WO1989002052A1

WO1989002052A1 - Gas turbine combustor

Info

Publication number: WO1989002052A1
Application number: PCT/JP1988/000870
Authority: WO
Inventors: Yasuo Iwai; Shigeru Azuhata; Kenichi Sohma; Kiyoshi Narato; Hironobu Kobayashi; Tooru Inada; Tadayoshi Murakami; Norio Arashi; Yoji Ishibashi; Michio Kuroda
Original assignee: Hitachi, Ltd.
Priority date: 1987-09-04
Filing date: 1988-08-31
Publication date: 1989-03-09
Also published as: DE3854666D1; EP0335978A1; JPS6463721A; DE3854666T2; JP2528894B2; CN1032230A; CN1011064B; EP0335978A4; EP0335978B1

Abstract

This invention relates to a gas turbine combustor of a premixing combustion system in which a fuel and the air are mixed and burnt, consisting of a cylindrical main nozzle provided on an upstream end wall of a cylindrical combustion chamber, an auxiliary nozzle formed around the main nozzle, a main premixed gas supply means for supplying a premixed gas to the main nozzle, and an auxiliary premixed gas supply means for supplying a premixed gas, the excess air ratio of which is smaller than that of the main premixed gas, to the auxiliary nozzle. Owing to this arrangement, a lean premixed gas having an excess air ratio larger than 1 can be burnt stably under low to high loads of a gas turbine.

Description

Specification

Gas turbine combustor

Technical field

The present invention relates to a gas turbine combustor, and more particularly to a premixed combustion type gas turbine combustor in which fuel and air are mixed in advance and burned.

Background art

Gases with a low nitrogen content, such as liquefied natural gas (LNG) Nitrogen oxides (N0X) generated during the combustion of fuel are generated by oxidizing nitrogen in the combustion air in a high-temperature atmosphere and producing NO. x makes up the majority. The production of thermal N〇 x has a large temperature dependence, and the production increases as the flame temperature increases, and especially when the temperature exceeds 150 ° C, the production may increase rapidly. Are known. The flame temperature changes depending on the mixture ratio of fuel and air, and becomes the highest when the fuel is burned near the stoichiometric amount of air where there is no excess or shortage to completely burn the fuel. In order to suppress the amount of NOx generated, it is necessary to lower the flame temperature. In order to lower the flame temperature, water or steam is blown into the fuel chamber to forcibly lower the temperature, or the mixing ratio of fuel and air is set to be extremely larger than the theoretical air amount, or the opposite. A method has been proposed in which combustion is performed in a reduced amount.

Injecting water or steam depends on the efficiency of the turbine. A new problem of degradation arises.

In a normal combustion device, as a measure for flame stability and flashback prevention, separate nozzles are used to separate fuel and air from the fuel, and the rain is mixed in the combustor and burned. A so-called diffusion flame is used. However, in the process of mixing fuel and air, there is a region where the air ratio (the ratio between the air flow rate and the theoretical air amount) is close to 1, where the flame temperature locally rises. Therefore, a region with a large amount of N 0 X is formed, and the amount of N 0 X discharged is increased.

In contrast to such a combustion device using a diffusion flame, there is a combustion device that uses a premixed flame in which an excess amount of air and fuel is mixed in advance with a theoretical amount of air and then injected into a combustor. Premixed flames with a high air-to-air ratio can prevent the formation of locally high-temperature regions, which can reduce NOx emissions.However, premixed flames have an air-to-air ratio of 1 It is most stable in the vicinity, and tends to blow out when the ejection speed is high, and at low ejection speed, the flame easily enters the nozzle and flashes back. In gas turbine sintering devices, it is necessary to eject a premixed mixture of fuel and air at a high ejection speed, usually about 40 mZs to 7 OmZs. Flames are difficult to form under high conditions. Therefore, the fuel is divided and supplied, and a part is used for forming a diffusion flame, and the rest is used for forming a premixed flame, and a relatively stable diffusion flame or diffusion is used. There is a combustor that uses the high-temperature combustion gas generated by the flame to ignite a premixed flame (Japanese Patent Laid-Open No. 22127/1986). Such a combustor is more effective than a conventional combustor using a diffusion flame. The emission of N 0 X can be reduced. However, reducing the flow rate of the fuel used for the diffusion flame and increasing the fuel flow rate of the premixed flame can reduce NOx, but increasing the premixed rate makes the flame unstable, so NOX emissions There is a limit to reducing the volume.

