JPH0745935B2 - Low NOx gas turbine combustor - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a two-stage combustion type low NOx gas turbine combustor,
In particular, the present invention relates to a gas turbine combustor in which the second stage combustion performance is improved and the low NOx effect is enhanced.

[Background of the Invention]

NO as an air pollutant as one of the environmental problems of gas turbines
x occurs. This is generated by the oxidation of nitrogen in the combustion air in the combustion flame of the gas turbine. Also, if the fuel contains nitrogen, it will be oxidized.
It becomes NOx. In the case of a gas turbine, a fuel containing a relatively small amount of nitrogen in the fuel is used, so most of NOx is due to the oxidation of nitrogen in the combustion air.

Therefore, reduction of NOx in the gas turbine combustor is achieved by low-temperature combustion to suppress nitrogen oxidation. As a concrete method of this, there are a conventional method of injecting water or steam into the combustor and a combustion control method based on lean combustion. In the former case, the thermal efficiency is lowered and auxiliary machinery is required. Therefore, the latter combustion control method is becoming mainstream these days.

The following two points are important for reducing NOx by lean combustion. That is, (1) achieving uniform low temperature combustion, and (2) achieving stable combustion over a wide operating range. As a solution to (1), it is possible to solve the problem by changing from the conventional diffusion combustion to the premixed combustion.
With regard to (2), there is a method in which multi-stage combustion of fuel and the amount of combustion air are controlled by the load of the gas turbine to appropriately adjust the fuel-air ratio in the combustion region. Especially when premixed combustion is used, there is a non-combustion air ratio zone. Therefore, when using this for a gas turbine combustor with a wide operating fuel injection range, the first stage is diffused to supplement the operating range. The two-stage combustion method, in which the combustion and the second stage are premixed combustion, is rational and is the mainstream of current technological development.

Examples of such a two-stage combustion system include Japanese Patent Publication No. 58-58563, Japanese Utility Model Publication No. 59-55267, and US Pat.
There are 260 etc. In the two-stage combustor in which the second stage is premixed combustion, as described above, in order to bring premixed combustion into a good combustion state, it is necessary to burn at a certain predetermined air-fuel ratio or more. Therefore, there is a problem that the performance is remarkably deteriorated when the flow rate of the premixed fuel in the second stage is small and when the fuel is switched from the first stage to the second stage.

[Object of the Invention]

An object of the present invention is to provide good combustion performance in a two-stage combustion type low NOx gas turbine combustor in which a small amount of unburned matter is generated in a small flow rate range of the second stage fuel including the time of introducing the second stage fuel. Moreover, it is to provide a combustor structure that promotes low NOx combustion in a large flow range of the second stage fuel.

[Outline of Invention]

Before explaining the outline of the present invention created to achieve the above object, first, the basic principle thereof will be described below.

The gist of the present invention is to adjust the concentration distribution of the combustible mixture and supply it to the combustion chamber by making the fuel injection position variable according to the fuel flow rate. More specifically, fuel is injected from the outlet side of the combustion air flow path in the low combustion flow rate range to increase the rich flame of combustible material concentration, and conversely, the high fuel flow rate range is in the upstream side of the combustion air flow path. The fuel is injected from the side to be supplied as a uniform combustible mixture.

In order to achieve the above-mentioned object based on the above principle, the low NOx gas turbine combustor according to the present invention has a second-stage fuel nozzle in which the injection holes are arranged in the downstream portion in the second-stage combustion air passage. The first fuel pipe and the second fuel pipe having the injection holes arranged upstream in the two-stage combustion air flow path, and the fuel distributor is 1 in the state from ignition of the gas turbine to partial load.
Fuel is supplied to the first-stage combustion section by the first-stage fuel nozzle according to the output of the gas turbine, and when the output of the gas turbine reaches the intermediate load zone, the fuel supply by the first-stage fuel nozzle is reduced stepwise. , By the first fuel pipe 2
The stage fuel is supplied to the downstream side in the second-stage combustion air flow passage, and the fuel supply by the first fuel pipe is gradually increased together with the fuel supply by the first-stage fuel nozzle according to the intermediate load zone of the gas turbine. When the turbine output reaches from the intermediate load zone to the high load zone, the fuel supply by the first fuel pipe is reduced, while the second stage fuel is supplied by the second fuel pipe.
The fuel is supplied to the upstream side in the staged combustion air flow path, and the fuel supply by the second fuel pipe is controlled to be gradually increased together with the fuel supply by the first stage fuel nozzle according to the high load zone of the gas turbine. To do.

