Patent Publication Number: US-2022228530-A1

Title: Transition piece, combustor, gas turbine, and gas turbine equipment

Description:
TECHNICAL FIELD 
     The present invention relates to a transition piece including a pipe in which fuel is combusted on an inner peripheral side, a combustor including the transition piece, a gas turbine, and gas turbine equipment. 
     Priority is claimed on Japanese Patent Application No. 2019-097550, filed May 24, 2019, the content of which is incorporated herein by reference. 
     BACKGROUND ART 
     A gas turbine includes a compressor that compresses air to generate compressed air; a combustor that combusts fuel in the compressed air; a turbine that is driven by combustion gas generated by the combustion of the fuel; and an intermediate casing. The compressor includes a compressor rotor and a compressor casing that covers the compressor rotor. The combustor includes a transition piece (or a combustion pipe) in which fuel is combusted on an inner peripheral side, and a burner that injects the fuel into the transition piece. The turbine includes a turbine rotor and a turbine casing that covers the turbine rotor. The compressor casing and the turbine casing are connected to each other via the intermediate casing. The compressed air that has been discharged from the compressor flows into the intermediate casing. The combustor is provided in the intermediate casing. 
     The following PTL 1 discloses a transition piece of a combustor. The transition piece includes a pipe in which fuel is combusted on an inner peripheral side; an acoustic damper forming an acoustic space on an outer peripheral side of the pipe; and a cooling air jacket forming a cooling air space on the outer peripheral side of the pipe. The acoustic damper is provided in an upstream portion of the pipe. The cooling air jacket is provided in a downstream portion of the pipe. Most of the compressed air in the intermediate casing flows into the combustor. In addition, some of the compressed air in the intermediate casing is bled out of the intermediate casing. The compressed air that has been bled is boosted by a boost compressor, and then flows into the cooling air space as enhanced cooling air. A cooling air flow path A and a cooling air flow path B are formed between an outer peripheral surface and an inner peripheral surface of the pipe. An acoustic hole penetrating through the pipe from the outer peripheral surface to the inner peripheral surface is formed in a portion of a panel forming the pipe, the acoustic damper being formed in the portion. 
     The cooling air flow path A includes an inlet that is open in a portion of the outer peripheral surface of the pipe, the cooling air jacket being formed in the portion, and an outlet that is open in a portion of the outer peripheral surface of the pipe, the acoustic damper and the cooling air jacket not being provided in the portion. The enhanced cooling air in the cooling air space flows into the cooling air flow path A. The enhanced cooling air exchanges heat with the pipe, which is exposed to the combustion gas, to cool the pipe in the process of passing through the cooling air flow path A. After the enhanced cooling air has exchanged heat with the pipe, the enhanced cooling air flows out into the intermediate casing from the outlet of the cooling air flow path A. 
     The cooling air flow path B includes an inlet that is open in a portion of the outer peripheral surface of the pipe, the acoustic damper and the cooling air jacket not being provided in the portion, and an outlet that is open in a portion of the outer peripheral surface of the pipe, the acoustic damper being provided in the portion. The compressed air present in the intermediate casing that is a space on the outer peripheral side of the pipe flows into the cooling air flow path B. The compressed air exchanges heat with the pipe, which is exposed to the combustion gas, to cool the pipe in the process of passing through the cooling air flow path B. After the compressed air has flowed into the acoustic space, the compressed air flows out to a space on the inner peripheral side of the pipe from the acoustic hole. The compressed air flows out from the acoustic space to the space on the inner peripheral side of the pipe through the acoustic hole such that the high-temperature combustion gas generated in the space on the inner peripheral side of the pipe does not flow into the acoustic space through the acoustic hole. 
     CITATION LIST 
     Patent Literature 
     
         
         [PTL 1] Japanese Unexamined Patent Application Publication No. 2012-077660 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     It is preferable that the mass flow rate of the air flowing out from the acoustic space to the space on the inner peripheral side of the pipe is small from the viewpoint of suppressing the amount of NOx generated. In addition, since the air flowing out from the acoustic space to the space on the inner peripheral side of the pipe lowers the temperature of the combustion gas, which is generated in the space on the inner peripheral side of the pipe, to reduce the efficiency of the gas turbine, it is preferable that the mass flow rate of the air is small. 
     Therefore, an object of the present invention is to provide a technique by which, while the air is allowed to flow out from an acoustic space to a space on an inner peripheral side of a pipe, the mass flow rate of the air can be suppressed. 
     Solution to Problem 
     According to one aspect of the invention to achieve the above object, there is provided a transition piece including: a pipe which has a tubular shape around an axis, and in which fuel is combusted on an inner peripheral side of the pipe; an acoustic damper including a part of a panel forming the pipe, and an acoustic cover forming an acoustic space on an outer peripheral side of the pipe in conjunction with the part of the panel; and a cooling air jacket forming a cooling air space in conjunction with another part of the panel forming the pipe except for a portion forming the acoustic damper, the cooling air space being isolated from an outer space that is a space on the outer peripheral side of the pipe. The pipe includes an inlet opening formed at an end on an upstream side that is one side in an axial direction in which the axis extends, an outlet opening formed at an end on a downstream side that is the other side in the axial direction, an outer peripheral surface facing the outer peripheral side, an inner peripheral surface facing the inner peripheral side, a first air flow path formed between the outer peripheral surface and the inner peripheral surface, and an acoustic hole penetrating through the pipe from the acoustic space to a combustion space that is a space on the inner peripheral side of the pipe. The first air flow path includes an inlet facing the cooling air space and guiding air in the cooling air space into the first air flow path, and an outlet facing the acoustic space and guiding the air, which has passed through the first air flow path, into the acoustic space. 
     In this aspect, the air in the cooling air space flows into the first air flow path to flow through the first air flow path. The air is heated while cooling the pipe because of heat exchange with the pipe, which is exposed to combustion gas, in the process of flowing through the first air flow path. The air that has passed through the first air flow path flows from the outlet of the first air flow path into the acoustic space. The air that has flowed into the acoustic space flows out to the combustion space from the acoustic hole. For this reason, the combustion gas in the combustion space does not flow into the acoustic space. 
     In order to ensure that the combustion gas in the combustion space does not flow into the acoustic space, a pressure Ps in the acoustic space needs to be higher than a pressure Pc in the combustion space, and a pressure difference ΔP between both pressures (=Ps−Pc&gt;0) needs to be a certain value or more. 
     The pressure difference ΔP is proportional to a density p of a fluid and is proportional to the square of a flow velocity v of the fluid as expressed by the following equation. 
       ΔP∝ρ·v 2  
 
     As can be understood from the above equation, when the pressure difference ΔP is to be set to the certain value or more, increasing the flow velocity v of the fluid is more effective than increasing the density p of the fluid. In addition, the flow velocity v of the fluid is increased by increasing the volume of the fluid while reducing the density p of the fluid, so that the mass flow rate of the fluid flowing out from the acoustic space to the combustion space can be suppressed. As a method for increasing the volume of the fluid while reducing the density p of the fluid, there is a method in which the fluid is expanded by increasing the amount of heating of the fluid. 
