Patent Publication Number: US-2023151965-A1

Title: Gas turbine combustor

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional application of U.S. patent application Ser. No. 17/165,147, filed on Feb. 2, 2021, which is based upon and claims the benefit of priority from Japanese Patent Application No. 2020-020881, filed on Feb. 10, 2020; the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     Embodiments described herein relate generally to a gas turbine combustor. 
     BACKGROUND 
     Increasing the efficiency of power generation plants is in progress in response to demands for reduction of carbon dioxide, resource conservation, and the like. Specifically, increasing the temperature of a working fluid of a gas turbine, employing a combined cycle, and the like are actively in progress. Further, research and development of collection techniques of carbon dioxide are also in progress. 
     Under such circumstances, a gas turbine facility including a combustor which combusts a fuel and oxygen in a supercritical CO 2  atmosphere (to be referred to as a CO 2  gas turbine facility, hereinafter) is under consideration. In this CO 2  gas turbine facility, a part of a combustion gas produced in the combustor is circulated in a system as a working fluid. 
     Therefore, in the CO 2  gas turbine facility, excess oxygen and fuel preferably do not remain in the combustion gas discharged from the combustor. Thus, flow rates of the fuel and an oxidant are regulated so as to have a stoichiometric mixture ratio (equivalence ratio 1), for example. 
     Incidentally, the equivalence ratio which is mentioned here is an equivalence ratio calculated based on a fuel flow rate and an oxygen flow rate. In other words, it is an equivalence ratio when it is assumed that the fuel and the oxygen are uniformly mixed (overall equivalence ratio). 
     In the combustor of the CO 2  gas turbine facility, a fuel-oxidant mixture mixed in the combustor is ignited by using an ignition device. At present, as the ignition device included in the combustor of the CO 2  gas turbine facility, a laser spark ignition device is under consideration. The laser ignition device irradiates the mixture inside the combustor with laser light to cause ignition. 
     The laser spark ignition device includes a laser oscillator, a lens, a heat-resistant glass provided in a casing part, and a laser passage pipe coupling a casing and a combustor liner, for example. Then, the interior of the combustor liner is irradiated through the lens, the heat-resistant glass, and the laser passage pipe with laser light emitted from the laser oscillator. 
     Then, the laser light is focused in the combustor liner. By the laser light being focused, an energy density increases. Then, gas in the portion where the energy density increases is plasmatized (breaks down) to ignite the mixture. 
     In the above-described laser ignition device of the CO 2  gas turbine facility, the combustion gas sometimes flows into the laser passage pipe. Then, an inner surface of the heat-resistant glass is exposed to the combustion gas and impurities such as soot adhere to the inner surface of the heat-resistant glass in some cases. This sometimes causes a reduction in transmittance of the laser light passing through the heat-resistant glass, resulting in not enabling stable ignition. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a system diagram of a gas turbine facility including a combustor of a first embodiment. 
         FIG.  2    is a view schematically illustrating a longitudinal section of the combustor of the first embodiment. 
         FIG.  3    is an enlarged view schematically illustrating a longitudinal section of an ignition device in the combustor of the first embodiment. 
         FIG.  4    is an enlarged view schematically illustrating a longitudinal section of the ignition device including another configuration in the combustor of the first embodiment. 
         FIG.  5    is a view schematically illustrating a longitudinal section of a combustor of a second embodiment. 
         FIG.  6    is an enlarged view schematically illustrating a longitudinal section of an ignition device in the combustor of the second embodiment. 
         FIG.  7    is an enlarged view schematically illustrating a longitudinal section of an ignition device in a combustor of a third embodiment. 
         FIG.  8    is an enlarged view schematically illustrating a longitudinal section of the ignition device including another configuration in the combustor of the third embodiment. 
         FIG.  9    is an enlarged view schematically illustrating a longitudinal section of an ignition device in a combustor of a fourth embodiment. 
         FIG.  10    is an enlarged view schematically illustrating a longitudinal section of an ignition device in a combustor of a fifth embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, embodiments of the present invention will be described with reference to the drawings. 
     In one embodiment, a gas turbine combustor includes: a casing; a combustion cylinder which is provided in the casing and combusts a fuel and an oxidant to produce a combustion gas; a pipe-shaped member provided to penetrate the casing and the combustion cylinder; a heat-resistant glass which is provided on the casing side in the pipe-shaped member and closes the pipe-shaped member; a laser light supply mechanism which irradiates an interior of the combustion cylinder through the heat-resistant glass and an interior of the pipe-shaped member with a laser light; and a contact prevention mechanism which prevents a combustion gas in the combustion cylinder from coming into contact with the heat-resistant glass. 
     First Embodiment 
       FIG.  1    is a system diagram of a gas turbine facility  10  including a combustor  20 A of a first embodiment. As illustrated in  FIG.  1   , the gas turbine facility  10  includes the combustor  20 A which combusts a fuel and an oxidant, a pipe  40  which supplies the fuel to the combustor  20 A, and a pipe  41  which supplies the oxidant to the combustor  20 A. Further, the combustor  20 A includes an ignition device  100 A which ignites a mixture of the fuel and the oxidant in the combustor  20 A. Note that the combustor  20 A functions as a gas turbine combustor. 
     The pipe  40  includes a flow rate regulating valve  21  which regulates a flow rate of the fuel to be supplied into a combustor liner  61  of the combustor  20 A. Here, as the fuel, for example, hydrocarbon such as methane or natural gas is used. Further, as the fuel, for example, a coal gasification gas fuel containing carbon monoxide, hydrogen, and the like can also be used. Note that the combustor liner  61  functions as a combustion cylinder. 
     The pipe  41  is provided with a compressor  23  which pressurizes the oxidant. As the oxidant, for example, oxygen separated from the atmosphere by an air separating apparatus (not illustrated) is used. The oxidant flowing through the pipe  41  is heated by passing through a heat exchanger  24  to be supplied to the combustor  20 A. 
     The fuel and the oxidant guided to the combustor liner  61  undergo reaction (combustion) in a combustion region in the combustor liner  61  and are turned into a combustion gas. Here, in the gas turbine facility  10 , a part of the combustion gas exhausted from a turbine  25  is circulated in the system, which is described later. Therefore, excess oxidant (oxygen) and fuel preferably do not remain in the combustion gas discharged from the combustor liner  61 . 
     Thus, flow rates of the fuel and the oxidant are regulated so as to have a stoichiometric mixture ratio (equivalence ratio 1), for example. Note that the equivalence ratio mentioned here is an equivalence ratio (overall equivalence ratio) when it is assumed that the fuel and the oxygen are uniformly mixed. 
     Further, the gas turbine facility  10  includes a turbine  25 , a generator  26 , a heat exchanger  24 , a cooler  27 , and a compressor  28 . Moreover, the gas turbine facility  10  includes a pipe  42  for circulating a part of the combustion gas discharged from the turbine  25  in the system. 
     The turbine  25  is moved rotationally by the combustion gas discharged from the combustor liner  61 . To the turbine  25 , for example, the generator  26  is coupled. The combustion gas discharged from the combustor liner  61 , which is mentioned here, is one containing a combustion product produced from the fuel and the oxidant and carbon dioxide to be circulated in the combustor liner  61  (a combustion gas from which water vapor has been removed). 
