COMBUSTOR AND GAS TURBINE

Abstract

The present invention is a combustor provided with a combustor transition pipe connected to a turbine while interposing a transition pipe seal in between, including a flange portion provided at an end portion on a downstream side in a fluid flow direction of the combustor transition pipe, the flange portion projecting to radially inside and extending in a circumferential direction. The flange portion includes a pin hole into which a pin to position the transition pipe seal is inserted, a circumferential slit portion either extending within a range in a radial direction where the pin hole is formed or being located on radially outside of the pin hole and extending in the circumferential direction, and a hole portion on which part of the circumferential slit portion abuts.

Claims

1. A combustor provided with a combustor transition pipe connected to a turbine while interposing a transition pipe seal in between, comprising, a flange portion provided at an end portion on a downstream side in a fluid flow direction of the combustor transition pipe, the flange portion projecting to radially inside and extending in a circumferential direction, wherein the flange portion includes a pin hole into which a pin to position the transition pipe seal is inserted, a circumferential slit portion either extending within a range in a radial direction where the pin hole is formed or being located on radially outside of the pin hole and extending in the circumferential direction, and a hole portion on which part of the circumferential slit portion abuts.

2. The combustor according to claim 1, wherein the flange portion includes a plurality of radial slit portions each abutting on a rim on the radially inside of the flange portion and extending in the radial direction, the radial slit portions are formed symmetrically in the circumferential direction with respect to the pin hole, and each radial slit portion is formed at a predetermined distance away in the circumferential direction from the pin hole, a plurality of the circumferential slit portions are formed symmetrically in the circumferential direction with respect to the pin hole, and each circumferential slit portion is formed such that one end of the circumferential slit portion is connected to an end portion on the radially outside of the corresponding radial slit portion, and the circumferential slit portion extends in the circumferential direction and in a direction away from the pin hole, and a plurality of the hole portions are formed symmetrically in the circumferential direction with respect to the pin hole, and such that another end portion of each circumferential slit portion abuts on the corresponding hole portion.

3. The combustor according to claim 2, wherein the flange portion includes a curved slit portion formed into a curve and provided at a junction between each radial slit portion and the corresponding circumferential slit portion.

4. The combustor according to claim 1, wherein the flange portion includes a radial slit portion abutting on a rim on the radially inside of the flange portion and extending in the radial direction, and the radial slit portion is formed at the same position in the circumferential direction as the pin hole, such that one end of the radial slit portion abuts on pin hole.

5. The combustor according to claim 4, wherein a plurality of the circumferential slit portions are formed symmetrically in the circumferential direction with respect to the pin hole, and each circumferential slit portion is formed such that one end of the circumferential slit portion abuts on the pin hole, and a plurality of the hole portions are formed symmetrically in the circumferential direction with respect to the pin hole, and such that another end portion of each circumferential slit portion abuts on the corresponding hole portion.

6. A gas turbine comprising the combustor according to claim 3.

7. A gas turbine comprising the combustor according to claim 5.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0024] FIG. 1 is an explanatory diagram showing a structure of a gas turbine including a combustor according to a first embodiment of the present invention.

[0025] FIG. 2 is an explanatory diagram showing a structure of the combustor according to the first embodiment.

[0026] FIG. 3 is an explanatory diagram showing an end portion on a downstream side in a fluid flow direction of the combustor according to the first embodiment.

[0027] FIG. 4 is a partially enlarged diagram showing the end portion on the downstream side in the fluid flow direction of the combustor according to the first embodiment (an enlarged diagram of a portion IV in FIG. 2).

[0028] FIG. 5A is a partially enlarged diagram showing the end portion on the downstream side in the fluid flow direction of the combustor according to the first embodiment (an enlarged diagram of a portion V in FIG. 3).

[0029] FIG. 5B is a partially enlarged diagram showing a modified example of the end portion on the downstream side in the fluid flow direction of the combustor according to the first embodiment (an enlarged diagram of the portion V in FIG. 3).

[0030] FIG. 5C is a partially enlarged diagram showing a modified example of the end portion on the downstream side in the fluid flow direction of the combustor according to the first embodiment (an enlarged diagram of the portion V in FIG. 3).