     Here, in order to facilitate understanding of the following description, a comparative example of this aspect will be described. A pipe of the comparative example does not include the first air flow path of this aspect, but includes a second air flow path. The second air flow path is formed between the outer peripheral surface and the inner peripheral surface of the pipe. The second air flow path includes an inlet that faces the outer space and that guides the air in the outer space into the second air flow path, and an outlet that faces the acoustic space and that guides the air, which has passed through the second air flow path, into the acoustic space. The air in the outer space flows into the second air flow path from the inlet of the second air flow path to flow through the second air flow path. The air is heated while cooling the pipe because of heat exchange with the pipe, which is exposed to the combustion gas, in the process of flowing through the second air flow path. The air that has passed through the second air flow path flows from the outlet of the second air flow path into the acoustic space. The air that has flowed into the acoustic space flows out to the combustion space from the acoustic hole. 
     In the comparative example, when the air in the outer space has a constant pressure and a constant temperature, as a method for increasing the amount of heating of the air flowing through the second air flow path, for example, there is a method for lengthening the flow path length of the second air flow path. In this method, the following problems occur. 
     (1) There is a possibility that the pressure loss in the second air flow path increases, so that the air in the outer space does not reach the acoustic space, or does not flow out to the combustion space from the acoustic hole. 
     (2) There is a possibility that the temperature of the air becomes very high by the time the air reaches the acoustic space, so that the air has no capability to cool the pipe. 
     In addition, there is also another method for forming the second air flow path in a region of the pipe which is easily heated by the combustion gas. Even in this method, the above problem (2) occurs. 
     In this aspect, the air in the cooling air space isolated from the outer space flows through the first air flow path. Therefore, in this aspect, the air having a pressure and a temperature different from those of the air in the outer space is capable of flowing through the first air flow path. For this reason, in this aspect, since the air having a higher pressure and a lower temperature than those of the air in the outer space is supplied to the cooling air space, as the method for increasing the amount of heating of the air, even when the method for lengthening the flow path length of the first air flow path and/or the method for forming the first air flow path in a region of the pipe which is easily heated by the combustion gas are adopted, the above problems (1) and (2) do not occur. 
     Therefore, in this aspect, the pressure difference ΔP (=Ps−Pc) between the pressure Ps in the acoustic space and the pressure Pc in the combustion space Sc is set to the certain value or more, so that while the air is allowed to flow out from the acoustic space to the combustion space on the inner peripheral side of the pipe, the mass flow rate of the air can be suppressed. 
     Here, in the transition piece according to this aspect, the cooling air jacket may be located on the downstream side of the acoustic cover. 
     In the combustion space, the temperature on the downstream side from a tip portion of a flame formed by the combustion of the fuel is higher than the temperature on the upstream side from the tip portion of the flame. Therefore, a region on the downstream side of the pipe is more easily heated by the combustion gas than a region on the upstream side. For this reason, in this aspect, the first air flow path is formed in the region on the downstream side of the pipe which is easily heated, so that the amount of heating of the air flowing through the first air flow path is increased. 
     The transition piece according to this aspect in which the cooling air jacket is located on the downstream side of the acoustic cover may include an attachment flange extending from the outer peripheral surface of the pipe to the outer peripheral side at the end on the downstream side of the pipe. In this case, the cooling air jacket is in contact with the attachment flange. 
     In addition, in the transition piece according to one of the above aspects, the pipe may include a second air flow path formed between the outer peripheral surface and the inner peripheral surface. In this case, the second air flow path includes an inlet facing the outer space and guiding air in the outer space into the second air flow path, and an outlet facing the acoustic space and guiding the air, which has passed through the second air flow path, into the acoustic space. 
     In this aspect, a portion of the pipe which cannot be cooled by the air flowing through the first air flow path can be cooled by the air flowing through the second air flow path. 
     In addition, the transition piece according to one of the above aspects may include a plurality of the acoustic covers. In this case, the outlet of the first air flow path faces the acoustic space formed by at least one acoustic cover of the plurality of acoustic covers. 
     In the transition piece according to this aspect which includes the plurality of acoustic covers, the pipe may include a second air flow path formed between the outer peripheral surface and the inner peripheral surface. In this case, the second air flow path includes an inlet facing the outer space and guiding air in the outer space into the second air flow path, and an outlet facing the acoustic space formed by at least the one acoustic cover of the plurality of acoustic covers, and guiding the air, which has passed through the second air flow path, into the acoustic space. 
     In this aspect, a portion of the pipe which cannot be cooled by the air flowing through the first air flow path can be cooled by the air flowing through the second air flow path. 
     In the transition piece according to this aspect which includes the plurality of acoustic covers and the second air flow path, the pipe may include the first air flow path and the second air flow path, which communicate with the acoustic space formed by each of the acoustic covers, for each of the plurality of acoustic covers. 
     In the transition piece according to one of the above aspects which includes the second air flow path, the inlet of the second air flow path may be located on the upstream side of the acoustic cover. 
     In this aspect, a portion on the upstream side of the pipe with respect to the acoustic cover can be cooled by the air flowing through the second air flow path. 
     In the transition piece according to one of the above aspects, the pipe may include a third air flow path formed between the outer peripheral surface and the inner peripheral surface. In this case, the third air flow path includes an inlet facing the cooling air space and guiding the air in the cooling air space into the third air flow path, and an outlet facing the outer space and guiding the air, which has passed through the third air flow path, into the outer space. 
     In this aspect, a portion of the pipe which cannot be cooled by the air flowing through the first air flow path can be cooled by the air flowing through the third air flow path. 
     In the transition piece according to this aspect which includes the second air flow path, an opening area of the outlet guiding the air, which has passed through the first air flow path, into the acoustic space is larger than an opening area of the outlet guiding air, which has passed through the second air flow path, into the acoustic space. 
     In this aspect, when the air that has passed through the first air flow path flows into the acoustic space, the flow velocity of the air can be reduced, so that a reduction in static pressure in the acoustic space can be suppressed and the combustion gas can be suppressed from flowing into the acoustic space. 
     According to one aspect of the invention to achieve the above object, there is provided a combustor including: the transition piece according to one of the above aspects; and a burner that injects fuel and air into the combustion space. 
     According to one aspect of the invention to achieve the above object, there is provided a gas turbine including: the combustor; a compressor; a turbine; and an intermediate casing. The compressor includes a compressor rotor rotating around a rotor axis, and a compressor casing covering the compressor rotor. The turbine includes a turbine rotor rotating integrally with the compressor rotor around the rotor axis, and a turbine casing covering the turbine rotor. The intermediate casing is disposed between the compressor casing and the turbine casing in a rotor axial direction in which the rotor axis extends, and connects the compressor casing and the turbine casing, and compressed air that has been discharged from the compressor flows into the intermediate casing. The combustor is provided in the intermediate casing. 
     According to one aspect of the invention to achieve the above object, there is gas turbine equipment including: the gas turbine according to this aspect; a cooling air line guiding the compressed air in the intermediate casing to an outside of the intermediate casing, and then guiding the compressed air into the cooling air jacket; a cooler provided in the cooling air line, and cooling the compressed air passing through the cooling air line; and a boost compressor provided in the cooling air line, and boosting the compressed air that has been cooled by the cooler. 
     Advantageous Effects of Invention 
     According to one aspect of the present invention, while the air is allowed to flow out from the acoustic space of the acoustic damper to the space on the inner peripheral side of the pipe, the mass flow rate of the air can be suppressed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a conceptual view illustrating a configuration of gas turbine equipment according to a first embodiment of the present invention. 
