JPS6213932A - Combustor for gas turbine - Google Patents

Abstract

PURPOSE:To carry out low NOx combustion by a method wherein an air introducing mechanism is provided near a first stage fuel nozzle provided on a head combustion chamber, multiple nozzles are provided and second stage fuel is premixed to introduce combustible mixture from an annular whirling device into the combustion chamber. CONSTITUTION:Air stream 27 and cooling air 28 are introduced through a gap between the first stage fuel nozzle 10 and a hole 9 provided on a liner cap 7. Upon low load, first stage fuel 29 is introduced into the main body 4 of fuel nozzle and is injected into a sub-chamber 8 from the fuel nozzle 10 having a multitude of injecting holes to carry out combustion. Upon high load, the fuel is introduced from a fuel path 31 and is injected through second fuel nozzle 19 provided at the upstream side of the annular whirling device 14, then, is mixed with the air stream 25 and combustible mixture is introduced into a main chamber 6 as a whirling stream to continue the combustion. Accordingly, the gas turbine combustor, being stable and reduced in the generation of NOx, may be provided by the combination of multiplication of injecting holes of the first fuel nozzle and the introduction of fuel from the second stage fuel nozzle, which is effected through the annular whirling device after premixing the fuel.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a gas turbine combustor, and in particular to a natural gas-fired low NOX combustor that aims to reduce nitrogen oxides (hereinafter referred to as NOX).
Regarding the combustor.

[Background of the invention]

NOx generation during combustion in a gas turbine combustor is dominated by the combustion gas in the local high-temperature part (1800°C or higher) of the combustion region, and is mainly caused by nitrogen components that are unburned emissions of fuel and nitrogen in the combustion air. Generated by oxidation of ingredients. especially,
During combustion during gas turbine operation, thermal NO is the main source due to its combustion form, so uniform low-temperature combustion (approximately 1500°C or less) does not form local high-temperature areas during the combustion process. A major objective is to achieve this.

Therefore, in order to ideally suppress the production of NOx by using only the combustion form K, it is an essential condition how to achieve catalytic mixing of fuel and air. As means for realizing this combustion method, there are premixing of air and fuel, dispersion of fuel, and multistage introduction method.

In particular, premix combustion allows for uniform and low temperatures;
It is considered to be the most advantageous for reducing NOx. However, the possible range of fully premixed combustion is narrower than that of diffusion combustion. There are problems such as flame backfire, and in actual gas turbine combustion, a combustion method using dispersed injection of fuel or multistage injection is adopted because of the wide operating range.

For example, Japanese Patent Publication No. 58-58563 discloses a two-stage combustion system in which a first-stage fuel nozzle with a single injection port is provided at the head of the combustor, and multiple second-stage fuel nozzles are installed on the downstream side. However, it has the following drawbacks: When the first-stage fuel nozzle is a single-nozzle type, there is a small amount of contact and mixing between the fuel jet in the center of the combustion chamber and the air flow from around the combustion chamber, resulting in a relatively large proportion of fuel introduced. , a localized high-temperature region that is disadvantageous for reducing NOx tends to be formed in the center of the combustion chamber. In addition, the second-stage fuel nozzle injection mechanism is also introduced in such a way that it is perpendicular to the combustion gas flow from the upstream side, and even if the fuel is a premixed combustible mixture, the fuel may interfere extremely with the flame inside the combustion chamber. The injection method cannot effectively reduce NOx.

[Purpose of the invention]

The purpose of the present invention is to provide multiple air introduction mechanisms and fuel nozzles near the first-stage fuel nozzle installed in the head combustion chamber, premix the second-stage fuel, and bring the combustible mixture from the annular swirler into the combustion chamber. This invention relates to the structure of a two-stage combustor that performs low NOx combustion.

[Summary of the invention]

When the gas turbine is under low load, the first stage fuel is introduced and diffused combustion is performed, and when the load is high, the two-stage combustion system performs premix combustion in the first and second stages, effectively achieving low NOx emissions. For this purpose, the operating range of the first and second stage fuels and their structure and configuration are important factors. In other words, the combustion chamber is a subchamber,
The combustion chamber is divided into main chambers, and each combustion chamber is provided with first and second stage fuel nozzles to disperse fuel in the cross-sectional direction of the combustion chamber. %K,
The fuel nozzle into the pre-chamber mainly uses diffusion combustion, so
Good contact with combustion air from the outer wall of the combustion chamber
, ', l', arranged near the outer wall of the combustion chamber where it is convenient. This promotes the mixing of fuel and air by dispersing the fuel and bringing it into close contact with the air flow, which is extremely effective. Since the main stream of air is formed near the first stage fuel nozzle, fuel can be effectively introduced into the air. For example, a mechanism for introducing fuel into the vortex for flame stabilization formed at the outer peripheral end of the head of the sub-chamber, or an air swirler for flame stabilization installed by multiple first-stage fuel nozzles, may also be used. It is also relatively easy to provide an air swirler in the center of the combustion chamber to prevent the formation of an extremely high temperature region in the center of the combustion chamber.

