JP4622100B2 - Low NOx combustor for gas turbine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a low NOx combustor for a gas turbine.
[0002]
[Prior art]
FIG. 6 is an overall configuration diagram of a conventional low-NOx combustor for a gas turbine. As shown in this figure, the conventional low NOx combustor includes a pilot burner 8 arranged in the center and a plurality of (only one shown in the figure) main burners 9 arranged around the pilot burner 8. . In this figure, 1 is a scroll portion, 2 is a combustor liner, 3 is a casing, 4 is a spark plug (igniter), and air 6 flows between the casing 3 and the liner 2 to reach the burners 8 and 9. The burner and other parts flow into the liner 2 to form flames 7a and 7b, and the generated combustion gas is guided to the gas turbine (not shown) through the scroll unit 1 so as to drive it. It has become.
[0003]
In FIG. 6, the main burner 9 is composed of a main injection valve 9a and a premixing tube 9b arranged coaxially with each other. Fuel F is supplied to the main injection valve 9a from the outside through the casing 3. For example, gas fuel or liquid fuel is used as this fuel. The premixing tube 9b is a cylindrical tube whose lower end is opened in this figure, and the fuel and air are easily mixed inside. That is, the main burner 9 is a premixed lean burner composed of a main injection valve 9a and a premixing tube 9b. With this configuration, the fuel F can be injected into the premixing tube 9b by the main injection valve 9a, the fuel F can be premixed with a sufficient amount of air in the premixing tube 9b, and the lean combustion can be performed.
In such a premixed combustion type combustor, fuel is premixed with a sufficient amount of air and this is burnt in a lean manner. Therefore, there is no hot spot, high temperature flame is eliminated, and low NOx can be realized. it can.
[0004]
[Problems to be solved by the invention]
However, in the above-described conventional cylindrical premixing tube 9b, the pilot flame 7a and the premixing flame 7b are in contact only with a line. Therefore, there has been a problem that the mixing of the pilot flame 7a and the lean premixed gas is slow. For this reason, the supply of the premixed gas to the lean premixed gas from the pilot flame 7a, which is a factor that stabilizes the flame, such as the amount of heat and radicals, is poor, and it has been difficult to hold the diluted premixed flame lacking in combustion stability. As a result, the combustion efficiency was reduced.
[0005]
The present invention has been made to solve such problems. That is, an object of the present invention is for a gas turbine that can improve the combustion stability of a lean premixed flame in a low NOx gas turbine combustor using a lean premixing system, and can reliably hold the flame and increase the combustion efficiency. The object is to provide a low NOx combustor.
[0006]
[Means for Solving the Problems]
According to the present invention, a diffusion combustion type pilot burner (12) and a plurality of premixed combustion type main burners (14) disposed therearound are provided, and the main burner (14) is a main injection valve. (15) and a premixing pipe (16), and the outlet shape of the premixing pipe is formed in a fan shape adjacent to the pilot burner ,
The premixing pipe (16) includes a cylindrical part (16a) adjacent to the main injection valve (15) and a deformed part (16b) connected to the cylindrical part and having a cross-sectional shape that changes from a circular shape to a fan shape. A featured low NOx combustor for a gas turbine is provided.
[0007]
According to the above-described configuration of the present invention, fuel and air are premixed inside the premixing pipe (16), and this premixed gas flows out from the fan-shaped premixing pipe outlet along the pilot flame into the fuel chamber. Can do. For this reason, the pilot flame and the premixed gas are in contact with each other on the surface adjacent to the fan-shaped pilot burner, and the mixing of the premixed gas and the pilot flame proceeds rapidly immediately after exiting the premixed tube at this interface. The amount of heat generated and the radicals can heat and activate the lean premixed gas in the main burner through the contact surface to increase the combustion stability and increase the combustion efficiency.
The premixing pipe (16) includes a cylindrical portion (16a) adjacent to the main injection valve (15) and a deformed portion (16b) connected to the cylindrical portion and having a cross-sectional shape that changes from a circular shape to a fan shape. The fuel and air injected from the main injection valve (15) at the cylindrical portion (16a) can be premixed with a strong swirl flow. In addition, the premixed gas can be changed to a fan-shaped flow at the deformed portion (16b), and can be discharged from the fan-shaped premixing tube outlet along the pilot flame into the fuel chamber.
