Combustor and combustion method

Abstract

To improve the combustibility of a fuel without utilizing a fuel gas with a high calory.SOLUTION: A combustor 10 includes: a combustor main body 20 that has a combustion chamber 24 therein; a main extruding portion 25 that extrudes a first burn-resistant fuel in the combustion chamber 24 in the main extruding direction; a spiral flow generative extruding portion 27 which extrudes a second burn-resistant fuel in the combustion chamber 24, and which generates a spiral flow around the first burn-resistant fuel; and a drawn opening 35 which is formed in a position facing the main extruding portion of the combustor main body 20 in the main extruding direction, has a smaller aperture cross-sectional area than the cross-sectional area of the combustion chamber 24 at a position where the spiral flow generative extruding portion 27 is provided and in the orthogonal direction to the main extruding direction, and is open to the exterior of the combustor main body 20.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a combustor and a combustion method using the combustor. [Background technology]

[0002] Conventionally, various proposals have been made to stably burn biogas and ammonia, which are flame-retardant fuels. For example, Patent Document 1 proposes a technology in which a combustion supporting fuel such as city gas is ignited in a first combustion chamber to form a swirling flame, and biogas is supplied to a second combustion chamber arranged in series with the first combustion chamber, swirled, and combusted. However, the technology of Patent Document 1 requires the use of high-calorie city gas or the like as a combustion supporting fuel.

[0003] Patent Document 2 proposes a technique for burning solid fuel such as pulverized coal or biomass in a furnace by supplying ammonia and air downstream of the outlet of the solid fuel to the furnace to co-combust the solid fuel and ammonia. Patent Document 2 can suppress the increase in nitrogen compounds due to the combustion of ammonia, but there is room for improvement in order to stably burn low-flammability fuel. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2006-207938 A [Patent Document 2] JP 2019-203631 A Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a combustor that improves the combustibility of fuel without using high-calorie fuel gas. [Means for solving the problem]

[0006] In order to achieve the above object, a combustor according to a first aspect of the present invention includes: a combustor body having a combustion chamber therein; a main ejection portion which ejects a first fuel into the combustion chamber in a main ejection direction; a swirl flow generating ejection portion which ejects a second fuel into the combustion chamber to generate a swirl flow around the first fuel; and a throttle opening portion which is formed in a position of the combustor body facing the main ejection direction from the main ejection portion, has an opening cross-sectional area smaller than a cross-sectional area of ​​the combustion chamber in a direction perpendicular to the main ejection direction at a position where the swirl flow generating ejection portion is provided, and is opened to an outside of the combustor body.

[0007] The combustor according to claim 1 includes a combustor body, a main ejection part, a swirl flow generating ejection part, and a throttle opening. The combustor body has a combustion chamber therein, into which a first fuel and a second fuel are ejected. The first fuel is ejected from the main ejection part in the main ejection direction. The second fuel is ejected from the swirl flow generating ejection part which generates a swirl flow around the ejection direction of the first fuel, and a swirl flow is generated around the first fuel in the combustion chamber.

[0008] At the throttling opening formed at a position opposite the main ejection portion, the opening cross-sectional area is smaller than the cross-sectional area in a direction perpendicular to the ejection direction of the main ejection portion at the position where the swirling flow generating ejection portion is provided, so that the swirling flow has a narrowed swirl radius, and in the vicinity of the throttling opening, the swirling flow strongly penetrates from the outer periphery into the flow of the first fuel ejected from the main ejection portion.

[0009] This allows the elements necessary for combustion to be concentrated on the inside of the swirling flow, thereby improving the combustibility of the first fuel and the second fuel.

[0010] In the combustor according to claim 2, the combustion chamber has a cylindrical shape with the main ejection direction being the cylindrical axis direction, and the swirl flow generating ejection portion is provided on a side surface of the combustion chamber.

[0011] According to the combustor of claim 2, a swirling flow can be easily generated with a simple configuration.

[0012] In the combustor according to a third aspect, the swirl flow generating jetting portion jets the second fuel along a side surface of the combustion chamber, on an upstream side of the combustion chamber.

[0013] According to the combustor of claim 3, a swirling flow can be effectively generated along the outer periphery of the flow of the main jet on the upstream side of the combustion chamber.

[0014] In the combustor according to claim 4, the throttle opening cross-sectional area is larger than the jet opening area of ​​the main jet portion.