On the other hand, the second-stage fuel nozzle uses a premixing method that mixes air and fuel on the upstream side of the annular swirler, and causes the combustible mixture to flow into the main combustion chamber in a large swirling flow. This swirling flow not only ensures stable combustion when the second stage fuel is introduced, but also avoids extreme interference with combustion in the head pre-chamber, forming a parallel swirling jet flow that is less likely to generate localized high temperatures. Therefore, an effective combination of multiple first-stage fuel nozzles and fuel from the second-stage fuel nozzle that is premixed and then introduced via an annular swirler aims to achieve stability and low NOx. gas turbine 1" [1, g
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In a gas turbine combustor consisting of 4, 5, etc.
The head of the inner cylinder 2 has a smaller cross section than the main combustion chamber 6 provided at the rear, and there is a sub-combustion chamber 8 formed by a liner cap 7 at the upstream end. The first stage fuel nozzle 10 protrudes into the auxiliary chamber 8, or
A plurality of holes are arranged in a non-protruding state, and a large number of combustion air introduction hole groups 12t are provided on the outer wall 11 of the sub-chamber.

On the other hand, an annular swirler 1 is attached to the inner cylinder enlarged portion 13 of the sub chamber 8 and the main chamber 6.
4, a fuel introduction flange 16 is fixed between the end cover 3 and the 7 flange 15 of the outer cylinder 1, and a second stage fuel nozzle 19 is connected from the fuel introduction pipe 17 and the fuel chamber 18 to the annular swirler 14. In addition, the outer wall 2 of the main room 6
0, a cooling air hole 21 and a dilution air hole 22'Jk are installed.

During operation of this combustor, air 23 is introduced into the main chamber 6 through the dilution air hole 22, cooling air 24, and air flow 25 to the annular swirler 14, and into the auxiliary chamber 8 is a group of combustion air introduction holes. 12 air flow 26, first stage fuel nozzle 10 and liner cap 7
Air is introduced from the air flow 27 from the gap between the holes 9 provided in the hole 9 and the cooling air 28. When the load is low, the first stage fuel 29 is introduced into the fuel nozzle main body 4, and is introduced into the auxiliary chamber 8 through the fuel nozzle 10 having a large number of ejection holes 29, and is ignited with a spark plug to perform combustion. , the fuel is introduced from the fuel 31 and ejected from the second stage fuel nozzle 19 installed on the upstream side of the annular swirler 14, mixed with the air flow 25, and the combustible mixture is guided into the main chamber 6 as a swirl flow for combustion. continue.

FIG. 3 shows an example of fuel control during operation of the gas turbine. The operating range of the first stage fuel nozzle 10 is kept constant after load control from the time of ignition to the turbine load of 25 cm, and the second stage fuel nozzle is introduced from the turbine load of 25 cm and operates in the high load range up to the constant load. . The features of this combustor are that the first-stage fuel nozzles 10 installed in the auxiliary chamber 8 are multi-layered, and the mechanism for introducing the premixture from the annular swirler 14 installed in the enlarged part 13 of the main chamber 6 has a parallel annular shape. The purpose is to have a rotating shape.

Other embodiments are shown in FIGS. 4 and 5.

A structural diagram of the combustor, showing an outer cylinder 1, an inner cylinder 2, an end cover 3,
It is composed of a first stage fuel nozzle main body 4, etc., the head of the inner cylinder 2 is formed by an auxiliary chamber 8 and a main chamber 6 at the rear thereof, and air is supplied to the center of a liner camp 7 that forms the upstream end of the auxiliary chamber 8. A swirler 32 is installed, and a plurality of first stage fuel nozzles 34 each having an air swirler 33 are arranged in a ring shape so as to cover the air swirler 32. Further, an annular swirler 14 is provided at the outlet of the auxiliary chamber 8, and a large number of second stage fuel nozzles 19 are protruded from a portion of the fuel chamber 18 corresponding to the nozzle portion between the swirling vanes of the annular swirler 14. Install.

