JPH06101841A - Air-fuel premixing structure for gas turbine combustor - Google Patents

Abstract

PURPOSE:To provide an effective structure being a basic technology through which premixing of the air and fuel is carried out at the time when premixed combustion is executed to suppress the production of NOx by a gas turbine combustor. CONSTITUTION:In a premixing burner port 10 arranged in a single stage or a multistage, an annular pre-mixture passage 8 in each stage is divided into a plurality of sections by means of an air foil 9 and a partition plate. Through lengthening in a radial direction of a fuel nozzle simultaneously with acceleration and deceleration of pre-mixture air and fuel gas in a pre-mixture passage 8 by means of the air foil 9, a plurality of fuel gas injection nozzles 13, arranged to both sides of a fuel nozzle, are caused to change a pitch or a nozzle diameter so as to match with a local premixed air amount, and an ideal fuel-air premixing can be carried out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention provides a low N by premixed combustion.
The present invention relates to an air-fuel premixing structure of a gas turbine combustor for performing Ox combustion, particularly natural gas (LNG, LPG, etc.)
The present invention relates to an air-fuel premixing structure of a gas turbine combustor capable of significantly reducing NOx when a gaseous fuel such as the above is used.

[0002]

2. Description of the Related Art Among conventional low NOx combustors, a technique closest to the present invention will be described. For example, JP-A-61-2212
According to the contents disclosed in the publication No. 7, a two-stage combustion system is adopted, a first stage adopts a diffusion combustion system using a multi-nozzle, and a second stage adopts a pre-mixing combustion system using a multi-nozzle. is doing. As a whole, low temperature combustion is performed due to excess air to reduce NOx.

As is well known, a gas turbine requires a very wide range of combustion from ignition to rated load. Therefore, it is impossible to cover this wide range of combustion only by premixed combustion having a narrow combustion range. For this reason, there is no choice but to rely on a diffusion combustion system having a wide combustion width from ignition to a certain rotation speed or a certain load band. However, in the diffusion combustion method, a high temperature portion is likely to be generated locally, so the level of NOx generated as a result of combustion increases. Therefore, in order to reduce NOx, a premixed combustion method with excess air is used to achieve uniform and low temperature. Need to be burned. Therefore, at the time of ignition, it is started by diffusion combustion, and it is necessary to switch to sequential premixed combustion while supporting the diffusion combustion flame from the time when the fluctuation range of the air-fuel ratio, that is, the air ratio, approaches the premixed combustion range. Becomes By this operation,
It enables low NOx operation of the gas turbine.

On the other hand, in the case of the premixed combustion system, low NOx
Combustion is not always easy to achieve. It is difficult to obtain a complete premixed gas even if the fuel is subdivided and supplied to a simple premixing passage having a short mixing distance as shown in FIGS. There will be a concentration distribution in. In other words, the meaning of subdividing the fuel is to supply the fuel corresponding to the air locally flowing therethrough. Particularly, in the structure in which the fuel is supplied vertically and horizontally to the premixing passage and the air flow is reversed as in the prior art shown here, the air is locally dealt with in a three-dimensional and biased space. As a result, it becomes extremely difficult to supply fuel, and as a result, a portion having a high gas concentration is partially generated, the flame temperature becomes high in this portion, and NOx generation is accelerated.

Making the concentration distribution of the premixed gas uniform is an extremely important technique for achieving low NOx.

[0006]

The object of the present invention is to achieve a significantly lower NOx combustion, for which a very homogeneous premix is obtained and the premixing with air is enhanced. The temperature distribution of the flame is made uniform, and low temperature combustion is realized.
Air in a gas turbine combustor that can significantly reduce Ox-
It is intended to provide a fuel premixing structure.

[0007]

In order to achieve the above-mentioned object, the present invention provides a plurality of premix passages by providing an airfoil or a combination of a partition plate and an airfoil in an annular premix passage. In order to reduce the pre-mixing distance by reducing the hydraulic diameter by dividing into two parts, the fuel nozzle provided upstream is elongated in the height direction of the pre-mixing passage (nozzle cross section becomes a rectangular shape in the radial direction). , The fuel gas flow rate corresponding to the local air flow rate is supplied to homogenize the premixed air, and the premixed air and the fuel gas are improved by accelerating and decelerating the airfoil. . Therefore, even if the premix distance is the same, the air-fuel mixture in the premix passage can be dramatically improved.

