JP2000146183A - Gas turbine combustor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a combustion vibration of a gas turbine combustor by supplying a shielding gas between the air for a pilot combustion and premixing gas for a main combustion. SOLUTION: A main nozzle 20 for supplying fuel for a main combustion and a main air supply passage 22 are provided at a periphery of a pilot air supply unit 16. A main swirler 22a is arranged in the passage 22. The nozzle 20, the passage 22 and the swirler 22a constitute a main burner. An exhaust gas supply passage 18 is arranged as a shielding gas supply passage between a pilot air supply passage and the passage 22. Further, a sub-cone 26 is disposed concentrically with a pilot cone 24 at an outside of the cone 24 downstream of an exhaust gas supply passage 18. Thus, the shielding gas supplied to a periphery of the air for a pilot combustion suppresses a contact of a premixed gas with a pilot flame, and a burning speed of the premixed gas is decelerated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a gas turbine combustor.

[0002]

2. Description of the Related Art In a gas turbine combustor, a two-stage combustion type combustor has been conventionally used in some cases. That is,
Along with supplying fuel along the central axis of the combustor, supplying combustion air for the fuel from the periphery thereof, and performing pilot combustion as a diffusion flame (hereinafter, referred to as pilot flame) at the center of the combustor, By supplying a premixed gas for main combustion having a very high excess air rate around the pilot flame and bringing the high-temperature gas of the pilot flame into contact with the premixed gas, a premixed flame (hereinafter, referred to as a main flame) is obtained. ) Is performed.

Referring to FIG. 2 in more detail, a prior art gas turbine combustor 50 includes a pilot nozzle 54 having a pipe combustion fuel extending along a central axis O ′ in a liner 52. , And a pilot air supply path 56 is provided around the pilot nozzle 54. A pilot swirler 56 a for holding a flame is provided in the pilot air supply path 56. Furthermore,
Around the pilot air supply path 55, a main nozzle 60 for supplying main combustion fuel, a main air supply path 58, and a main swirler 58a are provided.

A pilot cone 62 is provided downstream of the pilot nozzle 54 and the pilot air supply passage 56, and the fuel supplied from the pilot nozzle 54 and the air supplied from the pilot air supply passage 56 are
Combustion occurs in a pilot combustion chamber 62a defined by the pilot cone 62, and a high-temperature pilot flame indicated by an arrow 66 is formed. The fuel supplied from the main nozzle 60 and the air supplied from the main air supply path 58 are
The mixed gas is mixed in the mixing chamber 64 downstream thereof, and a pre-mixed gas indicated by an arrow 68 is formed. The main flame 70 is formed when the premixed gas 68 comes into contact with the pilot flame 66.

[0005]

In the gas turbine combustor 50 according to the prior art, since the pilot flame 66 and the premixed gas 68 come into contact with each other in a relatively short time, the premixed gas 68 is easily ignited, and the main flame 70 is It burns at a relatively small distance in the axial direction or the main flow direction and tends to be a short flame. Thus, when combustion occurs over short distances, in other words, in small spaces, the spatial density of energy released by combustion, or
The cross-sectional combustion load factor of the combustor is increased, and combustion oscillation is likely to occur. The combustion vibration is a self-excited vibration generated by converting a part of the heat energy into the vibration energy. When the sectional load ratio of the combustor increases, the excitation force of the combustion vibration increases, and the combustion vibration easily occurs. As described above, the gas turbine combustor according to the related art has a problem that the combustion load factor is relatively large and combustion becomes unstable due to combustion vibration.

An object of the present invention is to solve such problems of the prior art, and an object of the present invention is to reduce combustion oscillation of a gas turbine combustor.

[0007]

According to the present invention, a pilot fuel for pilot combustion is supplied along a central axis of a gas turbine combustor, and pilot combustion air is supplied around the pilot fuel. A gas turbine combustor for supplying a main combustion premixed gas around a working air, wherein a shielding gas is supplied between the pilot combustion air and the main combustion premixed gas. Is the gist.

[0008]

The pilot fuel is burned by the pilot combustion air to form a pilot flame composed of a diffusion flame. As in the prior art, the main combustion premixture contacts the pilot flame and burns by premixed combustion. The shielding gas supplied around the pilot combustion air suppresses contact between the premixed gas and the pilot flame, and the combustion speed of the premixed gas is reduced. Therefore, the main flame, which is a premixed flame formed between the premixed gas and the pilot flame, becomes longer in the longitudinal direction of the combustor, and the combustion energy density is reduced.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A gas turbine combustor according to an embodiment of the present invention will be described below with reference to FIG. The gas turbine combustor 10 according to the present embodiment has a substantially cylindrical shape, and in the liner 12, along the central axis O of the combustor 10,
A pilot nozzle 14 is provided for supplying fuel for pit combustion. A pilot air supply path 16 is provided around the pilot nozzle 14, and a pilot swirler 16 a for holding a pilot flame is provided in the pilot air supply path 16. The pilot nozzle 14, the pilot air supply path 16, and the pilot swirler 16a constitute a pilot burner. Downstream of the pilot air supply passage 16, a pilot combustion chamber 24a
Is provided.

