Abstract:
It is an object of the present invention to provide a sealing apparatus having high sealing performance, entailing a low cost, and satisfactory in assembly characteristics. The sealing apparatus is a differential pressure-responsive sealing apparatus which is inserted between seal grooves formed in the side surfaces of outlet flange portions of adjacent combustor transition pipes to seal clearance between the side surfaces, comprising: a minimum required number of seal pieces connected in the longitudinal direction for imparting flexibility, the seal piece comprising a heat resistant, wear resistant material, and having a pair of sealing ridges each having an arcuate surface contacting the wall surface of each seal groove.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a sealing apparatus, and a gas turbine having this apparatus. More particularly, the invention relates to a sealing apparatus for sealing clearance between assembly components which changes owing to external force or thermal expansion or the like, for example, a sealing apparatus suitable as a seal between gas turbine combustors at their outlets. 
     2. Description of the Related Art 
     Generally, a gas turbine has an air compressor (may hereinafter be referred to as “compressor”), a combustor, and a turbine as main constituents. The combustor is disposed between the compressor and the turbine connected together directly by a rotating shaft. Air to serve as a working fluid is taken into the compressor in accordance with the rotation of the rotating shaft, and compressed there. The compressed air is introduced into the combustor, and burned with a fuel. The resulting combustion gas at a high temperature and a high pressure is ejected to the turbine to drive the rotating shaft as well as the turbine rotationally. Such a gas turbine is effectively used as a drive source for a power generator or the like which is connected to the front end of the rotating shaft. 
     In recent years, a low NO x  (premix) combustor has been used frequently from the aspect of pollution control over air pollution, etc. With the low NO x  (premix) combustor, a larger amount of combustion air is needed for decreasing NO x . Thus, a sealing apparatus is applied to each part of the gas turbine to manage air leakage strictly. 
     Examples of the sealing apparatus used as a seal between gas turbine combustors at the outlets of the combustors are shown in  FIGS. 5 to 7 . 
       FIG. 5  shows a brush seal  102  used as a seal between gas turbine combustors at the outlets of the combustors (i.e., a side seal). The brush seal  102  comprises a rail  102   a  to be fitted into a groove formed in a wall portion of one of transition pipes, and a wire brush  102   b  whose leading end is pressed against the back of a flange portion of the other transition pipe and which is composed of wires densely planted in the rail  102   a . The brush seal  102  is adapted to reduce air leakage from the casing side to the turbine side. 
       FIG. 6  shows a so-called worm seal  104  comprising many I-shaped punched-out pieces  104   a  tied in a row with the use of a flexible sheet  104   b . The worm seal  104  seals clearance between flange portions of adjacent transition pipes, thereby reducing air leakage from the casing side to the turbine side. The worm seal  104  serves for sealing when it is inserted into grooves formed in the adjacent transition pipes, and a pair of arcuate projections  104   ab  of the worm seal  104  are pressed against the wall surfaces of the grooves under a differential pressure between the casing and the interior of the combustor. 
       FIG. 7  shows a sealing apparatus for sealing clearance between connecting surfaces (opposing surfaces) of the end surface of one component  106 A and the end surface of other component  106 B. This sealing apparatus is mounted in a space portion between groove-shaped stepped portions formed in the connecting surfaces. The sealing apparatus comprises a sealing body  107  composed of a support portion  107 A having a first seal protrusion  107 A 1  in intimate contact with a second step surface  106 A 2  of the one component  106 A and a second seal protrusion  107 A 2  in intimate contact with a second step surface  106 B 2  of the other component  106 B, and a holding portion  107 B formed to be upright on the support portion  107 A; a first seal member  108  having a second side portion  108 C secured to the side surface of the holding portion  107 B, a curved elastic portion  108 B, and an inclined first side portion  108 A, the second side portion  108 C, the elastic portion  108 B, and the first side portion  108 A being formed in the shape of a U-plate; a second seal member  109  disposed on the side surface of the holding portion  107 B in symmetrical relation with the first seal member  108 , having a second side portion  109 C secured to the side surface of the holding portion  107 B, and having nearly the same configurational requirements as those of the first seal member  108 ; a first seal surface  108 A 1  in intimate contact with a first step surface  106 A 1  of the one component  106 A at an outward surface of an end portion of the first side portion  108 A of the first seal member  108 ; and a second seal surface  109 A 1  in intimate contact with a first step surface  106 B 1  of the other component  106 B at an outward surface of an end portion of the first side portion  109 A of the second seal member  109 . As noted above, end sides of the second side portions  108 C and  109 C are secured to the holding portion  107 B. In this manner, the assembly clearance between the components where a high temperature fluid flows, or the assembly clearance between the components involving vibrations can be always sealed (see JP-A-2005-76802). 