[0015] According to the combustor of claim 4, an increase in flow resistance at the throttle opening can be suppressed.

[0016] In the combustor according to claim 5, the length of the throttle opening in the main ejection direction is longer than the ejection opening radius of the main ejection portion and shorter than the opening diameter of the throttle opening.

[0017] In the combustor according to claim 5, since the throttle opening is set to be longer than the ejection opening radius, the elements necessary for combustion are forcibly mixed inside the swirling flow when passing through the throttle opening, and a concentrated portion is secured. Also, since the throttle opening is shorter than the opening diameter of the throttle opening, it is possible to suppress an increase in the size of the combustor in the portions other than the combustion chamber.

[0018] In the combustor according to claim 6, the distance from the main ejection portion of the combustion chamber to the throttle opening is equal to or greater than the maximum width of the combustion chamber in a direction perpendicular to the main ejection direction.

[0019] According to the combustor of claim 6, the swirl of the swirl flow generated by the swirl flow generating jetting portion can be efficiently utilized.

[0020] A combustion method according to claim 7 is a combustion method in the combustor according to any one of claims 1 to 6, wherein a non-flammable fuel is used as the first fuel and the second fuel, the second fuel is premixed with air and injected into the combustion chamber to be ignited, and the first fuel is premixed with air and injected into the combustion chamber.

[0021] According to the combustor of claim 7, the fuel and air are mixed before being jetted into the combustion chamber, so that the combustor can have a simple configuration. Also, by igniting the swirling flow of the second fuel before the main jet is jetted, it is possible to effectively supply heat and radicals required for combustion to the outer periphery of the main jet.

[0022] In the combustion method according to an eighth aspect of the present invention, at least one of the first fuel and the second fuel is ammonia or biogas.

[0023] In this way, by using ammonia or biogas as a flame-retardant fuel, it is possible to achieve CO2-free combustion. Note that biogas here includes biosyngas, biofermentation gas, etc. Effect of the Invention

[0024] As described above, according to the present invention, it is possible to provide a combustor that improves the combustibility of fuel without using high-calorie fuel gas. [Brief description of the drawings]

[0025] [Figure 1] FIG. 2 is a side view of the combustor of the present embodiment. [Diagram 2] 2 is a cross-sectional view taken along line 2-2 of FIG. 1. [Diagram 3] 3 is a cross-sectional view taken along line 3-3 of FIG. 1. [Figure 4] FIG. 2 is a schematic diagram illustrating the flows of a main jet flow and a swirl flow in a combustion chamber. [Diagram 5] 1A and 1B are diagrams showing the vorticity of a space in which a combustion analysis of the combustor of the present embodiment was performed, in which (A) is a longitudinal cross-sectional view and (B) is a transverse cross-sectional view taken along line BB. [Figure 6] 1A and 1B are diagrams showing the OH radical volume concentration in a space where a combustion analysis of the combustor of the present embodiment was performed, where (A) is a vertical cross-sectional view and (B) is a horizontal cross-sectional view along line BB. [Figure 7] 1 is a graph showing the relationship between the main jet flow and the air ratio, and the quenching boundary. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] An embodiment of the present invention will be described below. Fig. 1 is a side view of a combustor 10 of this embodiment, Fig. 2 is a cross-sectional view taken along line 2-2 in Fig. 1, and Fig. 3 is a cross-sectional view taken along line 3-3 in Fig. 1. As shown in Figs. 1 to 3, the combustor 10 includes a combustor body 20, a first supply pipe 12, a second supply pipe 16, and a throttle section 30.

[0027] The combustor body 20 has a tubular portion 22, an upper flange portion 26, and a lower support portion 28. The tubular portion 22 is cylindrical with a bottom, and is formed to include a side wall 22A of the cylinder and a circular bottom portion 22B at the lower end of the side wall 22A, as shown in Fig. 2. A heat insulating material 23 is provided inside the tubular portion 22 so as to cover the entire inner circumferential surface of the side wall 22A and the upper surface of the bottom portion 22B. A combustion chamber 24 is formed by the space inside the heat insulating material 23. The combustion chamber 24 is cylindrical, and the axial direction S of the cylinder corresponds to a main ejection direction S, which is the ejection direction of a first non-combustible fuel described later.

