JP2544515B2 - Gas combustor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a gas combustor, and more particularly to a premixed combustion type gas combustor in which fuel and air are premixed and burned.

[Conventional technology]

Nitrogen oxides (NOx) generated during the combustion of gas fuel with low nitrogen content such as liquefied natural gas (LNG) are mostly thermal NOx produced by the oxidation of nitrogen in combustion air in a high temperature atmosphere. Occupy It is known that the production of thermal NOx has a large temperature dependency, and the production amount increases as the flame temperature rises, especially when the temperature exceeds 1500 ° C, the production amount rapidly increases. The flame temperature changes depending on the mixing ratio of the fuel and air, and becomes the highest when the fuel is burned in the vicinity of the stoichiometric amount of air, that is, the stoichiometric amount of air for complete combustion of the fuel. To suppress the NOx generation amount, it is necessary to lower the flame temperature. To lower the flame temperature, blow water or steam into the fuel chamber to forcibly lower the temperature, or make the mixing ratio of fuel and air extremely higher or lower than the theoretical air amount. The method of burning with is proposed.

The method of injecting water or steam has a new problem of lowering turbine efficiency.

In a normal combustion device, a so-called diffusion flame is used as a flame stability and a flashback prevention measure, in which fuel and air are ejected from separate nozzles, and both are mixed and burned in a combustor. However, in the process of mixing fuel and air, the air ratio (the ratio of the air flow rate to the theoretical air quantity) is 1
There is a nearby area where the flame temperature locally rises. Therefore, a region where the amount of NOx generated is large is formed, and the amount of NOx emitted increases.

In addition to such a combustion device that uses a diffusion flame, there is a combustion device that uses a premixed flame that premixes air and fuel in excess of the theoretical air amount and ejects them into the combustor. In a premixed flame with a high air ratio, it is possible to prevent the formation of a region where the temperature locally rises, so it is possible to reduce NOx emissions, but a premixed flame is the most stable when the air ratio is around 1. In addition, when the ejection speed is increased, it is easy to blow out, and at low ejection speed, the flame easily enters the nozzle and backfires easily. In a gas combustor, fuel and air are usually ejected at a high ejection speed of about 50 m / s. However, it is difficult to form a flame under such a high ejection velocity condition. Therefore,
Fuel is divided and supplied, part of it is used for diffusion flame formation, and the rest is used for premixed flame formation.A relatively stable diffusion flame or high-temperature combustion gas generated by the diffusion flame is used for premixed flame formation. There is a combustor used for ignition (JP-A-61-
No. 22127) In such a combustor, NOx emission amount can be reduced as compared with a combustor using a conventional diffusion flame.
However, if the flow rate of the fuel used for the diffusion flame is reduced and the fuel flow rate of the premixed flame is increased, NOx can be reduced, but if the proportion of premixing increases, the flame becomes unstable and NOx emission or In Japanese Patent Publication No. Sho 57-192728, the inner surface 4
The outer cylinder 16 is formed, the flow is branched from the extraction passage 7, the pressure is increased by the compressor 18 and is guided to the fuel nozzle 3, and the predetermined flow rate is determined only by the primary swirler area. Is mixed with air in the fuel nozzle 3 and flows into the pre-combustion chamber 1 as premixed air, and the secondary air is provided with an air flow passage between the inner surface 4 and the outer cylinder 16 so as to control the passage area variable. The flow rate is controlled according to the load by the device 14, and the secondary fuel from the secondary fuel pipe 9 and the secondary swirler
A gas turbine premix combustion apparatus is disclosed in which a fuel-lean mixture is introduced into the main combustion chamber 2 while being premixed in the vicinity of 11 or diffusively mixed at the outlet of the swirler 11.

Further, in Japanese Patent Publication No. 58-57656, a fuel burner is provided with a first swirl flow means on the upstream side and a hollow duct through which an air flow flows, and a second duct on the upstream side which at least partially surrounds the hollow duct. An annular outer duct having a swirl flow means for allowing an air flow therethrough, a first fuel injection means for injecting an appropriate amount of fuel into a hollow duct downstream of the first swirl flow means, and a second
A combustion device for a gas turbine engine is disclosed, which comprises a second injection means for injecting an appropriate amount of fuel into the outer duct downstream of the swirling flow means.

[Problems to be Solved by the Invention]

In the above-mentioned conventional technique, a diffusion flame is partially formed in order to stabilize an unstable premixed flame, so that there is a limit in reducing NOx generated from the gas combustor.

