BURNER, COMBUSTION CHAMBER EQUIPPED THEREWITH AND GAS TURBINE EQUIPPED WITH COMBUSTION CHAMBER

Abstract

This burner includes a mixing tube in which a mixing space is formed, and a fuel nozzle disposed in the mixing space. The fuel nozzle includes a nozzle main body extending in an extending direction of the mixing space, and a protruding portion protruding from an outer peripheral surface of the nozzle main body and spaced from an inner peripheral surface of the mixing tube. The nozzle main body has a fuel discharge port capable of discharging fuel into the mixing space. The protruding portion, as it extends in a circumferential direction relative to the nozzle main body, gradually extends toward a downstream side in the extending direction, and the entire protruding portion is formed in a spiral shape around the nozzle main body.

Description

Technical area

[0001] The present disclosure relates to a combustor, a combustor containing the combustor, and a gas turbine containing the combustor.

[0002] Priority is claimed to Japanese Patent Application No. 2022-168852 filed on October 21, 2022, the contents of which are incorporated herein by reference. State of the art

[0003] Gas turbines contain a compressor that compresses the air, a combustor that burns the fuel with the air compressed by the compressor to produce combustion gas, and a turbine that is driven by the combustion gas from the combustor.

[0004] PTL 1 discloses a combustor including a tube in which a combustion chamber in which a hydrogen-containing fuel is burned is formed, a plurality of fuel nozzles, and a plate. The tube has openings formed at one end on a downstream side and one end on an upstream side in an extending direction of the tube. The plate is arranged to close the opening of the end of the tube on the downstream side. A plurality of air holes are formed in the plate, penetrating the plate in the extending direction. A tip portion of the fuel nozzle is inserted into the plurality of air holes. Swirl grooves are formed on the inner peripheral surfaces of the plurality of air holes, gradually extending toward the downstream side as the swirl grooves extend in a circumferential direction of the holes.

[0005] The gas flow rate near the inner peripheral surface of the air hole is slower than the gas flow rate near the center axis of the air hole. Therefore, when the fuel concentration near the inner peripheral surface of the air hole is high, backfire, which is a flame in the combustion chamber that is transmitted to the air hole, is likely to occur.

[0006] In the combustion chamber described in PTL 1, in a process where the compressed air from the compressor passes through the air hole, the compressed air becomes a swirl flow due to the swirl groove formed on the inner peripheral surface of the air hole. A hydrogen-containing fuel is ejected from the fuel nozzle into the swirl flow. Since the compressed air has a higher density than the fuel, the compressed air is pressed against the inner peripheral surface side of the air hole due to centrifugal force, while the fuel is collected near the center axis of the air hole. That is, in this combustion chamber, the separation of fuel and air is achieved by the swirl flow. Therefore, in this combustion chamber, the backfire described above can be suppressed. Citation listPatent literature

[0007] [PTL 1] Japanese Unexamined Patent Application Publication No. 2015-014400 Summary of the inventionTechnical problem

[0008] In the combustion chamber described in PTL 1, although backfiring can be suppressed, a region where a fuel-air ratio (fuel amount / air amount) is high is generated near the center axis of the air hole, and the amount of NOx generated increases.

[0009] Therefore, an object of the present disclosure is to provide a technique capable of suppressing the generation of NOx while suppressing backfiring. Solution to the problem

[0010] According to one aspect of the present disclosure, to achieve the above object, there is provided a burner comprising: a mixing tube extending in a predetermined extension direction and in which a mixing space for mixing air and fuel is formed; and a fuel nozzle extending in the extension direction and at least a part of which is arranged in the mixing space.

[0011] The mixing tube has an air inlet through which air can flow into the mixing chamber, and an exhaust port through which a premixed gas in which the air and fuel are mixed can be exhausted from the mixing chamber. The exhaust port is formed at one end of the mixing tube on a downstream side of an upstream side, which is one side in the extending direction, and the downstream side, which is the other side in the extending direction. The fuel nozzle includes a nozzle main body extending in the extending direction and a protrusion portion protruding from an outer peripheral surface of the nozzle main body and separated from an inner peripheral surface of the mixing tube.The nozzle main body includes a fuel discharge port capable of discharging fuel into the mixing chamber from a position located downstream of the air inlet and upstream of the discharge port. The protrusion portion gradually extends toward the downstream side as the protrusion portion extends in a circumferential direction with respect to the nozzle main body, and an entire portion of the protrusion portion is formed in a spiral shape around the nozzle main body.

[0012] In the present aspect, the swirling flow of the air that has flowed into the mixing space can be formed by the protrusion portion in the region around the vicinity of the nozzle main body in a virtual plane perpendicular to the extension direction, which is a region where the protrusion portion exists in the extension direction and a region on the downstream side of the protrusion portion. Furthermore, since the protrusion portion is separated from the inner peripheral surface of the mixing tube, when the air overflows an outer peripheral surface of the protrusion portion, a small turbulence of air is generated on the downstream side in an air overflow direction on the outer peripheral surface. Further, a small turbulence of air is generated on the downstream side of the downstream end of the protrusion portion.As described above, in the present aspect, in a downstream main body surrounding area, which is an area on the downstream side of the protrusion portion and an area around the vicinity of the nozzle main body in the virtual plane perpendicular to the extending direction, a swirl flow is formed as a main air flow, and a small turbulence is formed. Therefore, in the present aspect, in the downstream main body surrounding area, the mixing of the air and the fuel jetted from the nozzle main body is promoted. Therefore, in the present aspect, the generation of a region where the fuel-air ratio (fuel amount / air amount) is high in the mixing space can be suppressed, and the generation of NOx can be suppressed.

[0013] Furthermore, in the present aspect, since the protrusion portion is separated from the inner peripheral surface of the mixing tube, it is possible to suppress the influence of the swirl flow in a region near the inner peripheral surface of the mixing tube in the virtual plane perpendicular to the extending direction, which is the region of the protrusion portion on the downstream side. Therefore, in the present aspect, the mixing of the air and fuel in the region near the inner peripheral surface is suppressed. Therefore, in the present aspect, the fuel-air ratio (fuel amount / air amount) in the region near the inner peripheral surface where the gas flow rate is low can be kept low, and backfiring, which is a flame transmitted into the mixing space, can be suppressed.