[0009]
The deformed portion (16b) has an outer wall inclined inward so that the premixed gas flows inward. With this configuration, the flow of the premixed gas from the fan-shaped premixing tube outlet becomes inward, and the contact with the pilot flame can be further promoted.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In each figure, common portions are denoted by the same reference numerals, and redundant description is omitted.
[0011]
FIG. 1 is an overall configuration diagram showing a first embodiment of a low NOx combustor for a gas turbine according to the present invention. In this figure, (A) is a longitudinal sectional view, and (B) is a view taken along the line BB of (A).
[0012]
A low NOx combustor 10 shown in FIG. 1 (A) includes a pilot burner 12 disposed in the center and a plurality (for example, six) main burners 14 disposed around the pilot burner 12. The low NOx combustor 10 is a single tube combustor, 2 is a combustor liner, 3 is a casing, and 4 is a spark plug (igniter).
With this configuration, the air 6 flows between the casing 3 and the liner 2 and reaches the burners 12 and 14, and flows into the liner 2 through the burner and other portions to form flames 7 a and 7 b. The gas is guided to a gas turbine (not shown) through a scroll portion (not shown) and is driven.
[0013]
In FIG. 1A, a pilot burner 12 is a diffusion burner that diffuses and burns fuel in the combustion chamber 11. The main burner 14 is a premix burner in which fuel is premixed with air and burned in the combustion chamber.
[0014]
The premix burner 14 includes a main injection valve 15 and a premix pipe 16. Further, as shown in FIG. 1B, the outlet shape of the premixing tube 16 is formed in a sector shape adjacent to the pilot burner. In this fan shape, a short arc of the fan shape is arranged close to the circular outlet of the pilot burner 12 so that a donut shape surrounding the circular outlet of the pilot burner 12 is formed by a plurality of (six in this example) fan shapes. Yes.
[0015]
The premixing pipe 16 includes a cylindrical portion 16a adjacent to the main injection valve 15 and a deformed portion 16b that is connected to the cylindrical portion 16a and whose cross-sectional shape changes from a circular shape to a fan shape. The cylindrical portion 16a has an inner surface formed in a cylindrical shape so as to premix the fuel and air injected from the main injection valve 15 with a strong swirling flow formed by a swirl or the like. In addition, the deformed portion 16b has a smooth inner surface so that the premixed premixed gas is changed into a fan-shaped flow and flows out from the fan-shaped premixing tube outlet along the pilot flame into the fuel chamber. The deformed portion 16b is preferably formed to have a constant cross-sectional area so that the flow rate of the premixed gas does not change. In addition, the cross-sectional area may be gradually reduced so that the flow velocity can be increased and injected into the combustion chamber 11 as necessary.
[0016]
Further, the deformed portion 16b has an outer wall inclined inward so that the premixed gas flows inward, and the flow of the premixed gas from the fan-shaped premixed tube outlet is directed inward so that the pilot flame and It is designed to further promote the contact.
[0017]
FIG. 2 is a block diagram showing a second embodiment of the low NOx combustor of the present invention. In this figure, (A) is a side view and (B) is a BB arrow view. The low NOx combustor 10 of this example is an annular type, and is formed in a fan shape in which a donut-shaped portion surrounding the engine is divided into a plurality (four in this example). Each of the low NOx combustors 10 includes a plurality (three in this example) of diffusion combustion type pilot burners 12 and a plurality (four each) of premixed combustion type main burners 14 disposed therearound. It consists of. Other configurations are the same as those of the first embodiment shown in FIG.
[0018]
FIG. 3 is a principle diagram of the low NOx combustor of the present invention. In this figure, (A) shows a conventional type, and (B) shows the present invention.
According to the configuration of the present invention described above, fuel and air are premixed inside the premixing pipe 16, and this premixed gas is allowed to flow out from the fan-shaped premixing pipe outlet along the pilot flame 7a into the fuel chamber. Can do. Therefore, at the boundary surface adjacent to the fan-shaped pilot burner 12 (pilot injection valve), the pilot flame 7a and the premixed gas are in contact with each other, and the premixed gas and the pilot flame 7a immediately after exiting the premixing tube 16 at this interface. And the amount of heat and radicals generated in the pilot flame 7a can be heated and activated through the contact surface to increase the combustion stability and the combustion efficiency. .
[0019]
【Example】
Examples of the present invention will be described below based on test results.
