JPH0621571B2 - Gas turbine combustor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a gas turbine combustor, and in particular, nitrogen oxide (NOx) which is an air pollutant and carbon monoxide (CO) which is an unburned emission. The present invention relates to a premix multistage combustor capable of suppressing the generation of hydrocarbons (HC) and the like.

[Conventional technology]

A specific example (U.S.P. 4292801) which is a conventional premixed combustion method for a gas turbine combustor will be described. This combustor has a first-stage fuel nozzle on its head, has a plurality of partitioned combustion chambers, and has a second-stage fuel nozzle that is formed to project in the central portion on the downstream side, and its outer periphery. It is composed of a combustion chamber with a part of the side narrowed. During operation, fuel is introduced from the first-stage nozzle to ignite, second-stage fuel is introduced, the first-stage fuel is temporarily shut off, and the second-stage fuel is ignited. Further, the first stage fuel is introduced to premix the fuel and air to continue combustion with the second stage flame. However, if the amount of fuel in the first stage is increased, the amount of NOx produced decreases, but there is a flashback region, and there is extreme CO generation in the range where the premixed fuel ratio is small. Therefore, in the gas turbine combustion operation region, when the combustion load control is performed for a constant amount of combustion air, lean combustion occurs on the low load side, and it is difficult to reduce NOx by premixed combustion. Particularly, conventionally, no consideration has been given to the expansion of the premixed combustion operation region according to the combustion load zone, the controlled combustion at the time of switching from the first stage to the second stage, and the like.

[Problems to be solved by the invention]

In the case of gas turbine combustion, a relatively large amount of air flows with respect to the fuel, so if optimum premixing of air and fuel is set under rated load conditions, regardless of the degree of premixing on the low load side with less fuel , The combustion on the lean side. As means for this combustion region, conventionally, diffusion combustion by introducing fuel dispersion in the first stage is performed and a high-load second-stage premixed combustion system is adopted. However, since the premixed combustion range is narrow, ultra-low NOx reduction cannot be expected, and it is structurally difficult to suppress CO generation during partial load. In particular, in the two-stage combustion system, the ratio of diffusion combustion and premixed combustion is an extremely important factor for the NOx and CO production amounts, and if the premixed combustion region is narrow, low NOx is produced.
It is disadvantageous to chemical combustion, and it is necessary to solve the problems of fire transfer and unstable combustion when switching from the first stage to the second stage.

The object of the present invention relates to a method of expanding a combustion range by suppressing the degree of premixing in a premixed combustion system and performing low NOx combustion that matches exhaust gas characteristics in a combustion load zone.

[Means for solving problems]

The above-mentioned object is to match the gas turbine combustion operating region, to form a shade in the mixing pattern of the combustible mixture when the load is low, and to freely suppress the fuel that can be uniformly mixed when the load is high. As a means for achieving premixed combustion, the premixed gas is multistaged in the axial direction of the combustion chamber to achieve a uniform low temperature by dispersing the flame. Next, the fuel introduction mechanism into the combustion chamber divides the air flow passage on the upstream side of the injection port, arranges a large number of fuel introduction holes and fuel introduction pipes with injection holes in each flow passage, To change the fuel concentration. In addition, the fuel flow rate of each stage can be automatically controlled through a regulator. Further, the first-stage fuel introduction region is operated from ignition to low load, and the second-stage operation region is from partial load to rated negative load. In particular, when introducing the premixing of each stage, the fuel introduction mechanism of the injection port is operated to form the density of the premixed fuel in the lean side combustion, and the combustion is continued at the fuel concentration in the homogenizing direction at the time of high load. NOx, C
O is suppressed at the same time.

[Action]

In the premixing process of fuel and air, it is very advantageous to expand the premixed combustion region and stabilize the fuel by enabling the concentration field of the fuel to be suppressed in accordance with the combustion load zone. For example, when a relatively small amount of fuel is introduced into a region where the air amount is constant, and a concentration is formed in the premixed fuel, a flame is generated if the rich region is in the combustible range, and as the temperature rises, Combustion of the surrounding lean combustible mixture is promoted.