         FIG. 2  is a sectional view of a main part of the gas turbine equipment according to the first embodiment of the present invention. 
         FIG. 3  is a sectional view of a main part of a transition piece according to the first embodiment of the present invention. 
         FIG. 4  is a view on arrow IV in  FIG. 3 . 
         FIG. 5  is a sectional view taken along line V-V in  FIG. 3 . 
         FIG. 6  is a sectional view of a main part of a transition piece according to a second embodiment of the present invention. 
         FIG. 7  is a view on arrow VII in  FIG. 6 . 
         FIG. 8  is a sectional view of a main part of a transition piece according to a third embodiment of the present invention. 
         FIG. 9  is a view on arrow IX in  FIG. 8 . 
         FIG. 10  is a sectional view of a main part of a transition piece according to a fourth embodiment of the present invention. 
         FIG. 11  is a view on arrow XI in  FIG. 10 . 
         FIG. 12  is a sectional view according to a fifth embodiment of the present invention, which corresponds to  FIG. 6 . 
         FIG. 13  is a view on an arrow according to the fifth embodiment of the present invention, which corresponds to  FIG. 7 . 
         FIG. 14  is a view on an arrow in a modification example of the fifth embodiment according to the present invention, which corresponds to  FIG. 13 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, various embodiments of gas turbine equipment according to the present invention and modification examples thereof will be described in detail with reference to the drawings. 
     First Embodiment 
     Hereinafter, a first embodiment of the gas turbine equipment according to the present invention will be described with reference to  FIGS. 1 to 5 . 
     As illustrated in  FIG. 1 , the gas turbine equipment of the present embodiment includes a gas turbine  10  and a cooling device  70  that cools some components of the gas turbine  10 . 
     The gas turbine  10  includes a compressor  20  that compresses air A; a plurality of combustors  40  that combust fuel in the air, which has been compressed by the compressor  20 , to generate combustion gas G; and a turbine  30  that is driven by the combustion gas G. 
     The compressor  20  includes a compressor rotor  21  that rotates around a rotor axis Lr; a compressor casing  25  that rotatably covers the compressor rotor  21 ; an d a plurality of stator vane rows  26 . Hereinafter, a direction in which the rotor axis Lr extends is referred to as a rotor axial direction Da, and one side and the other side in the rotor axial direction Da are referred to as an axial upstream side Dau and an axial downstream side Dad, respectively. In addition, a circumferential direction around the rotor axis Lr is simply referred to as a circumferential direction Dc, and a direction perpendicular to the rotor axis Lr is referred as a radial direction Dr. Further, a side approaching the rotor axis Lr in the radial direction Dr is referred to as a radial inner side Dri, and an opposite side is referred to as a radial outer side Dro. 
     The compressor rotor  21  includes a rotor shaft  22  extending along the rotor axis Lr in the rotor axial direction Da, and a plurality of rotor blade rows  23  attached to the rotor shaft  22 . The plurality of rotor blade rows  23  are arranged in the rotor axial direction Da. Each of the rotor blade rows  23  is formed of a plurality of rotor blades arranged in the circumferential direction Dc. One stator vane row  26  of the plurality of stator vane rows  26  is disposed on the axial downstream side Dad of each of the plurality of rotor blade rows  23 . Each of the stator vane rows  26  is provided inside the compressor casing  25 . Each of the stator vane rows  26  is formed of a plurality of stator vanes arranged in the circumferential direction Dc. An annular space between the radial outer side Dro of the rotor shaft  22  and the radial inner side Dri of the compressor casing  25  in a region in which the stator vanes and the rotor blades are disposed in the rotor axial direction Da forms an air compression flow path in which the air is compressed while flowing therethrough. 
     The turbine  30  is disposed on the axial downstream side Dad of the compressor  20 . The turbine  30  includes a turbine rotor  31  that rotates around the rotor axis Lr; a turbine casing  35  that rotatably covers the turbine rotor  31 ; and a plurality of stator vane rows  36 . The turbine rotor  31  includes a rotor shaft  32  extending along the rotor axis Lr in the rotor axial direction Da, and a plurality of rotor blade rows  33  attached to the rotor shaft  32 . The plurality of rotor blade rows  33  are arranged in the rotor axial direction Da. Each of the rotor blade rows  33  is formed of a plurality of rotor blades arranged in the circumferential direction Dc. One stator vane row  36  of the plurality of stator vane rows  36  is disposed on the axial upstream side Dau of each of the plurality of rotor blade rows  33 . Each of the stator vane rows  36  is provided inside the turbine casing  35 . Each of the stator vane rows  36  is formed of a plurality of stator vanes arranged in the circumferential direction Dc. An annular space between the radial outer side Dro of the rotor shaft  32  and the radial inner side Dri of the turbine casing  35  in a region in which the stator vanes and the rotor blades are disposed in the rotor axial direction Da forms a combustion gas flow path through which the combustion gas G from the combustors  40  flows. 
     The compressor rotor  21  and the turbine rotor  31  are located on the same rotor axis Lr, and are connected to each other to form a gas turbine rotor  11 . For example, a rotor of a generator GEN is connected to the gas turbine rotor  11 . The gas turbine  10  further includes an intermediate casing  16  having a tubular shape and having the rotor axis Lr as a center. The intermediate casing  16  is disposed between the compressor casing  25  and the turbine casing  35  in the rotor axial direction Da. The compressor casing  25  and the turbine casing  35  are connected to each other via the intermediate casing  16 . The compressor casing  25 , the intermediate casing  16 , and the turbine casing  35  are connected to each other to form a gas turbine casing  15 . Compressed air Acom from the compressor  20  flows into the intermediate casing  16 . The plurality of combustors  40  are provided in the intermediate casing  16 . 
     The cooling device  70  includes a cooling air line  71 , a cooler  75 , and a boost compressor  76 . The cooling air line  71  bleeds the compressed air Acom in the intermediate casing  16  from the inside of the intermediate casing  16 , and guides the compressed air Acom to the combustors  40 . The cooling air line  71  includes an air bleeding line  72 , a cooling air main line  73 , and a plurality of cooling air branch lines  74 . The air bleeding line  72  is connected to the intermediate casing  16 , and guides the compressed air Acom in the intermediate casing  16  to the boost compressor  76 . The cooling air main line  73  is connected to a discharge port of the boost compressor  76 . Enhanced cooling air Acl that is air boosted by the boost compressor  76  flows through the cooling air main line  73 . The cooling air branch line  74  is a line branching from the cooling air main line  73  to each of the plurality of combustors  40 . Each of the plurality of cooling air branch lines  74  guides the enhanced cooling air Acl to one of the combustors  40 . The cooler  75  and the boost compressor  76  are provided in the air bleeding line  72  of the cooling air line  71 . The cooler  75  cools the compressed air Acom flowing through the air bleeding line  72 . The boost compressor  76  boosts the compressed air Acom that has been cooled by the cooler  75 , and feeds the compressed air Acom to the combustors  40  as the enhanced cooling air Acl. 
     As illustrated in  FIG. 2 , the combustor  40  includes a transition piece (or combustion pipe)  50  that feeds the high-temperature and high-pressure combustion gas G into the combustion gas flow path of the turbine  30 , and a fuel nozzle  41  that injects fuel F into the transition piece  50 , together with the compressed air Acom. The fuel nozzle  41  includes a plurality of burners  42  that inject the fuel F into the transition piece  50 , and a frame  43  that supports the plurality of burners  42 . A fuel line  45  is connected to each of the burners  42 . The fuel line  45  is provided with a fuel flow rate-regulating valve  46  that regulates the flow rate of the fuel F to be supplied to the plurality of burners  42 . The transition piece  50  of the combustor  40  is disposed inside the intermediate casing  16 . 