If unstable premixed flames are stabilized and the gas turbine combustion method is changed to complete premixed combustion, it is possible to reduce NOx generated from gas turbine combustors.

A problem when the gas turbine combustion system is completely premixed combustion is that a large amount of combustion air flows compared to the fuel flow rate during low-load operation, so the fuel becomes lean and ignites. In addition, during high-load operation, the flow rate of the premixed gas further increased in order to increase the supply material and the air flow rate, and there was a problem that the premixed flame was likely to blow and disappear. Disclosure of the invention

An object of the present invention is to provide a gas turbine combustor and a combustion method capable of stably burning a lean premixed air having an air ratio greater than 1 from a low load to a high load on a gas turbine. It is in.

This purpose is provided on the upstream end wall of the cylindrical combustion chamber. A cylindrical main nozzle, an auxiliary nozzle formed on an outer peripheral portion of the main nozzle, a main premix air supply means for supplying a premix air to the main nozzle, and the main premix to the auxiliary nozzle This is achieved by a gas Durbin combustor characterized by comprising auxiliary premixed gas supply means for supplying a premixed gas having an air ratio smaller than that of air. Furthermore, a premixed combustion method for a gas turbine combustor, characterized in that premixed gas ejected from an opening of a cylindrical main nozzle is burned by a premixed flame formed on an outer periphery of the opening of the raw nozzle. Is also achieved.

ADVANTAGE OF THE INVENTION According to this invention, the main flame which burns at high speed can be maintained by forming a stable auxiliary flame constantly at the base of the high air ratio combustion flame. As a result, the gas turbine combustion system can be completely premixed combustion, and if the air ratio of the fuel-air mixture gas for the main flame is set from 1.0 to the high air ratio side to perform lean combustion, the gas turbine It has the effect of reducing the environmental pollutants NOx and CO generated from the combustor.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a partial cross-sectional view of a gas turbine combustor embodying the present invention, FIG. 2 is a cross-sectional view taken along the line Π—Π in FIG. 1, and FIG. 3 is a detailed cross-sectional view of a nozzle portion in FIG. Fig. 4 is a graph showing the relationship between the turbine load and the opening of each valve shown in Fig. 1, and Figs. 5 (a) and (b) show changes in the air ratio of the premixed gas. Ete graph showing the relationship between the generated amount of the burned Kino NO x generation amount and the H _2, CO, FIG. 6 (a) and (b) the air ratio obtained by using the combustor of the present invention 3.6 7 is a graph showing the composition of the exhaust gas in the radial direction of the flame nozzle, and FIG. 8 is a graph showing another embodiment of the gas turbine combustor of the present invention. Fig. 9 is a simplified cross-sectional view along the line E-K in Fig. 8, and Fig. 10 is a characteristic diagram showing the relationship between load fluctuation and fuel supply system in the gas turbine combustor in Fig. 8. It is.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a cross-sectional view of a gas turbine combustor embodying the present invention. An inner cylinder 20 is arranged concentrically inside the cylindrical outer cylinder 10, and a rectangular space formed between the outer cylinder 10 and the inner cylinder 20 is discharged from a compressor (not shown). An air passage 12 is formed to guide air to the head of the inner cylinder. At the head of the inner cylinder 20, double end walls 11 and 12 are provided. On the inner end wall 11 as shown in FIG. Auxiliary nozzles 15 and are open so that they surround the surroundings. The main nozzle 14 is formed at the right end of a cylindrical premix cylinder 16 extending through the end wall 12 to the outer end wall 12 side, and the left end of the premix cylinder 16 is formed at the end wall 1 Air is taken in from the air chamber 17 formed on the left side of 2. A fuel supply pipe 18 is inserted into each premixing cylinder 16, and an end of the fuel supply pipe 18 is provided. When fuel flows out of the cylinder 16, it mixes with air to generate a premixed gas. The auxiliary nozzle 15 communicates with an auxiliary premixing chamber 30 formed between the end walls 11 and 12, and the chamber 30 is provided with a uniform premixing chamber from a bench lily mixer 31. An air-fuel mixture is supplied. 3 By introducing high-pressure air into the mixer 1 through the air inlet valve 40 through the inlet plate 26, the fuel adjusted to atmospheric pressure is sucked into Generates a premixed gas. The fuel supply pipes 18 are communicated with the main fuel regulating valve 60 via stop valves 50 provided on the respective pipes. The valves 50 and 60 are controlled by a command from the controller 70. The controller 70 receives the gas turbine load and rotation speed signals.