     The combustion gas discharged from the turbine  25  is guided to the pipe  42  and cooled by passing through the heat exchanger  24 . At this time, the oxidant flowing through the pipe  41  and carbon dioxide flowing through the pipe  42  to be circulated through the combustor  20 A are heated by heat release from the combustion gas. 
     The combustion gas having passed through the heat exchanger  24  passes through the cooler  27 . By the combustion gas passing through the cooler  27 , the water vapor contained in the combustion gas is removed therefrom. At this time, the water vapor in the combustion gas condenses into water. This water is discharged through a pipe  43  to the outside, for example. 
     Here, as described previously, when the flow rates of the fuel and the oxidant are regulated so as to have the stoichiometric mixture ratio (equivalence ratio 1), most of components of the combustion gas (dry combustion gas) from which the water vapor has been removed are carbon dioxide. Note that, for example, a slight amount of carbon monoxide, or the like is sometimes mixed in the combustion gas from which the water vapor has been removed, but hereinafter, the combustion gas from which the water vapor has been removed is simply referred to as carbon dioxide. 
     The carbon dioxide is pressurized to a pressure equal to or more than a critical pressure by the compressor  28  interposed in the pipe  42  to become a supercritical fluid. A part of the pressurized carbon dioxide flows through the pipe  42  and is heated in the heat exchanger  24 . Then, the carbon dioxide is guided between the combustor liner  61  and a cylinder body  80 . The temperature of the carbon dioxide having passed through the heat exchanger  24  becomes, for example, about 700° C. Note that the pipe  42  which supplies carbon dioxide between the combustor liner  61  and the cylinder body  80  also functions as a first fluid supply part. 
     Another part of the pressurized carbon dioxide is introduced to a pipe  44  branching off from the pipe  42 , for example. The carbon dioxide introduced to the pipe  44  is guided between a combustor casing  70  and the cylinder body  80  as a cooling medium after its flow rate is regulated by a flow rate regulating valve  29 . The temperature of the carbon dioxide guided between the combustor casing  70  and the cylinder body  80  by the pipe  44  is, for example, about 400° C. 
     This temperature of the carbon dioxide guided between the combustor casing  70  and the cylinder body  80  is lower than the previously-described temperature of the carbon dioxide guided between the combustor liner  61  and the cylinder body  80 . Note that the pipe  44  which supplies the carbon dioxide between the combustor casing  70  and the cylinder body  80  also functions as a first fluid supply part. Further, the combustor casing  70  functions as a casing. 
     Meanwhile, further another part of the pressurized carbon dioxide is introduced to a pipe  45  branching off from the pipe  42 . The carbon dioxide introduced to the pipe  45  is discharged to the outside after its flow rate is regulated by a flow rate regulating valve  30 . Note that the pipe  45  functions as a discharge pipe. The carbon dioxide discharged to the outside can be utilized for EOR (Enhanced Oil Recovery) or the like employed at an oil drilling field, for example. 
     Next, a configuration of the combustor  20 A of the first embodiment is described in detail. 
       FIG.  2    is a view schematically illustrating a longitudinal section of the combustor  20 A of the first embodiment.  FIG.  3    is an enlarged view schematically illustrating a longitudinal section of the ignition device  100 A in the combustor  20 A of the first embodiment. 
     As illustrated in  FIG.  2   , the combustor  20 A includes a fuel nozzle part  60 , the combustor liner  61 , a transition piece  62 , the combustor casing  70 , the cylinder body  80 , and the ignition device  100 A. 
     The fuel nozzle part  60  ejects the fuel supplied from the pipe  40  and the oxidant supplied from the pipe  41  into the combustor liner  61 . For example, the fuel is ejected from the center and the oxidant is ejected from the periphery of the center. 
     The combustor casing  70  is provided along a longitudinal direction of the combustor  20 A so as to surround a part of the fuel nozzle part  60 , the combustor liner  61 , and the transition piece  62 , for example. The combustor casing  70  is divided into two parts in the longitudinal direction of the combustor  20 A, for example. The combustor casing  70  is constituted of an upstream-side casing  71  on an upstream side and a downstream-side casing  72  on a downstream side, for example. 
     The upstream-side casing  71  is constituted by a cylinder body having one end (upstream end) thereof closed and the other end (downstream end) thereof opened, for example. In the center of the one end, an opening  71   a  into which the fuel nozzle part  60  is inserted is formed. Further, the pipe  44  is coupled to a side portion of the upstream-side casing  71 . The pipe  44  is fitted in and joined to an opening  71   b  formed in the side portion of the upstream-side casing  71 , for example. 
     The downstream-side casing  72  is constituted by a cylinder body having both ends thereof opened. One end of the downstream-side casing  72  is connected to the upstream-side casing  71 . The other end of the downstream-side casing  72  is connected to, for example, a casing surrounding the turbine  25 . 
     As illustrated in  FIG.  2   , in the combustor casing  70 , the cylinder body  80  which surrounds peripheries of a part of the fuel nozzle part  60 , the combustor liner  61 , and the transition piece  62  and demarcates a space between the combustor casing  70  and the combustor liner  61  is provided. Predetermined spaces exist between the combustor liner  61  and the cylinder body  80  and between the combustor casing  70  and the cylinder body  80 . 
     The cylinder body  80  has one end (upstream end) thereof closed, in which an opening  81  into which the fuel nozzle part  60  is inserted is formed. The cylinder body  80  has the other end (downstream end) thereof closed, in which an opening  82  through which a downstream end of the transition piece  62  penetrates is formed. The cylinder body  80  is formed by joining a plate-shaped lid member  80   a  having the opening  81  therein to a cylindrical main body member  80   b,  for example. 
     A configuration of the cylinder body  80  is not limited as long as the cylinder body  80  has a structure which surrounds the peripheries of a part of the fuel nozzle part  60 , the combustor liner  61 , and the transition piece  62  as illustrated in  FIG.  2   . 
     An inner peripheral surface of the downstream-side opening  82  in the cylinder body  80  is in contact with an outer peripheral surface of the downstream end portion of the transition piece  62 . 
     Further, the pipe  42  is coupled to an upstream-side side portion of the cylinder body  80 . The pipe  42  is coupled to the side portion of the cylinder body  80  by passing through the interior of the pipe  44  coupled to the side portion of the upstream-side casing  71 , as illustrated in  FIG.  2   , for example. The pipe  44  and the pipe  42  passes through the interior of the pipe  44  form a double-pipe structure. 
     Incidentally, the pipe  42  is inserted through an opening  44   a  formed in the pipe  44  into the interior of the pipe  44 , for example. Then, the pipe  42  is joined to the pipe  44  in an opening portion having the opening  44   a,  for example. Further, the double-pipe structure of the pipe  42  and the pipe  44  is not limited to being provided at one place and may be plurally provided in a circumferential direction. 
     The ignition device  100 A includes a pipe-shaped member  101 , a heat-resistant glass  102 , a laser light supply mechanism  103 , and a contact prevention mechanism  104 A as illustrated in  FIG.  2    and  FIG.  3   . 
