Patent Publication Number: US-9429326-B2

Title: Combustor nozzle assembly, combustor equipped with the same, and gas turbine

Description:
TECHNICAL FIELD 
     The present invention relates to a combustor nozzle assembly that injects fuel, a combustor equipped with the combustor nozzle assembly, and a gas turbine. Priority is claimed on Japanese Patent Application No. 2012-168535 filed on Jul. 30, 2012, the contents of which are incorporated herein by reference. 
     BACKGROUND ART 
     A combustor of a gas turbine includes a nozzle assembly having a nozzle which injects fuel into compressed air from a compressor of the gas turbine, and a transition piece which leads high-temperature gas generated by mixing fuel injected from a nozzle with the compressed air and burning the mixture, to a turbine. Although the present invention is not limited to this, as the nozzle, there is a so-called dual nozzle which injects both fuel oil and fuel gas. 
     The dual nozzle has a double-pipe structure, as shown in  FIG. 5  of, for example, Patent Document 1 below, and includes a tubular nozzle rod and a tubular oil fuel pipe which is disposed in the nozzle rod. In the nozzle rod, a gaseous fuel flow path, through which gaseous fuel passes, is formed in a portion further on the outer periphery side than a pipe insertion space in which the oil fuel pipe is inserted. Further, the nozzle rod is fixed to a nozzle mounting base which blocks a combustor insertion opening formed in a gas turbine casing. A pipe tip portion of the oil fuel pipe is fixed to a rod tip portion of the nozzle rod. A pipe base end portion of the oil fuel pipe protrudes from a rod base end portion of the nozzle rod and the nozzle mounting base and is inserted in an oil manifold fixed to the nozzle mounting base. Oil fuel is supplied into the oil manifold and flows in the oil fuel pipe from there. 
     When the oil fuel is injected from the dual nozzle and burned (an oil firing operation), the oil fuel pipe is cooled by the oil fuel which flows therein. On the other hand, since the nozzle rod is exposed to the flow of the compressed air from the compressor of the gas turbine, the nozzle rod is heated by the compressed air. For this reason, although the temperatures of the oil fuel pipe and the nozzle rod are uniform at the time of stopping of the gas turbine, during the oil firing operation of the gas turbine, the temperature of the nozzle rod becomes relatively high with respect to the temperature of the oil fuel pipe. Due to this difference in temperature, a difference in thermal expansion between the oil fuel pipe and the nozzle rod occurs. 
     Further, when gaseous fuel is injected from the dual nozzle and burned (a gas firing operation), the oil fuel pipe is not cooled by the oil fuel. For this reason, the oil fuel pipe has a temperature close to the temperature of the nozzle rod and becomes hotter than when the oil fuel is burned. However, the temperature of the oil fuel pipe does not rise as much as the temperature of the nozzle rod directly exposed to the flow of the compressed air. Accordingly, even during the gas firing operation of the gas turbine, a difference in temperatures between the oil fuel pipe and the nozzle rod occurs, and as a result, a difference in thermal expansion between the oil fuel pipe and the nozzle rod occurs. 
     In this manner, since a difference in thermal expansion between the oil fuel pipe and the nozzle rod occurs, although the pipe tip portion of the oil fuel pipe is fixed to the rod tip portion of the nozzle rod, the pipe base end portion of the oil fuel pipe is inserted in the oil manifold so as to be able to relatively move with respect to the oil manifold. An O-ring is disposed between the outer periphery of the pipe base end portion of the oil fuel pipe and the inner surface of the oil manifold in order to suppress leakage of the oil fuel from between them while allowing a difference in expansion of the oil fuel pipe. 
     Incidentally, in the dual nozzle described above, heat in the gas turbine casing is easily transmitted to the O-ring or a rod base end portion of an oil fuel rod through the nozzle mounting base and the oil manifold. For this reason, the O-ring sometimes gets damaged due to heat being applied in a short period of time. 
     Therefore, in Patent Document 1, as shown in FIGS. 2 and 3 of Patent Document 1, there is proposed a technique to insert the pipe base end portion of the oil fuel pipe into the oil manifold by separating the oil manifold from the nozzle mounting base and making the amount of protrusion of the oil fuel pipe from the nozzle mounting base large. In addition, in Patent Document 1, there is also proposed a technique to provide a leaked oil recovery chamber on the pipe tip portion side of the oil fuel pipe based on the O-ring in the oil manifold in order to prevent leakage of the oil fuel due to the damage to the O-ring. 
     PRIOR ART DOCUMENT 
     Patent Document 
     Patent Document 1: Japanese Unexamined Patent Application, First Publication No. 2008-190402 
     SUMMARY OF INVENTION 
     Problem to be Solved by the Invention 
     In the technique disclosed in Patent Document 1 above, since the amount of heat transferred to the O-ring is surely reduced, the O-ring can be prevented from being damaged in a short period of time. In addition, even if the O-ring is damaged, since the leaked oil recovery chamber is present, the oil fuel leaking outside can be prevented. However, in the technique disclosed in Patent Document 1 above, the leaked oil recovery chamber is provided, whereby a structure of the oil manifold becomes complicated, and in addition, a support which supports the oil manifold is separately required, and thus there is a problem in that the manufacturing cost increases. 