     The transition piece  50  includes a pipe  51  having a tubular shape around a combustor axis Lcom; an acoustic damper  61  forming an acoustic space Ss on an outer peripheral side of the pipe  51 ; a cooling air jacket  65  forming a cooling air space Sa on the outer peripheral side of the pipe  51 ; and an attachment flange  66 . Hereinafter, a direction in which the combustor axis Lcom extends is referred to as a combustor axial direction Dcom (hereinafter, simply referred to as an axial direction Dcom). In addition, one side in the axial direction Dcom is referred to as a combustor upstream side Dcu (hereinafter, simply referred to as an upstream side Dcu), and the other side in the axial direction Dcom is referred to as a combustor downstream side Dcd (hereinafter, simply referred to as a downstream side Dcd). 
     The pipe  51  includes an inlet opening  54   i  formed at an end on the upstream side Dcu; an outlet opening  54   o  formed at an end on the downstream side Dcd; an outer peripheral surface  55   o  facing the outer peripheral side; and an inner peripheral surface  55   i  facing an inner peripheral side. A space on the inner peripheral side of the pipe  51  is a combustion space Sc in which the fuel F is combusted and through which the combustion gas G generated by the combustion flows. The attachment flange  66  extends from the outer peripheral surface  55   o  of the pipe  51  to the outer peripheral side at an end on the downstream side Dcd of the pipe  51 . The attachment flange  66  is a flange for attaching the pipe  51  to the turbine casing  35 . 
     The acoustic damper  61  includes a part of a panel forming the pipe  51 , and an acoustic cover  62  forming the acoustic space Ss on the outer peripheral side of the pipe  51  in conjunction with the part of the pipe  51 . The acoustic cover  62  is provided in a portion on the upstream side Dcu of the pipe  51 . The acoustic cover  62  extends in the circumferential direction with respect to the combustor axis Lcom. 
     The cooling air jacket  65  forms the cooling air space Sa on the outer peripheral side of the pipe  51  in conjunction with another part except for the portion forming the acoustic damper  61  in the panel forming the pipe  51 , and the attachment flange  66 . For this reason, a part of an edge of the cooling air jacket  65  is in contact with the attachment flange  66 , and the remainder of the edge of the cooling air jacket  65  is in contact with the pipe  51 . The cooling air space Sa is isolated from an outer space So that is a space on the outer peripheral side of the pipe  51 . The outer space So is a space on the outer peripheral side of the pipe  51  and inside the intermediate casing  16 , excluding the acoustic space Ss and the cooling air space Sa. During operation of the gas turbine  10 , the compressed air Acom that has been discharged from the compressor  20  is present in the outer space So. In addition, the fact that the cooling air space Sa is isolated from the outer space So means that the compressed air Acom in the outer space So does not directly flow into the cooling air space Sa. As described above, the cooling air jacket  65  is in contact with the attachment flange  66  provided at the end on the downstream side Dcd of the pipe  51 , which means that the cooling air jacket  65  is located on the downstream side Dcd of the acoustic cover  62 . The cooling air branch lines  74  of the cooling device  70  described above are connected to the cooling air jacket  65 . Therefore, the enhanced cooling air Acl from the cooling device  70  flows into the cooling air space Sa. 
     As illustrated in  FIGS. 3 and 4 , the pipe  51  includes a plurality of acoustic holes  59 , a plurality of first air flow paths  56 , and a plurality of third air flow paths  58 .  FIG. 3  is a sectional view of a main part of the transition piece  50  taken along a virtual plane including the combustor axis Lcom, and  FIG. 4  is a view on arrow IV in  FIG. 3 . 
     The acoustic hole  59  penetrates through the panel forming the pipe  51  from the acoustic space Ss to the combustion space Sc. Therefore, the acoustic hole  59  is a hole penetrating through a portion of the pipe  51 , which is covered by the acoustic cover  62 , from the outer peripheral surface  55   o  to the inner peripheral surface  55   i  of the pipe  51 . 
     Both the first air flow path  56  and the third air flow path  58  are formed between the outer peripheral surface  55   o  and the inner peripheral surface  55   i  of the pipe  51 . The first air flow path  56  includes an inlet  56   i  that faces the cooling air space Sa and that guides the air in the cooling air space Sa into the first air flow path  56 , and an outlet  56   o  that faces the acoustic space Ss and that guides the air, which has passed through the first air flow path  56 , into the acoustic space Ss. Therefore, the inlet  56   i  of the first air flow path  56  is formed in a portion of the outer peripheral surface  55   o  of the pipe  51 , the portion being covered by the cooling air jacket  65 . In addition, the outlet  56   o  of the first air flow path  56  is formed in a portion of the outer peripheral surface  55   o  of the pipe  51 , the portion being covered by the acoustic cover  62 . The third air flow path  58  includes an inlet  58   i  that faces the cooling air space Sa and that guides the air in the cooling air space Sa into the third air flow path  58 , and an outlet  58   o  that faces the outer space So and that guides the air, which has passed through the third air flow path  58 , into the outer space So. Therefore, the inlet  58   i  of the third air flow path  58  is formed in a portion of the outer peripheral surface  55   o  of the pipe  51 , the portion being covered by the cooling air jacket  65 . In addition, the outlet  58   o  of the third air flow path  58  is formed in a portion of the outer peripheral surface  55   o  of the pipe  51 , the portion not being covered by the acoustic cover  62  and the cooling air jacket  65 . Among the plurality of third air flow paths  58 , the outlets  58   o  of some of the third air flow paths  58  are formed in a portion on the upstream side Dcu of the outer peripheral surface  55   o  of the pipe  51  with respect to the portion covered by the acoustic cover  62 . 
     As illustrated in  FIG. 5 , the panel forming the pipe  51  is formed by joining an outer peripheral wall panel  52   o  and an inner peripheral wall panel  52   i  by means of brazing or the like. A plurality of grooves  53  that are recessed in a direction away from the other side and that are long in the axial direction Dcom are formed in one wall panel of the outer peripheral wall panel  52   o  and the inner peripheral wall panel  52   i . An air flow path  56  ( 58 ) through which the air flows is formed between an inner surface of the groove  53  and a surface of the other wall panel. In the present embodiment, the grooves  53  are formed in the outer peripheral wall panel  52   o.    
     Next, an operation of the gas turbine  10  described above will be described. 
     The compressor  20  suctions outside air A, and compresses the air while the air passes through the air compression flow path. The compressed air, namely, the compressed air Acom, flows from the air compression flow path of the compressor  20  into the intermediate casing  16 . The compressed air Acom is supplied into the pipe  51  of the transition piece  50  via the fuel nozzle  41  of the combustor  40 . The fuel F is injected into the pipe  51  of the transition piece  50  from the plurality of burners  42  of the fuel nozzle  41 . The fuel F is combusted in the compressed air Acom that has been supplied into the combustion space Sc of the pipe  51 . As a result of the combustion, the combustion gas G is generated, and the combustion gas G flows from the transition piece  50  into the combustion gas flow path of the turbine  30 . When the combustion gas G passes through the combustion gas flow path, the turbine rotor  31  rotates. 