[0028] A main ejection part 25 is formed in the center of the bottom 22B and in a part of the heat insulating material 23 corresponding to the center. The main ejection part 25 opens into the combustion chamber 24, and is connected to a first supply pipe 12 described later. As shown in FIG. 3, two swirl flow generating ejection parts 27 are formed at the end of the side wall 22A and the heat insulating material 23 on the bottom 22B side. As shown in FIG. 3, the two swirl flow generating ejection parts 27 are formed at symmetrical positions with respect to the center of the combustion chamber 24 in a plan view. The swirl flow generating ejection part 27 opens into the combustion chamber 24, and is connected to a second supply pipe 16 described later to eject the second flame-retardant fuel. The ejection direction from the swirl flow generating ejection part 27 to the combustion chamber 24 is along the tangential direction in a plan view.

[0029] 2, upper flange portion 26 is in the form of a ring plate having a larger diameter than tubular portion 22, and is disposed so that the outer circumferential upper end portion of tubular portion 22 is fitted into ring opening 26A. A convex shape 26B is formed around ring opening 26A of upper flange portion 26. Outside convex shape 26B of upper flange portion 26, a plurality of connecting holes 26C for connecting to a boiler (not shown) together with a throttle portion 30 (described later) are formed penetrating in the plate thickness direction.

[0030] The lower support portion 28 is in the shape of a disk having a larger diameter than the cylindrical portion 22, and is concentrically arranged on the lower surface of the bottom portion 22B of the cylindrical portion 22. The lower support portion 28 has a lower support opening 28A formed at a position corresponding to the central main ejection portion 25. In addition, a convex shape 28B is formed surrounding the outer periphery of the cylindrical portion 22. The lower support portion 28 may be omitted.

[0031] The throttle portion 30 is disposed at the upper end of the upper flange portion 26 and the tube portion 22. The throttle portion 30 has a disk-shaped throttle body portion 32 and a heat insulating material 34 formed of the same material as the heat insulating material 23. The throttle body portion 32 has approximately the same diameter as the upper flange portion 26, and a connecting hole 32C is formed at a position corresponding to the connecting hole 26C. The throttle body portion 32 and the upper flange portion 26 are joined to a mounting portion of the boiler (not shown) by inserting a bolt (not shown) through the connecting hole 32C and the connecting hole 26C and fastening them with a nut (not shown). In addition, a circular recess 32A having approximately the same diameter as the inner diameter of the tube portion 22 is formed in the center of the throttle body portion 32. A through opening 32B is formed in the center of the recess 32A.

[0032] A heat insulating material 34 is fitted into the recess 32A. The heat insulating material 34 is disk-shaped and has a thickness substantially equal to the depth of the recess 32A, and has a through opening 34B formed at a position corresponding to the central through opening 32B. The through opening 34B has the same diameter as the through opening 32B. The through openings 34B and 32B form a throttle opening 35. The combustion chamber 24 is formed inside and surrounded by the heat insulating material 23 and the heat insulating material 34.

[0033] The inner diameter (opening diameter) D1 of the throttle opening 35 is set smaller than the inner diameter D0 of the combustion chamber 24. That is, the cross-sectional area of ​​the throttle opening 35 in a direction perpendicular to the axial direction S is set smaller than the cross-sectional area of ​​the combustion chamber 24 in a direction perpendicular to the axial direction S. Also, the inner diameter D1 of the throttle opening 35 is set larger than the inner diameter D2 of the main ejection portion 25. That is, the cross-sectional area of ​​the throttle opening 35 in a direction perpendicular to the axial direction S is set larger than the cross-sectional area of ​​the main ejection portion 25 in a direction perpendicular to the axial direction S.

[0034] The length S1 of the throttle opening 35 in the axial direction S is set to be longer than the jetting opening radius R2 (½ of D2) of the main jetting part 25. In addition, the length S1 of the throttle opening 35 in the axial direction S is set to be shorter than the inner diameter D1 of the throttle opening 35.

[0035] The main ejection part 25 is formed penetrating from the tip of the first supply pipe 12 through the bottom part 22B and the heat insulating material 23, and the first non-combustible fuel is ejected and supplied from the main ejection part 25 to the combustion chamber 24. The first non-combustible fuel is premixed with air in an air mixing part (not shown) and supplied to the first supply pipe 12. The first non-combustible fuel premixed with air is ejected and supplied from the main ejection part 25 to the combustion chamber 24. As a result, a main jet M of the first non-combustible fuel is generated in the combustion chamber 24 (see FIG. 4).