[0014] According to one aspect of the present disclosure, to achieve the above object, there is provided a combustion chamber comprising: the burner according to the above aspect; and a pipe in which the premixed gas discharged from the discharge port of the burner can be combusted.

[0015] According to one aspect of the present disclosure, to achieve the above object, there is provided a cluster burner combustor comprising: a plurality of the burners according to the above aspect; and a pipe in which the premixed gas discharged from the discharge port of each of the plurality of burners can be combusted.

[0016] The extension direction of each of the plurality of burners is the same as that of the others. The positions of the discharge ports of the plurality of burners in the extension direction are aligned with each other.

[0017] According to one aspect of the present disclosure, to achieve the above object, there is provided a gas turbine comprising: the combustor according to the above aspect; a compressor configured to compress air to generate compressed air and supply the compressed air to the combustor; and a turbine configured to be driven by a combustion gas generated by the combustion of the premixed gas in the tube of the combustor.

[0018] According to another aspect of the present disclosure, to achieve the above object, there is provided a gas turbine comprising: the cluster burner combustor according to the above aspect; a compressor configured to compress air to generate compressed air and supply the compressed air to the plurality of burners; and a turbine configured to be driven by a combustion gas generated by the combustion of the premixed gas in the tube of the cluster burner combustor. Advantageous effects of the invention

[0019] In one aspect of the present disclosure, it is possible to suppress the generation of NOx while suppressing backfiring. Brief description of the drawings Fig. 1 is a schematic view showing a configuration of a gas turbine in an embodiment according to the present disclosure. Fig. 2 is a cross-sectional view showing the gas turbine around a combustor in the embodiment according to the present disclosure. Fig. 3 is a cutaway perspective view showing a burner in the embodiment according to the present disclosure. Fig. 4 is a cross-sectional view showing the burner in the embodiment according to the present disclosure. Fig. 5 is a fragmentary perspective view showing a main part of the burner in the embodiment according to the present disclosure. Fig. 6 is a view for describing a fuel-air ratio distribution in a mixing chamber in a reference example. Fig. 7 is a view for describing a fuel-air ratio distribution in a mixing chamber in the embodiment according to the present disclosure. Fig. 8 is a fragmentary perspective view showing a main part of a burner in a first modification example according to the present disclosure. Fig. 9 is a fragmentary perspective view showing a main part of a burner in a second modification example according to the present disclosure. Fig. 10 is a cross-sectional view showing a burner in a third modification example according to the present disclosure. Description of embodiments

[0020] Hereinafter, embodiments of a combustor according to the present disclosure, a combustor including the combustor, and a gas turbine including the combustor will be described in detail with reference to the drawings, and a modification example of the combustor will be further described.

[0021] As in Fig. 1, a gas turbine in the present embodiment includes a compressor 10 capable of compressing air A to produce compressed air Acom, a plurality of combustors 20 capable of combusting a fuel F in the compressed air Acom to produce a combustion gas G, and a turbine 15 capable of being driven by the combustion gas G.

[0022] The compressor 10 includes a compressor rotor 11 rotating around a rotor axis Ar and a compressor casing 12 covering the compressor rotor 11. The turbine 15 includes a turbine rotor 16 rotating around the rotor axis Ar and a turbine casing 17 covering the turbine rotor 16. Furthermore, in the following, a direction in which the rotor axis Ar extends is referred to as a rotor axis direction Da, one side of both sides of the rotor axis direction Da is referred to as an axial upstream side Dau, and the other side is referred to as an axial downstream side Dad.

[0023] The compressor 10 is arranged on the axial upstream side Dau with respect to 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 1. For example, a rotor of a generator GEN is connected to the gas turbine rotor 1. The gas turbine further includes an intermediate casing 4 arranged between the compressor casing 12 and the turbine casing 17. The compressed air Acom from the compressor 10 flows into the intermediate casing 4. The plurality of combustion chambers 20 are arranged in a circumferential direction with respect to the rotor axis Ar and are attached to the intermediate casing 4. The compressor casing 12, the intermediate casing 4, and the turbine casing 17 are connected to each other to form a gas turbine casing 2.

[0024] A fuel line is connected to the combustion chamber 20. The combustion chamber 20 can generate the combustion gas G by burning the fuel F from the fuel line in the compressed air Acom from the compressor 10.

[0025] As in Fig. 2, the combustion chamber 20 includes a tube 21 forming a combustion space Sc in which the fuel F can be burned, a plurality of burners 30 ejecting a premixed gas Gpm in which the fuel F and the compressed air Acom are mixed within the combustion space Sc, and a burner support frame 25 supporting the plurality of burners 30.

[0026] The tube 21 is sometimes referred to as a transition piece or a combustion tube. The tube 21 has a tubular shape around a combustion chamber axis Ac. Here, a direction in which the combustion chamber axis Ac extends is referred to as an extension direction De. Moreover, one side of both sides in the extension direction De is referred to as an upstream side Deu, and the other side is referred to as a downstream side Ded. One end of the tube 21 on the upstream side Deu and one end of the tube 21 on the downstream side Ded are open. As shown in Fig. 1, an opening is formed on the downstream side Ded of the tube 21 so that the combustion gas G generated by the combustion of the fuel F can be supplied into the turbine casing 17. On the other hand, an opening 22 on the upstream side Deu of the tube 21 is blocked by the burner support frame 25. The plurality of burners 30 are arranged side by side with respect to the combustor axis Ac in a radial direction and the circumferential direction and are supported by the burner support frame 25. Therefore, the combustor 20 of the present embodiment is a cluster combustor combustor.

[0027] Each of the plurality of burners 30 includes a mixing tube 31, a fuel nozzle 34 and a plurality of nozzle holders 39, as shown in Fig. 3 and Fig. 4 shown.

[0028] Each of the mixing tubes 31 for the plurality of burners 30 extends in the extension direction De in which the combustion chamber axis Ac extends, and forms a cylindrical mixing space Sm in which the compressed air Acom and the fuel F are mixed. The mixing tube 31 has an air inlet 31i through which the compressed air Acom can flow into the mixing space Sm, an exhaust port 31o through which a premixed gas Gpm in which the compressed air Acom and the fuel F are mixed can be exhausted from the mixing space Sm, and a fuel flow path 31p. The air inlet 31i is formed at one end of the mixing tube 31 on the upstream side Deu, and the exhaust port 31o is formed at one end of the mixing tube 31 on the downstream side Ded. The mixing space Sm has a reduced area section 33 in which a cross-sectional area perpendicular to the extension direction De gradually decreases toward the downstream side Ded.The reduced area portion 33 is formed between the air inlet 31i and the discharge port 31o in the extending direction De. The cross-sectional area of an upstream side portion Deu of the reduced area portion 33 in the mixing space Sm is larger than the cross-sectional area of a downstream side portion Ded of the reduced area portion 33 in the mixing space Sm. The fuel flow path 31p penetrates from an outer peripheral surface of the mixing tube 31 to an inner peripheral surface 32, and the fuel F can flow through the fuel flow path 31p.

