JPS59129330A - Premixed combustion type gas turbine - Google Patents

Abstract

PURPOSE:To enable to control the fuel-air ratio in the annular part and in the inner tube of a premixing chamber independently of each other and consequently to burn over a wide range in the fuel-air ratio, by a structure wherein a premixing chamber, which is arranged on the upstream side of the liner of a combustor and in which fuel- and-air combustible mixture is formed, is made in a double cylindrical tube structure of an inner and an outer tubes. CONSTITUTION:A portion 41 partitioned in the inner tube 6 of a premixing chamber 4 is so constituted that its cross sectional area is gradually enlarged toward downstream direction. A portion 42 partitioned in the annular portion, which is formed in an annular portion formed by the inner tube 6 and outer tube 7, is also so constituted that its cross sectional area is gradually enlarged toward downstream direction. Due to the structure of the premixing chamber as mentioned above, the flow velocity of combustible mixture in the premixing chamber is resulted in advance to become gradually higher toward upstream direction. Accordingly, when the flow velosity at the outlet of the premixing chamber is set higher than the flow velocity required for the prevention of backfire, flame does not easily propagate toward the upstream side of the premixing chamber, even if backfiring occurs, resulting in further improving the safety against backfire.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a gas turbine combustor, and particularly to a premixed combustion type low NOx combustor that has a large effect of reducing NOx (phonemic oxides).

[Prior art]

NOx generated during the combustion process depends on the combustion gas temperature.

Although it is affected by the oxygen partial pressure and the residence time of the high temperature gas, the combustion gas temperature has the greatest influence, and therefore low temperature combustion is the most effective means for reducing NOx.

Therefore, as a low-Nor technology for gas turbine combustors, a so-called lean combustion method has been developed in which air of a stoichiometric air type or higher is supplied to the combustion region and the air is combusted at a low temperature. However, gas turbine combustors have a very wide operating range from startup to rated load, so if you try to achieve low NOx by sufficiently lean combustion at rated load, the fuel flow rate will decrease even more at partial load or ignition. The extent of p1 lean burn is severely restricted due to the adverse effects of poor ignition, unstable combustion, and an increase in unburned matter. A technique to avoid this restriction is to control the fuel distribution within the combustor and form a locally rich fuel region, thereby creating a stable combustion flame in this region during partial load.
The development of combustion technology that attempts to stabilize the overall combustion (through the flame-holding effect of the combustor) and the so-called multi-combustion method that divides and supplies fuel downstream of the combustor.

is in progress. However, these lean burn systems rely on diffusion combustion in which fuel and air are supplied separately into the combustor and burned while being mixed within the combustor, so it is inevitable that the air-fuel mixture close to the stoichiometric mixture locally will be mixed. It has the fatal disadvantage of generating combustion hot spots where a high degree of NOx is generated. Therefore, with this method, the resulting reduction in NOx is approximately 5 times lower than that of a conventional standard combustor.
This is about a 0% reduction. Therefore, in order to achieve the greatest reduction in NOx, a low NOx combustor using the so-called mixed combustion method is promising, which eliminates the hot spots mentioned above by performing combustion after the formation of a homogeneous mixture. I'll go.

However, problems still remain in applying the premix combustion method to a gas turbine combustor and thereby achieving ultra-low NOx. In the case of a premixture, there is a range of non-flammable mixtures and there is a risk of flame backfiring into the premixing chamber.

The latter problem of backfire can be solved in principle by setting the flow velocity of the air-fuel mixture to be sufficiently higher than the combustion speed of the air-fuel mixture, regardless of the specific device configuration. Therefore, in applying the premix combustion method to a gas turbine combustor with a wide operating range, the biggest challenge is the former problem, that is, achieving stable combustion of the premix combustion flame over a wide operating range.

[Purpose and outline of the invention]

The present invention is based on the above-mentioned Ni1. This was done to solve the problem. A premixing chamber was installed upstream of the combustion chamber, and
In addition, the premixing chamber has a double cylindrical structure, and the mixing tube has a structure that achieves a sufficient level of stability.This structure improves the thermal flame stabilization effect of the flame, and also allows the premixing chamber to have a double cylindrical structure. By making it possible to control the concentration of the flammable mixture flowing out, stable combustion of the lean premixture can be achieved over a wide range.

