Combustor and gas turbine

Abstract

This combustor comprises a central burner and an outer burner. The outer burner includes: an inner peripheral burner provided so as to surround an outer axis located on the radial outer-side of a demarcated combustor axis; and an outer peripheral burner provided so as to surround the demarcated inner peripheral burner. The amount of fuel supplied to demarcated fuel nozzles can be independently adjusted for the demarcated inner peripheral burner and the demarcated outer peripheral burner. A hole-free region where demarcated air holes of the outer peripheral burner are not formed is provided between the inner peripheral burner and the demarcated central burner on the downstream end face.

Description

Combustors and Gas Turbines

[0001] This application claims priority to Japanese Patent Application No. 2023-098806, filed on June 15, 2023, the contents of which are incorporated herein by reference.

[0002] For example, Patent Document 1 discloses a multi-cluster combustor as an example of a combustor used in a gas turbine. The multi-cluster combustor includes an air hole plate having a plurality of air holes formed therein and a fuel nozzle for supplying fuel to each of the air holes. A central burner is formed by air holes arranged in a group at the center of the air hole plate. An outer burner is formed by air holes arranged in a group at the outer periphery of the air hole plate. A plurality of outer burners are arranged in the circumferential direction to surround the central burner. The outer burner is composed of an inner burner and an outer burner, each of which has an independent fuel supply system.

[0003] JP 2013-155626 A

[0004] In the combustor described above, it is desired to achieve further reduction in NOx emissions while enabling stable operation with suppressed combustion oscillation.

[0005] The present disclosure has been made to solve the above-mentioned problems, and has an object to provide a combustor and a gas turbine that can achieve low NOx emissions while performing stable operation.

[0006] In order to achieve the above object, a combustor according to the present disclosure includes: an air hole plate having a plurality of air holes extending in a combustor axis direction and opening at a downstream end face; and a plurality of fuel nozzles provided corresponding to each of the air holes, the plurality of fuel nozzles supplying fuel from an upstream side to the corresponding air hole, wherein a central burner is formed by the plurality of air holes and the plurality of fuel nozzles collectively arranged to surround the combustor axis, and an outer burner is formed by the plurality of air holes and the plurality of fuel nozzles collectively arranged radially outside the central burner, the outer burner includes an inner burner provided to surround an outer axis located radially outside the combustor axis, and an outer burner provided to surround the inner burner, and amounts of fuel supplied to the fuel nozzles of the inner burner and the outer burner are adjustable independently of each other, and a hole-free region in which no air holes of the outer burner are formed is provided between the inner burner and the central burner at the downstream end face.

[0007] A gas turbine according to the present disclosure includes the above-described combustor, a compressor that compresses air and supplies it to the combustor, a turbine that is driven by combustion gas produced by the combustor, and a fuel control device that controls the amount of fuel supplied to the fuel nozzles of the combustor, wherein the fuel control device sets the amount of fuel supplied so that, at rated load, the fuel-air ratio of the central burner is greater than the fuel-air ratio of the outer peripheral burner, and so that the fuel-air ratio of the inner peripheral burner is greater than the fuel-air ratio of the outer peripheral burner.

[0008] According to the combustor and gas turbine according to the present disclosure, it is possible to achieve low NOx emissions while maintaining stable operation.

[0009] Fig. 3 is a schematic diagram showing a schematic configuration of a gas turbine according to a first embodiment of the present disclosure. Fig. 4 is a longitudinal sectional view showing a schematic configuration of a combustor according to the first embodiment of the present disclosure. Fig. 5 is a diagram of the combustor according to the first embodiment of the present disclosure, as viewed from the downstream side. Fig. 6 is an enlarged view of a main part of Fig. 3. Fig. 7 is a functional block diagram of a fuel control device for a gas turbine according to the first embodiment of the present disclosure. Fig. 8 is a flowchart illustrating a processing flow of the fuel control device in the gas turbine according to the first embodiment of the present disclosure. Fig. 9 is an enlarged view of a main part of a combustor according to a second embodiment of the present disclosure, as viewed from the downstream side. Fig. 10 is a hardware configuration diagram of a fuel control device for a gas turbine according to the present disclosure.

[0010] <First Embodiment> A first embodiment of the present invention will be described in detail below with reference to Figures 1 to 6. As shown in Figure 1, a gas turbine 1 according to this embodiment includes a compressor 2 that compresses air, a combustor 3 that generates combustion gas, a turbine 4 driven by the combustion gas, and a fuel control device 90 that controls the amount of fuel supplied to the combustor 3. A plurality of combustors 3 are provided around the rotation shaft of the gas turbine 1 at intervals in the circumferential direction. The combustors 3 mix fuel with the air compressed by the compressor 2 and combust the fuel to generate high-temperature, high-pressure combustion gas.

[0011] <Combustor> The configuration of the combustor 3 will be described below with reference to Figures 2 to 4. As shown in Figure 2, the combustor 3 includes an outer casing 10, an end cover 20, an inner casing 30, an air hole plate 40, a fuel nozzle 60, and a fuel supply system 80.

[0012] <Outer casing> The outer casing 10 has a cylindrical shape centered on a combustor axis O (hereinafter simply referred to as the axis O) which is the center of the combustor 3. Combustion gas is generated in the space inside the outer casing 10. The combustion gas flows from one side in the direction of the axis O (the left side in FIG. 2 ), which is the upstream side, to the other side in the direction of the axis O (the right side in FIG. 2 ), which is the downstream side.

[0013] <End Cover> The end cover 20 is a disk-shaped member that closes the upstream end of the external cylinder 10. The upstream end of the external cylinder 10 abuts against the end cover 20. A first fuel header 21, a second fuel header 22, and a third fuel header 23 are formed as spaces inside the end cover 20. Fuel is supplied to the first fuel header 21, the second fuel header 22, and the third fuel header 23 from the outside.

