Combustor and gas turbine

Abstract

This combustor comprises a plurality of burner groups arranged in a circumferential direction with respect to a combustor axis. Each of the plurality of burner groups has a plurality of burners capable of injecting fuel together with compressed air. Each of the plurality of burners has an air flow passage frame through which air can flow and which can inject air, and a nozzle in which there is formed a fuel injection port through which fuel can be injected into the air flow passage frame. The air flow passage frame has an air inlet that is opened at an upstream-side end, and an air mixture outlet that is opened at a downstream-side end. The air mixture flow passage length, which is the distance in the direction of the combustor axis from the fuel injection port of the nozzle to the air mixture outlet of the air flow passage frame into which fuel is injected from the fuel injection port, is different between the burner groups that are adjacent to each other in the circumferential direction.

Description

Combustor and gas turbine

[0001] This application claims priority to Japanese Patent Application No. 2023-115975, filed on July 14, 2023, the contents of which are incorporated herein by reference.

[0002] A gas turbine includes a compressor that compresses air, a combustor that burns fuel with the air compressed by the compressor to generate combustion gas, and a turbine driven by the combustion gas from the combustor. The combustor has a cylindrical cylinder around the combustor axis that is capable of burning fuel on its inner periphery, and multiple burners that can inject fuel together with compressed air into the cylinder. Each of the multiple burners has an air flow path frame through which air can flow and that can inject air into the cylinder, and a nozzle that can inject fuel into the air flow path frame.

[0003] In a gas turbine described in Patent Document 1 below, combustion oscillation is suppressed by varying the mixture flow path lengths of multiple burners arranged in the radial direction. Note that the mixture flow path length here refers to the distance from the fuel injection port of a nozzle in a certain burner to the mixture outlet formed at the downstream end of the air flow path frame of that burner.

[0004] JP 2014-173840 A

[0005] An object of the present disclosure is to provide a technology that enables stable combustion of fuel.

[0006] To achieve the above object, one aspect of the present disclosure provides a combustor comprising: a cylinder that is tubular about a combustor axis and that defines, on an inner circumferential side, a combustion space in which fuel can be combusted; and a plurality of burner groups. Each of the plurality of burner groups includes a plurality of burners that can inject fuel together with compressed air into the cylinder. Each of the plurality of burners includes an air flow path frame through which air can flow and that can inject air into the cylinder, and a nozzle that is formed in the air flow path frame with a fuel ejection port that can inject fuel. The air flow path frame has an air inlet that opens at an upstream end of the air flow path frame and a mixture outlet that opens at a downstream end of the air flow path frame, on an upstream side and a downstream side in a combustor axial direction in which the combustor axis extends. A plurality of target burner groups that are at least some of the plurality of burner groups are aligned in a circumferential direction about the combustor axis. A mixture flow path length, which is the distance in the combustor axial direction from the fuel outlet of the nozzle to the mixture outlet of the air flow path frame through which fuel is ejected from the fuel outlet, is different between target burner groups adjacent in the circumferential direction.

[0007] When any one of the following fluctuations occurs: concentration fluctuation of the mixture at the mixture outlet, heat generation fluctuation due to combustion of the mixture injected from the burner into the cylinder, pressure fluctuation in the air passage frame, and velocity fluctuation of the mixture in the air passage frame, these fluctuations occur repeatedly. For example, when a concentration fluctuation occurs, it causes a heat generation fluctuation → pressure fluctuation → velocity fluctuation → concentration fluctuation to occur repeatedly in this order. If the positions of the mixture outlets of all burners in the combustor axial direction are the same and the mixture passage lengths of all burners are the same, the cycle of these fluctuations may lock at a specific frequency, causing combustion oscillation that may damage the burners or cylinders.

[0008] This combustion oscillation has multiple oscillation modes. A representative oscillation mode among the multiple oscillation modes is, for example, an inner-outer oscillation mode in which an annular node is formed around the combustor axis inside the cylinder. In this inner-outer oscillation mode, the direction of amplitude in a region on the inner periphery of the annular node is opposite to the direction of amplitude in a region on the outer periphery of the annular node.

[0009] In this aspect, the lengths of the mixture flow passages are different between the burner groups adjacent in the circumferential direction, so that even if any one of fluctuations among the concentration of the mixture at the mixture outlet, the heat generation fluctuation due to combustion of the mixture injected from the burner into the cylinder, the pressure fluctuation in the air flow passage frame, and the velocity fluctuation of the mixture in the air flow passage frame occurs, the frequencies of the cycles of the aforementioned fluctuations are different between the burner groups adjacent in the circumferential direction, making it possible to prevent the combustion oscillation from being locked into a specific internal / external oscillation mode.

[0010] In order to achieve the above object, a gas turbine according to one aspect of the present disclosure includes the combustor according to the aspect, a compressor capable of compressing air to generate compressed air, and a turbine capable of being driven by combustion gas generated by combustion of fuel in the combustion space, wherein the air flow path frame for each of the plurality of burner groups in the combustor is configured to allow the compressed air from the compressor to flow into the air flow path frame from the air inlet.

[0011] In one aspect of the present disclosure, fuel can be stably burned.

[0012] FIG. 1 is a schematic diagram showing a configuration of a gas turbine according to an embodiment of the present disclosure. FIG. 1 is a partial cross-sectional view of a combustor and its surroundings of a gas turbine according to an embodiment of the present disclosure. FIG. 2 is a view seen from an arrow III in FIG. 2. FIG. 3 is a cross-sectional view taken along line IV in FIG. 3. FIG. 4 is a perspective view of an air hole plate according to a first embodiment of the present disclosure. FIG. 5 is an explanatory view for explaining an internal and external vibration mode in combustion oscillation. FIG. 6 is a plan view of an air hole plate according to a second embodiment of the present disclosure. FIG. 7 is a cross-sectional view taken along line VIIIa in the outer region and line VIIIb in the inner region in FIG. 7. FIG. 8 is a perspective view of an air hole plate according to a second embodiment of the present disclosure. FIG. 9 is an explanatory view for explaining a circumferential vibration mode in combustion oscillation. FIG. 10 is a plan view of an air hole plate according to a third embodiment of the present disclosure. FIG. 11 is a cross-sectional view of an air hole plate according to a first modified example of the present disclosure. FIG. 12 is a cross-sectional view of an air hole plate according to a second modified example of the present disclosure taken along the outer periphery of a circle centered on the combustor axis.

[0013] Hereinafter, embodiments of a gas turbine operation method according to the present disclosure and a gas turbine facility capable of implementing this method will be described in detail with reference to the drawings.

[0014] "Embodiment of Gas Turbine" As shown in FIG. 1, the gas turbine in this embodiment includes a compressor 10 capable of compressing air A to generate compressed air Acom, a combustor 20 capable of burning fuel F in the compressed air Acom to generate combustion gas CG, and a turbine 15 capable of being driven by the combustion gas CG.

[0015] The compressor 10 has a compressor rotor 11 that rotates about a rotor axis Ar, and a compressor casing 12 that covers the compressor rotor 11. The turbine 15 has a turbine rotor 16 that rotates about the rotor axis Ar, and a turbine casing 17 that covers the turbine rotor 16. In the following description, the direction in which the rotor axis Ar extends is referred to as a rotor axial direction Da, and one of both sides of the rotor axial direction Da is referred to as an axial upstream side Dau, and the other is referred to as an axial downstream side Dad.

[0016] The compressor 10 is disposed on the axial upstream side Dau of the turbine 15. The compressor rotor 11 and the turbine rotor 16 are located on the same rotor axis Ar and are connected to each other to form a gas turbine rotor 2. To this gas turbine rotor 2, for example, a rotor of a generator GEN is connected.

[0017] The gas turbine 1 further includes an intermediate casing 3 disposed between the compressor casing 12 and the turbine casing 17. Compressed air Acom from the compressor 10 flows into the intermediate casing 3. The combustor 20 is attached to the intermediate casing 3.

[0018] A fuel supply system 30 is connected to the combustor 20. The combustor 20 is capable of burning fuel F from the fuel supply system 30 in compressed air Acom from the compressor 10 to generate combustion gas CG.

[0019] 2 , the combustor 20 includes an outer casing 21 o, an end cover 21 e, an inner casing 21 i, an air hole plate 23, a combustion casing 22 that defines a combustion space on the inner circumferential side in which fuel can be combusted, and a plurality of burner groups 26. The outer casing 21 o, the inner casing 21 i, and the combustion casing 22 are all cylindrically shaped around a combustor axis Ac. Here, the direction in which the combustor axis Ac extends is referred to as a combustor axial direction Dc, one side of the combustor axial direction Dc is simply referred to as an upstream side Dcu, and the other side of the combustor axial direction Dc is simply referred to as a downstream side Dcd.