[0029] The fuel nozzle 34 is arranged in the mixing chamber Sm. The fuel nozzle 34 includes a nozzle main body 35 extending in the extension direction De and a plurality of protruding portions 37 protruding from an outer peripheral surface 36 of the nozzle main body 35 and separated from the inner peripheral surface 32 of the mixing tube 31.

[0030] The nozzle main body 35 is arranged on a space center axis Ab, which is a center axis of the mixing space Sm. The space center axis Ab extends in the extension direction De. The nozzle main body 35 includes a large-diameter portion 35a having a cylindrical shape around the space center axis Ab, a reduced-diameter portion 35b having a conical shape around the space center axis Ab, and a small-diameter portion 35c having a cylindrical shape around the space center axis Ab. The large-diameter portion 35a is formed in a portion of the nozzle main body 35 on the upstream side Deu. The reduced-diameter portion 35b is connected to one end of the large-diameter portion 35a on the downstream side Ded. An outer diameter of the reduced-diameter portion 35b gradually decreases toward the downstream side Ded.The small-diameter portion 35c is connected to one end of the reduced-diameter portion 35b on the downstream side Ded and extends to one end of the nozzle main body 35 on the downstream side Ded. An outer diameter of the small-diameter portion 35c is smaller than an outer diameter of the large-diameter portion 35a. The nozzle main body 35 further includes a fuel flow path 35p and a fuel discharge port 35o formed at the end of the nozzle main body 35 on the downstream side Ded. The fuel flow path 35p extends in the extension direction De inside the large-diameter portion 35a, the reduced-diameter portion 35b, and the small-diameter portion 35c. The fuel F can flow through the fuel flow path 35p.The fuel discharge port 35o can discharge the fuel F, which has flowed into the mixing space Sm through the fuel flow path 35p, to the downstream side Ded.

[0031] The protrusion portion 37 gradually extends to the downstream side Ded as the protrusion portion 37 extends in the circumferential direction with respect to the nozzle main body 35, and the entire protrusion portion 37 is formed spirally around the nozzle main body 35. In other words, the protrusion portion 37 is formed as a whole in a spiral shape around the space center axis Ab. In Fig. 4, for convenience, the protrusion portion 37 is illustrated as extending linearly in the extension direction De in order to easily understand the protrusion amount of the protrusion portion 37. The protrusion portion 37 has an upstream end 37u on the most upstream side Deu in the extension direction De and a downstream end 37d on the most downstream side Ded in the extension direction De. All of the upstream ends 37u of each of the plurality of protrusion portions 37 are located at a boundary between the large-diameter portion 35a and the reduced-diameter portion 35b in the extension direction De. All of the downstream ends 37d of each of the plurality of protrusion portions 37 are located at the end of the nozzle main body 35 on the downstream side Ded in the extension direction De.A distance from the spatial center axis Ab to an outer peripheral surface 38 of the protrusion portion 37 is equal to the outer diameter of the large-diameter portion 35a at any position in the extension direction De. For this reason, the protrusion amount, which is a distance from the outer peripheral surface 36 of the nozzle main body 35 to the outer peripheral surface 38 of the protrusion portion 37, gradually increases toward the downstream side Ded in a portion of the protrusion portion 37 formed in the reduced-diameter portion 35b of the nozzle main body 35. Moreover, the protrusion amount is a maximum protrusion amount pmax at a portion of the protrusion portion 37 formed in the small-diameter portion 35c of the nozzle main body 35.

[0032] The reduced area portion 33 of the above-described mixing space Sm is formed in a region where the protruding portion 37 is present in the extension direction De. A portion of the inner peripheral surface 32 of the mixing tube 31 located on the downstream side Ded of the reduced area portion 33 faces the outer peripheral surface 36 of the small diameter portion 35c of the nozzle main body 35 in the radial direction.A distance from a portion of the outer peripheral surface 36 of the nozzle main body 35, which is a portion where the protrusion portion 37 is present in the extension direction De, to the inner peripheral surface 32 of the mixing tube 31 is a minimum distance dmin at a distance from the outer peripheral surface 36 of the small-diameter portion 35c of the nozzle main body 35 to a portion of the inner peripheral surface 32 of the mixing tube 31, which is a portion on the downstream side Ded of the reduced area portion 33. The maximum protrusion amount pmax of the above-described protrusion portion 37 is equal to or less than 20% of the minimum distance dmin.

[0033] The plurality of nozzle holders 39 connect the outer peripheral surface 36 of the nozzle main body 35 and the inner peripheral surface 32 of the mixing tube 31 at a position on the downstream side Ded with respect to a region where the protruding portion 37 is present in the extension direction De. One nozzle holder 39 of the plurality of nozzle holders 39 has a fuel flow path 39p through which the fuel F can flow. The fuel flow path 39p communicates with the fuel flow path 31p of the mixing tube 31 and the fuel flow path 35p of the nozzle main body 35.

[0034] As in Fig. 2, a portion of the pipe 21 on the upstream side Deu is connected to one end of the burner support frame 25 on the downstream side Ded, and the opening 22 on the upstream side Deu of the pipe 21 is closed as described above. One end of the burner support frame 25 on the upstream side Deu is connected to the intermediate casing 4. In the extension direction De, the position of the end of the mixing pipe 31 on the upstream side Deu in each of the plurality of burners 30 substantially coincides with the position of the end of the burner support frame 25 on the upstream side Deu. The burner support frame 25 has a fuel flow path 26 through which the fuel F can flow and an air flow path 27 through which the compressed air Acom can flow.The fuel flow path 26 includes a main flow path 26m that receives the fuel F from the outside and through which the fuel F can flow, and a plurality of branch flow paths 26b that branch off from the main flow path 26m. Each of the plurality of branch flow paths 26b communicates with the fuel flow path 31p of the mixing tube 31 of any one of the plurality of burners 30. The air flow path 27 is formed so that the compressed air Acom from the compressor 10 can flow into the mixing space Sm for each of the plurality of burners 30.

