JPH09170716A - Fuel premixing device and gas turbine combustion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel premixing device, small in size, mixing fuel and air sufficiently and having no possibility of backfire or spontaneous ignition. SOLUTION: This device is constituted so as to be provided with a mixing flow passage and a fuel nozzle 3b, arranged in the mixing flow passage, while fuel is injected into flowing air, flowing through the mixing flow passage, from the fuel nozzle 3b to mix fuel into the air. A choking plate 8, choking air stream, is provided near the entrance of the mixing flow passage and at the upstream side of the fuel nozzle while a turbulent flow plate 9, generating turbulent flow in the mixture of air and fuel, is provided at the downstream side of the fuel nozzle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel premixing device, and more particularly to a fuel premixing device suitable for application to a gas turbine combustion device.

[0002]

2. Description of the Related Art As shown in FIG. 16, the main part of a conventional gas turbine combustion apparatus has adopted a two-stage combustion method in order to meet the demand for NOx reduction. In general, premixed combustion is performed at the rated output combustion. The premixed combustion is to burn a mixture of air and fuel mixed in advance, and can prevent the generation of a local high temperature region and reduce NOx.

The combustion apparatus mainly comprises a main combustion chamber R1, an auxiliary combustion chamber R2, a fuel nozzle (3a, 3b, 3c) and a premixer 4, and a gas turbine blade 2 is arranged downstream of the main combustion chamber R1. The compressor 1 is arranged on the upstream side. In this case, the second-stage combustion is premixed combustion, and the air and fuel are mixed in the premixer 4 to form a premixed gas, which is supplied into the main combustion chamber R1 and stored. The flame is held by the flame unit 5 and burns.

In the premixed combustion, it is effective to reduce the NOx by mixing the fuel and the air as uniformly as possible and burning the mixture in a lean premixed air. For this reason, generally, a system has been adopted in which a swirler is provided in the premixer, and after swirling the air, the fuel is injected from the fuel nozzle to promote the mixing of the fuel and the air.

Examples of the fuel premixing device of this type include JP-A-4-283316 and JP-A-6-2848.

[0006]

In the premixing device thus constructed, the air is swirled by the swirler to form a forced vortex, and the shear flow of the air causes the fuel and the air injected from the fuel nozzle to be injected. Mixing is promoted. However, even such a premixing device has the following problems.

That is, since all the air flowing in the premixer is swirled, the axial flow velocity component tends to be large at the outer peripheral portion and small at the central portion of the swirling, and a backflow may occur depending on the state. is there. If the premixed gas is supplied to the combustion chamber while leaving the non-uniform flow velocity distribution, a flashback may occur in the premixer from the low flow velocity part or the backflow part.

For this reason, in order to make the flow velocity distribution uniform in order to prevent flashback, the premixer must be lengthened, and the premixing device cannot be downsized. In addition, if the pressure ratio is increased to increase efficiency and the air temperature inside the combustor rises, the length of time of the premixer increases the residence time of the combustible premixed gas, increasing the possibility of spontaneous ignition. .

The present invention has been made in view of the above, and an object of the present invention is to shorten the distance, that is, to reduce the size, to sufficiently mix the fuel and the air, and to prevent the risk of flashback or spontaneous ignition. It is to provide a fuel premixing device of this kind.

[0010]

Means for Solving the Problems That is, the present invention comprises a mixing flow passage and a fuel nozzle arranged in the mixing flow passage, and from the fuel nozzle to the circulating air flowing in the mixing flow passage. In a fuel premixing device for injecting fuel to mix air and fuel, a separating means for separating an air flow is provided near an inlet of the mixing channel and upstream of the fuel nozzle, and the fuel is A turbulent flow generating means for generating a turbulent flow in a mixture of air and fuel is provided downstream of the nozzle to achieve the initial purpose.

Further, the mixing channel and a fuel nozzle arranged in the mixing channel are provided, and the fuel is injected from the fuel nozzle into the circulating air flowing in the mixing channel to mix the air and the fuel. In the fuel premixing device designed to
A turbulent flow plate is provided near the inlet of the mixing channel and upstream of the fuel nozzle, and a turbulent flow plate is provided downstream of the fuel nozzle to generate a turbulent flow in a mixture of air and fuel. Is provided.

That is, in the fuel premixing device formed as described above, the air flowing into the premixer causes local separation downstream of the throttle structure provided near the premixer inlet. A strong turbulence occurs near the boundary between the main stream and the separation region, and the fuel is injected into this strong turbulence, so that the strong turbulence of the air flow promotes the mixing of the fuel and the air. Therefore, the fuel and the air can be sufficiently mixed in a short distance, that is, in a small size, and the flashback and the spontaneous ignition can be suppressed. Furthermore, since the generation of a local high temperature region is prevented, it is possible to reduce NOx.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on illustrated embodiments. FIG. 1 shows the premixer 4 assembled in the combustor liner 6. The premixer 4 is formed in an annular shape (see FIG. 2) and is partitioned by a partition plate 7 into a large number of flow paths in the circumferential direction. A fuel nozzle 3b is projected at approximately the center of each flow path.
A throttle plate 8 is attached to the outer and inner circumferences near the inlet, and a triangular turbulent flow plate 9 having an angle of attack with the main flow direction of the air A is provided on the downstream side of the fuel nozzle 3b. .