[0036] The distance S0 from the main ejection part 25 of the combustion chamber 24 to the throttle opening 35 must be a length that maintains a certain degree of strength of the swirling flow from the upstream side (lower part) to the downstream side (upper part) of the combustion chamber 24, and if the distance is too long, the swirling strength decreases. Therefore, it is preferable that the distance S0 is set to be longer than the inner diameter D0 of the combustion chamber 24 (the maximum width of the combustion chamber 24) and shorter than approximately three times the inner diameter D0 of the combustion chamber 24.

[0037] The swirling flow generating jetting portion 27 is formed penetrating the side wall 22A and the heat insulating material 23 of the tube portion 22 from the tip end of the pair of second supply pipes 16, and the second non-combustible fuel is jetted from the swirling flow generating jetting portion 27 to the combustion chamber 24 along the inner side wall of the combustion chamber 24. The second non-combustible fuel is premixed with air in an air mixing portion (not shown) and supplied to the second supply pipe 16. The first non-combustible fuel premixed with air is jetted from the swirling flow generating jetting portion 27 to the combustion chamber 24. As a result, a swirling flow N of the second non-combustible fuel is generated in the combustion chamber 24 (see FIG. 4). The jetting opening radius R1 of the swirling flow generating jetting portion 27 is set to be smaller than the jetting opening radius R2 of the main jetting portion 25.

[0038] Ammonia or biogas can be used as the first and second flame-retardant fuels. The first and second flame-retardant fuels may be the same type of fuel or different types of fuel. That is, both the first and second flame-retardant fuels may be ammonia or biogas. Also, one of the first and second flame-retardant fuels may be ammonia and the other may be biogas.

[0039] Next, a combustion operation in the combustor 10 according to this embodiment will be described. When starting combustion in the combustor 10, first, the second non-combustible fuel premixed with air is supplied to the pair of second supply pipes 16, and is ejected from the swirl flow generating ejection portion 27 into the combustion chamber 24 as a swirl flow N, and is ignited in the combustion chamber 24 by an igniter (not shown). This allows a flame of the swirl flow N to be generated along the inner side surface of the combustion chamber 24. The flame of the swirl flow N becomes a spiral flow from the bottom 22B of the combustion chamber 24 toward the throttle portion 30. In the flame of the swirl flow N, active chemical species (OH radicals, H radicals, O radicals, etc.) necessary for combustion and thermal energy are generated.

[0040] Next, while maintaining the flame of the swirling flow N, the first non-combustible fuel premixed with air is supplied to the first supply pipe 12 and is ejected from the main ejection part 25 into the combustion chamber 24 as a main jet M. As a result, the main jet M of the first non-combustible fuel flows from the main ejection part 25 toward the throttle opening 35 in the central part of the combustion chamber 24 when viewed from above. The main jet M flows inside the flame of the swirling flow N flowing in a spiral shape, and active chemical species and thermal energy required for combustion are supplied from the flame of the swirling flow N to the outer periphery of the main jet M.

[0041] The main jet M burns by obtaining the supplied active chemical species and thermal energy. Here, the active chemical species and thermal energy of the flame of the swirling flow N are consumed sequentially from the upstream side (bottom 22B side), and the vorticity of the swirling flow N weakens as it moves downstream (throttle opening 35), so that the active chemical species and thermal energy supplied to the main jet M decrease. However, the combustor 10 of this embodiment has the throttle opening 35. The swirling flow N has a swirling radius narrowed by the throttle opening 35 on the downstream side of the combustion chamber 24, and the active chemical species in the flame of the swirling flow N are forcibly mixed and concentrated at the center of the swirl. As a result, near the throttle opening 35 provided on the downstream side of the combustion chamber 24, high-density active chemical species and heat strongly enter the outer periphery of the main jet M. Therefore, the combustion of the main jet M can be strengthened.

[0042] 5 shows the space used in the combustion analysis of the combustor 10. In Fig. 5(A) and (B), in the case where ammonia is used as the first and second non-combustible fuels, the combustion chamber 24, the throttle opening 35, and the virtual space E for confirming the flame are surrounded by dotted lines. As shown in Fig. 5(A), the high vorticity parts can be confirmed on the outer periphery on the upstream side of the main jet and along the inner wall of the throttle opening 35.