[0014] The first fuel header 21 is a space formed along the axis O. The second fuel header 22 is a space formed along an outer axis P spaced from the axis O radially outward of the axis O. As shown in FIG. 2 , a plurality of outer axes P (six in this embodiment) are arranged spaced apart in the circumferential direction of the axis O. The third fuel header 23 is a space formed to surround each second fuel header 22 from the radially outer side of the outer axis P. The third fuel header 23 has an annular shape formed concentrically with the second fuel header 22.

[0015] <Inner cylinder> The inner cylinder 30 is a cylindrical member centered on the axis O, and is disposed inside the outer cylinder 10 coaxially with the outer cylinder 10. The upstream end of the inner cylinder 30 is spaced apart from the end cover 20 in the direction of the axis O. The outer diameter of the inner cylinder 30 is smaller than the outer diameter of the inner cylinder 30. The inner cylinder 30 is provided inside the outer cylinder 10 and spaced apart from the end cover 20 by a support portion (not shown). As a result, an annular flow path is formed between the outer peripheral surface of the inner cylinder 30 and the inner peripheral surface of the outer cylinder 10. Air compressed by the compressor 2 flows through this flow path from the other side in the direction of the axis O to one side in the direction of the axis O.

[0016] <Air hole plate> The air hole plate 40 is disk-shaped with its center at the axis O. The air hole plate 40 is fitted inside the inner cylinder 30 so as to be coaxial with the inner cylinder 30. The air hole plate 40 is fitted into the upstream end of the inner cylinder 30. The air hole plate 40 has an upstream end face 41 and a downstream end face 42.

[0017] <Upstream End Surface> The upstream end surface 41 is the upstream end surface of the air hole plate 40 and has a flat surface perpendicular to the axis O. The upstream end surface 41 is located at the same position in the axis O as the upstream end surface of the inner cylinder 30.

[0018] <Downstream End Surface> The downstream end surface 42 is the downstream end surface of the air hole plate 40 and is flat and perpendicular to the axis O. The downstream end surface 42 is located downstream of the upstream end surface of the inner cylinder 30. As a result, a space is defined by the inner circumferential surface of the inner cylinder 30 and the downstream end surface 42 of the air hole plate 40. This space serves as a combustion space of the combustor 3.

[0019] <Air holes> A plurality of air holes 50 are formed in the air hole plate 40, penetrating from the upstream end face 41 to the downstream end face 42. The air hole plate 40 extends in the direction of the axis O. The air holes 50 are open at both the upstream end face 41 and the downstream end face 42. Air flows in through the opening at the upstream end face 41 of each air hole 50, and flows out through the opening at the downstream end face 42 of each air hole 50.

[0020] 3, the air holes 50 are arranged in groups to form air hole groups, which include a central air hole group 51 and an outer air hole group 52.

[0021] <Central Air Hole Group> The central air hole group 51 is formed in the center of the air hole plate 40 when viewed in the direction of the axis O. That is, the central air hole group 51 is formed by air holes 50 that are collectively arranged in a circular area centered on the axis O so as to surround the axis O of the air hole plate 40. The central air hole group 51 is configured by multiple rows (three rows in this embodiment) of air holes 50 arranged in a ring shape centered on the axis O, arranged in the radial direction.

[0022] The air holes 50 constituting the central air hole group 51 extend so as to spiral in the circumferential direction of the axis O as they move from the upstream side to the downstream side. In other words, these air holes 50 are configured to have a spiral angle with respect to the axis O.

[0023] <Outer air hole groups> A plurality of outer air hole groups 52 are formed at intervals in the circumferential direction of the axis O of the air hole plate 40 so as to surround the central portion when viewed in the direction of the axis O. The outer air hole groups 52 are formed radially outward from the axis O at the central portion and radially inward from the outer peripheral edge of the air hole plate 40. The outer air hole groups 52 are formed by air holes 50 that are collectively arranged in a circular region centered on the outer axis P so as to surround the outer axis P. The outer air hole groups 52 are made up of an inner peripheral air hole group 53 and an outer peripheral air hole group 54.

[0024] The inner circumferential air hole group 53 is formed by a row of holes arranged in an annular shape around the outer axis P so as to surround the outer axis P. In this embodiment, the inner circumferential air hole group 53 is formed by a single annular row of holes.

[0025] The outer peripheral air hole group 54 is provided so as to surround the inner peripheral air hole group 53 from the radially outer side of the outer axis P. The outer peripheral air hole group 54 has a hole row made up of a plurality of air holes 50 arranged in the circumferential direction of the outer axis P. The outer peripheral air hole group 54 in this embodiment is configured by arranging multiple rows of the hole rows in the radial direction (two rows in this embodiment).

[0026] The air holes 50 constituting the outer air hole group 52 extend so as to spiral in the circumferential direction of the outer axis P as they move from the upstream side to the downstream side. In other words, these air holes 50 are configured to have a spiral angle with respect to the outer axis P.

[0027] Here, the swirling direction of the air holes 50 that make up the outer air hole group 52 is opposite to the swirling direction of the air holes 50 that make up the central air hole group 51. In this embodiment, when viewed from the downstream side, the air holes 50 that make up the central air hole group 51 extend in a clockwise direction (first swirling direction) as they move downstream, whereas the air holes 50 that make up the outer air hole group 52 extend in a counterclockwise direction (second swirling direction) as they move downstream.

[0028] 2, a plurality of fuel nozzles 60 are provided in one-to-one correspondence with each air hole 50. The fuel nozzles 60 inject fuel into each air hole 50. The fuel supplied from the fuel nozzles 60 into the air hole 50 is mixed with the air flowing through the air hole 50 to generate a premixed gas.