[0020] The downstream end Dcd of the external cylinder 21o is connected to the intermediate casing 3. The upstream end Dcu of the external cylinder 21o is closed by the end cover 21e. The inner cylinder 21i is disposed on the inner circumferential side of the external cylinder 21o with a gap therebetween. A flow path for the compressed air Acom that has flowed into the intermediate casing 3 is formed between the inner circumferential side of the external cylinder 21o and the outer circumferential side of the inner cylinder 21i. The air hole plate 23 is disposed on the inner circumferential side of the inner cylinder 21i. The air hole plate 23 is also disposed on the end cover 21e with a gap therebetween in the combustor axial direction Dc. A flow path for the compressed air Acom is formed between the end cover 21e and the air hole plate 23. This flow path is connected to the flow path between the inner circumferential side of the external cylinder 21o and the outer circumferential side of the inner cylinder 21i. The air hole plate 23 is fixed to the end cover 21e via a support or the like. The inner cylinder 21i is fixed to an air hole plate 23. The air hole plate 23 has a downstream end face 23ds facing the downstream side Dcd and facing the combustion space, an upstream end face 23us facing the upstream side Dcu, and a plurality of air holes 23h penetrating from the upstream end face 23us to the downstream end face 23ds. The combustion cylinder 22 is fixed to the downstream side Dcd of the inner cylinder 21i. As described above, the inner peripheral side of this combustion cylinder 22 forms the combustion space where fuel is burned.

[0021] Each of the plurality of burner groups 26 has a plurality of burners 27 that can inject fuel F together with compressed air Acom into the combustion liner 22. For this reason, the combustor 20 in this embodiment is called a multi-cluster combustor. Each of the plurality of burners 27 has an air flow path frame 28 through which air can flow and that can inject air into the combustion liner 22, and a nozzle 29 in which a fuel ejection port 29o that can inject fuel is formed in the air flow path frame 28. The air flow path frame 28 has an air inlet 28i that opens at an end of the air flow path frame 28 on the upstream side Dcu, and an air-fuel mixture outlet 28o that opens at an end of the air flow path frame 28 on the downstream side Dcd.

[0022] The inner peripheral surface of the air flow path frame 28 of each burner 27 is formed by the inner peripheral surface of one of the plurality of air holes 23h of the air hole plate 23. Thus, each air flow path frame 28 is formed by a part of the air hole plate 23.

[0023] The nozzle 29 extends in the combustor axial direction Dc. A fuel ejection port 29o is formed at the end of the downstream side Dcd of the nozzle 29. The downstream side Dcd portion of the nozzle 29 is inserted into the air flow path frame 28, in other words, into the air hole 23h.

[0024] The fuel supply system 30 includes a main fuel line connected to a fuel supply source and a plurality of branch lines branching from the main fuel line, each of which is connected to one of the plurality of nozzles 29.

[0025] As described above, the compressed air Acom that has flowed into the intermediate casing 3 passes through the flow path between the inner circumferential side of the outer cylinder 21o and the outer circumferential side of the inner cylinder 21i and the flow path between the end cover 21e and the air hole plate 23, and then flows into the air flow path frame 28 for each of the multiple burners 27. The nozzles 29 for each of the multiple burners 27 inject fuel into the air flow path frame 28. As a result, an air-fuel mixture of air and fuel is formed in the air flow path frame 28. This air-fuel mixture is injected from the air flow path frame 28 for each of the multiple burners 27 into the combustion liner 22. The fuel injected into the combustion liner 22 is combusted therein. The combustion gas formed by this combustion flows into the turbine 15.

[0026] Detailed embodiments of the combustor will be described below. The configuration of the combustor described above is a common configuration among combustors in each of the embodiments described below.

[0027] "First embodiment of combustor" As shown in Figs. 3 to 5, an air hole plate 23 of a combustor in the present embodiment has a plurality of circumferential divided regions 25 arranged in a circumferential direction Dcc with respect to a combustor axis Ac. One of a plurality of burner groups 26 is provided in each of the plurality of circumferential divided regions 25. Fig. 3 is a view seen from an arrow III in Fig. 2. Fig. 4 is a cross-sectional view taken along line IV in Fig. 3. Fig. 5 is a perspective view of the air hole plate 23.

[0028] In the present embodiment, the number of the circumferentially divided regions 25 is six. The width angle of each of the circumferentially divided regions 25 in the circumferential direction Dcc relative to the combustor axis line Ac is the same among the circumferentially divided regions 25. Therefore, in the present embodiment, the width angle of one circumferentially divided region 25 is 60° (=360°÷6). In the present embodiment, among the plurality of circumferentially divided regions 25, a first circumferentially divided region 25a is a region ranging from 330° to 0° and 0° to 30° relative to the combustor axis line Ac. The second circumferentially divided region 25b is a region ranging from 30° to 90° relative to the combustor axis line Ac. The third circumferentially divided region 25c is a region ranging from 90° to 150° relative to the combustor axis line Ac. The fourth circumferentially divided region 25d is a region ranging from 150° to 210° relative to the combustor axis line Ac. The fifth circumferentially divided region 25e is a region from 210° to 270° relative to the combustor axis line Ac, and the sixth circumferentially divided region 25f is a region from 270° to 330° relative to the combustor axis line Ac.

[0029] In the present embodiment, all of the plurality of burner groups 26 are target burner groups. In the present embodiment, one of the plurality of burner groups 26 is provided in each of the plurality of circumferentially divided regions 25. Therefore, the plurality of burner groups 26 are aligned in the circumferential direction Dcc. Furthermore, the width angle of each of the plurality of burner groups 26 in the circumferential direction Dcc with respect to the combustor axis Ac is the same among the plurality of burner groups 26. In the following, the burner group 26 provided in the first circumferential divided region 25a will be referred to as the first burner group 26a, the burner group 26 provided in the second circumferential divided region 25b will be referred to as the second burner group 26b, the burner group 26 provided in the third circumferential divided region 25c will be referred to as the third burner group 26c, the burner group 26 provided in the fourth circumferential divided region 25d will be referred to as the fourth burner group 26d, the burner group 26 provided in the fifth circumferential divided region 25e will be referred to as the fifth burner group 26e, and the burner group 26 provided in the sixth circumferential divided region 25f will be referred to as the sixth burner group 26f.

[0030] 4 , the distance in the combustor axial direction Dc from the air inlet 28i of the air flow path frame 28 to the mixture gas outlet 28o of this air flow path frame 28 is defined as an air flow path length La. Furthermore, the distance in the combustor axial direction Dc from the fuel outlet 29o of the nozzle 29 to the mixture gas outlet 28o of the air flow path frame 28 into which this nozzle 29 is inserted is defined as a mixture gas flow path length Lm. Furthermore, the distance in the combustor axial direction Dc from the air inlet 28i of the air flow path frame 28 to the fuel outlet 29o of the nozzle 29 that ejects fuel into this air flow path frame 28 is defined as an insertion length Li. The air flow path length La, the mixture gas flow path length Lm, and the insertion length Li have the following relationship: La = Lm + Li

[0031] The positions in the combustor axial direction Dc of the mixture outlets 28o of all the air flow path frames 28 are the same. Therefore, the downstream end surface 23ds of the air hole plate 23, in which the mixture outlets 28o of each air flow path frame 28 are formed, is flat.

[0032] The mixture gas flow path length Lmb of the plurality of burners 27 constituting the second burner group 26b is shorter than the mixture gas flow path length Lma of the plurality of burners 27 constituting the first burner group 26a. The mixture gas flow path length Lmc of the plurality of burners 27 constituting the third burner group 26c is shorter than the mixture gas flow path length Lmb of the plurality of burners 27 constituting the second burner group 26b. The mixture gas flow path length Lmd of the plurality of burners 27 constituting the fourth burner group 26d is the same as the mixture gas flow path length Lmb of the plurality of burners 27 constituting the second burner group 26b. Therefore, the mixture gas flow path length Lmd of the plurality of burners 27 constituting the fourth burner group 26d is shorter than the mixture gas flow path length Lma of the plurality of burners 27 constituting the first burner group 26a and longer than the mixture gas flow path length Lmc of the plurality of burners 27 constituting the third burner group 26c. The mixture gas flow path length Lme of the plurality of burners 27 constituting the fifth burner group 26e is the same as the mixture gas flow path length Lmc of the plurality of burners 27 constituting the third burner group 26c. Therefore, the mixture gas flow path length Lme of the plurality of burners 27 constituting the fifth burner group 26e is shorter than the mixture gas flow path length Lma of the plurality of burners 27 constituting the first burner group 26a and the mixture gas flow path length Lmb of the plurality of burners 27 constituting the second burner group 26b. The mixture gas flow path length Lmf of the plurality of burners 27 constituting the sixth burner group 26f is the same as the mixture gas flow path length Lmb of the plurality of burners 27 constituting the second burner group 26b and the mixture gas flow path length Lmd of the plurality of burners 27 constituting the fourth burner group 26d. Therefore, the mixture flow path length Lmf of the plurality of burners 27 constituting the sixth burner group 26f is shorter than the mixture flow path length Lma of the plurality of burners 27 constituting the first burner group 26a, and longer than the mixture flow path length Lmc of the plurality of burners 27 constituting the third burner group 26c.

[0033] Therefore, in this embodiment, the mixture flow path length Lm differs between the burner groups 26 (or between the circumferential divided regions 25) adjacent to each other in the circumferential direction Dcc.