The stop valve 50 is fully opened when an open signal is given from the controller 70, and is kept fully closed otherwise. Although only four stop valves are shown in FIG. 1, they are provided in all fuel supply pipes 19, and in this embodiment there are 19 stop valves, and FIG. As shown, as the load on the turbine increases, the number of open stop valves increases. On the other hand, the opening of the regulating valve 60 increases almost in proportion to the turbine load. The regulating valve 40 maintains an almost constant opening (about 10%) regardless of the turbine load. Thus, the premixed gas introduced into the auxiliary premixing chamber 30 becomes a uniform premixed gas in the mixer 31 and has an air ratio in the range of 0.8 to 1.2. The air adjusting valve 40 is adjusted so that the air blowing rate is set to a certain value and the ejection speed from the auxiliary nozzle 15 is almost the same as the combustion speed.

When operating the gas turbine, first, the auxiliary flame air regulating valve 40 is opened, and the auxiliary premixed gas is generated by the mixer 31. Next, a premixed gas ejected from the auxiliary nozzle 15 is ignited by an ignition plug (not shown). The air ratio of the auxiliary premixed gas is set to around 1, that is, 0.8 to 1.2, and the injection speed is 0.4 m, which is almost the same as the combustion speed, so ignition is reliable and stable after ignition Burn.

At this time, since most of the stop valves 50 are closed, only air is ejected from the main nozzle 14. The opening of the regulating valve 60 gradually increases according to the load signal of the turbine, and the stop valve 50 also opens in a predetermined order. Then, a premixed gas is generated in the premixed cylinder 16, and the premixed gas is ejected at a high speed from the main nozzle 14. The premixture jetted from the main nozzle 14 is ignited by the auxiliary flame 80 (Fig. 3) formed around it and becomes the main flame 90.

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

On the other hand, although the amount of fuel passing through the regulating valve 60 changes almost in proportion to the turbine load, the number of open stop valves 50 changes according to the amount of fuel. The amount of fuel supplied to the premix cylinder is substantially constant, and the air ratio of the air-fuel mixture generated in the premix cylinder 16 does not change significantly. Therefore, in this embodiment, the air ratio is from 1.2 to 2. 5 is set.

In this embodiment, since the premixed air of the auxiliary nozzle 15 is set to a range in which the air ratio is close to 1 and the flame holding property is good, the premixed air from the main nozzle 14 is 20 mZ s or more. Preferably, even at a high speed of 40 m / ~ 70 m / s, there is no danger of blowing out. In addition, since the main nozzle 14 constantly blows air at a high speed of 20 m / s to 70 ms, there is no danger of flashback.

Furthermore, the premixed gas from the main nozzle 14 is stably burned by the auxiliary flame, even if the air ratio is lean such as 1.5 or more.

Fig. 5 (a), (b) and 6th (a), (b) show the NOx and CO emissions when the premixed air is burned with the air ratio changed. It shows the relationship. In Fig. 5 (a), the inner diameter of the combustion cylinder is ^ 90 ran, height 7 '; mm, Fig. 5 (b) shows the combustion cylinder when the premixed flame is formed under the same combustion conditions when the inside diameter of the combustion cylinder is 0 2 O 8 ran and the height is 6 24. This is the result of analysis of the exhaust gas.

Fig. 5 (b) shows the analysis of exhaust gas up to the high air ratio range of 3.6. In Figs. 5 (a) and 5 (b), the main flame has an air ratio of 1.5 or more, so the amount of N0X generated is markedly small and small as shown in 181, CO, CO, H ₂ is almost zero, as seen in 1991 and 201 respectively. Of course, 02 shows 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 generated NOx increases, but the fuel ratio of the auxiliary flame is about 10% at the rated load, so the overall Therefore, the amount of N〇 X generated is reduced.

Fig. 7 shows the sampling and probe movement from the center of the nozzle to the five thighs in the downstream direction from the main nozzle (inner diameter of about 26 mm), and sampling and analysis of the fuel gas from the center of the nozzle. This is a study of the combustion state near, and the auxiliary flame. As can be seen from the figure, almost no CH4 burns inside the main flame, but CH4 burns as it approaches the auxiliary flame, and above the auxiliary flame nozzle, CH4 burns 100%. ing. In other words, the main flame starts from the auxiliary flame of the auxiliary nozzle. It can be seen that the nozzle was surely transferred to the premixed gas. The dimension of the wrench used in this example is 26 for the main nozzle inner diameter, the spacer thickness around the main nozzle is 2 ran, and the auxiliary nozzle is 2 nm.