[0029] Each fuel nozzle 60 has a cylindrical shape extending parallel to the axis O. A fuel injection hole for supplying fuel is formed at the downstream end, i.e., the tip, of each fuel nozzle 60. The tip of each fuel nozzle 60 is inserted into the corresponding air hole 50 from the opening in the upstream end face 41. The multiple fuel nozzles 60 are arranged spaced apart in a direction perpendicular to the axis O in accordance with the arrangement of the air holes 50.

[0030] The base ends of the fuel nozzles 60 opposite to the tips are fixed to the end cover 20. A fuel inlet is formed at the base end of the fuel nozzles 60. The fuel inlet of each fuel nozzle 60 communicates with one of the first fuel header 21, the second fuel header 22, and the third fuel header 23.

[0031] Here, the fuel nozzles 60 that supply fuel to the air holes 50 that make up the central air hole group 51 are referred to as central nozzles 61. The central nozzles 61 are arranged in groups to surround the axis O in correspondence with the central air hole group 51. The base ends of the central nozzles 61 are connected to the first fuel header 21. As a result, fuel is supplied to the central nozzles 61 via the first fuel header 21.

[0032] The fuel nozzles 60 that supply fuel to the air holes 50 that make up the outer air hole groups 52 are referred to as outer nozzles 62. The outer nozzles 62 are arranged in groups corresponding to the outer air hole groups 52 so as to surround the outer axis P. Each of the outer nozzles 62 includes a plurality of inner peripheral nozzles 63 and outer peripheral nozzles 64.

[0033] The inner nozzle 63 supplies fuel to the air holes 50 that constitute the inner air hole group 53 of the outer air hole group 52. The inner nozzle 63 is provided in a region of the outer air hole group 52 that is radially inward of the outer axis P, corresponding to the inner air hole group 53. A base end of the inner nozzle 63 is connected to the second fuel header 22. As a result, fuel is supplied to the inner nozzle 63 via the second fuel header 22.

[0034] The outer peripheral nozzle 64 supplies fuel to the air holes 50 that constitute the outer peripheral air hole group 54 of the outer air hole group 52. The outer peripheral nozzle 64 is provided in a region of the outer air hole group 52 that is radially outward of the outer axis P, corresponding to the outer peripheral air hole group 54. A base end of the outer peripheral nozzle 64 is connected to the third fuel header 23. As a result, fuel is supplied to the outer peripheral nozzle 64 via the third fuel header 23.

[0035] 1 , the fuel supply system 80 is a system that supplies fuel to each fuel nozzle 60 via the first fuel header 21, the second fuel header 22, and the third fuel header 23. In this embodiment, the amount of fuel supplied to each of the first fuel header 21, the second fuel header 22, and the third fuel header 23 can be adjusted independently. This makes it possible to individually adjust the amount of fuel supplied to each of the center nozzles 61 connected to the first fuel header 21, the inner peripheral nozzles 63 connected to the second fuel header 22, and the outer peripheral nozzles 64 connected to the third fuel header 23.

[0036] The fuel supply system 80 includes a first fuel line 81, a first fuel regulating valve 81a, a second fuel line 82, a second fuel regulating valve 82a, a third fuel line 83, and a third fuel regulating valve 83a. The first fuel line 81, the second fuel line 82, and the third fuel line 83 are each connected to a fuel tank. The fuel supplied from the fuel tank may be, for example, natural gas. However, hydrogen, a mixed fuel of hydrogen and natural gas, or other fuels may also be used.

[0037] The first fuel line 81 is connected to the first fuel header 21. A first fuel regulating valve 81a is provided in the first fuel line 81. The second fuel line 82 branches off midway and is connected to each second fuel header 22. A second fuel regulating valve 82a is provided in the second fuel line 82. The third fuel line 83 branches off midway and is connected to each third fuel header 23. A third fuel regulating valve 83a is provided in the third fuel line 83.

[0038] <Each burner and its details> A central burner 71 is made up of a central air hole group 51 and a plurality of central nozzles 61 that supply fuel to the air holes 50 that make up the central air hole group 51. The central burner 71 is made up of an outer air hole group 52 and a plurality of outer nozzles 62 that supply fuel to the air holes 50 that make up the outer air hole group 52.

[0039] The radially inner portion of the outer burner 72 with respect to the outer axis P is an inner peripheral burner 73 that surrounds the outer axis P. The radially outer portion of the outer burner 72 with respect to the outer axis P is an outer peripheral burner 74 that covers the inner peripheral burner 73 from the outer peripheral side of the outer axis P.

[0040] Each burner will be described in detail with reference to Figure 4. Because the air holes 50 constituting the central air hole group 51 of the central burner 71 have a swirl angle in the first swirl direction, the premixed gas from the central air hole group 51 is ejected radially outward from the axis O while swirling in the first swirl direction. When the premixed gas is ignited, a flame is formed having a central swirl flow F1 about the axis O. Because the air holes 50 constituting the outer air hole group 52 of the outer burner 72 have a swirl angle in a second swirl direction opposite to the first swirl direction, the premixed gas from the central air hole group 51 swirls in the second swirl direction opposite to the first swirl direction and is ejected radially outward from the outer axis P. When the premixed gas is ignited, a flame is formed having an outer swirl flow F2 about the outer axis P and opposite to the central swirl flow F1.

[0041] When the downstream end face 42 is viewed from the downstream side, there is an area between the central air hole group 51 that constitutes the central burner 71 and the inner air hole group 53 that constitutes the inner burner 73, where the air holes 50 of the outer air hole group 54 that constitutes the outer burner 74 are not formed. This area is designated as a hole-free area R. No air holes 50 open in the hole-free area R, and only the flat surface of the downstream end face 42 without any air holes 50 exists between the central air hole group 51 and the inner air hole group 53.