[0034] The air flow path length Lab of the plurality of burners 27 constituting the second burner group 26b is shorter than the air flow path length Laa of the plurality of burners 27 constituting the first burner group 26a. The air flow path length Lac of the plurality of burners 27 constituting the third burner group 26c is shorter than the air flow path length Lab of the plurality of burners 27 constituting the second burner group 26b. The air flow path length Lad of the plurality of burners 27 constituting the fourth burner group 26d is the same as the air flow path length Lab of the plurality of burners 27 constituting the second burner group 26b. Therefore, the air flow path length Lad of the plurality of burners 27 constituting the fourth burner group 26d is shorter than the air flow path length Laa of the plurality of burners 27 constituting the first burner group 26a and longer than the air flow path length Lac of the plurality of burners 27 constituting the third burner group 26c. The air flow path length Lae of the plurality of burners 27 constituting the fifth burner group 26e is the same as the air flow path length Lac of the plurality of burners 27 constituting the third burner group 26c. Therefore, the air flow path length Lae of the plurality of burners 27 constituting the fifth burner group 26e is shorter than the air flow path length Laa of the plurality of burners 27 constituting the first burner group 26a and the air flow path length Lab of the plurality of burners 27 constituting the second burner group 26b. The air flow path length Laf of the plurality of burners 27 constituting the sixth burner group 26f is the same as the air flow path length Lab of the plurality of burners 27 constituting the second burner group 26b and the air flow path length Lad of the plurality of burners 27 constituting the fourth burner group 26d. Therefore, the air flow path length Laf of the multiple burners 27 that make up the sixth burner group 26f is shorter than the air flow path length Laa of the multiple burners 27 that make up the first burner group 26a, and longer than the air flow path length Lac of the multiple burners 27 that make up the third burner group 26c.

[0035] Therefore, in the present embodiment, the air flow path length La differs between the burner groups 26 adjacent to each other in the circumferential direction Dcc (or between the circumferential divided regions 25). Furthermore, in the present embodiment, the positions of the air inlets 28i in the combustor axial direction Dc differ between the burner groups 26 adjacent to each other in the circumferential direction Dcc (or between the circumferential divided regions 25). Therefore, as shown in FIGS. 4 and 5 , the position of the upstream end face 23us of the air hole plate 23, on which the air inlets 28i of the air flow path frames 28 of the plurality of burners 27 constituting the second burner group 26b are formed, is shifted downstream Dcd with respect to the upstream end face 23us of the air hole plate 23, on which the air inlets 28i of the air flow path frames 28 of the plurality of burners 27 constituting the first burner group 26a are formed. The position of the upstream end face 23us of the air hole plate 23 on which the air inlets 28i of the air flow path frames 28 of the plurality of burners 27 constituting the third burner group 26c are formed is shifted downstream Dcd relative to the upstream end face 23us of the air hole plate 23 on which the air inlets 28i of the air flow path frames 28 of the plurality of burners 27 constituting the second burner group 26b are formed. The position of the upstream end face 23us of the air hole plate 23 on which the air inlets 28i of the air flow path frames 28 of the plurality of burners 27 constituting the fourth burner group 26d is formed is shifted upstream Dcu relative to the upstream end face 23us of the air hole plate 23 on which the air inlets 28i of the air flow path frames 28 of the plurality of burners 27 constituting the third burner group 26c are formed. The position of the upstream end face 23us of the air hole plate 23 on which the air inlets 28i of the air flow path frames 28 of the plurality of burners 27 constituting the fifth burner group 26e are formed is shifted downstream Dcd relative to the upstream end face 23us of the air hole plate 23 on which the air inlets 28i of the air flow path frames 28 of the plurality of burners 27 constituting the fourth burner group 26d are formed.The position of the upstream end face 23us of the air hole plate 23, on which the air inlets 28i of the air flow path frames 28 of the plurality of burners 27 constituting the sixth burner group 26f are formed, is shifted upstream Dcu relative to the upstream end face 23us of the air hole plate 23, on which the air inlets 28i of the air flow path frames 28 of the plurality of burners 27 constituting the fifth burner group 26e are formed, and is shifted downstream Dcd relative to the upstream end face 23us of the air hole plate 23, on which the air inlets 28i of the air flow path frames 28 of the plurality of burners 27 constituting the first burner group 26a are formed. Therefore, in this embodiment, there is a step in the combustor axial direction Dc between the upstream end face 23us of each of the plurality of burner groups 26 and the upstream end face 23us of the burner group 26 adjacent in the circumferential direction Dcc. In other words, in a region on the upstream end surface 23us where one of the two circumferentially divided regions 25 adjacent to each other in the circumferential direction Dcc transitions to the other circumferentially divided region 25, the position of the upstream end surface 23us in the combustor axial direction Dc changes in a stepwise manner.

[0036] The insertion length Li of the plurality of burners 27 constituting the first burner group 26a, the insertion length Li of the plurality of burners 27 constituting the second burner group 26b, the insertion length Li of the plurality of burners 27 constituting the third burner group 26c, the insertion length Li of the plurality of burners 27 constituting the fourth burner group 26d, the insertion length Li of the plurality of burners 27 constituting the fifth burner group 26e, and the insertion length Li of the plurality of burners 27 constituting the sixth burner group 26f are all the same.

[0037] Assume that the positions of the mixture outlets 28o of all the burners 27 in the combustor axial direction Dc are the same, and that the mixture flow path lengths Lm of all the burners 27 are the same. In this case, if any one of the following fluctuations occurs: concentration fluctuation of the mixture at the mixture outlet 28o, heat fluctuation due to combustion of the mixture injected from the burner 27 into the combustion liner 22, pressure fluctuation within the air flow path frame 28 of the burner 27, and velocity fluctuation of the mixture within the air flow path frame 28, these fluctuations will occur repeatedly. For example, if a concentration fluctuation occurs, this will cause the following sequence to occur repeatedly: heat fluctuation → pressure fluctuation → velocity fluctuation → concentration fluctuation. The cycle of these fluctuations may lock at a specific frequency, causing combustion oscillation that may damage the burner 27 or the combustion liner 22.

[0038] This combustion oscillation has a plurality of oscillation modes. A representative oscillation mode among the plurality of oscillation modes is, for example, an inner-outer oscillation mode in which an annular node Nc is formed around the combustor axis Ac inside the combustion liner 22, as shown in Fig. 6. In this inner-outer oscillation mode, the amplitude direction in a region on the inner circumferential side of the annular node N is opposite to the amplitude direction in a region on the outer circumferential side of the annular node N.

[0039] In the present embodiment, as described above, the mixture flow path length Lm differs between the burner groups 26 adjacent to each other in the circumferential direction Dcc (or between the circumferentially divided regions 25). Therefore, even if any one of the following fluctuations occurs: a concentration fluctuation of the mixture at the mixture outlet 28o, a heat fluctuation due to combustion of the mixture injected from the burner 27 into the combustion cylinder 22, a pressure fluctuation in the air flow path frame 28 of the burner 27, and a velocity fluctuation of the mixture in the air flow path frame 28, the frequency of the cycle of the aforementioned fluctuation differs between the burner groups 26 adjacent to each other in the circumferential direction Dcc (or between the circumferentially divided regions 25), and therefore, locking into combustion oscillation of a specific internal / external oscillation mode can be suppressed.

[0040] Furthermore, in the present embodiment, the positions of the upstream end faces 23us of each of the plurality of burner groups 26 in the combustor axial direction Dc are made different between the upstream end faces 23us of adjacent burner groups 26 in the circumferential direction Dcc, and the insertion lengths Li of the plurality of burners 27 of each of the plurality of burner groups 26 are made the same, thereby making the environment from the air inlet 28i to the fuel outlet 29o within the air flow path frame 28 of each of the plurality of burner groups 26 substantially the same. Therefore, it is easy to design the mixture flow path length Lm of each of the plurality of burner groups 26, which is effective in suppressing the occurrence of combustion oscillation.

[0041] Second Embodiment of Combustor As shown in FIG. 7 , an air hole plate 23 of a combustor in the present embodiment includes an inner region 24i including the combustor axis Ac, and an annular outer region 24o adjacent to the outer circumferential side of the inner region 24i. The outer region 24o includes a plurality of circumferential divided regions 25 that are aligned in the circumferential direction Dcc with respect to the combustor axis Ac. One of the plurality of burner groups 26 is provided in the inner region 24i. Note that hereinafter, the burner group 26 provided in the inner region 24i is referred to as an inner burner group 26i. Furthermore, one of the plurality of burner groups 26 is provided in each of the plurality of circumferential divided regions 25 of the outer region 24o. Note that hereinafter, the burner group 26 provided in each of the plurality of circumferential divided regions 25 of the outer region 24o is referred to as an outer burner group 26o.