     While the fuel F is combusted in the combustion space Sc, the boost compressor  76  of the cooling device  70  is driven. For this reason, the compressed air Acom in the outer space So, in other words, some of the compressed air Acom in the intermediate casing  16 , is bled from the inside of the intermediate casing  16 , flows into the cooler  75  of the cooling device  70 , and then is cooled here. The compressed air Acom that has been cooled in the cooler  75  is boosted by the boost compressor  76 , and then flows into the cooling air space Sa of the transition piece  50  as the enhanced cooling air Acl. Since the enhanced cooling air Acl is air obtained by cooling and then boosting the compressed air Acom in the intermediate casing  16 , the enhanced cooling air Acl has a lower temperature and a higher pressure than those of the compressed air Acom in the intermediate casing  16 . 
     The enhanced cooling air Acl in the cooling air space Sa flows into the first air flow path  56  and the third air flow path  58  of the pipe  51  to flow through the air flow paths  56  and  58 . The enhanced cooling air Acl is heated while cooling the pipe  51  because of heat exchange with the pipe  51 , which is exposed to the high-temperature combustion gas G, in the process of flowing through the air flow paths  56  and  58 . 
     The enhanced cooling air Acl that has passed through the third air flow path  58  flows out to the outer space So from the outlet  58   o  of the third air flow path  58 , and is mixed with the compressed air Acom present in the outer space So. In addition, the enhanced cooling air Acl that has passed through the first air flow path  56  flows from the outlet  56   o  of the first air flow path  56  into the acoustic space Ss. The enhanced cooling air Acl that has flowed into the acoustic space Ss flows out to the combustion space Sc from the acoustic hole  59 . For this reason, the combustion gas G in the combustion space Sc does not flow into the acoustic space Ss. 
     In order to ensure that the combustion gas G in the combustion space Sc does not flow into the acoustic space Ss, a pressure Ps in the acoustic space Ss needs to be higher than a pressure Pc in the combustion space Sc, and a pressure difference ΔP between both pressures (=Ps−Pc&gt;0) needs to be a certain value or more. 
     The pressure difference ΔP is proportional to a density p of a fluid and is proportional to the square of a flow velocity v of the fluid as expressed by the following equation. 
       Δ∝ρ·v 2  
 
     As can be understood from the above equation, when the pressure difference ΔP is to be set to the certain value or more, increasing the flow velocity v of the fluid is more effective than increasing the density p of the fluid. In addition, the flow velocity v of a fluid is increased by increasing the volume of the fluid while reducing the density p of the fluid, so that the mass flow rate of the fluid flowing out from the acoustic space Ss to the combustion space Sc can be suppressed. As a method for increasing the volume of the fluid while reducing the density p of the fluid, there is a method in which the fluid is expanded by increasing the amount of heating of the fluid. 
     Here, in order to facilitate understanding of the following description, a comparative example of this aspect will be described. A pipe of the comparative example does not include the first air flow path  56 , but includes a second air flow path  57  illustrated by an imaginary line (alternate long and two short dashed line) in  FIG. 3 . The second air flow path  57  is formed between the outer peripheral surface  55   o  and the inner peripheral surface  55   i  of the pipe  51 . The second air flow path  57  includes an inlet  57   i  that faces the outer space So and that guides the air in the outer space So into the second air flow path  57 , and an outlet  57   o  that faces the acoustic space Ss and that guides the air, which has passed through the second air flow path  57 , into the acoustic space Ss. The inlet  57   i  of the second air flow path  57  is located on the upstream side Dcu of the acoustic cover  62 . The air in the outer space So flows into the second air flow path  57  from the inlet  57   i  of the second air flow path  57  to flow through the second air flow path  57 . The air is heated while cooling the pipe because of heat exchange with the pipe  51 , which is exposed to the combustion gas G, in the process of flowing through the second air flow path  57 . The air that has passed through the second air flow path  57  flows from the outlet  57   o  of the second air flow path  57  into the acoustic space Ss. The air that has flowed into the acoustic space Ss flows out to the combustion space Sc from the acoustic hole  59 . 
     In the comparative example, when the air in the outer space So, namely, the compressed air Acom, has a constant pressure and a constant temperature, as a method for increasing the amount of heating of the air flowing through the second air flow path  57 , for example, there is a method for lengthening the flow path length of the second air flow path  57 . In this method, the following problems occur. 
     (1) There is a possibility that the pressure loss in the second air flow path  57  increases, so that the air in the outer space So does not reach the acoustic space Ss, or does not flow out to the combustion space Sc from the acoustic hole  59 . 
     (2) There is a possibility that the temperature of the air becomes very high by the time the air reaches the acoustic space Ss, so that the air has no capability to cool the pipe  51 . 
     In addition, there is also another method for forming the second air flow path  57  in a region of the pipe  51  which is easily heated by the combustion gas G. Even in this method, the above problem (2) occurs. 
     In the present embodiment, the enhanced cooling air Acl in the cooling air space Sa isolated from the outer space So flows through the first air flow path  56 . Therefore, in the present embodiment, the air having a pressure and a temperature different from those of the compressed air Acom in the outer space So is capable of flowing through the first air flow path  56 . Therefore, in the present embodiment, the enhanced cooling air Acl having a higher pressure and a lower temperature than those of the compressed air Acom in the outer space So flows through the first air flow path  56 . For this reason, in the present embodiment, as the method for increasing the amount of heating of the air, even when the method for lengthening the flow path length of the first air flow path  56  and/or the method for forming the first air flow path  56  in a region of the pipe  51  which is easily heated by the combustion gas G are adopted, the above problems (1) and (2) do not occur. 
     Therefore, in the present embodiment, the pressure difference ΔP (=Ps−Pc) between the pressure Ps in the acoustic space Ss and the pressure Pc in the combustion space Sc is set to the certain value or more, so that while the air is allowed to flow out from the acoustic space Ss to the combustion space Sc on the inner peripheral side of the pipe  51 , the mass flow rate of the air can be suppressed. 
     As described above, in the present embodiment, since the mass flow rate of the air flowing out from the acoustic space Ss to the combustion space Sc on the inner peripheral side of the pipe  51  can be suppressed, the amount of NOx generated can be suppressed. Further, in the present embodiment, since the amount of the combustion gas G diluted by the air flowing out to the combustion space Sc is decreased, a reduction in the temperature of the gas to be fed to the turbine  30  can be suppressed, and a reduction in the efficiency of the gas turbine  10  can be suppressed. 
     In the present embodiment, as the method for increasing the amount of heating of the air, the method for lengthening the flow path length of the first air flow path  56  and the method for forming the first air flow path  56  in a region of the pipe  51  which is easily heated by the combustion gas G are adopted. Specifically, in the present embodiment, the flow path length of the first air flow path  56  is lengthened by providing the cooling air jacket  65  in a portion on the downstream side Dcd of the pipe  51 , and allowing the cooling air space Sa in the cooling air jacket  65  and the acoustic space Ss in the acoustic damper  61 , which is disposed in a portion on the upstream side Dcu of the pipe  51 , to communicate with each other through the first air flow path  56 . In the combustion space Sc of the pipe  51 , the temperature on the downstream side Dcd from a tip portion of a flame formed by the combustion of the fuel F is higher than the temperature on the upstream side Dcu from the tip portion of the flame. Therefore, a region on the downstream side Dcd of the pipe  51  is more easily heated by the combustion gas G than a region on the upstream side Dcu. Therefore, in the present embodiment, the first air flow path  56  is formed in a region on the downstream side Dcd of the pipe  51  which is easily heated. 