Example of Invention

An embodiment of the present invention will now be described with reference to the accompanying drawings. The present embodiment is an example improved by applying the present invention to a combustor of a gas turbine for power generation.

FIG. 1 is a sectional view of this embodiment. The combustor 2 is a back-flow can type, and the compressed air 101 supplied from the compressor 1 flows between the combustor outer cylinder 25 and the combustor liner 5, and also between the combustor liner 5 and the combustor liner 6, respectively. It enters the inside of the combustor 2 through an inflow means such as an air hole provided. This air is 1
Generate a high-temperature working gas 110 through a combustion reaction with the fuel
This is supplied to the turbine 3 via the transition piece 27.

The combustor 2 has a small-diameter sub-chamber liner 6 on the upstream side, a large-diameter main chamber liner 5 on the downstream side, and is provided with a second-stage combustion air flow passage 9 defined at the connecting portion. Combustion pores 8 and 8'on the wall surface of the sub-chamber liner 6, and liner cap 7
A swirler 11 is provided in the. A first-stage fuel nozzle 12 is attached to substantially the center of the liner cap 7, and the sub-chamber liner 6 forms a first-stage combustion section 2 '. on the other hand,
Inside the second-stage combustion air channel 9, a plurality of second-stage fuel nozzles 14 are mounted at substantially equal intervals on the same circumference of the air channel, and a combustible mixture is formed in this air channel. Are supplied to the second-stage combustion section 2 ″. More specifically, the second-stage fuel nozzle 14 is composed of two systems including a first flow passage 15 and a second flow passage 18, and has a first injection hole 17 and a second injection passage 17, respectively. The fuel is supplied from the second injection hole 20.

FIG. 2 shows a detailed cross section of the second stage fuel nozzle, and FIG. 3 shows (A) to (A ′) cross sections of FIG. The structure of the second stage fuel nozzle 14 will be described with reference to FIGS. 2 and 3.

A plurality of air passage windows 32 are provided in the fuel supply flange 12 supported by the combustor outer cylinders 25 ', 25 "described with reference to FIG. And the second
A flow path 18 is provided. The plurality of first flow paths 15 and second flow paths 18
And are communicated with the fuel headers 16 and 19 partitioned by the partition plate 33, respectively.

A plurality of second stage fuel nozzles 14 are attached to the fuel header section. The second stage fuel nozzle 14 is the first fuel pipe 28.
By coaxially combining the second fuel pipe 29 with the second fuel pipe 29, the first fuel pipe 28 extends to the downstream side of the second-stage combustion air flow passage 9, the tip of which has a closed structure, and the first injection pipe is provided at the end. A hole 17 is provided. The second fuel pipe 29 is the second stage combustion air flow passage 9
A second injection hole 20 is provided at the upstream end side of which has a closed structure. That is, in the second-stage combustion air flow passage 9, the first injection hole 17 is arranged at the upstream portion and the second injection hole 17 is provided at the downstream portion.
The injection hole 20 is arranged.