[0042] In the present embodiment, as in the first embodiment, the number of the circumferentially divided regions 25 is six. The width angle of each of the circumferentially divided regions 25 in the circumferential direction Dcc relative to the combustor axis line Ac is the same among the circumferentially divided regions 25. In the present embodiment, among the circumferentially divided regions 25, the first circumferentially divided region 25a is a region ranging from 330° to 0° and 0° to 30° relative to the combustor axis line Ac. The second circumferentially divided region 25b is a region ranging from 30° to 90° relative to the combustor axis line Ac. The third circumferentially divided region 25c is a region ranging from 90° to 150° relative to the combustor axis line Ac. The fourth circumferentially divided region 25d is a region ranging from 150° to 210° relative to the combustor axis line Ac. The fifth circumferentially divided region 25e is a region ranging from 210° to 270° relative to the combustor axis line Ac. The sixth circumferentially divided region 25f is a region from 270° to 330° with respect to the combustor axis Ac.

[0043] In the present embodiment, all of the outer burner groups 26o provided in each of the plurality of circumferentially divided regions 25 of the outer region 24o are target burner groups. In the present embodiment as well, the outer burner groups 26o provided in each of the plurality of circumferentially divided regions 25 are aligned in the circumferential direction Dcc with respect to the combustor axis line Ac. Furthermore, the width angles of the plurality of outer burner groups 26o in the circumferential direction Dcc with respect to the combustor axis line Ac are the same among the plurality of outer burner groups 26o. In this embodiment, as in the first embodiment, the outer burner group 26o provided in the first circumferentially divided region 25a is referred to as the outer first burner group 26oa, the outer burner group 26o provided in the second circumferentially divided region 25b is referred to as the outer second burner group 26ob, the outer burner group 26o provided in the third circumferentially divided region 25c is referred to as the outer third burner group 26oc, the outer burner group 26o provided in the fourth circumferentially divided region 25d is referred to as the outer fourth burner group 26od, the outer burner group 26o provided in the fifth circumferentially divided region 25e is referred to as the outer fifth burner group 26oe, and the outer burner group 26o provided in the sixth circumferentially divided region 25f is referred to as the outer sixth burner group 26of.

[0044] Also in the present embodiment, as shown in Fig. 8 , the positions of the mixture outlets 28o of all of the air flow path frames 28 in the combustor axial direction Dc are the same. Therefore, the downstream end surface 23ds of the air hole plate 23 in which the mixture outlets 28o of each air flow path frame 28 are formed is flat. Note that Fig. 8 is a diagram illustrating a cross section taken along line VIIIa in the outer region 24o and a cross section taken along line VIIIb in the inner region 24i in Fig. 7 .

[0045] The air flow path length La, the mixture flow path length Lm, and the insertion length Li of the plurality of burners 27 constituting the first outer burner group 26oa, the plurality of burners 27 constituting the second outer burner group 26ob, the plurality of burners 27 constituting the third outer burner group 26oc, the plurality of burners 27 constituting the fourth outer burner group 26od, the plurality of burners 27 constituting the fifth outer burner group 26oe, and the plurality of burners 27 constituting the sixth outer burner group 26of are all the same as in the first embodiment.

[0046] That is, the gasoline mixture passage length Lma in the plurality of burners 27 constituting the first outer burner group 26oa is longer than the gasoline mixture passage length Lm in the plurality of burners 27 constituting the other outer burner groups 26o. The gasoline mixture passage length Lmb in the plurality of burners 27 constituting the second outer burner group 26ob, the gasoline mixture passage length Lmd in the plurality of burners 27 constituting the fourth outer burner group 26od, and the gasoline mixture passage length Lmf in the plurality of burners 27 constituting the sixth outer burner group 26of are all the same and shorter than the gasoline mixture passage length Lma in the plurality of burners 27 constituting the first outer burner group 26oa. The mixture gas passage length Lmc in the plurality of burners 27 constituting the third outer burner group 26oc and the mixture gas passage length Lme in the plurality of burners 27 constituting the fifth outer burner group 26oe are the same and are shorter than the mixture gas passage length Lmb in the plurality of burners 27 constituting the second outer burner group 26ob, the mixture gas passage length Lmd in the plurality of burners 27 constituting the fourth outer burner group 26od, and the mixture gas passage length Lmf in the plurality of burners 27 constituting the sixth outer burner group 26of. Thus, in this embodiment as well, the mixture gas passage length Lm differs between the outer burner groups 26o (or between the circumferential divided regions 25) adjacent to each other in the circumferential direction Dcc.

[0047] Furthermore, the air flow path length Laa of the plurality of burners 27 constituting the first outer burner group 26oa is longer than the air flow path length La of the plurality of burners 27 constituting the other outer burner group 26o. The air flow path length Lab of the plurality of burners 27 constituting the second outer burner group 26ob, the air flow path length Lad of the plurality of burners 27 constituting the fourth outer burner group 26od, and the air flow path length Laf of the plurality of burners 27 constituting the sixth outer burner group 26of are all the same and shorter than the air flow path length Laa of the plurality of burners 27 constituting the first outer burner group 26oa. The air flow path length Lac of the plurality of burners 27 constituting the outer third burner group 26oc and the air flow path length Lae of the plurality of burners 27 constituting the outer fifth burner group 26oe are the same as each other and are shorter than the air flow path length Lab of the plurality of burners 27 constituting the outer second burner group 26ob, the air flow path length Lad of the plurality of burners 27 constituting the outer fourth burner group 26od, and the air flow path length Laf of the plurality of burners 27 constituting the outer sixth burner group 26of.

[0048] Therefore, in this embodiment as well, the air flow path length La differs between the adjacent outer burner groups 26o (or between the adjacent circumferentially divided regions 25) in the circumferential direction Dcc. Furthermore, in this embodiment as well, the position of the air inlet 28i in the combustor axial direction Dc differs between the adjacent outer burner groups 26o (or between the adjacent circumferentially divided regions 25) in the circumferential direction Dcc. Therefore, as shown in FIG. 9 , in this embodiment as well, there is a step in the combustor axial direction Dc between the upstream end face 23us of each of the plurality of outer burner groups 26o and the upstream end face 23us of the adjacent outer burner group 26o in the circumferential direction Dcc. In other words, in a region of the upstream end face 23us where one of the two adjacent circumferentially divided regions 25 in the circumferential direction Dcc transitions to the other circumferentially divided region 25, the position of the upstream end face 23us in the combustor axial direction Dc changes stepwise.

[0049] The insertion length Li of the plurality of burners 27 constituting the outer first burner group 26oa, the insertion length Li of the plurality of burners 27 constituting the outer second burner group 26ob, the insertion length Li of the plurality of burners 27 constituting the outer third burner group 26oc, the insertion length Li of the plurality of burners 27 constituting the outer fourth burner group 26od, the insertion length Li of the plurality of burners 27 constituting the outer fifth burner group 26oe, and the insertion length Li of the plurality of burners 27 constituting the outer sixth burner group 26of are the same as each other.

[0050] The air flow path lengths Lai of the plurality of burners 27 constituting the inner burner group 26i are the same as one another and are shorter than the air flow path lengths La of the plurality of burners 27 constituting each of the plurality of outer burner groups 26o. The mixture flow path lengths Lmi of the plurality of burners 27 constituting the inner burner group 26i are the same as one another and are shorter than the mixture flow path lengths Lm of the plurality of burners 27 constituting each of the plurality of outer burner groups 26o. The insertion lengths Lii of the plurality of burners 27 constituting the inner burner group 26i are the same as one another.

[0051] As described above, in this embodiment as well, the mixture flow path length Lm differs between the outer burner groups 26o (or between the circumferentially divided regions 25) adjacent to each other in the circumferential direction Dcc. Therefore, in this embodiment as well, it is possible to suppress the occurrence of combustion oscillation in the above-mentioned internal / external oscillation mode that could lead to damage to the burners 27 or the combustion liner 22.

[0052] Among the multiple vibration modes of combustion oscillation, a representative vibration mode is, in addition to the aforementioned inner / outer vibration mode, a circumferential vibration mode in which, for example, as shown in FIG. 10 , multiple nodes Nr extending radially relative to the combustor axis Ac are formed within the combustion liner 22. In this circumferential vibration mode, the multiple nodes Nr divide the combustion liner 22 into multiple regions in the circumferential direction Dcc, and the amplitude directions of adjacent two regions in the circumferential direction Dcc are opposite to each other. In the present embodiment, as described above, the mixture flow path length Lm is different between the outer region 24o and the inner region 24i, thereby making it possible to suppress the occurrence of combustion oscillation in the circumferential vibration mode. Note that, even in the combustor 20 of the first embodiment, the occurrence of combustion oscillation in the circumferential vibration mode can be suppressed when the positions of the boundaries between the multiple burner groups 26 arranged in the circumferential direction Dcc are deviated from the positions of the nodes formed in the circumferential vibration mode.

[0053] In the present embodiment, the air flow path length Lai of the plurality of burners 27 constituting the inner burner group 26i is shorter than the air flow path length La of the plurality of burners 27 constituting each of the plurality of outer burner groups 26o. However, the air flow path length Lai of the plurality of burners 27 constituting the inner burner group 26i may be longer than the air flow path length La of the plurality of burners 27 constituting each of the plurality of outer burner groups 26o. In other words, it is sufficient that the air flow path length Lai of the plurality of burners 27 constituting the inner burner group 26i is different from the air flow path length La of the plurality of burners 27 constituting each of the plurality of outer burner groups 26o.