     In the present embodiment, as described above, as the method for increasing the amount of heating of the air, the method for lengthening the flow path length of the first air flow path  56  and the method for forming the first air flow path  56  in a region of the pipe  51  which is easily heated by the combustion gas G are both adopted. However, only one of the above two methods may be adopted. 
     Second Embodiment 
     Hereinafter, a second embodiment of the gas turbine equipment according to the present invention will be described with reference to  FIGS. 6 and 7 . The gas turbine equipment of the present embodiment differs from the gas turbine equipment of the first embodiment only in the configuration of the transition piece of the combustor. Therefore, hereinafter, a configuration of a transition piece  50   a  of the present embodiment will be mainly described. 
     Similarly to the first embodiment, the transition piece  50   a  of the present embodiment includes a pipe  51   a ; the acoustic damper  61 ; the cooling air jacket  65 ; and the attachment flange  66 . Similarly to the pipe  51  of the first embodiment, the pipe  51   a  includes the inlet opening  54   i ; the outlet opening  54   o ; the outer peripheral surface  55   o ; the inner peripheral surface  55   i ; a plurality of the first air flow paths  56 ; and a plurality of the third air flow paths  58 . The pipe  51   a  of the present embodiment further includes a plurality of the second air flow paths  57 . The second air flow path  57  is formed between the outer peripheral surface  55   o  and the inner peripheral surface  55   i  of the pipe  51   a . The second air flow path  57  includes the inlet  57   i  that faces the outer space So and that guides the compressed air Acom in the outer space So into the second air flow path  57 , and the outlet  57   o  that faces the acoustic space Ss and that guides the compressed air Acom, which has passed through the second air flow path  57 , into the acoustic space Ss. The inlet  57   i  of the second air flow path  57  is located on the upstream side Dcu of the acoustic cover  62 . The pipe  51   a  of the present embodiment includes the third air flow path  58 , but may not include the third air flow path  58 . 
     Also in the present embodiment, similarly to the first embodiment, the enhanced cooling air Acl in the cooling air space Sa flows into the first air flow path  56  and the third air flow path  58  of the pipe  51   a  to flow through the air flow paths  56  and  58 . The enhanced cooling air Acl is heated while cooling the pipe  51   a  because of heat exchange with the pipe  51   a , which is exposed to the high-temperature combustion gas G, in the process of flowing through the air flow paths  56  and  58 . The enhanced cooling air Acl that has passed through the third air flow path  58  flows out to the outer space So from the outlet  58   o  of the third air flow path  58 , and is mixed with the compressed air Acom present in the outer space So. In addition, the enhanced cooling air Acl that has passed through the first air flow path  56  flows from the outlet  56   o  of the first air flow path  56  into the acoustic space Ss. 
     The compressed air Acom in the outer space So flows into the second air flow path  57  from the inlet  57   i  of the second air flow path  57  to flow through the second air flow path  57 . The compressed air Acom is heated while cooling the pipe  51   a  because of heat exchange with the pipe  51   a , which is exposed to the combustion gas G, in the process of flowing through the second air flow path  57 . The compressed air Acom that has passed through the second air flow path  57  flows from the outlet  57   o  of the second air flow path  57  into the acoustic space Ss. 
     Therefore, in the present embodiment, the enhanced cooling air Acl that has flowed through the first air flow path  56  and the compressed air Acom that has flowed through the second air flow path  57  flow into the acoustic space Ss. The air that has flowed into the acoustic space Ss flows out to the combustion space Sc through the acoustic hole  59 . As described above, in the present embodiment, similarly to the first embodiment, since the air flowing out from the acoustic space Ss to the combustion space Sc through the acoustic hole  59  includes the enhanced cooling air Acl that has flowed through the first air flow path  56 , the air having a large amount of heating of the air is capable of flowing out to the combustion space Sc. Therefore, also in the present embodiment, similarly to the first embodiment, while the air is allowed to flow out from the acoustic space Ss to the combustion space Sc, the mass flow rate of the air can be suppressed. 
     In the first embodiment, a portion on the upstream side Dcu of the pipe  51  with respect to the acoustic cover  62  is cooled by the air flowing through the third air flow path  58 . The amount of heating of the air flowing through the third air flow path  58  by the time the air reaches the acoustic cover  62  is large. On the other hand, in the present embodiment, the portion on the upstream side Dcu of the pipe  51   a  with respect to the acoustic cover  62  is cooled by the air flowing through the second air flow path  57 . In the portion on the upstream side Dcu of the pipe  51   a  with respect to the acoustic cover  62 , the temperature of the air flowing through the second air flow path  57  is lower than the temperature of the air flowing through the third air flow path  58 . For this reason, in the present embodiment, the cooling capacity of the portion on the upstream side Dcu of the pipe  51   a  with respect to the acoustic cover  62  can be increased more than in the first embodiment. 
     Third Embodiment 
     Hereinafter, a third embodiment of the gas turbine equipment according to the present invention will be described with reference to  FIGS. 8 and 9 . The gas turbine equipment of the present embodiment differs from the gas turbine equipment of the first embodiment only in the configuration of the transition piece of the combustor. Therefore, hereinafter, a configuration of a transition piece  50   b  of the present embodiment will be mainly described. 
     Similarly to the first embodiment, the transition piece  50   b  of the present embodiment includes a pipe  51   b ; acoustic dampers  61   a  and  61   b ; the cooling air jacket  65 ; and the attachment flange  66 . However, the transition piece  50   b  of the present embodiment includes a plurality of the acoustic dampers  61   a  and  61   b . Similarly to the pipe  51  of the first embodiment, the pipe  51   b  includes the inlet opening  54   i ; the outlet opening  54   o ; the outer peripheral surface  55   o ; the inner peripheral surface  55   i ; a plurality of the first air flow paths  56 ; and a plurality of the third air flow paths  58 . The outlet  56   o  of the first air flow path  56  of the present embodiment faces only a first acoustic space Ssa of the first acoustic damper  61   a  of the plurality of acoustic dampers  61   a  and  61   b , and does not face a second acoustic space Ssb of the second acoustic damper  61   b . Therefore, in the present embodiment, the enhanced cooling air Acl in the cooling air space Sa flows into the first acoustic space Ssa through the first air flow path  56 , but does not flow into the second acoustic space Ssb. The pipe  51   b  of the present embodiment further includes a plurality of the second air flow paths  57 . The second air flow path  57  is formed between the outer peripheral surface  55   o  and the inner peripheral surface  55   i  of the pipe  51   b . The second air flow path  57  includes the inlet  57   i  that faces the outer space So and that guides the air in the outer space So into the second air flow path  57 , and the outlet  57   o  that faces only the second acoustic space Ssb and that guides the air, which has passed through the second air flow path  57 , into the second acoustic space Ssb. Therefore, in the present embodiment, the compressed air Acorn in the outer space So flows into the second acoustic space Ssb through the second air flow path  57 , but does not flow into the first acoustic space Ssa. The inlet  57   i  of the second air flow path  57  is located on the upstream side Dcu of the respective acoustic covers  62  of the plurality of acoustic dampers  61   a  and  61   b . The pipe  51   b  of the present embodiment includes the third air flow path  58 , but may not include the third air flow path  58 . 