A main nozzle 20 and a main air supply passage 22 for supplying main combustion fuel are provided around the pilot air supply passage 16, and a main swirler 22 a is provided in the main air supply passage 22. Have been. The main nozzle 20, the main air supply passage 22, and the main swirler 22a constitute a main burner. An exhaust gas supply passage 18 is provided between the pilot air supply passage 16 and the main air supply passage 22 as a shielding gas supply passage. Further, downstream of the exhaust gas supply passage 18, a sub cone 26 is provided outside the pilot cone 24,
4 and are arranged concentrically.

The operation of this embodiment will be described below. The pilot combustion air from the pilot air supply passage 16 is
In the pilot combustion chamber 24a, the fuel flows so as to enclose the pilot fuel supplied from the pilot nozzle 14, and the pilot fuel is burned by the pilot combustion air to produce a pilot flame (arrow 3) composed of a diffusion flame.
0) is formed. The fuel supplied from the main nozzle 20 and the air supplied from the main air supply passage 22 are mixed in a downstream mixing chamber 28 to form a premixed air indicated by an arrow 28. When the premixed gas 28 comes into contact with the pilot flame 30, a main flame 34 as a premixed flame is formed.

Exhaust gas generated by combustion in the gas turbine combustor 10 is supplied to a gas turbine (not shown) provided downstream of the gas turbine combustor 10.
The gas turbine is driven. After driving the gas turbine, most of the exhaust gas is exhausted to the atmosphere, but part of the exhaust gas is again returned to the exhaust gas supply path 18 of the gas turbine combustor 10 by a recirculation system including an exhaust gas compressor (not shown). Recirculated to

Exhaust gas 36 from the exhaust gas supply passage 18 is supplied between the pilot flame 30 and the premixed gas 32 by an exhaust gas introduction portion 26a formed between the pilot cone 24 and the sub cone 26 as a shielding gas introduction portion. Is done. Due to the exhaust gas 36, the pilot flame 30 and the premixed air 32
Is suppressed, the combustion speed of the main flame 34 decreases, and the main flame 34 becomes longer in the axial direction of the combustor or in the mainstream direction. Therefore, the combustion energy density released by the main flame 34 or the cross-sectional combustion load of the combustor is reduced, the excitation force of the combustion vibration is reduced, and the combustion vibration is suppressed. Furthermore,
Due to the exhaust gas 36, the oxygen concentration in the main flame 34 decreases, and the flame temperature decreases. Because of this, NOx generated
The amount decreases.

In the above-described embodiment, the exhaust gas of the gas turbine is described as an example of the shielding gas. However, the present invention is not limited to this, and the exhaust gas from other devices may be used. Further, an inert gas, such as nitrogen, supplied from another facility may be used. In short, any gas that is inert to the combustion reaction that can prevent the air-fuel mixture from directly contacting the pilot flame and lengthen the premixed flame in the mainstream direction of the combustor may be used.

[0015]

According to the first aspect of the present invention, the shielding gas supplied around the pilot combustion air suppresses the contact between the premixed air and the pilot flame, and the combustion speed of the premixed air is reduced. I do. Therefore, the main flame formed between the premixed gas and the pilot flame becomes longer in the longitudinal direction of the combustor, the combustion energy density is reduced, and the combustion oscillation is suppressed.

According to the second aspect of the present invention, by using the exhaust gas as the shielding gas, the oxygen concentration of the premixed flame is reduced and the generation of NOx is suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a gas turbine combustor according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view of a gas turbine combustor according to the prior art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Gas turbine combustor 14 ... Pilot nozzle 16 ... Pilot air supply path 18 ... Exhaust gas supply path 20 ... Main nozzle 22 ... Main air supply path

Continued on the front page (72) Inventor Koichi Nishida 2-1-1, Shinhama, Arai-machi, Takasago-shi, Hyogo Prefecture Inside Takasago Works, Mitsubishi Heavy Industries, Ltd. (72) Inventor Mako Akamatsu 2-1-1, Niihama, Arai-machi, Takasago-shi, Hyogo Mitsubishi Heavy Industry Co., Ltd. Takasago Factory

Claims (2)

[Claims] 1. A pilot fuel for pilot combustion is supplied along a central axis of a gas turbine combustor, a pilot combustion air is supplied around the pilot fuel, and a main combustion air is supplied around the pilot combustion air. A gas turbine combustor for supplying a premixed gas, wherein a shielding gas is supplied between the pilot combustion air and the main combustion premixed gas. 2. The gas turbine combustor according to claim 1, wherein the shielding gas is a recirculated gas of exhaust gas burned by the gas turbine combustor.