[0035] As in Fig. 1, the compressor 10 compresses the air A to produce the compressed air Acom. The compressed air Acom is discharged from the compressor 10 into the intermediate housing 4. As shown in Fig. 2, the compressed air Acom discharged into the intermediate housing 4 flows through the air flow path 27 of the burner support frame 25 into the mixing space Sm for each of the plurality of burners 30. As shown in Fig. 2 and Fig. 4, the fuel F flows into the fuel flow path 35p of the nozzle main body 35 of each of the plurality of burners 30 through the fuel flow path 26p of the burner support frame 25, the fuel flow path 31p of the mixing tube 31 of each of the plurality of burners 30, and the fuel flow path 39p of the nozzle holder 39 of each of the plurality of burners 30. The fuel F that has flowed into the fuel flow path 35p of the nozzle main body 35 is discharged from the fuel discharge port 35o formed at the downstream end Ded of the nozzle main body 35 to the mixing space Sm. The fuel F discharged into the mixing space Sm is mixed with the compressed air Acom in the mixing space Sm and is discharged from the discharge port 31o of the mixing tube 31 into the combustion space Sc of the tube 21 as the premixed gas Gpm. The premixed gas Gpm is combusted in the combustion space Sc to become the combustion gas G.The combustion gas G is fed from the combustion chamber 20 into the turbine housing 17. The combustion gas G rotates the turbine rotor 16 in the process of flowing to the axial downstream side Dad in the turbine housing 17. A rotor of the generator GEN connected to the gas turbine rotor 1 is rotated by rotation of the turbine rotor 16.

[0036] As a result, the generator GEN produces electricity.

[0037] In the present embodiment, as shown in Fig. 5, a swirl flow Fs of the compressed air Acom that has flowed into the mixing space Sm is formed by the protruding portion 37 in the region around the vicinity of the nozzle main body 35 in the virtual plane perpendicular to the extension direction De, which is a region where the protruding portion 37 exists in the extension direction De, and a region on the downstream side Ded of the protruding portion 37. The protruding portion 37 is formed in a spiral shape around the space center axis Ab. Therefore, the swirl flow Fs is a flow that swirls around the space center axis Ab. Moreover, since the protrusion portion 37 is separated from the inner peripheral surface 32 of the mixing tube 31, when the compressed air Acom overflows the outer peripheral surface 38 of the protrusion portion 37, a small turbulence Ft1 of the air on the downstream side Ded in the air overflow direction is generated on the outer peripheral surface 38.Further, a small turbulence Ft2 of the air is also generated on the downstream side Ded of the downstream end 37d of the protruding portion 37.

[0038] In a case where the spiral projection portion 37 is not provided around the nozzle main body 35, the mixing of the compressed air Acom and the fuel F ejected from the nozzle main body 35 is not promoted, and in a downstream main body surrounding area Ra (in Fig. 4 and Fig. 7), which is a region around the vicinity of the nozzle main body 35 in the virtual plane perpendicular to the extending direction De, a region in which a fuel-air ratio (fuel amount / air amount) is high is formed as shown in Fig. 6 shown. In Fig. 6 and Fig. 7, to be described later, the color is shown to become darker as the fuel-air ratio increases.

[0039] On the other hand, in the present embodiment, as described above, in the downstream main body surrounding area Ra, which is an area on the downstream side Ded of the protruding portion 37 and is an area around the vicinity of the nozzle main body 35 in the virtual plane perpendicular to the extending direction De, the swirl flow Fs is formed as the main air flow, and small turbulences Ft1 and Ft2 are formed. For this reason, in the present embodiment, in the downstream main body surrounding area Ra, the mixing of the compressed air Acom and the fuel F ejected from the nozzle main body 35 is promoted. Specifically, in the present embodiment, the protruding portion 37 is formed in an area including the end on the downstream side Ded of the nozzle main body 35.Therefore, in the present embodiment, the influence of the swirl flow Fs and the turbulence Ft1 and Ft2 of the compressed air Acom formed by the protrusion portion 37 can be exerted more strongly on the fuel jetted from the downstream side end Ded of the nozzle main body 35 than in a case where the downstream end 37d of the protrusion portion 37 on the upstream side Deu is formed from the downstream side end Ded of the nozzle main body 35. Accordingly, in the present aspect, in the downstream main body surrounding area Ra, the compressed air Acom and the fuel F can be effectively mixed. Therefore, in the present embodiment, as shown in FIG. Fig. 7, it is possible to suppress the occurrence of a region having a high fuel-air ratio (fuel amount / air amount) in the downstream main body surrounding area Ra and to suppress the generation of NOx.

[0040] Furthermore, in the present embodiment, the protruding portion 37 is separated from the inner peripheral surface 32 of the mixing tube 31. Specifically, as described above, the maximum protrusion amount pmax of the protruding portion 37 from the outer peripheral surface 36 of the nozzle main body 35 is equal to or less than 20% of the minimum distance dmin from the outer peripheral surface 36 of the small diameter portion 35c of the nozzle main body 35 to the inner peripheral surface 32 of the mixing tube 31. Therefore, in the present embodiment, it is possible to reduce the area of the region in which a circumferential component flow rate Vc ( Fig. 7) of the swirl flow Fs is a first flow rate or higher, in the above-described downstream main body surrounding area Ra in the virtual plane perpendicular to the extending direction De. On the other hand, in the present embodiment, in the area on the downstream side Ded of the protrusion portion 37, the area of the area in which the circumferential component flow rate Vc of the swirl flow Fs is equal to or lower than a second flow rate slower than the first flow rate, in a region Rb near the inner peripheral surface (in Fig. 4 and Fig. 7) of the mixing tube 31 in the virtual plane perpendicular to the extension direction De. Therefore, in the present aspect, the mixing of the fuel F with the compressed air Acom flowing along the inner peripheral surface 32 of the mixing tube 31 can be suppressed in the region Rb near the inner peripheral surface where the gas flow rate is slow, and backfiring, which is a flame transmitted into the mixing space Sm, can be suppressed.

