JPS59173633A - Gas turbine combustor - Google Patents

Abstract

PURPOSE:To contrive to reduce nitrogen oxides in exhaust gas by a structure wherein a premixing chamber to mix fuel with combustion air is arranged at the head of a combustor and a main combustion chamber is arranged on the downstream side of the premixing chamber. CONSTITUTION:A premixing chamber 25 to mix fuel with combustion air is arranged at the head of a combustor so as to perform premixed combustion in order to prevent hot spots from generating in flame and consequently to check the generation of NOx strikingly and at the same time a main combustion chamber 26, the diameter of which is larger than that of the premixing chamber, is arranged on the downstream side of the premixing chamber 25. In addition, pilot burners to perform diffusion combustion are arranged at the junction part of the premixing chamber 25 and the main combustion chamber 26 so as to generate pilot flame in order to prevent an engine from overcooling. In such a manner as mentioned above, NOx, CO and HC in exhaust gas are strikingly reduced.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a combustor for supplying high-temperature, high-pressure working gas to a gas turbine, and is particularly improved to suppress the generation of air pollutants. It relates to a gas turbine combustor.

[Prior art]

In general, nitrogen oxides (No) and carbon oxides (Co) generated during the combustion process are air pollutants, and in gas turbines in particular, reducing the emissions of these substances can improve turbine performance. This is an equally important issue. N
In order to suppress the generation of O, a common method is the so-called lean low-temperature combustion method in which combustion is performed using excess air to lower the temperature of high-temperature combustion gas. However, supplying excess air and performing low-temperature combustion also reduces combustibility due to supercooling, causing CO-? This causes an increase in the generation of uncombustible components such as HC. For this reason, in a gas turbine combustor, the reduction of NOx and the reduction of unburned substances such as CO and HC are contradictory, and the key to improving the gas turbine combustor is to eliminate these simultaneously. The so-called premix combustion method, in which air and fuel are mixed in advance and combusted, is known to increase the effect of reducing NO emissions, but in this method, the mixture ratio of fuel and air becomes either too rich or too light. The disadvantage is that the combustion condition deteriorates and the amount of unburned hydrocarbons (HC) produced increases.

Therefore, effectively and uniformly cooling the flame with as little air as possible and preventing the formation of supercooled areas is very advantageous in reducing NO and preventing CO generation. Specifically, it forms a uniform flame and effectively NO! One way to reduce this is to form a main combustion chamber in the head combustion chamber and its downstream side, and supply fuel to two stages. A so-called two-stage combustion method is used. This method maintains the flame during the head combustion and dawn, and the combustion supply from the second stage performs combustion with excess air, increasing the effect of reducing NO, but the effect of the flame forming in the head combustion chamber increases. This method has disadvantages such as a large amount of carbon dioxide, making it impossible to obtain a low NO effect, and generation of uncombusted components during second-stage combustion and supply.

FIG. 1 is a longitudinal sectional view of a conventional gas turbine combustor of the two-stage combustion type and premix combustion type described above.