[0042] The outer-periphery air hole groups 54 are provided over only a portion of the circumferential direction of the outer axis P. That is, the outer-periphery air hole groups 54 exist only in the portion outside the no-hole region R between the central air hole groups 51 and the inner air hole groups 53. In other words, the outer-periphery air hole groups 54 exist only in the remaining region cut away in the circumferential direction by the no-hole region R.

[0043] In this embodiment, the row of holes extending in the circumferential direction at the innermost periphery of the outer-periphery air hole group 54 is present in a circumferential region excluding only the no-hole region R. Furthermore, the row of holes extending in the circumferential direction at the outermost periphery of the outer-periphery air hole group 54 is provided in a circumferential range that is narrower than the circumferential range of the row of holes at the innermost periphery. The row of holes at the outermost periphery may also be provided in the same circumferential range as the row of holes at the innermost periphery.

[0044] 4, when the downstream end face 42 is viewed from the downstream side, a straight line connecting the axis O and the outer axis P is defined as a reference line L. The reference line L is a straight line extending in the radial direction of the axis O and the outer axis P. The hole-free region R is centered on the outer axis P and extends over a predetermined range from the reference line L toward the upstream side of the outer swirling flow F2. In this embodiment, the hole-free region R is centered on the outer axis P and extends over a predetermined range from the reference line L toward the downstream side of the outer swirling flow F2.

[0045] 4 , when the downstream end face 42 is viewed from the downstream side, among the straight lines extending from the outer axis P in the radial direction of the outer axis P, a straight line that defines the upstream end of the outer swirling flow F2 in the hole-free region R is defined as the upstream boundary line U. Furthermore, when the downstream end face 42 is viewed from the downstream side, among the straight lines extending from the outer axis P in the radial direction of the outer axis P, a straight line that defines the downstream end of the outer swirling flow F2 in the hole-free region R is defined as the upstream boundary line U. The hole-free region R exists across the upstream boundary line U and the downstream boundary line D in the region around the outer axis P.

[0046] In this embodiment, the upstream boundary line U is located in a range from the reference line L to the upstream tangent line T1 within a circumferential region centered on the outer axis P. More specifically, the upstream boundary line U is located in a range upstream of the reference line L with respect to the outer swirling flow F2, up to the upstream tangent line T1. Here, the upstream tangent line T1 is one of two tangent lines drawn from the outer axis P to a circle defining the outer edge of the central burner 71, which is located upstream of the outer swirling flow F2 as viewed from the radially inner side of the axis O. The air holes 50 at one circumferential end of the outer peripheral air hole group 54 of the outer burner 74 contact the upstream tangent line T1 from the upstream side of the outer swirling flow F2. Furthermore, the circle defining the outer edge of the central burner 71 is a virtual circle centered on an axis on which the outermost row of air holes 50 of the central air hole group 51 of the central burner 71 is inscribed. It is not necessary for all of the air holes 50 in the row at the outermost periphery of the central air hole group 51 to be inscribed in the circle, and only some of the air holes 50 may be inscribed in the circle. In this embodiment, the upstream boundary line U coincides with the upstream tangent line T1.

[0047] In this embodiment, the downstream boundary line D is located in a range from the reference line L to the downstream tangent line T2 within a circumferential region centered on the outer axis P. More specifically, the downstream boundary line D is located in a range downstream of the reference line L of the outer swirling flow F2, up to the downstream tangent line T2. Here, the downstream tangent line T2 is one of two tangent lines drawn from the outer axis P to a circle defining the outer edge of the central burner 71, and is located downstream of the outer swirling flow F2 when viewed from the radially inner side of the axis O. The air holes 50 at the other circumferential end of the outer peripheral air hole group 54 of the outer peripheral burner 74 contact the downstream tangent line T2 from the downstream side of the outer swirling flow F2. In this embodiment, the downstream boundary line D is located closer to the downstream tangent line T2 within the region between the reference line L and the downstream tangent line T2.

[0048] Therefore, the hole-free region R in this embodiment is located in the region between the central burner 71 and the inner peripheral burner 73, biased toward the upstream side in the swirling direction of the outer swirling flow F2 with respect to the reference line L. That is, the region of the hole-free region R upstream of the reference line L of the outer swirling flow F2 is wider than the region downstream of the reference line L of the outer swirling flow F2.

[0049] The angle formed by the upstream boundary line U and the downstream boundary line D is set, for example, in the range of 30° to 90°, preferably in the range of 45° to 75°, and more preferably in the range of 55° to 65°.

[0050] <Fuel Control Device> Next, the fuel control device 90 will be described with reference to Figures 5 and 6. The fuel control device 90 controls the amount of fuel supplied to each burner. As shown in Figure 5, the fuel control device 90 includes an output requirement acquisition unit 91, a fuel distribution setting unit 92, and an adjustment valve control unit 93.

[0051] The output request acquisition unit 91 acquires an output request signal of the gas turbine 1. The fuel allocation setting unit 92 sets the apertures of the first fuel regulating valve 81 a, the second fuel regulating valve 82 a, and the third fuel regulating valve 83 a in accordance with the output request signal acquired by the output request acquisition unit 91. The adjustment valve control unit 93 controls the first fuel regulating valve 81 a, the second fuel regulating valve 82 a, and the third fuel regulating valve 83 a so that the apertures are set by the fuel allocation setting unit 92.