     The pipe-shaped member  101  is constituted by a cylindrical pipe having both ends thereof opened, or the like. The pipe-shaped member  101  is provided to penetrate the combustor casing  70 , the cylinder body  80 , and the combustor liner  61 . In other words, the pipe-shaped member  101  is disposed so as to penetrate through a coaxial circular communication hole (through hole) formed in each of the combustor casing  70 , the cylinder body  80 , and the combustor liner  61  from the direction perpendicular to the longitudinal direction of the combustor  20 A. 
     Incidentally, an inner end portion  101   a  of the pipe-shaped member  101  is configured not to project to the interior of the combustor liner  61 . Further, an inside diameter of the pipe-shaped member  101  is set to the extent that laser light is not hindered when it passes through the interior of the pipe-shaped member  101 . 
     The heat-resistant glass  102  is provided on the outer side (combustor casing  70  side) in the pipe-shaped member  101 . Specifically, the heat-resistant glass  102  is preferably provided in the pipe-shaped member  101  on a side close to the outside than a flow path between the combustor casing  70  and the cylinder body  80 , through which the carbon dioxide flows. For example, the heat-resistant glass  102  is provided on an outer end portion  101   b  side of the pipe-shaped member  101 . 
     The heat-resistant glass  102  is provided so as to close the interior of the pipe-shaped member  101 . This shuts off communication between the inside and the outside of the combustor  20 A. 
     The laser light supply mechanism  103  irradiates the interior of the combustor liner  61  through the heat-resistant glass  102  and the interior of the pipe-shaped member  101  with a laser light  110 . The laser light supply mechanism  103  includes a laser oscillator  103   a  and a condensing lens  103   b.    
     The condensing lens  103   b  is provided outside the combustor casing  70  (downstream-side casing  72 ) to face the heat-resistant glass  102 . That is, the condensing lens  103   b  is provided between the laser oscillator  103   a  and the heat-resistant glass  102 . A focal length and an installation position of the condensing lens  103   b  are set so as to have a focal point  11   a  at a position suitable for igniting the fuel-air mixture. 
     The laser oscillator  103   a  is disposed outside the combustor casing  70 . The laser oscillator  103   a  irradiates the interior of the combustor liner  61  through the condensing lens  103   b,  the heat-resistant glass  102 , and the interior of the pipe-shaped member  101  with the laser light  110 . That is, the laser oscillator  103   a  is disposed so as to be able to irradiate the interior of the combustor liner  61  with the laser light  110  by passing the laser light  110  through the condensing lens  103   b,  the heat-resistant glass  102 , and the interior of the pipe-shaped member  101  in this order. 
     Incidentally, the condensing lens  103   b  may be irradiated through an optical fiber with the laser light  110  oscillated by the laser oscillator  103   a.    
     The contact prevention mechanism  104 A prevents the combustion gas in the combustor liner  61  from coming into contact with the heat-resistant glass  102 . The contact prevention mechanism  104 A includes a fluid supply part  120  and an ejection part  130 . 
     The fluid supply part  120  supplies a fluid for preventing the contact between the combustion gas in the combustor liner  61  and the heat-resistant glass  102 . Note that the fluid for preventing the contact between the combustion gas in the combustor liner  61  and the heat-resistant glass  102  is hereinafter referred to as a contact prevention fluid. 
     The fluid supply part  120  supplies the contact prevention fluid between the combustor casing  70  and the combustor liner  61 . Here, specifically, the fluid supply part  120  supplies the contact prevention fluid between the combustor liner  61  and the cylinder body  80 . 
     Here, the fluid supply part  120  is constituted of the pipe  42  which circulates the carbon dioxide heated in the heat exchanger  24  between the combustor liner  61  and the cylinder body  80 . Note that, the fluid supply part  120  functions as the first fluid supply part, and the contact prevention fluid to be supplied by the fluid supply part  120  functions as a first fluid. 
     Further, the carbon dioxide supplied between the combustor liner  61  and the cylinder body  80  also functions as a cooling medium to cool the combustor liner  61  and the transition piece  62  other than the function as the contact prevention fluid. 
     The ejection part  130  ejects the contact prevention fluid into the pipe-shaped member  101 . The ejection part  130  has a plurality of ejection holes  131  formed in a circumferential direction of the pipe-shaped member  101 . 
     The ejection part  130  is formed in the pipe-shaped member  101  located between the combustor liner  61  and the cylinder body  80 , for example. In other words, the ejection holes  131  are formed in the circumferential direction of the pipe-shaped member  101  located between the combustor liner  61  and the cylinder body  80 . 
     The ejection hole  131  is constituted by a circular hole, a slit, or the like. Further, the ejection holes  131  are disposed uniformly in the circumferential direction of the pipe-shaped member  101 . The ejection holes  131  each penetrate in a direction perpendicular to a center axis of the pipe-shaped member  101 , for example. 
     Here, a pressure of the contact prevention fluid to be ejected into the pipe-shaped member  101  is higher than a pressure in the combustor liner  61 . Therefore, the combustion gas flowing into the pipe-shaped member  101  does not pass through the ejection holes  131  to flow in between the combustor liner  61  and the cylinder body  80 . In other words, the contact prevention fluid ejected from the ejection holes  131  into the pipe-shaped member  101  flows into the combustor liner  61 . 
     Next, the operation of the combustor  20 A is described. 
     At the time of ignition, the laser oscillator  103   a  is driven to oscillate the laser light  110 . The laser light  110  oscillated by the laser oscillator  103   a  passes through the condensing lens  103   b  and the heat-resistant glass  102  to enter the pipe-shaped member  101 . The laser light  110  having passed through the interior of the pipe-shaped member  101  is focused on the focal point  110   a  in a predetermined region in the combustor liner  61 . Note that the laser light  110  travels from the focal point  110   a  in a traveling direction while expanding a beam diameter. 
     After the irradiation of the interior of the combustor liner  61  with the laser light  110 , the fuel and the oxygen are ejected from the fuel nozzle part  60  into the combustor liner  61 . At this time, the fuel and the oxygen are ejected from the fuel nozzle part  60  in a state of the oxidant flow rate and the fuel flow rate being reduced in order to suppress a sudden heat load on the combustor  20 A. 
     The oxidant and the fuel ejected from the fuel nozzle part  60  flow while mixing together to create a mixture. Then, when the mixture flows to a high energy density position where the laser light is focused on the focal point  110   a,  the mixture is ignited. This initiates combustion. Note that drive of the ignition device  100 A is stopped when the combustion in the combustor liner  61  is stabilized, for example. 
     Then, after the ignition, the flow rate of the circulating carbon dioxide and the oxidant flow rate are increased to increase the pressure in the combustor, and at the same time, the fuel flow rate is increased to increase the combustion gas temperature in the combustor. Then, the fuel flow rate, the flow rate of the circulating carbon dioxide, and the oxidant flow rate are increased up to a rated load condition of the turbine. 
     Since the action of the combustion gas discharged from the combustor liner  61  has been already described with reference to  FIG.  1   , flows of the carbon dioxide introduced from the pipe  42  and the pipe  44  into the combustor  20 A are described here with reference to  FIG.  2    and  FIG.  3   . 
     A part of the carbon dioxide introduced from the pipe  42  into the cylinder body  80  functions as the contact prevention fluid. As illustrated in  FIG.  3   , a part of the carbon dioxide passes through the ejection holes  131  of the pipe-shaped member  101  to be ejected into the pipe-shaped member  101 . Note that in  FIG.  3   , flows of the contact prevention fluid (carbon dioxide) ejected from the ejection holes  131  are indicated by arrows. 
