JP2024090698A - Burner and combustor having the same - Google Patents

Abstract

To prevent occurrence of backfire and suppress generation of nitrogen compound NOx during combustion.SOLUTION: A burner burns a mixture of air and fuel in a combustion chamber. The burner includes: a first supply pipe having a flow passage for supplying the air toward the combustion chamber; a second supply pipe inserted in the flow passage of the first supply pipe to supply the fuel; a restriction formation part that is provided at a tip part of the second supply pipe and forms a restriction part for restricting the flow passage with respect to an inner wall surface of the first supply pipe; a body part having an ejection hole for ejecting the fuel toward the upstream side of the flow passage; and a tubular part for sending the fuel to be supplied by the second supply pipe to the body part. The body part includes: a fuel ejection part disposed in the vicinity of the combustion chamber; and a diffusion part that is provided at a connecting portion between the first supply pipe and the combustion chamber and diffuses the air flowing from the flow passage into the combustion chamber in the combustion chamber.SELECTED DRAWING: Figure 2

Description

The present invention relates to a burner used in a gas turbine or the like, and a combustor having the burner.

When burning gases with a fast combustion speed, such as hydrogen, in a gas turbine combustor, the combustion range is wide and the combustion temperature is high, resulting in the generation of large amounts of the nitrogen compound NOx. As a countermeasure, extremely high denitrification effects can be achieved by injecting steam or water into the combustor, but this generally involves using steam from a waste heat boiler that utilizes the exhaust heat of the gas turbine, which reduces the overall thermal efficiency of the gas turbine. On the other hand, the dry low NOx combustion method can maintain the overall thermal efficiency.

JP 2021-196073 A

However, while fuels with a relatively slow burning speed, such as natural gas, can achieve dry low NOx combustion with lean premixing, gases such as hydrogen have a fast burning speed and there is a risk of flashback when using lean premixing.

The present invention was invented to solve the problems described above, and aims to provide a burner and a combustor having the burner that suppresses the generation of nitrogen compounds (NOx) during combustion and suppresses the occurrence of flashbacks.

In order to solve the above-mentioned problems, one aspect of the burner of the present invention is a burner that burns a mixture of fuel and air in a combustion chamber, and is characterized in that it includes a first supply pipe having a flow path that supplies air toward the combustion chamber, a second supply pipe that is inserted into the flow path of the first supply pipe and supplies fuel, a constriction forming section that is provided at the tip of the second supply pipe and forms a constriction section that constricts the flow path between the inner wall surface of the first supply pipe, a main body section having an ejection hole that ejects fuel toward the upstream side of the flow path, and a tubular section that sends the fuel supplied by the second supply pipe to the main body section, the main body section having a fuel ejection section that is located near the combustion chamber, and a diffusion section that is provided at the connection between the first supply pipe and the combustion chamber and that diffuses the air flowing into the combustion chamber from the flow path within the combustion chamber.

In addition, when the inner diameter of the first supply pipe is D1, the outer diameter of the constriction forming portion is D2, and the outer diameter of the tubular portion is D3, the ratio of the outer diameter D2 of the constriction forming portion to the inner diameter D1 of the first supply pipe is set to 0.75 to 0.9, and the ratio of the outer diameter D3 of the tubular portion to the inner diameter D1 of the first supply pipe is set to 0.05 to 0.2.

In addition, when the inner diameter of the first supply pipe is D1 and the distance from the main body to the combustion chamber is H1, the ratio of the inner diameter D1 of the first supply pipe to the distance H1 from the main body to the combustion chamber is set to 0.15 to 0.45.

The diffusion section is an arc-shaped curved surface provided at the connection between the first supply pipe and the combustion chamber, and when the inner diameter of the first supply pipe is D1 and the radius of the diffusion section is R1, the ratio of the inner diameter D1 of the first supply pipe to the radius R1 of the diffusion section is set to 0.2 or more.

The combustor of one aspect of the present invention is characterized by comprising the burner described above, an inner cylinder having an internal combustion chamber for burning the mixture sent from the burner, and an outer cylinder in which the inner cylinder is housed and having a space between the inner cylinder and the outer cylinder for supplying air to the premixing tube.