[0020]
FIG. 4 is a diagram showing test results of the low NOx combustor of the present invention. In this test, the ratio L / D of the arc length L adjacent to the pilot burner 12 at the outlet of the sector 16b and the diameter D of the cylindrical portion 16a is 1.0, 1.4, and 2.4. Each was tested as type A, B, C. Moreover, the combustion chamber wall temperature near the premixing tube outlet was measured. The combustion chamber wall temperature in the vicinity of the outlet was attached to a place where the temperature easily rises due to heat transfer and radiation when the premixed flame ignites immediately in the combustion chamber and stably burns. Therefore, the increase in the temperature of the combustion chamber wall in this portion is a guideline for stable ignition and combustion.
[0021]
In FIG. 4, the horizontal axis represents the ratio L / D, and the vertical axis represents the rate of increase in the combustion chamber wall temperature in the vicinity of the premixing tube outlet. From this figure, the combustion chamber wall temperature rises by 20% or more at the ratio L / D1 or more, and rises by about 40% at about 1.5. Therefore, the ratio L / D is preferably 1 or more.
[0022]
FIG. 5 is a diagram showing another test result of the low NOx combustor of the present invention. In this figure, the horizontal axis represents the overall air-fuel ratio, and the vertical axis represents the combustion efficiency. In the figure, ▲ is the result of the present invention, and ● is the result of the prior art.
From this figure, it can be seen that the low NOx combustor of the present invention can achieve higher combustion efficiency at the same air-fuel ratio and higher air-fuel ratio at the same combustion efficiency than the conventional one.
[0023]
The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention.
[0024]
【The invention's effect】
As described above, in the present invention, a fan-shaped premixing tube having an increased contact area with the pilot burner is used. In other words, the exit shape of the premixing tube is fan-shaped, and the interference between the two is increased by increasing the contact area between the diffusion combustion type pilot flame formed to hold the lean premixed flame and the lean premixed flame. To stabilize the flame.
[0025]
As a result, the air premixed with the fuel inside the premixing pipe is supplied to the combustion chamber, but the premixing pipe outlet has a fan shape and is supplied in a flow along the pilot flame (FIG. 3). reference). For this reason, on the surface in contact with the pilot flame, the mixing of the premixed gas and the pilot flame proceeds rapidly immediately after leaving the premixing tube. The pilot flame generates heat and generates radicals, but the lean premixed flame is stabilized because a large amount of such factors that promote combustion can be taken in from the entire contact surface (see FIGS. 4 and 5). .
[0026]
That is, the low NOx combustor for a gas turbine according to the present invention enhances the combustion stability of the lean premixed flame in the low NOx gas turbine combustor using the lean premixing method, and reliably holds the flame to increase the combustion efficiency. It has excellent effects such as being able to.
[Brief description of the drawings]
FIG. 1 is a diagram showing a first embodiment of a low NOx combustor for a gas turbine according to the present invention.
FIG. 2 is a diagram showing a second embodiment of a low NOx combustor according to the present invention.
FIG. 3 is a principle diagram of a low NOx combustor according to the present invention.
FIG. 4 is a diagram showing test results of the low NOx combustor of the present invention.
FIG. 5 is a diagram showing another test result of the low NOx combustor of the present invention.
FIG. 6 is a configuration diagram of a conventional low-NOx combustor for a gas turbine.
[Explanation of symbols]
1 scroll part, 2 combustor liner,
3 Casing, 4 Spark plug (igniter),
6 air, 7 flames,
7a Pilot flame (diffusion flame), 7b Main flame (premixed flame),
8 pilot burners, 9 main burners,
9a main injection valve, 9b premixing pipe,
10 low NOx combustor, 11 combustion chamber,
12 Pilot burner (diffusion burner),
14 Main burner (premix burner,
15 main injection valves, 16 premixing tubes,
16a cylindrical part, 16b deformed part

Claims (2)

A diffusion combustion type pilot burner (12) and a plurality of premixed combustion type main burners (14) disposed around the diffusion burner type pilot burner (12), the main burner (14) being premixed with the main injection valve (15). Tube (16), and the outlet shape of the premixing tube is formed in a fan shape adjacent to the pilot burner ,
The premixing pipe (16) includes a cylindrical part (16a) adjacent to the main injection valve (15) and a deformed part (16b) connected to the cylindrical part and having a cross-sectional shape that changes from a circular shape to a fan shape. A low NOx combustor for gas turbines. The low-NOx combustor for a gas turbine according to claim 1 , wherein the deformed portion (16b) has an outer wall inclined inward so that the premixed gas flows inward.

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