     The flows of the contact prevention fluid (carbon dioxide) ejected from the ejection holes  131  each travel in the direction perpendicular to the center axis of the pipe-shaped member  101 , and at the same time, turn to the combustor liner  61  side, as illustrated in  FIG.  3   , for example. That is, in the pipe-shaped member  101 , a flow field toward the interior of the combustor liner  61  is formed by the contact prevention fluid ejected from the ejection holes  131 . 
     Further, in the interior of the pipe-shaped member  101  being an inner side of the ejection holes  131 , such a flow field as to shut off a cross section of the interior of the pipe-shaped member  101  is formed by the contact prevention fluid ejected from the plurality of ejection holes  131  formed in the circumferential direction. 
     Here, the contact prevention fluid to be ejected from the ejection holes  131  preferably has a penetration force to the extent of being capable of reaching the vicinity of the center axis of the pipe-shaped member  101 . Specifically, the contact prevention fluid to be ejected from the ejection holes  131  preferably has a penetration force to the extent of coming into contact with an outer periphery of the laser light  110  (laser beam) passing through the center of the pipe-shaped member  101 , for example. 
     The above-described flows formed by the contact prevention fluid ejected from the ejection holes  131  prevent the combustion gas in the combustor liner  61  from flowing into the pipe-shaped member  101 . Alternatively, the flows formed by the contact prevention fluid ejected from the ejection holes  131  prevent the combustion gas flowing from the interior of the combustor liner  61  into the pipe-shaped member  101  from flowing into the side closer to the heat-resistant glass  102  from positions formed with the ejection holes  131 . 
     This makes it possible to prevent the combustion gas in the combustor liner  61  from coming into contact with the heat-resistant glass  102  (an inner surface  102   a  of the heat-resistant glass  102 ). Then, impurities such as soot contained in the combustion gas do not adhere to the inner surface  102   a  of the heat-resistant glass  102 . Therefore, it is possible to prevent a reduction in transmittance of the laser light  110  passing through the heat-resistant glass  102 . 
     Incidentally, the contact prevention fluid ejected from the ejection holes  131  into the pipe-shaped member  101  flows into the combustor liner  61 . The contact prevention fluid flowing into the combustor liner  61  is introduced into the transition piece  62  together with the combustion gas. 
     Here, a flow rate of the contact prevention fluid to be ejected to the pipe-shaped member  101  can be regulated by a hole diameter of the ejection hole  131  and the number of the ejection holes  131 . The flow rate of the contact prevention fluid to be ejected from the ejection holes  131  into the pipe-shaped member  101  is preferably a minimum flow rate which can prevent inflow of the combustion gas to the heat-resistant glass  102  side. 
     This allows flames to be formed in the combustor liner  61  without being affected by the contact prevention fluid flowing from the pipe-shaped member  101  into the combustor liner  61 . 
     On one hand, the remaining part of the carbon dioxide introduced from the pipe  42  into the cylinder body  80  flows through an annular space between the combustor liner  61  and the cylinder body  80  to the downstream side. At this time, the carbon dioxide cools the combustor liner  61  and the transition piece  62 . 
     Then, the carbon dioxide is introduced from, for example, holes  63 ,  64  of a porous film cooling part, dilution holes  65 , and the like in the combustor liner  61  and the transition piece  62  into the combustor liner  61  and the transition piece  62 . The carbon dioxide introduced into the combustor liner  61  and the transition piece  62  is introduced to the turbine  25  together with the combustion gas produced by the combustion. 
     As illustrated in  FIG.  2   , the low-temperature carbon dioxide flowing through the pipe  44  is guided to a double pipe constituted by the pipe  42  and the pipe  44 . The carbon dioxide guided to the double pipe passes through an annular passage between the pipe  42  and the pipe  44  to be guided between the combustor casing  70  and the cylinder body  80 . 
     The carbon dioxide guided between the combustor casing  70  and the cylinder body  80  flows through the annular space between the combustor casing  70  and the cylinder body  80  to the downstream side. At this time, the carbon dioxide cools the combustor casing  70 , the cylinder body  80 , and the pipe-shaped member  101  of the ignition device  100 A. This carbon dioxide is used also for cooling stator blades  85  and rotor blades  86  of the turbine  25 , for example. By such cooling, the temperature of the combustor casing  70  becomes, for example, about 400° C. 
     Therefore, it is possible to maintain the temperature of the combustor casing  70  with the heat-resistant glass  102  of the ignition device  100 A installed therein to about 400° C. even at the time of the turbine rated load of the CO 2  gas turbine facility. That is, the temperature of the heat-resistant glass  102  of the ignition device  100 A is maintained to about 400° C. 
     According to the combustor  20 A of the first embodiment as described above, including the contact prevention mechanism  104 A makes it possible to prevent the contact between the heat-resistant glass  102  included in the pipe-shaped member  101  of the ignition device  100 A and the combustion gas. Therefore, the impurities such as soot do not adhere to the inner surface  102   a  of the heat-resistant glass  102 . This prevents the reduction in transmittance of the laser light  110  passing through the heat-resistant glass  102 , resulting in enabling stable ignition. 
     Here, in the above-described embodiment, one example of the ejection holes  131  each penetrating in the direction perpendicular to the center axis of the pipe-shaped member  101  is indicated, but a configuration of the ejection hole  131  is not limited to this. 
       FIG.  4    is an enlarged view schematically illustrating a longitudinal section of the ignition device  100 A including another configuration in the combustor  20 A of the first embodiment. 
     As illustrated in  FIG.  4   , ejection holes  131  may each be formed to be inclined to the end portion  101   a  side of the pipe-shaped member  101  relative to the direction perpendicular to the center axis of the pipe-shaped member  101 . That is, the ejection holes  131  may each be formed to be inclined so that an outlet of the ejection hole  131  is located closer to the end portion  101   a  side of the pipe-shaped member  101  than an inlet of the ejection hole  131 . 
     In this case, the contact prevention fluid ejected from the ejection holes  131  has a component of velocity along the center axis of the pipe-shaped member  101 . This makes it likely to form a flow field of the contact prevention fluid having a penetration force to the extent of coming into contact with an outer periphery of the laser light  110  (laser beam) passing through the center of the pipe-shaped member  101 . Then, the interior of the combustor liner  61  is irradiated with the laser light  110  in a state of suppressing an influence from the contact prevention fluid. 
     Second Embodiment 
       FIG.  5    is a view schematically illustrating a longitudinal section of a combustor  20 B of a second embodiment.  FIG.  6    is an enlarged view schematically illustrating a longitudinal section of an ignition device  100 B in the combustor  20 B of the second embodiment. Note that in the following embodiment, the same constituent portions as those of the combustor  20 A of the first embodiment are denoted by the same reference signs, and redundant explanations are omitted or simplified. 
     The combustor  20 B of the second embodiment has the same configuration as that of the combustor  20 A of the first embodiment except a configuration of a contact prevention mechanism  104 B of the ignition device  100 B. Therefore, the configuration of the contact prevention mechanism  104 B is mainly described here. 