In addition, a combustion method according to one aspect of the present invention includes the steps of: generating a first vortex inside a first supply pipe constituting a burner by air flowing into the first supply pipe; ejecting fuel supplied by a second supply pipe inserted into the first supply pipe toward the upstream side of the first supply pipe using a nozzle provided at the tip of the second supply pipe; mixing the air flowing into the first supply pipe and the fuel ejected from the nozzle by the first vortex so that the fuel is in a fuel-rich state; and The method includes the steps of: performing primary combustion of the mixture of air and the fuel inside the combustion chamber; diffusing the air sent from the first supply pipe to the combustion chamber inside the combustion chamber by a diffusion section provided at the connection between the first supply pipe and the combustion chamber to generate a second vortex inside the combustion chamber; mixing the fuel that is unburned by the primary combustion with the air sent to the combustion chamber by the second vortex; and performing secondary combustion of the mixture of the fuel and the air mixed by the second vortex inside the combustion chamber.

This invention makes it possible to prevent flashbacks and at the same time suppress the generation of nitrogen compounds (NOx) during combustion.

FIG. 1 illustrates one configuration of a combustor. FIG. 2 is a cross-sectional view showing the configuration of the burner. FIG. 3 is a diagram showing the air flow through the burner and the combustion chamber. FIG. 4 is a diagram showing the temperature distribution in the combustion chamber. FIG. 5 is a diagram showing the distribution of nitrogen compounds (NOx) in the combustion chamber. FIG. 6 is a diagram showing another embodiment of the throttle forming portion. FIG. 7 shows another embodiment of the nozzle.

An embodiment of the combustor of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing the schematic configuration of a combustor 10. The combustor 10, which will be described in detail later, generates a vortex with the incoming air, mixes the fuel and air so that the fuel is in an excess state, and burns the mixture in the combustion chamber for the primary combustion. The combustor 10 also generates a vortex in the combustion chamber with the air that flows into the combustion chamber, mixes the unburned fuel and air in the primary combustion, and burns the mixture in the secondary combustion. This configuration makes it possible to suppress the occurrence of flashback of the hydrogen fuel. Note that, in the following, a gas with a high combustion speed such as hydrogen is given as an example of the fuel, but it is also possible to use, for example, natural gas as the fuel.

The combustor 10 is provided, for example, in a gas turbine (not shown) and rotates the turbine (not shown) by sending the combustion gas generated by combustion to the turbine. As shown in FIG. 1, the combustor 10 has an inner cylinder 20, an outer cylinder 30, and a burner 40. Note that the burner that ignites the combustion chamber 21 when combustion begins is sometimes called a pilot burner, and the burner 40 that sends the fuel and air required for combustion to the combustion chamber 21 is sometimes called a main burner.

The inner cylinder 20 has a combustion chamber 21 inside that burns the mixture generated by the burner 40 using a flame ignited by a pilot burner (not shown) or by direct ignition from a plug. The inner cylinder 20 is a tubular member, for example, cylindrical, whose upper end in the direction of the central axis L is closed by a canopy 22. The canopy 22 has a shape such that, for example, its center portion 23 protrudes upward relative to the outer peripheral edge portion 24.

Although not shown, a pilot burner is installed in the center 23 of the canopy 22. In addition, in the center 23 of the canopy 22, multiple burners 40 are provided at predetermined angular intervals centered on the central axis (L) direction of the inner cylinder 20 so as to surround the pilot burner in a plan view of the combustor 10. In addition, multiple burners 40 are also provided on the outer peripheral edge portion 24 of the canopy 22 at predetermined angular intervals centered on the central axis (L) direction of the inner cylinder 20. The configuration of the burners 40 will be described later.

The outer cylinder 30, like the inner cylinder 20, is a cylindrical member with a closed upper end in the direction of the central axis (L). The outer cylinder 30 is held in a state in which the inner cylinder 20 is housed. The outer cylinder 30 houses the inner cylinder 20 in a state in which the inner cylinder 20 is coaxial with the outer cylinder 30. When the inner cylinder 20 is housed inside the outer cylinder 30, a space 31 is formed between the housed inner cylinder 20. The space 31 functions as a supply space (hereinafter referred to as the supply space 31) that flows air supplied from the lower end of the outer cylinder 30 in the direction of the central axis (L) to the inside of the outer cylinder 30 toward the pilot burner provided in the canopy 22 and the air supply pipe 41 of the burner 40.

Although not shown in the figure, the pilot burner ejects fuel and air toward the combustion chamber 21 of the inner cylinder 20, diffusing and mixing the fuel and air inside the combustion chamber 21, and ignites the diffused and mixed fuel with an ignition rod to burn. This combustion burns the air-fuel mixture that flows from the burner 40 into the combustion chamber 21.

