JP3951155B2 - Low NOx steam injection combustor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a low NOx combustor for a gas turbine, and more particularly to a low NOx steam injection combustor in which output is increased by steam injection.
[0002]
[Prior art]
In order to protect the environment, it is obliged to reduce NOx (nitrogen oxides) in the combustion exhaust gas of the gas turbine. Must be:
[0003]
The cause of this NOx is that nitrogen in the air is oxidized by the high temperature flame at the time of combustion. To reduce this, it is effective to reduce the hot spots in the flame and eliminate the generation of the high temperature flame. It is.
A lean premix combustor is known as a combustor capable of reducing NOx. This lean premix combustor premixes fuel with a sufficient amount of air, homogenizes it, and burns it lean. Since the optimum combustion temperature is higher than the heat-resistant temperature on the turbine side, diluted air is mixed into the combustion gas and the temperature is lowered to a temperature suitable for the turbine side, and supplied to the turbine. This diluted air also has the function of making the temperature of the mixed gas uniform.
[0004]
[Problems to be solved by the invention]
When increasing the output of the lean premix combustor, steam can be injected into the inner cylinder, and fuel can be injected and combusted as the temperature decreases, thereby increasing the output. In this case, when the steam is injected into the combustion region, the combustion stability is impaired. Further, in order to increase the air from the air intake port of the fuel injection unit corresponding to the increased fuel, a device for reducing the area of the diluted air intake port of the inner cylinder is required.
[0005]
The present invention has been developed to solve such problems. That is, the object of the present invention is to prevent instability of combustion due to steam injection and to limit the air inflow from the dilution air intake with a simple structure so that the air from the air intake of the fuel injection portion increases. It is to provide a low NOx steam injection combustor.
[0006]
In order to achieve the above object, according to the first aspect of the present invention, an inner cylinder having a substantially cylindrical shape and an upper part serving as a combustion chamber and having a dilution air intake at the lower part of the combustion chamber, and an outer cylinder surrounding the inner cylinder. A cylindrical premixing pipe whose lower end communicates with the inner cylinder at the top of the inner cylinder and has a premixing space inside, and fuel in the premixing space above the premixing space. A fuel injection part for injecting the fuel, and a steam injection part having a steam injection port adjacent to the dilution air intake,
A cross-sectional area of the premix space perpendicular to the axis of the inner cylinder is smaller than a cross-sectional area of the combustion chamber perpendicular to the axis of the inner cylinder;
The fuel injection part is provided with a pressurized air intake,
A space between the outer cylinder and the inner cylinder communicates with the dilution air inlet and the pressurized air inlet, and pressurized air is supplied to the space, and the pressurized air is supplied to the pressurized air inlet. Through the fuel injection part,
The fuel injection unit injects the pressurized air introduced through the pressurized air intake port into the premixing space together with fuel, and premixes the pressurized air and fuel in the premixing space;
During normal operation, the pressurized air between the outer cylinder and the inner cylinder is not only introduced into the fuel injection section through the pressurized air intake, but also into the inner cylinder through the dilution air intake. Introduced,
When the output is increased, the amount of fuel injected from the fuel injection unit is increased, and steam is injected from the steam injection port, so that the pressurized air between the outer cylinder and the inner cylinder becomes the diluted air. Inflow from the intake port is restricted, and the restricted pressurized air is supplied to the pressurized air intake port, whereby the pressurized air introduced into the fuel injection unit is increased. A low NOx steam injection combustor is provided.
[0007]
With the above configuration, when the output is increased, the steam is injected from the diluted air intake provided in the lower part of the combustion chamber, so that the combustion in the combustion region is not adversely affected. In addition, this steam injection limits the amount of air that has flowed from the dilution air intake port until now. This restricted and non-entering air enters from the air intake of the fuel injector and is used for increased fuel combustion. Since the inflow of dilution air can be restricted by injecting steam in this way, it is not necessary to provide a special device for restricting the inflow of dilution air.
[0008]
According to a second aspect of the present invention, the steam injection port is approximately the same size as the dilution air intake port.
[0009]
When the steam injection port is almost the same size as the dilution air intake port and they are arranged close to each other and the steam is injected from the steam injection port, the entire amount flows into the inner cylinder, but the ambient air is also sucked in somewhat by the ejector action. . However, the amount of air sucked is smaller than the amount of air that flows in when steam is not injected, and the air flow rate is limited by steam.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described below with reference to the drawings. In each figure, common portions are denoted by the same reference numerals, and redundant description is omitted.
FIG. 1 is an overall configuration diagram of a low NOx steam injection combustor for a gas turbine according to the present invention. As shown in this figure, the low NOx steam injection combustor 1 of the present invention includes a pilot combustor 12 disposed in the central portion and a plurality (only one is shown in the figure) disposed around the pilot combustor 12. And a combustor 14. In this figure, 2 is an inner cylinder (liner), 3 is a casing (outer cylinder), 4 is a spark plug (igniter), and air 6 flows between the casing 3 and the liner 2 to combustors 12 and 14. Reaches the liner 2 through the combustors 12 and 14 and other portions to form flames 7 and 8, and the generated combustion exhaust gas 9 is guided to a gas turbine (not shown) through the scroll portion 2c. , This is supposed to drive.