     As illustrated in  FIG.  5   , the ignition device  100 B includes a pipe-shaped member  101 , a heat-resistant glass  102 , a laser light supply mechanism  103 , and the contact prevention mechanism  104 B. 
     The contact prevention mechanism  104 B prevents a combustion gas in a combustor liner  61  from coming into contact with the heat-resistant glass  102 . The contact prevention mechanism  104 B includes a fluid supply part  140  and an ejection part  150 . 
     The fluid supply part  140  supplies a contact prevention fluid. The fluid supply part  140  supplies the contact prevention fluid between a combustor casing  70  and a cylinder body  80 . 
     Here, the fluid supply part  140  is constituted of a pipe  44  which circulates the carbon dioxide pressurized by the compressor  28  between the combustor casing  70  and the cylinder body  80 . Here, the carbon dioxide circulated by the pipe  44  is not heated in the heat exchanger  24 . 
     Incidentally, the fluid supply part  140  functions as a first fluid supply part, and the contact prevention fluid to be supplied by the fluid supply part  140  functions as a first fluid. 
     Further, the carbon dioxide supplied between the combustor casing  70  and the cylinder body  80  also functions as a cooling medium to cool the combustor casing  70 , the cylinder body  80  and the pipe-shaped member  101  of the ignition device  100 B other than the function as the contact prevention fluid. 
     The ejection part  150  ejects the contact prevention fluid into the pipe-shaped member  101 . The ejection part  150  has a plurality of ejection holes  151  formed in a circumferential direction of the pipe-shaped member  101 . 
     The ejection part  150  is formed in the pipe-shaped member  101  located between the combustor casing  70  and the cylinder body  80 , for example. In other words, the ejection holes  151  are formed in the circumferential direction of the pipe-shaped member  101  located between the combustor casing  70  and the cylinder body  80 . 
     A shape and a disposition configuration of the ejection holes  151  are the same as those of the ejection holes  131  of the first embodiment. Further, the ejection holes  151  each penetrate in a direction perpendicular to a center axis of the pipe-shaped member  101 , for example. 
     Incidentally, as exemplified by the first embodiment (refer to  FIG.  4   ), the ejection holes  151  may each be formed to be inclined to an end portion  101   a  side of the pipe-shaped member  101  relative to the direction perpendicular to the center axis of the pipe-shaped member  101 . An effect obtained by the above is the same as the effect described by the first embodiment. 
     Here, a pressure of the contact prevention fluid to be ejected into the pipe-shaped member  101  is higher than a pressure in the combustor liner  61 . Therefore, the combustion gas flowing into the pipe-shaped member  101  does not pass through the ejection holes  151  to flow in between the combustor casing  70  and the cylinder body  80 . In other words, the contact prevention fluid ejected from the ejection holes  151  into the pipe-shaped member  101  flows into the combustor liner  61 . 
     Next, the operation of the combustor  20 B is described. 
     Here, the operation of the contact prevention mechanism  104 B is described. 
     A part of the carbon dioxide introduced between the combustor casing  70  and the cylinder body  80  from the pipe  44  functions as the contact prevention fluid. As illustrated in  FIG.  6   , a part of the carbon dioxide passes through the ejection holes  151  of the pipe-shaped member  101  to be ejected into the pipe-shaped member  101 . Note that in  FIG.  6   , flows of the carbon dioxide (contact prevention fluid) ejected from the ejection holes  151  are indicated by arrows. 
     The flows of the carbon dioxide (contact prevention fluid) ejected from the ejection holes  151  are similar to the flows of the carbon dioxide (contact prevention fluid) ejected from the ejection holes  131  in the first embodiment. That is, the flows of the carbon dioxide (contact prevention fluid) ejected from the ejection holes  151  each travel in the direction perpendicular to the center axis of the pipe-shaped member  101 , and at the same time, turn to the combustor liner  61  side, as illustrated in  FIG.  6   , for example. 
     Further, in the interior of the pipe-shaped member  101  being an inner side of the ejection holes  151 , such a flow field as to shut off a cross section of the interior of the pipe-shaped member  101  is formed by the carbon dioxide ejected from the plurality of ejection holes  151  formed in the circumferential direction. 
     The flows formed by the carbon dioxide ejected from the ejection holes  151  prevent the combustion gas in the combustor liner  61  from flowing into the pipe-shaped member  101 . Alternatively, the flows formed by the carbon dioxide ejected from the ejection holes  151  prevent the combustion gas flowing from the interior of the combustor liner  61  into the pipe-shaped member  101  from flowing into the side closer to the heat-resistant glass  102  from positions formed with the ejection holes  151 . 
     This makes it possible to prevent the combustion gas in the combustor liner  61  from coming into contact with the heat-resistant glass  102  (an inner surface  102   a  of the heat-resistant glass  102 ). Then, impurities such as soot contained in the combustion gas do not adhere to the inner surface  102   a  of the heat-resistant glass  102 . Therefore, it is possible to prevent a reduction in transmittance of the laser light  110  passing through the heat-resistant glass  102 . 
     Incidentally, similarly to the first embodiment, a flow rate of the contact prevention fluid to be ejected to the pipe-shaped member  101  can be regulated by a hole diameter of the ejection hole  151  and the number of the ejection holes  151 . An effect obtained by the above is also the same as that of the first embodiment. 
     On one hand, the remaining part of the carbon dioxide introduced between the combustor casing  70  and the cylinder body  80  from the pipe  44  flows through an annular space between the combustor casing  70  and the cylinder body  80  to the downstream side. At this time, similarly to the first embodiment, the carbon dioxide cools the combustor casing  70 , the cylinder body  80  and the pipe-shaped member  101  of the ignition device  110 B. 
     According to the combustor  20 B of the second embodiment as described above, including the contact prevention mechanism  104 B makes it possible to prevent the contact between the heat-resistant glass  102  included in the pipe-shaped member  101  of the ignition device  100 B and the combustion gas. Therefore, the impurities such as soot do not adhere to the inner surface  102   a  of the heat-resistant glass  102 . This prevents the reduction in transmittance of the laser light  110  passing through the heat-resistant glass  102 , resulting in enabling stable ignition. 
     Third Embodiment 
       FIG.  7    is an enlarged view schematically illustrating a longitudinal section of an ignition device  100 C in a combustor  20 C of a third embodiment. 
     The combustor  20 C of the third embodiment has the same configuration as that of the combustor  20 A of the first embodiment except a configuration of a contact prevention mechanism  104 C of the ignition device  100 C. Therefore, the configuration of the contact prevention mechanism  104 C is mainly described here. 
     As illustrated in  FIG.  7   , the ignition device  100 C includes a pipe-shaped member  101 , a heat-resistant glass  102 , a laser light supply mechanism  103 , and the contact prevention mechanism  104 C. 
     The contact prevention mechanism  104 C prevents a combustion gas in a combustor liner  61  from coming into contact with the heat-resistant glass  102 . The contact prevention mechanism  104 C includes an annular groove  160 , a flow path  161 , a fluid supply part  170  and an ejection part  180 . 
     The annular groove  160  is formed around a periphery of the pipe-shaped member  101  in a combustor casing  70  (for example, a downstream-side casing  72 ) through which the pipe-shaped member  101  penetrates. The annular groove  160  is formed on a side closer to a combustor liner  61  from the heat-resistant glass  102  in the combustor casing  70 . 