The burner 40 mixes fuel and air to generate a mixture, and supplies the mixture to the combustion chamber 21. As shown in FIG. 2, the burner 40 is composed of an air supply pipe 41 and a fuel supply pipe 42, which will be described in detail later. The air supply pipe 41 of the burner 40 corresponds to the first supply pipe described in the claims, and the fuel supply pipe 42 corresponds to the second supply pipe described in the claims.

The air supply pipes 41 are provided at the center and outer periphery of the canopy 22 of the inner cylinder 20 so that the direction of their respective central axes (L2) is horizontal to the direction of the central axis (L) of the inner cylinder 20. The air supply pipe 41 has an inlet 41a at its upper end through which air flows in, and a flow path 51 that supplies the air flowing in from the inlet 41a to the combustion chamber 21.

A diffusion section 56 is provided at the connection between the lower end of the air supply pipe 41 and the canopy 22 of the inner cylinder 20. The diffusion section 56 is, for example, an arc-shaped curved surface. By providing the diffusion section 56, when air flows from the flow path 51 of the air supply pipe 41 into the combustion chamber 21, the air flows along the diffusion section 56 and is diffused when it enters the combustion chamber 21.

The fuel supply pipe 42 supplies fuel to the flow path 51 of the air supply pipe 41. The fuel supply pipe 42 extends from the upper end surface of the outer cylinder 30 toward the lid 22 of the inner cylinder 20 (see FIG. 1) and is held in a state inserted into each of the air supply pipes 41 provided on the lid 22 of the inner cylinder 20.

The fuel supply pipe 42 has a throttle forming portion 42a at the tip of the fuel supply pipe 42. The throttle forming portion 42a protrudes from the outer circumferential surface of the fuel supply pipe 42 in the radial direction of the fuel supply pipe 42. The throttle forming portion 42a is, for example, a cone shape with an outer diameter enlarged toward the tip of the fuel supply pipe 42. For example, when the fuel supply pipe 42 is inserted and held inside the air supply pipe 41, the throttle forming portion 42a forms a throttle portion 52 between the inner wall surface 41b of the air supply pipe 41 on the downstream side of the air supply pipe 41. By providing the throttle portion 52 inside the air supply pipe 41, the flow speed of the air before and after passing through the throttle portion 52 changes, and a part of the air that has passed through the throttle portion 52 forms a vortex 71 downstream of the throttle portion 52. It is preferable that the flow speed of the air passing through the throttle portion 52 is set to, for example, 80 to 100 m/s. As a result, a portion of the air that has passed through the throttling section 52 can form a vortex 71 downstream of the throttling section 52 that is strong enough to mix the fuel and air in an excess of fuel. Here, the vortex 71 corresponds to the first vortex described in the claims.

A nozzle 53 is provided at the tip of the fuel supply pipe 42. The nozzle 53 corresponds to the fuel ejection portion described in the claims. The nozzle 53 extends from the tip surface 42b of the fuel supply pipe 42 toward the combustion chamber 21. The nozzle 53 has a main body portion 61 and a tubular portion 62. The main body portion 61 has a plurality of ejection holes 63 that eject fuel toward the tip surface 42b side of the fuel supply pipe 42. The multiple ejection holes 63 are provided at predetermined angular intervals centered on the central axis (L2) direction.

(Explanation of the flow from mixing of air and fuel in the burner 40 to combustion)
Next, the flow from mixing of air and fuel in the burner 40 to combustion will be described mainly with reference to Fig. 3. As the gas turbine is driven, air and fuel are supplied to the combustor 10. The air supplied to the combustor 10 flows into a supply space 31 provided between the inner cylinder 20 and the outer cylinder 30 of the combustor 10. The air that has flowed into the supply space 31 flows into the air supply pipe 41 from an inlet 41a provided at the upper end of the air supply pipe 41. The air that has flowed into the air supply pipe 41 flows through a flow path 51 between the air supply pipe 41 and the fuel supply pipe 42 toward the combustion chamber 21.

As described above, the fuel supply pipe 42 has a constriction forming portion 42a at its tip. Therefore, in the flow path 51 between the air supply pipe 41 and the fuel supply pipe 42, a constriction portion 52 is formed by the inner wall surface of the air supply pipe 41 and the constriction forming portion 42a of the fuel supply pipe 42.

When air flowing toward the combustion chamber 21 passes through the throttling section 52, the flow speed of the air changes. For example, air flowing near the inner wall surface 41b of the air supply pipe 41 continues to flow near the inner wall surface 41b of the air supply pipe 41. On the other hand, when air flowing along the throttling section 42a of the fuel supply pipe 42 passes through the throttling section 52, it forms a vortex 71 toward the central axis L2 direction of the air supply pipe 41 downstream of the throttling section 42a of the fuel supply pipe 42.