     However, the seal shown in  FIG. 5  has posed the problem that the deformation of the wire brush  102   b  at the time of combustor assembly and after operation of the gas turbine is marked, arousing a concern about deterioration of performance, so that the seal is difficult to apply to a low NO x  (premix) combustor. That is, the wire brush  102   b  may collapse or wear when the clearance changes at the time of combustor assembly, during operational vibrations, or at start or stoppage of the gas turbine. There has also been the problem that the cost for repair of the combustor increases because of replacement work necessitated by deformation after operation. 
     With the seal shown in  FIG. 6 , higher sealing performance than that of the brush seal  102  in  FIG. 5  has been confirmed. However, increases in processing man-hours and the number of the components have presented the problem of cost increases. 
     The sealing apparatus shown in  FIG. 7  has involved the problems that an increase in the number of the components results in a cost increase, and the sealing body  107  is integrally formed, and lacks flexibility, leading to poor assembly characteristics within a narrow space. 
     SUMMARY OF THE INVENTION 
     The present invention has been accomplished in light of the above-described situations. It is an object of the invention to provide a sealing apparatus having high sealing performance, entailing a low cost, and satisfactory in assembly characteristics, and a gas turbine equipped with the sealing apparatus. 
     A first aspect of the present invention is a differential pressure-responsive sealing apparatus which is inserted between seal grooves formed in end surfaces of adjacent members to seal clearance between the end surfaces, comprising: a minimum required number of seal pieces connected in a longitudinal direction for imparting flexibility, the seal piece comprising a heat resistant, wear resistant material, and having a pair of sealing ridges each having an arcuate surface contacting a wall surface of each seal groove. 
     A plurality of the seal pieces formed by machining or press-working may be connected by a flexible sheet joined to the seal pieces while spanning flat side surfaces of the seal pieces. 
     The seal pieces formed by press-working to have the sealing ridges of a semi-annular cross section may be laminated in a superposed manner, and a plurality of the seal pieces laminated may be tied together by wires each inserted into a circular hole formed by two of the sealing ridges opposing each other. 
     A sealing metal foil may be interposed between connecting surfaces of the seal pieces, i.e., the seal pieces connected in the longitudinal direction. 
     The present invention can realize the sealing apparatus which has a small number of the components, whose production is easy, and which is wear resistant. Thus, the sealing apparatus has high sealing performance, and can achieve cost reduction. Furthermore, the flexible sheet can impart moderate flexibility, and thus can enhance assembly characteristics. 
     A second aspect of the present invention is a gas turbine in which a seal between gas turbine combustors at outlets of the gas turbine combustors is constructed using the above-mentioned sealing apparatus. 
     The gas turbine of the present invention enables the performance of a low NO x  (premix) combustor to be fully exhibited. 
    
    
     
       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 configurational drawing of essential parts of a gas turbine showing Embodiment 1 of the present invention; 
         FIG. 2  is a perspective view of essential parts of a sealing apparatus in the gas turbine; 
         FIG. 3  is a plan view of a sealing apparatus showing Embodiment 2 of the present invention; 
         FIG. 4  is a configurational drawing of a sealing apparatus showing Embodiment 3 of the present invention; 
         FIG. 5  is a configurational drawing of a conventional brush seal; 
         FIG. 6  is a configurational drawing of a conventional worm seal; and 
         FIG. 7  is a configurational drawing of a conventional further different sealing apparatus. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A sealing apparatus, and a gas turbine using the apparatus, according to the present invention will be described in detail by the following embodiments with reference to the accompanying drawings. 
     Embodiment 1 
       FIG. 1  is a schematic configurational drawing of essential parts of a gas turbine showing Embodiment 1 of the present invention.  FIG. 2  is a perspective view of essential parts of a sealing apparatus in the gas turbine. 
     As shown in  FIG. 1 , a gas turbine has a plurality of (e.g.,  16 ) combustors  1  of a low NO x  (premix) type arranged around a main shaft (rotating shaft; not shown). In each combustor  1 , a fuel F injected from fuel nozzles  3  provided adjacent to a combustor inner tube  2 , and compressed air PA ejected from an air compressor (will hereinafter be referred to simply as a compressor)  4  and introduced to the upstream side of the combustor inner tube  2  are mixed. Then, the mixture is burned in a combustion region on the downstream side of the combustor inner tube  2  or the upstream side of a combustor transition pipe  5 , and is introduced into a turbine  6  as a high temperature, high pressure combustion gas CG. In the turbine  6 , this combustion gas CG is sequentially passed through and expanded by a plurality of turbine stages each comprising a stationary blade  7  and a moving blade  8  to generate power, thereby driving the compressor  4  as well as outputting a surplus drive force to the outside. 
     The ratio between the compressed air PA and the fuel F (air-fuel ratio) introduced into the combustor inner tube  2  needs to be controlled to an optimal value in conformity with the operating state of the gas turbine (i.e., the amount of the fuel introduced). For this purpose, not all of the compressed air PA is introduced into the combustion region of the combustor  1 , but part of the compressed air PA is bypassed and flowed from a casing  9  into the combustor transition pipe  5 . A bypass valve  10  is provided for this purpose and, by its action, part of the compressed air PA is flowed and supplied into the combustor transition pipe  5  through an opening of a bypass pipe  11  provided within the casing  9 . 