In such a combustor structure (see FIG. 1), the compressed air 101 supplied from the compressor 1 is diluted air 102 from the dilution air hole 10 provided in the main chamber liner 5, and the diluted air 102 is supplied from the second-stage combustion air passage 9. The second-stage combustion air 103 and the remaining air are supplied to the sub-chamber liner 6 side through the air passage window 32 (FIG. 3) provided in the fuel supply flange 12, and the first-stage combustion air 105, 105 respectively. ′ And 106 are supplied into the first-stage combustion section 2 ′. On the other hand, the fuel 200 is distributed and supplied to the first stage fuel (F ₁ ) 22, the sub second stage fuel (F ₂ ′) 23 and the main second stage fuel (F ₂ ) 24 by the fuel distributor 34, respectively. . The fuel flow rate and the fuel distribution ratio are controlled by a fuel control signal 300 preset according to the output of the gas turbine. From the ignition start of the gas turbine to the light output, the first stage fuel (F ₁ ) 22
The second stage fuel is first supplied by the sub second stage fuel (F ₂ ′) 23 before the second stage fuel is supplied on the high output side including the rated output. supplied Te is sub second stage fuel in upon reaching a predetermined output (F ₂ ') 23 is switched to the main second stage fuel (F ₂₎ 24. FIG. 4 shows the fuel injection method. Only the gas turbine load operation is shown in the figure, but only the first stage fuel (F ₁ ) is operated from the ignition start of the gas turbine to about 25% output. The first-stage fuel is basically a diffusion fuel, and the working twist / air ratio band in the first-stage combustion region is set to 0.005 to 0.02. At an output of 25%, the fuel-air ratio in the first stage combustion area is about 0.02. In this state, while making the total fuel flow rate to match the total fuel curve shown by the chain line in FIG. 4, the first stage fuel green (F ₁ ) is reduced stepwise (point D) and the sub second stage The fuel (F ₂ ′) is injected stepwise (point U), and the second stage combustion is performed. Since this second-stage combustion is ignited by the flame propagation from the first-stage combustion flame, the conditions for maintaining good combustion in the second-stage and maintaining stable combustion are the first-stage combustion. It is affected by the flame temperature, the second-stage fuel-air ratio, and the mixed state of the second-stage fuel and the second-stage combustion air. That is, the higher the combustion flame temperature in the first stage and the more uneven the mixed state of the fuel in the second stage, the more the second stage combustion can be ignited at a smaller combustion flow rate. However, the greater the non-uniformity of the concentration distribution of the two-stage fuel, the greater the generation of NOx, so it is important to set appropriate conditions. Here, based on various experimental studies, it is necessary to make the step input amount of the secondary second-stage fuel (F ₂ ′) about 0.03 or more in the fuel-air ratio expressed by the ratio with the second-stage combustion air. On the other hand, at this time, the fuel-air ratio of the first-stage combustion part reduced to the step-like state is 0.05% as described above.
It is necessary to be above. After switching fuel, first stage fuel, sub 2
When the second stage fuel is increased by increasing the second stage fuel to increase the gas turbine output and reaching the high load zone, that is, at the output of about 60%, the second stage fuel is switched. This is achieved by introducing the main second stage fuel (F ₂ ) while keeping the total fuel flow rate constant and reducing the sub second stage fuel (F ₂ ′) by the fuel distributor 34. To be done. By this operation, the second stage fuel is 2
It is injected into the upstream portion of the stage combustion air flow path 9 and is supplied to the stage 2 combustion chamber as a sufficiently homogeneous mixture with the stage 2 combustion air.
Burns at a uniform flame temperature, resulting in lower NOx combustion. Stable low N when the fuel-air ratio after switching the second stage fuel is 0.035 or more
Ox combustion can be realized, and the upper limit is preferably 0.045 or more. As described above, when the gas turbine of the embodiment reaches the intermediate load zone (when the load is low), the fuel distributor 34 lowers the fuel supply from the first-stage fuel nozzle 12 in a stepwise manner, while the second-stage fuel nozzle 2 by 14 first fuel pipes 28
Switching to supply the stage fuel to the downstream side of the second-stage combustion air flow passage 9 and the fuel supply by the first fuel pipe 28,
Fuel is supplied from the first-stage fuel nozzle 12 It gradually increases with the fuel supply from the first-stage fuel nozzle 12 according to the intermediate load zone of the gas turbine. Therefore, the fuel concentration distribution has a shade, and the mixture is burned reliably with a rich combustion concentration. Therefore, even when the transition to the second-stage combustion is performed and the second-stage fuel flow rate is small, stable combustion can be performed as a whole, and the combustion performance is improved.

Moreover, when the gas turbine reaches the high load zone from the intermediate load zone, the fuel supply by the first fuel pipe 28 is reduced, while the second fuel pipe 29 causes the first stage fuel to flow into the second stage combustion air flow passage 9. The fuel supply by the second fuel pipe is gradually increased together with the fuel supply by the first-stage fuel nozzle according to the high load zone of the gas turbine, so that a more uniform mixture is burned at high load. Low NOx combustion can be realized by supplying it to the room and burning it.

FIG. 5 and FIG. 6 show an embodiment different from the above. In the embodiment of FIG. 5, the second-stage combustion is performed from the first fuel header 16 and the second fuel header 19 via the sub-second fuel pipe 32 and the main second-stage fuel pipe 33, respectively, in the second-stage combustion air flow path. A plurality of first injection holes 17 and second injection holes 20 which are provided in the inner peripheral wall and are guided to the auxiliary fuel headers 35, 36 and are formed in the inner peripheral wall.
It supplies more fuel. In the case of such a structure, the secondary second-stage fuel is injected on the side closer to the first-stage combustion flame to improve ignition, and a fuel nozzle is not required, which is structurally simple. The embodiment of FIG. 6 is mainly 2
The stage fuel is supplied from the second injection hole 20 provided near the upstream end of the outer peripheral wall 30 of the second stage combustion air flow passage 9. With this structure, the mixed state of the main second-stage fuel and air becomes leaner toward the inner peripheral side, and the low NOx effect is enhanced.

