-pressure combustion gas generated by the combustors  102  is supplied to the turbine casing  108  formed by the turbine-side rotor  104   b  and the casing  105 , so that the combustion gas flows into spaces between the moving blades  103   a  and the stationary blades  103   b  at respective stages to rotate the turbine-side rotor  104   b.  Note that since the rotation of the turbine-side rotor  104   b  is transferred to the compressor-side rotor  104   a  via the intermediate shaft  104   c , the compressor-side rotor  104   a  also rotates together with the turbine-side rotor  104   b.    
         [0035]    As shown in  FIGS. 1 and 2 , the upper casing  105   a  covering the outer circumferences of the compressor-side rotor  104   a  and the turbine-side rotor  104   b  has an upper outer casing (outer member)  110  and an upper inner casing (inner member)  111 . As shown in  FIG. 2 , the lower casing  105   b  covering the outer circumferences of the compressor-side rotor  104   a  and the turbine-side rotor  104   b  has a lower outer casing (outer member)  112  and a lower inner casing (inner member)  113 . 
         [0036]    For ease of explanation,  FIG. 2  does not show components other than the upper casing  105   a,  the lower casing  105   b,  and the centering mechanism  1 . 
         [0037]    As shown in  FIG. 2 , the centering mechanism  1  according to this embodiment includes, as main components, a horizontal-direction positioning unit  2  which positions the upper inner casing  111  and the lower inner casing  113  in the horizontal direction (in the right-and-left direction in  FIG. 2 ), and vertical-direction positioning units  3  which position the upper inner casing  111  and the lower inner casing  113  in the vertical direction (in the up-and-down direction in  FIG. 2 ). 
         [0038]    The horizontal-direction positioning unit  2  includes a first horizontal-direction positioning unit  4  provided at the top (upper part in  FIG. 2 ) of the upper casing  105   a  and a second horizontal-direction positioning unit  5  provided at the bottom (lower part in  FIG. 2 ) of the lower casing  105   b.    
         [0039]    The first horizontal-direction positioning unit  4  has a through-hole  6  which is drilled in a thickness direction of the upper outer casing  110  and has a circular shape in plan view, a concave part  7  which is formed on the outer circumferential surface of the upper inner casing  111  and has a long-gutter-like elongated hole shape in the rotor axial direction in plan view, and a pin  8  which is to be inserted into the through-hole  6  and the concave part  7 . The through-hole  6  and the concave part  7  are formed to have gutter widths that are approximately the same as the outer diameter of the pin  8 . The cross-sectional shape of the pin  8  may be a shape obtained when parts of circular cross section are cut with two parallel chords. In that case, the pin  8  is formed such that the outer walls at the parallel chords of the pin  8  are fitted inside the inner walls of the concave part  7 . 
         [0040]    Similarly to the first horizontal-direction positioning unit  4 , the second horizontal-direction positioning unit  5  has a through-hole  6  which is drilled in a thickness direction of the lower outer casing  112  and has a circular shape in plan view, a concave part  7  which is formed on the outer circumferential surface of the lower inner casing  113  and has a long-gutter-like elongated hole shape in the rotor axial direction in plan view, and a pin  8  which is to be inserted into the through-hole  6  and the concave part  7 . 
         [0041]    Next, the vertical-direction positioning units  3  will be described with reference to  FIGS. 3 to 5 . 
         [0042]    The vertical-direction positioning units  3  are provided at both sides of the casing  105  (see  FIG. 1 ); specifically, they are provided near junctions of the upper casing  105   a  and the lower casing  105   b.  The vertical-direction positioning units  3  are provided on the inner circumferential surfaces located at upper-end side parts of the lower outer casing  112  and have a rectangular shape in plan view (see  FIG. 3 ). Each of the vertical-direction positioning units  3  includes a key gutter  10  having a rectangular shape in cross-sectional view (see  FIG. 4 ), a key  11  which is set (accommodated) in the key gutter  10  and reciprocates in the axial direction (of the rotor  104 ), and a gutter portion  12  which is provided on the outer circumferential surface located at an upper-end side part of the lower inner casing  113  and receives a part of the key  11  in a slidable manner. 
         [0043]    The key gutter  10  is formed to have approximately the same height as the key  11  (or to have a height slightly (somewhat) higher than the key  11 ), and the upper end of the key gutter  10  is an open end. The open end is closed when the upper casing  105   a  is placed on the lower casing  105   b . Further, the key gutter  10  is formed to have a width wider than the key  11 , so that the key  11  can reciprocate in the axial direction in the key gutter  10 . A female threaded part  10   a  is provided at the bottom face (face opposed to the open end) of the key gutter  10  into which is screwed a male screw part  18   a  provided at the tip of a key-securing bolt  18 , to be described later. 
         [0044]    As shown in  FIGS. 3 and 5 , the key  11  has a first member  13  which extends in a direction perpendicular to the axial direction and is located at an upstream side (high pressure side), a second member  14  which extends in a direction perpendicular to the axial direction and is located at a downstream side (low pressure side), and an oblique member  16  which extends in the axial direction and connects a low-pressure-side end face of the first member  13  and a high-pressure-side end face of the second member  14 . Each of the first member  13  and the second member  14  is a substantially square pole having approximately the same height as the key gutter  10  (or having a height slightly (somewhat) shorter than the key gutter  10 ). The oblique member  16  is a plate-like member which inclines downward from the upstream side (high pressure side) to the downstream side (low pressure side). 