[0054] In the present embodiment, of the outer region 24o and the inner region 24i, only the outer region 24o has a plurality of circumferential divided regions 25 aligned in the circumferential direction Dcc. However, of the outer region 24o and the inner region 24i, only the inner region 24i may have a plurality of circumferential divided regions 25 aligned in the circumferential direction Dcc.

[0055] "Third Embodiment of Combustor" As shown in FIG. 11 , the air hole plate 23 of the combustor in the present embodiment includes an inner region 24i including the combustor axis Ac, and an annular outer region 24o adjacent to the outer circumferential side of the inner region 24i. The inner region 24i includes a plurality of inner circumferentially divided regions 25i that are arranged in the circumferential direction Dcc with respect to the combustor axis Ac. The outer region 24o includes a plurality of outer circumferentially divided regions 25o that are arranged in the circumferential direction Dcc with respect to the combustor axis Ac. One of the plurality of burner groups 26 is provided in each of the plurality of inner circumferentially divided regions 25i. Note that, hereinafter, the burner group 26 provided in each of the plurality of inner circumferentially divided regions 25i is referred to as an inner burner group 26i. One of the plurality of burner groups 26 is provided in each of the plurality of outer circumferentially divided regions 25o of the outer region 24o. In the following description, the burner groups 26 provided for each of the plurality of outer circumferentially divided regions 25o will be referred to as outer burner groups 26o.

[0056] In the present embodiment, as in the second embodiment, the number of the outer circumferentially divided regions 25o is six. The width angles of the outer circumferentially divided regions 25o in the circumferential direction Dcc relative to the combustor axis line Ac are the same among the outer circumferentially divided regions 25o. In the present embodiment, among the outer circumferentially divided regions 25o, the outer first circumferentially divided region 25oa is a region between 330° and 0° and between 0° and 30° relative to the combustor axis line Ac. The outer second circumferentially divided region 25ob is a region between 30° and 90° relative to the combustor axis line Ac. The outer third circumferentially divided region 25oc is a region between 90° and 150° relative to the combustor axis line Ac. The outer fourth circumferentially divided region 25od is a region between 150° and 210° relative to the combustor axis line Ac. The outer fifth circumferentially divided region 25oe is a region between 210° and 270° relative to the combustor axis line Ac. The outer sixth circumferentially divided region 25of is a region between 270° and 330° relative to the combustor axis line Ac. In the present embodiment, outer boundary lines 24oB, which are boundary lines between adjacent outer circumferentially divided regions 25o in the circumferential direction Dcc, are located at positions of 30°, 90°, 150°, 210°, 270°, and 330° relative to the combustor axis line Ac. Each of the outer boundary lines 24oB extends in the radial direction relative to the combustor axis line Ac within the outer region 24o.

[0057] In the present embodiment, all of the outer burner groups 26o provided in each of the plurality of outer circumferentially divided regions 25o are target burner groups. The outer burner groups 26o provided in each of the plurality of outer circumferentially divided regions 25o are aligned in the circumferential direction Dcc with respect to the combustor axis line Ac. Furthermore, the width angles of the plurality of outer burner groups 26o in the circumferential direction Dcc with respect to the combustor axis line Ac are the same among the plurality of outer burner groups 26o. In this embodiment, as in the second embodiment, the outer burner group 26o provided in the first outer circumferentially divided region 25oa is referred to as the first outer burner group 26oa, the outer burner group 26o provided in the second outer circumferentially divided region 25ob is referred to as the second outer burner group 26ob, the outer burner group 26o provided in the third outer circumferentially divided region 25oc is referred to as the third outer burner group 26oc, the outer burner group 26o provided in the fourth outer circumferentially divided region 25od is referred to as the fourth outer burner group 26od, the outer burner group 26o provided in the fifth outer circumferentially divided region 25oe is referred to as the fifth outer burner group 26oe, and the outer burner group 26o provided in the sixth outer circumferentially divided region 25of is referred to as the sixth outer burner group 26of.

[0058] In the present embodiment, the number of the inner circumferentially divided regions 25i is six. The width angles of the inner circumferentially divided regions 25i in the circumferential direction Dcc relative to the combustor axis line Ac are the same among the inner circumferentially divided regions 25i. In the present embodiment, among the inner circumferentially divided regions 25i, the inner first circumferentially divided region 25ia is a region ranging from 0° to 60° relative to the combustor axis line Ac. The inner second circumferentially divided region 25ib is a region ranging from 60° to 120° relative to the combustor axis line Ac. The inner third circumferentially divided region 25ic is a region ranging from 120° to 180° relative to the combustor axis line Ac. The inner fourth circumferentially divided region 25id is a region ranging from 180° to 240° relative to the combustor axis line Ac. The inner fifth circumferentially divided region 25ie is a region between 240° and 300° relative to the combustor axis line Ac. The inner sixth circumferentially divided region 25if is a region between 300° and 360° relative to the combustor axis line Ac. In the present embodiment, inner boundary lines 24iB, which are boundary lines between the inner circumferentially divided regions 25i adjacent to each other in the circumferential direction Dcc, are located at the positions of 0°, 60°, 120°, 180°, 240°, and 300° relative to the combustor axis line Ac. Each of the inner boundary lines 24iB extends in the radial direction relative to the combustor axis line Ac within the inner region 24i.

[0059] In this embodiment, the position of each inner boundary line 24iB in the circumferential direction Dcc is different from the position of each outer boundary line 24oB in the circumferential direction Dcc.

[0060] In the present embodiment, all of the inner burner groups 26 i provided in each of the plurality of inner circumferentially divided regions 25 i are target burner groups. The inner burner groups 26 i provided in each of the plurality of inner circumferentially divided regions 25 i are aligned in the circumferential direction Dcc with respect to the combustor axis line Ac. Furthermore, the width angles of the plurality of inner burner groups 26 i in the circumferential direction Dcc with respect to the combustor axis line Ac are the same among the plurality of inner burner groups 26 i. In the present embodiment, the inner burner group 26i provided in the first inner circumferential divided region 25ia is referred to as the first inner burner group 26ia, the inner burner group 26i provided in the second inner circumferential divided region 25ib is referred to as the second inner burner group 26ib, the inner burner group 26i provided in the third inner circumferential divided region 25ic is referred to as the third inner burner group 26ic, the inner burner group 26i provided in the fourth inner circumferential divided region 25id is referred to as the fourth inner burner group 26id, the inner burner group 26i provided in the fifth inner circumferential divided region 25ie is referred to as the fifth inner burner group 26ie, and the inner burner group 26i provided in the sixth inner circumferential divided region 25if is referred to as the sixth inner burner group 26if.

[0061] As shown in Fig. 12 , in this embodiment as well, the positions of the mixture outlets 28o of all of the air flow path frames 28 in the combustor axial direction Dc are the same. Therefore, the downstream end surface 23ds of the air hole plate 23 in which the mixture outlets 28o of each air flow path frame 28 are formed is flat. Note that Fig. 12 is a diagram illustrating a cross section taken along line XIIa in the outer region 24o and a cross section taken along line XIIb in the inner region 24i in Fig. 11 .

[0062] The air flow path length La, the mixture flow path length Lm, and the insertion length Li of the plurality of burners 27 constituting the first outer burner group 26oa, the plurality of burners 27 constituting the second outer burner group 26ob, the plurality of burners 27 constituting the third outer burner group 26oc, the plurality of burners 27 constituting the fourth outer burner group 26od, the plurality of burners 27 constituting the fifth outer burner group 26oe, and the plurality of burners 27 constituting the sixth outer burner group 26of are all the same as those in the second embodiment.

[0063] That is, the gasoline mixture passage length Lma in the plurality of burners 27 constituting the first outer burner group 26oa is longer than the gasoline mixture passage length Lm in the plurality of burners 27 constituting the other outer burner groups 26o. The gasoline mixture passage length Lmb in the plurality of burners 27 constituting the second outer burner group 26ob, the gasoline mixture passage length Lmd in the plurality of burners 27 constituting the fourth outer burner group 26od, and the gasoline mixture passage length Lmf in the plurality of burners 27 constituting the sixth outer burner group 26of are all the same and shorter than the gasoline mixture passage length Lmc in the plurality of burners 27 constituting the first outer burner group 26oa. The mixture gas passage length Lmc in the plurality of burners 27 constituting the third outer burner group 26oc and the mixture gas passage length Lme in the plurality of burners 27 constituting the fifth outer burner group 26oe are the same as each other and are shorter than the mixture gas passage length Lmc in the plurality of burners 27 constituting the second outer burner group 26ob, the mixture gas passage length Lmd in the plurality of burners 27 constituting the fourth outer burner group 26od, and the mixture gas passage length Lmf in the plurality of burners 27 constituting the sixth outer burner group 26of. Thus, in this embodiment as well, the mixture gas passage length Lm differs between the outer burner groups 26o (or between the circumferential divided regions 25) adjacent to each other in the circumferential direction Dcc.