On the other hand, the fuel (gas with a high combustion speed such as hydrogen) supplied to the combustor 10 flows through the fuel supply pipe 42 and then reaches the nozzle 53. The fuel that reaches the nozzle 53 is then ejected from the ejection hole 63 provided in the nozzle 53 toward the tip surface 42b of the fuel supply pipe 42, i.e., toward the upstream side of the air supply pipe 41. As described above, inside the air supply pipe 41, a vortex 71 is formed downstream of the throttle forming portion 42a of the fuel supply pipe 42 by the air passing through the throttle portion 52. Therefore, a portion of the fuel ejected toward the tip surface 42b of the throttle forming portion 42a of the fuel supply pipe 42 is rapidly mixed (premixed) with the air by the vortex 71. The air that passes through the throttle portion 52 to form the vortex 71 and the fuel ejected toward the vortex 71 are mixed in a state where the equivalence ratio of fuel to air is 1 or more, i.e., in a state of excess fuel. In addition, when an air-fuel mixture is mixed in an excess fuel state, some of the mixture is completely mixed (premixed), but not all of the injected fuel is completely mixed and is diffused and mixed with the air as it flows toward the combustion chamber 21.

When the gas turbine is driven, it is ignited by the pilot burner. Therefore, the mixture supplied from the burner 40 to the combustion chamber 21 is burned in the area 76 near the diffusion section 56 (primary combustion). That is, in the primary combustion, the mixture generated by premixing air and fuel inside the burner 40 (premixed combustion) and the mixture generated by diffusing the air and fuel flowing to the combustion chamber 21 (diffusion combustion) are simultaneously burned. As described above, the mixture generated by premixing air and fuel inside the burner 40 is in a state of excess fuel. Therefore, in the premixed combustion, which is part of the primary combustion, only the fuel corresponding to the air concentration contained in the mixture is burned, and the unburned fuel flows into the inside of the combustion chamber 21 together with the gas and steam generated by the primary combustion.

By the way, the air that has passed through the narrowing section 52 and flows along the inner wall surface 41b of the air supply pipe 41 is diffused inside the combustion chamber 21 when it flows into the combustion chamber 21. At this time, in the combustion chamber 21, the mixture of air and fuel mixed by the vortex 71 flows into the combustion chamber 21 and is burned inside the combustion chamber 21. Therefore, the air diffused from the flow path 51 of the air supply pipe 41 into the combustion chamber 21 diffuses inside the combustion chamber 21 and then flows toward the area 76 where the mixture undergoes primary combustion. As a result, a vortex 72 is generated inside the combustion chamber 21. The vortex 72 is, for example, larger than the inner diameter of the air supply pipe 41. The vortex 72 corresponds to the second vortex described in the claims. When the vortex 72 is formed by the inflow of air into the combustion chamber 21, the unburned fuel in the primary combustion is rapidly mixed with the air again by the vortex 72, together with the water vapor generated by the combustion of the mixture. This rapidly mixed mixture is burned by the flame generated by the primary combustion in region 77 below region 76 where the primary combustion takes place (secondary combustion). This secondary combustion burns the fuel that is unburned in the primary combustion. The gas generated by the secondary combustion flows downwards in the inner cylinder 20 (see FIG. 1) together with the gas generated by the primary combustion, and rotates a turbine (not shown).

In the region 76 where the primary combustion takes place, the temperature rises and the air contained in the mixture reacts chemically to produce the nitrogen compound NOx. However, because most of the air contained in the mixture is used to burn the fuel, the amount of nitrogen compound NOx produced by the chemical reaction of the air is suppressed.

In addition, in the secondary combustion, the temperature in the region 77 where the secondary combustion is performed rises due to the combustion of fuel, but the water vapor generated by the primary combustion vaporizes, preventing the temperature from rising excessively in the region 77 where the secondary combustion is performed. Therefore, in the secondary combustion, the air contained in the mixture is less likely to undergo chemical reactions, and the amount of nitrogen compound NOx produced is suppressed. Furthermore, the high-temperature combustion gas is diluted by being rapidly mixed with the air again by the vortex 72, and the process of generating thermal nitrogen compound NOx due to high temperature is stopped. For example, if the gas generated by the secondary combustion remains at a high temperature, thermal nitrogen compound NOx due to high temperature will continue to be generated. Therefore, the amount of nitrogen compound NOx generated throughout the entire combustion chamber 21 is suppressed.