A gas turbine is an air compressor1. Turbine 2. and the combustor 3 as the main groove forming member. 4 is a load (for example, a generator). Air 5 compressed to about lθ atmospheric pressure is sent to the combustor 3. The combustor 3 has an inner combustion cylinder 6, an outer cylinder 7, and a cover 8 attached to the side closing part, and the cover 8 has an inner combustion chamber to which an ejection nozzle 10 for a primary fuel 9 and a supply part 12 for a secondary fuel 11 are attached. The head combustion chamber 14 forms the m6ra head flame 13, and the main combustion chamber 15 performs lean low-temperature combustion of secondary fuel in the wake section. The head combustion chamber 14 contains primary fuel and air from the air holes and wall cooling holes.
is supplied to form a head flame, but mainly air flow 16.1
7 and the primary fuel 9 are subjected to diffusion combustion. Further, air flows 21 and 22 and a mixed fuel 23 of the secondary fuel 11 and the excess air flow 19 are supplied to the main combustion chamber, thereby forming a premixed combustion flame 20, resulting in lean low-temperature combustion due to premixed combustion. Achieve low NO by controlling. However, the head flame 13 formed in the head combustion chamber 14 performs high-temperature combustion, and this head flame 13 is located inside the combustor inner cylinder 6.
It occupies a large area in part Q. Additionally, airflow from the surroundings17. Since it cannot be mixed uniformly with the same No. 18, a large amount of NOa is generated. Therefore, in the premixed combustion flame 20, N
Even if the generation of O is suppressed, the overall amount of NO generated cannot be significantly reduced. On the other hand 1. excess air 1
However, in the process of supplying the fuel 11 to the air 19, at low load when the fuel 11 supply is very low, the fuel concentration becomes lighter than the air or air 19, that is, the fuel 11 becomes overly concentrated. Because it is a cooling combustion, combustion due to supercooling is inhibited, resulting in the production of unused substances such as CO and F (C).
It has the disadvantage of emitting a large amount of combustible matter. (9) Re-burning of unburned components is also possible due to the head flame 13. Since there is cooling air 18 near the head wall surface, the head flame 13, which is a pilot flame, and the premix flame 20 are Since a layer of cooling air is formed between the
It is not possible to completely reduce C, etc. Therefore, 2
Measures have been attempted to change the supply direction of the secondary mixed fuel to the above-mentioned head flame, but since more fuel is supplied to the head flame, the combustion temperature in the center of the combustor will be even higher. This has the disadvantage of increasing the occurrence of As described above, in the conventional technology, it is not possible to simultaneously reduce NO and CO to a large extent.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and is aimed at reducing NO in exhaust gas.
, and also CO,f(C).

[Summary of the invention]

The basic principle of the device of the present invention, which achieves the above object or not, will be briefly described below.

The gas turbine combustor of the present invention effectively performs premix combustion to prevent hot spots 7) in the flame, thereby greatly suppressing the generation of NO, while generating a pilot flame at an appropriate location. HC-? which prevents supercooling and is an unburned component. This suppresses the generation of CO.

Based on the above-mentioned principles, the above-mentioned objectives (NO,.

In order to achieve simultaneous reduction of CO, H, and C, the device of the present invention is equipped with a premixing chamber for mixing fuel and combustion air at the head of the combustor, and a premixing chamber on the downstream side of the premixing chamber. The present invention is characterized in that a main combustion chamber having a diameter larger than that of the premixing chamber is provided, and a pilot burner for performing diffusion combustion is provided at the connection between the premixing chamber and the main combustion chamber.

[Embodiments of the invention]

Next, one embodiment of the present invention will be described with reference to FIGS. 2 to 4.

FIG. 2 is a longitudinal sectional view showing an embodiment of the gas turbine combustor of the present invention.

A head premixing chamber 25 is provided at the head (ie, the upstream end) of the combustor inner cylinder 24, and a premixing cylinder 28 is provided therein.

The premix cylinder 28 is a cylindrical member (with a taper in this example) for mixing the fuel 26 and air (indicated by an arrow) 27 to be subjected to premix combustion. The spout hole 48 is drilled.

A plurality of fuel nozzles 3 are installed around the downstream end of the head premixing chamber 25 to form a pilot flame 29.
0 is arranged.

Each of the fuel nozzles 30 described above is provided with a swirler 32 for giving swirl to the airflow, and each nozzle 30 is configured to independently have a flame-holding function.

The fuel ejected from the nozzle 30 may be any fuel, whether liquid or gas, and is characterized by being a diffusive combustion flame that forms a stable flame even in a wide range of combustion conditions. Further, immediately on the outer peripheral side of this pilot flame, fuel 33 and secondary air 34 are mixed outside the combustor inner cylinder 24 and then supplied to the main combustion chamber 36 as a swirling flow by the swirling vanes 35 to create a premixed flame. 37b. An air inlet hole 38 for cooling the wall surface of the main chamber and a dilution air hole 39 near the outlet are formed in the wall surface of the main chamber.

FIG. 3 is a cutaway perspective view showing the above-mentioned head premixing chamber 25, a pilot burner fuel nozzle 30 provided near its outlet, and a secondary fuel supply section 40. A pilot flame forming section 38 having a diameter larger than that of the head premixing chamber 25 is provided near the downstream end of the head premixing chamber 25, and a pilot flame forming section 38 having a diameter larger than that of the pilot flame forming section 8 is provided outside of the pilot flame forming section 38. A large main combustion chamber 36 is present, and a secondary fuel supply section 40 opens at the connection between the pilot flame forming section 8 and the main combustion chamber 36 .