Fig. 8 shows that the main nozzles provided on the end wall on the head side of the combustor inner cylinder are divided into three groups, and the main nozzles blow out when the turbine load is varied in the range of 20% to 100%. The amount of fuel supplied to each nozzle group is independently increased or decreased so that the air ratio of the fuel-air mixture becomes within the range of 1 * 2 to 2,5. This is an example of a gas turbine combustor that suppresses the amount of NOx and CO generated. The numbers given to the main nozzles in the combustor · front view shown in Fig. 9 are the classification numbers of the main nozzle group divided into three. The number of main nozzles in each nozzle group was four. 6 1, 6 2, 6 3 are flow regulating valves, 61 increases / decreases the amount of fuel supplied to the second nozzle group, 62 is the first nozzle group, and −63 is the third nozzle group. Adjustment valve. Reference numeral 19 denotes a diffusion flame parner for igniting a pilot frame formed in the auxiliary nozzle, which stops supplying the feed after forming the pilot frame in the auxiliary nozzle. And the flame is extinguished.

Fig. 10 shows the change in the amount of fuel supplied to each nozzle group when the load on the gas turbine combustor in Fig. 8 was changed. Things. Turbine load: From 0% to 39%, fuel was supplied only to the first nozzle group, and when the air ratio of the dominate-air premixed gas ejected from the main nozzle became 1.25. Then, the fuel supply is reduced until the air ratio becomes 2.5, and at the same time, the fuel is supplied to the second nozzle group so that the air ratio becomes 2.5, and the amount of fuel supplied to the second nozzle group is fixed. By increasing the amount of fuel supplied to the first nozzle group below, the turbine load increases from 39% to 60%. Further, when the air ratio of the fuel-air mixture gas in the first nozzle group became 1.25, the supply fuel was reduced until the air ratio in the first nozzle group became 2.5, and at the same time, the third nozzle group So that the air ratio becomes 2.5. Turbine load: From 60% to 100%, the amount of fuel supplied to the first, second and third nozzle groups is proportional. When the bin load is 100%, the operation is performed so that the air ratio of the fuel-air mixture gas ejected from the first, second, and third nozzles becomes 1.5.

Under the gas turbine operating conditions shown in Fig. 10, when the turbine load is between 20% and 100%, the air ratio of the fuel-air mixture gas ejected from the first, second, and third nozzle groups is reduced. It is between 1.25 and 2.50. As can be seen from Fig. 6 (a) and (b), when the air ratio is between 1.25 and 2.50, the generated N0X is almost 100 ppm or less, and the Since the amount of CO, Ha, and CH4 generated is almost small, it can be said that this method of operating a gas turbine combustor is effective as a gas turbine combustion method for low NOX.

In the present invention described above, the auxiliary flame having a low ejection speed is used as an auxiliary flame for igniting and maintaining a premixed flame (main flame) having a high ejection speed. Therefore, the injection speed of the premixed gas to form a pilot flame for flame holding is set to approximately 0.4 m / s, the same as the combustion speed, and by setting the air ratio to 0.8 to 1.2, NO x And to prevent blowout. By enclosing the entire periphery of the premixture that gushes at a high blast speed with an auxiliary flame for flame holding, the heat generated by the flame for flame holding can be efficiently transmitted to the main flame. it can. Furthermore, the vortex formed by the velocity difference of the jet of the fuel stably flows between the main flame auxiliary and the auxiliary flame parner, and between the main flame premixed air and the auxiliary flame premixed air. Provide a spacer as large as possible, and use the iron to promote the mixing of the premixed gas with a high air ratio for the main flame and the combustion gas from the high-temperature trapping flame. It can promote ignitability. In addition, when the main flame and the auxiliary flame are separated by a thin wall such as a knife edge without using a spacer, the flow of the auxiliary flame is determined by the jet of the main flame. In the experiment where the main flame was blown out and the main flame blown out, the auxiliary flame also went out. It is clear. Therefore, by providing a spacer, the main flame and the auxiliary flame do not directly mix near the burner outlet, and some of the rainy people mix in the vortex formed by the spacer. Since the auxiliary flame can always be stably formed without being affected by the main flame, the effect of increasing the range of the flow velocity or air ratio at which the main flame is stably formed can also be obtained.