         [0045]    The inclination angle of the oblique member  16  is set to an angle at which the upper inner casing  111  and the lower inner casing  113  naturally slide downward along the oblique member  16  by only the gravity acting on the upper inner casing  111  and the lower inner casing  113  (in short, an angle at which they move rightward in  FIG. 3 , in other words, an angle larger than a friction angle), in a state where the gas turbine  100  (see  FIG. 1 ) is stopped (in other words, in a state where gas does not affect upstream-side (high-pressure-side) end faces (left end faces in  FIG. 3 ) of the upper inner casing  111  and the lower inner casing  113  and downstream-side (low-pressure-side) end faces (right end faces in  FIG. 3 ) of the upper inner casing  111  and the lower inner casing  113 ). 
         [0046]    Note that this does not mean that the inclination angle is strictly set equal to or larger than the friction angle. Usually, in the inner casing and in the blade ring, the flow of working fluid imposes a load in the rotor axial direction, and, when the operation is started, the upper inner casing  111  and the lower inner casing  113  are quickly pushed downstream and seated at a given position (even if they are placed on a conventional horizontal key or even if they are positioned upstream in an unbalanced state due to play in a mounting gutter, for example, when the operation is started, they are seated at a given downstream position against the friction). It is preferable to set the inclination angle in a direction in which they slide downstream because it helps them to be seated. It is more preferable if the inclination angle is equal to or larger than the friction angle because they can be seated at the given position in a stable manner from the start of the operation. 
         [0047]    A through hole  17  is drilled in the height direction approximately at the center part in the cross-sectional view of each of the first member  13  and the second member  14 . The key-securing bolt  18  is inserted into the through hole  17  and the male screw part  18   a  of the key-securing bolt  18  is tightened into the female threaded part  10   a,  so that the key  11  is sandwiched between a bolt head  18   b  of the key-securing bolt  18  and the bottom face of the key gutter  10  and is secured to the lower outer casing  112 . 
         [0048]    The through hole  17  is drilled such that its width in the axial direction is larger than in a direction perpendicular to the axial direction and has an elongated hole shape extending in the axial direction in plan view. The through hole  17  is formed such that the key  11  can reciprocate in the axial direction when the key-securing bolt  18  is loosened. 
         [0049]    Further, female threaded parts  20  which are screwed with male screw parts  19   a  provided at the tips of key position adjusting bolts  19  are provided at a high-pressure-side end face of the first member  13  and a low-pressure-side end face of the second member  14 . With bolt heads  19   b  of the key position adjusting bolts  19  being brought into contact with the side faces of the key gutter  10 , one of the key position adjusting bolts  19  is tightened and the other one of the key position adjusting bolts  19  is loosened, thereby allowing the key  11  to move in the axial direction. 
         [0050]    The gutter portion  12  is a gutter for receiving the oblique member  16  of the key  11  and is formed to have the same inclination angle as the oblique member  16 . 
         [0051]    Next, a description will be given of a procedure for adjusting the position of the upper inner casing  111  and the lower inner casing  113  in the vertical direction, performed by using the vertical-direction positioning units  3 , having the above-described structures. 
         [0052]    First, the key-securing bolts  18  are loosened to produce gaps between lower end faces of the bolt heads  18   b  and upper end faces of the key  11 . 
         [0053]    Then, in order to position the lower inner casing  113  at a desired position in the vertical direction, one of the key position adjusting bolts  19  is loosened and the other one of the key position adjusting bolts  19  is tightened to move the key  11  in the axial direction. The lower inner casing  113  is thus moved in the direction perpendicular to the axial direction (i.e., in the vertical direction). 
         [0054]    When the lower inner casing  113  is moved to the desired position, the key position adjusting bolts  19  are turned to be loosened such that the bolt heads  19   b  press the side faces of the key gutter  10 . Therefore, the key  11  is fixed so as to be prevented from moving in the axial direction. 
         [0055]    Lastly, the key-securing bolts  18  are turned to be tightened to completely (firmly) fix the key  11  to the lower outer casing  112 . 
         [0056]    According to the centering mechanism  1  of this embodiment, the key  11  is only moved in the key gutter  10  in the axial direction, so that the lower inner casing  113  is moved along the oblique member  16  provided for the key  11 , in the direction perpendicular to the axial direction (i.e., in the vertical direction) in a non-stepwise manner. 
         [0057]    Therefore, it is possible to easily and quickly position the upper inner casing  111  and the lower inner casing  113  in the vertical direction, to improve the efficiency of the centering work, and to reduce the work time. 
         [0058]    Unlike the conventional technology, it is unnecessary to prepare a new key (liner) every time the centering work is performed. Therefore, the cost and the work time required for the centering work can be substantially reduced. 
         [0059]    The inclination angle of the oblique member  16  is set such that low-pressure-side end faces  111   a  and  113   a  of the upper inner casing  111  and the lower inner casing  113  are brought into contact with (are pressed against) high-pressure-side end faces  110   a  and  112   a  of the upper outer casing  110  and the lower outer casing  112 , in a state where the gas turbine  100  (see  FIG. 1 ) is stopped or in a state where the gas pressure is low immediately after starting of operation. In other words, the inclination angle of the oblique member  16  is set to produce a state where the low-pressure-side end faces of the upper inner casing  111  and the lower inner casing  113  and the high-pressure-side end faces of the upper outer casing  110  and the lower outer casing  112  are always sealed. 
         [0060]    Accordingly, the upper inner casing  111  and the lower inner casing  113  can be prevented from being moved in the axial direction (more specifically, toward the high pressure side in the axial direction), and the upper inner casing  111  and the lower inner casing  113  can be maintained at the desired position where the upper inner casing  111  and the lower inner casing  113  are always centered. 
         [0061]    Note that the centering mechanism of the present invention has been described with reference, for example, to the gas turbine shown in  FIG. 1 . Application of the centering mechanism of the present invention is not limited to the gas turbine; it can be applied to centering of a blade ring or an inner casing in a rotary machine such as a compressor.