[0064] Furthermore, the air flow path length Laa of the plurality of burners 27 constituting the first outer burner group 26oa is longer than the air flow path length La of the plurality of burners 27 constituting the other outer burner group 26o. The air flow path length Lab of the plurality of burners 27 constituting the second outer burner group 26ob, the air flow path length Lad of the plurality of burners 27 constituting the fourth outer burner group 26od, and the air flow path length Laf of the plurality of burners 27 constituting the sixth outer burner group 26of are all the same and shorter than the air flow path length Laa of the plurality of burners 27 constituting the first outer burner group 26oa. The air flow path length Lac of the plurality of burners 27 constituting the outer third burner group 26oc and the air flow path length Lae of the plurality of burners 27 constituting the outer fifth burner group 26oe are the same as each other and are shorter than the air flow path length Lab of the plurality of burners 27 constituting the outer second burner group 26ob, the air flow path length Lad of the plurality of burners 27 constituting the outer fourth burner group 26od, and the air flow path length Laf of the plurality of burners 27 constituting the outer sixth burner group 26of.

[0065] Therefore, also in the present embodiment, the air flow path lengths La are different between the outer burner groups 26o adjacent to each other in the circumferential direction Dcc (or between the outer circumferentially divided regions 25o). Also in the present embodiment, the positions of the air inlets 28i in the combustor axial direction Dc are different between the outer burner groups 26o adjacent to each other in the circumferential direction Dcc (or between the outer circumferentially divided regions 25o). Therefore, as shown in FIG. 13 , also in the present embodiment, there is a step in the combustor axial direction Dc between the upstream end surfaces 23us of each of the plurality of outer burner groups 26o and the upstream end surfaces 23us of the outer burner groups 26o adjacent to each other in the circumferential direction Dcc. In other words, in a region on the upstream end surface 23us where one of the two outer circumferential divided regions 25o adjacent to each other in the circumferential direction Dcc transitions to the other outer circumferential divided region 25o, the position of the upstream end surface 23us in the combustor axial direction Dc changes in a stepwise manner.

[0066] The insertion length Li of the plurality of burners 27 constituting the outer first burner group 26oa, the insertion length Li of the plurality of burners 27 constituting the outer second burner group 26ob, the insertion length Li of the plurality of burners 27 constituting the outer third burner group 26oc, the insertion length Li of the plurality of burners 27 constituting the outer fourth burner group 26od, the insertion length Li of the plurality of burners 27 constituting the outer fifth burner group 26oe, and the insertion length Li of the plurality of burners 27 constituting the outer sixth burner group 26of are the same as each other.

[0067] The air flow path length Laa of the plurality of burners 27 constituting the first inner burner group 26ia is longer than the air flow path length La of the plurality of burners 27 constituting the other inner burner group 26i. The air flow path length Lab of the plurality of burners 27 constituting the second inner burner group 26ib, the air flow path length Lad of the plurality of burners 27 constituting the fourth inner burner group 26id, and the air flow path length Laf of the plurality of burners 27 constituting the sixth inner burner group 26if are all the same and shorter than the air flow path length Laa of the plurality of burners 27 constituting the first inner burner group 26ia. The air flow path length Lac of the plurality of burners 27 constituting the inner third burner group 26ic and the air flow path length Lae of the plurality of burners 27 constituting the inner fifth burner group 26ie are the same as each other and are shorter than the air flow path length Lab of the plurality of burners 27 constituting the inner second burner group 26ib, the air flow path length Lad of the plurality of burners 27 constituting the inner fourth burner group 26id, and the air flow path length Laf of the plurality of burners 27 constituting the inner sixth burner group 26if.

[0068] Therefore, in the present embodiment, the air flow path length La is different between the inner burner groups 26i adjacent to each other in the circumferential direction Dcc (or between the inner circumferentially divided regions 25i). Furthermore, in the present embodiment, the position of the air inlet 28i in the combustor axial direction Dc is different between the inner burner groups 26i adjacent to each other in the circumferential direction Dcc (or between the inner circumferentially divided regions 25i). Therefore, as shown in FIG. 13 , in the present embodiment as well, there is a step in the combustor axial direction Dc between the upstream end surface 23us of each of the plurality of inner burner groups 26i and the upstream end surface 23us of the inner burner group 26i adjacent to each other in the circumferential direction Dcc. In other words, in a region on the upstream end surface 23us where one of the two inner circumferentially divided regions 25i adjacent to each other in the circumferential direction Dcc transitions to the other inner circumferentially divided region 25i, the position of the upstream end surface 23us in the combustor axial direction Dc changes in a stepwise manner.

[0069] The insertion length Li of the plurality of burners 27 constituting the first inner burner group 26ia, the insertion length Li of the plurality of burners 27 constituting the second inner burner group 26ib, the insertion length Li of the plurality of burners 27 constituting the third inner burner group 26ic, the insertion length Li of the plurality of burners 27 constituting the fourth inner burner group 26id, the insertion length Li of the plurality of burners 27 constituting the fifth inner burner group 26ie, and the insertion length Li of the plurality of burners 27 constituting the sixth inner burner group 26if are all the same.

[0070] As described above, in the present embodiment, the mixture flow path length Lm is different between the outer burner groups 26o (or between the outer circumferentially divided regions 25o) adjacent to each other in the circumferential direction Dcc. Furthermore, in the present embodiment, the mixture flow path length Lm is different between the inner burner groups 26i (or between the inner circumferentially divided regions 25i) adjacent to each other in the circumferential direction Dcc. Therefore, in the present embodiment, the occurrence of combustion oscillation in the above-described inner / outer oscillation mode, which may lead to damage to the burners 27 or the combustion liner 22, can be suppressed in each of the outer region 24o and the inner region 24i.

[0071] Furthermore, in the present embodiment, as described above, the position of the circumferential direction Dcc of each inner boundary line 24iB is different from the position of the circumferential direction Dcc of each outer boundary line 24oB. In other words, in the present embodiment, the position of the circumferential direction Dcc of each of the inner circumferentially divided regions 25i is different from the position of the circumferential direction Dcc of each of the outer circumferentially divided regions 25o. Therefore, the mixture flow path length Lm does not completely match between the outer region 24o and the inner region 24i, so that the occurrence of combustion oscillation in the circumferential oscillation mode can be suppressed.

[0072] "First Modification of Combustor" In the first embodiment, the number of the circumferentially divided regions 25 is six. However, as shown in FIG. 14 , the number of the circumferentially divided regions 25 may be three, or may be, for example, five, seven, or eight, as long as it is three or more. In the example shown in FIG. 14 , among the plurality of circumferentially divided regions 25, a first circumferentially divided region 25a is a region between 330° and 0° and between 0° and 90° relative to the combustor axis line Ac. A second circumferentially divided region 25b is a region between 90° and 210° relative to the combustor axis line Ac. A third circumferentially divided region 25c is a region between 210° and 330° relative to the combustor axis line Ac. Each of the plurality of circumferentially divided regions 25 is provided with one of the plurality of burner groups 26. 14 illustrates a modified example of the combustor according to the first embodiment, but the combustors according to the second and third embodiments may also have the number of the plurality of circumferentially divided regions as long as it is three or more, similar to this modified example. Furthermore, in the combustor according to the third embodiment, the number of the plurality of outer circumferentially divided regions 25o is the same as the number of the plurality of inner circumferentially divided regions 25i, but these numbers may be different from each other. For example, the number of the plurality of outer circumferentially divided regions 25o may be six, and the number of the plurality of inner circumferentially divided regions 25i may be three.

[0073] "Second Modification of Combustor" In the first embodiment, the upstream end surfaces 23us of each of the plurality of burner groups 26 are stepped in the combustor axial direction Dc between the upstream end surfaces 23us of adjacent burner groups 26 in the circumferential direction Dcc. However, as shown in FIG. 15 , all of the upstream end surfaces 23us of each of the plurality of burner groups 26 may be located on a single imaginary plane. In this case, the positions of the air inlets 28i of all of the burners 27 in the combustor axial direction Dc are the same, and the air flow path lengths La of all of the burners 27 are the same. Meanwhile, in this case, the insertion lengths Li of adjacent burner groups 26 in the circumferential direction Dcc are different from one another. Note that FIG. 15 illustrates a modification of the combustor in the first embodiment. However, in the combustors of the second and third embodiments, as in this modification, all of the upstream end surfaces 23us of each of the plurality of burner groups 26 may be located on a single imaginary plane.

[0074] Furthermore, the present disclosure is not limited to the embodiment and modifications described above, and various additions, modifications, substitutions, partial deletions, etc. are possible within the scope of the conceptual idea and spirit of the present invention derived from the content defined in the claims and their equivalents.

[0075] [Additional Notes] The combustors in the above-described embodiments and modifications can be understood, for example, as follows.

