JPH0117061B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a combustor for a gas turbine, and particularly to a combustor for a gas turbine.
A gas turbine that uses the LNG (liquefied natural gas)-fired lean burn system and divides the inner cylinder into a sub-combustion chamber and a main combustion chamber, and injects fuel in multiple stages to more effectively reduce NOx. Regarding the combustor.

[Prior art]

The most advantageous way to reduce NOx in gas turbine combustion is through lean combustion, in which a relatively large amount of air is flowed and combusted relative to the fuel flow rate.

In particular, during combustion, it is possible to lower the combustion temperature, promote mixing of fuel and air, and shorten the NOx generation time to achieve uniform low-temperature combustion.

Conventionally, a lean combustor with an auxiliary combustion chamber has been proposed as a specific means for establishing the above combustion method.

However, in the conventional lean combustor with sub-combustion chamber,
Since fuel is supplied from a single fuel nozzle, if a large amount of fuel is introduced from the fuel nozzle, immediate lean mixing will not occur in the fuel and air mixing process, so the high temperature region will be expanded.
The disadvantage is that NOx generation is extremely high. Also,
If excessive air is introduced in order to reduce NOx, a supercooled area is formed, which tends to increase the amount of unburned matter such as CO.

These points are further illustrated in Figures 1, 2, and 3.
This will be explained in detail based on the figures.

As shown in FIG. 1, the gas turbine plant includes a compressor 1, a combustor 2 with an auxiliary combustion chamber, a turbine 3, and a load section 4 such as a generator.

As shown in FIG. 1, the conventional combustor 2 with an auxiliary combustion chamber includes an inner cylinder 5 having an auxiliary combustion chamber 11 and a main combustion chamber 12, a transition cylinder 6, an outer cylinder 7 that covers both cylinders, and an outer cylinder 7 that covers both cylinders. and a fuel supply device provided at the front end of the auxiliary combustion chamber 11. The fuel supply system consists of a single fuel nozzle 9 and an air swirler 10 arranged annularly around the end of the fuel nozzle 9.
The main combustion chamber 12 is formed to have a larger diameter than the sub-combustion chamber 11, and is connected to the rear part of the sub-combustion chamber 11 by a non-wide connecting portion 13. The sub-combustion chamber 1
1 has a first air swirl supply hole group 14 on the front end side.
A second air swirl supply hole group 15 is provided on the rear end side, and an air introduction hole 16 is provided in the intermediate portion. The main combustion chamber 12 is provided with an air introduction hole 17 on the front end side, a dilution air introduction hole 18 on the rear end side, and a cooling hole group 19 in the middle part.
is provided. In addition, in Figure 1, 20
21 represents fuel, 21 represents air supplied from the compressor to the combustor, and 22 represents combustion gas whose temperature is adjusted at the rear of the combustor and is supplied to the turbine.

In the combustor with an auxiliary combustion chamber, an air amount of about 50% or more of the total air amount is introduced into the auxiliary combustion chamber 11 whose cross-sectional area is smaller than that of the main combustion chamber 12. Therefore, by increasing the average cross-sectional flow velocity to promote mixing of fuel and air, and at the same time shortening the residence time of combustion gas, it is attempted to effectively reduce NOx.

As a result of the experiment, as shown in FIG. 2, the combustion state in the sub-combustion chamber 11 is the dominant combustion state in the generation of NOx, and by increasing the excess air ratio λ of the sub-combustion chamber 11, NOx can be reduced. There is a tendency for reductions to be achieved. However, in the region where the excess air ratio λ is large,
Unburned matter such as CO increases, and as shown in Figure 3,
Combustion during partial load in the gas turbine operating region results in lean combustion conditions that are quite severe, resulting in unstable combustion and an increase in unburned matter, which ultimately becomes a cause for restricting lean combustion.