[0031] FIG. 5D is a partially enlarged diagram showing a modified example of the end portion on the downstream side in the fluid flow direction of the combustor according to the first embodiment (an enlarged diagram of the portion V in FIG. 3).

[0032] FIG. 5E is a partially enlarged diagram showing a modified example of the end portion on the downstream side in the fluid flow direction of the combustor according to the first embodiment (an enlarged diagram of the portion V in FIG. 3).

DESCRIPTION OF EMBODIMENTS

[0033] An embodiment of a gas turbine including a combustor according to the present invention will be described below in detail with reference to the accompanying drawings. It is needless to say that the present invention is not limited only to the following embodiment, and various modifications are possible within a range not departing from the gist of the present invention.

First Embodiment

[0034] A structure of a gas turbine including a combustor according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 5A.

[0035] As shown in FIG. 1, a gas turbine 1 includes a compressor 11 which takes in and compresses outside air. A turbine 13 is provided, through the intermediary of a combustor 12, on a downstream side in a fluid flow direction (see arrows in FIG. 1) of the compressor 11. The compressed air generated by the compressor 11 is mixed with a fuel in the combustor 12 and then combusted. Combustion gas thus generated by the combustor 12 is expanded in the turbine 13 and used to rotate a rotor shaft (rotation shaft) 14.

[0036] The gas turbine 1 is juxtaposed to a power generator 2. The power generator 2 is provided coaxially with the rotor shaft 14 of the gas turbine 1. In other words, the power generator 2 is mechanically connected to the rotor shaft 14, whereby rotational motion of the rotor shaft 14 is transmitted to the power generator 2. Accordingly, thermal energy generated by the compressor 11 and the combustor 12 of the gas turbine 1 is converted into rotational kinetic energy for the rotor shaft 14 by the turbine 13, and the rotational kinetic energy is converted into electric energy by the power generator 2.

[0037] As shown in FIG. 2, the combustor 12 includes: a combustor outer pipe 21 to be connected to a not-illustrated housing; a combustor inner pipe 22 disposed inside the combustor outer pipe 21; and a combustor transition pipe 23 disposed on the downstream side in the fluid flow direction (see arrows in FIG. 2) of the combustor inner pipe 22 and connected to the turbine 13. The compressed air generated by the compressor 11 is passed through a gap between the combustor outer pipe 21 and the combustor inner pipe 22, and is supplied to a space S.sub.1 inside the combustor 12 (inside the combustor inner pipe 22 and the combustor transition pipe 23).

[0038] Moreover, the combustor 12 includes a pilot burner 24 provided with a pilot nozzle 24a, and premix burners 25 each provided with a premix nozzle 25a. The compressed air supplied into the combustor transition pipe 23 is mixed with the fuel injected from the pilot nozzle 24a and the premix nozzles 25a, and then ignited and brought into combustion by the pilot burner 24 and the premix burners 25.

[0039] Here, in the gas turbine 1, the combustors 12 are arranged in a circumferential direction (see FIG. 3) such that end portions on the downstream side in the fluid flow direction (on the right near side of the sheet in FIG. 3) of the combustor transition pipes 23 draw a circle.

[0040] The turbine 13 includes stator vanes 31 supported by the not-illustrated housing, and not-illustrated rotor vanes supported by the rotor shaft 14. The rotor vanes are arranged in a circumferential direction of the rotor shaft 14 and at multiple stages in an axial direction thereof. The flow of the combustion gas generated by the combustor 12 (the combustor transition pipe 23) is straightened by the stator vanes 31 at the respective stages of the turbine 13, and is converted into force in the circumferential direction by the not-illustrated rotor vanes, thereby rotating the rotor shaft 14.

[0041] As shown in FIGS. 3 and 4, a flange portion 41 that projects toward an external space (a space in the radially inside of the combustor 12 and of the turbine 13, the space being located on a lower side in FIGS. 3 and 4) S.sub.2 and extends in the circumferential direction is provided at an end portion on the downstream side (the right side in FIG. 4) in the fluid flow direction of the combustor transition pipe 23.