[0076] (1) A combustor according to a first aspect includes a cylinder 22 that is cylindrically shaped around a combustor axis Ac and that defines, on an inner circumferential side, a combustion space in which fuel can be combusted, and a plurality of burner groups 26. Each of the plurality of burner groups 26 includes a plurality of burners 27 that can inject fuel together with compressed air into the cylinder 22. Each of the plurality of burners 27 includes an air flow path frame 28 through which air can flow and that can inject the air into the cylinder 22, and a nozzle 29 that has a fuel ejection port 29o formed in the air flow path frame 28 and that can inject fuel. The air flow path frame 28 has an upstream side Dcu and a downstream side Dcd in a combustor axial direction Dc in which the combustor axis Ac extends, and includes an air inlet 28i that opens at an end of the upstream side Dcu of the air flow path frame 28, and an air-fuel mixture outlet 28o that opens at an end of the downstream side Dcd of the air flow path frame 28. A plurality of target burner groups 26, which are at least some of the plurality of burner groups 26, are aligned in a circumferential direction Dcc with respect to the combustor axis Ac. A mixture flow path length Lm, which is a distance in the combustor axial direction Dc from the fuel ejection port 29o of the nozzle 29 to the mixture outlet 28o of the air flow path frame 28 from which fuel is ejected from the fuel ejection port 29o, is different between target burner groups 26 adjacent to each other in the circumferential direction Dcc.

[0077] When any one of the following fluctuations occurs: concentration fluctuation of the air-fuel mixture at the air-fuel mixture outlet 28o, heat generation fluctuation due to combustion of the air-fuel mixture injected from the burner 27 into the combustion tube 22, pressure fluctuation in the air passage frame 28, and velocity fluctuation of the air-fuel mixture in the air passage frame 28, these fluctuations occur repeatedly. For example, when a concentration fluctuation occurs, it causes a heat generation fluctuation → pressure fluctuation → velocity fluctuation → concentration fluctuation to occur repeatedly in this order. If the positions of the air-fuel mixture outlets 28o of all the burners 27 in the combustor axial direction Dc are the same and all the burners 27 have the same mixture passage length Lm, the cycle of these fluctuations may lock at a specific frequency, causing combustion oscillation that may damage the burners 27 or the tube 22.

[0078] This combustion oscillation has a plurality of oscillation modes. A representative oscillation mode among the plurality of oscillation modes is, for example, an inner-outer oscillation mode in which an annular node Nc centered on the combustor axis Ac is formed inside the cylinder 22. In this inner-outer oscillation mode, the amplitude direction in a region on the inner circumferential side of the annular node Nc is opposite to the amplitude direction in a region on the outer circumferential side of the annular node Nc.

[0079] In this embodiment, the mixture flow path length Lm is different between adjacent burner groups 26 in the circumferential direction Dcc. Therefore, even if any one of fluctuations among fluctuations in the concentration of the mixture at the mixture outlet 28o, fluctuations in heat generation due to combustion of the mixture injected from the burner 27 into the cylinder 22, fluctuations in pressure within the air flow path frame 28, and fluctuations in the velocity of the mixture within the air flow path frame 28 occurs, the cycle frequencies of the aforementioned fluctuations are different between adjacent burner groups 26 in the circumferential direction Dcc, and therefore it is possible to prevent the combustion oscillation from being locked into a specific internal / external oscillation mode.

[0080] (2) A combustor according to a second aspect is the combustor 20 according to the first aspect, wherein the number of the plurality of target burner groups 26 is three or more.

[0081] (3) A combustor according to a third aspect is the combustor 20 according to the first or second aspect, wherein the width angles of the plurality of target burner groups 26 in the circumferential direction Dcc based on the combustor axis Ac are the same among the plurality of target burner groups 26.

[0082] (4) A combustor according to a fourth aspect is the combustor 20 according to any one of the first to third aspects, wherein the positions of the air inlets 28 i in the combustor axial direction Dc are different between target burner groups 26 adjacent to each other in the circumferential direction Dcc.

[0083] (5) A combustor according to a fifth aspect is the combustor 20 according to any one of the first to fourth aspects, wherein the distances in the combustor axial direction Dc from the air inlets 28i of the air flow path frame 28 to the fuel ejection ports 29o of the nozzles 29 that eject fuel into the air flow path frame 28 are the same among the plurality of target burner groups 26.

[0084] (6) A combustor according to a sixth aspect is the combustor 20 according to any one of the first to fifth aspects, wherein the positions of the air-fuel mixture outlets 28o of all of the air flow path frames 28 in the combustor axial direction Dc are the same as each other.

[0085] (7) A combustor according to a seventh aspect is the combustor 20 according to any one of the first to sixth aspects, wherein the plurality of burner groups 26 include an inner region 24i including the combustor axis Ac and an annular outer region 24o adjacent to the outer periphery of the inner region 24i, the plurality of target burner groups 26 being arranged in one region and the plurality of burner groups 26 being arranged in the other region, and the mixture flow path length Lm is different between the plurality of target burner groups 26 arranged in the one region and the burner group 26 arranged in the other region.

[0086] In this embodiment, a plurality of target burners 27 are arranged in one of the inner region 24i and the outer region 24o, and the mixed gas flow path lengths are different between the target burner groups 26 adjacent to each other in the circumferential direction Dcc. Therefore, in this embodiment as well, it is possible to suppress the occurrence of combustion oscillation in the above-mentioned internal and external oscillation mode that could lead to damage to the burners 27 and the cylinder 22.

[0087] Among the multiple vibration modes of combustion oscillation, a representative vibration mode is, in addition to the aforementioned inner and outer vibration mode, a circumferential vibration mode in which multiple nodes Nr extending in the radial direction relative to the combustor axis Ac are formed within the cylinder 22. In this circumferential vibration mode, the interior of the cylinder 22 is divided into multiple regions in the circumferential direction Dcc relative to the combustor axis Ac by the multiple nodes Nr, and the amplitude directions of two adjacent regions in the circumferential direction Dcc are opposite to each other. In this aspect, the mixture flow path length Lm is different between the multiple target burner groups 26 arranged in one of the inner region 24i and the outer region 24o and the burner group 26 arranged in the other region. Therefore, in this aspect, the occurrence of combustion oscillation in the circumferential vibration mode can also be suppressed.

[0088] (8) A combustor according to an eighth aspect is the combustor 20 according to any one of the first to sixth aspects, wherein the plurality of burner groups 26 includes a plurality of outer burner groups 26o as the plurality of target burner groups 26 disposed in an annular outer region 24o adjacent to an outer circumferential side of an inner region 24i including the combustor axis Ac, and a plurality of inner burner groups 26i disposed in the inner region 24i. The plurality of inner burner groups 26i are aligned in the circumferential direction Dcc with respect to the combustor axis Ac. The mixture flow path lengths Lm are different between the inner burner groups 26i adjacent to each other in the circumferential direction Dcc.

[0089] In this embodiment, the mixture flow path lengths Lm are different between the outer burner groups 26o adjacent to each other in the circumferential direction Dcc. Furthermore, in this embodiment, the mixture flow path lengths Lm are different between the inner burner groups 26i adjacent to each other in the circumferential direction Dcc. Therefore, in this embodiment, the occurrence of combustion oscillation in the above-mentioned internal / external oscillation mode, which may lead to damage to the burners 27 or the cylinders 22, can be suppressed in each of the outer region 24o and the inner region 24i.

[0090] (9) A combustor according to a ninth aspect relates to the combustor 20 according to the eighth aspect, wherein the outer region 24o includes outer circumferentially divided regions 25o each corresponding to one of the plurality of outer burner groups 26o, and outer boundary lines 24oB each corresponding to one of the plurality of outer burner groups 26o, which are arranged in the circumferential direction Dcc. The outer boundary lines 24oB each corresponding to one of the plurality of outer burner groups 26o extend in a direction having a radial component with respect to the combustor axis Ac and are boundary lines between the outer circumferentially divided regions 25o adjacent to each other in the circumferential direction Dcc. The inner region 24i includes inner circumferentially divided regions 25i each corresponding to one of the plurality of inner burner groups 26i, and inner boundary lines 24iB each corresponding to one of the plurality of outer burner groups 26o, which are arranged in the circumferential direction Dcc. The inner boundary line 24iB of each of the plurality of inner burner groups 26i extends in a direction having a radial component with respect to the combustor axis Ac and is a boundary line between the inner circumferentially divided regions 25i that are adjacent to each other in the circumferential direction Dcc. The position of the inner boundary line 24iB of each of the plurality of inner burner groups 26i in the circumferential direction Dcc is different from the position of the outer boundary line 24oB of each of the plurality of outer burner groups 26o in the circumferential direction Dcc.

[0091] In this embodiment, the position of each inner boundary line 24iB in the circumferential direction Dcc is different from the position of each outer boundary line 24oB in the circumferential direction Dcc. Therefore, the mixture flow path length Lm does not completely match between the outer region 24o and the inner region 24i, so that the occurrence of combustion oscillation in the circumferential oscillation mode can be suppressed.