[0052] Next, the processing procedure of the fuel control device 90 will be described with reference to the flowchart shown in FIG. 5 . First, the output request acquisition unit 91 acquires an output request signal of the gas turbine 1 (step S1). Next, the fuel allocation setting unit 92 sets the apertures of the first fuel control valve 81a, the second fuel control valve 82a, and the third fuel control valve 83a in accordance with the deviation between the output request signal and the actual output of the gas turbine 1 so that the fuel-air ratio (a dimensionless number obtained by dividing the fuel mass by the air mass) of each fuel nozzle 60 becomes an appropriate value (step S2). Here, for example, when the output request of the gas turbine 1 is rated operation (full load operation), the fuel-air ratio of each fuel nozzle 60 is set so that the fuel-air ratio of the central nozzle 61 is higher than that of the inner nozzle 63, and so that the fuel-air ratio of the inner nozzle 63 is higher than that of the outer nozzle 64. The fuel allocation setting unit 92 sets the apertures of the first fuel control valve 81a, the second fuel control valve 82a, and the third fuel control valve 83a so that the fuel-air ratio becomes the appropriate value.

[0053] Then, the regulating valve control unit 93 controls the first fuel regulating valve 81a, the second fuel regulating valve 82a, and the third fuel regulating valve 83a based on the set opening degrees (step S3). As a result, fuel is supplied to the first fuel header 21, the second fuel header 22, and the third fuel header 23 so as to achieve a fuel-air ratio according to the output request of the gas turbine 1. This makes it possible to operate the gas turbine 1 according to the output request.

[0054] <Effects> In the combustor 3 when the gas turbine 1 is operating, the central burner 71, which has the highest fuel-air ratio during rated operation, plays a role in flame-stabilizing the outer peripheral burner 74. Furthermore, among the outer peripheral burners 74, the inner peripheral burner 73, which has a relatively high fuel-air ratio, stabilizes the flame of the outer peripheral burner 74, which has a relatively low fuel-air ratio. In this embodiment, as shown in Fig. 4, a hole-free region R is provided between the central burner 71 and the inner peripheral burner 73, where there are no air holes 50 that constitute the outer peripheral air hole group 54 of the outer peripheral burner 74. Therefore, the flame generated in the combustion space by the central burner 71 can be guided to the inner peripheral burner 73 via the hole-free region R.

[0055] If the air holes 50 of the outer-periphery burner 74 were present over the entire circumferential area of ​​the outer axis P, the entire area around the inner-periphery burner 73 would be covered by the flame from the outer-periphery burner 74 having the outer swirling flow F2. Therefore, the flame of the outer-periphery burner 74 would act as a barrier, making it difficult for the flame of the central burner 71 to reach the inner-periphery burner 73. In contrast, in this embodiment, the air holes 50 of the outer-periphery burner 74 are not present in the area between the central burner 71 and the inner-periphery burner 73, and therefore an area without the flame of the outer-periphery burner 74 is formed between the central burner 71 and the inner-periphery burner 73. Therefore, the flame of the central burner 71 can reach the inner-periphery burner 73 without being obstructed by the flame of the outer-periphery burner 74.

[0056] This improves the flame transfer from the central burner 71 to the inner burner 73. As a result, the flame of the central burner 71 can assist the combustion of the flame of the inner burner 73, improving the flame stability of the inner burner 73. Furthermore, the improved flame stability of the inner burner 73 also improves the combustibility of the outer burner 74, which is flame-stabilized by the inner burner 73. Therefore, the combustibility of the entire combustor 3 is improved, and stable operation with suppressed combustion oscillation is possible.

[0057] Here, because the flame transfer from the central burner 71 to the inner peripheral burner 73 has been improved, the inner peripheral burner 73 can stably maintain a flame even if the fuel supply amount to the inner peripheral burner 73 is reduced compared to before to lower the fuel-air ratio. Therefore, the temperature of the flame generated by the inner peripheral burner 73 can be lowered, and as a result, the generation of NOx can be suppressed.

[0058] Furthermore, by providing the hole-free region R and reducing the number of air holes 50 in the air hole groups constituting the outer burner 74, the air flow rate of the central air hole group 51 of the central burner 71 and the air flow rate of the inner air hole group 53 of the inner burner 73 increase accordingly. This makes it possible to lower the flame temperatures of the central burner 71 and the inner burner 73, which have high flame temperatures. As a result, it becomes possible to reduce the total amount of NOx generated by the entire combustor 3.

[0059] In this embodiment, the hole-free region R extends upstream of the outer swirling flow F2 from the reference line L. Therefore, the hole-free region R is configured to open in the tangential direction of the central swirling flow F1 of the central burner 71. This allows the flame of the central burner 71 to be smoothly guided to the inner burner 73 along the flow of the central swirling flow F1, thereby improving the flame stability of the inner burner 73.

[0060] Furthermore, in this embodiment, the upstream boundary line U of the hole-free region R coincides with the tangent to the circle that forms the outer edge of the central burner 71. This allows the flame guided by the flow of the central swirl flow F1 to be taken in to the inner peripheral burner 73 to the maximum extent possible, thereby further improving the flame stability of the inner peripheral burner 73.

[0061] Furthermore, since the hole-free region R extends beyond the reference line L to the downstream side of the outer swirling flow F2, the entrance of the flame of the central burner 71 to the inner burner 73 can be made large from the upstream side to the downstream side, thereby ensuring more reliable transfer of the flame from the central burner 71 to the inner burner 73.

[0062] Furthermore, the region of the hole-free region R upstream of the reference line L of the outer swirling flow F2 is wider than the region of the hole-free region R downstream of the reference line L of the outer swirling flow F2. This improves the flame transfer from the central burner 71 to the inner burner 73, while ensuring a large region for forming the outer burner 74 on the outer burner 72. As a result, the output of the combustor 3 can be ensured.