[0041] In the present embodiment, in the area along the inner peripheral surface 32 of the mixing tube 31, in the reduced area portion 33, an airflow is generated that has a directional component toward a center of the mixing tube 31. Due to this airflow, in the present embodiment, the swirl flow Fs formed by the protrusion portion 37 is pushed toward a center side of the mixing tube 31. Therefore, in the present embodiment, in the above-described downstream main body surrounding area Ra in the virtual plane perpendicular to the extension direction De, a region where the circumferential component flow rate Vc of the swirl flow Fs is equal to or higher than the first flow rate is located near the center of the mixing tube 31.As a result, in the present embodiment, it is possible to reduce the area of the region where the circumferential component flow rate Vc of the swirl flow Fs is equal to or higher than the first flow rate. Further, the cross-sectional area of the mixing space Sm on the downstream side Ded of the reduced-area portion 33 is smaller than the cross-sectional area of the mixing space Sm on the upstream side Deu of the reduced-area portion 33. For this reason, in the present embodiment, the gas flow rate in the mixing space Sm on the downstream side Ded of the reduced-area portion 33 in the extending direction De is higher than the gas flow rate in a case where the reduced-area portion 33 is not present. Therefore, in the present embodiment, backfiring, which is the flame transmitted into the mixing space Sm, can be effectively suppressed.

[0042] The air that has flowed into the mixing space Sm undergoes pressure loss through the nozzle holder 39. Moreover, when a part of the mixing space Sm is occupied by the nozzle holder 39, a region where the compressed air Acom flows in the mixing space Sm becomes narrow, the flow rate of the compressed air Acom increases, and the pressure loss of the air due to the nozzle holder 39 increases. Therefore, in the present embodiment, in order to suppress the pressure loss of the compressed air Acom due to the nozzle holder 39, the nozzle holder 39 is arranged in a region where the cross-sectional area of the mixing space Sm is larger than the cross-sectional area of the upstream-side reduced-area portion 33 Deu.

[0043] The protrusion portion 37 of the present embodiment is not provided on a radially outer side with respect to the space center axis Ab from the large-diameter portion 35a. For this reason, in the present embodiment, it is possible to suppress a pressure loss of the compressed air Acom due to a collision of the compressed air Acom flowing along the large-diameter portion 35a of the nozzle main body 35 with the upstream end 37u of the protrusion portion 37. [Modification example]

[0044] In the embodiment described above, the maximum protrusion amount pmax of the protrusion portion 37 is equal to or less than 20% of the minimum distance dmin from the outer peripheral surface 36 of the small diameter portion 35c of the nozzle main body 35 to the inner peripheral surface 32 of the mixing tube 31. However, depending on the flow rate of the compressed air Acom flowing within the mixing space Sm in the extending direction De, the maximum protrusion amount pmax of the protrusion portion 37 may be greater than 20% of the minimum distance dmin from the outer peripheral surface 36 of the small diameter portion 35c of the nozzle main body 35 to the inner peripheral surface 32 of the mixing tube 31, and may be equal to or less than half of the minimum distance dmin.

[0045] In the above-described embodiment, the protrusion portion 37 is formed in a predetermined range from the end on the downstream side Ded of the nozzle main body 35 to the upstream side Deu. As shown in Fig. 8, however, the protruding portion 37a may be formed in a predetermined range from a position on the upstream side Deu with respect to the end on the downstream side Ded of the nozzle main body 35 toward the upstream side Deu.

[0046] In the above-described embodiment, the protruding portion 37 is not formed in the region including the upstream-side end Deu of the nozzle main body 35. However, the protruding portion may be formed in a region including the upstream-side end Deu of the nozzle main body 35.

[0047] In the above-described embodiment, a projection portion 37 is formed along a virtual line having a spiral shape around the spatial center axis Ab. As shown in Fig. 9, however, a plurality of protrusion portions 37b and 37c may be formed along a virtual line having a spiral shape around the space center axis Ab.

[0048] In the embodiment described above, the entire nozzle main body 35 is accommodated in the mixing space Sm. As shown in Fig. However, as shown in FIG. 10, one end of the nozzle main body 35 on the upstream side Deu may protrude from one end of the mixing space Sm on the upstream side Deu to the upstream side Deu. Even in this case, as described above, the protruding portion 37 may be formed in a region including the upstream side Deu end of the nozzle main body 35. That is, a part of the protruding portion 37 may be formed outside the mixing space Sm.

[0049] The combustion chamber 20 in the above-described embodiment is a cluster combustor combustor in which a plurality of burners 30 are arranged in the circumferential direction and the radial direction with respect to the combustion chamber axis Ac. However, the burner structure of the present disclosure can be applied to a premixed burner in a normal combustion chamber in which a plurality of premixed burners are not arranged in the radial direction with respect to the combustion chamber axis Ac.

[0050] Furthermore, the present disclosure is not limited to the above-described embodiment and modification example. Various additions, modifications, replacements, partial deletions, and the like may be made without departing from the conceptual idea and gist of the present invention, which are derived from the contents defined in the claims and their equivalents. [Supplementary note]

[0051] For example, the burner in the embodiment described above is to be understood as follows. (1) A burner according to a first aspect comprises: a mixing tube 31 extending in a predetermined extension direction De and in which a mixing space Sm for mixing air Acom and fuel F is formed; and a fuel nozzle 34 extending in the extension direction De and at least a part of which is disposed in the mixing space Sm. The mixing tube 31 has an air inlet 31i through which the air Acom can flow into the mixing space Sm, and an exhaust port 31o through which a premixed gas Gpm in which the air Acom and the fuel F are mixed can be exhausted from the mixing space Sm. The exhaust port 31o is formed at one end of the mixing tube 31 on a downstream side Ded between an upstream side Deu, which is one side in the extension direction De, and the downstream side Ded, which is the other side of the extension direction De.The fuel nozzle 34 includes a nozzle main body 35 extending in the extension direction De, and protrusion portions 37, 37a, 37b, and 37c protruding from an outer peripheral surface 36 of the nozzle main body 35 and separated from an inner peripheral surface 32 of the mixing tube 31. The nozzle main body 35 includes a fuel discharge port 35o capable of discharging the fuel F into the mixing space Sm from a position located on the downstream side Ded of the air inlet 31i and on the upstream side Deu of the discharge port 31o. The protrusion portions 37, 37a, 37b, and 37c gradually extend toward the downstream side Ded as the protrusion portions 37, 37a, 37b, and 37c extend in a circumferential direction with respect to the nozzle main body 35, and an entire portion of the protrusion portions 37, 37a, 37b, and 37c is formed in a spiral shape around the nozzle main body 35.