[0008]

In order to improve the mixing of fuel gas and premixed air, (1) reduce the hydraulic diameter of the cross section of the premixing passage. (2) reduce the local premixing air flow rate in the premixing passage. Supply the fuel gas in proportion to each other. (3) A flow resistor is provided in the premixing passage through which the mixture of the injected fuel gas and the premixed air passes to give a predetermined pressure loss for promoting the mixing (mixing). It is a technical condition to satisfy the above three factors. In the present invention, a combination of an airfoil or a partition plate and an airfoil reduces the hydraulic diameter, lengthens the fuel nozzle in the height direction of the premixing passage, and adjusts the fuel gas in proportion to the local premixing air flow rate. Is supplied, and acceleration and deceleration are performed by an airfoil to give a predetermined pressure loss necessary for mixing to improve mixing.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. FIG. 1 is a sectional view showing a specific example of a gas turbine combustor according to the present invention. In this embodiment, an example of a single-stage premix burner is shown, but the present invention is not particularly limited, and two or more stages may be included in the present invention without any problem. Compressed air 1 pressurized by a gas turbine compressor (not shown) is supplied to an air chamber 3 after the pressure is restored by a diffuser 2. A part of the compressed air 1 is used to cool the combustor liner-4.
It is used as cooling air 5 and is supplied into the combustion chamber 14.

The other part of the compressed air 1 passes between the adjacent fuel nozzles 7 as the premixed combustion air 6, flows in the premix passage 8 and is supplied to the combustion chamber 14 from the premix burner port 10. Then, premixed combustion is performed.

On the other hand, the premixed fuel gas 11 enters the premixed fuel chamber 12, and is injected into the premix passage 8 from a plurality of fuel gas injection holes 13 provided on both sides of each of the plurality of fuel nozzles 7. Then, it joins with the premixed combustion air 6, diffuses and mixes with the airfoil 9, becomes homogeneous premixed fuel gas, is supplied to the premixing burner port 10, becomes premixed flame in the combustion chamber 14, and becomes a low mixture. NOx combustion is performed.

On the other hand, regarding the diffusion burner, a part of the compressed air enters the diffusion combustion air passage 23 as the diffusion combustion air 17, and is supplied from the diffusion burner swirler 18 into the combustion chamber 14 through the diffusion burner port 19. It becomes a diffusion flame. Further, the diffusion fuel gas 20 passes through the diffusion fuel gas passage 21 and is injected into the diffusion burner swirler 18 through the diffusion fuel gas injection port 22 and is supplied into the combustion chamber 14 through the diffusion burner port 19. Combustion chamber 14
The high-temperature gas burned in 1 flows in the transition piece 15 and is supplied to the turbine side as a high-temperature gas stream 16.

The premix structure of the present invention relates to the premix combustion air 6, the fuel nozzle 7, the premix passage 8, the airfoil 9 and the fuel gas injection port 13, and finally from the premix burner port 10. An extremely uniform premixed gas is supplied to the combustion chamber 14 to realize near-ideal premixed low NOx combustion.

FIG. 2 is a sectional view taken along line AA of FIG.
As shown in the drawing, 16 fuel nozzles 7 are shown in the space of the diffusion fuel gas passage 21 in the center and in the portion of the premix passage inlet 24. As can be seen from the drawing, the fuel nozzle 7 is inserted into the inlet portion of the premix passage 8 with its cross section being lengthened in the radial direction and being substantially the same as the radial height of the premix passage 8. The fuel gas jet 25 of the fuel nozzle 7 is jetted in the circumferential direction from a plurality of fuel gas jets 13 provided on both side surfaces of the fuel nozzle as shown in the drawing, and the fuel gas jet 2
It becomes like 5. A portion near the outer cylinder 27 is the combustion air passage portion 26, which is a passage for the compressed air 1.

