JPH0882419A - Gas turbine combustor - Google Patents

Abstract

PURPOSE: To ensure low NOx from the starting operation of a gas turbine to a rated load operation by providing a main premixing combustor on an outer periphery of a cone type pilot premixing combustor where its cross section increases from an inlet of the combustor to an outlet thereof. CONSTITUTION: Air 10 compressed by a compressor passes between an outer cylinder 5 of a gas turbine combustor and a liner 6. Part of the air 10 enters from an inlet of a main premixing combustor 3 and mixes with a fuel 11 injected from a fuel nozzle 4 for combustion. Remaining air 10 enters from an inlet of a cone type pilot premixing combustor 2 and mixes with the fuel 11 injected from the fuel nozzle 4 and further flows out from an outlet of the cone type pilot premixing combustor 2 for combustion. Combustion in the cone type pilot premixing combustor 2 is performed in the combustor 2 when the flow rate of air is reduced while it is performed at the outlet of the combustor 2 when the flow rate of air is increased. Hereby, there is reduced the amount of production of NOx in a whole operation region from the time of firing when the speed of the gas turbine is increased to a rated operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustor applied to a gas turbine, and more particularly to a gas turbine suitable for reducing the NOx generation amount by burning only the premixed fuel from the start of the gas turbine to the full load. For combustors for automobiles.

[0002]

2. Description of the Related Art Normally, a combustor uses two combustion methods, diffusion combustion and premixed combustion, from the viewpoint of reducing NOx.
Stage combustion is not used, and diffusion combustion is normally performed from the start of the gas turbine to partial load, and premixed combustion is normally performed from partial load to rated load.

For example, Japanese Patent Laid-Open No. 1-54122 discloses a two-stage combustion combustor using diffusion combustion and premixed combustion.

In this case, the second-stage combustion is premixed combustion, and the premixing swirler provided inside the premixer mixes air and fuel to form a premixed mixture for combustion. It is fed into the chamber and burns. To reduce NOx, it is important to widen the premixed combustion region and narrow the diffusion combustion region or eliminate the diffusion combustion itself.

Further, as a combustor in which the cross-sectional area from the inlet to the outlet is gradually increased, it is described in JP-A-2-275221, JP-A-59-101551 and JP-A-59-129330. ing.

[0006]

[Problems to be Solved by the Invention] Since the flow rate of combustion air greatly changes from the start of the gas turbine to the rated load, especially when the gas turbine speeds up, from the viewpoint of combustion stability, when the gas turbine speeds up. From ignition to partial load, there was no choice but to use diffusion combustion. Therefore, the amount of NOx generated was high from the start of the gas turbine to the partial load.

The present invention has been made in view of the above problems, in which premixed combustion is stably performed from ignition at the time of acceleration of the gas turbine to the rated load, and the start-up to the rated load of the gas turbine is reduced. An object of the present invention is to provide a combustor for a gas turbine capable of converting to NOx.

[0008]

In order to achieve the above object, the premixed fuel should be stably burned even in the region where the air flow rate greatly changes from the gas turbine speed up to the no-load rated speed. A premixed combustor capable of

Here, in order to stably burn the premixed fuel, the fuel-air ratio, which is the ratio of the fuel flow rate to the air flow rate, and the flow velocity of the premixed fuel have a great influence, so no load is applied from the time the gas turbine accelerates. The structure of the premixed combustor (hereinafter referred to as the pilot premixed combustor) used in the area where the air flow rate changes significantly up to the rated speed, even if the air flow rate changes drastically It is necessary to have a combustor structure that can maintain the mixed fuel flow rate.

That is, in the combustor having the same cross-sectional area from the inlet to the outlet as in the conventional premixed combustor, the premixed fuel from the inlet to the outlet of the premixed combustor is changed in response to a large change in the air flow rate. Since the flow velocity changes drastically, it is impossible to maintain the premixed fuel flow velocity within the stable combustion range from the acceleration of the gas turbine to the no-load rated speed.

In order to solve this, the cross-sectional area from the inlet to the outlet of the premixing combustor is changed so that the premixing fuel flow velocity within the stable combustion range can always be obtained even if the air flow rate changes greatly. Will be required. Therefore, the pilot premixed combustor has at least one pilot premixed combustor in which the cross-sectional area from the inlet to the outlet of the premixed combustor is gradually widened, and in addition, from the no-load rated speed to the rated load. Has at least one premix combustor (hereinafter referred to as the main premix combustor) capable of stably burning the premix fuel in the region where the air flow rate of the gas hardly changes, and ignition during acceleration of the gas turbine The gas turbine combustor is designed so that NOx can be reduced by premixing combustion from the load to the rated load.

[0012]

[Operation] By having the pilot premixing combustor and the main premixing combustor whose cross-sectional area is gradually expanded from the inlet to the outlet of the premixing combustor, the ignition from the acceleration of the gas turbine to the no-load rated speed is achieved. In the region where the air flow rate changes drastically, premixed combustion is performed by the pilot premix combustor, and in the region where the air flow rate from the no-load rated speed to the rated load does not change significantly, the pilot premix combustor is used. In addition, premixed combustion is performed by the main premixed combustor, and premixed combustion can be performed from ignition at the time of acceleration of the gas turbine to rated load.