[0052] In the present aspect, the swirl flow Fs of the air Acom that has flowed into the mixing space Sm can be formed by the protrusion portions 37, 37a, 37b, and 37c in the region around the vicinity of the nozzle main body 35 in the virtual plane perpendicular to the extending direction De, which is a region where the protrusion portions 37, 37a, 37b, and 37c exist in the extending direction De, and a region on the downstream side Ded of the protrusion portions 37, 37a, 37b, and 37c. Moreover, since the protrusion portions 37, 37a, 37b and 37c are separated from the inner peripheral surface 32 of the mixing tube 31, when the air Acom overflows the outer peripheral surface 38 of the protrusion portions 37, 37a, 37b and 37c, a small turbulence Ft1 of the air Acom is generated on the downstream side Ded in the air overflow direction on the outer peripheral surface 38.Furthermore, a small turbulence Ft1 of the air Acom also occurs on the downstream side Ded of the downstream end 37d of the protruding portions 37, 37a, 37b, and 37c. As described above, in the present aspect, the swirl flow Fs as the main air flow is formed in the downstream main body surrounding region Ra, which is a region on the downstream side Ded of the protruding portions 37, 37a, 37b, and 37c and a region near the nozzle main body 35 in the virtual plane perpendicular to the extending direction De, and small turbulences Ft1 and Ft2 are formed. Therefore, in the present aspect, in the downstream main body surrounding region Ra, the mixing of the air Acom and the fuel F jetted from the nozzle main body 35 is promoted.Therefore, in the present aspect, the generation of a region having a high fuel-air ratio (fuel amount / air amount) in the mixing space Sm can be suppressed, and the generation of NOx can be suppressed.

[0053] Furthermore, in the present aspect, since the protrusion portions 37, 37a, 37b, and 37c are separated from the inner peripheral surface 32 of the mixing tube 31, the influence of the swirl flow Fs in the region Rb near the inner peripheral surface of the mixing tube 31, which is the region on the downstream side Ded of the protrusion portions 37, 37a, 37b, and 37c, in the virtual plane perpendicular to the extending direction De can be suppressed. Therefore, in the present aspect, the mixing of the air Acom and the fuel F in the region Rb near the inner peripheral surface is suppressed. Therefore, in the present aspect, the fuel-air ratio (fuel amount / air amount) in the region Rb near the inner peripheral surface where the gas flow rate is low can be kept low, and backfiring, which is a flame transmitted into the mixing space Sm, can be suppressed.

[0054] (2) In a burner according to a second aspect, in the burner 30 according to the first aspect, a maximum protrusion amount pmax of the protrusion portions 37, 37a, 37b, and 37c from the outer peripheral surfaces 36, 38 of the nozzle main body 35 is equal to or less than half of a minimum distance dmin from a portion, which is a part of the outer peripheral surface 36 of the nozzle main body 35 and in which the protrusion portions 37, 37a, 37b, and 37c are present in the extending direction De, to the inner peripheral surface 32 of the mixing tube 31.

[0055] In the present aspect, it is possible to reduce the area of the region where the circumferential component flow rate of the swirl flow Fs is equal to or higher than the first flow rate in the above-described downstream main body surrounding region Ra in the virtual plane perpendicular to the extending direction De. On the other hand, in the present aspect, it is possible to increase the area of the region where the circumferential component flow rate of the swirl flow Fs is equal to or lower than the second flow rate, which is slower than the first flow rate, in the above-described near-inner peripheral surface region Rb in the virtual plane perpendicular to the extending direction De.Therefore, in the present aspect, the mixing of the fuel F with the air Acom flowing along the inner peripheral surface 32 of the mixing tube 31 can be suppressed in the region Rb near the inner peripheral surface where the gas flow rate is slow, and backfiring, which is a flame transmitted into the mixing space Sm, can be suppressed.

[0056] (3) In a burner according to a third aspect, in the burner 30 according to the first aspect or the second aspect, a maximum protrusion amount pmax of the protrusion portions 37, 37a, 37b, and 37c from the outer peripheral surfaces 36, 38 of the nozzle main body 35 is equal to or less than 20% of a minimum distance dmin from a portion, which is a part of the outer peripheral surfaces 36, 38 of the nozzle main body 35 and in which the protrusion portions 37, 37a, 37b, and 37c are present in the extending direction De, to the inner peripheral surface 32 of the mixing tube 31.

[0057] In the present aspect, it is possible to reduce the area of the region where the circumferential component flow rate of the swirl flow Fs is equal to or higher than the first flow rate in the above-described downstream main body surrounding region Ra in the virtual plane perpendicular to the extending direction De. On the other hand, in the present aspect, it is possible to increase the area of the region where the circumferential component flow rate of the swirl flow Fs is equal to or lower than the second flow rate, which is slower than the first flow rate, in the above-described near-inner peripheral surface region Rb in the virtual plane perpendicular to the extending direction De.Therefore, in the present aspect, the mixing of the fuel F with the air Acom flowing along the inner peripheral surface 32 of the mixing tube 31 can be suppressed in the region Rb near the inner peripheral surface where the gas flow rate is slow, and backfiring, which is a flame transmitted into the mixing space Sm, can be suppressed.

[0058] (4) In a burner according to a fourth aspect, in the burner 30 according to any one of the first to third aspects, the fuel discharge port 35o is formed at an end of the nozzle main body 35 on the downstream side Ded. The protruding portions 37, 37c are formed in a predetermined range on an outer peripheral surface 36 of the nozzle main body 35 from the end of the nozzle main body 35 on the downstream side Ded to the upstream side Deu of the nozzle main body 35.

[0059] In the present aspect, the protrusion portions 37, 37c are formed in a region including the downstream side end Ded of the nozzle main body 35. Therefore, in the present aspect, the influence of the swirl flow Fs and the turbulence Ft1 and Ft2 of the air Acom formed by the protrusion portions 37, 37c can be exerted more strongly on the fuel jetted from the downstream side end Ded of the nozzle main body 35 than in a case where the downstream end 37d of the protrusion portions 37, 37c is formed on the upstream side Deu from the downstream side end Ded of the nozzle main body 35. Therefore, in the present aspect, the air Acom and the fuel F can be effectively mixed in the above-described downstream main body surrounding region Ra.