(Regarding the outer diameter of the constriction forming portion 42a of the fuel supply pipe 42 and the outer diameter of the tubular portion 62 of the nozzle 53)
In the configuration of the burner 40 described above, air passing through the throttle portion 52 generates a vortex 71 downstream of the throttle portion 52, and the air and fuel are mixed, for example, such that the equivalence ratio of fuel to air is in excess of fuel, that is, the equivalence ratio is equal to or greater than 1. As shown in Fig. 2, it is preferable that the inner diameter D1 of the air supply pipe 41, the maximum outer diameter D2 of the throttle-forming portion 42a of the fuel supply pipe 42, and the outer diameter D3 of the tubular portion 62 of the nozzle 53 satisfy the following formulas (1) and (2).

D2/D1=0.75 to 0.9 (1)
D3/D1=0.05 to 0.2 (2)

In addition, in order to diffuse the air flowing into the combustion chamber 21 and to make the size of the vortex 72 generated by the air flowing into the region 76 where the mixture is burned at least one time the inner diameter of the air supply pipe 41, it is preferable that the radius R1 of the diffusion section 56 satisfies the following formula (3) relative to the inner diameter D1 of the air supply pipe 41.

R1/D1 ≧ 0.2 ... (3)

Furthermore, when combusting the mixture sent to the combustion chamber 21, in order to prevent combustion inside the burner 40, i.e., to prevent the occurrence of flashback, it is preferable that the distance H1 from the tip of the nozzle 53 to the combustion chamber 21 with respect to the inner diameter D1 of the air supply pipe 41 satisfies the following formula (4).

H1/D1 = 0.15 to 0.45... (4)

(experiment)
Finally, the temperature distribution in the combustion chamber 21 and the distribution of the nitrogen compound NOx generated when fuel is burned in the combustion chamber 21 in the combustor having the above configuration will be described. As shown in Fig. 4, it was found that when fuel is burned in the combustion chamber 21, the temperature becomes high in the region 76 where the primary combustion is performed and the region 77 where the secondary combustion is performed as shown in Fig. 3, but there are few regions where the temperature becomes high locally. In addition, as shown in Fig. 5, it was found that the concentration of the nitrogen compound NOx is high in the region 77 where the secondary combustion is performed inside the combustion chamber 21, but the concentration of the nitrogen compound NOx in the combustion chamber 21 is generally low. Therefore, it was found that the generation of the nitrogen compound NOx can be suppressed in the combustion in the combustion chamber 21 using the combustor 10 of the present invention.

In this embodiment, the fuel supply pipe 42 is provided with a throttle forming portion 42a to form a throttle portion 52 between the inner wall surface 41b of the air supply pipe 41, but the shape of the throttle forming portion 42a is not limited to the conical throttle forming portion 42a as shown in FIG. 2. For example, as shown in FIG. 6, a disk-shaped flange portion 81 having an outer diameter larger than the outer diameter of the fuel supply pipe 80 can be provided at the tip of the fuel supply pipe 80, and this flange portion 81 can function as the throttle forming portion.

In addition, in the embodiment of the present invention, the detailed description of the shape of the nozzle 53 provided at the tip of the fuel supply pipe 42 is omitted, but as long as the fuel can be sprayed toward the tip surface 42b of the fuel supply pipe 42, there is no need to limit the shape of the main body 61 of the nozzle 53 to that shown in FIG. 2. As shown in FIG. 7, for example, a nozzle 85 may be used that faces the tip surface 42b of the fuel supply pipe 42 and has a main body 84 with a sloped surface 83 on which the spray holes 82 are formed.

(Summary of effects)
As described above, the burner 40 is a burner 40 that sends a mixture of fuel and air to the combustion chamber 21, and is characterized in that it includes an air supply pipe 41 having a flow path 51 that supplies air toward the combustion chamber 21, a fuel supply pipe 42 that is inserted into the flow path 51 of the air supply pipe 41 and supplies fuel, a constriction forming portion 42a that is provided at the tip of the fuel supply pipe 42 and forms a constriction portion 52 that constricts the flow path 51 between the air supply pipe 41 and the inner wall surface 41b of the air supply pipe 41, a main body portion 61 having an ejection hole 63 that ejects fuel toward the upstream side of the flow path 51, and a tubular portion 62 that sends the fuel supplied by the fuel supply pipe 42 to the main body portion 61, and the main body portion 61 includes a nozzle 53 that is arranged in the vicinity of the combustion chamber 21, and a diffusion portion 56 that is provided at the connection portion between the air supply pipe 41 and the combustion chamber 21 and diffuses the air flowing from the flow path 51 into the combustion chamber 21 within the combustion chamber 21.