As a result, NOx can be reduced in the entire operating region from ignition to rated load when the gas turbine accelerates.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. FIG. 1 shows a combustor 1 for a gas turbine according to the present invention. The gas turbine combustor shown in the present embodiment is a cone type pilot premix combustor 2, a main premix combustor 3 and a main premix combustor 3 whose cross-sectional area increases from the inlet to the outlet of the combustor, which is a feature of the present invention. It has a fuel nozzle 4.

The air 10 compressed by the compressor passes between the outer casing 5 of the gas turbine combustor and the liner 6 of the gas turbine combustor, and a part of the air 10 enters from the inlet of the main premix combustor 3. , Mixes with the fuel 11 ejected from the fuel nozzle 4, and then flows out from the outlet of the main premixing combustor 3 and burns. The remaining air 10 enters from the inlet of the cone-type pilot premix combustor 2 and mixes with the fuel 11 ejected from the fuel nozzle 4, and then flows out from the outlet of the cone-type pilot premix combustor 2 for combustion. To do. The combustion position in the cone-type pilot premix combustor 2 depends on the air flow rate from ignition at the time of acceleration of the gas turbine to the no-load rated rotation speed. When the air flow rate is low, the cone-type pilot premix combustor 2 Of the cone type pilot premix combustor 2 when the air flow rate is large. This point will be described in detail in FIG. A part of the air 10 is also used for cooling the liner 7 of the cone type pilot premix combustor 2.

FIG. 2 shows an example of the AA cross section of FIG. 1, in which a ring-shaped main premix combustor 3 is provided around the cone type pilot premix combustor 2.
The ring-shaped main premixing combustor 3 is shown in FIG.
It is preferable to install a spacer 8 as shown in FIG. 2 and divide it into several sectors. In this embodiment, since the spacer 8 can be used as a flame stabilizer, flame stability can be achieved. The ring-shaped main premix combustor 3 may be divided into double ring-shaped premix combustors. With this configuration, NOx reduction can be achieved.

FIG. 3 shows another example of the AA cross section of FIG. 1, in which a plurality of cylindrical main premix combustors 3 are provided around the cone type pilot premix combustor 2. It is a thing. The cylindrical main premixing combustor 3 may be doubled.

FIG. 4 shows the characteristics of the cone type pilot premix combustor 2 according to the present invention. That is, when the air flow rate is small (line 41), the area from the inlet of the cone-type pilot premix combustor 2 to the point A where the axial flow velocity V is within the stable combustion range is within the stable combustion range.
Combustion occurs inside the cone-type pilot premix combustor 2 upstream of point A. On the other hand, when the air flow rate is high (line 42), from the point B where the axial velocity V enters the stable combustion range to the outlet of the cone type pilot premix combustor 2 is within the stable combustion range. Therefore, the combustion is downstream from the point B, that is, the cone type pilot premix combustor 2
Happens at the exit of. The change in the axial flow speed changes during the so-called speedup of the gas turbine from the start of the compressor to the steady rotation, and also occurs when the valve (IGV) for adjusting the amount of air taken in by the compressor is adjusted.

FIG. 5 shows a cone type pilot premix combustor 2
FIG. 3 shows an example of the flame holding mechanism of FIG. That is, a swirler 9 for swirling the inflowing air 10 is attached to the inlet of the cone-type pilot premix combustor 2, and the fuel 11 is ejected at the outlet of the swirler 9. The nozzle 4 is attached. in this way,
When a swirl flow is given to the inside of the cone type pilot premix combustor 2, the pressure on the inlet side becomes lower than the pressure on the outlet side in the central portion of the inside of the cone type pilot premix combustor 2 and the flow in the central portion is reduced. A backflow occurs, and as a result, a circulation flow 12 is generated inside the pilot premixing combustor 2 as shown in the figure.
Occurs, and the circulating flow 12 plays a role of flame holding.

Further, the cone type pilot premix combustor 2
Install a premixing chamber at the inlet of the
After the air 10 and the fuel 11 are introduced into the premix chamber, the air 10 and the fuel 11 are premixed in the premix chamber, and then the mixed fuel is caused to flow into the swirler 9 to swirl the mixed fuel to produce a cone. It is made to flow into the type pilot premix combustor 2. In this way, swirling the premixed fuel mixture,
Even if a swirl flow is given to the inside of the cone-type pilot premixed combustor 2, a circulating flow 12 is generated, and this circulating flow 12 plays a role of flame holding.

FIG. 6 shows a cone type pilot premix combustor 2
1 shows an example of a method for cooling the liner 7 of
Fins 21 are provided on the outer wall of the liner 7 in order to improve the cooling capacity. Fins 2 on the outer wall of the liner 7
By installing 1, the convection cooling capacity by the air 10 is improved, so that the capacity of cooling the liner 7 is improved and the temperature of the liner 7 can be lowered. The fins are made of the same material as that used for the main chamber, and 16 fins of about 0.5 to 1 cm are formed in this embodiment.