     The present invention has an object to provide a combustor nozzle assembly in which fuel leaking outside can be prevented even while reducing the manufacturing cost, a combustor equipped with the combustor nozzle assembly, and a gas turbine. 
     Means for Solving the Problems 
     According to a first aspect of the present invention, a combustor nozzle assembly includes: a nozzle mounting base which blocks a combustor insertion opening formed in a turbine casing; a nozzle rod which is formed in a tubular shape, passes through the nozzle mounting base, and has a rod tip portion protruding to the inside of the turbine casing and a rod base end portion protruding to the outside of the turbine casing; a fuel pipe which is formed in a tubular shape, which is as a whole inserted into the nozzle rod, which has a pipe tip portion fixed to the rod tip portion of the nozzle rod and a pipe base end portion inserted into the rod base end portion of the nozzle rod, in which fuel is supplied to the inside through the rod base end portion, and which injects the fuel from the pipe tip portion through the rod tip portion of the nozzle rod; and a seal member which is disposed in the rod base end portion of the nozzle rod and suppresses leakage of the fuel to the pipe tip portion side between the inner periphery side of the nozzle rod and the outer periphery side of the fuel pipe. 
     In the combustor nozzle assembly, since the seal member is disposed in the rod base end portion of the nozzle rod which protrudes to the outside of the turbine casing, heating of the seal member by heat from the nozzle mounting base or the like can be suppressed. Accordingly, in the combustor nozzle assembly, damage to the seal member due to heat can be suppressed. 
     In addition, in the combustor nozzle assembly, since the entire fuel pipe is inserted in the nozzle rod, even if the seal member which suppresses leakage of fuel to the pipe tip portion side between the inner periphery side of the nozzle rod and the outer periphery side of the fuel pipe is damaged, leakage of the fuel can be prevented because the fuel flows in between the inner peripheral surface of the nozzle rod and the outer peripheral surface of the fuel pipe. Accordingly, in the combustor nozzle assembly, since an oil manifold having a complicated shape, in which a leaked oil recovery chamber is formed, and a support thereof become unnecessary, the manufacturing cost can be reduced. 
     In the combustor nozzle assembly, the nozzle rod may have a mounting portion which is located in the nozzle mounting base, and a cross-sectional area reduced portion which is a portion between the mounting portion and the rod base end portion and in which a cross-sectional area in a cross section perpendicular to a direction in which the nozzle rod extends is smaller than the maximum cross-sectional area of the mounting portion. 
     Since the cross-sectional area reduced portion is interposed between the rod base end portion of the nozzle rod in the combustor nozzle assembly and the mounting portion which is located in the nozzle mounting base, the rod base end portion of the nozzle rod exists at a position relatively far from the nozzle mounting base. For this reason, heat that the rod base end portion of the nozzle rod receives from the nozzle mounting base can be reduced. Further, since the cross-sectional area of the cross-sectional area reduced portion of the nozzle rod is smaller than the maximum cross-sectional area of the mounting portion of the nozzle rod, thermal resistance in a heat transfer pathway from the nozzle mounting base or the like to the rod base end portion increases. 
     For this reason, in the combustor nozzle, damage to the seal member in the rod base end portion due to heat can be suppressed. 
     In the combustor nozzle assembly in which the nozzle rod has the cross-sectional area reduced portion, it is preferable that the cross-sectional area reduced portion of the nozzle rod be exposed to the outside of a combustor. 
     In the combustor nozzle assembly, since the cross-sectional area reduced portion between the mounting portion and the rod base end portion of the nozzle rod is exposed to the outside of the combustor, heat transmitted from the mounting portion to the cross-sectional area reduced portion can be released to the outside of the combustor. Accordingly, in the combustor nozzle assembly, heat which is transmitted from the cross-sectional area reduced portion to the rod base end portion can be reduced, and thus damage to the seal member due to a higher temperature can be suppressed. 
     Further, in either one of the combustor nozzle assemblies described above, the rod base end portion of the nozzle rod may be exposed to the outside of a combustor. 
     In the combustor nozzle assembly, heat transmitted to the rod base end portion can be released to the outside of the combustor. Accordingly, in the combustor nozzle assembly, heat which is transmitted from the rod base end portion to the seal member can be reduced, and thus damage to the seal member due to a higher temperature can be suppressed. 
     Further, either one of the combustor nozzle assemblies described above may further include a fuel receiving pipe which is connected to the rod base end portion of the nozzle rod and supplies the fuel into the fuel pipe through the rod base end portion. 