     Also in the present embodiment, similarly to the first embodiment, the enhanced cooling air Acl in the cooling air space Sa flows into the first air flow path  56  and the third air flow path  58  of the pipe  51   b  to flow through the air flow paths  56  and  58 . The enhanced cooling air Acl is heated while cooling the pipe  51   b  because of heat exchange with the pipe  51   b , which is exposed to the high-temperature combustion gas G, in the process of flowing through the air flow paths  56  and  58 . The air that has passed through the third air flow path  58  flows out to the outer space So from the outlet  58   o  of the third air flow path  58 , and is mixed with the compressed air Acom present in the outer space So. In addition, the enhanced cooling air Acl that has passed through the first air flow path  56  flows from the outlet  56   o  of the first air flow path  56  into the first acoustic space Ssa. The air that has flowed into the first acoustic space Ssa flows out to the combustion space Sc from a first acoustic hole  59   a  of the first acoustic damper  61   a.    
     The compressed air Acom in the outer space So flows into the second air flow path  57  from the inlet  57   i  of the second air flow path  57  to flow through the second air flow path  57 . The compressed air Acom is heated while cooling the pipe  51   b  because of heat exchange with the pipe  51   b , which is exposed to the combustion gas G, in the process of flowing through the second air flow path  57 . The compressed air Acom that has passed through the second air flow path  57  flows from the outlet  57   o  of the second air flow path  57  into the second acoustic space Ssb. The compressed air Acom that has flowed into the second acoustic space Ssb flows out to the combustion space Sc from a second acoustic hole  59   b  of the second acoustic damper  61   b.    
     As described above, in the present embodiment, the enhanced cooling air Acl that has flowed through the first air flow path  56  flows into the first acoustic space Ssa of a plurality of the acoustic spaces Ss. The air that has flowed into the first acoustic space Ssa flows out to the combustion space Sc through the first acoustic hole  59   a . For this reason, in the present embodiment, the total mass flow rate of the air flowing out from all the acoustic spaces Ssa and Ssb to the combustion space Sc can be suppressed more than when only the compressed air Acom that has flowed through the second air flow path  57  flows into all the acoustic spaces Ssa and Ssb. 
     In addition, in the present embodiment, similarly to the second embodiment, since the second air flow path  57  is provided, the cooling capacity of the portion on the upstream side Dcu of the pipe  51   b  with respect to the acoustic cover  62  can be increased more than in the first embodiment. 
     Fourth Embodiment 
     Hereinafter, a fourth embodiment of the gas turbine equipment according to the present invention will be described with reference to  FIGS. 10 and 11 . The gas turbine equipment of the present embodiment is a modification example of the third embodiment, and differs from the gas turbine equipment of the third embodiment only in the configuration of the transition piece of the combustor. Therefore, hereinafter, a configuration of a transition piece  50   c  of the present embodiment will be mainly described. 
     Similarly to the third embodiment, the transition piece  50   c  of the present embodiment includes a pipe  51   c ; a plurality of the acoustic dampers  61   a  and  61   b ; the cooling air jacket  65 ; and the attachment flange  66 . Similarly to the pipe  51   b  of the third embodiment, the pipe  51   c  includes the inlet opening  54   i ; the outlet opening  54   o ; the outer peripheral surface  55   o ; the inner peripheral surface  55   i ; a plurality of the first air flow paths  56 ; and a plurality of the second air flow paths  57 . In the present embodiment, among the plurality of first air flow paths  56 , the outlets  56   o  of some of the first air flow paths  56  face only the first acoustic space Ssa of the first acoustic damper  61   a  of the plurality of acoustic dampers  61   a  and  61   b , and do not face the second acoustic space Ssb of the second acoustic damper  61   b . In addition, among the plurality of first air flow paths  56 , the outlets  56   o  of the other first air flow paths  56  face only the second acoustic space Ssb of the second acoustic damper  61   b  of the plurality of acoustic dampers  61   a  and  61   b , and do not face the first acoustic space Ssa of the first acoustic damper  61   a . Therefore, in the present embodiment, the enhanced cooling air Acl in the cooling air space Sa flows into each of the acoustic spaces Ssa and Ssb of the plurality of acoustic dampers  61   a  and  61   b  through one of the plurality of first air flow paths  56 . In the present embodiment, among the plurality of second air flow paths  57 , the outlets  57   o  of some of the second air flow paths  57  face only the first acoustic space Ssa of the first acoustic damper  61   a  of the plurality of acoustic dampers  61   a  and  61   b , and do not face the second acoustic space Ssb of the second acoustic damper  61   b . In addition, among the plurality of second air flow paths  57 , the outlets  57   o  of the other second air flow paths  57  face only the second acoustic space Ssb of the second acoustic damper  61   b  of the plurality of acoustic dampers  61   a  and  61   b , and do not face the first acoustic space Ssa of the first acoustic damper  61   a . Therefore, in the present embodiment, the compressed air Acom in the outer space So flows into each of the acoustic spaces Ssa and Ssb of the plurality of acoustic dampers  61   a  and  61   b  through one of the plurality of second air flow paths  57 . 
     As described above, in the present embodiment, similarly to the second embodiment, the enhanced cooling air Acl that has flowed through the first air flow path  56  and the compressed air Acom that has flowed through the second air flow path  57  flow into the acoustic spaces Ssa and Ssb of the plurality of acoustic dampers  61   a  and  61   b , respectively. The air that has flowed into the first acoustic space Ssa flows out to the combustion space Sc through the first acoustic hole  59   a . The air that has flowed into the second acoustic space Ssb flows out to the combustion space Sc through the second acoustic hole  59   b . Therefore, also in the present embodiment, similarly to the second embodiment, while the air is allowed to flow out from the acoustic spaces Ssa and Ssb to the combustion space Sc on the inner peripheral side of the pipe  51   c , the mass flow rate of the air can be suppressed. 
     The pipe  51   c  of the present embodiment does not include the third air flow path  58  in each of the above embodiments. However, the pipe  51   c  of the present embodiment may include the third air flow path  58 . 
     Fifth Embodiment 
     Hereinafter, a fifth embodiment of the gas turbine equipment according to the present invention will be described with reference to  FIGS. 12 and 13 . The gas turbine equipment of the present embodiment differs from the gas turbine equipment of the second embodiment only in the configuration of the transition piece of the combustor. Therefore, hereinafter, a configuration of a transition piece  50   d  of the present embodiment will be mainly described. 
     Similarly to the second embodiment, the transition piece  50   d  of the present embodiment includes the pipe  51   a ; the acoustic damper  61 ; the cooling air jacket  65 ; and the attachment flange  66 . Similarly to the pipe  51   a  of the second embodiment, the pipe  51   a  includes the inlet opening  54   i ; the outlet opening  54   o ; the outer peripheral surface  55   o ; the inner peripheral surface  55   i ; a plurality of the first air flow paths  56 ; and a plurality of the third air flow paths  58 . The pipe  51   a  of the present embodiment further includes a plurality of the second air flow paths  57 . The pipe  51   a  of the present embodiment includes the third air flow path  58 , but may not include the third air flow path  58 . 