[Embodiments of the invention]

An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows an example of the implementation of the present invention, in which this gas turbine combustor comprises a mixing chamber 4 for forming a combustible mixture of fuel and air on the upstream side of the combustor liner, and the premixing chamber A combustor liner 5 is connected to the downstream side of the combustor liner 5. This premixing chamber 4 has a double cylindrical shape with an inner cylinder 6 and an outer cylinder 7. The annular portion 42 defined by the cylinder 6 and the outer cylinder 7 of the premixing chamber 4 has a plurality of cylinder fuel nozzles 1 having an air swirler 15 concentrically therein.
The inner cylinder 6 is provided with at least one fuel nozzle 12 having an air swirler 13 concentrically therein. Furthermore, a multi-tube fuel nozzle 10 has an air swirler 11 concentrically on the peripheral wall near the connection between the premixing chamber 4 and the combustion chamber litchi 5.
It consists of the following.

By adopting such a configuration, the gas turbine is operated by supplying fuel to the fuel nozzle 0 provided in the combustion chamber liner 5 from ignition and startup to partial load, and from high load to rated load range, the premixing chamber is used. 4 can be operated by supplying fuel to the fuel nozzles 12 and 14 provided in the fuel nozzles 12 and 14, and therefore stable combustion over a wide range can be achieved.

More specifically, the specific configuration of this embodiment is as follows. In other words, in a premix combustion type gas turbine combustor, basically, the combustion chamber liner 5 and the premix chamber outer cylinder 7 are housed by the combustor outer cylinder 1 and the cover 2, and the compressor pressurizes the compressor. The air 100 flows upstream between the combustor outer cylinder 1, the combustor liner 5, and the premixing chamber outer cylinder 7, while flowing from the air supply holes or air swirler provided in the combustion chamber liner 5 and the premixing chamber 4, respectively. It is of the type that flows inside.

In this basic configuration, the premixing chamber 4 has a premixing chamber cylinder 6.
It has a double cylindrical structure consisting of a combination of and a premixing chamber outer cylinder 7,
An air swirler 13 is installed concentrically in the inner cylinder 6 at the upstream end of the double cylinder.
A secondary fuel inner cylinder fuel nozzle 12 having
A plurality of secondary fuel annular fuel nozzles 14 having a diameter of 5 are arranged in a plurality of cylinders.

In this example, the combustion chamber liner 5 has a diameter larger than that of the premixing chamber outer cylinder 7, and is connected to the downstream side of the premixing chamber outer cylinder 7 by an enlarged portion 8. A primary fuel nozzle 1 with a primary fuel nozzle air swirler 11 arranged concentrically on the peripheral wall of this enlarged portion 8
0f: Arrange multiple items.

In such a combustor configuration, ignition and startup of the gas turbine is performed as follows. - Primary fuel 107 to primary fuel supply pipe 1
The fuel is supplied to a plurality of primary fuel nozzles 10 provided in the enlarged portion 8 through a secondary fuel distribution pipe 17, and this fuel is ignited by a spark plug 22 provided downstream of the primary fuel nozzle 10. Ru. This flame is combusted by the swirling air flow supplied from the primary fuel nozzle wall swirler 11 provided on the outer periphery of each primary fuel nozzle 10, and stable combustion is achieved by the presence flow partially stratified by this swirling air flow. do. -Next fuel nozzle 1
The flame formed in the combustion chamber 3 by the combustion chamber 3 is a collective flame of individual flames formed by the plurality of primary fuel nozzles 10. However, in the vicinity of the primary fuel nozzle 10, a single flame stabilized by each fuel nozzle 10 and air swirler 11 is formed. - The flames combine on the downstream side of the fuel nozzle 10 to form a ring-shaped flame that surrounds the entire premixing chamber 4. The gas turbine is operated using only this primary fuel 107 from ignition startup to partial load.

When the gas turbine shifts to high load operation, the secondary fuel 108 is supplied to the secondary fuel supply pipe 18 and the secondary fuel annulus fuel nozzle 14. Secondary fuel 10 supplied to such premixing chamber 4
8 is mixed with air supplied to an air swirler 13.15 provided in each fuel nozzle 12.14 to form a combustible mixture 105.106 which is supplied to the combustion chamber liner 3. These combustible mixtures are ignited by the above-mentioned primary contact, and a stable premixed combustion flame is formed by the thermal flame-holding effect of the ring-shaped flame. In this case, ignition of the premixture first occurs in the root combustible mixture 112 flowing out close to the ring-shaped flame, and then the inner cylinder combustible mixture 111 is ignited by flame propagation within the combustible mixture. ignite. Therefore, in order to achieve early ignition and stable combustion of the lean premixture, which has been a problem in the past, it is necessary to make the ignition region of the premixture a mixture that is easy to ignite. One advantage is to set the fuel-air ratio condition to enable early ignition of the annular part combustible mixture 112 that is close to the ring-shaped flame that is the source.