Therefore, if the unstable premixed flame is stabilized and the gas combustion system is the complete premixed combustion, the NOx generated from the gas combustor can be reduced.

The problem when the gas combustion system is completely premixed combustion,
In order to flow a large amount of combustion air as compared to the fuel flow rate during low load operation, the fuel becomes lean and does not ignite, and in order to increase the supplied fuel and air flow rate during high load operation, There is a problem that the flow velocity of the premixed air becomes higher and the premixed flame is easily blown out.

Further, JP-A-57-192728 discloses only supplying a lean air-fuel mixture from the outlet of the secondary swirler, and JP-B-58-27656 discloses that when the engine output is low, the fuel consumption is low. It is disclosed that most or all of the above is sent to the auxiliary nozzle referred to in the present invention, and more than half of the fuel is distributed to the main nozzle when the engine output increases,
No consideration was given to stabilizing the main flame that burns at a high air ratio at high speed with the auxiliary flame to reduce environmental pollutants.

An object of the present invention is to provide a gas combustor that stably burns a lean premixed gas having an air ratio of 1.5 or more.
Further, it is to provide a gas combustor capable of stably burning a lean premixed gas from a low load to a high load of the gas turbine.

[Means for solving the problem]

In order to achieve the above object, the gas combustor of the present invention,
In a gas combustor having a main nozzle and an auxiliary nozzle arranged so as to be adjacent to the main nozzle, a main mixture of a lean fuel having an air ratio of 1.5 or more containing air in excess of the theoretical air amount in the main nozzle. And a means for supplying the auxiliary nozzle is arranged on the outer peripheral portion of the main nozzle, and the injection speed of the premixed gas to the auxiliary nozzle is 1.0 to 2.0 m / s, the air ratio is 0.8 to 1.5. A means for supplying an auxiliary premixed gas in a range is provided, and a plurality of main nozzles are provided, and the main nozzle is ignited by the auxiliary nozzle.

[Action]

In the present invention, an auxiliary flame having a low ejection speed is used as an auxiliary flame for igniting and holding a premixed flame (main flame) having a high ejection speed. Therefore, the jet speed of the premixed gas to form the pilot flame for flame holding is set to 2 m / s or less to suppress the generation of NOx and improve the flame holding performance of the auxiliary flame for blowing. Prevent disappearance. Further, by enclosing the entire outer periphery of the premixed gas ejected at a high ejection speed with an auxiliary flame for flame holding, the heat generated by the flame for flame holding can be efficiently generated,
Can tell the main flame. Furthermore, between the main flame burner and the auxiliary flame burner, and between the burners ejecting the main flame good mixture and the auxiliary flame mixture, the vortex flow formed by the difference in the jet speeds of both is stable. A spacer that can be formed on the main flame is provided.
It promotes mixing with the combustion gases from the hot auxiliary flame, which can enhance the ignitability of the main flame. Further, for example, when the main flame and the auxiliary flame are separated by a thin partition wall such as a knife edge without providing a spacer, the flow of the auxiliary flame is greatly affected by the jet flow of the main flame,
It is clear from the experiments by the inventors that the auxiliary flame also extinguishes under the condition that the main flame is blown out. Therefore, by providing the spacer, the main flame and the auxiliary flame do not mix directly in the vicinity of the burner outlet, but a part of both mix in the vortex flow formed by the spacer section, and the auxiliary flame is the main flame. Since it can be stably formed without being affected by, the range of the flow velocity or the air ratio at which the flame is stably formed is increased.

Further, a plurality of the main nozzles are provided, and the main nozzle is ignited by the auxiliary nozzle, so that reliable ignition can be performed and stable combustion is achieved even after the ignition. Further, it is possible to perform combustion according to the load.