[0043] 6(A) and 6(B), the areas with a high OH radical volume ratio are surrounded by dotted lines in the combustion chamber 24, the throttle opening 35, and the virtual space E for observing the flame. As shown in Fig. 6(A), it can be seen that the area with a high OH radical volume ratio is constricted toward the inside of the swirl just before the throttle opening 35, and a high OH radical volume ratio is maintained within the throttle opening 35.

[0044] According to the combustor 10 of the present embodiment, the combustibility of the main jet M can be improved and high load combustion can be maintained by using the swirl flow N and the throttle opening 35. Note that the high load combustion here means combustion that increases the amount of fuel burned per unit time and the amount of fuel burned per unit volume.

[0045] Furthermore, the swirling flow is generated by ejecting the second flame-retardant fuel from the swirling flow generating ejection portion 27 arranged on the side surface of the combustion chamber 24 along the inner side wall of the combustion chamber 24, so that the swirling flow can be generated with a simple configuration. In this embodiment, the swirling flow generating ejection portion 27 is provided in two locations, but it may be provided in only one location, or in three or more locations. Furthermore, the ejection direction from the swirling flow generating ejection portion 27 to the combustion chamber 24 may be a direction along the outer periphery of the main jet that can generate a swirling flow.

[0046] In this embodiment, the cross-sectional area of ​​the throttle opening 35 is set to be larger than the cross-sectional area of ​​the main ejection part 25 in the direction perpendicular to the axial direction, but this is not necessarily required, and the cross-sectional area of ​​the throttle opening 35 may be approximately the same as or smaller than the cross-sectional area of ​​the main ejection part 25 in the direction perpendicular to the axial direction S. By setting the cross-sectional area relationship as in this embodiment, it is possible to suppress an increase in the flow path resistance of the throttle opening 35, which is the outlet of the first and second non-combustible fuels ejected into the combustion chamber 24. Also, as shown in FIG. 4, the inlet portion of the opening 35 may be rounded.

[0047] In this embodiment, the length S1 of the axial direction S of the throttle opening 35 is set to be longer than the jet opening radius R2 of the main jet section 25, but this is not necessarily required, and the length S1 may be equal to or shorter than the jet opening radius R2. By making the length S1 longer than the jet opening radius R2 as in this embodiment, a path for concentrating active chemical species and thermal energy required for combustion to the inside of the swirling flow N when passing through the throttle opening 35 is secured.

[0048] In addition, in this embodiment, the length S1 in the axial direction S of the throttle opening 35 is set to be shorter than the inner diameter D1 of the throttle opening 35, but this is not necessarily required, and the length S1 may be set to be longer than the inner diameter D1. By making the length S1 in the axial direction S shorter than the inner diameter D1 of the throttle opening 35 as in this embodiment, it is possible to suppress an increase in the size of the combustor 10.

[0049] In addition, in this embodiment, the distance S0 from the main ejection portion 25 of the combustion chamber 24 to the throttle opening 35 is set to be longer than the inner diameter D0 (maximum width of the combustion chamber 24) of the combustion chamber 24, but this is not necessarily required, and the distance S0 may be shorter than the inner diameter D0. By making the distance S0 longer than the inner diameter D0 as in this embodiment, it is possible to efficiently utilize the swirl of the circumferential swirling flow N generated by the ejection of the second flame-retardant fuel.

[0050] In addition, in this embodiment, the distance S0 from the main ejection portion 25 of the combustion chamber 24 to the throttle opening 35 is set to be shorter than three times the inner diameter D0 (maximum width of the combustion chamber 24) of the combustion chamber 24, but this is not necessarily required, and the distance S0 may be longer than three times the inner diameter D0. By making the distance S0 shorter than three times the inner diameter D0 as in this embodiment, it is possible to efficiently utilize the swirl of the circumferential swirling flow N generated by the ejection of the second flame-retardant fuel.

[0051] In addition, in this embodiment, the first and second non-combustible fuels are premixed with air before being injected into the combustion chamber 24, but this is not necessarily required, and the air may be mixed within the combustion chamber 24. By premixing the air as in this embodiment, the combustor 10 can be simplified in configuration.