According to this, a premixed mixture with an excess of fuel and a mixture in which the fuel flowing toward the combustion chamber 21 is diffused and mixed with air are sent into the combustion chamber 21, and the mixture is subjected to primary combustion. In this primary combustion, most of the air contained in the mixture is used for combustion, and the amount of nitrogen compounds NOx generated by chemical reactions accompanying the temperature rise due to the primary combustion is reduced. In this primary combustion, some of the fuel contained in the mixture is unburned, but the unburned fuel flows with the water vapor generated during the primary combustion and is mixed with air diffused inside the combustion chamber 21 for secondary combustion. In this secondary combustion, the mixture containing water vapor is burned, so the temperature rise due to the combustion of the fuel is suppressed. As a result, the generation of nitrogen compounds NOx due to chemical reactions accompanying the secondary combustion is suppressed. In addition, the high-temperature combustion gas is diluted by being rapidly mixed with air again by the vortex 72, and the process of generating thermal nitrogen compounds NOx due to high temperatures is stopped. Therefore, the total amount of nitrogen compounds NOx generated when fuel is burned inside the combustion chamber 21 is reduced.

In addition, the burner 40 uses the flame generated by the primary combustion to perform secondary combustion of the mixture of air diffused inside the combustion chamber 21 and fuel that is unburned in the primary combustion. Therefore, there is no need to place components such as a burner for reheating combustion or an air injection nozzle that supplies air required during secondary combustion downstream of the inner tube 20, as is used in dry combustion type combustors, and the overall configuration of the combustor 10 can be simplified and the combustor 10 can be made smaller. In addition, when an air injection nozzle is used, a region is generated in which the unburned fuel flowing from the primary combustion region and the air cannot be rapidly mixed. However, in the burner 40, a vortex 72 is generated inside the combustion chamber 21 by the air flowing into the inside of the combustion chamber 21, and the vortex 72 makes it possible to reliably and rapidly mix the fuel and air that are unburned during primary combustion.

The nozzle 53 provided on the fuel supply pipe 42 ejects fuel into the flow passage 51 of the air supply pipe 41, and the fuel is mixed with the air by a vortex generated by the air that has passed through the narrowing section 52. In a conventional premixing pipe, the fuel and air are mixed upstream of the premixing pipe, so that the flame caused by the combustion in the combustion chamber 21 penetrates the inside of the burner 40 and reaches the upstream side of the burner 40, which is called a flashback. However, in the burner of the present invention, the air flowing inside the air supply pipe 41 is used to mix with the fuel downstream of the burner 40, so that the flame caused by the combustion in the combustion chamber 21 penetrates the inside of the burner 40 and reaches the upstream side of the burner 40, which is called a flashback, can be prevented.

In addition, when the inner diameter of the air supply pipe 41 is D1, the maximum outer diameter of the constriction forming portion 42a is D2, and the outer diameter of the tubular portion 62 is D3, the ratio of the outer diameter D2 of the constriction forming portion 42a to the inner diameter D1 of the air supply pipe 41 is set to 0.75 to 0.9, and the ratio of the outer diameter D3 of the tubular portion 62 to the inner diameter D1 of the air supply pipe 41 is set to 0.05 to 0.2.

For example, if the ratio of the outer diameter D2 of the constriction forming portion 42a to the inner diameter D1 of the air supply pipe 41 is less than 0.75, when the air and fuel are mixed by the vortex 71 generated downstream of the constriction portion 52, the amount of air mixed is reduced, and a lot of fuel is generated that is unburned during primary combustion. Also, when air flows into the inside of the combustion chamber 21, the vortex 72 generated inside the combustion chamber 21 prevents the air from being rapidly mixed with the fuel that is unburned during primary combustion. As a result, the combustion temperature during secondary combustion in the combustion chamber 21 rises, and the amount of nitrogen compound NOx generated by secondary combustion increases.

On the other hand, by setting the ratio of the outer diameter D2 of the constriction forming portion 42a to the inner diameter D1 of the air supply pipe 41 to 0.75 to 0.9, it is possible to suppress the generation of unburned fuel during primary combustion and to rapidly mix the unburned fuel and air caused by primary combustion. As a result, it is possible to suppress the generation of the nitrogen compound NOx associated with secondary combustion.

In addition, when the inner diameter of the air supply pipe 41 is D1 and the distance from the main body 61 to the combustion chamber 21 is H1, the ratio of the inner diameter D1 of the air supply pipe 41 to the distance H1 from the main body 61 to the combustion chamber 21 is set to 0.15 to 0.45.