That is, in lean combustion using only a fuel supply device composed of a single combustion nozzle 9 and an air swirler 10, as in a conventional combustor with a sub-combustion chamber,
Even if the amount of fuel supplied becomes relatively large and excessive air is introduced, a sufficiently lean mixture cannot be obtained. In addition, when a large amount of fuel is supplied to the airflow, an optimal combustion range (stoichiometric mixture ratio = 1) is necessarily formed during the combustion process, and a high-temperature flame front exists.
The amount of NOx produced increases. In particular, when a large amount of fuel is introduced from the single fuel nozzle 9, it is difficult to achieve an instant lean mixture ratio in the fuel and air mixing process, so the high temperature region is expanded and NOx generation increases significantly. On the other hand, when excessive air is introduced to reduce NOx, a supercooled section is formed and the amount of NOx produced decreases, but unburned substances such as CO tend to increase.

[Purpose of the invention]

The purpose of the present invention is to eliminate the drawbacks of the prior art described above, to achieve a significant reduction in NOx through optimal lean combustion even when the gas turbine is under high load, and to achieve stable combustion with good flame holding performance. The object of the present invention is to provide a gas turbine combustor that can be realized.

[Summary of the invention]

The present invention provides a combustor in which an auxiliary combustion chamber is connected to a main combustion chamber having a larger diameter, in which the auxiliary combustion chamber is provided with a single fuel nozzle and an air swirler provided at its front end. Fuel and air are introduced from a fuel supply device, and fuel and air are introduced into the main combustion chamber from a fuel supply device equipped with a fuel supply means and an air swirler provided on the shoulder between the auxiliary combustion chamber and the main combustion chamber. By introducing fuel and air in two stages and introducing it in a distributed manner, optimal lean combustion can be carried out even when the gas turbine is under high load, resulting in a significant reduction in fuel consumption.
In addition, the fuel supply device installed on the shoulder between the auxiliary combustion chamber and the main combustion chamber can be used to form a concentrated region in the mixture of fuel and air supplied to the main combustion chamber. By doing so, it was possible to stabilize the flame and thus achieve stable combustion.

[Embodiments of the invention]

Hereinafter, the present invention will be explained based on the drawings.

4, 5 and 6 show one embodiment of the invention.

In the embodiment shown in these figures, the outer cylinder 23,
Inner cylinder 2 having an auxiliary combustion chamber 25 and a main combustion chamber 26
4. A fuel supply device provided at the front end of the auxiliary combustion chamber 25 (hereinafter referred to as the first-stage fuel supply device); a connecting portion 32 between the auxiliary combustion chamber 25 and the main combustion chamber 26;
A fuel supply device (hereinafter referred to as
(referred to as a second stage fuel supply device).

The opening on the front end side of the outer cylinder 23 is closed with an end cover 23'.

The inner cylinder 24 has an auxiliary combustion chamber 25 and a main combustion chamber 26.
It is divided into. The main combustion chamber 26 is formed to have a larger diameter than the sub-combustion chamber 25, and
5 by a connecting portion 32 having a shoulder 32'. Note that a trailing portion 26' of the main combustion chamber 26 in the inner cylinder 24 is formed to have a smaller diameter than the main combustion chamber 26.

The first stage fuel supply device includes a single fuel nozzle 27 provided facing the sub-combustion chamber 25 from the outside of the end plate 23', and provided around the outlet side end of the fuel nozzle 27. The air swirler 28 is configured to include an air swirler 28.

The auxiliary combustion chamber 25 is provided with an air swirling supply hole group 29 at the front end, a plurality of air introduction scoop holes 30 at intervals in the circumferential direction at the middle part, and a group of air supply scoop holes 30 at the rear end. A plurality of air introduction holes 31 are provided at intervals in the circumferential direction.