[0060] (5) In a burner according to a fifth aspect, in the burner 30 according to any one of the first to fourth aspects, the protrusion portions 37, 37a, 37b and 37c are formed only in the mixing space Sm.

[0061] (6) In a burner according to a sixth aspect, in the burner 30 according to the fifth aspect, the mixing space Sm has a reduced area portion 33 whose cross-sectional area perpendicular to the extension direction De gradually decreases toward the downstream side Ded. The reduced area portion 33 is formed in a region where the protrusion portions 37, 37a, 37b, and 37c are present in the extension direction De.

[0062] In the present aspect, in the area along the inner peripheral surface 32 of the mixing tube 31, in the reduced-area portion 33, an airflow having a directional component toward the center of the mixing tube 31 is generated. Due to this airflow, the swirl flow Fs formed by the protrusion portions 37, 37a, 37b, and 37c is pushed toward the center side of the mixing tube 31. For this reason, in the present aspect, in the above-described downstream main body surrounding area Ra in the virtual plane perpendicular to the extending direction De, a region where the circumferential component flow rate Vc of the swirl flow Fs is equal to or higher than the first flow rate is located near the center side of the mixing tube 31. As a result, in the present aspect, it is possible to reduce the area of the region where the circumferential component flow rate Vc is equal to or higher than the first flow rate.Furthermore, the cross-sectional area of the mixing space Sm on the downstream side Ded of the reduced area portion 33 is smaller than the cross-sectional area of the mixing space Sm on the upstream side Deu of the reduced area portion 33. Therefore, in the present aspect, the gas flow rate in the mixing space Sm on the downstream side Ded of the reduced area portion 33 in the extension direction De is higher than the gas flow rate in a case where the reduced area portion 33 is not provided. Therefore, in the present aspect, backfiring, which is the flame transmitted into the mixing space Sm, can be effectively suppressed.

[0063] (7) In a burner according to a seventh aspect, the burner 30 according to the sixth aspect further includes the nozzle holder 39 configured to support the fuel nozzle 34 within the mixing space Sm. The nozzle holder 39 connects the outer peripheral surfaces 36, 38 of the nozzle main body 35 and the inner peripheral surface 32 of the mixing tube 31 at a position on the upstream side Deu of a region where the reduced area portion 33 is formed in the extending direction De.

[0064] The air Acom that has flowed into the mixing space Sm undergoes a pressure loss through the nozzle holder 39. Moreover, when a part of the mixing space Sm is occupied by the nozzle holder 39, a region where the air Acom flows in the mixing space Sm becomes narrow, the flow rate of the air Acom increases, and the pressure loss of the air Acom increases due to the nozzle holder 39. Therefore, in the present aspect, in order to suppress the pressure loss of the air Acom caused by the nozzle holder 39, the nozzle holder 39 is arranged in a region where the cross-sectional area of the mixing space Sm on the upstream side Deu is larger than in the reduced area portion 33.

[0065] (8) In a burner according to an eighth aspect, in the burner 30 according to any one of the first to seventh aspects, the mixing space Sm is a space having a cylindrical shape. The nozzle main body 35 is arranged on a space center axis Ab of the mixing space Sm.

[0066] (9) In a burner according to a ninth aspect, in the burner 30 according to the eighth aspect, the nozzle main body 35 includes a large-diameter portion 35a having a cylindrical shape around the space center axis Ab, a reduced-diameter portion 35b having a conical shape around the space center axis Ab, and a small-diameter portion 35c having a cylindrical shape around the space center axis Ab. The reduced-diameter portion 35b is connected to one end of the large-diameter portion 35a on the downstream side Ded, and an outer diameter of the reduced-diameter portion 35b gradually decreases toward the downstream side Ded. The small-diameter portion 35c is connected to one end of the reduced-diameter portion 35b on the downstream side Ded.An upstream end 37u of the protrusion portions 37, 37a, 37b, and 37c is located at a boundary between the large-diameter portion 35a and the reduced-diameter portion 35b in the extension direction De. A downstream end 37d of the protrusion portions 37, 37a, 37b, and 37c is located at an end of the small-diameter portion 35c on the downstream side Ded. A distance from the spatial center axis Ab to an outer peripheral surface 38 of the protrusion portions 37, 37a, 37b, and 37c is equal to or smaller than an outer diameter of the large-diameter portion 35a at any position in the extension direction De.

[0067] The protrusion portions 37, 37a, 37b, and 37c according to the present aspect are not located on the radially outer side relative to the large-diameter portion 35a with respect to the space center axis Ab. For this reason, in the present aspect, it is possible to suppress a pressure loss of the air Acom due to a collision of the air Acom flowing along the large-diameter portion 35a of the nozzle main body 35 with the upstream end 37u of the protrusion portions 37, 37a, 37b, and 37c.

[0068] The combustion chamber in the above embodiment is understood, for example, as follows.

[0069] (10) A combustion chamber according to a tenth aspect comprises: the burner 30 according to any one of the first to ninth aspects; and a pipe 21 in which the premixed gas Gpm discharged from the discharge port 31o of the burner 30 can be combusted.

[0070] For example, the cluster burner combustion chamber in the above embodiment is understood as follows. (11) A cluster burner combustion chamber according to an eleventh aspect comprises: a plurality of burners 30 according to any one of the first to ninth aspects; and a tube 21 in which the premixed gas Gpm discharged from the discharge port 31o of each of the plurality of burners 30 can be combusted. The extension direction De of each of the plurality of burners 30 is the same direction as that of the others. Positions of the discharge ports 31o of the plurality of burners 30 in the extension direction De are aligned with each other.