The secondary fuel 33 is guided to a fuel tank 41 and receives fuel spray from a plurality of fuel supply pipes 43 before a swirling blade 42 that swirls the secondary fuel and secondary air. Reference numeral 44 denotes an ejection hole bored in the fuel supply pipe 43 described above.

In this example, a premixing chamber 45 is formed between the fuel reservoir inner wall 47 and the pilot flame former outer wall extension 46, in which the secondary fuel 33 and the air stream are mixed.

Next, the formation of flame in the combustor configured as above will be described.

(See Figure 2) The fuel premixed in the head premixing cylinder 28 is injected into the premixing chamber 25 from the plurality of injection holes 48, mixed with the air flow from the plurality of air holes 49, and premixed. It will be in a mixed state. That is, excess premixed fuel is supplied from the premix cylinder 28 and further mixed with air from the premix chamber 25, resulting in premix combustion with excess air. In this example, a mechanism for maintaining flame intensity is not provided in the premixing chamber 25, and the axial flow velocity is increased, so the flame is maintained at the tip of the premixing inner cylinder 28. It becomes a flame 37a.

This makes it possible to significantly reduce N08. However, at a position close to the wall of the premixing chamber, there is no uniform premixing and there is always an excess of air, resulting in a large amount of unburned fuel.

For this reason, the apparatus of the present invention is configured to form a pilot flame near the outlet of the premixing chamber to promote reburning of the unburned products.

On the other hand, the secondary fuel also performs premix combustion with the air flow to form a premix flame near the wall of the main combustion chamber, making it possible to significantly reduce NO. Furthermore, when the amount of fuel 33 is reduced to reduce the amount of combustion, the generation of CO and IC caused by so-called supercooling caused by excess air is suppressed because re-combustion can be performed in the main combustion chamber by the pilot flame 29. can do.

FIG. 4 is an explanatory diagram of the flame generation state. As shown in this figure, the pilot flame forming nozzle 30 has a swirler 32 around it that supplies a swirling air flow, and the supplied fuel can be either liquid or gas, but in the case of liquid, high pressure energy is used to supply the fuel. Either a spray structure that atomizes the droplets or a system that atomizes the atomization using the gas force of high-pressure air or steam is suitable. FIG. 4 shows the case of gaseous fuel supply, in which the fuel is supplied so as to mix with the swirling air flow to form a so-called -φ diffusion combustion flame. Diffusive combustion flames always have areas with high fuel concentration, so stable combustion can be maintained over a wide range.

Further, since the pilot flame has a flame-holding effect due to the recirculation flow 53 generated by the swirling air flow 52, the pilot flame continues stably.

Forming the pilot flame outside the outlet of the head combustion chamber in this way can also be applied when the head combustion chamber performs diffusion combustion. In other words, even in the case of diffuse combustion, low NO
In order to improve the combustion efficiency, a combustion method is used in which air is supplied in excess, but the combustion temperature in the center of the combustor is relatively high and no unburned components are generated, but due to the wall cooling air flow and the absorption of radiant heat by the wall, Because the combustion temperature is low and supercooling occurs, Co
, HC and other unburned phosphorus are generated, but by forming a pilot flame according to the present invention, re-combustion becomes possible and CO, HC, etc. are generated.
IC generation can be suppressed.

FIG. 5 is a chart showing an example of fuel flow rate control in the above embodiment, and the horizontal axis represents the load factor of the gas turbine. FI is the fuel flow rate for obtaining a pilot flame, F1' is the primary fuel flow rate of the head premixing chamber 25-, F2 is the secondary fuel flow rate, and Ft is the total fuel flow rate.

Now, looking at the case where the gas turbine is ignited at 10 points in the figure and the load is gradually applied to the gas turbine, after ignition, the start-up is performed using only the pilot flame until the load start point T1, and from no load to approximately 172 loads. Primary fuel is supplied, and secondary fuel is further supplied from 1/2 load to full load. However, 80
% load, the pilot fuel supply is stopped. This is because the effect of the pilot flame in suppressing the generation of unburned components by only the primary fuel is up to 20% load), and at loads higher than this, if the primary fuel flow rate is large, the amount of combustion increases, and CO , there is no supercooled part that causes IC generation. In addition, the impact on secondary fuel alone was 80%.
If the temperature exceeds that level, there will be no supercooled portion for the same reason as for the primary fuel.

