JPH06137559A - Combustor for gas turbine - Google Patents

Abstract

PURPOSE:To provide a combustor for a gas turbine in which radial mixture of the air and fuel gas in a main nozzle is made uniform, and a quantity of diffusion combustion in a pilot combustion chamber is reduced to improve a reduction in NOx. CONSTITUTION:The combustor for a gas turbine comprises a pilot swirler 7-containing type pilot nozzle 9 provided at a center to diffusion burn, an annular pilot premixing nozzle 6 coaxially surrounding an outer periphery of the nozzle to premixture burn, and a plurality of circular main swirler 8-containing type main nozzle 3 arranged at an equal interval along the outer periphery of the nozzle 6 to premixture burn.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to the structure of a gas fired gas turbine combustor.

[0002]

2. Description of the Related Art An example of a conventional combustor adopting a premixed combustion system to reduce NOx is shown in FIGS. In both combustors, a pilot combustor for diffusion combustion is placed in the center, and a main nozzle that creates a premixed air-fuel gas mixture is placed outside the pilot combustor. I do. First, in the combustor shown in FIG. 5, the main premixing nozzle 3 has an inward angle with respect to the center line of the combustor, and a plurality of (16 or more) main fuel nozzles are provided on the inner wall surface of the inlet of the combustion air. 4 are arranged. Further, in the structure shown in FIG. 6, the partition plate 17 is provided in the main premixing nozzles 3 and 3 '.
By inserting the fuel cells 4 into the dual main premixing nozzles.
It promotes the mixing of air and fuel gas.

[0003]

However, such a conventional structure has the following problems. (1) There is a limit to the reduction of NOx because the air and fuel gas in the main nozzle are not sufficiently mixed. That is, in the conventional combustor, the fuel nozzle is provided on the inner wall surface of the annular air passage. Therefore, if the number of fuel nozzles is increased in order to improve the mixing in the circumferential direction in the premix nozzle, the hole diameter of the fuel nozzle becomes smaller (fuel injection differential pressure is constant = total nozzle area is constant). Is reduced and the radial mixing is worse. (2) A large amount of NOx is generated in the pilot part where diffusion combustion is performed. That is, in the conventional combustor, since there is no swirler in the main premixing nozzle, the circulating flow in the inner cylinder of the combustor is small, so there is a relatively large amount of fuel from the diffusion pilot nozzle in order to secure flame holding property. Has become.

The present invention has been proposed in view of such circumstances, and makes the radial mixing of the air and the fuel gas in the main nozzle uniform and the amount of diffuse combustion in the pilot combustion chamber. An object of the present invention is to provide a gas turbine combustor that reduces the NOx and improves the NOx reduction.

[0005]

To this end, the present invention provides a pilot nozzle portion provided in a central portion for performing diffusion combustion,
An annular pilot premixing nozzle that coaxially surrounds the outer periphery of the pilot nozzle portion and performs premixed combustion, and a plurality of circles that are arranged at equal intervals along the outer periphery of the annular pilot premixing nozzle and that perform premixed combustion, respectively. It has a main nozzle with a built-in main swirler.

[0006]

According to this structure, the following actions are performed. (1) Generally, in the case of a premixed combustor, if the premixed air-fuel mixture is non-uniform, the flame temperature rises in the portion where the fuel concentration is high, and the amount of NOx generated increases. Therefore, by changing the shape of the main nozzle from an annular shape to a plurality of circular shapes and providing a swirler, the combustion air and the fuel gas can be mixed more uniformly. (2) By providing the premixing pilot nozzle in an annular shape around the diffusion pilot, a part of the pilot fuel that has been conventionally diffused and burned is premixed and burned, and a strong swirl is generated in the air flow of the premixed pilot nozzle. By providing a circulation region downstream of the entire pilot nozzle, the flame holding property of the entire combustor is not impaired. As a result, the fuel amount of diffusion pilot is 20% of the conventional one.
It is possible to reduce the amount to the following, and it is possible to significantly reduce NOx.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall longitudinal sectional view thereof, FIG. 2 is an enlarged view showing a pilot nozzle of FIG. 1, and FIG. 3 is a pilot nozzle and a main nozzle in FIG. 5 is a diagram showing the fuel distribution of FIG. 5 in comparison with Conventional Example 1 and Conventional Example 2 shown in FIG. 6, and FIG. 4 is an explanatory diagram showing layered combustion in the combustion chamber of FIG.