The second stage fuel supply device includes a fuel chamber 33 as a fuel supply means, an air swirler 35, and a fuel nozzle hole 36 as a fuel passage. The fuel chamber 33 is formed in an annular shape concentric with the main combustion chamber 26, and is attached to the shoulder portion 32' of the connecting portion 32. Further, the fuel chamber 33 is connected to a fuel supply source (not shown) through a fuel supply pipe 34, and the fuel chamber 33 is connected to a fuel supply source (not shown) through a fuel supply pipe 34.
3 shows the turbine 1/ in the gas turbine operating region.
When the load is high (2 loads or more), the amount of fuel is fed in proportion to the load. The air swirler 35 is formed in an annular shape inscribed in the fuel chamber 33, and is divided into a plurality of small chambers in the circumferential direction by vanes, as shown in FIG. As shown in FIG. 6, the fuel injection hole 36 is
Air swirler 3 from the inner circumferential wall of fuel chamber 33
Each of the booths No. 5 is opened to the outside inside.

The main combustion chamber 26 is provided with a group of cooling holes 37, and the trailing portion 26' of the main combustion chamber 26 is provided with dilution air introduction holes 38.

In addition, in FIGS. 4 and 6, 20a,
Reference numeral 20b indicates fuel such as LNG that is introduced into the first and second stage fuel supply devices, and 21a and 21b indicate air that is also introduced into the first and second stage fuel supply devices.

Next, the operation of the combustor of the above embodiment will be explained with reference to FIGS. 4 to 8.

From ignition to the partial load of the turbine operating region, that is, the turbine 1/2 load, the fuel flow rate F ₁ shown in FIG. 7 is introduced from the fuel nozzle 27 of the first stage fuel supply device, and the air swirler 28 , air swirl supply hole group 29, air introduction scoop hole 30,
Air is introduced from the air introduction hole 31, and the auxiliary combustion chamber 25 is
lean combustion mainly in the auxiliary combustion chamber 25.

Then, when the load is high, such as 1/2 load or more of the turbine, the fuel nozzle 27 of the first stage fuel supply device and the second
Fuel is introduced from the fuel chamber 33 of the fuel supply device in the first stage, and as shown in _FIG .
Lean combustion is established with a fuel flow rate (F ₁ +F ₂ ) that is the sum of the fuel flow rate F ₂ of the fuel chamber 33 of the fuel supply device in the stage.

According to experiments, the distribution of the fuel flow rate to the sub-combustion chamber 25 and the main combustion chamber 26, as shown in _FIG . It has become clear that the effective application range L is 20 to 60%. In FIG. 8, when F ₂ <20%, the combustion state in the main combustion chamber 26 becomes leaner, which is advantageous for reducing NOx.
The fuel flow rate F ₁ introduced into the auxiliary combustion chamber 25 is F ₁ >80%
Therefore, when combustion is continued at the fuel flow rate F ₁ , the excess air ratio λ in the sub-combustion chamber 25 tends to decrease and the amount of NOx produced increases. Therefore, even if the amount of NOx generated in the main combustion chamber 26 decreases when F ₂ <20% is introduced into the main combustion chamber 26, the amount of NOx generated in the auxiliary combustion chamber 25 becomes dominant, and the combustion NOx reduction at the room outlet is not achieved.

On the other hand, in the region of F ₂ >60%, lean combustion is not performed in the main combustion chamber 26, so NOx increases,
Since F ₁ <40%, the excess air ratio λ in the auxiliary combustion chamber 25 becomes too large, resulting in an increase in the amount of CO generated,
Damages such as flame not being properly propagated from the auxiliary combustion chamber 25 to the main combustion chamber 26 occur.

Therefore, lean combustion is continued in the auxiliary combustion chamber 25 and the main combustion chamber 26 by supplying the amount of air relative to the fuel flow rate so that the excess air ratio λ at the outlet of the auxiliary combustion chamber 25 is 1.3 or more. You can do it by doing this.

Further, in the embodiment shown in FIGS. 4 to 6, the fuel injection holes 36 are opened outside the small space chamber into which the air swirler 35 in the second stage fuel supply device is divided. Therefore, the fuel 20b introduced into the main combustion chamber 26 through each small space chamber of the air swirler 35
The mixture of air and air 21b is concentrated on the outside of each small space chamber outlet and becomes thinner on the inside, forming a dark and dark region.
Thereby, flame propagation in the main combustion chamber 26 can be improved, flame stabilization can be achieved, and as a result, stable combustion can be realized.