[0052] In addition, in this embodiment, ammonia and biogas are used as the first and second flame-retardant fuels, but other flame-retardant fuels may be used, such as off-gas containing a large amount of non-combustible components discharged in the biogas refining process, gas containing a large amount of nitrogen in the biosyngas manufacturing process, ammonia decomposition gas (off-gas), etc. In this embodiment, by using ammonia and biogas as the first and second flame-retardant fuels, CO2-free combustion can be achieved.

[0053] [Test example] In order to confirm the combustion effect of the combustor 10 of the present embodiment, a combustion experiment was carried out in the combustor 10 under the following conditions.

[0054] (Combustion chamber 24): Inner diameter D0: 40mm :Distance S0:50mm (Aperture opening 35): Inner diameter D1: 25mm Length S1: 18mm (Swirling flow generation jet part 27): Radius R1: 2mm (Main spout part 25): Radius R2: 5mm

[0055] <1> As shown in Table 1, the first and second non-flammable fuels were biogas, the swirl flow velocity and the swirl air ratio were fixed, and the flow velocity of the main jet M and the air ratio of the main jet M were changed.

[0056] [Table 1]

[0057] Figure 7 shows the relationship between the air ratio and the main jet M, and a graph of the quenching boundary as a result of the above experiment. With an air ratio of 1, the flame was not blown out even with a main jet M of 45 m / s, and high-load combustion was confirmed. In addition, it was confirmed that this combustor can secure a wide range of turndown ratios.

[0058] <2> As shown in Table 2, the first and second non-flammable fuels were ammonia, the swirl flow velocity, swirl air ratio, and main jet air ratio were fixed, and the flow velocity of the main jet M was changed between 7 m / s and 9 m / s.

[0059] [Table 2]

[0060] Stable combustion was confirmed for both the flow velocities of the main jet M of 7 m / s and 9 m / s. The combustion velocity (laminar flow propagation velocity) of ammonia is 0.07 m / s, and it was confirmed that the combustor 10 of this embodiment can propagate a flame and maintain a stable flame even when the flow velocity of the main jet M is 100 times or more the combustion velocity of ammonia, making high-load combustion possible.

[0061] Furthermore, by changing the flow velocity of the main jet M between 0 m / s and 10 m / s, a wide range of turndown ratios from approximately 20% to 100% can be achieved. The turndown ratio is the ratio of the maximum combustion load to the minimum combustion load at which stable combustion is possible, and it was confirmed that excellent combustion control can be achieved. [Explanation of symbols]

[0062] 10 Combustor 20 Combustor body 24 Combustion chamber 25 Main spout 27 Swirl flow generation jet part 35 Aperture

Claims

1. A combustor body having a combustion chamber therein; a main ejection portion that ejects the first fuel in a main ejection direction into the combustion chamber; a swirl flow generating ejection portion that ejects a second fuel into the combustion chamber to generate a swirl flow around the first fuel; a throttle opening formed in a position facing the main ejection direction from the main ejection portion of the combustor body, the throttle opening having an opening cross-sectional area smaller than a cross-sectional area in a direction perpendicular to the main ejection direction at a position where the swirl flow generating ejection portion of the combustion chamber is provided, and the throttle opening is opened to the outside of the combustor body; A combustor comprising:

2. The combustion chamber has a cylindrical shape with the main ejection direction being a cylinder axis direction, and the swirl flow generating ejection portion is provided on a side surface of the combustion chamber. The combustor of claim 1 .

3. The swirl flow generating jetting portion jets the second fuel along a side surface of the combustion chamber on an upstream side of the combustion chamber. The combustor of claim 2 .

4. The throttle opening cross-sectional area is larger than the jet opening area of ​​the main jet portion. The combustor according to any one of claims 1 to 3.

5. The length of the throttle opening in the main ejection direction is longer than the ejection opening radius of the main ejection portion and shorter than the opening diameter of the throttle opening. The combustor according to any one of claims 1 to 4.

6. The distance from the main ejection portion of the combustion chamber to the throttle opening is equal to or greater than the maximum width of the combustion chamber in a direction perpendicular to the main ejection direction. The combustor according to any one of claims 1 to 5.

7. A combustion method in the combustor according to any one of claims 1 to 6, A non-flammable fuel is used as the first fuel and the second fuel, premixing the second fuel with air and injecting the premix into the combustion chamber and igniting the premix; premixing the first fuel with air and injecting the premixed fuel into the combustion chamber; Combustion method.

8. At least one of the first fuel and the second fuel is ammonia or biogas; The combustion method according to claim 7.

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