FIG. 7 shows a cone type pilot premix combustor 2
1 shows an example of a method for cooling the liner 7 of
A turbulence promoter 22 is installed on the outer wall of the liner 7 in order to improve the cooling capacity. By doing so, the convective heat transfer coefficient by the air 10 is improved, so that the ability to cool the liner 7 is improved and the temperature of the liner 7 can be lowered. The turbulence promoter causes turbulence in the air flowing through the outer wall of this liner. It is a so-called turbulent flow promoting body, which produces a vortex and enhances the cooling effect.

FIG. 8 shows a cone type pilot premix combustor 2
1 shows an example of a method for cooling the liner 7 of
In order to improve the cooling capacity and reduce the amount of heat input to the liner 7, the liner 7 is provided with a large number of cooling air holes 23. By forming a large number of cooling air holes 23 in the liner 7, a part of the air 10 flows from the outside to the inside of the cone-type premix combustor 2 to cool the liner 7 and to move the air 10 along the inner wall of the liner 7. Has a film cooling effect, and the liner 7 reduces the heat input to the liner 7.
The temperature can be lowered. The air injected from the outside to the inside is
The outer wall of the liner is cooled by the air stream while flowing along the inner wall of the liner to protect the liner from combustion gases.

FIG. 9 shows a cone type pilot premix combustor 2
1 shows an embodiment for reducing the amount of heat input to the liner 7, in which the inner wall of the liner 7 is provided with a thermal barrier coating (TBC) 24. By providing the thermal barrier coating 24 on the inner wall of the liner 7, the thermal resistance increases, so that the heat input amount from the combustion gas to the liner 7 decreases and the temperature of the liner 7 can be lowered. In particular, it is preferable to use a Ni-based or Co-based ceramic material.

[0025]

According to the present invention, the cone-type pilot premixing combustor stabilizes the premixed fuel even in the region where the air flow rate greatly changes from the acceleration of the gas turbine to the unloaded rated speed. Can be burned. From the unloaded rated speed to the rated load, in addition to the combustion of this cone pilot premix combustor, fuel is also supplied to the main premix combustor arranged around the cone pilot premix combustor. By burning and increasing the fuel, it is possible to deal with the entire region from the acceleration of the gas turbine to the rated load by only the premixed combustion.
Therefore, it is possible to realize a gas turbine combustor in which the amount of NOx generated is extremely small in the entire operating range from ignition during acceleration of the gas turbine to rated load.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a gas turbine combustor showing an embodiment of the present invention.

FIG. 2 is a sectional view of a ring-shaped gas turbine combustor according to the present invention.

FIG. 3 is a sectional view of a cylindrical gas turbine combustor according to the present invention.

FIG. 4 is a characteristic explanatory view of a cone type pilot premix combustor according to the present invention.

FIG. 5 is an explanatory view of a flame holding mechanism of a cone type pilot premixed combustor according to the present invention.

FIG. 6 is a block diagram of a cone pilot premixed combustor with fin cooling according to the present invention.

FIG. 7 is a schematic diagram of a cone type pilot premix combustor with turbulence promoter cooling according to the present invention.

FIG. 8 is a schematic diagram of a cone-type pilot premix combustor having cooling air holes according to the present invention.

FIG. 9 is a block diagram of a cone type pilot premix combustor having a thermal barrier coating according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Combustor for gas turbine, 2 ... Cone type pilot premix combustor, 3 ... Main premix combustor, 4 ... Fuel nozzle, 5 ... Outer cylinder of combustor for gas turbine, 6 ... Combustor for gas turbine Liner, 7 ... Cone type pilot premixed combustor liner, 8 ... Spacer, 9 ... Swirler, 10 ... Air, 11 ... Fuel, 12 ... Circulating flow, 21 ... Fin, 22 ...
Turbulence promoter, 23 ... Cooling air holes, 24
… Thermal barrier coating.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location F23R 3/42 A

Claims (8)

[Claims] 1. A combustor for a gas turbine, comprising a second premixed combustor around a first premixed combustor in which a cross-sectional area from an inlet to an outlet of the combustor is gradually increased. 2. A gas turbine characterized in that a pilot premixing combustor having a cross-sectional area gradually increasing from an inlet to an outlet of the combustor, and a main premixing combustor is installed around the pilot premixing combustor. Combustor. 3. The gas turbine combustor according to claim 1, wherein the first premixed combustor is a cone type pilot premixed combustor having a cylindrical cross section. 4. The gas turbine combustor according to claim 3, wherein the cone-type pilot premixed combustor includes means for imparting swirl to the premixed fuel flowing therein. 5. The gas turbine combustor according to claim 3, wherein the cone-type pilot premixing combustor has fins on the outer wall of the liner. 6. The gas turbine combustor according to claim 3, wherein the cone type pilot premix combustor has a turbulence promoter on an outer wall of the liner. 7. The gas turbine combustor according to claim 3, wherein the cone-type pilot premix combustor has cooling air holes in its liner. 8. The combustor for a gas turbine according to claim 3, wherein the cone-type pilot premix combustor has a thermal barrier coating on the inner wall of the liner.