As shown in FIG. 1, in the passage structure in which the flow direction of the premixed combustion air 6 is reversed, the flow velocity on the outer peripheral side of the flow increases due to the uneven flow. On the other hand, as is clear from FIG. 2, the passage cross-sectional area of the premixed air inlet portion is smaller toward the center. Therefore, although the imbalance of the premixed air amount tends to be considerably relaxed, the flow rate is not always uniformly distributed in the radial direction. Therefore, in order to correct this imbalance, it is necessary to distribute the fuel gas on the fuel side in proportion to the amount of air.

The present invention seeks to correct this imbalance in two ways. That is, the first method is to correct the imbalance of the drift by changing the pitch of the plurality of fuel gas injection holes 13 provided on both side surfaces of the fuel nozzle, as shown in FIG.
As shown in FIG. 7, the second method is to correct the unbalance of the drift by changing the nozzle diameters of the plurality of fuel gas nozzles 13 provided on both side surfaces of the fuel nozzle.

FIG. 3 shows a cross section taken along the line BB of FIG. 1, and in particular, an airfoil 9 provided in the premix passage 8.
It shows a detailed cross section of the portion. Premix passage 8
Is divided into a plurality of parts by the premix passage partition plate 28, and serves to reduce the hydraulic diameter and improve the mixing efficiency of the premix air and the fuel gas. An airfoil 9 is inserted into the divided premixing passage 8 to form a premixing passage narrow portion 29. The narrow portion 29 of the premix passage is effective in correcting the uneven flow of the premix air and is also effective in promoting the mixing of the premix air and the fuel gas in the deceleration portion of the airflow downstream of the airfoil. . That is, as shown in FIG. 4, which is a sectional development view of the CC in FIG. 1, the airfoil 9 is an enlarged premixing passage having a tapered rear portion and a diverging end in its tapered portion. The pressure difference across the airfoil 9 is a fluid pressure drop, but this pressure difference can be considered the energy required to improve mixing.

In the embodiment shown in FIGS. 3 and 4, the premixing passage partition plate 28 and the airfoil 9 are combined to divide the premixing passage 8 into a plurality of parts. The same effect can be obtained even if the premix partition plate 28 is omitted.

FIG. 4 is a sectional development view taken along the line CC of FIG. 1, in which the fuel nozzle 7, the airfoil 9, the premixing passage partition wall 28, the premixing passage narrow portion 29 and the fuel gas jet 2 are shown.
5 is a diagram illustrating the relationship with 5. The premixed combustion air 6 is divided into two for each premixing passage 8 by the fuel nozzle 7 provided at the inlet of the premixing passage 8.
It will be accelerated at 9 and then decelerated by the enlarged passage to promote mixing. Turbulent vortices generated in the wake of the airfoil 9 are attenuated while promoting mixing in the premix passage 8 and reach the premix burner port 10.

FIG. 5 is a D view of FIG. 1, showing the premixing burner port 10 and the diffusion bar from the inside of the combustion chamber 14.
This shows the opening 19. As can be seen from FIG. 5, the premixing burner port 10 has a swirl flow, and the diffusion burner port 19 also has a swirl flow. The swirling directions are the same, and a counter flow is induced on the axial center of the combustion chamber 14 generated by swirling to stabilize the flame.

As described above, the present invention relates to the mixing structure of the fuel gas supplied from the fuel nozzle 7 and the premixed combustion air 6, which is different from the case where the premix burner port 10 has multiple stages. Can be similarly applied. That is,
As shown in FIG. 8, even in the case of a two-stage premix type, the present invention can be applied to each stage.

[0022]

The first effect of the present invention is to provide a plurality of airfoils in the annular premix passage,
The premixed combustion air and fuel gas undergo an acceleration-deceleration process, and the hydraulic diameter can be reduced, resulting in extremely efficient mixing. A second effect of the present invention is to use a fuel nozzle that is long in the height direction (radial direction) of the annular premixing passage and distribute the fuel gas in the height direction to promote more effective mixing. That is. A third effect of the present invention is, in order to further promote the second effect, with respect to a plurality of fuel gas injection holes provided on both side surfaces of the fuel nozzle,
It is possible to obtain an extremely uniform premixed air by biasing the pitch of the nozzles and the diameter of the nozzles so as to match the local amount of premixed combustion air. A fourth effect of the present invention is that a more efficient mixing process can be obtained by combining the above first to third effects. A fifth effect of the present invention is that by making the premixing burner port multistage, low NOx combustion by premixing combustion can be achieved over a wide range of load changes of the gas turbine. As described above, the effects of the present invention are extremely effective for realizing low NOx combustion of the gas turbine.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a gas turbine combustor combining a premixed combustion and a diffusion combustion method according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG.