The turbulent flow plate 9 projects from the partition plate 7 into the flow path as shown in FIG. 3, and is installed so that the projecting amount increases from the upstream side to the downstream side. . The flame stabilizer 5 is provided on the downstream side of the turbulent flow plate 9, that is, on the outlet side.
Is installed.

The mixing of fuel and air in the premixer thus formed is performed as follows. That is, the air A flowing into the premixer 4 is contracted by the diaphragm plate 8 and
Peeling S occurs downstream of Near the boundary between the mainstream A and the separation area S, the velocity gradient becomes large, so that strong turbulence occurs.
The fuel F flows from the fuel nozzle 3b downstream of the throttle plate 8 into the air flow A.
Is injected perpendicularly to the air flow A, but strong turbulence is generated in the air flow A.
The mixing with is promoted.

Further, since the triangular turbulent flow plate 9 is provided on the downstream side of the fuel nozzle 3b, the fuel F
And the air A further mix, that is, since the turbulent flow plate 9 has an angle of attack with respect to the main flow direction of the air A, the downstream separation S is three-dimensional, and the air flow A is the main flow direction as shown in FIG. It will flow while turning around. Therefore, the strong turbulence extends over a large area in the premixer.

As described above, since there is strong turbulence in a wide region of the air-fuel mixture on the post-injection side, the fuel F injected from the fuel nozzle 3b into the air A downstream of the throttle plate 8 is further mixed with air. It is possible to obtain a uniform premixed gas AF that is convenient for advancing and reducing NOx. Pre-mixture AF in which fuel F and air A are well mixed
Is flame-held by the flame stabilizer 5 provided at the outlet, and stable premixed combustion is performed.

In this case, the turbulent flow plate 9 imparts independent swirl to the mixed air flow depending on the angle of attack. However, as shown in FIG. 3, the swirl flow direction is the same at the boundary where the swirl contacts. It is preferable to promote the mixing of the fuel F and the air A. Also, regarding the angle of attack of the turbulent flow plate 9, 10 to 30 ° seems to be preferable in the result of the experiment.

Further, with such a structure, sufficient mixing of the fuel F and the air A and a uniform flow velocity distribution can be obtained in a short distance, so that the residence time of the combustible premixed gas AF in the premixer 4 is increased. Can be shortened, and the risk of spontaneous combustion is reduced.

In the above description, the fuel F is ejected from the fuel nozzle 3b perpendicularly to the air flow A. However, as shown in FIG. 4, the fuel F is parallel to the air flow A. The fuel F may be injected downstream, or the fuel F may be injected upstream with respect to the air flow A. Also,
The shape of the premixer 4 is not limited to the annular shape shown in FIGS. 1 and 2 divided by a large number of partition plates 7, and the same phenomenon may occur in the case of a cylindrical shape as shown in FIGS. Occurs.

In FIG. 7, the diaphragm plate 8 is attached to the outer circumference and the inner circumference in the vicinity of the inlet of the premixer 4 and to the partition plate 7 side. In this way, the air A flowing into the premixer 4 is contracted not only in the radial direction but also in the circumferential direction, so that the boundary between the main flow A and the separation region S expands and the region of strong turbulence expands. Therefore, the mixing of the fuel F and the air A is further promoted, and the homogeneity of the premixed air AF is improved.

FIG. 8 shows the diaphragm plate 8 having a circular flow path shape in contrast to FIG. 7 in which the flow path shape of the diaphragm plate 8 is a substantially quadrangular shape, but substantially the same actions and effects can be obtained.

In FIG. 9, four turbulent flow plates 9 having an attack angle with respect to the main flow direction of the air A are provided in the vicinity of the inlet of the premixer 4 with partition plates 7.
It is installed from the upstream side to the downstream side so that the protruding amount increases from the upstream side to the downstream side. In addition, FIG. 10 shows the S-S arrow view.

Since the turbulent flow plate 9 has an attack angle with respect to the main flow direction of the air A as described above, the downstream separation S is three-dimensional, and the air flow A is centered in the main flow direction as shown in FIG. It will flow while turning as an axis. Therefore, the strong turbulence extends over a wider area in the premixer than in the above-described embodiment. The fuel F is injected into the air A from the fuel nozzle 3b downstream of the turbulent flow plate 9. However, the air flow A has a strong turbulence in a wide area, so that the fuel F and the air A are further increased than in the embodiments described above. As a result, the uniform premixed gas AF, which is convenient for reducing NOx, can be easily obtained.