[0042] Meanwhile, as shown in FIG. 4, a flange portion 51 that extends in the fluid flow direction (the right-left direction in FIG. 4) toward the flange portion 41 of the combustor transition pipe 23 is provided at an end portion on an upstream side (the left side in FIG. 4) in the fluid flow direction of each shroud 32.

[0043] Here, the shrouds 32 are configured to support the radially inside and the radially outside of the stator vanes 31 in the turbine 13. The shrouds 32 for the stator vanes 31 disposed on the uppermost stream side in the fluid flow direction are opposed to the combustor transition pipe 23. Note that FIG. 4 illustrates a junction between the combustor transition pipe 23 and the shroud 32 on the radially inside of the stator vane 31.

[0044] As shown in FIG. 4, a transition pipe seal 15 is provided at the junction between the combustor 12 and the turbine 13. The transition pipe seal 15 is disposed on the radially inside at the end portion on the downstream side in the fluid flow direction of the combustor transition pipe 23, and extends in the circumferential direction along the flange portion 41 of the combustor transition pipe 23 and the flange portion 51 of the shroud 32.

[0045] The transition pipe seal 15 includes: a first radial extension portion 61 located on one side (the upstream side in the fluid flow direction and the left side in FIG. 4) of the flange portion 41 of the combustor transition pipe 23 and extending in the radial direction (the vertical direction in FIG. 4); a second radial extension portion 62 located on another side (the downstream side in the fluid flow direction and the right side in FIG. 4) of the flange portion 41 of the combustor transition pipe 23 and extending in the radial direction; and a connection portion 63 which connects rims on the radially inside (the lower side in FIG. 4) of the first radial extension portion 61 and of the second radial extension portion 62 to each other.

[0046] In other words, the first radial extension portion 61 and the second radial extension portion 62 of the transition pipe seal 15 are disposed in such a way as to sandwich the flange portion 41 of the combustor transition pipe 23 along the fluid flow direction (the axial direction of the rotor shaft 14). Thus, a position in the fluid flow direction of the transition pipe seal 15 is determined by the first radial extension portion 61 and the second radial extension portion 62.

[0047] Moreover, the transition pipe seal 15 includes: a first axial extension portion 64 and a second axial extension portion 65 projecting from the second radial extension portion 62 to the other side (the downstream side in the fluid flow direction). The first axial extension portion 64 is located on the radially outside (the upper side in FIG. 4) of the flange portion 51 of the shroud 32, and the second axial extension portion 65 is located on the radially inside of the flange portion 51 of the shroud 32.

[0048] In other words, the first axial extension portion 64 and the second axial extension portion 65 of the transition pipe seal 15 are disposed in such a way as to sandwich the flange portion 51 of the shroud 32 along the radial direction. Thus, a position in the radial direction of the transition pipe seal 15 is determined by the first axial extension portion 64 and the second axial extension portion 65.

[0049] Furthermore, the transition pipe seal 15 is brought into pinned connection to the combustor transition pipe 23 (the flange portion 41) by using a positioning pin 16. The transition pipe seal 15 is provided with a round hole 66 into which the positioning pin 16 is insertable, and the flange portion 41 is provided with an elongated hole (a pin hole) 42 which extends in the radial direction and into which the positioning pin 16 is insertable. Positioning in the circumferential direction (the front-back direction of the sheet surface in FIG. 4) of the transition pipe seal 15 relative to the combustor transition pipe 23 is established by inserting the positioning pin 16 into the round hole 66 in the transition pipe seal 15 and into the elongated hole 42 in the flange portion 41 of the combustor transition pipe 23, i.e., bringing the transition pipe seal 15 into the pinned connection to the combustor transition pipe 23 (the flange portion 41) by using the positioning pin 16.

[0050] In other words, the transition pipe seal 15 is provided between the combustor transition pipe 23 disposed on the lowermost stream side in the fluid flow direction of the combustor 12 and the shroud 32 of the stator vane 31 disposed on the uppermost stream side in the fluid flow direction of the turbine 13. The transition pipe seal 15 prevents the combustion gas, which flows from the combustor 12 to the turbine 13, from being leaked from a fluid flow passage (the space inside the combustor 12 and the turbine 13) S.sub.1 for the combustion gas to an external space (the space outside the combustor 12 and the turbine 13) S.sub.2.