[0092] (10) A tenth aspect of the combustor is the combustor 20 of any one of the first to ninth aspects, including an air hole plate 23 having a downstream end surface 23ds facing the downstream side Dcd and facing the combustion space, an upstream end surface 23us facing the upstream side Dcu, and a plurality of air holes 23h penetrating from the upstream end surface 23us to the downstream end surface 23ds. An inner circumferential surface of the air flow path frame 28 for each of the plurality of burners 27 is formed by an inner circumferential surface of any one of the plurality of air holes 23h. The air inlet 28i opens at the upstream end surface 23us of the air hole plate 23. The air-fuel mixture outlet 28o opens at the downstream end surface 23ds of the air hole plate 23. The air hole plate 23 has a plurality of circumferential divided regions 25 aligned in the circumferential direction Dcc with respect to the combustor axis Ac. One of the plurality of target burner groups 26 is provided for each of the plurality of circumferentially divided regions 25 .

[0093] For example, the air flow path frame 28 of each burner 27 can be formed of a pipe. In this case, it is necessary to manufacture a pipe for each of the plurality of burners 27 and arrange the pipes in appropriate positions for each of the plurality of burners 27. On the other hand, in this embodiment, the air flow path frame 28 for each of the plurality of burners 27 is integrated by the air hole plate 23, so that manufacturing costs can be reduced.

[0094] (11) An eleventh aspect of the combustor is that, in the combustor 20 of the tenth aspect, in a region in the upstream end surface 23us where one of two circumferentially divided regions 25 adjacent to each other in the circumferential direction Dcc transitions from the other circumferentially divided region 25, a position of the upstream end surface 23us in the combustor axial direction Dc changes in a stepwise manner.

[0095] The gas turbines in the above embodiments and modified examples can be understood as follows, for example. (12) A gas turbine in a twelfth aspect includes the combustor 20 in any one of the first to eleventh aspects, a compressor 10 capable of compressing air to generate compressed air, and a turbine 15 capable of being driven by combustion gas generated by combustion of fuel in the combustion space. The air flow path frame 28 for each of the plurality of burner groups 26 in the combustor 20 is configured to allow the compressed air from the compressor 10 to flow into the air flow path frame 28 from the air inlet 28i.

[0096] According to one aspect of the present disclosure, it is possible to flexibly respond to fluctuations in externally required output.

[0097] 1: Gas turbine 2: Gas turbine rotor 3: Intermediate casing 10: Compressor 11: Compressor rotor 12: Compressor casing 15: Turbine 16: Turbine rotor 17: Turbine casing 20: Combustor 21i: Inner cylinder 21o: Outer cylinder 21e: End cover 22: Combustion cylinder (or simply cylinder) 23;Air hole plate 23us: Upstream end face 23ds: Downstream end face 23h: Air hole 24i: Inner area 24iB: Inner boundary line 24o: Outer area 24oB: Outer boundary line 25: Circumferential division area 25a: First circumferential division area 25b: Second circumferential division area 25c: Third circumferential division area 25d: Fourth circumferential division area 25e: Fifth circumferential divided area 25f: Sixth circumferential divided area 25i: Inner circumferential divided area 25ia: Inner first circumferential divided area 25ib: Inner second circumferential divided area 25ic: Inner third circumferential divided area 25id: Inner fourth circumferential divided area 25ie: Inner fifth circumferential divided area 25if: Inner sixth circumferential divided area 25o: Outer circumferential divided area 25oa: Outer first circumferential division area 25ob: Second outer circumferential divided area 25oc: Third outer circumferential divided area 25od: Fourth outer circumferential divided area 25oe: Fifth outer circumferential divided area 25of: Sixth outer circumferential divided area 26: Burner group 26a: First burner group 26b: Second burner group 26c: Third burner group 26d: Fourth burner group 26e: Fifth burner group 26f: Sixth burner group 26i: Inside burner group 26ia: Inside first burner group 26ib: Inside second burner group 26ic: Inside third burner group 26id: Inside fourth burner group 26ie: Inside fifth burner group 26if: Inside sixth burner group 26o: Outside burner group 26oa: First outer burner group 26ob: Second outer burner group 26oc: Third outer burner group 26od: fourth outer burner group 26oe: fifth outer burner group 26of: sixth outer burner group 27: burner 28: air flow path frame 28i: air inlet 28o: mixture outlet 29: nozzle 29o: fuel nozzle 30: fuel supply system 31: main fuel line 32: branch fuel line A: air Acom: compressed air F: fuel CG: combustion gas Nc, Nr: nodes Ar: rotor axis Ac: combustor axis Da: rotor axial direction Dau: axial upstream side Dad: axial downstream side Dc: combustor axial direction Dcu: upstream side Dcd: downstream side Dcc: circumferential direction La: air flow path length Lm: mixture flow path length Li: insertion length;

Claims

1. A method for producing a combustion system comprising: a cylinder having a cylindrical shape around a combustor axis and defining a combustion space on an inner peripheral side in which fuel can be combusted; and a plurality of burner groups, each of the plurality of burner groups having a plurality of burners capable of injecting fuel together with compressed air into the cylinder, each of the plurality of burners having an air flow path frame through which air can flow and capable of injecting air into the cylinder, and a nozzle having a fuel ejection port formed in the air flow path frame and capable of injecting fuel, the air flow path frame having an air inlet opening at an upstream end of the air flow path frame and a mixture outlet opening at a downstream end of the air flow path frame, of the upstream and downstream sides in the combustor axial direction in which the combustor axis extends, and a plurality of target burner groups which are at least a portion of the plurality of burner groups are aligned in a circumferential direction about the combustor axis, a mixture flow passage length, which is a distance in the combustor axial direction from the fuel ejection port of the nozzle to the mixture outlet of the air flow passage frame through which fuel is ejected from the fuel ejection port, is different between target burner groups adjacent to each other in the circumferential direction.

2. A combustor according to claim 1, wherein the number of the plurality of target burner groups is three or more.

3. A combustor according to claim 1, wherein the circumferential width angle based on the combustor axis for each of the plurality of target burner groups is the same between the plurality of target burner groups.

4. A combustor according to claim 1, wherein the positions of the air inlets in the axial direction of the combustor are different between groups of target burners adjacent to each other in the circumferential direction.

5. A combustor according to claim 1, wherein the distance in the combustor axial direction from the air inlet of the air flow path frame to the fuel outlet of the nozzle that ejects fuel into the air flow path frame is the same for each of the plurality of target burner groups.

6. A combustor according to claim 1, wherein the positions of the mixture outlets of all the air flow path frames in the axial direction of the combustor are the same.

7. A combustor as claimed in claim 1, wherein the plurality of burner groups have the plurality of target burner groups arranged in one of an inner region including the combustor axis and an annular outer region adjacent to the outer periphery of the inner region, and a burner group arranged in the other region, and the mixture gas flow path length is different between the plurality of target burner groups arranged in the one region and the burner group arranged in the other region.

8. A combustor according to claim 1, wherein the plurality of burner groups include a plurality of outer burner groups which are the plurality of target burner groups arranged in an annular outer region adjacent to the outer circumferential side of an inner region including the combustor axis, and a plurality of inner burner groups arranged in the inner region, the plurality of inner burner groups being aligned in the circumferential direction with respect to the combustor axis, and the mixture gas flow path lengths being different between the inner burner groups adjacent to each other in the circumferential direction.

9. A combustor according to claim 8, wherein the outer region has outer circumferentially divided regions for each of the plurality of outer burner groups, and outer boundary lines for each of the plurality of outer burner groups, which are arranged in the circumferential direction, the outer boundary lines for each of the plurality of outer burner groups extending in a direction having a radial component with respect to the combustor axis and being boundary lines between the outer circumferentially divided regions adjacent in the circumferential direction, the inner region has inner circumferentially divided regions for each of the plurality of inner burner groups, and inner boundary lines for each of the plurality of outer burner groups, which are arranged in the circumferential direction, the inner boundary lines for each of the plurality of inner burner groups extending in a direction having a radial component with respect to the combustor axis and being boundary lines between the inner circumferentially divided regions adjacent in the circumferential direction, and the circumferential position of the inner boundary line for each of the plurality of inner burner groups is different from the circumferential position of the outer boundary line for each of the plurality of outer burner groups.

10. A combustor according to any one of claims 1 to 9, comprising an air hole plate having a downstream end face facing the downstream side and facing the combustion space, an upstream end face facing the upstream side, and a plurality of air holes penetrating from the upstream end face to the downstream end face, wherein an inner circumferential surface of the air flow path frame for each of the plurality of burners is formed by the inner circumferential surface of any one of the plurality of air holes, the air inlet opens at the upstream end face of the air hole plate, and the mixture outlet opens at the downstream end face of the air hole plate, the air hole plate has a plurality of circumferentially divided areas aligned in the circumferential direction relative to the combustor axis, and one of the plurality of target burner groups is provided for each of the plurality of circumferentially divided areas.

11. A combustor according to claim 10, wherein in a region of the upstream end face where one of the two circumferentially divided regions adjacent to each other in the circumferential direction transitions to the other circumferentially divided region, a position of the upstream end face in the combustor axial direction changes stepwise.

12. A gas turbine comprising: a combustor as claimed in claim 1; a compressor capable of compressing air to generate compressed air; and a turbine capable of being driven by combustion gas generated by combustion of fuel in the combustion space, wherein the air flow path frame for each of the plurality of burner groups in the combustor is configured to allow the compressed air from the compressor to flow into the air flow path frame from the air inlet.

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