     In a case of supplying fuel into the fuel pipe through the rod base end portion of the nozzle rod, a method to cover the rod base end portion with a manifold for fuel supply and a method to provide a fuel receiving pipe, as in the combustor nozzle assembly described above, are conceivable. In the former method, since the rod base end portion is covered with the manifold for fuel supply, release of heat from the rod base end portion to the outside cannot be expected too much. On the other hand, in the latter method, since the rod base end portion is not covered with the manifold for fuel supply, release of heat from the rod base end portion to the outside can be expected. 
     Accordingly, in the combustor nozzle assembly, heat which is transmitted from the rod base end portion to the seal member can be reduced, and thus damage to the seal member due to a higher temperature can be suppressed. 
     According to a second aspect of the present invention, a combustor includes: either one of the combustor nozzle assemblies described above; and a transition piece which leads combustion gas generated by burning of fuel injected from the nozzle of the combustor nozzle assembly, to a turbine. 
     According to a third aspect of the present invention, a gas turbine includes: the combustor; a turbine rotor which is rotated by the combustion gas from the combustor; and the turbine casing which covers the turbine rotor and on which the combustor is mounted. 
     Effects of the Invention 
     In the present invention, even if an oil manifold having a complicated shape, in which a leaked oil recovery chamber is formed, is not provided, it is possible to prevent leakage of fuel. Further, since it is not necessary to provide a support, the manufacturing cost can be reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an overall side view, with a main section partially cut away, of a gas turbine according to an embodiment of the present invention. 
         FIG. 2  is a cross-sectional view of a surrounding of a combustor of the gas turbine according to an embodiment of the present invention. 
         FIG. 3  is a perspective view of a main section of a combustor nozzle assembly according to an embodiment of the present invention. 
         FIG. 4  is an overall cross-sectional view of a main nozzle according to an embodiment of the present invention. 
         FIG. 5  is a cross-sectional view of a base end portion of the main nozzle according to an embodiment of the present invention. 
         FIG. 6  is a cross-sectional view of a main section of a nozzle rod in a first modified example according to an embodiment of the present invention. 
         FIG. 7  is a cross-sectional view of a main section of a nozzle rod in a second modified example according to an embodiment of the present invention. 
         FIG. 8  is a cross-sectional view of a main section of a nozzle rod in a third modified example according to an embodiment of the present invention. 
         FIG. 9  is a cross-sectional view of a main section of a nozzle rod in a fourth modified example according to an embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, an embodiment of a combustor nozzle assembly, a combustor equipped with the combustor nozzle assembly, and a gas turbine according to an embodiment of the present invention will be described in detail referring to the drawings. 
     The gas turbine according to this embodiment includes a compressor  1  which compresses external air, thereby generating compressed air, a plurality of combustors  2  which mixes fuel from a fuel supply source with the compressed air and burns the mixture, thereby generating combustion gas, and a turbine  3  which is driven by the combustion gas, as shown in  FIG. 1 . 
     The turbine  3  includes a turbine casing  4  and a turbine rotor  5  which rotates in the turbine casing  4 . The turbine rotor  5  is connected to, for example, an electric generator (not shown) which generates electricity by rotation of the turbine rotor  5 . The plurality of combustors  2  are fixed to the turbine casing  4  at equal intervals with respect to each other in a circumferential direction with an axis of rotation Ar of the turbine rotor  5  as the center. The combustor  2  includes a transition piece  10  which sends high-temperature and high-pressure combustion gas to blades of the turbine rotor  5 , and a combustor nozzle assembly  20  which supplies the fuel and the compressed air into the transition piece  10 . In addition, in the following, the combustor nozzle assembly  20  is simply referred to as a nozzle assembly  20 . 
     The nozzle assembly  20  includes a pilot nozzle  21 , a plurality of main nozzles  31  which are disposed at equal intervals in the circumferential direction with the pilot nozzle  21  as the center, a nozzle mounting base  70  on which the pilot nozzle  21  and the plurality of main nozzles  31  are mounted, as shown in  FIG. 2 . 
     A combustor insertion opening  4   a  is formed in the turbine casing  4 . The nozzle mounting base  70  blocks the combustor insertion opening  4   a . The nozzle mounting base  70  has a nozzle stand  71  on which the pilot nozzle  21  and the plurality of main nozzles  31  are mounted, and a nozzle stand frame  75  to which the nozzle stand  71  is fixed. The nozzle stand frame  75  is fixed to the turbine casing  4  by bolts. 
     Both the pilot nozzle  21  and the main nozzle  31  are formed in a rod shape and directed in the same direction. Both the pilot nozzle  21  and the main nozzle  31  pass through the nozzle mounting base  70 . A tip portion  21   t  of the pilot nozzle  21  and a tip portion  31   t  of the main nozzle  31  protrude into the turbine casing  4 . Further, a base end portion  21   b  of the pilot nozzle  21  and a base end portion  31   b  of the main nozzle  31  protrude to the outside of the turbine casing  4 . In addition, in the following, a direction in which the pilot nozzle  21  and the main nozzle  31  extend is set to be a nozzle longitudinal direction D, a direction in which the tip portions  21   t  and  31   t  of the pilot nozzle  21  and the main nozzle  31  are directed, in the nozzle longitudinal direction D, is set to be a tip side Dt, and a direction in which the base end portions  21   b  and  31   b  of the pilot nozzle  21  and the main nozzle  31  are directed, in the nozzle longitudinal direction D, is set to be a base end side Db. 