Next, FIG. 9 shows another embodiment of the present invention.

In this embodiment, the fuel chamber 33 of the second stage fuel supply device and each divided small space chamber of the air swirler 35 are connected to a fuel pipe 40 as a fuel passage.
communicated via. And fuel pipe 4
0 is opened to the inside of the small space chamber.

Therefore, in this embodiment, the mixture of fuel 20b and air 21b is richer on the inside and thinner on the outside at the outlet of each small space, forming a dark/concentrated region.

In the embodiment shown in FIG. 9, other structures and functions are the same as those in the embodiment shown in FIGS. 4 to 6.

Next, FIGS. 10 and 11 show another embodiment of the present invention.

In this embodiment, the second stage fuel supply device is constructed by attaching a plurality of sets of air swirlers 41 and fuel nozzles 42 at intervals in the circumferential direction. Each set of air swirlers 41 is attached to the shoulder 32' of the connecting part 32 between the auxiliary combustion chamber 25 and the main combustion chamber 26, and each set of fuel nozzles 42 is inserted into the center of the air swirler 41. There is.

With this configuration, it is possible to control the fuel flow rate for each fuel nozzle 42, and in each pair of air swirler 41 and fuel nozzle 42, the fuel 20
Since the mixture of air 21b and air 21b is rich in the center and thin in the surrounding area, it is possible to form a pronounced dark and light region.
Even under conditions where flame propagation from the auxiliary combustion chamber 25 is severe, stable combustion can be achieved more effectively.

In addition, in the embodiment shown in FIGS. 10 and 11, other configurations and functions are as described in the fourth section.
This embodiment is similar to the embodiment shown in FIGS.

In the present invention, the second-stage fuel supply device that sends the air-fuel mixture to the main combustion chamber 26 is not limited to that of the illustrated embodiment, but is essentially a combination of a fuel supply means and an air swirler. Any material that can be attached using the shoulder 32' between the auxiliary combustion chamber 25 and the main combustion chamber 26 may be used.

Further, the specific structure for forming a rich/dark region in the mixture of fuel and air in the second stage fuel supply device is not limited to the illustrated embodiment.

〔Effect of the invention〕

According to the present invention described above, in a combustor that connects a sub-combustion chamber and a main combustion chamber having a larger diameter, the sub-combustion chamber has a first combustion chamber equipped with a single fuel nozzle and an air swirler. Fuel and air are introduced from the fuel supply device of the second stage, and the main combustion chamber is equipped with a fuel supply means and an air swirler provided on the shoulder between the auxiliary combustion chamber and the main combustion chamber. The fuel and air are introduced from the fuel supply system, and the fuel and air are introduced in two stages in a distributed manner, making it possible to perform optimal lean combustion even when the gas turbine is under high load, resulting in a significant reduction in It has the effect of reducing NOx,
Further, according to the present invention, the second stage fuel supply device is configured to form a rich/concentrated region in the mixture of fuel and air supplied to the main combustion chamber, so that flame stabilization can be achieved. This also has the effect of realizing stable combustion.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of a gas turbine blunt equipped with a conventional combustor with an auxiliary combustion chamber, and Figure 2 shows the excess air ratio, NOx generation amount, and CO at the outlet of the auxiliary combustion chamber in a conventional combustor with an auxiliary combustion chamber. Figure 3 is a diagram showing the relationship between the production amounts, Figure 3 is a diagram showing the state of air inflow into the secondary combustion chamber in the gas turbine operating region in a conventional combustor with secondary combustion chamber, and Figures 4 to 6 are diagrams showing the state of air inflow into the secondary combustion chamber in the gas turbine operating region in a conventional combustor with secondary combustion chamber. This shows an example, and FIG. 4 is a longitudinal sectional front view;
FIG. 5 is a longitudinal sectional side view of the second stage fuel supply device, FIG. 6 is a partially enlarged longitudinal sectional front view, FIG. 7 is a diagram showing the relationship between turbine load and fuel flow rate in the present invention, and FIG. The figure shows the fuel distribution to the sub-combustion chamber and the effective range of application for reducing NOx in the present invention.
FIG. 9 shows another embodiment of the present invention, and is an enlarged vertical sectional front view of a portion of the second stage fuel supply device, and FIGS. 10 and 11 show other embodiments of the present invention. 10 is a longitudinal sectional front view, and FIG. 11 is a sectional view taken along line A-A' in FIG. 23... Outer cylinder of the combustor, 24... Inner cylinder of the same, 25
...Sub-combustion chamber, 26...Main combustion chamber, 27...First
Single fuel nozzle of stage fuel supply device, 28...
Air swirler, 29, 30, 31...Various air introduction holes, 32'...Shoulder between the auxiliary combustion chamber and the main combustion chamber,
33...Fuel chamber as a fuel supply means of the second stage fuel supply device, 35...Air swirler thereof,
36...Fuel injection hole as the same fuel passage, 37,3
8...Various air introduction holes, 40...Fuel pipe as a fuel passage connecting the fuel chamber and the air swirler, 41...Air swirler of the second stage fuel supply device, 42...Fuel supply means of the same as a fuel nozzle.