     The flow path  161  is a flow path coupling the outside of the combustor casing  70  and the annular groove  160 . The flow path  161  is constituted by a through hole penetrating from a side surface of the combustor casing  70  to the annular groove  160 . 
     The fluid supply part  170  supplies a contact prevention fluid to the flow path  161 . Specifically, the fluid supply part  170  is coupled to the flow path  161 . 
     Here, the fluid supply part  170  may be constituted by a pipe branching off from the pipe  42  which circulates the carbon dioxide heated in the heat exchanger  24  between the combustor liner  61  and the cylinder body  80  (refer to  FIG.  1   ), for example. 
     Further, the fluid supply part  170  may be constituted by a pipe branching off from the pipe  44  which circulates the carbon dioxide pressurized by the compressor  28  between the combustor casing  70  and the cylinder body  80  (refer to  FIG.  1   ), for example. 
     Here, when the fluid supply part  170  is constituted by each of the pipes branching off from the system of the gas turbine facility  10  as described above, a filter (not illustrated) is preferably interposed in the fluid supply part  170 . Passing through the filter enables removal of foreign matter contained in a flow of the carbon dioxide. This makes it possible to prevent the foreign matter from flowing into the combustor liner  61  and the turbine  25 . 
     Moreover, the fluid supply part  170  may be a supply system (supply pipe) other than the system of the gas turbine facility  10 , for example. Also in this case, the fluid supply part  170  supplies carbon dioxide at a supercritical pressure as the contact prevention fluid to the flow path  161 . 
     Here, even in any of the above-described configurations, the fluid supply part  170  supplies the contact prevention fluid to the flow path  161  so that a pressure of the contact prevention fluid to be ejected from the ejection part  180  into the pipe-shaped member  101  is higher than a pressure in the combustor liner  61 . 
     Incidentally, the fluid supply part  170  functions as a second fluid supply part. Further, the contact prevention fluid to be supplied from the fluid supply part  170  functions as a second fluid. 
     The ejection part  180  ejects the contact prevention fluid supplied to the annular groove  160  into the pipe-shaped member  101 . The ejection part  180  has a plurality of ejection holes  181  formed in a circumferential direction of the pipe-shaped member  101 . 
     The ejection part  180  is formed in the pipe-shaped member  101  in a position formed with the annular groove  160 , as illustrated in  FIG.  7   . In other words, the ejection holes  181  are formed in the circumferential direction of the pipe-shaped member  101  in the position formed with the annular groove  160 . 
     A shape and a disposition configuration of the ejection holes  181  are the same as those of the ejection holes  131  of the first embodiment. Further, the ejection holes  181  each penetrate in a direction perpendicular to a center axis of the pipe-shaped member  101 , for example. 
     Incidentally, as exemplified by the first embodiment (refer to  FIG.  4   ), the ejection holes  181  may each be formed to be inclined to an end portion  101   a  side of the pipe-shaped member  101  relative to the direction perpendicular to the center axis of the pipe-shaped member  101 . An effect obtained by the above is the same as the effect described by the first embodiment. 
     Here, the pressure of the contact prevention fluid to be ejected into the pipe-shaped member  101  is higher than the pressure in the combustor liner  61 . Therefore, the combustion gas flowing into the pipe-shaped member  101  does not pass through the ejection holes  181  to flow into the annular groove  160 . In other words, the contact prevention fluid ejected from the ejection holes  181  into the pipe-shaped member  101  flows into the combustor liner  61 . 
     Next, the operation of the combustor  20 C is described. 
     Here, the operation of the contact prevention mechanism  104 C is described. 
     The contact prevention fluid supplied from the fluid supply part  170  to the annular groove  160  expands in the circumferential direction in the annular groove  160 . The contact prevention fluid expanded in the circumferential direction in the annular groove  160  is ejected through the ejection holes  181  of the pipe-shaped member  101  into the pipe-shaped member  101 . Note that in  FIG.  7   , flows of the contact prevention fluid ejected from the ejection holes  181  are indicated by arrows. Further, a flow rate of the contact prevention fluid ejected from each of the ejection holes  181  is nearly uniform. Here, for example, fixing an end portion  101   b  on an outer side of the pipe-shaped member  101  to the combustor casing  70  by welding prevents the contact prevention fluid introduced to the annular groove  160  from leaking outside the combustor casing  70 . 
     The flows of the carbon dioxide (contact prevention fluid) ejected from the ejection holes  181  are similar to the flows of the carbon dioxide (contact prevention fluid) ejected from the ejection holes  131  in the first embodiment. That is, the flows of the contact prevention fluid ejected from the ejection holes  181  each travel in the direction perpendicular to the center axis of the pipe-shaped member  101 , and at the same time, turn to the combustor liner  61  side, as illustrated in  FIG.  7   , for example. 
     Further, in the interior of the pipe-shaped member  101  being an inner side of the ejection holes  181 , such a flow field as to shut off a cross section of the interior of the pipe-shaped member  101  is formed by the contact prevention fluid ejected from the plurality of ejection holes  181  formed in the circumferential direction. 
     The flows formed by the contact prevention fluid ejected from the ejection holes  181  prevent the combustion gas in the combustor liner  61  from flowing into the pipe-shaped member  101 . Alternatively, the flows formed by the contact prevention fluid ejected from the ejection holes  181  prevent the combustion gas flowing from the interior of the combustor liner  61  into the pipe-shaped member  101  from flowing into the side closer to the heat-resistant glass  102  from positions formed with the ejection holes  181 . 
     This makes it possible to prevent the combustion gas in the combustor liner  61  from coming into contact with the heat-resistant glass  102  (an inner surface  102   a  of the heat-resistant glass  102 ). Then, impurities such as soot contained in the combustion gas do not adhere to the inner surface  102   a  of the heat-resistant glass  102 . Therefore, it is possible to prevent a reduction in transmittance of the laser light  110  passing through the heat-resistant glass  102 . 
     Incidentally, similarly to the first embodiment, a flow rate of the contact prevention fluid to be ejected to the pipe-shaped member  101  can be regulated by a hole diameter of the ejection hole  181  and the number of the ejection holes  181 . An effect obtained by the above is also the same as that of the first embodiment. 
     According to the combustor  20 C of the third embodiment as described above, including the contact prevention mechanism  104 C makes it possible to prevent the contact between the heat-resistant glass  102  included in the pipe-shaped member  101  of the ignition device  100 C and the combustion gas. Therefore, the impurities such as soot do not adhere to the inner surface  102   a  of the heat-resistant glass  102 . This prevents the reduction in transmittance of the laser light  110  passing through the heat-resistant glass  102 , resulting in enabling stable ignition. 
     Here, a configuration of the contact prevention mechanism  104 C in the combustor  20 C is not limited to the above-described structure.  FIG.  8    is an enlarged view schematically illustrating a longitudinal section of the ignition device  100 C including another configuration in the combustor  20 C of the third embodiment. 
     As illustrated in  FIG.  8   , the contact prevention mechanism  104 C may be provided outside the combustor casing  70 . 