     A P-oil fuel receiving pipe  81  which receives oil fuel Fpo and a P-gaseous fuel receiving pipe  82  which receives gaseous fuel Fpg are connected to the base end portion  21   b  of the pilot nozzle  21 . An oil fuel flow path (not shown) through which the oil fuel Fpo flows and a gaseous fuel flow path (not shown) through which the gaseous fuel Fpg flows are formed in the pilot nozzle  21 . Both the flow paths are opened at the tip portion  21   t  of the pilot nozzle  21  and the respective fuels Fpo and Fpg are injected from here. 
     The main nozzle  31  has a tubular nozzle rod  40 , and a tubular oil fuel pipe  60  which is as a whole inserted into the nozzle rod  40 . The nozzle rod  40  passes through the nozzle stand  71  of the nozzle mounting base  70 . A rod tip portion  41   t  of the nozzle rod  40  protrudes into the turbine casing  4  and also a rod base end portion  41   b  of the nozzle rod  40  protrudes to the outside of the turbine casing  4 . In the nozzle rod  40 , a mounting portion  41   a  which is located in the nozzle mounting base  70  is fixed to the nozzle stand  71  of the nozzle mounting base  70  by welding. In addition, since the entire oil fuel pipe  60  is inserted into the nozzle rod  40 , the rod tip portion  41   t  of the nozzle rod  40  forms the tip portion  31   t  of the main nozzle  31  and the rod base end portion  41   b  of the nozzle rod  40  forms the base end portion  31   b  of the main nozzle  31 . 
     An M-gaseous fuel receiving pipe  89  which receives gaseous fuel Fmg is connected to the outer periphery side of the nozzle stand  71 , as shown in  FIG. 4 . In the inside of the nozzle stand  71 , an annular fuel flow path  72  through which the gaseous fuel Fmg from the M-gaseous fuel receiving pipe  89  flows is formed at a position further on the outer periphery side than the plurality of main nozzles  31 . In addition, a branched flow path  73  which branches toward each main nozzle  31  from the annular fuel flow path  72  and an in-stand fuel space  74  which leads the gaseous fuel Fmg from the branched flow path  73 , to the surroundings of the mounting portion  41   a  of the nozzle rod  40 , are formed in the nozzle stand  71 . 
     In the rod base end portion  41   b  of the nozzle rod  40 , when the rod base end portion  41   b  is viewed in a direction from the base end side Db to the tip side Dt, a base end portion inner space  42  having a cylindrical shape is formed. An M-oil fuel receiving pipe  85  which receives oil fuel Fmo and communicates with the base end portion inner space  42  is connected to the rod base end portion  41   b . Further, a pipe insertion space  44  which extends from the base end portion inner space  42  to the rod tip portion  41   t  and in which the oil fuel pipe  60  is inserted is formed in the nozzle rod  40 . In addition, in the nozzle rod  40 , a gaseous fuel flow path  45  which extends from the mounting portion  41   a  of the nozzle rod  40  to the rod tip portion  41   t  of the nozzle rod  40  is formed at a position further on the outer periphery side than the pipe insertion space  44 . The gaseous fuel flow path  45  is opened at the mounting portion  41   a  and communicates with the in-stand fuel space  74 . Further, the gaseous fuel flow path  45  is opened at the rod tip portion  41   t  and this opening forms an injection port  46  for fuel. 
     A portion of the nozzle rod  40  between the rod base end portion  41   b  and the mounting portion  41   a  forms a cross-sectional area reduced portion  41   d  in which a cross-sectional area in a cross section perpendicular to the nozzle longitudinal direction D is smaller than the maximum cross-sectional area of the mounting portion  41   a . In addition, the cross-sectional area of the cross-sectional area reduced portion  41   d  is smaller than the maximum cross-sectional area of the rod base end portion  41   b  in a cross section perpendicular to the nozzle longitudinal direction D. 
     A pipe tip portion  61   t  of the oil fuel pipe  60  is disposed in the pipe insertion space  44  of the nozzle rod  40  and fixed at the position of the rod tip portion  41   t  of the nozzle rod  40  by welding. Further, a pipe base end portion  61   b  of the oil fuel pipe  60  extends to the inside of the rod base end portion  41   b  of the nozzle rod  40 . An oil fuel flow path  62  which passes through from the base end side Db of the oil fuel pipe  60  to the tip side Dt is formed in the oil fuel pipe  60 . The oil fuel flow path  62  is opened at the pipe base end portion  61   b  and the pipe tip portion  61   t . The oil fuel Fmo flows from an opening of the pipe base end portion  61   b  into the oil fuel flow path  62 , flows out from an opening of the pipe tip portion  61   t , and is injected from the injection port  46  of the nozzle rod  40  to the outside of the main nozzle  31 . 