Therefore, at a load of 80% or more, the presence of the pilot flame forms a high-temperature region within the combustor, which actually becomes a factor that increases the production of NOl. Therefore, at this point (80% load), fuel supply to the pilot flame is stopped, so-called premix combustion using only primary and secondary fuels is eliminated, and only so-called premix combustion is performed using only primary and secondary fuels. By achieving uniform low-temperature combustion, it is possible to significantly reduce NO. By performing such fuel control on pilot flame formation, the present invention provides a combustor that eliminates the generation of CO1HC under a wide range of operating conditions from ignition to rated load, and achieves a significantly low No. be able to. This situation is shown in FIG. The vertical axis of this figure is the reduction rate regarding No., CQ and HC, that is,
This is the concentration in this example/the strength in the conventional device.

When the load factor was 100% (rated) and the load factor was 100% (rated), the NO.-decrease rate was 0.4, achieving a 60% reduction compared to the conventional device.

The reason why the reduction rate curve for NOYO is discontinuously better in the high load region than at the point of about 80% load is that the high temperature part disappeared because the pilot flame was stopped. On the other hand, C0
For 9HC, CO, CO,
The effect of reducing HCj by 1 degree appears.

〔Effect of the invention〕

As explained above, the gas turbine combustor of the present invention has
A premixing chamber for mixing fuel and combustion air is provided at the head of the combustor, and a main combustion chamber having a larger diameter than the premixing chamber is provided downstream of the premixing chamber, and By installing a pilot burner that performs diffusion combustion at the connection between the premixing chamber and the main combustion chamber, it has the excellent practical effect of significantly reducing NO emissions in the exhaust gas, as well as reducing Co and HC. play.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of a low NO type combustor according to the prior art.
2 to 8 show the gas turbine combustor of the present invention, FIG. 2 is a longitudinal sectional view, FIG. 3 is a partially cutaway perspective view, and FIG. 4 is an explanation of the flame generation state. Figure 5 is a chart showing the fuel control status, Figure 6 is No, , co and HC.
2 is a chart showing the reduction effect of 3...Combustor, 25...Head premixing chamber, 26...
Primary fuel, 28... Premix cylinder, 30... Pilot flame fuel nozzle, 33... Secondary fuel, 37 a *
37 b... Premixed combustion flame, 54... Pilot fuel. Agent Patent Attorney Masami Akimoku Figure 3 Figure 6 puγmatahiso-mu<γ. Continued from page 1 of 0 Inventor: Michio Kuroda, 502 Kandachi-cho, Tsuchiura City, Hitachi, Ltd. Mechanical Research Laboratory, 0 Inventor: Katsuo Wada, 3-1-1, Saiwai-cho, Hitachi City, % formula % Procedural amendment, Showa; July 20, 1955 Kazuo Wakasugi, Commissioner of the Japan Patent Office 1, Indication of the case Showa SS Year Patent Application No.≠6θ03 shi J2, Title of the invention Gas turbine combustor 3, Name of the person making the amendment (Name) (510) Co., Ltd. Hitachi 4,
agent

Claims (1)

[Claims] A premixing chamber for mixing fuel and combustion air is provided at the head of the combustor, and a large-diameter main body is provided on the downstream side of the premixing chamber. A gas turbine combustor comprising a combustion chamber and a pilot burner for performing diffusion combustion at the connection between the premixing chamber and the main combustion chamber. 2. A means for supplying a mixed gas of fuel and air is provided on the outer circumferential side of the pilot burner, and the mixed gas is diffused between the premixed flame generated in the premixing chamber and the mixed gas (flame caused by). The gas turbine combustor according to claim 1, characterized in that the gas turbine combustor is capable of forming a flame. 3. The pilot burner stops fuel injection when the gas turbine is in a high load state. The gas turbine combustor according to claim 2, characterized in that the gas turbine combustor is equipped with a control means configured to.