[0051] Here, in the flange portion 41 of the combustor transition pipe 23, there are a high-temperature region (a region above a boundary B in FIG. 4) T.sub.1 where a material temperature is likely to reach a high temperature, and a low-temperature region (a region below the boundary B in FIG. 4) T.sub.2 where the material temperature never reaches a high temperature. As a consequence, the flange portion 41 is likely to cause a thermal stress attributed to a difference in temperature between the high-temperature region T.sub.1 and the low-temperature region T.sub.2. Hence, stress concentration is likely to occur on a rim 42a on one side (a rim on the lower side in FIG. 4) of the elongated hole 42.

[0052] In this case, the high-temperature region T.sub.1 is a region which is located in the vicinity of an inner peripheral surface 23a exposed to the high-temperature combustion gas while the gas turbine 1 is in operation, and to which the heat is transmitted from the inner peripheral surface 23a. The high-temperature region T.sub.1 is also likely to be exposed to the combustion gas flowing into a space S.sub.3 between the combustor transition pipe 23 and the shroud 32. Meanwhile, the low-temperature region T.sub.2 is a region in contact with the transition pipe seal 15, which is not exposed to the combustion gas flowing into the space S.sub.3 between the combustor transition pipe 23 and the shroud 32.

[0053] Accordingly, in the gas turbine 1 including the combustor 12 of this embodiment, the flange portion 41 is provided with slits 43 and stop holes (hole portions) 44 collectively functioning as a stress relaxation structure to be described below (see FIG. 5A), and is thus configured to relax the thermal stress in the vicinity of the elongated hole 42 in the flange portion 41 of the combustor transition pipe 23, and to reduce cyclic fatigue caused by repeatedly operating and stopping the gas turbine 1.

[0054] As shown in FIG. 5A, the flange portion 41 is provided with the slits 43 and the stop holes 44, which are located in the vicinity of the elongated hole 42 and are formed substantially symmetrical in the circumferential direction (the right-left direction in FIG. 5A) with respect to the elongated hole 42.

[0055] Each slit 43 includes: a radial slit 43a (a radial slit portion) abutting on a rim 41a on the radially inside (the lower side in FIG. 5A) of the flange portion 41 and extending in the radial direction (the vertical direction in FIG. 5A); a curved slit (a curved slit portion) 43b connected to an end portion on the radially outside (an upper end portion in FIG. 5A) of the radial slit 43a and curved while changing its direction away from the elongated hole 42; and a circumferential slit (a circumferential slit portion) 43c connected to an end portion in the circumferential direction of the curved slit 43b and extending in the circumferential direction (a direction along the temperature boundary B).

[0056] Each stop hole 44 is formed at a position away by a predetermined distance in the circumferential direction from the elongated hole 42. Each circumferential slit 43c abuts on the inside of the corresponding stop hole 44.

[0057] In other words, the slit 43 is formed such that the radial slit 43a is continuous with the circumferential slit 43c via the curved slit 43b, and that the end portion on one side of the slit 43 abuts on the rim 41a of the flange portion 41 while the end portion on the other side thereof abuts on the stop hole 44.

[0058] Each circumferential slit 43c is formed substantially at the same position in the radial direction as a rim 42b on the radially outside (the upper side in FIG. 5A) of the elongated hole 42. Needless to say, the circumferential slit portions of the present invention are not limited to this configuration. The circumferential slit portions may be formed at the same position in the radial direction (within a range in the radial direction where the elongated hole 42 is formed) as any other portion of the elongated hole 42, or at a position located on the radially outside of the elongated hole 42.

[0059] The operation of the gas turbine including the combustor according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 5A.

[0060] When the gas turbine 1 starts operation, the outside air is taken from a not-illustrated air intake port into the compressor 11, and the compressed air is generated by the compressor 11 (see FIG. 1). The compressed air is supplied to the combustor 12, and is mixed with the fuel and then combusted. The combustion gas generated by the combustion is sent to the turbine 13. The combustion gas is expanded in the turbine 13 and used to rotate the rotor shaft 14. Thus, the power generator 2 generates the power.