     The main nozzle  31  has, in addition to the nozzle rod  40  and the oil fuel pipe  60  described above, a columnar inner piece  32  which is accommodated in the columnar base end portion inner space  42  of the nozzle rod  40 , a plurality of O-rings  36  as seal members, and an elastic body  37  such as a disk spring, as shown in  FIG. 5 . The main nozzle  31  further has a bolt  38  which presses the elastic body  37  while blocking an opening on the base end side Db of the rod base end portion  41   b  in the base end portion inner space  42 , and a packing  39  which seals the gap between a bolt head portion of the bolt  38  and the rod base end portion  41   b  of the nozzle rod  40 . 
     The inner piece  32  is accommodated in an area on the tip side Dt of the base end portion inner space  42  of the nozzle rod  40 . In the inner piece  32 , a pipe insertion space  33  in which the pipe base end portion  61   b  of the oil fuel pipe  60  is inserted, a communication path  34  which makes the oil fuel pipe  60  and the M-oil fuel receiving pipe  85  communicate with each other, and seal grooves  35 , in each of which each of the O-rings  36  is mounted, are formed. The communication path  34  also plays a role as an orifice which controls the flow rate of the oil fuel Fmo from the M-oil fuel receiving pipe  85 , thereby making the flow rate of the oil fuel Fmo which flows in the oil fuel pipe  60  to be a target flow rate. 
     As the seal grooves  35 , there are a first seal groove  35   a  which is formed in the outer peripheral surface of the columnar inner piece  32 , a second seal groove  35   b  which is formed in the end face on the tip side Dt of the inner piece  32 , and a third seal groove  35   c  which faces the pipe insertion space  33 . The each O-ring  36  is disposed in the seal groove  35 . O-rings  36   a  and  36   b  which are disposed in the first seal groove  35   a  and the second seal groove  35   b  serve to seal the gap between the outer surface of the inner piece  32  and the inner surface of the rod base end portion  41   b . Further, an O-ring  36   c  which is disposed in the third seal groove  35   c  serves to seal the gap between the inner surface of the inner piece  32  and the outer surface of the oil fuel pipe  60  while allowing thermal expansion and contraction of the oil fuel pipe  60  in the nozzle longitudinal direction D in the pipe insertion space  33  of the inner piece  32 . 
     Further, the O-ring  36   a  disposed in the first seal groove  35   a  seals the gap between the outer surface of the inner piece  32  and the inner surface of the rod base end portion  41   b , thereby suppressing leakage of the oil fuel Fmo from between these surfaces to the base end side Db. On the other hand, the O-ring  36   b  disposed in the second seal groove  35   b  and the O-ring  36   c  disposed in the third seal groove  35   c  seal the gap between the outer surface of the inner piece  32  and the inner surface of the rod base end portion  41   b  and the gap between the inner surface of the inner piece  32  and the outer surface of the oil fuel pipe  60 , thereby suppressing leakage of the oil fuel Fmo from between these surfaces to the tip side Dt. 
     The elastic body  37  is disposed in the base end portion inner space  42  further on the base end side Db than the inner piece  32  with an elasticity direction thereof directed in the nozzle longitudinal direction D. The elastic body  37  is pressed to the tip side Dt by the bolt  38  which blocks an opening of the rod base end portion  41   b , as described above. For this reason, the inner piece  32  is biased to the tip side Dt in the base end portion inner space  42  by the elastic body  37 . 
     The M-oil fuel receiving pipe  85  which is connected to the nozzle rod  40  has a plurality of connecting pipes  86  which connects the rod base end portions  41   b  of the nozzle rods  40  of the plurality of main nozzles  31  to each other, and a main receiving pipe  87  which supplies the oil fuel Fmo to one of the connecting pipes  86 , as shown in  FIG. 3 . The plurality of main nozzles  31  are disposed at equal intervals in the circumferential direction with the pilot nozzle  21  as the center, as described above. For this reason, the plurality of connecting pipes  86  which connects the rod base end portions  41   b  of the nozzle rods  40  of the plurality of main nozzles  31  to each other are arranged in the circumferential direction with the pilot nozzle  21  as the center. 
     During an oil firing operation of the gas turbine according to this embodiment, the oil fuel Fmo is supplied from the outside through the M-oil fuel receiving pipe  85  to the plurality of main nozzles  31 . The oil fuel Fmo flows in the base end portion inner space  42  of the nozzle rod  40  of the main nozzle  31 . The oil fuel Fmo flows in the oil fuel flow path  62  of the oil fuel pipe  60  inserted into the pipe insertion space  33  of the inner piece  32 , through the communication path  34  of the inner piece  32  disposed in the base end portion inner space  42 , and is injected from the injection port  46  of the nozzle rod  40  to the outside of the main nozzle  31 . The oil fuel Fmo injected to the outside of the main nozzle  31  is mixed and burned with the compressed air from the compressor  1 . The high-temperature and high-pressure combustion gas generated by this burning is led to the blades of the turbine rotor  5  by the transition piece  10 . 