On the other hand, on the high load side, the amount of fuel becomes large, so premixing is strengthened and uniform low temperature combustion is enabled. The homogenized mixing of fuels is the most effective method for low NOx combustion, and CO
It is also effective in suppressing. In addition, even when forming a shade in the fuel concentration field, avoid forming it in a portion where the fuel is extremely rich (fuel only) or in a light area (only air), and it is possible to introduce it with a premixed air-fuel mixture. It becomes a necessary condition.
Furthermore, on the low load side, it is important to form a fuel concentration field that matches the combustion load characteristics. For example, since the amount of NOx and CO produced is small in the low load region, a large shade is formed, and the load band becomes relatively large during the operation of the second stage fuel,
Since the fuel flow rate increases, the fuel in the first stage is reduced stepwise, and the amount of the reduction is adjusted so that the fuel in the second stage is introduced at the same time and the concentration is formed in the fuel concentration field. Let Especially when switching from the first stage to the second stage,
A fuel concentration field is formed on the inner peripheral side and the outer peripheral side of the second-stage injection hole portion, and is formed on the outer peripheral side thereof, to locally approach the theoretical mixing direction (excess air ratio λ = 1) to improve the fire transfer. After that, as the load band rises, the outer circumference side is made uniform, and near the rated time,
The combustion is continued in a mixed state in the complete premixing direction, which is most advantageous for low NOx combustion.

In the present invention, the above-described means is matched with the combustion load zone, the fuel concentration field is suppressed, and low NOx combustion is enabled.

〔Example〕

FIG. 1 shows a specific embodiment of the present invention. A main combustion chamber 5 having a sub-combustion chamber 3 having a first-stage premixed fuel injection port 2 at the head of an inner cylinder 1 of the combustor and a second-stage premixed fuel injection port 4 at the rear upstream side. In the gas turbine combustor composed of, the air flow passages 6, 7 and 8 that are annularly divided inward and outward are provided on the upstream side of the first-stage fuel injection port portion 2, and at the upstream ends of the respective flow passages. Fuel introduction pipes 9, 10 and 11 having jet holes
Are arranged in a circle, and fuel distribution pipes 12, 13 and 14 are installed so that the fuel can be dividedly introduced into the flow paths of the respective parts.
Each fuel flow rate control valve 15, 16, 17 Control device 18
To premix the air and fuel. on the other hand,
Also in the second-stage premixed fuel injection port portion 4 installed in the upstream portion of the main fuel chamber 5, the air flow passage portions 19, 20, 2 are similar to the above.
1, fuel introduction pipes 22, 23, 24, fuel distribution pipes 25, 2
6, 27 and control valves 28, 29, 30 to form a premixed gas.

During operation of this combustor, combustion air is caused to flow into each combustion chamber, and each fuel introduction mechanism is operated in accordance with a combustion load zone described later. For example, in the case where the premixed fuel injection port portion 2 is formed with a shade in the combustible mixture, the control valves 18, 16 and 17 are set via the control device 18 with respect to the air flow flowing through the air flow passage portions 6, 7, and 8. And operate the fuel distribution pipes 12, 13, 14
The fuel flow rate is suppressed to 12>13> 14. Also,
When making the fuel concentration uniform, the fuel distribution pipe 12 = 13 =
By distributing and supplying the fuel in the ratio of 14, the fuel concentration in the outlet cross section of the premixed fuel injection port 2 can be made uniform.
By operating in the same procedure when the second-stage premixed fuel injection port 4 is operated, an arbitrary fuel concentration field can be freely formed.

FIG. 2 shows an example of the fuel control operation method in the gas turbine operating region. The fuel operating range of the first stage is 25% of the turbine load from the time of ignition, up to 50% of the total fuel amount, and the fuel of the second stage is 25-100% of the turbine load.
Introduce a flow rate of 25-50% of the total fuel. In particular, at a turbine load of 25%, at the same time that the second stage fuel 25% is introduced stepwise, the first stage fuel is reduced from 50% to 25% stepwise, and then the first stage and second stage The stage fuel is divided into ½ of the flow rate commensurate with the turbine load zone and operated at the ratio of 50:50 of the total fuel at the rated time.