Further, although the turbulent flow plate is formed in a triangular shape in this embodiment, it is needless to say that it may be a quadrangular plate having an angle of attack. Also, the number of plates need not necessarily be four.

FIG. 11 shows an embodiment in which a round bar 10 perpendicular to the air flow A is installed near the inlet of the premixer 4. 12 is a view taken in the direction of arrows UU in FIG. 11, and FIG. 13 is a sectional view taken along line VV in FIG.

As shown in FIG. 13, at least the round bar 10 is installed on the upstream side corresponding to each ejection hole 11 of the fuel nozzle 3b. When a round bar is installed in the air flow A, separation S occurs on the downstream side, and Karman vortices are emitted. Near the boundary between the mainstream A and the separation area S, the velocity gradient becomes large, so that strong turbulence occurs.

The fuel F is supplied downstream of the round rod 10 to the fuel nozzle 3b.
Injected from. Then, since strong turbulence exists in this region, the mixing of the fuel F and the air A is promoted, and NO
x can be reduced. The peeling area S is a round bar 10.
Since it exists locally downstream of the premixer, it disappears in a short distance, and the flow velocity distribution is almost uniform, so it is possible to shorten the length of the premixer, and there is a risk of flashback and spontaneous ignition. It will disappear. In this case, of course, a square bar or a flat plate may be installed instead of the round bar 10.

FIG. 14 shows that the mesh 12 is provided in the vicinity of the inlet of the premixer 4, and since the separation area S is the smallest among those described so far, the effect of promoting the mixing of the fuel F and the air A is The least. On the contrary, a uniform flow velocity distribution is obtained at the shortest distance.

The throttle plates 8 are attached to the outer circumference and the inner circumference near the inlet of the premixer 4, and four turbulent flow plates 9 having an angle of attack with the main flow direction of the air A flow from the partition plate 7 downstream thereof. FIG. 15 shows that three sets of those projecting in the passage are installed in the flow direction, and the fuel F from the fuel nozzle 3b is injected between the first set and the second set.

Immediately after the separation S occurs in the downstream side of the throttle plate 8 and strong turbulence is generated, the turbulent flow plate 9 swirls around the main flow direction as a central axis to further strengthen the turbulence. Expand the area. Since the fuel F from the fuel nozzle 3b is injected into the air A downstream thereof,
The mixing of the fuel F and the air A will be greatly promoted. Further, the two sets of turbulence plates 9 on the downstream side also increase the strong turbulence, so that the mixing of the fuel F and the air A becomes extremely good. As a result, an extremely uniform premixture AF of the fuel F and the air A can be obtained, which may lead to a significant reduction of NOx.

As described above, before injecting the fuel F into the air A, it is necessary to install a plurality of means for generating the above-mentioned strong turbulence in the flow direction, and further to install them downstream of the fuel F injection. It is easily understood that the mixing of the fuel F and the air A becomes more uniform. This method is low NO
It is extremely effective for x conversion.

However, since the turbulence becomes stronger, a long distance is required to obtain a uniform flow velocity distribution, and it is undeniable that the possibility of flashback or spontaneous ignition is increased, and it is experimentally optimized depending on the model. Planned. By the way, when a plurality of sets of turbulent flow plates 9 having an angle of attack are installed in the flow direction, it is preferable that the direction of the swirling flow is the same in each set in order to improve the mixing of the fuel F and the air A. .

As described above, in this fuel premixing device, a structure for separating the air flow is provided near the inlet of the premixer, and the fuel is injected into the air from the fuel nozzle downstream thereof. In addition, since the turbulent flow plate is provided on the downstream side of the fuel nozzle, a large velocity gradient is generated near the boundary between the main stream of air and separation, and strong turbulence occurs, and fuel is injected into the air downstream. Therefore, the strong turbulence promotes the mixing of fuel and air, and further turbulence further promotes the mixing, so that a uniform premixed gas that is convenient for NOx reduction can be obtained.

Therefore, it is possible to sufficiently mix the fuel and the air in a short distance, to achieve a uniform flow velocity distribution, and to obtain a small premixer which is free from the risk of flashback or spontaneous ignition. It is possible to prevent a local high temperature region from being generated in combustion, and to reduce NOx.

[0036]

As explained above, according to the present invention, this kind of fuel premixing in which the fuel and air are sufficiently mixed in a short distance, that is, in a small size, and there is no fear of flashback or spontaneous combustion The device can be obtained.

[Brief description of the drawings]

FIG. 1 is a vertical sectional side view showing an embodiment of a fuel premixing device of the present invention.

FIG. 2 is a front view taken along the line II of FIG.