[0061] As described above, in this embodiment, the thermal energy generated by the compressor 11 and the combustor 12 of the gas turbine 1 is converted into the rotational kinetic energy by the turbine 13, and the rotational kinetic energy is converted into the electric energy by the power generator 2.

[0062] Moreover, the combustor of this embodiment is provided with the slits 43 and the stop holes 44 collectively as the stress relaxation structure (see FIG. 5A), which relax the thermal stress occurring in the vicinity of the elongated hole 42 (the rim 42a) in the flange portion 41 of the combustor transition pipe 23 while the gas turbine 1 is in operation, and reduce the cyclic fatigue (low-cycle fatigue) at the rim 42a caused by repeatedly operating and stopping the gas turbine 1.

[0063] While the gas turbine 1 is in operation, a difference in thermal strain (thermal stress) caused by the difference in temperature between the high-temperature region T.sub.1 and the low-temperature region T.sub.2 in the flange portion 41 occurs in a continuous material. This difference in thermal strain (the thermal stress) is relaxed by the slits 43. Meanwhile, in the vicinity of the elongated hole 42 in the flange portion 41, the thermal strain (the thermal stress) in which the low-temperature region T.sub.2 is pulled by the high-temperature region T.sub.1 is transmitted in a range between the slits 43 (a range at a distance (W+W) between the slits 43 in FIG. 5A).

[0064] Accordingly, as compared to a conventional flange portion (which is not provided with the slits 43 or the stop holes 44), this flange portion brings about a smaller difference in thermal strain and has a smaller range of transmission of the thermal strain (the thermal stress) to the rim 42a of the elongated hole 42. Thus, the thermal stress occurring on the rim 42a of the elongated hole 42 is relaxed.

[0065] Here, the flange portion 41 is provided with a sufficiently large circumferential length L of each circumferential slit 43c and with a sufficiently large inside diameter D of each stop hole 44. Thus, the flange portion 41 is configured to avoid excessive stress concentration on the periphery of each stop hole 44. Moreover, by providing a sufficiently large curvature R to each curved slit 43b, the flange portion 41 is configured to avoid excessive stress concentration on the periphery of the curved slit 43b.

[0066] Note that in this embodiment, the slits 43 and the stop holes 44 are formed in the flange portion 41 to satisfy a relation expressed in the following Formula (1), so as to avoid the excessive stress concentration on the periphery of the stop holes 44 while relaxing the thermal stress on the rim 42a of the elongated hole 42:

(X×1/6)<(L×2+W×2)<(X×1/3)   Formula (1).

[0067] Here, X is a length in the circumferential direction of the flange portion 41 (see FIG. 3), L is a distance in the circumferential direction between each radial slit 43a and the corresponding stop hole 44 (the circumferential length of each circumferential slit 43c) (see FIG. 5A), and W is a distance in the circumferential direction from the center of the elongated hole 42 to each slit 43 (the radial slit 43a).

[0068] In this embodiment, the flange portion 41 of the combustor transition pipe 23 is provided with the slits 43 and the stop holes 44 collectively as the stress relaxation structure. Thus, the thermal stress in the vicinity of the elongated hole 42 in the flange portion 41 of the combustor transition pipe 23 is relaxed and the cyclic fatigue is thus reduced (see FIG. 5A).

[0069] For example, it is also possible to relax the thermal stress in the vicinity of the elongated hole 42 in the flange portion 41 of the combustor transition pipe 23 and to reduce the cyclic fatigue by providing the flange portion 41 of the combustor transition pipe 23 with any of stress relaxation structures shown below (see FIGS. 5B to 5E). Note that FIGS. 5B to 5E show modified examples of the stress relaxation structure in the flange portion 41 of the combustor transition pipe 23, in which constituents having the same functions and structures as those in the above-described embodiment will be denoted by the same reference signs and overlapping explanations thereof will be omitted as appropriate.

[0070] First, as shown in FIG. 5B, the flange portion 41 may be provided with slits 143 and stop holes 144 collectively as the stress relaxation structure.