This allows the mixture of air and fuel in an excess state to be sent immediately into the combustion chamber 21. This prevents the flame from burning the mixture in the combustion chamber 21 from penetrating the inside of the burner 40 and burning the mixture inside the burner 40, which is known as backfiring.

The diffusion section 56 is an arc-shaped curved surface provided at the connection between the air supply pipe 41 and the combustion chamber 21, and when the inner diameter of the air supply pipe 41 is D1 and the radius of the diffusion section 56 is R1, the ratio of the radius R1 of the diffusion section 56 to the inner diameter D1 of the air supply pipe 41 is set to 0.2 or more.

According to this, the air flowing into the combustion chamber 21 is diffused inside the combustion chamber 21. At this time, when the ratio of the radius R1 of the diffusion section 56 to the inner diameter D1 of the air supply pipe 41 is less than 0.2, the air flowing into the combustion chamber 21 does not generate a vortex 72 inside the combustion chamber 21. Therefore, the high-temperature combustion gas generated by the primary combustion in the combustion chamber 21 flows directly downstream of the combustion chamber 21. As a result, the air inside the combustion chamber 21 chemically reacts with the high-temperature gas and continues to generate nitrogen compounds NOx. On the other hand, in the present invention, the ratio of the radius R1 of the diffusion section 56 to the inner diameter D1 of the air supply pipe 41 is set to 0.2 or more, so that the air flowing into the combustion chamber 21 generates a vortex 72 inside the combustion chamber 21. The generation of this vortex 72 causes the fuel that is not burned during primary combustion and the water vapor generated by primary combustion to be rapidly mixed with the air. This rapid mixing also dilutes the high-temperature combustion gas generated by the primary combustion in the combustion chamber 21, stopping the process of generating thermal nitrogen compounds (NOx) due to high temperatures.

The combustor 10 is characterized by comprising the burner 40 described above, an inner cylinder 20 having a combustion chamber 21 therein for burning the air-fuel mixture sent from the burner 40, and an outer cylinder 30 that is disposed outside the inner cylinder 20 and forms a space 31 between the inner cylinder 20 and the outer cylinder 30 for supplying air to the burner 40.

According to this, a fuel-rich mixture is sent into the combustion chamber 21, and the mixture is subjected to primary combustion. In this primary combustion, most of the air contained in the mixture is used for combustion, and the amount of nitrogen compounds NOx generated by chemical reactions accompanying the temperature rise due to the primary combustion is reduced. In this primary combustion, some of the fuel contained in the mixture is unburned, but the unburned fuel flows with the water vapor generated during the primary combustion and is mixed with air that is diffused inside the combustion chamber 21 and is subjected to secondary combustion. In this secondary combustion, the mixture containing water vapor is burned, so the temperature rise due to the combustion of fuel is suppressed. Furthermore, the high-temperature combustion gas is diluted by being rapidly mixed with air again by the vortex 72, and the process of generating thermal nitrogen compounds NOx due to high temperatures is stopped. As a result, the generation of nitrogen compounds NOx due to chemical reactions accompanying secondary combustion is suppressed. Therefore, the total generation amount of nitrogen compounds NOx generated when fuel is burned inside the combustion chamber 21 is reduced.

As described above, the combustion method includes the steps of: generating a vortex 71 inside the air supply pipe 41 by air flowing into the air supply pipe 41 that constitutes the burner 40; ejecting fuel supplied by a fuel supply pipe 42 inserted into the air supply pipe 41 toward the upstream side of the air supply pipe 41 using a nozzle 53 provided at the tip of the fuel supply pipe 42; mixing the air flowing into the air supply pipe 41 and the fuel ejected from the nozzle 53 by the vortex 71 to a state in which the fuel is in an excess of fuel; and mixing the air flowing into the air supply pipe 41 and the fuel ejected from the nozzle 53 by the vortex 71. The method is characterized by having a process of performing primary combustion of the mixture of air and fuel inside the combustion chamber 21, a process of diffusing the air sent from the air supply pipe 41 to the combustion chamber 21 inside the combustion chamber 21 by a diffusion section 56 provided at the connection between the air supply pipe 41 and the combustion chamber 21, a process of mixing the fuel that is unburned by the primary combustion with the air sent to the combustion chamber 21 by the vortex 72, and a process of performing secondary combustion of the mixture of fuel and air mixed by the vortex 72 inside the combustion chamber 21.