     The oil fuel pipe  60  is cooled by the oil fuel flowing in the oil fuel pipe  60 . On the other hand, since the nozzle rod  40  is exposed to the flow of the high-temperature and high-pressure compressed air from the compressor  1 , the nozzle rod  40  is heated by this compressed air. For this reason, although the temperatures of the oil fuel pipe  60  and the nozzle rod  40  are uniform at the time of stopping of the gas turbine, during the oil firing operation, the temperature of the nozzle rod  40  becomes relatively high with respect to the temperature of the oil fuel pipe  60 . Due to this temperature difference, a difference in thermal expansion between the oil fuel pipe  60  and the nozzle rod  40  occurs. 
     During a gas firing operation of the gas turbine according to this embodiment, the gaseous fuel Fmg is supplied to the plurality of main nozzles  31  through the M-gaseous fuel receiving pipe  89 . The gaseous fuel Fmg flows from the M-gaseous fuel receiving pipe  89  into the annular fuel flow path  72  in the nozzle stand  71  and flows from there through the branched flow path  73  and the in-stand fuel space  74  in the nozzle stand  71  into the gaseous fuel flow path  45  in the nozzle rod  40 . 
     The gaseous fuel Fmg is injected from the injection port  46  of the nozzle rod  40  to the outside of the main nozzle  31 . 
     The gaseous fuel Fmg injected to the outside of the main nozzle  31  is mixed and burned with the compressed air from the compressor  1 , similar to the time of the oil firing operation. The high-temperature and high-pressure combustion gas generated by this burning is led to the blades of the turbine rotor  5  by the transition piece  10 . 
     During this gas firing operation, since the oil fuel Fmo is not supplied to the oil fuel pipe  60 , the oil fuel pipe  60  is not cooled by the oil fuel Fmo. For this reason, the oil fuel pipe  60  has a temperature close to the temperature of the nozzle rod  40  and becomes hotter than when the oil fuel is burned. However, the temperature of the oil fuel pipe  60  does not rise as much as the temperature of the nozzle rod  40  directly exposed to the flow of the compressed air. Accordingly, even during the gas firing operation and the oil firing operation, a difference in temperatures between the oil fuel pipe  60  and the nozzle rod  40  occurs, and due to this, a difference in thermal expansion between the oil fuel pipe  60  and the nozzle rod  40  occurs. 
     Incidentally, the pipe tip portion  61   t  of the oil fuel pipe  60  is fixed to the rod tip portion  41   t  of the nozzle rod  40  by welding, as described above. For this reason, if the length of the oil fuel pipe  60  relatively changes with respect to the length of the nozzle rod  40 , the relative position of the pipe base end portion  61   b  of the oil fuel pipe  60  changes with respect to the position of the rod base end portion  41   b  of the nozzle rod  40 . Specifically, since, for example, compared to the time of stopping of the gas turbine, the temperature of the oil fuel pipe  60  during the oil firing operation is relatively lowered with respect to the temperature of the nozzle rod  40 , the length of the oil fuel pipe  60  with respect to the length of the nozzle rod  40  becomes relatively short. Accordingly, during the oil firing operation, compared to the time of stopping of the gas turbine, the position of the pipe base end portion  61   b  of the oil fuel pipe  60  moves to the tip side Dt with respect to the position of the rod base end portion  41   b  of the nozzle rod  40 . 
     In this manner, according to an operating condition of the gas turbine, in the nozzle longitudinal direction D, the position of the pipe base end portion  61   b  of the oil fuel pipe  60  relatively moves with respect to the position of the rod base end portion  41   b  of the nozzle rod  40 . For this reason, the O-ring  36   c  which is disposed in the third seal groove  35   c  of the inner piece  32  disposed in the rod base end portion  41   b  of the nozzle rod  40  allows thermal expansion and contraction of the oil fuel pipe  60  in the nozzle longitudinal direction D in the pipe insertion space  33  of the inner piece  32  even while sealing the gap between the inner surface of the inner piece  32  and the outer surface of the oil fuel pipe  60 . 
     Further, the inner piece  32  in the rod base end portion  41   b  of the nozzle rod  40  tends to move in the same direction as the moving direction of the pipe base end portion  61   b  due to the movement of the pipe base end portion  61   b  of the oil fuel pipe  60 . In addition, a difference in thermal expansion also occurs between the rod base end portion  41   b  of the nozzle rod  40  and the inner piece  32 . Due to this difference in thermal expansion, the inner piece  32  tends to move in the rod base end portion  41   b  of the nozzle rod  40 . For this reason, the O-rings  36   a  and  36   b  which are disposed in the first and second seal grooves  35   a  and  35   b  of the inner piece  32  disposed in the rod base end portion  41   b  of the nozzle rod  40  allows movement in the nozzle longitudinal direction D of the inner piece  32  in the rod base end portion  41   b  of the nozzle rod  40  even while sealing the gap between the outer surface of the inner piece  32  and the inner surface of the rod base end portion  41   b.    