[0071] The slits 143 include: a radial slit 143a abutting on the rim 41a on the radially inside (the lower side in FIG. 5B) of the flange portion 41 and extending in the radial direction (the vertical direction in FIG. 5B); and circumferential slits 143b each extending in the circumferential direction at the same position (within the range in the radial direction where the elongated hole 42 is formed) in the radial direction as the rim 42b on the radially outside (the upper side in FIG. 5B) of the elongated hole 42. Each stop hole 144 is formed at a position away by a predetermined distance in the circumferential direction from the elongated hole 42. Each circumferential slit 143b abuts on the inside of the corresponding stop hole 144.

[0072] The radial slit 143a is formed at the same position in the circumferential direction (the right-left direction in FIG. 5B) as the elongated hole 42. One end (which is an end portion on the radially outside and is an upper end portion in FIG. 5B) of the radial slit 143a is formed to extend to the rim 42a on the radially inside of the elongated hole 42 (to abut on the elongated hole 42).

[0073] One end of each of the circumferential slits 143b is formed to abut on the elongated hole 42. The circumferential slits 143b are formed substantially symmetrical in the circumferential direction with respect to the elongated hole 42 in such a way as to extend from the elongated hole 42 to one side in the circumferential direction and to the other side in the circumferential direction, respectively. Another end of each of the circumferential slits 143b is formed to abut on the corresponding stop hole 144.

[0074] By providing the slits 143 and the stop holes 144 collectively as the stress relaxation structure as described above, the thermal stress on the flange portion 41 (the rim 42a on the radially inside of the elongated hole 42) is relaxed while the gas turbine 1 is in operation, and the cyclic fatigue caused by repeatedly operating and stopping the gas turbine 1 is reduced as a consequence.

[0075] To be more precise, the rim 42a on the radially inside of the elongated hole 42 is split in the circumferential direction by the radial slit 143a. For this reason, no large thermal stress occurs in the flange portion 41 as a result of being pulled to the two sides in the circumferential direction due to the difference in thermal strain caused by the difference in temperature between the high-temperature region T.sub.1 and the low-temperature region T.sub.2 of the flange portion 41.

[0076] In the meantime, while the gas turbine 1 is in operation, the difference in thermal strain (the thermal stress) caused by the difference in temperature between the high-temperature region T.sub.1 and the low-temperature region T.sub.2 in the flange portion 41 occurs within a continuous material. This difference in thermal strain (thermal stress) is relaxed by the slits 143. Specifically, the high-temperature region T.sub.1 and the low-temperature region T.sub.2 of the flange portion 41 are split by the slits 143, whereby each of the regions (the high-temperature region T.sub.1 and the low-temperature region T.sub.2) exhibits free thermal expansion. Accordingly, the thermal stress liable to occur in the vicinity of the elongated hole 42 as a consequence of the low-temperature region T.sub.2 being pulled by the high-temperature region T.sub.1 is relaxed in the flange portion 41.

[0077] In the meantime, as shown in FIG. 5C, the flange portion 41 may be provided with slits 243 collectively as the stress relaxation structure.

[0078] The slits 243 include radial slits 243a, 243b, and 243c each extending in the radial direction (the vertical direction in FIG. 5C) and abutting on the rim 41a on the radially inside (the lower side in FIG. 5C) of the flange portion 41. Sets of the radial slits 243a, 243b, and 243c are provided symmetrically in the circumferential direction (the right-left direction in FIG. 5C) with respect to the elongated hole 42. The radial slits 243a, 243b, and 243c are arranged in the circumferential direction in the vicinity of the elongated hole 42. In the flange portion 41, first radial slits 243a, second radial slits 243b, and third radial slits 243c are symmetrically arranged in this order from near the elongated hole 42, respectively.

[0079] By providing the slits 243 as the stress relaxation structure as described above, the thermal stress on the flange portion 41 (the rim 42a on the radially inside of the elongated hole 42) is relaxed while the gas turbine 1 is in operation, and the cyclic fatigue caused by repeatedly operating and stopping the gas turbine 1 is reduced as a consequence.

[0080] To be more precise, while the gas turbine 1 is in operation, the thermal stress in which the low-temperature region T.sub.2 is pulled by the high-temperature region T.sub.1 is transmitted within a range between the first radial slits 243a in the vicinity of the elongated hole 42 of the flange portion 41.