     Also in the present embodiment, similarly to the second embodiment, the enhanced cooling air Acl in the cooling air space Sa flows into the first air flow path  56  and the third air flow path  58  of the pipe  51   a , and flows through the air flow paths  56  and  58 . The enhanced cooling air Acl is heated while cooling the pipe  51   a  because of heat exchange with the pipe  51   a , which is exposed to the high-temperature combustion gas G, in the process of flowing through the air flow paths  56  and  58 . The enhanced cooling air Acl that has passed through the third air flow path  58  flows out to the outer space So from the outlet  58   o  of the third air flow path  58 , and is mixed with the compressed air Acom present in the outer space So. In addition, the enhanced cooling air Acl that has passed through the first air flow path  56  flows from an outlet  156   o  of the first air flow path  56  into the acoustic space Ss. 
     The compressed air Acom in the outer space So flows into the second air flow path  57  from the inlet  57   i  of the second air flow path  57  to flow through the second air flow path  57 . The compressed air Acom is heated while cooling the pipe  51   a  because of heat exchange with the pipe  51   a , which is exposed to the combustion gas G, in the process of flowing through the second air flow path  57 . The compressed air Acom that has passed through the second air flow path  57  flows from the outlet  57   o  of the second air flow path  57  into the acoustic space Ss. 
     Therefore, in the present embodiment, the enhanced cooling air Acl that has flowed through the first air flow path  56  and the compressed air Acom that has flowed through the second air flow path  57  flows into the acoustic space Ss from the outlet  156   o  and the outlet  57   o , respectively. The air that has flowed into the acoustic space Ss flows out to the combustion space Sc through the acoustic hole  59 . As described above, in the present embodiment, similarly to the first embodiment, since the air flowing out from the acoustic space Ss to the combustion space Sc through the acoustic hole  59  includes the enhanced cooling air Acl that has flowed through the first air flow path  56 , the air having a large amount of heating of the air is capable of flowing out to the combustion space Sc. Therefore, also in the present embodiment, similarly to the second embodiment, while the air is allowed to flow out from the acoustic space Ss to the combustion space Sc, the mass flow rate of the air can be suppressed. 
     In the second embodiment described above, the case has been depicted in which the opening area of the outlet  56   o  and the opening area of the outlet  57   o  are the same; however, in the present embodiment, the opening area of the outlet  156   o  that guides the enhanced cooling air Acl, which has passed through the first air flow path  56 , into the acoustic space Ss is larger than the opening area of the outlet  57   o  that guides the compressed air Acom, which has passed through the second air flow path  57 , into the acoustic space Ss. For this reason, in the present embodiment, the flow velocity of the enhanced cooling air Acl flowing from the outlet  156   o  into the acoustic space Ss can be made lower than the flow velocity of the enhanced cooling air Acl flowing from the outlet  56   o  into the acoustic space Ss in the second embodiment. Accordingly, since a reduction in static pressure in the acoustic space Ss due to the inflow of the enhanced cooling air Acl can be suppressed, the combustion gas G in the combustion space Sc can be more suppressed from flowing into the acoustic space Ss through the acoustic hole  59  than in the second embodiment. In addition, in the present embodiment, since the opening area of the outlet  156   o  of the first air flow path  56  allowing a larger mass flow rate than the second air flow path  57  is large, a reduction in static pressure in the acoustic space Ss can be efficiently suppressed. 
     Modification Example of Fifth Embodiment 
     In the fifth embodiment described above, the case has been depicted in which the outlet  156   o  having a larger opening area than that of the outlet  57   o  is formed in the pipe  51 . In other words, in the fifth embodiment, the case has been described in which one outlet  156   o  is provided in one first air flow path  56 . However, as illustrated in  FIG. 14 , a plurality of (for example, two) outlets  256   o  facing the acoustic space Ss may be provided in one first air flow path  56 . The total opening area of the plurality of outlets  256   o  provided in one first air flow path  56  is larger than the opening area of one outlet  57   o . Also in such a modification example of the fifth embodiment, similarly to the fifth embodiment, the combustion gas G can be suppressed from flowing into the acoustic space Ss by reducing the flow velocity of the enhanced cooling air Acl flowing into the acoustic space Ss. 
     In addition, instead of the outlet  56   o  of the third and fourth embodiments, the outlet  156   o  of the fifth embodiment or the outlets  256   o  of the modification example of the fifth embodiment may be provided. 
     INDUSTRIAL APPLICABILITY 
     According to one aspect of the present invention, while the air is allowed to flow out from the acoustic space of the acoustic damper to the space on the inner peripheral side of the pipe, the mass flow rate of the air can be suppressed. 
     REFERENCE SIGNS LIST 
     
         
         
           
               10 : Gas turbine 
               11 : Gas turbine rotor 
               15 : Gas turbine casing 
               16 : Intermediate casing 
               20 : Compressor 
               21 : Compressor rotor 
               22 : Rotor shaft 
               23 : Rotor blade row 
               25 : Compressor casing 
               26 : Stator vane row 
               30 : Turbine 
               31 : Turbine rotor 
               32 : Rotor shaft 
               33 : Rotor blade row 
               35 : Turbine casing 
               36 : Stator vane row 
               40 : Combustor 
               41 : Fuel nozzle 
               42 : Burner 
               43 : Frame 
               45 : Fuel line 
               46 : Fuel flow rate-regulating valve 
               50 ,  50   a ,  50   b ,  50   c ,  50   d : Transition piece (or combustion pipe) 
               51 ,  51   a ,  51   b ,  51   c : Pipe 
               52   i : Inner peripheral wall panel 
               52   o : Outer peripheral wall panel 
               53 : Groove 
               54   i : Inlet opening 
               54   o : Outlet opening 
               55   i : Inner peripheral surface 
               55   o : Outer peripheral surface 
               56 : First air flow path 
               56   i : Inlet 
               56   o ,  156   o ,  256   o : Outlet 
               57 : Second air flow path 
               57   i : Inlet 
               57   o : Outlet 
               58 : Third air flow path 
               58   i : Inlet 
               58   o : Outlet 
               59 : Acoustic hole 
               59   a : First acoustic hole 
               59   b : Second acoustic hole 
               61 : Acoustic damper 
               61   a : First acoustic damper 
               61   b : Second acoustic damper 
               62 : Acoustic cover 
               65 : Cooling air jacket 
               66 : Attachment flange 
               70 : Cooling device 
               71 : Cooling air line 
               72 : Air bleeding line 
               73 : Cooling air main line 
               74 : Cooling air branch line 
               75 : Cooler 
               76 : Boost compressor 
             A: Air 
             Acom: Compressed air 
             Acl: Enhanced cooling air 
             G: Combustion gas 
             Lcom: Combustor axis (or simply axis) 
             Lr: Rotor axis 
             Da: Rotor axial direction 
             Dau: Axial upstream side 
             Dad: Axial downstream side 
             Dc: Circumferential direction 
             Dr: Radial direction 
             Dri: Radial inner side 
             Dro: Radial outer side 
             Dcom: Combustor axial direction (or simply axial direction) 
             Dcu: Combustor upstream side (or simply upstream side) 
             Dcd: Combustor downstream side (or simply downstream side) 
             Sc: Combustion space 
             Ss: Acoustic space 
             Ssa: First acoustic space 
             Ssb: Second acoustic space 
             Sa: Cooling air space 
             So: Outer space