〔Example〕

FIG. 1 is a sectional view of a gas turbine combustor embodying the present invention. Inside the cylindrical outer cylinder 10, the inner cylinder 20 is concentrically arranged, and the annular space formed between the outer cylinder 10 and the inner cylinder 20 allows the discharge air from the compressor (not shown) to flow from the inner cylinder. An air passage 12 is densely formed on the head. Double end walls 11 and 12 are provided on the head of the inner cylinder 20, and as shown in FIG. 2, the inner end wall 11 is assisted so that the main nozzle 14 and its surroundings are almost entirely covered. The nozzle 15 is open. Main nozzle 14
Is formed at the right end of a cylindrical premixing cylinder 16 extending through the end wall 12 toward the outer end wall 12 side, and the pressure end of the premixing cylinder 16 is the end wall.
Air is taken in from an air chamber 17 formed on the left side of 12. A fuel supply pipe 18 is inserted into each premixing cylinder 16 and
The fuel ejected from the end of 18 mixes with the air when flowing in the cylinder 16 to generate a premixed gas. The auxiliary nozzle 15 is an end wall
It communicates with an auxiliary premixing chamber 30 formed between 11 and 12, and this chamber 18 is supplied with auxiliary fuel via an auxiliary fuel adjusting valve 40 and is opened on the peripheral wall surface of the inner cylinder. It mixes with the air from the air holes 26 to produce a premixed air. Fuel supply pipe 18
Are communicated with the main fuel regulating valve 60 via a stop valve 50 provided in each pipe. The valves 50 and 60 are controlled by a command from the controller 70. The load and rotation speed signal of the gas turbine are taken into the controller 70.

The stop valve 50 is fully opened when an open signal is given from the controller 70, and is kept fully closed otherwise. In FIG. 1, only four stop valves are shown, but all fuel supply pipes 18 are provided, and in this embodiment there are 19 stop valves, as shown in FIG. As the load increases,
The number of open stop valves increases. On the other hand, the opening degree of the adjusting valve 60 is
It increases almost proportionally to the turbine load. Regulating valve 40 maintains a substantially constant opening (about 10%) regardless of the turbine load. Then, the auxiliary premixing chamber 30 is always supplied with an almost constant amount of fuel via the adjusting valve 40 and premixed with the air from the air hole 26, but the mixing ratio with the air from the air hole 26 is large. Is set so that the air ratio is in the range of 0.8 to 1.5, and the ejection speed from the auxiliary nozzle 15 is in the range of 1.0 to 2.0 m / s, which is higher than the combustion speed (0.5 m / s). Then, the opening area of the nozzle 15 is adjusted.

When operating the gas turbine, first, the auxiliary regulating valve 40
Is opened, and the auxiliary premixed gas is generated in the auxiliary premixing chamber 30. Next, the premixed gas ejected from the auxiliary nozzle 15 is ignited by an ignition plug (not shown). The air ratio of the auxiliary premixed air is set to around 1, preferably 1.3, and the ejection speed is also set.
Ignition is certain because it is less than 2.0 m / s, and combustion is stable even after ignition.

At this time, most of the stop valve 50 is closed, so only the air is ejected from the main nozzle 14. The opening signal of the adjusting valve 60 gradually increases due to the turbine load signal, and the stop valve 50
Also, the valves are opened in a predetermined order. Then, the premixed gas is generated in the premixing cylinder 16, and the premixed gas is ejected from the main nozzle 14 at high speed. The premixed gas ejected from the main nozzle 14 is ignited by the auxiliary flame 80 (FIG. 3) formed around the premixed gas,
The main flame becomes 90.

As the stop valve 50 is sequentially opened, the number of flames formed in the main nozzles 14 is also sequentially increased, and at the rated load, flames are formed in all the main nozzles 14. Generally, in a gas turbine for power generation, the rotation speed of the turbine is constant from 0% to 100% of the load, so that the air supplied to the combustor is almost constant. Therefore, the amount of air flowing into the premixing cylinder 16 from the air chamber 17 is substantially constant.

On the other hand, the amount of fuel passing through the adjusting valve 60 changes substantially in proportion to the turbine load, but the number of open stop valves 50 changes according to the amount of fuel, so that there is a premix cylinder for each open stop valve. The amount of fuel supplied is almost constant, and the air ratio of the air-fuel mixture produced in the premixing cylinder 16 does not change significantly. Therefore, in this embodiment, the air ratio is set to 1.5 or more, preferably about 2.0.

In this embodiment, the premixed gas of the auxiliary nozzle 15 has an air ratio of 1
Since it is set in the vicinity with a good flame holding property, even if the premixed gas is ejected from the main nozzle 14 at high speed, there is no fear of blowout.

Further, even if the premixing ratio from the main nozzle 14 is a lean one having an air ratio of 1.5 or more, stable combustion is achieved by the auxiliary flame.

Fig. 5 shows the relationship between the amount of NOx produced and the amount of H ₂ and CO produced when the air-fuel ratio of the premixed gas is changed and burned. The main flame has an air ratio of 1.5 or more. Therefore, the amount of NOx generated is significantly reduced as shown in 181, and CO and H ₂ are 19
As seen in 1,201, it becomes almost zero. Obviously, O ₂ exhibits a characteristic like 211.