     Incidentally, the rod base end portion  41   b  of the nozzle rod  40  is provided to protrude to the outside of the turbine casing  4 . For this reason, it is difficult for the rod base end portion  41   b  of the nozzle rod  40  to receive heat from the nozzle mounting base  70 . Further, in the cross-sectional area reduced portion  41   d  of the nozzle rod  40 , as described above, the cross-sectional area in a cross section perpendicular to the nozzle longitudinal direction D is smaller than the maximum cross-sectional area in the mounting portion  41   a  of the nozzle rod  40 . For this reason, the cross-sectional area reduced portion  41   d  of the nozzle rod  40  increases thermal resistance in a heat transfer pathway from the turbine casing  4  to the rod base end portion  41   b . In addition, since the rod base end portion  41   b  of the nozzle rod  40  is exposed to the outside of the combustor  2 , a cooling effect by heat exchange with the outside can also be expected. Accordingly, in this embodiment, an increase in the temperature of the rod base end portion  41   b  of the nozzle rod  40  according to combustion of the fuel and an increase in the temperature of the O-ring  36  according to the increase in the temperature of the rod base end portion  41   b  can be suppressed. 
     Therefore, according to this embodiment, damage to the O-ring  36  due to heat can be suppressed, and thus the life of the O-ring  36  can be extended. 
     Further, in this embodiment, even if the O-rings  36   b  and  36   c  which prevent leakage of the oil fuel Fmo to the tip side Dt are damaged, leakage of the oil fuel Fmo to the outside can be prevented. This is because the oil fuel Fmo which has flowed in the base end portion inner space  42  of the nozzle rod  40  flows in a heat insulating space between the inner surface of the nozzle rod  40  and the outer surface of the oil fuel pipe  60  through the gap between the inner surface of the inner piece  32  and the outer surface of the oil fuel pipe  60  sealed by the O-ring  36   c  or the gap between the outer surface of the inner piece  32  and the inner surface of the rod base end portion  41   b  of the nozzle rod  40  sealed by the O-ring  36   b . That is, in this embodiment, the heat insulating space plays a role as a leaked oil recovery space at the time of damage to the O-rings  36   b  and  36   c.    
     Further, in this embodiment, even if the O-ring  36   a  which prevents leakage of the oil fuel Fmo to the base end side Db is damaged, since the packing  39  exists further to the base end side Db than the O-ring  36   a , leakage of the oil fuel Fmo to the outside can be prevented. Here, since the packing  39  is for sealing the gap between the bolt head portion of the bolt  38  and the rod base end portion  41   b  of the nozzle rod  40  which make little relative movement due to a change in temperature, the life of the packing  39  is longer than that of the O-ring  36   a . For this reason, leakage of the oil fuel Fmo to the outside due to damage to the packing  39  need not be considered as much as damage to the O-ring  36 . 
     Therefore, in this embodiment, since an oil manifold having a complicated shape, in which a leaked oil recovery chamber is formed, and a support thereof become unnecessary, the manufacturing cost can be reduced. 
     Next, various modified examples of the nozzle rod will be described using  FIGS. 6 to 9 . 
     First, a first modified example of the nozzle rod will be described using  FIG. 6 . 
     The shape of a nozzle rod  40   s  according to this modified example is slightly different from the shape of the nozzle rod  40  in the above-described embodiment. 
     In the nozzle rod  40   s  according to this modified example, a mounting portion  41   as  which is located in the nozzle mounting base  70  has a main mounting portion  41   ax  in which a cross-sectional area in a cross section perpendicular to the nozzle longitudinal direction D is the largest, and a reduced diameter portion  41   ay . The reduced diameter portion  41   ay  is formed on the base end side Db of the main mounting portion  41   ax  and the cross-sectional area of the reduced diameter portion  41   ay  is the same as the cross-sectional area of the cross-sectional area reduced portion  41   d  of the nozzle rod  40   s.    
     In this manner, even if the mounting portion  41   as  of the nozzle rod  40   s  has the reduced diameter portion  41   ay , if the cross-sectional area in a cross section perpendicular to the nozzle longitudinal direction D of the cross-sectional area reduced portion  41   d  is smaller than the maximum cross-sectional area of the mounting portion  41   as , thermal resistance in the heat transfer pathway from the turbine casing  4  to the rod base end portion  41   b  can be increased, similar to the above-described embodiment. 
     Next, a second modified example of the nozzle rod will be described using  FIG. 7 . 
     The shape of a nozzle rod  40   t  according to this modified example is also slightly different from the shape of the nozzle rod  40  in the above-described embodiment. 