FIG. 3 is a specific example of the combustion region and the premixing single combustion range mainly for controlling the fuel concentration field of the present invention, and FIG. 4 shows an example of the formation state of the fuel concentration distribution in the cross section of the outlet of the fuel injection port. It was When introducing the fuel region and the fuel in a step-like manner mainly for controlling the fuel concentration field, form the fuel concentration field in the direction (a) of FIG. Further, the fuel concentration field should be controlled so as to move from (a) to (c) as the turbine load increases. Further, in the premixed combustion region, the combustion is continued by the fuel concentration field of (c).

FIG. 5 shows a specific example of the automatic control method of the fuel concentration field. In the fuel concentration field control mechanism, an exhaust gas sampling probe 31 is installed near the combustor outlet, and a gas analyzer 32 is installed.
Thus, the exhaust gas characteristics such as NOx and CO are detected, and the signal thereof is sent to the control device 18 so that the premixed state into the combustion chamber can be automatically operated. For example, when the NOx value is larger than the allowable value, the premixed combustion is strengthened, and when the CO generation is suppressed, the density is formed in the fuel concentration field to perform the combustion.

Therefore, combustion that reduces NOx and CO at the same time from low load to high load can be realized.

〔The invention's effect〕

FIG. 6 shows NOx and CO characteristic values according to the combustion method of the present invention. In the figure, NOx and CO limit values indicate regulated emission amounts, and CO suppression and low NOx are achieved while controlling the fuel concentration field by the turbine load. According to the basic experiment of the fuel concentration field, in the mixing pattern at the time of CO suppression, the fuel concentration at the fuel injection port has a concentration variation of 0.9 to the average mixture concentration value.
It was about 1.1, and it was confirmed that the fuel flow rate in that case should be increased by 10% in the higher concentration.
In this way, CO countermeasures in the direction of uniform mixing are easy,
The increase rate of NOx is also about 1.1 times. Further, since the amount of fuel is small on the low load side, CO suppression combustion is the main component rather than the NOx countermeasure, so the fuel is made to have a density so as to suppress the generation of CO within the limit value. Since these fuel concentration fields can be automatically controlled, highly reliable low NOx combustion can be realized.

[Brief description of drawings]

FIG. 1 is a system diagram of a combustor according to an embodiment of the present invention, FIG. 2 is a diagram showing an example of a fuel control operation method in a gas turbine operating region, and FIG. 3 is a fuel concentration field combustion and premix combustion range. One specific example diagram, FIG. 4 is a formation state diagram of the premixed fuel concentration distribution, FIG.
The figure shows a specific example of controlling the degree of premixing, and FIG. 6 shows the NOx, CO characteristic diagram of the present invention. 2 ... First stage premixed fuel injection port.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Fumio Kato 502 Jinritsucho, Tsuchiura-shi, Ibaraki Hiritsu Manufacturing Co., Ltd.Mechanical Research Institute (72) Yoshihiro Uchiyama 502 Jinritsu-cho, Tsuchiura-shi, Ibaraki Nitate Manufacturing Co., Ltd. Inside the mechanical laboratory

Claims (4)

[Claims] 1. When the air and the fuel are premixed and introduced into the combustion chamber, a density is formed in the fuel concentration field when the load is low, and the fuel concentration field is uniformly mixed when the load is high. A gas turbine combustor having means for controlling combustion according to a load zone to perform combustion. 2. The premixing mechanism according to claim 1, wherein the premixing mechanism is divided into several stages in an annular shape inward and outward on the upstream side of the fuel injection port portion to form an air flow passage portion, A large number of fuel introduction pipes are installed in the vicinity of the inflow port in a circumferential shape, and the control valve provided in the fuel distribution pipe to control the ratio of the fuel flow rate to the air flow of each stage is freely controlled by the signal of the control device. And forming a premixed fuel concentration field. 3. The gas turbine combustor according to claim 2, wherein the fuel introduction pipe is multi-staged in the axial direction of the combustion chamber. 4. The gas turbine combustor according to claim 2, further comprising a means for detecting an exhaust gas analysis value at a combustor outlet of the fuel introduction pipe, which is automatically operated by a signal from the exhaust gas analysis value.