[0063] Second Embodiment Next, a combustor 3 according to a second embodiment will be described with reference to FIG. 7 . In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. The combustor 3 according to the second embodiment differs from the first embodiment in the range in which the hole-free region R is formed. That is, as shown in FIG. 7 , the downstream boundary line D of the hole-free region R according to the second embodiment is located downstream of the upstream boundary line U in the outer swirling flow F2 and upstream of the reference line L. The angle formed by the upstream boundary line U and the downstream boundary line D is set to a range of, for example, 15° to 45°, preferably 20° to 40°, and more preferably 25° to 35°.

[0064] As a result, the circumferential range of the hole-free region R is smaller than in the first embodiment. On the other hand, the range over which the peripheral air hole groups 54 constituting the peripheral burner 74 are formed is wider than in the first embodiment, and the total number of air holes 50 is also increased. In accordance with the increase in the number of air holes 50 in the peripheral air hole groups 54, the number of peripheral nozzles 64 is also increased compared to the first embodiment so as to correspond to the number of air holes 50.

[0065] In particular, in this embodiment, the number of hole groups in the first row on the innermost periphery is increased compared to the first embodiment among the outer peripheral air hole groups 54 that make up the outer peripheral burner 74. Of the air holes 50 in the first row on the innermost periphery, the air holes 50 that contact the downstream boundary line D of the hole-free region R overlap the reference line L, and a portion of the air holes 50 extends upstream of the reference line L into the outer swirling flow F2.

[0066] According to the present embodiment, compared to the first embodiment, the number of air holes 50 constituting the peripheral air hole group 54 of the peripheral burner 74 and the number of peripheral nozzles 64 corresponding to the air holes 50 are increased. Therefore, compared to the first embodiment, it is possible to increase the output of the combustor 3 as a whole.

[0067] On the other hand, the non-hole region R is formed in the range where the flame spread from the central burner 71 to the inner peripheral burner 73 is the most efficient. That is, the non-hole region R is biased and arranged only in the region upstream of the outer swirling flow F2 on the reference line L, into which the flame is likely to flow in accordance with the central swirling flow F1 of the central burner 71. Therefore, it is possible to increase the output while ensuring the flame spread.

[0068] Other Embodiments Although the embodiments of the present invention have been described above, the present invention is not limited to these and can be modified as appropriate within the scope of the technical concept of the invention.

[0069] The upstream boundary line U of the hole-free region R need not only coincide with the upstream tangent line T1, but also be between the upstream tangent line T1 and the reference line L between the central burner 71 and the inner peripheral burner 73. The upstream boundary line U may also be located further upstream of the upstream tangent line T1. The upstream boundary line U may also be located downstream of the reference line L in the outer swirling flow F2. It is sufficient that there is a region in which no air holes 50 exist in the circumferential and radial directions in at least a portion of the region between the central burner 71 and the inner peripheral burner 73. It is preferable that the circumferential range of this region has a dimension equivalent to at least one air hole 50.

[0070] The downstream boundary line D of the hole-free region R may coincide with the downstream tangent line T2, for example. That is, the hole-free region R may extend over any range between the upstream tangent line T1 and the downstream tangent line T2. The downstream boundary line D may also be located further downstream than the downstream tangent line T2.

[0071] For example, the inner air hole group 53 constituting the inner burner 73 may be configured to have multiple rows instead of just one row around the outer axis P. The outer air hole group 54 constituting the outer burner 74 may be configured to have one row, or three or more rows instead of just two rows around the outer axis P.

[0072] During rated operation and partial load operation, the fuel-air ratio of the central nozzle 61 is not necessarily higher than that of the inner nozzle 63; these fuel-air ratios may be the same, or the fuel-air ratio of the inner nozzle 63 may be set higher than that of the central nozzle 61.

[0073] Furthermore, during rated operation and partial load operation, the fuel-air ratio of the inner nozzle 63 is not necessarily higher than that of the outer nozzle 64; these fuel-air ratios may be the same, or the fuel-air ratio of the outer nozzle 64 may be set higher than that of the inner nozzle 63. Even in these cases, the inner nozzle 63, which is located inside the outer nozzle 64, still plays a role in maintaining the flame of the outer nozzle 64. Furthermore, by improving flame transfer to the inner nozzle 63, the amount of fuel supplied to the inner nozzle 63 can be reduced, thereby lowering the combustion temperature.

[0074] The processing steps performed by the fuel control device 90 described above are stored in the form of a program on a recording medium that can be read by the computer 200, and the processing described above is performed by the computer 200 reading and executing this program. A specific example of the computer 200 is shown below.

[0075] 8, the computer 200 includes a CPU 100, a main memory 101, a storage 102, and an interface 103. For example, the above-described fuel control device 90 is implemented in the computer 200. The operations of the above-described processing units are stored in the storage 102 in the form of a program. The CPU 100 reads the program from the storage 102, loads it into the main memory 101, and executes the above-described processing in accordance with the program. The CPU 100 also allocates a storage area in the main memory 101 in accordance with the program.

[0076] Examples of storage 102 include a hard disk drive (HDD), a solid state drive (SSD), a magnetic disk, a magneto-optical disk, a compact disc read-only memory (CD-ROM), a digital versatile disc read-only memory (DVD-ROM), and a semiconductor memory. Storage 102 may be an internal medium directly connected to the bus of computer 200, or an external medium connected to computer 200 via interface 103 or a communication line. Furthermore, when this program is distributed to computer 200 via a communication line, computer 200 that receives the program may load the program into main memory 101 and execute the above-described processing. Storage 102 is a non-transitory tangible storage medium.