First, referring to FIGS. 1 and 2, the combustor of the present invention has a central pilot nozzle 9, a plurality of circular premixing main nozzles 3 surrounding the pilot nozzle 9 at equal intervals, and a combustor inner cylinder 5.
Composed of and. The pilot nozzle 9 has four small holes (FIG. 2) for the diffusion pilot at the tip thereof, and a small hole for the premix pilot is provided immediately downstream of the pilot swirler 7. The main fuel nozzle 4 also has a small hole for injecting fuel immediately downstream of the main swirler 8.
It is important to choose the number and diameter of the gas injection holes in the premix pilot nozzle 9 and the main fuel nozzle 4 so that they mix with the air in the pilot nozzle 9 and the main fuel nozzle 4 as uniformly as possible. In this embodiment, the number and diameter of the diffusion pilot, the premixing pilot, and the main gas injection holes are such that the ratio of the respective flow rates is 1 as shown in FIG.
It is necessary to make it 3%, 4-10%, 87-95%. By the way, in Conventional Example 1; Conventional Example 2, the flow rates of the diffusion pilot and the premix main are 30% and 70, respectively.
%; 7 to 15%, 85% to 93%. In the above embodiment, the average gas temperature at the combustor outlet is 1350 ° C. and NOx
Achieved 25 ppm @ 15% O ₂ .

In such a combustor structure, as shown in FIG. 4, the diffusion combustion section by the pilot nozzles 9 and the main nozzle 3 which are arranged on the same plane perpendicular to each other.
Combustion is performed in a three-layer structure in which a pilot premix combustion section is formed between the main premix combustion section and the main premix combustion section. Like this 3
By the stratified combustion, the fuel concentration is gradually reduced from the pilot diffusion combustion in the central part to the main premixed combustion on the outer side to facilitate flame propagation from the pilot to the main and to achieve low NOx.

[0010]

As a result, according to the structure of the present invention, the following effects can be obtained. (1) By changing the shape of the main nozzle from an annular shape to a plurality of circular shapes and providing a swirler,
The combustion air and the fuel gas can be mixed more uniformly. (2) By providing a premixed pilot nozzle in an annular shape around the diffusion pilot, a part of the pilot fuel that has been conventionally diffused and burned is premixed and burned, and a strong swirl is given to the airflow of the premixed pilot nozzle. As a result, NOx can be significantly reduced without impairing combustion stability.

In short, according to the present invention, a pilot nozzle portion provided in the center portion for performing diffuse combustion, an annular pilot premixing nozzle for coaxially surrounding the outer periphery of the pilot nozzle portion for performing premixed combustion, and the above annular shape By equipping a plurality of circular main swirler built-in type main nozzles arranged at equal intervals along the outer circumference of the pilot premixing nozzle and performing premixed combustion, respectively, air and fuel gas in the main nozzle are INDUSTRIAL APPLICABILITY The present invention is extremely useful industrially because it provides a gas turbine combustor that homogenizes radial mixing and reduces diffusion combustion in the pilot combustion chamber to improve NOx reduction.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a combustor showing an embodiment of the present invention.

FIG. 2 is an enlarged view showing the pilot nozzle of FIG.

FIG. 3 is a diagram showing fuel distribution between the pilot nozzles and the main nozzles in FIG. 1 in comparison with Conventional Example 1 and Conventional Example 2 shown in FIGS.

FIG. 4 is an explanatory diagram showing layered combustion in the combustion chamber of FIG. 1.

FIG. 5 is a vertical sectional view showing a first conventional example of a combustor of a gas turbine.

FIG. 6 is a vertical cross-sectional view showing a second conventional example of a gas turbine combustor.

[Explanation of symbols]

 1 pilot combustor 2 pilot fuel nozzle 3 main premixing nozzle 4 main fuel nozzle 5 combustor inner cylinder 6 pilot premixing nozzle 7 pilot swirler 8 main swirler 9 pilot nozzle 10 diffusion pilot nozzle 11 premixing pilot nozzle 17 partition plate

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Watao Sato 2-1-1 Niihama, Arai-cho, Takasago, Hyogo Prefecture Mitsubishi Heavy Industries Ltd. Takasago Research Center

Claims (1)

[Claims] 1. A pilot nozzle portion provided in a central portion for performing diffuse combustion, an annular pilot premix nozzle for coaxially surrounding the outer periphery of the pilot nozzle portion for premix combustion, and an annular pilot premix nozzle. A gas turbine combustor comprising: a plurality of circular main swirler built-in main nozzles, which are arranged at equal intervals along the outer periphery and each perform premixed combustion.