[0011]
In FIG. 1, the main combustor 14 includes a main injection valve 15 arranged coaxially with each other, an air intake 15 a provided in the main injection valve 15, and a pre-evaporation premixing pipe 16. Fuel F is supplied to the main injection valve 15 from the outside through the casing 3. As this fuel, it is preferable to use a fuel having a small nitrogen component that causes fuel NOx, such as gas fuel, kerosene, light oil, A heavy oil, or the like. Since pressurized air is supplied into the casing 3 from below, air flows in from the air intake port 15a. The pre-evaporation premixing pipe 16 is a cylindrical tube whose lower end is opened in this figure, and the fuel and air are easily mixed inside. That is, the main combustor 14 is a premixed lean combustor configured by a main injection valve 15, an air intake 15 a and a prevaporization premixing pipe 16. With this configuration, the fuel F is injected into the pre-evaporation premixing pipe 16 by the main injection valve 15, the air corresponding to the fuel supplied from the air intake port 15 a flows in, and the fuel F in the pre-evaporation premixing pipe 16. Can be premixed with a sufficient amount of air to evaporate and be lean burned.
[0012]
In FIG. 1, the pilot combustor 12 includes a pilot injection valve 13a, a pilot chamber 13b, and an air intake port 13c arranged coaxially with each other. The pilot combustor 12 is a diffusion combustor capable of stable combustion, in which fuel is injected into the pilot chamber 13b by the pilot injection valve 13a, air flows in from the air intake port 13c, and the fuel diffuses into the air. It is supposed to burn while. Further, the ignition part of the spark plug 4 is located in the pilot chamber 13b, and ignites the mixed gas diffused to each other. With this configuration, the diffusion flame 7 can be stably formed inside the liner 2.
[0013]
In FIG. 1, the liner 2 (inner cylinder) has a hollow cylindrical shape and is provided with a top plate and a bottom plate. The top plate is provided with a pilot combustor 12 and a main combustor 14, and a plurality of air inlets 2d are provided. Yes. A considerable amount of air rising while cooling the periphery of the liner 2 flows into the air intakes 13c and 15a provided in the pilot combustor 12 and the main combustor 14, respectively, and the rest from the air inlet 2d. Inflow. The bottom plate is provided with a turbine passage 10 through which combustion exhaust gas is sent to the turbine. The upper portion of the liner 2 constitutes a combustion chamber 2 a, a plurality of dilution air intakes 20 are provided on the outer periphery of the central portion 2 b, and the lower portion is a scroll chamber 2 c that is connected to the turbine passage 10. In the vicinity of the dilution air intake port 20, a steam injection pipe 22 having the same diameter as the intake port 20 is provided for each dilution air intake port 20, and a steam supply device (not shown) is connected to the vapor injection pipe 22. Has been. The pressurized air is taken in from the lower part of the dilution air intake 20 and rises while cooling the liner 2, and the dilution air intake 20, the air inlet 2 d of the liner top plate, the pilot combustor 12 and the main combustor 14. From the air inlets 13c and 15a.
[0014]
FIG. 2 shows the relationship between the diluted air intake 20 and the steam injection pipe 22 and shows the air inflow state during normal operation. The dilution air intake 20 and the steam injection pipe 22 are provided at a distance t, and the diameter D of the dilution air intake 20 and the inner diameter d of the steam injection pipe 22 are substantially the same size. The distance t has a desired air flow rate and is as short as possible. The diameter D of the dilution air intake 20 and the inner diameter d of the steam injection pipe 22 are set to be substantially the same size. During this normal operation, since the steam is not injected from the steam injection pipe 22, the air 6 flows from the diluted air intake 20.
[0015]
FIG. 3 shows a state at the time of steam injection. The steam 23 is injected over the diluted air intake 20 at a pressure higher than that of the surrounding pressurized air 6 and sucks some air 6 by the ejector action, but the inflow of the air 6 is greatly limited by the jet flow of the steam 23. Is done.
[0016]
Next, the operation will be described.
During normal operation, the pressurized air 6 supplied from the lower periphery of the liner rises along the liner 2, partly flows from the dilution air intake 20, and the rest rises while cooling the liner 2. The part flows in from the air inlet 2d of the liner top plate, and the rest flows into the air intakes 13c and 15a provided in the pilot combustor 12 and the main combustor 14, respectively. The inflowing air and fuel are premixed in the pilot combustor 12 and the main combustor 14 and burned in the combustion chamber 2a. In the combustion chamber 2a, combustion is performed by adding air flowing in from the air inlet 2d. The air flowing from the dilution air intake 20 is added to the combustion gas, and the temperature of the combustion gas is lowered to a temperature required on the turbine side and a uniform temperature distribution is obtained.