The feature of this combustor is that an air swirler 33 is provided in the first stage fuel nozzle 34, making it multi-purpose. An air swirler 32 is installed near the upstream center of the auxiliary chamber 8 to strengthen the flame stability of the first stage fuel nozzle and to cool the auxiliary chamber 8 with one air flow so that the vicinity of the center does not become a high temperature region. Furthermore, if the air introduced into the center of the sub-chamber 8 is made into a swirling flow, the velocity component in the axial direction will be relatively small, so stable combustion can be expected. In particular, by dispersing fuel into the pre-chamber, the fuel flow rate per fuel nozzle can be reduced, and by introducing it near the main stream of air in the combustion chamber, mixing and diffusion is promoted, and flame separation during combustion is on the lean side. This makes it relatively easy to make the gas temperature uniform in the cross-sectional direction of the combustion chamber. In addition, the structure of the first stage fuel nozzle is equipped with an air swirler, so that even when the fuel injection part protrudes, there is a large proportion of contact with air from around the combustion chamber, and mixed combustion on the lean side is expected. This is very advantageous for reducing NOx. Furthermore, as another method, installing an air swirler in the center of the combustion chamber with a structure in which the first stage fuel nozzle protrudes can also lower the combustion temperature near the center of the combustion base and effectively work toward lean combustion. . In particular, when introducing fuel to the outer circumferential side of the combustion chamber,
Flames may be generated around the combustion chamber, drawing high-temperature gas into the center, so installing an air swirler near the center of the combustion chamber is an effective means of avoiding localized high-temperature areas. Therefore, the gas turbine combustor of the present invention has a highly reliable low NO
It can be provided as an x-oxidized combustor.

Figure 6 shows 1 conventional method (Citation: Special Publication No. 58-58563)
2 shows the gas temperature distribution near the outlet of the head combustion chamber in the two-stage combustor of the present invention and the two-stage combustor of the present invention. Since the conventional system has a single-hole fuel nozzle in the center of the combustion chamber, a high-temperature region is formed in which high-temperature gas during combustion is concentrated in the center, and the outer circumferential side of the combustion chamber tends to be lower.

On the other hand, in the combustor of the present invention, the gas temperature is lower overall than in the conventional type, and the temperature distribution in the cross-sectional direction of the combustion chamber is low near the center and a relatively high temperature region is formed on the outer circumference. Uniformity in the direction can be achieved. That is, more uniform and lower temperature combustion than the conventional method is possible, and effective reduction in NOx can be achieved.

-! In addition, since a high temperature region is formed on the outer circumferential side of the combustion chamber,
It is possible to improve the fire transfer characteristics to the second stage fuel nozzle.

In particular, the fire transfer phenomenon is significantly influenced by the temperature of the atmosphere near the introduction of the combustible mixture. In other words, the flammable range of fuel is highly dependent on temperature and tends to widen as the temperature increases, so a temperature distribution with a high gradient toward the outer circumferential side of the gas temperature from the upstream side is effective for preventing fire from spreading. . Furthermore, the annular swirler constituting the second stage fuel nozzle section is made parallel, so that the combustible mixture is jetted in a parallel swirl with respect to the gas flow from the upstream side, thereby preventing extreme flame interference. .

FIG. 7 shows an example of the NOx suppression results of the combustor structure of the present invention. Compared to the conventional system, it is possible to improve the NOx reduction rate by 30 degrees during rated gas turbine operation.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of the combustor of the present invention, and Figure 2 is the
3 is an explanatory diagram of the fuel introduction method in combustion according to the present invention, FIG. 4 is a vertical cross-sectional view of the combustor head of another embodiment of the present invention, and FIG. Figure 6 is a gas temperature distribution diagram in a cross-sectional view near the pre-chamber outlet of the combustor head, Figure 7 is a view in the direction of the V arrow.
The figure is a comparison diagram of NOx characteristics of the conventional and the present invention. 6...Main chamber, 7...Liner cap, 8...Sub-chamber, 10...First stage fuel nozzle, 14...Annular swirler, 1-Bin depression "Qo scam 40"

Claims (1)

[Scope of Claims] 1. A sub-combustion chamber is formed at the head of the combustor inner cylinder, and a main combustion chamber having a cross section enlarged from the sub-combustion chamber is formed at the rear of the sub-combustion chamber, forming a front end of the sub-combustion chamber. A plurality of first-stage fuel nozzles are arranged and installed in the liner cap part, and an annular swirler is provided in the enlarged part of the auxiliary combustion chamber and the main combustion chamber, and a corresponding upstream fuel nozzle is provided between the swirler blades. It has a mechanism in which a large number of second-stage fuel nozzles are arranged in the side space, and air and fuel are mixed and then introduced into the main combustion chamber in a swirling flow.
A gas turbine combustor characterized in that the first stage fuel nozzle is operated, and in a high load region, fuel is also introduced into the second fuel nozzle for combustion. 2. A gas turbine combustor according to claim 1, comprising a tubular first stage fuel nozzle that protrudes through a front end liner cap portion of the auxiliary combustion chamber. 3. According to claim 1, an air swirler is installed in the center of the liner cap of the auxiliary combustion chamber, and a plurality of the first stage fuel nozzles are arranged on the outer circumferential side of the air swirler. Gas turbine combustor. 4. The gas turbine combustor according to claim 1, characterized in that an air swirler is installed in the first stage fuel nozzle.