From this characteristic, the air ratio of the premixed gas in the auxiliary nozzle is close to 1, so the amount of NOx generated is large, but the fuel ratio of the auxiliary flame is about 10% at the rated load, so the overall NOx Is reduced.

Fig. 6 shows sampling at 5 mm downstream from the main nozzle in the radial direction from the center of the nozzle, moving the probe, collecting and analyzing the fuel gas, and examining the combustion state inside the main flame and near the auxiliary flame. It is a thing. As you can see from the figure, almost no CH ₄ is burned inside the main flame,
CH ₄ burns as it approaches the auxiliary flame, and 100% of the CH ₄ burns above the auxiliary flame nozzle. That is, it can be seen that the flame transfer from the auxiliary flame of the auxiliary nozzle to the premixed air of the main nozzle is reliably performed.

〔The invention's effect〕

According to the present invention, the injection speed of the premixed gas is reduced to the auxiliary nozzle.
A means for supplying an auxiliary pre-mixture in the range of 1.0 to 2.0 m / s and an air ratio of 0.8 to 1.5 is provided, and since the main nozzle is ignited by the auxiliary nozzle, steady ignition of the main flame at high speed can be achieved. Therefore, by constantly forming a stable auxiliary flame at the root of the combustion flame of the high air ratio main nozzle, the main flame that burns at high speed can be retained. As a result, the gas turbine combustion system can be a complete premixed combustion type, so if the air ratio of the fuel-air mixture gas for the main flame is set from 1.5 to the high air ratio side and lean combustion is performed, the gas turbine combustor It is possible to reduce NOx and CO, which are environmental pollutants emitted from the environment. Further, since a plurality of main nozzles are provided, it is possible to operate according to the load.

[Brief description of drawings]

FIG. 1 is a sectional view of a gas turbine combustor embodying the present invention, FIG. 2 is a sectional view taken along line II-II of FIG. 1, FIG. 3 is a detailed sectional view of a nozzle portion, and FIG. Turbine load and opening characteristics of each valve, Fig. 5 shows the air ratio of premixed gas and NOx, CO, H
FIG. 6 is a characteristic diagram showing the relationship of ₂ , and FIG. 6 is a characteristic diagram showing the results of combustion gas analysis in the flame radial direction. 10 …… Outer cylinder, 11,12 …… End wall, 14 …… Main nozzle, 15 ……
Auxiliary nozzle, 16 ... premixing cylinder, 18 ... fuel supply pipe, 20 ...
… Inner cylinder, 30 …… Auxiliary premixing chamber, 40 …… Auxiliary control valve, 50…
… Stop valve, 60… Main regulator valve.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kiyoshi Narato 4026 Kuji Town, Hitachi City, Hitachi, Ibaraki Prefecture Hitachi Research Laboratory, Ltd. (72) Keinobu Kobayashi 4026 Kuji Town, Hitachi City, Ibaraki Hitachi Ltd. In-house (72) Inventor Toru Inada 4026 Kuji-machi, Hitachi, Hitachi, Ibaraki 4026 Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Tadataka Murakami 4026, Kuji-cho, Hitachi, Ibaraki Hitachi, Ltd. (72) Invention Noriyoshi Arashi 4026 Kujimachi, Hitachi, Hitachi, Ibaraki Prefecture, Hitachi Research Laboratory, Hitachi Ltd. (72) Inventor, Yoji Ishibashi 502, Kamimachi, Tsuchiura City, Ibaraki Prefecture Machinery Research Laboratory, Hitachi Ltd. (72) Inventor, Tomio Kuroda Hitachi, Ibaraki Prefecture 3-1-1, Saiwaicho, Ichi, Hitachi, Ltd., Hitachi Works (56) References Akira 57-192728 (JP, A) JitsuHiraku Akira 62-24274 (JP, U) Tokuoyake Akira 58-57656 (JP, B2)

Claims (1)

(57) [Claims] 1. A gas combustor having a main nozzle and an auxiliary nozzle arranged so as to be adjacent to the main nozzle,
A means for supplying a main air-fuel mixture having an air ratio of 1.5 or more with excess air to the main nozzle to the main nozzle, and the auxiliary nozzle being arranged on an outer peripheral portion of the main nozzle, Moreover, the injection speed of the premixed gas is 1.0 at the auxiliary nozzle.
~ 2.0m / s, the air ratio is provided with a means for supplying an auxiliary pre-mixture in the range of 0.8-1.5, the main nozzle is provided in a plurality, the auxiliary nozzle for ignition of the main nozzle A gas combustor characterized by being performed by.