[0077] The program may also implement some of the functions described above. Furthermore, the program may be a file that can implement the functions described above in combination with a program already recorded on computer 200, that is, a so-called differential file (differential program).

[0078] In addition to or instead of the above configuration, a custom LSI (Large Scale Integrated Circuit) such as a PLD (Programmable Logic Device), an ASIC (Application Specific Integrated Circuit), a GPU (Graphics Processing Unit), or a processing device similar thereto may be provided. Examples of PLDs include programmable array logic (PAL), generic array logic (GAL), complex programmable logic device (CPLD), and field programmable gate array (FPGA). In this case, some or all of the functions realized by a processor may be realized by the integrated circuit.

[0079] <Additional Notes> The combustor 3 and the gas turbine 1 described in each embodiment can be understood, for example, as follows.

[0080] (1) A combustor 3 according to a first aspect includes an air hole plate 40 having a plurality of air holes 50 extending in a direction of a combustor axis O and opening to a downstream end surface 42, and a plurality of fuel nozzles 60 provided corresponding to the air holes 50 and supplying fuel from the upstream side to the corresponding air holes 50, wherein a central burner 71 is configured by the plurality of air holes 50 and the plurality of fuel nozzles 60 that are collectively arranged to surround the combustor axis O, and a central burner 71 is configured by the plurality of air holes 50 and the plurality of fuel nozzles 60 that are collectively arranged radially outward of the central burner 71. An outer burner 72 is configured by the central burner 71 and includes an inner burner 73 provided to surround an outer axis P located radially outward of the combustor axis O, and an outer burner 74 provided to surround the inner burner 73, and the inner burner 73 and the outer burner 74 are capable of adjusting the amount of fuel supplied to the fuel nozzle 60 independently of each other, and a hole-free region R in which the air holes 50 of the outer burner 74 are not formed is provided between the inner burner 73 and the central burner 71 at the downstream end face 42.

[0081] According to the above configuration, the flame of the central burner 71 can be guided to the inner burner 73 of the outer burner 72 via the hole-free region R. By transferring the flame of this central burner 71 to the inner burner 73, the flame stability of the inner burner 73 can be improved. As a result, the flame stability of the outer burner 74 around the inner burner 73 can be improved. Furthermore, by ensuring the flame stability of the inner burner 73, the flow rate of fuel supplied to the inner burner 73 can be reduced. This makes it possible to reduce the temperature of the flame of the inner burner 73.

[0082] (2) A combustor (3) according to a second aspect is the combustor (3) described in (1), wherein the plurality of air holes (50) constituting the central burner (71) have a swirl angle such that a central swirl flow (F1) swirling around the combustor axis O is formed, the plurality of air holes (50) constituting the outer peripheral burner (74) have a swirl angle such that an outer swirl flow (F2) swirling around the outer axis P in a direction opposite to the central swirl flow (F1), and when the downstream end surface (42) is viewed from the downstream side, an upstream boundary line (U) extending from the outer axis P in a radial direction of the outer axis P and defining an upstream end of the outer swirl flow (F2) in the hole non-formation region (R) is located in a range upstream of a reference line (L) connecting the combustor axis O and the outer axis P.

[0083] The flame of the central burner 71 follows the flow of the central swirl flow F1 and is sent in the tangential direction of the outer edge of the central burner 71. By arranging the hole-free region R so that it extends upstream of the outer swirl flow F2 of the outer burner 72 from the reference line, the flame of the central burner 71 can be guided more smoothly to the inner burner 73.

[0084] (3) The combustor 3 according to a third aspect is the combustor 3 described in (2), wherein the upstream boundary line U is located in a range from the reference line L to a tangent line on the upstream side of the outer swirl flow F2 drawn from the outer axis P to a circle that defines the outer edge of the central burner 71.

[0085] This makes it possible to ensure flame stability while ensuring the number of air holes.

[0086] (4) A combustor 3 according to a fourth aspect is the combustor 3 according to (2) or (3), wherein, when the downstream end surface 42 is viewed from the downstream side, a downstream boundary line D that extends from the outer axis P in a radial direction of the outer axis P and defines a downstream end of the outer swirling flow F2 in the hole-non-formation region R is located in a range downstream of the reference line L.

[0087] By widely expanding the non-hole forming region R, where there are no air holes 50 of the outer burner 74, to the downstream side of the outer swirling flow F2 of the outer burner 72, the flame can be more reliably transferred from the central burner 71 to the inner burner 73.

[0088] (5) A combustor 3 according to a fifth aspect is the combustor 3 according to (4), wherein the downstream boundary line D is located in a range from the reference line L to a downstream tangent to the outer swirl flow F2 that is drawn from the outer axis P to a circle that defines an outer edge of the central burner 71.

[0089] This makes it possible to ensure flame stability while ensuring the number of air holes.

[0090] (6) A combustor according to a sixth aspect is the combustor 3 according to any one of (2) to (5), wherein the region of the hole-non-formation region R upstream of the outer swirling flow F2 from the reference line L is wider than the region of the hole-non-formation region R downstream of the outer swirling flow F2 from the reference line L.

[0091] This improves the flame transfer from the central burner 71 to the inner burner 73 while ensuring a large area for forming the outer burner 74 on the outer burner 72, thereby ensuring the output of the combustor 3.

[0092] (7) A combustor 3 according to a seventh aspect is the combustor 3 according to (2) or (3), wherein, when the downstream end surface 42 is viewed from the downstream side, a downstream boundary line D extending from the outer axis P in a radial direction of the outer axis P and defining a downstream end of the outer swirling flow F2 in the hole-non-formation region R is located downstream of the outer swirling flow F2 with respect to the upstream boundary line U and in a range upstream of the outer swirling flow F2 with respect to the reference line L.