[0071] For example, the gas turbine in the embodiment described above is to be understood as follows. (12) A gas turbine according to a twelfth aspect comprises: the combustor according to the tenth aspect; a compressor 10 configured to compress air A to generate compressed air Acom and supply the compressed air Acom to the burner 30; and a turbine 15 configured to be driven by a combustion gas G generated by the combustion of the premixed gas Gpm in the tube 21 of the combustor. (13) A gas turbine according to a thirteenth aspect comprises: the cluster burner combustor according to the eleventh aspect; a compressor 10 configured to compress air A to generate compressed air Acom and supply the compressed air Acom to the plurality of burners 30; and a turbine 15 configured to be driven by a combustion gas G generated by the combustion of the premixed gas Gpm in the tube of the cluster burner combustor. Industrial applicability

[0072] In one aspect of the present disclosure, it is possible to suppress the generation of NOx while suppressing backfiring. List of reference symbols 1 gas turbine rotor 2 gas turbine casings 4 intermediate housings 10 Compressor 11 Compressor rotor 12 Compressor housing 15 turbines 16 Turbine rotor 17 Turbine housing 20 combustion chamber 21 pipe 22 Opening on upstream side 25 burner support frames 26 Fuel flow path 26m main flow path 26b Branch flow path 27 Air flow path 30 burners 31 Mixing tube 31i air intake 31o discharge connection 31p Fuel flow path 32 inner circumferential surface 33 Section with reduced area 34 Fuel nozzle 35 Nozzle main body 35a Large diameter section 35b Section with reduced diameter 35c small diameter section 35o fuel discharge connection 35p Fuel flow path 36 outer peripheral surface 37, 37a, 37b, 37c projection section 37u upstream end 37d downstream end 38 outer peripheral surface 39 nozzle holder 39p Fuel flow path A Air Acom compressed air F Fuel G Combustion gas Gpm premixed gas Ar rotor axis Ac combustion chamber axis From the room center axis Since rotor axis direction Dau axial upstream side The axial downstream side The direction of extension Deu upstream side The downstream side Sc combustion chamber Sm mixing room Ra downstream main body surrounding area Rb area near inner peripheral surface Fs swirl current Ft1, Ft2 turbulence QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2022-168852

[0002] JP 2015-014400

[0007]

Claims

[1] Burner, comprising: a mixing tube extending in a predetermined direction of extension and in which a mixing space for mixing air and fuel is formed; and a fuel nozzle extending in the direction of extension and at least a part of which is arranged in the mixing chamber, wherein the mixing tube has an air inlet through which the air can flow into the mixing chamber, and an exhaust port through which a premixed gas in which the air and the fuel are mixed can be expelled from the mixing chamber, the discharge port is formed at one end of the mixing tube on a downstream side of an upstream side, which is one side in the extending direction, and the downstream side, which is the other side of the extending direction, the fuel nozzle has a nozzle main body extending in the extension direction and a protruding portion protruding from an outer peripheral surface of the nozzle main body and separated from an inner peripheral surface of the mixing tube, the nozzle main body has a fuel discharge port capable of discharging the fuel into the mixing chamber from a position located on the downstream side of the air inlet and on the upstream side of the discharge port, and the protrusion portion extends gradually to the downstream side as the protrusion portion extends in a circumferential direction with respect to the nozzle main body, and an entire portion of the protrusion portion is formed in a spiral shape around the nozzle main body. [2] The burner according to claim 1, wherein a maximum protrusion amount of the protruding portion from the outer peripheral surface of the nozzle main body is equal to or less than one half of a minimum distance from a portion, which is a part of the outer peripheral surface of the nozzle main body and in which the protruding portion is present in the extending direction, to the inner peripheral surface of the mixing tube. [3] The burner according to claim 1, wherein a maximum protrusion amount of the protrusion portion from the outer peripheral surface of the nozzle main body is equal to or less than 20% of a minimum distance from a portion, which is a part of the outer peripheral surface of the nozzle main body and in which the protrusion portion is present in the extending direction, to the inner peripheral surface of the mixing tube. [4] Burner according to one of claims 1 to 3, wherein the fuel discharge port is formed at one end of the nozzle main body on the downstream side, and the protrusion portion is formed in a predetermined range on an outer peripheral surface of the nozzle main body from the end of the nozzle main body on the downstream side to the upstream side of the nozzle main body. [5] A burner according to claim 4, wherein the projection portion is formed only in the mixing space. [6] Burner according to claim 5, wherein the mixing space has a reduced area portion of which a cross-sectional area perpendicular to the extension direction gradually decreases toward the downstream side, and the reduced area portion is formed in a region where the protrusion portion is present in the extending direction. [7] Burner according to claim 6, further comprising: a nozzle holder configured to support the fuel nozzle within the mixing chamber, wherein the nozzle holder connects the outer peripheral surface of the nozzle main body and the inner peripheral surface of the mixing tube at a position on the upstream side of a region where the reduced area portion is formed in the extending direction. [8] Burner according to one of claims 1 to 3, wherein the mixing chamber is a chamber with a cylindrical shape, and the nozzle main body is arranged on a central axis of the mixing chamber. [9] Burner according to claim 8, wherein the nozzle main body has a large diameter portion having a cylindrical shape around the space central axis, a reduced diameter portion having a conical shape around the space central axis, and a small diameter portion having a cylindrical shape around the space central axis, the reduced diameter section is connected to one end of the large diameter section on the downstream side, and an outer diameter of the reduced diameter section gradually decreases toward the downstream side, the small diameter section is connected to one end of the reduced diameter section on the downstream side, an upstream end of the projection portion is located at a boundary between the large diameter portion and the reduced diameter portion in the extending direction, a downstream end of the projection portion is located at an end of the small diameter portion on the downstream side, and a distance from the spatial center axis to an outer peripheral surface of the protrusion portion at any position in the extending direction is equal to or smaller than an outer diameter of the large diameter portion. [10] Combustion chamber comprising: the burner according to one of claims 1 to 3; and a tube in which the premixed gas expelled from the burner's exhaust port can be combusted. [11] Cluster burner combustion chamber, comprising: several of the burners according to one of claims 1 to 3; and a pipe in which the premixed gas discharged from the discharge port of each of the plurality of burners can be burned, wherein the extension direction of each of the plurality of burners has the same direction as that of the others, and Positions of the discharge ports of the plurality of burners are aligned with each other in the extension direction. [12] Gas turbine, comprising: the combustion chamber according to claim 10; a compressor configured to compress air to produce compressed air and supply the compressed air to the burner; and a turbine configured to be driven by a combustion gas produced by the combustion of the premixed gas in the tube of the combustion chamber. [13] Gas turbine, comprising: the cluster burner combustion chamber according to claim 11; a compressor configured to compress air to produce compressed air and supply the compressed air to the plurality of burners; and a turbine configured to be driven by a combustion gas produced by the combustion of the premixed gas in the tube of the cluster burner combustor.

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