     In the present embodiment, a sealing apparatus  20  as a seal between the combustors (side seal) is interposed between outlet flange portions  5   a  and  5   a  of the adjacent combustor transition pipes  5 . That is, seal grooves  5   b  of a rectangular cross section are formed to oppose each other, in the side walls of the adjacent combustor transition pipes  5 . The sealing apparatus  20  is loosely fitted between these seal grooves  5   b  and  5   b.    
     The sealing apparatus  20  comprises a plurality of (2 to 4; in the illustrated example, 3 or more) seal pieces  21  of the same shape connected in the longitudinal direction, as shown in  FIG. 2 . Concretely, a sealing metal foil  22  is interposed between connecting surfaces of the respective seal pieces  21 , and the seal pieces  21  are coupled by a sheet  23  which is spot-welded (W) to the respective seal pieces  21  while spanning their flat side surfaces, and which is shorter than the seal piece  21  and has flexibility. 
     On the side surface of each seal piece  21  on the side opposite to the flat side surface thereof, sealing ridges  24  of a semicircular cross section extend in the longitudinal direction at right and left portions of the seal piece  21  in the drawing. The seal piece  21  is manufactured by machining or press-working a heat resistant, wear resistant alloy material such as Highness-25 (commercial name). The seal piece  21  may be provided with a wear resistant coating (chromium carbide or the like), as is the aforementioned seal groove  5   b . The length of the sealing apparatus  20  is set to be nearly equal to the height of the outlet flange portion  5   a  of the combustor transition pipe  5 . The above-mentioned sheet  23  is manufactured from the same material as that for the seal piece  21 . 
     Because of the above features, the sealing apparatus  20  is inserted into the seal grooves  5   b  between the outlet flange portions  5   a  of the adjacent combustor transition pipes  5 , after the combustors  1  are assembled to the gas turbine body. During operation of the gas turbine, as shown in the blow-off area of  FIG. 1 , the seal piece  21  of the sealing apparatus  20  is pressed against the wall surfaces of the seal grooves  5   b  under the differential pressure between the casing  9  and the combustor  1  (see an open thick arrow in the drawing), whereby leaking air (see thin arrows in the drawing) between the adjacent outlet flange portions  5   a  is sealed up. 
     On this occasion, the pair of sealing ridges  24  of the seal piece  21  contact the wall surfaces of the adjacent seal grooves  5   b  such that one sealing ridge contacts one wall surface. Thus, even if displacement between the adjacent outlet flange portions  5   a  occurs in the flowing direction of leaking air because of deformation due to thermal expansion, the contact on the arcuate surface is maintained, and wear or the like attributed to contact of the edge portion is effectively avoided. 
     According to the present embodiment, as described above, the sealing apparatus  20  can be realized which has a small number of the components, whose production is easy, and which is wear resistant. Thus, it has high sealing performance, and can achieve cost reduction, and is optimal when used in a low NO x  (premix) combustor. Furthermore, the flexible sheet  23  can impart moderate flexibility, thus making it possible to enhance assembly characteristics within a narrow space. 
     The interposition of the metal foil  22  is not compulsory. Instead of the spot welding W, other joining means, such as brazing, may be employed. 
     Embodiment 2 
       FIG. 3  is a plan view of a sealing apparatus showing Embodiment 2 of the present invention. 
     This is an embodiment in which the seal pieces  21  in Embodiment 1 are arranged symmetrically on both surfaces of the sheet  23 . The sealing apparatus according to this embodiment can be used as a sealing apparatus between the components when the flowing direction of leaking air is reversed in the seal groove  5   b.    
     Embodiment 3 
       FIG. 4  is a configurational drawing of a sealing apparatus showing Embodiment 3 of the present invention. 
     This is an embodiment in which seal pieces  21 A as in Embodiment 1, formed by press-working to have sealing ridges  24 A of a semi-annular cross section, are laminated in a superposed manner by spot welding W, and a plurality of the resulting laminates are tied (connected) together in the longitudinal direction by two wires  25 . That is, each wire  25  is inserted into the circular hole formed by the two sealing ridges  24 A opposing each other. 
     According to the present embodiment, like Embodiment 1, the sealing apparatus  20  can be realized which has a small number of the components, whose production is easy, and which is wear resistant. Thus, it has high sealing performance, and can achieve cost reduction. Since the core material is the wire  25 , moreover, moderate flexibility can be imparted, and assembly characteristics can also be enhanced. 
     While the present invention has been described by the above embodiments, it is to be understood that the invention is not limited to these embodiments, but may be varied in many other ways. For example, the sealing apparatus according to the present invention can be applied not only to a sealing apparatus at the outlets of gas turbine combustors, but also to a sealing apparatus for an assembly clearance between components for flow of other fluid, or an assembly clearance between components involving vibrations. 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 appended claims.