According to this, a fuel-rich mixture is sent into the combustion chamber 21, and the mixture is subjected to primary combustion. In this primary combustion, most of the air contained in the mixture is used for combustion, and the amount of nitrogen compounds NOx generated by chemical reactions accompanying the temperature rise due to the primary combustion is reduced. In this primary combustion, some of the fuel contained in the mixture is unburned, but the unburned fuel flows together with the water vapor generated during the primary combustion and is mixed with the air that is diffused inside the combustion chamber 21 and is subjected to secondary combustion. In this secondary combustion, the mixture containing water vapor is burned, so the temperature rise caused by the combustion of the fuel is suppressed. As a result, the generation of nitrogen compounds NOx due to chemical reactions accompanying the secondary combustion is suppressed. Furthermore, the high-temperature combustion gas is diluted by being rapidly mixed with air again by the vortex 72, and the process of generating thermal nitrogen compounds NOx due to high temperatures is stopped. Therefore, the total amount of nitrogen compounds NOx generated when fuel is burned inside the combustion chamber 21 is reduced.

REFERENCE SIGNS LIST 10 combustor 20 inner cylinder 30 outer cylinder 40 burner 41 air supply pipe 42 fuel supply pipe 42a throttle forming portion 53 nozzle 61 main body portion 62 tubular portion 63 ejection hole 71 vortex 72 vortex 76 region where primary combustion takes place 77 region where secondary combustion takes place

Claims (6)

A burner that burns a mixture of fuel and air in a combustion chamber,
a first supply pipe having a flow path for supplying the air toward the combustion chamber;
a second supply pipe that is inserted into the flow path of the first supply pipe and supplies the fuel;
a constriction forming portion provided at a tip end of the second supply pipe and forming a constriction portion that constricts the flow path between the tip end and an inner wall surface of the first supply pipe;
a fuel ejection section including a main body section having an ejection hole for ejecting the fuel toward an upstream side of the flow path, and a tubular section for sending the fuel supplied by the second supply pipe to the main body section, the main body section being disposed in the vicinity of the combustion chamber;
a diffusion section provided at a connection between the first supply pipe and the combustion chamber, diffusing the air flowing into the combustion chamber from the flow path within the combustion chamber;
A burner comprising: 2. The burner according to claim 1,
When the inner diameter of the first supply pipe is D1, the outer diameter of the throttle forming portion is D2, and the outer diameter of the tubular portion is D3,
a ratio of an outer diameter D2 of the throttle forming portion to an inner diameter D1 of the first supply pipe is set to 0.75 to 0.9;
A burner, characterized in that a ratio of an outer diameter D3 of the tubular portion to an inner diameter D1 of the first supply pipe is set to be 0.05 to 0.2. 2. The burner according to claim 1,
When the inner diameter of the first supply pipe is D1 and the distance from the main body to the combustion chamber is H1,
A burner, characterized in that a ratio of a distance H1 from said main body to said combustion chamber to an inner diameter D1 of said first supply pipe is set to be 0.15 to 0.45. 2. The burner according to claim 1,
the diffusion portion is an arc-shaped curved surface provided at a connection portion between the first supply pipe and the combustion chamber,
When the inner diameter of the first supply pipe is D1 and the radius of the diffusion portion is R1,
a ratio of a radius R1 of the diffusion portion to an inner diameter D1 of the first supply pipe is set to 0.2 or more. A burner according to any one of claims 1 to 4;
an inner cylinder having a combustion chamber therein for combusting the air-fuel mixture sent from the burner;
an outer cylinder disposed outside the inner cylinder and forming a space between the outer cylinder and the inner cylinder for supplying the air to the burner;
A combustor comprising: generating a first vortex inside a first supply pipe constituting a burner by air flowing into the first supply pipe;
a step of ejecting fuel supplied from a second supply pipe inserted into the first supply pipe toward an upstream side of the first supply pipe using a nozzle provided at a tip of the second supply pipe;
mixing the air flowing into the first supply pipe and the fuel ejected from the nozzle by the first vortex so that the fuel is in an excess fuel state;
a step of primarily combusting the mixture of the air and the fuel mixed by the first vortex inside a combustion chamber;
a step of diffusing the air sent from the first supply pipe to the combustion chamber inside the combustion chamber by a diffusion section provided at a connection portion between the first supply pipe and the combustion chamber to generate a second vortex inside the combustion chamber;
mixing the fuel that is uncombusted by the primary combustion and the air that is sent into the combustion chamber by the second vortex;
a step of subjecting the mixture of the fuel and the air mixed by the second vortex to secondary combustion inside the combustion chamber;
A combustion method comprising the steps of:

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