[0017]
When the output increases, steam is injected from the steam injection pipe 22. As a result, most of the air 6 flowing in from the dilution air intake 22 flows into the air intakes 13c and 15a provided in the pilot combustor 12 and the main combustor 14, respectively, and a part of the air in the liner top plate. It flows in from the inlet 2d. The pilot combustor 12 and the main combustor 14 increase and supply fuel according to the air inflow amount. Thus, stable low NOx combustion can be maintained even if the fuel is increased to increase the output. The inflowing steam 23 and the partially sucked air are uniformly mixed with the combustion gas, and the temperature of the combustion gas is lowered to a temperature required on the turbine side and a uniform temperature distribution is obtained.
[0018]
FIG. 4 is a diagram showing the relationship between the amount of steam, the equivalent ratio (fuel / air), and NOx when the fuel is increased by injecting steam into the combustion chamber. As the amount of steam is increased and the fuel is increased accordingly, the equivalence ratio increases and NOx also increases.
[0019]
FIG. 5 is a diagram showing the relationship between the amount of steam, the equivalence ratio, and NOx in the case of the present invention when steam is injected from the diluted air intake port 20 and the fuel is increased accordingly. In this case, the air whose inflow from the dilution air intake 20 is restricted by the steam flows into the air intakes 13c and 15a provided in the pilot combustor 12 and the main combustor 14, respectively, and a part of the liner top plate. Therefore, even if the fuel increases, the equivalence ratio does not change and the generation of NOx does not change.
[0020]
【The invention's effect】
As described above, the present invention increases the fuel because the air flowing from the diluted air intake by steam injection flows from the air intake provided in the pilot combustor and the main combustor, respectively. However, the equivalence ratio does not change, and the output can be increased without impairing the combustion stability. Further, since the combustion state is not changed, the low NOx state can be maintained without increasing the generation of NOx. In particular, when combined with a dry low NOx combustor (especially a premixed combustor with a narrow stable combustion range), low NOx operation can be performed over a wide load range from a load range that does not require steam injection to a steam injection range. In addition, since the intake of air into the combustor by steam injection is not provided with a special structure, it becomes a simple structure, which is advantageous in terms of manufacturing and cost.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a low NOx steam injection combustor according to the present invention.
FIG. 2 is a diagram showing a relationship between a diluted air intake port and a steam injection pipe and showing a state at the time of air intake.
FIG. 3 is a diagram showing a relationship between a diluted air intake port and a steam injection pipe and a state at the time of steam injection.
FIG. 4 is a diagram showing the relationship between the amount of steam, the equivalence ratio (fuel / air), and NOx when steam is injected into the combustion chamber to increase the fuel.
FIG. 5 is a diagram showing the relationship between the amount of steam, the equivalent ratio (fuel / air), and NOx when steam is injected into the diluted air intake port to increase the fuel.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Low NOx steam injection combustor 2 Liner 2a Combustion chamber 2b Center part 2c Scroll part 2d Air inlet 3 Casing 4 Spark plug (igniter)
6 Air 7 Diffusion flame 8 Premixed flame 9 Combustion exhaust gas 10 Turbine passage 12 Pilot combustor 13a Pilot injection valve 13b Pilot chamber 13c Air intake 14 Main combustor 15 Main injection valve 15a Air intake 16 Pre-evaporation premixing tube 20 Dilution Air intake port 22 Steam injection tube 23 Steam

Claims (2)

It is substantially cylindrical and the upper part is a combustion chamber, an inner cylinder having a dilution air intake at the lower part of the combustion chamber, an outer cylinder surrounding the inner cylinder, and a lower end of the inner cylinder at the top of the inner cylinder . A cylindrical premixing tube that communicates with the inside of the cylinder and has a premixing space inside, a fuel injection section that injects fuel into the premixing space above the premixing space, and the dilution air intake port. A steam injection part having a steam injection port in proximity,
A cross-sectional area of the premix space perpendicular to the axis of the inner cylinder is smaller than a cross-sectional area of the combustion chamber perpendicular to the axis of the inner cylinder;
The fuel injection part is provided with a pressurized air intake,
A space between the outer cylinder and the inner cylinder communicates with the dilution air inlet and the pressurized air inlet, and pressurized air is supplied to the space, and the pressurized air is supplied to the pressurized air inlet. Through the fuel injection part,
The fuel injection unit injects the pressurized air introduced through the pressurized air intake port into the premixing space together with fuel, and premixes the pressurized air and fuel in the premixing space;
During normal operation, the pressurized air between the outer cylinder and the inner cylinder is not only introduced into the fuel injection section through the pressurized air intake, but also into the inner cylinder through the dilution air intake. Introduced,
When the output is increased, the amount of fuel injected from the fuel injection unit is increased, and steam is injected from the steam injection port, so that the pressurized air between the outer cylinder and the inner cylinder becomes the diluted air. Inflow from the intake port is restricted, and the restricted pressurized air is supplied to the pressurized air intake port, whereby the pressurized air introduced into the fuel injection unit is increased. A low NOx steam injection combustor.   2. The low NOx steam injection combustor according to claim 1, wherein the steam injection port is substantially the same size as the dilution air intake port.

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