[0093] This improves the flame transfer from the central burner 71 to the inner burner 73, while also ensuring a larger area for forming the outer burner 74 on the outer burner 72, thereby ensuring greater output from the combustor 3.

[0094] (8) A gas turbine 1 according to an eighth aspect is a gas turbine 1 including: the combustor 3 according to any one of (1) to (8); a compressor 2 that compresses air and supplies the compressed air to the combustor 3; a turbine 4 that is driven by combustion gas generated by the combustor 3; and a fuel control device 90 that controls the amount of fuel supplied to the fuel nozzle 60 of the combustor 3, wherein the fuel control device 90 sets the amount of fuel supplied so that, at rated load, the fuel-air ratio of the central burner 71 is larger than the fuel-air ratio of the outer peripheral burner 74 and so that the fuel-air ratio of the inner peripheral burner 73 is larger than the fuel-air ratio of the outer peripheral burner 74.

[0095] This makes it possible to more reliably perform flame stabilization of the inner burner 73 by the central burner 71, and flame stabilization of the outer burner 74 by the inner burner 73. Furthermore, the flame can be transferred from the central burner 71, so that the inner burner 73 can sufficiently maintain flame stability without needing to unnecessarily increase the fuel-air ratio of the inner burner 73. Therefore, the inner burner 73 can reliably perform flame stabilization of the outer burner 74, making it possible to achieve low NOx emissions and stable operation.

[0096] According to the combustor and gas turbine according to the present disclosure, it is possible to achieve low NOx emissions while maintaining stable operation.

[0097] REFERENCE SIGNS LIST 1 gas turbine 2 compressor 3 combustor 4 turbine 10 outer casing 20 end cover 21 first fuel header 22 second fuel header 23 third fuel header 30 inner casing 40 air hole plate 41 upstream end face 42 downstream end face 50 air hole 51 central air hole group 52 outer air hole group 53 inner circumferential air hole group 54 outer circumferential air hole group 60 fuel nozzle 61 central nozzle 62 outer nozzle 63 inner circumferential nozzle 64 outer circumferential nozzle 71 central burner 72 outer burner 73 inner circumferential burner 74 outer circumferential burner 80 fuel supply system 81 first fuel line 81a first fuel adjustment valve 82 second fuel line 82a second fuel adjustment valve 83 third fuel line 83a third fuel adjustment valve 90 fuel control device 91 Output requirement acquisition unit 92 Fuel distribution setting unit 93 Regulating valve control unit 100 CPU 101 Main memory 102 Storage 103 Interface 200 Computer O Combustor axis P Outer axis L Reference line U Upstream boundary line D Downstream boundary line R Hole non-formation region F1 Central swirl flow F2 Outer swirl flow T1 Upstream tangent line T2 Downstream tangent line

Claims

a central burner is formed by the plurality of air holes and the plurality of fuel nozzles arranged collectively to surround the combustor axis, and an outer burner is formed by the plurality of air holes and the plurality of fuel nozzles arranged collectively to the radially outside of the central burner, the outer burner includes: an inner peripheral burner arranged to surround an outer axis located radially outside the combustor axis, and an outer peripheral burner arranged to surround the inner peripheral burner, the amount of fuel supplied to the fuel nozzle of the inner peripheral burner and the outer peripheral burner are adjustable independently of each other, and a hole non-formation region in which the air holes of the outer peripheral burner are not formed is provided between the inner peripheral burner and the central burner at the downstream end face.

2. The combustor according to claim 1, wherein the plurality of air holes constituting the central burner have a swirl angle such that a central swirl flow is formed that swirls around the combustor axis, the plurality of air holes constituting the outer peripheral burner have a swirl angle such that an outer swirl flow is formed that swirls around the outer axis in a direction opposite to the central swirl flow, and an upstream boundary line extending from the outer axis in a radial direction of the outer axis and defining the upstream end of the outer swirl flow in the hole non-formation region is located in a range upstream of a reference line connecting the combustor axis and the outer axis, when the downstream end face is viewed from the downstream side.

3. A combustor as claimed in claim 2, wherein said upstream boundary line is located in a range from said reference line to an upstream tangent to said outer swirl drawn from said outer axis to a circle defining an outer edge of said central burner.

4. A combustor as set forth in claim 2 or 3, wherein, when the downstream end face is viewed from the downstream side, a downstream boundary line extending from the outer axis in a radial direction of the outer axis and defining a downstream end of the outer swirling flow in the hole-free region is located in a range downstream of the reference line.

5. A combustor as claimed in claim 4, wherein said downstream boundary line lies in a range from said reference line to a downstream tangent to said outer swirl drawn from said outer axis to a circle defining an outer edge of said central burner.

6. A combustor according to claim 4, wherein the non-hole-formed region is wider on an upstream side of the outer swirling flow from the reference line than on a downstream side of the outer swirling flow from the reference line.

7. A combustor as claimed in claim 2 or 3, wherein, when the downstream end face is viewed from the downstream side, a downstream boundary line extending from the outer axis in a radial direction of the outer axis and defining a downstream end of the outer swirling flow in the hole-free region is located in a range downstream of the outer swirling flow from the upstream boundary line and upstream of the outer swirling flow from the reference line.

8. A gas turbine comprising: a combustor as claimed in claim 1; a compressor which compresses air and supplies it to said combustor; a turbine driven by combustion gas produced by said combustor; and a fuel control device which controls the amount of fuel supplied to said fuel nozzle of said combustor, wherein said fuel control device sets the amount of fuel supplied so that, at rated load, the fuel-air ratio of said central burner is greater than the fuel-air ratio of said outer peripheral burner and so that the fuel-air ratio of said inner peripheral burner is greater than the fuel-air ratio of said outer peripheral burner.

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