Claims

The scope of the claims

1. A cylindrical combustion chamber (20), a plurality of cylindrical main nozzles (14) provided on an upstream end wall of the combustion chamber, and an auxiliary nozzle (15) formed on an outer peripheral portion of the main nozzle. A main premixed air supply means (17, 18) for supplying a premixed air to the main nozzle (14); and a premixed air having an air ratio smaller than the main premixed air to the auxiliary nozzle (15). A gas turbine combustor characterized by comprising a supplementary premixed gas supply means (31) for supplying.

2 A cylindrical main nozzle (14) provided on the upstream end wall of the _β- cylindrical combustion and firing chamber (20), and a catching nozzle (15) formed on the outer periphery of the main nozzle (14) A main premixed air supply means (17, 18) for supplying a premixed air to the main nozzle (14); and a premixed air having an air ratio smaller than the main premixed air to the auxiliary nozzle (15). A gas turbine combustor characterized by comprising an auxiliary premixed gas supply means (31) to be supplied.

3. A plurality of cylindrical main nozzles (14) provided on the upstream end wall of the cylindrical combustion chamber (20), and concentrically formed on the outer periphery of each of the main nozzles (14). Auxiliary nozzle (15), main premixed air supply means (17, 18) for supplying a premixed air to the main nozzle (14), and auxiliary premixing for supplying a premixed air to the auxiliary nozzle (15) A gas turbine combustor characterized by having a gas supply means (31).

4. A plurality of cylindrical main nozzles (14) provided on the upstream end wall of the cylindrical combustion chamber (20), and an auxiliary formed concentrically around the outer periphery of each of the main nozzles (14). A nozzle (15), main premixed air supply means (17, 18) for supplying a premixed air having an air ratio greater than 1 to the main nozzle (14), and an air ratio to the auxiliary nozzle (15). A gas turbine combustor characterized by comprising auxiliary premixed gas supply means (31) for supplying 0.8 to 1.2 premixed gas.

5. A plurality of cylindrical main nozzles (14) provided on the upstream end wall of the cylindrical combustion chamber (20), and an auxiliary formed concentrically around the outer periphery of each of the main nozzles (14). A nozzle (15); main premixed gas supply means (17, 18) for supplying a premixed gas to the main nozzle (14) at an ejection speed greater than a combustion speed of the premixed gas; (15) A gas turbine combustor comprising an auxiliary premixed gas supply means (31) for supplying the premixed gas at an ejection speed substantially equal to the burning speed of the premixed gas.

A plurality of cylindrical main nozzles (14) provided on the upstream end wall of the tubular firing chamber (20), and auxiliary nozzles formed in an annular shape on the outer periphery of each of the main nozzles (14). A main premixed air supply means (17, 18) for supplying a premixed air having an air ratio greater than 1 to the main nozzle (14) at an ejection speed of 20 mZ seconds or more to the nozzle (15); The auxiliary nozzle (15) has an air ratio of 0.8 to 1.2. A gas turbine combustor characterized by comprising auxiliary premixed gas supply means (31) for supplying the premixed gas at an ejection speed substantially equal to the combustion speed of the premixed gas.

The premixed gas ejected from the opening of the cylindrical main nozzle (14) is combusted by a premixed flame (80) formed on the outer periphery of the opening of the main nozzle (14). Premixed combustion method for gas turbine combustor.

A premixed air mixture with an air ratio of 1 greater than that of the main nozzle (14) is jetted at a speed of 20 mZ seconds or more from the opening of the main nozzle (14). A premixed combustion method for a gas turbine combustor, characterized by burning with the formed premixed flame (80).

A premixed air having an air ratio of one greater was blown out from the opening of the cylindrical main nozzle (14), and the air ratio formed on the outer periphery of the opening of the main nozzle (14) was zero. A premixed combustion method for a gas turbine combustor, characterized in that combustion is performed with 8 to 1 and 2 premixed flames (80).

The premixed air having an air ratio greater than 1 is ejected from the opening of the cylindrical main nozzle (14) at an ejection speed higher than the combustion speed of the premixed air, and the main nozzle (14) is discharged. A premixed combustion method for a gas turbine combustor, characterized in that combustion is performed by a premixed flame (80) formed on the outer periphery of the opening of the gas turbine.