〔The invention's effect〕

As described above, when the low NOx gas turbine combustor of the present invention is switched to the two-stage combustion and when the second stage fuel flow rate is small, the fuel can be supplied into the combustor with a different concentration, so that the two-stage combustion is possible. The ignition range and the good combustion range of the eye combustion are expanded, and it becomes possible to shift to the second stage combustion at the lighter load side, and the combustion performance is improved, especially the unburned content after fuel switching is suppressed. It Furthermore, by switching the second stage fuel on the high load side, it is possible to burn a homogeneous air-fuel mixture and achieve low NOx. Therefore, according to the present invention, it is possible to achieve both stability of combustion at low load and low NOx at high load.

[Brief description of drawings]

FIG. 1 is a sectional view of one embodiment of the present invention, and FIG. 2 is an enlarged detailed sectional view of the vicinity of the second stage fuel nozzle in the above embodiment,
FIG. 3 is a sectional view taken along line (A)-(A ′) of FIG. 2, FIG. 4 is a table showing the fuel flow rate ratio in the above embodiment, and FIGS. 5 and 6 are respectively different embodiments. FIG. 3 is a cross-sectional view of the vicinity of a second stage fuel nozzle. 2 ... Combustor, 5 ... Main chamber liner, 6 ... Sub chamber liner,
9: 2nd stage combustion air flow path, 12: 1st stage fuel nozzle,
14 …… Second stage fuel nozzle, 17 …… Second stage first injection hole, 20…
… Second stage second injection hole, 25 …… Combustor outer cylinder, 28 …… First fuel pipe, 29 …… Second fuel pipe, 34 …… Fuel distributor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshihiro Uchiyama 502 Jinritsu-cho, Tsuchiura-shi, Ibaraki Machinery Research Institute, Hiritsu Manufacturing Co., Ltd. (72) Inventor Nobuyuki Iizuka 3-1-1, Saicho-cho, Hitachi, Ibaraki Stock Hitachi, Ltd., Hitachi Plant (72) Inventor, Katsuo Wada 3-1-1, Saiwaicho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd., Hitachi Plant

Claims (2)

[Claims] 1. A combustor outer cylinder, a sub-chamber liner provided inside the combustor outer cylinder and provided with combustion air holes, and a first-stage fuel for supplying a first-stage fuel near the upstream end of the sub-chamber liner. The first-stage combustion section formed by the eye fuel nozzle, the second-stage combustion section formed by the main chamber liner connected to the downstream side of the sub-chamber liner and provided with dilution air holes, and the downstream side of the sub-chamber liner. A two-stage combustion air flow path that is partitioned along the outer peripheral wall, axially communicates with the upstream side in the two-stage combustion section of the main chamber liner, and that supplies compressed air to the main chamber liner, and the two-stage combustion A plurality of second-stage fuel nozzles provided in the air flow path, a first-stage fuel nozzle, and a fuel distributor for controlling the second-stage fuel nozzle are provided, and the first-stage is subjected to diffusion combustion and second-stage. In a gas turbine combustor with premixed combustion in the eyes, each of the second-stage fuel nozzles is Is composed of a first fuel pipe arranged downstream in the two-stage combustion air flow passage and a second fuel pipe arranged in the injection hole upstream in the two-stage combustion air flow passage, and the fuel distributor is In the state from ignition to partial load of the gas turbine, fuel is supplied to the first-stage combustion section by the first-stage fuel nozzle according to the output of the gas turbine, and when the output of the gas turbine reaches the intermediate load zone, the first-stage The fuel supply from the second fuel nozzle is reduced stepwise, while the second fuel is supplied to the downstream side in the second fuel air passage by the first fuel pipe,
The fuel supply by the first fuel pipe is gradually increased together with the fuel supply by the first-stage fuel nozzle according to the intermediate load zone of the gas turbine, and further, when the gas turbine output reaches the high load zone from the intermediate load zone, While reducing the fuel supply by the fuel pipe, the second fuel pipe supplies the second-stage fuel to the upstream side in the second-stage fuel air flow path, and the fuel supply by the second fuel pipe is set in the high load zone of the gas turbine. A low NOx gas turbine combustor characterized by performing switching control so as to gradually increase with fuel supply from the first stage fuel nozzle. 2. The first fuel pipe and the second fuel pipe of the second stage fuel nozzle have a double tubular structure coaxial with each other, and the tip of the second fuel pipe is in close contact with the first fuel pipe. In addition, the first fuel pipe has a nozzle hole at its tip, and the first fuel pipe projects from the tip of the second fuel pipe and has a nozzle hole at its tip. The low NOx gas turbine combustor according to claim 1, wherein each of the first and second fuel pipes is connected to two independent fuel headers.