     In this case, the pipe-shaped member  101  is constituted by a cylindrical pipe having both ends thereof opened, or the like. The pipe-shaped member  101  is provided to penetrate the combustor casing  70 , the cylinder body  80  and the combustor liner  61 . 
     Further, one end side of the pipe-shaped member  101  projects from the combustor casing  70  to the outside. That is, the one end side of the pipe-shaped member  101  is extended to the outside of the combustor casing  70 . Note that in the pipe-shaped member  101 , a portion projecting from the combustor casing  70  to the outside is referred to as an outside projecting portion  101   e.    
     Further, on an outer periphery of the outside projecting portion  101   e  of the pipe-shaped member  101 , for example, a flange  101   c  is included. Then, attaching the flange  101   c  on an outer surface of the combustor casing  70  makes the pipe-shaped member  101  be fixed thereto. 
     The outside projecting portion  101   e  is provided with the contact prevention mechanism  104 C. Then, the heat-resistant glass  102  is disposed in the pipe-shaped member  101  on a side closer to the outside (laser light supply mechanism  103  side) than a position provided with the contact prevention mechanism  104 C. 
     The contact prevention mechanism  104 C includes an annular member  165 , a fluid supply part  170  and an ejection part  185 . 
     The annular member  165  is provided on the outer periphery of the outside projecting portion  101   e  over the circumferential direction, as illustrated in  FIG.  8   . A cross-sectional shape perpendicular to the circumferential direction in the annular member  165  is a U-shape. Then, the annular member  165  has a hollow portion. An open side (inner peripheral side) of the annular member  165  is joined to the outer periphery of the outside projecting portion  101   e.  By including the annular member  165  as described above, an annular passage  166  is formed on the outer periphery of the outside projecting portion  101   e.    
     Further, the annular member  165  is disposed between a position provided with the flange  101   c  and a position provided with the heat-resistant glass  102  in an axial direction of the pipe-shaped member  101 . 
     The fluid supply part  170  supplies the contact prevention fluid to the annular passage  166 . Specifically, the fluid supply part  170  is connected to the annular member  165 . Note that a pipe constituting the fluid supply part  170 , or the like is as previously described. 
     The ejection part  185  ejects the contact prevention fluid supplied to the annular passage  166  in the annular member  165  into the pipe-shaped member  101 . The ejection part  185  has a plurality of ejection holes  186  formed in a circumferential direction of the outside projecting portion  101   e.    
     The ejection holes  186  are formed in the pipe-shaped member  101  in a position formed with the annular passage  166 , as illustrated in  FIG.  8   . In other words, the ejection holes  186  are formed in the circumferential direction of the outside projecting portion  101   e  in the position formed with the annular passage  166 . A shape and a configuration of the ejection holes  186  are the same as the previously-described shape and configuration of the ejection holes  181 . 
     Here, the contact prevention fluid supplied from the fluid supply part  170  to the annular passage  166  expands in the circumferential direction in the annular passage  166 . Then, the contact prevention fluid expanded in the annular passage  166  is ejected from the ejection holes  186  into the pipe-shaped member  101 . Flows of the contact prevention fluid ejected from the ejection holes  186  into the pipe-shaped member  101  are similar to the previously-described flows of the contact prevention fluid ejected from the ejection holes  181  into the pipe-shaped member  101 . 
     Incidentally, a pressure of the contact prevention fluid to be ejected into the pipe-shaped member  101  is higher than a pressure in the combustor liner  61 . Therefore, the combustion gas flowing into the pipe-shaped member  101  does not pass through the ejection holes  186  to flow into the annular passage  166 . In other words, the contact prevention fluid ejected from the ejection holes  186  into the pipe-shaped member  101  flows into the combustor liner  61 . 
     Fourth Embodiment 
       FIG.  9    is an enlarged view schematically illustrating a longitudinal section of an ignition device  100 D in a combustor  20 D of a fourth embodiment. 
     The combustor  20 D of the fourth embodiment has the same configuration as that of the combustor  20 A of the first embodiment except a configuration of a contact prevention mechanism  104 D of the ignition device  100 D. Therefore, the configuration of the contact prevention mechanism  104 D is mainly described here. 
     As illustrated in  FIG.  9   , the ignition device  100 D includes a pipe-shaped member  101 , a heat-resistant glass  102 , a laser light supply mechanism  103 , and the contact prevention mechanism  104 D. 
     The contact prevention mechanism  104 D prevents a combustion gas in a combustor liner  61  from coming into contact with the heat-resistant glass  102 . The contact prevention mechanism  104 D includes an orifice member  190 . 
     The orifice member  190  is constituted by a circular plate-shaped member provided in the pipe-shaped member  101 . The orifice member  190  has a through hole  191  which passes a laser light  110  through the center thereof. 
     An outer periphery of the orifice member  190  is in contact with an inner periphery of the pipe-shaped member  101 . Such a configuration makes it possible to prevent the combustion gas from flowing from between the outer periphery of the orifice member  190  and an inner surface of the pipe-shaped member  101  into the heat-resistant glass  102  side. Note that an outer shape of the orifice member  190  is formed to correspond to a shape of an interior of the pipe-shaped member  101  in which the orifice member  190  is disposed. 
     A bore of the through hole  191  is set to a size to the extent that the laser light  110  is not prevented from passing therethrough. 
     Here, one example of including the orifice member  190  in the pipe-shaped member  101  between a combustor casing  70  and a cylinder body  80  is indicated, but this configuration is not restrictive. 
     For example, the orifice member  190  may be included in the pipe-shaped member  101  between a combustor liner  61  and the cylinder body  80 . 
     Here, since the laser light  110  is focused by a condensing lens  103   b,  a beam diameter of the laser light  110  is reduced to a focal point  110   a.  Therefore, including the orifice member  190  on the combustor liner  61  side allows the bore of the through hole  191  to be smaller. This makes it possible to more securely suppress a flow of the combustion gas flowing through the through hole  191  into the heat-resistant glass  102  side. 
     Next, the operation of the combustor  20 D is described. 
     Here, the operation of the contact prevention mechanism  104 D is described. 
     At the time of ignition, the laser light  110  oscillated by a laser oscillator  103   a  passes through the condensing lens  103   b,  the heat-resistant glass  102 , and the through hole  191  of the orifice member  190  to enter the pipe-shaped member  101 . The laser light  110  having passed through the interior of the pipe-shaped member  101  is focused on the focal point  110   a  in a predetermined region in the combustor liner  61 . 
     The inflow to the heat-resistant glass  102  side of the combustion gas flowing into the pipe-shaped member  101  is blocked by the orifice member  190 . Note that even though the combustion gas flows through the through hole  191  to the heat-resistant glass  102  side, a flow amount thereof is a very small amount. Therefore, impurities such as soot do not adhere to an inner surface  102   a  of the heat-resistant glass  102 . 
     According to the combustor  20 D of the fourth embodiment as described above, including the contact prevention mechanism  104 D makes it possible to suppress the contact between the heat-resistant glass  102  included in the pipe-shaped member  101  of the ignition device  100 D and the combustion gas. Therefore, the impurities such as soot do not adhere to the inner surface  102   a  of the heat-resistant glass  102 . This prevents the reduction in transmittance of the laser light  110  passing through the heat-resistant glass  102 , resulting in enabling stable ignition. 