That is, one of the main points of the present invention is that the premixing chamber structure has a double cylindrical structure in order to realize early ignition of a lean combustible mixture. The fuel mixture 111 is thin in fuel, and the mixture 112 on the outside between the inner cylinder 6 and the outer cylinder 7 is rich in fuel. The fuel-to-fuel ratio of the combustible mixture 112 in the cylindrical portion is also set to be larger than that of the combustible mixture 111 in the cylindrical portion.

In this case, in order to achieve a significant KNOx conversion through lean premix combustion and to achieve stable combustion over a wide operating range as a gas turbine combustor, it is necessary to
12 is set to 0.040 to 0.07, and the fuel air ratio of the cylindrical combustible mixture 111 is set to 0.03 to 0.06. More preferably, the fuel-air ratio of the annular portion combustible mixture 112 is set to 0.04 to 0.05 under the rated operating conditions of the gas turbine.
The fuel-air ratio f of the combustible mixture 111 at the circle' node is 0.03.
~0.04. In this range, the generation of NOx is minimal, and the liquid is suitable for good ignition and maintaining good flame stability.

FIG. 3 explains an example of the fuel injection method in this example. The primary fuel Fl for p1 gas turbine load
(the fuel indicated by the reference numeral 107) and the secondary fuel F2 (
This shows the flow rate of the fuel (denoted by the reference numeral 108). That is, the gas turbine is operated with only the primary fuel Fs in the partial load region from the start of the gas turbine, and the load increase is compensated for in the high load region of the gas turbine by supplying the secondary fuel P1. The injection timing of secondary fuel F is when the gas turbine load is 5.
It is preferable to perform this between 0 and 75 inches, and furthermore, at one rated load, the primary fuel Fl is decreased and the premix combustion ratio of the secondary fuel F is increased. This reduces the amount of primary fuel Ft' which is diffuse combustion, and conversely increases the premix combustion ratio to achieve low NOx. Specifically, the primary fuel Ft at the time of rating is 10 to 40 inches, and the secondary fuel F2 is 60 inches.
It is desirable to set it to ~90 Qin. Furthermore, in order to quickly ignite and stably burn the premixed flame when the secondary fuel is introduced, there is also an operation method in which the secondary fuel F2 is introduced in k steps.

When this method is adopted, in order to avoid sudden changes in the output of the gas turbine, the secondary fuel should be reduced stepwise by the same amount as the secondary fuel flow rate, which is injected stepwise. Make it. By using such a fuel injection method, the combustion characteristics of the combustor of this example when secondary fuel is input are significantly improved. In addition, the flow velocity of the combustible mixture in the premixing chamber must be approximately one order of magnitude faster than the combustion rate of the combustible mixture in order to prevent the flame from backfiring into the premixing chamber. The flow velocity of the mixture 111 and 112 is approximately 20 m
/s or more.

As explained above, in this embodiment, the premixing chamber 4 having a double cylindrical structure is provided on the upstream side of the combustion chamber liner 5 provided on the entire peripheral wall of the diffusion combustion burner, and the combustible mixture in the annular part 42 of the premixing chamber and the cylindrical part 41 are provided. By separately controlling the fuel-air ratio of each combustible mixture, it is possible to achieve stable combustion and low NOx combustion over a wide range of lean combustible mixtures.

FIG. 2 shows another example of the present invention, in which a portion 41 defined within the inner cylinder 6 of the premixing chamber 4 has a structure in which the area gradually increases toward the downstream side, and the inner surface 6 In this embodiment, a portion 42 defined within the annular body portion formed by the outer cylinder 7 and the outer cylinder 7 also gradually increases in area toward the downstream side. Specifically, in this example, in the structure of the pipe that widens toward the downstream side, the premixing chamber cylinder 6 and the outer cylinder 7 are provided with an auxiliary inner cylinder 23 and an auxiliary cone 24 whose area gradually increases toward the downstream side. This is achieved by providing To avoid this, in this example, a 7-shaped vortex generator 25 is provided at the downstream end of the premixing chamber inner cylinder 6. With such a premixing chamber structure, first, the combustible air mixture flow in the premixing chamber is made to gradually increase in flow velocity toward the upstream side. Therefore, if the flow velocity at the outlet of the premixing chamber is set to a value higher than the flow velocity for preventing flashback described above, even if flashback occurs, the flame will not be easily transmitted to the upstream side of the premixing chamber.
Safety against backfire is further improved. Also, the vortex generator 2
5, a vortex 115 is formed in its wake. This promotes turbulent eddy mixing and significantly speeds up the flame propagation of the premixed flame upon ignition. Furthermore, since the downstream flow of the vortex generator 25 is made into a low-velocity flow, flame stabilization can be improved. Even if this vortex generator 25 is added to the example shown in FIG. 1, the same effect can be achieved.