     The outer diameter of a cross-sectional area reduced portion  41   dt  in the nozzle rod  40   t  according to this modified example is the same as the outer diameter of the mounting portion  41   a  and the inner diameter of the cross-sectional area reduced portion  41   dt  is larger than the inner diameter of the mounting portion  41   a . For this reason, in the cross-sectional area reduced portion  41   dt , the outer diameter of the cross-sectional area reduced portion  41   dt  becomes larger than the outer diameter of the cross-sectional area reduced portion  41   d  in the above-described embodiment. However, the cross-sectional area in a cross section perpendicular to the nozzle longitudinal direction D becomes smaller than the maximum cross-sectional area of the mounting portion  41   a  of the nozzle rod  40   t , similar to the above-described embodiment. For this reason, also in this modified example, similar to the above-described embodiment, thermal resistance in the heat transfer pathway from the turbine casing  4  to the rod base end portion  41   b  can be increased. 
     Next, a third modified example of the nozzle rod will be described using  FIG. 8 , and a fourth modified example of the nozzle rod will be described using  FIG. 9 . 
     A nozzle rod  40   u  according to the third modified example has the same shape as the nozzle rod  40  in the above-described embodiment. However, the nozzle rod  40   u  according to this modified example is formed by joining a member on the tip side Dt of the nozzle rod  40   u  and a member on the base end side Db of the nozzle rod  40   u  to each other by welding. Further, a nozzle rod  40   v  according to the fourth modified example has the same shape as the nozzle rod  40   t  according to the second modified example. However, the nozzle rod  40   v  according to this modified example is also formed by joining a member on the tip side Dt of the nozzle rod  40   v  and a member on the base end side Db of the nozzle rod  40   v  to each other by welding, similar to the third modified example. For this reason, in the nozzle rods  40   u  and  40   v  according to these modified examples, welded portions m exists in, for example, the cross-sectional area reduced portions  41   d  and  41   dt.    
     As in the nozzle rods  40   v  and  40   u  according to the third and fourth modified examples described above, even if the nozzle rod is formed by joining a member on the tip side Dt of the nozzle rod and a member on the base end side Db of the nozzle rod to each other by welding, basically the same effect as the nozzle rod  40  in the above-described embodiment or the nozzle rod  40   t  in the second modified example can be obtained. Further, in the nozzle rods  40   v  and  40   u  according to the third and fourth modified examples, if the welded portions m exist in the cross-sectional area reduced portions  41   d  and  41   dt , thermal resistance in the heat transfer pathway from the turbine casing  4  to the rod base end portion  41   b  can be further increased. 
     In addition, here, each of the nozzle rods  40   v  and  40   u  having the same shape as the nozzle rod  40  in the above-described embodiment or the nozzle rod  40   t  in the second modified example is formed by joining of two members by welding. However, a nozzle rod having the same shape as the nozzle rod  40   s  according to the first modified example may also be formed by joining of two members by welding. In addition, here, the nozzle rod is formed by joining two members by welding. However, an oil fuel pipe having the same shape as the oil fuel pipe  60  in the above-described embodiment may also be formed by joining two members by welding. 
     Further, in the above-described embodiment, for flow rate regulation or the like, the inner piece  32  is disposed in the base end portion inner space  42  of the nozzle rod  40 . However, the inner piece  32  may be omitted. In this case, a function to regulate the flow rate of the oil fuel Fmo is given to a portion which receives the oil fuel Fmo from the M-oil fuel receiving pipe  85 , in the base end portion inner space  42 . 
     In addition, the main nozzle  31  in the above-described embodiment is a so-called dual nozzle which injects both fuel oil and fuel gas. However, the invention is not limited thereto, and if a nozzle has a nozzle rod and an oil fuel pipe, a nozzle which does not inject fuel gas is also acceptable. 
     INDUSTRIAL APPLICABILITY 
     According to the combustor nozzle assembly, even if an oil manifold having a complicated shape, in which a leaked oil recovery chamber is formed, is not provided, it is possible to prevent leakage of fuel. Further, since it is also not necessary to provide a support, the manufacturing cost can be reduced. 
     REFERENCE SIGNS LIST 
       1 : compressor 
       2 : combustor 
       3 : turbine 
       4 : turbine casing 
       4   a : combustor insertion opening 
       5 : turbine rotor 
       10 : transition piece 
       20 : nozzle assembly 
       21 : pilot nozzle 
       31 : main nozzle 
       32 : inner piece 
       33 : pipe insertion space 
       36 : O-ring (seal member) 
       37 : elastic body 
       38 : bolt 
       39 : packing 
       40 ,  40   s ,  40   t ,  40   u ,  40   v : nozzle rod 
       41   b : rod base end portion 
       41   d ,  41   dt : cross-sectional area reduced portion 
       41   a : mounting portion 
       41   t : rod tip portion 
       42 : base end portion inner space 
       44 : pipe insertion space 
       45 : gaseous fuel flow path 
       46 : injection port 
       60 : oil fuel pipe 
       61   b : pipe base end portion 
       61   t : pipe tip portion 
       62 : oil fuel flow path 
       70 : nozzle mounting base 
       71 : nozzle stand 
       75 : nozzle stand frame