     Here, a configuration of the combustor  20 D of the fourth embodiment is not limited to the above-described configuration. 
     For example, when the orifice member  190  is included in the pipe-shaped member  101  between the combustor casing  70  and the cylinder body  80 , the contact prevention mechanism  104 C of the third embodiment may be further included. Further, when the orifice member  190  is included in the pipe-shaped member  101  between the combustor casing  70  and the cylinder body  80 , the contact prevention mechanism  104 B of the second embodiment may be further included on the combustor casing  70  side of the orifice member  190 . 
     For example, when the orifice member  190  is included in the pipe-shaped member  101  between the combustor liner  61  and the cylinder body  80 , the contact prevention mechanism  104 B of the second embodiment or the contact prevention mechanism  104 C of the third embodiment may be further included. Further, when the orifice member  190  is included in the pipe-shaped member  101  between the combustor liner  61  and the cylinder body  80 , the contact prevention mechanism  104 A of the first embodiment may be further included on the combustor casing  70  side of the orifice member  190 . 
     In any of the cases, the contact prevention fluids ejected from the ejection holes  131 ,  151 ,  181  of the contact prevention mechanisms  104 A,  104 B,  104 C into the pipe-shaped member  101  each flow through the through hole  191  of the orifice member  190  to the combustor liner  61  side. This makes it possible to prevent the combustion gas from flowing through the through hole  191  to the heat-resistant glass  102  side. 
     Fifth Embodiment 
       FIG.  10    is an enlarged view schematically illustrating a longitudinal section of an ignition device  100 E in a combustor  20 E of a fifth embodiment. Note that  FIG.  10    illustrates a state where a shutoff valve  200  is opened. 
     The combustor  20 E of the fifth embodiment has the same configuration as that of the combustor  20 A of the first embodiment except a configuration of a contact prevention mechanism  104 E of the ignition device  100 E. Therefore, the configuration of the contact prevention mechanism  104 E is mainly described here. 
     As illustrated in  FIG.  10   , the ignition device  100 E includes a pipe-shaped member  101 , a heat-resistant glass  102 , a laser light supply mechanism  103 , and the contact prevention mechanism  104 E. 
     The pipe-shaped member  101  is constituted by a cylindrical pipe having both ends thereof opened, or the like. The pipe-shaped member  101  is provided to penetrate a combustor casing  70 , a cylinder body  80  and a combustor liner  61 . Further, one end side of the pipe-shaped member  101  projects from the combustor casing  70  to the outside. That is, the one end side of the pipe-shaped member  101  is extended to the outside of the combustor casing  70 . Note that in the pipe-shaped member  101 , a portion projecting from the combustor casing  70  to the outside is referred to as an outside projecting portion  101   e.    
     Further, on an outer periphery of the outside projecting portion  101   e  of the pipe-shaped member  101 , for example, a flange  101   c  is included. Then, attaching the flange  101   c  on an outer surface of the combustor casing  70  makes the pipe-shaped member  101  be fixed thereto. 
     The outside projecting portion  101   e  is provided with the contact prevention mechanism  104 E. Then, the heat-resistant glass  102  is disposed in the pipe-shaped member  101  on a side closer to the outside (laser light supply mechanism  103  side) than a position provided with the contact prevention mechanism  104 E. 
     The contact prevention mechanism  104 E prevents the combustion gas in the combustor liner  61  from coming into contact with the heat-resistant glass  102 . The contact prevention mechanism  104 E includes the shutoff valve  200 . 
     The shutoff valve  200  is provided in a side portion of the outside projecting portion  101   e.  The shutoff valve  200  is disposed between a position provided with a flange  101   c  and a position provided with the heat-resistant glass  12  in an axial position of the pipe-shaped member  101 . Then, the shutoff valve  200  communicates or shuts off a space  240   a  on the heat-resistant glass  102  side in the pipe-shaped member  101  and a space  240   b  on the combustor liner  61  side in the pipe-shaped member  101 . 
     The shutoff valve  200  includes valve casings  210 ,  220  and a shutoff portion  230 . 
     The valve casing  210  is constituted by a cylinder body having both ends thereof opened, or the like. As illustrated in  FIG.  10   , one end  210   a  of the valve casing  210  is fitted in and joined to an opening  101   d  formed in a sidewall of the outside projecting portion  101   e.  The other end  210   b  of the valve casing  210  has a flange  211 , for example. Note that the valve casing  210  may be formed integrally with the outside projecting portion  101   e.    
     The valve casing  220  is constituted by a cylinder body having both ends thereof opened, or the like. One end  220   a  of the valve casing  220  has a flange  221 , for example. One valve casing is constituted by fastening the flange  221  of the valve casing  220  and the flange  211  of the valve casing  210  with a bolt, for example. 
     The shutoff portion  230  shuts off space in the pipe-shaped member  101 . The shutoff portion  230  is provided to be movable forward and backward in the valve casings  210 ,  220 . For example, in a state where the shutoff portion  230  is closed, namely a closed state, the space  240   a  and the space  240   b  are shut off. Here, in the closed state, the combustion gas flowing into the space  240   b  does not flow to the space  240   a  side. 
     A sealing member  250  such as packing is provided on an inner wall  220   b  of the valve casing  220 . The shutoff portion  230  moves while coming into contact with the sealing member  250 . Thus, the valve casing  220  and the shutoff portion  230  are sealed therebetween by the sealing member  250 . 
     As the shutoff valve  200 , for example, a needle valve, a ball valve, or the like can be used. Note that the shutoff valve  200  is not limited to these. As long as the shutoff valve  200  is a one which can shut off the space  240   a  and the space  240   b  when the shutoff portion  230  is closed, the one can be used. 
     Next, the operation of the combustor  20 E is described. 
     Here, the operation of the contact prevention mechanism  104 E is described. 
     At the time of ignition, the shutoff portion  230  is opened. Therefore, a laser light  110  oscillated by a laser oscillator  103   a  passes through a condensing lens  103   b  and the heat-resistant glass  102  to enter the pipe-shaped member  101 . The laser light  110  having passed through the interior of the pipe-shaped member  101  is focused on a focal point  110   a  in a predetermined region in the combustor liner  61 . 
     After confirming the ignition, the oscillation of the laser light  110  by the laser oscillator  103   a  is stopped, and at same time, the shutoff portion  230  is closed. This causes the space  240   a  and the space  240   b  to be shut off. 
     Therefore, the inflow to the heat-resistant glass  102  side of the combustion gas flowing into the pipe-shaped member  101  is blocked by the shutoff portion  230 . This causes impurities such as soot not to adhere to an inner surface  102   a  of the heat-resistant glass  102 . 
     According to the combustor  20 E of the fifth embodiment as described above, including the contact prevention mechanism  104 E makes it possible to suppress the contact between the heat-resistant glass  102  included in the pipe-shaped member  101  of the ignition device  100 E and the combustion gas. Therefore, the impurities such as soot do not adhere to the inner surface  102   a  of the heat-resistant glass  102 . This prevents the reduction in transmittance of the laser light  110  passing through the heat-resistant glass  102 , resulting in enabling stable ignition. 
     According to the embodiments described above, it becomes possible to prevent the impurities such as soot from adhering to the heat-resistant glass of the laser ignition device and to perform stable ignition. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.