Claims (1)

[Scope of Claims] 1. An auxiliary combustion chamber is formed at the head of the combustor inner cylinder, and a main combustion chamber having a larger diameter than the auxiliary combustion chamber is formed at the rear of the auxiliary combustion chamber,
The combustion chamber is provided with a fuel supply device including a single fuel nozzle and an air swirler, and each of the auxiliary combustion chamber and the main combustion chamber is provided with a plurality of fuel nozzles arranged in multiple stages in the length direction, and each stage has a plurality of fuel supply devices in the circumferential direction. In a combustor having various air inlet holes, (a) a fuel supply device is provided on the shoulder between the auxiliary combustion chamber and the main combustion chamber, and (b) the fuel supply device is an air swirler. and a fuel supply channel opening toward the air swirler, and (c) the fuel supply channel has an inner peripheral portion of the air swirler,
(d) In a cross section of the air mixture discharged from the air swirler to the main combustion chamber, the air swirler has an opening in a plane perpendicular to the central axis of the combustor inner cylinder. A combustor for a gas turbine characterized by being configured such that the concentration of the air-fuel mixture changes in the radial direction. 2. The fuel supply device that supplies the air-fuel mixture to the main combustion chamber includes a fuel chamber as a fuel supply means, an air swirler, and a fuel passage that introduces fuel from the fuel chamber to the air swirler, and The chamber and the air swirler are formed in an annular shape concentric with the main combustion chamber, the air swirler is divided into a plurality of small space chambers in the circumferential direction, and the fuel passage is biased in each of the small space chambers. The combustor for a gas turbine according to claim 1, characterized in that the combustor is opened at a certain position. 3. The fuel supply device that supplies the air-fuel mixture to the main combustion chamber is composed of a plurality of air swirlers and the same number of fuel nozzles as fuel supply means,
inserting the fuel nozzle into the center of each air swirler;
The gas turbine according to claim 1, wherein the air swirler and fuel nozzle set is mounted on a shoulder between a sub-combustion chamber and a main combustion chamber at intervals in the circumferential direction. combustor. 4. The amount of fuel supplied to the auxiliary combustion chamber is divided into 40 to 80% and the amount of fuel supplied to the main combustion chamber is divided into 20 to 60%,
The combustor for a gas turbine according to claim 1, characterized in that it performs two-stage combustion. 5. The combustor for a gas turbine according to claim 4, wherein air is supplied so that the excess air ratio at the outlet of the auxiliary combustion chamber becomes 1.3 or more.