[0081] Accordingly, as compared to a conventional flange portion (which is not provided with the slits 243 (the first radial slits 243a)), this flange portion has a smaller range of transmission of the thermal stress to the rim 42a of the elongated hole 42. Thus, the thermal stress occurring on the rim 42a of the elongated hole 42 is relaxed.

[0082] Moreover, since the second radial slits 243b and the third radial slits 243c are provided, the thermal stress in which the low-temperature region T.sub.2 is pulled by the high-temperature region T.sub.1 is transmitted in small ranges between the respective slits (between each first radial slit 243a and the corresponding second radial slit 243b, and between each second radial slit 243b and the corresponding third radial slit 243c). In other words, the thermal stress in which the low-temperature region T.sub.2 is pulled by the high-temperature region T.sub.1 is dispersed in the spaces between the slits 243a, 243b, and 243c. As a consequence, no large thermal stress (stress concentration) occurs in any part of the flange portion 41.

[0083] Meanwhile, as shown in FIG. 5D, the flange portion 41 may be provided with slits 343 and stop holes 344 collectively as the stress relaxation structure.

[0084] The slits 343 abut on the rim 41a on the radially inside (the lower side in FIG. 5D) of the flange portion 41 and extend in directions different from the radial direction (the vertical direction in FIG. 5D) and the circumferential direction (the right-left direction in FIG. 5D), and are provided symmetrical in the circumferential direction with respect to the elongated hole 42. In other words, the slits 343 are symmetrically arranged in such a way as to recede radially outward (upward in FIG. 5D) from the rim 41a, and to recede from each other (from the elongated hole 42) in the circumferential direction (in a spreading manner). Each stop hole 344 is formed at a position away by a predetermined distance in the circumferential direction from the elongated hole 42. Each slit 343 abuts on the inside of the corresponding stop hole 344.

[0085] By providing the slits 343 and the stop holes 344 collectively as the stress relaxation structure as described above, the thermal stress on the flange portion 41 (the rim 42a on the radially inside of the elongated hole 42) is relaxed while the gas turbine 1 is in operation, and the cyclic fatigue caused by repeatedly operating and stopping the gas turbine 1 is reduced as a consequence.

[0086] To be more precise, while the gas turbine 1 is in operation, the thermal stress in which the low-temperature region T.sub.2 is pulled by the high-temperature region T.sub.1 is transmitted within a range between the symmetrically arranged slits 343.

[0087] Accordingly, as compared to a conventional flange portion (which is not provided with the slits 343 or the stop holes 344), this flange portion has a smaller range of transmission of the thermal stress to the rim 42a of the elongated hole 42. Thus, the thermal stress occurring on the rim 42a of the elongated hole 42 is relaxed.

[0088] Moreover, since the stop holes 344 are provided, no large stress concentration occurs at an end portion on the radially outside of each slit 343.

[0089] In the meantime, as shown in FIG. 5E, the flange portion 41 may be provided with slits 443 and stop holes 444 collectively as the stress relaxation structure.

[0090] Each slit 443 includes: a radial slit 443a abutting on the rim 41a on the radially inside (the lower side in FIG. 5E) of the flange portion 41 and extending in the radial direction (the vertical direction in FIG. 5E); and a curved slit 443b connected to an end portion on the radially outside (an upper end portion in FIG. 5E) of the radial slit 443a and curved while changing its direction to a direction away from the elongated hole 42. Each stop hole 444 is formed at a position away by a predetermined distance in the circumferential direction from the elongated hole 42. Each curved slit 443b abuts on the inside of the corresponding stop hole 444.

[0091] By providing the slits 443 and the stop holes 444 collectively as the stress relaxation structure as described above, the thermal stress on the flange portion 41 (the rim 42a on the radially inside of the elongated hole 42) is relaxed while the gas turbine 1 is in operation, and the cyclic fatigue caused by repeatedly operating and stopping the gas turbine 1 is reduced as a consequence.

[0092] To be more precise, while the gas turbine 1 is in operation, the thermal stress in which the low-temperature region T.sub.2 is pulled by the high-temperature region T.sub.1 is transmitted within a range between the slits 443 (the radial slits 443a and the curved slits 443b).