In addition to the effects of the example shown in FIG.
The surface of the premixing chamber 4 [-the area is gradually expanded toward the downstream,
Furthermore, by providing the vortex generator 25 at the outlet of the premixing chamber 4, flashback can be prevented reliably, and the ignition and stabilization of the lean premixture can be improved.

〔Effect of the invention〕

As described above, in the gas turbine combustor of the present invention, the premixing chamber for forming a combustible mixture of fuel and air provided upstream of the combustor liner has a double cylindrical structure with an inner cylinder and an outer cylinder. Therefore, the fuel-air ratio can be controlled by dividing the combustible mixture between the annular part and the inner cylindrical part of the premixing chamber. Also,
Annular part, inner cylinder.

Since an air swirler is provided on each wall near the connection between the premixing chamber and the combustor liner, sufficient equalization of each air-fuel mixture can be achieved. Therefore, these effects enable stable combustion of a lean combustible mixture over a wide range and low NOx combustion.

It should be noted that, although the illustrated embodiment has many other effects, the present invention is not limited to the illustrated example.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an example of the implementation of the present invention. FIG. 2 is a schematic cross-sectional view showing another embodiment of the present invention. FIG. 3 is an explanatory diagram schematically showing a fuel injection plan. 3... Combustion chamber, 4... Premixing chamber, 41... Part formed by inner cylinder, 42... Annular part, 5... Combustion chamber liner, 6... Premixing chamber cylinder , 7... Premixing chamber outer cylinder,
8...Connection part, 10...-Next fuel nozzle, 11...
- Secondary fuel nozzle air swirler, 12...Fuel nozzle for secondary fuel inner cylinder, 13...Fuel nozzle air swirler for secondary fuel inner cylinder, 14...Fuel nozzle for secondary fuel annular part ,1
5...Fuel nozzle air swirler for secondary fuel annular portion, 16
...-Secondary fuel supply pipe, 18...Secondary fuel supply pipe, 2
3 River auxiliary inner cylinder, 24... Auxiliary cone, 25... Eddy current generator. Agent: Masami Akimoto, Patent Attorney No. 2, No. 3 J゛Sypinkariima (%p Continued from Page 1 0) Author: Fumio Kato, 502 Kandate-cho, Tsuchiura City, Hitachi, Ltd. Mechanical Research Laboratory

Claims (1)

[Claims] 1. Gas turbine combustion comprising a premixing chamber for forming a combustible mixture of fuel and air on the upstream side of the combustor liner, and a combustor liner connected to the downstream side of the premixing chamber. In the container, the premixer has a double cylindrical shape with an inner tube and an outer tube, and a plurality of fuel nozzles with concentric air swirlers are installed in the annular portion formed by the inner tube and the outer tube. At least one fuel nozzle having an air swirler arranged concentrically is provided in the fuel nozzle, and a multi-sided fuel nozzle having an air swirler arranged concentrically is provided on the circumferential wall near the connection between the premixing chamber and the combustor liner. 1. A premix combustion type gas turbine combustor, characterized in that the premix combustion type gas turbine combustor is provided. 2. A premix combustion type gas turbine combustor according to claim 1, wherein the combustor liner has a diameter larger than the premix chamber. 3. In claim 1 or 2, the area defined within the inner cylinder of the premixing chamber is configured to gradually expand in area toward the downstream side, and the area defined by the inner cylinder and the outer cylinder are A premix combustion type gas turbine combustor, characterized in that the area defined within the formed annular portion also gradually increases in area toward the downstream side. 4. In claim 3, the portion defined within the inner cylinder has a double area enlargement structure by providing the inner cylinder with an auxiliary cone whose area gradually increases toward the downstream side. This can be achieved by providing an annular auxiliary inner cylinder whose area gradually increases toward the downstream side in the part defined by the annular part formed by the inner cylinder and the outer cylinder. A premixed combustion gas turbine combustor that achieves the configuration. 5. A premix combustion type gas turbine combustor, characterized in that a V-shaped vortex generator is provided at the downstream end of the inner cylinder of the premix chamber in any one of the first to fourth % tolerance requirements. 6. In any one of claims 1 to 5, the fuel flow rate of a fuel nozzle provided in a combustor liner and the air amount ratio '? r: 0°03 to 0.06, the ratio of the fuel flow rate supplied to the annular part of the premixing chamber to the amount of air flowing into the annular part to 0.045 to 0.07, and the inner cylinder of the premixing chamber The ratio of the fuel flow rate to be supplied and the amount of air flowing into the inner cylinder section is set to 0.
03 to 0.06. A premix combustion type gas turbine combustor.