FIG. 3 is a sectional view taken along line AA of FIG. 1;

FIG. 4 is a vertical sectional side view showing another embodiment of the fuel premixing device of the present invention.

FIG. 5 is a vertical sectional side view showing still another embodiment of the fuel premixing device of the present invention.

FIG. 6 is a front view of FIG. 5;

FIG. 7 is a front view showing still another embodiment of the fuel premixing device of the present invention.

FIG. 8 is a front view showing still another embodiment of the fuel premixing device of the present invention.

FIG. 9 is a vertical sectional side view showing still another embodiment of the fuel premixing device of the present invention.

FIG. 10 is a view on arrow S-S in FIG. 9.

FIG. 11 is a vertical sectional side view showing still another embodiment of the fuel premixing device of the present invention.

FIG. 12 is a view taken in the direction of arrow UU in FIG.

13 is a cross-sectional view taken along the line VV of FIG.

FIG. 14 is a front view showing still another embodiment of the fuel premixing device of the present invention.

FIG. 15 is a vertical sectional side view showing still another embodiment of the fuel premixing device of the present invention.

FIG. 16 is a vertical cross-sectional side view showing the periphery of a conventional gas turbine combustion device.

[Explanation of symbols]

1 ... Compressor, 2 ... Gas turbine blade, 3a, 3b, 3c ...
Fuel nozzle, 4 ... Premixer, 5 ... Flame stabilizer, 6 ... Combustor liner, 7 ... Partition plate, 8 ... Throttling plate, 9 ... Turbulent flow plate, 10 ... Round bar, 11 ... Fuel injection hole, 12 ... mesh.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeyoshi Kobayashi 7-2-1, Omika-cho, Hitachi-shi, Ibaraki Hitachi, Ltd. Power & Electric Development Division

Claims (8)

[Claims] 1. A mixing flow path and a fuel nozzle arranged in the mixing flow path, wherein the fuel is injected into the circulating air flowing in the mixing flow path to mix the air and the fuel. In the fuel premixing device configured to perform, in the vicinity of the inlet of the mixing flow path and upstream of the fuel nozzle, a separating unit for separating an air flow is provided, and the air and the fuel are provided downstream of the fuel nozzle. A fuel premixing device comprising turbulent flow generation means for generating turbulent flow in the mixture. 2. A mixing flow path and a fuel nozzle arranged in the mixing flow path, wherein the fuel is injected from the fuel nozzle into the circulating air flowing in the mixing flow path to mix the air and the fuel. In the fuel premixing device configured to perform, in the vicinity of the inlet of the mixing flow path and on the upstream side of the fuel nozzle, a throttle plate that restricts an air flow is provided, and on the downstream side of the fuel nozzle, air and fuel A fuel premixing device comprising a turbulent flow plate for generating a turbulent flow in a mixture. 3. A mixing flow path and a fuel nozzle arranged in the mixing flow path, wherein the fuel is injected from the fuel nozzle into the circulating air flowing in the mixing flow path to mix the air and the fuel. In the fuel premixing device, a turbulent flow generator having an angle of attack with respect to the main flow direction of the air is provided in the mixing passage and upstream and downstream of the fuel nozzle. A fuel premixing device. 4. A mixing flow passage and a fuel nozzle arranged in the mixing flow passage, and the fuel is injected from the fuel nozzle into the circulating air flowing in the mixing flow passage to mix the air and the fuel. In the fuel premixing device, a mesh for restricting an air flow is provided in the vicinity of the inlet of the mixing channel and upstream of the fuel nozzle, and the air and fuel are mixed downstream of the fuel nozzle. A fuel premixing device comprising a turbulent flow plate for generating a turbulent flow. 5. A mixing flow path and a fuel nozzle arranged in the mixing flow path, wherein the fuel is injected into the circulating air flowing through the mixing flow path to mix the air and the fuel. In the fuel premixing device, a throttle plate for narrowing the air flow and a turbulent flow plate for generating a turbulent flow are provided in the vicinity of the inlet of the mixing channel and upstream of the fuel nozzle, and the fuel nozzle is provided. A fuel premixing device characterized in that a turbulent flow plate for generating a turbulent flow in a mixture of air and fuel is provided further downstream. 6. The fuel premixing device according to claim 2, wherein a plurality of turbulent flow plates arranged on the downstream side of the fuel nozzle are arranged in parallel in the air-fuel mixture flowing direction. 7. The turbulent flow plate has a triangular shape having an angle of attack with respect to the main air flow direction, and is formed such that the protrusion amount increases from the upstream side toward the downstream side. , 4 or 5 fuel premixing device. 8. A gas turbine combustion apparatus having a fuel premixing device for mixing a fuel and air to produce a premixed gas, comprising the fuel premixing device according to any one of claims 1 to 7. Characteristic gas turbine combustion device.