[0093] Accordingly, as compared to a conventional flange portion (which is not provided with the slits 443), this flange portion has a smaller range of transmission of the thermal stress to the rim 42a of the elongated hole 42. Thus, the thermal stress occurring on the rim 42a of the elongated hole 42 is relaxed.

[0094] Moreover, since the curved slits 443b are provided, no large stress concentration occurs at an end portion on the radially outside of each slit 443 (each radial slit 443a). Further, since the stop holes 444 are provided, no large stress concentration occurs at an end portion on the radially outside of each curved slit 443b.

REFERENCE SIGNS LIST

[0095] 1 GAS TURBINE

[0096] 2 POWER GENERATOR

[0097] 11 COMPRESSOR

[0098] 12 COMBUSTOR

[0099] 13 TURBINE

[0100] 14 ROTOR SHAFT (ROTATION SHAFT)

[0101] 15 TRANSITION PIPE SEAL

[0102] 16 POSITIONING PIN

[0103] 21 COMBUSTOR OUTER PIPE

[0104] 22 COMBUSTOR INNER PIPE

[0105] 23 COMBUSTOR TRANSITION PIPE

[0106] 23a INNER PERIPHERAL SURFACE OF COMBUSTOR TRANSITION PIPE

[0107] 24 PILOT BURNER

[0108] 24a PILOT NOZZLE

[0109] 25 PREMIX BURNER

[0110] 25a PREMIX NOZZLE

[0111] 31 STATOR VANE

[0112] 32 SHROUD

[0113] 41 FLANGE PORTION OF COMBUSTOR TRANSITION PIPE

[0114] 41a RIM ON RADIALLY INSIDE OF FLANGE PORTION

[0115] 42 ELONGATED HOLE IN FLANGE PORTION (PIN HOLE)

[0116] 42a RIM OF ELONGATED HOLE (RIM ON RADIALLY INSIDE)

[0117] 42b RIM OF ELONGATED HOLE (RIM ON RADIALLY OUTSIDE)

[0118] 43 SLIT OF FLANGE PORTION

[0119] 43a RADIAL SLIT (RADIAL SLIT PORTION)

[0120] 43b CURVED SLIT (CURVED SLIT PORTION)

[0121] 43c CIRCUMFERENTIAL SLIT (CIRCUMFERENTIAL SLIT PORTION)

[0122] 44 STOP HOLE IN FLANGE PORTION (HOLE PORTION)

[0123] 51 FLANGE PORTION OF SHROUD

[0124] 52 VERTICAL FLANGE PORTION OF SHROUD

[0125] 53 HORIZONTAL FLANGE PORTION OF SHROUD

[0126] 61 FIRST RADIAL EXTENSION PORTION OF TRANSITION PIPE SEAL

[0127] 62 SECOND RADIAL EXTENSION PORTION OF TRANSITION PIPE SEAL

[0128] 63 CONNECTION PORTION OF TRANSITION PIPE SEAL

[0129] 64 FIRST AXIAL EXTENSION PORTION OF TRANSITION PIPE SEAL

[0130] 65 SECOND AXIAL EXTENSION PORTION OF TRANSITION PIPE SEAL

[0131] 66 ROUND HOLE IN TRANSITION PIPE SEAL (PIN HOLE)

[0132] 143 SLIT OF FLANGE PORTION

[0133] 143a RADIAL SLIT (RADIAL SLIT PORTION)

[0134] 143b CIRCUMFERENTIAL SLIT (CIRCUMFERENTIAL SLIT PORTION)

[0135] 144 STOP HOLE IN FLANGE PORTION (HOLE PORTION)

[0136] 243 SLIT OF FLANGE PORTION

[0137] 243a FIRST RADIAL SLIT

[0138] 243b SECOND RADIAL SLIT

[0139] 243c THIRD RADIAL SLIT

[0140] 343 SLIT OF FLANGE PORTION

[0141] 344 STOP HOLE IN FLANGE PORTION (HOLE PORTION)

[0142] 443 SLIT OF FLANGE PORTION

[0143] 443a RADIAL SLIT

[0144] 443b CURVED SLIT

[0145] 444 STOP HOLE IN FLANGE PORTION