4 is a development view of a cross section taken along the line CC of FIG.

5 is a view on arrow D in FIG. 1. FIG.

FIG. 6 is a partial perspective view showing an example in which the pitch of fuel gas injection holes is changed.

FIG. 7 is a partial perspective view showing an example in which the injection port diameter of the fuel gas injection port is changed.

FIG. 8 is a cross-sectional view showing an example in which the premix burner has two stages.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Compressed air, 2 ... Diffuser, 3 ... Air chamber, 4 ... Combustor liner, 5 ... Liner-cooling air, 6 ... Premix combustion air, 7 ... Fuel nozzle, 8 ... Premix passage, 9 ... Air foil, 10 ... Premix burner port, 11 ... Premix fuel gas,
12 ... Premixed fuel chamber, 13 ... Fuel gas nozzle, 14 ... Combustion chamber, 15 ... Transition piece, 16 ... High temperature gas flow,
17 ... Diffusion combustion air, 18 ... Diffusion burner swirl, 19 ...
Diffusion burner port, 20 ... Diffusion fuel gas, 21 ... Diffusion fuel gas passage, 22 ... Diffusion fuel gas jet port, 23 ... Diffusion combustion air passageway, 24 ... Premixing passage inlet port, 25 ... Fuel gas jet stream,
26 ... Combustion air passage part, 27 ... Outer cylinder, 28 ... Premixing passage partition plate, 29 ... Premixing passage narrow part.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiko Kumada 3-1-1, Saiwaicho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi factory

Claims (6)

[Claims] 1. A gas turbine combustor for performing a low NOx combustion by premixing a part of combustion air supplied from a compressor as premixed air with a fuel, to provide a plurality of premixed passages in an annular shape. An airfoil is provided in the radial direction to divide the premixing passage into a plurality of parts by the airfoil, and a nozzle having a rectangular sectional shape extending in the radial direction is arranged at the inlet of each divided premixing passage and the tip of the nozzle is A plurality of fuel injection holes are provided on both sides of the long side portion, and the airfoil in each of the divided premixing passages promotes mixing of the fuel supplied from the nozzle and the premixed air supplied to the premixing passage to reduce the NOx. An air-fuel premixing structure for a gas turbine combustor, characterized in that combustion is performed. 2. In a gas turbine combustor for premixing a part of combustion air supplied from a compressor with fuel as premixed air to perform low NOx combustion, an annular premixing passage is radially formed. It is divided into a plurality of parts by extending partition plates, an airfoil extending in the radial direction is provided in each of the divided premixing passages, and a nozzle having a rectangular cross-sectional shape extending in the radial direction is arranged at the inlet of each of the divided premixing passages. A plurality of fuel injection holes are provided on both sides of the long side of the tip of the nozzle, and the fuel supplied from the nozzle and the premixed air supplied to the premixing passage are mixed by the airfoil of each divided premixing passage. An air-fuel premixing structure for a gas turbine combustor, which promotes low temperature NOx combustion. 3. A part of the premixing passage widens toward the end to form a premixing passage by forming the rear portion of the airfoil into a tapered shape,
An air-fuel premixing structure for a gas turbine combustor according to claim 1 or 2, wherein diffusion mixing of the premixed fuel and the premixed air is performed. 4. The fuel-air mixing ratio is made uniform by arranging a plurality of fuel injection holes provided on both sides of the long side of the fuel nozzle at unequal intervals so as to correspond to the locally mixed premixed air amount. The air-fuel premixing structure for a gas turbine combustor according to claim 1 or 2, wherein 5. The fuel-air mixing ratio is made uniform by changing the diameters of a plurality of fuel injection holes provided on both sides of the long side of the fuel nozzle so as to correspond to the locally mixed premixed air amount. The air-fuel premixing structure for a gas turbine combustor according to claim 1 or 2, wherein 6. The gas turbine combustor according to claim 1, wherein the annular premixing passages are provided in multiple stages in the radial direction, and the fuel supply nozzles are also provided in multiple stages. Air-fuel premix structure.