JPH08261464A - Turbulence-mixed fuel injection valve - Google Patents

Abstract

PURPOSE: To mix fuel and air evenly and prevent backfire and self-ignition. CONSTITUTION: Around the periphery of a fuel injection nozzle 1, by which fuel and air are mixed and injected, a shroud 4 is provided coaxially and with a clearance between the two. In this clearance a plurality of vanes 15 are disposed, which vanes cause vane-end eddies in a flow of air passed through the clearance. Into this clearance a flow of secondary air is supplied from the upstream side of the vanes 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection valve for low NOx (nitrogen oxide) combustion used in a gas turbine or a jet engine, and more particularly to a turbulent mixed fuel injection for preventing flashback and self-ignition. Regarding the valve.

[0002]

2. Description of the Related Art In a gas turbine or jet engine combustion apparatus, a premixing pipe is arranged between a combustor and a fuel injection nozzle to promote evaporation of fuel supplied to the combustor and mixing with air. Lean combustion is possible, and NOx emissions can be significantly reduced.

FIG. 6 shows a fuel injection valve for a gas turbine which achieves such low NOx combustion. In the figure, the fuel injection nozzle 1 has a double structure having a primary air supply part 2 on the center side and a fuel supply part 3 around it. A shroud 4 is coaxially formed with a gap on the outer periphery of the fuel injection nozzle 1.
Is provided, and this gap constitutes the secondary air supply unit 5. A swirler 6 is provided in this gap to make the secondary air a swirl flow. The shroud 4 has a tapered tip and is connected to the premixing pipe 7 to promote evaporation of fuel and mixing with air in the premixing pipe 7.

[0004]

FIG. 7 is a diagram for explaining the operation of the above-mentioned fuel injection valve. The air supplied from the primary air supply unit 2 and the fuel injected from the fuel supply unit 3 are mixed, and the air supplied from the secondary air supply unit 5 is further mixed therewith. This causes the fuel to mix with the air, but not necessarily homogeneously. Curve A shows the concentration distribution in one cross section of the premixing tube 7. The concentration is low on both sides and the center, but the concentration between both sides and the center is high. When the fuel concentration distribution becomes non-uniform as described above, there is a problem that the NOx emission amount increases.

To promote the mixing and combustion of fuel and air,
Although the swirler 6 is used, the swirling flow generated thereby causes the mixed gas to have a low flow velocity on the axial center of the premixing pipe 7. Further, the flow velocity is also slow near the pipe wall of the premixing pipe 7. In addition, there is a risk of flashback or self-ignition in the slow flow area. Flashback and self-ignition are more likely to occur as the combustor inlet pressure and inlet temperature are higher, which is a particular problem in the case of an aircraft jet engine that meets these conditions.

The present invention has been made in view of the above problems, and an object thereof is to uniformly mix fuel and air.
Furthermore, it aims to prevent flashback and self-ignition.

[0007]

In order to achieve the above object, in the invention of claim 1, a nozzle for mixing and injecting fuel and air and a nozzle are provided coaxially with an outer circumference of the nozzle with a gap. And a plurality of blades having a blade length of a predetermined length in a gap between the shroud and the outer circumference of the nozzle and arranged so as to intersect with an air flow flowing into the gap.

According to the second aspect of the invention, a fuel supply device for injecting fuel from the upstream side of the blade is provided in the gap.

According to a third aspect of the invention, a plurality of stages are provided in the blade in the flow direction of the inflowing air.

According to the fourth aspect of the present invention, the blades are arranged along the tapered shape in the gap between the tapered portion of the nozzle and the shroud so that the air flows along the tapered portion.

[0011]

According to the first aspect of the invention, the fuel and the air are injected from the nozzle while being mixed, but the air that has become a turbulent flow due to the tip vortex is mixed from around this, and the fuel and the air are uniformly mixed. The blade provided in the gap between the shroud and the outer circumference of the nozzle generates a blade tip vortex from the blade tip with respect to the air flow, makes the air flow turbulent, promotes mixing of fuel and air, and mixes uniformly.
The swirling flow used conventionally slows down the flow in the center of the premixing tube 7 and causes flashback and self-ignition, but the tip vortex forms a straight flow as a whole, and locally A small vortex flow promotes mixing with the fuel, so a uniform concentration distribution of the fuel can be obtained, and there is no part where the flow velocity slows or a part where backflow occurs, so uniform concentration and prevention of flashback and self-ignition A mixed gas is obtained. If the air flow rate is increased relative to the fuel flow rate, a low-concentration mixed flow is obtained, and low NOx combustion is achieved.

According to the second aspect of the present invention, the fuel is injected from the gap between the shroud and the outer circumference of the nozzle, so that more uniform mixing is achieved. This immediately mixes the injected fuel with the vortex at the tip of the blade, and becomes a turbulent vortex of the mixed flow, and this turbulent vortex agitates the mixed flow of the fuel and air injected from the nozzle, so that the fuel and air are uniformly A good mixture is obtained.

According to the third aspect of the invention, since the blades are provided in a plurality of stages in the air flow direction, the amount of blade tip vortices is increased, so that uniform mixing of fuel and air is further promoted.

According to the fourth aspect of the invention, since the blades are arranged so that the air flows along the tapered portion at the tip of the nozzle, the blades not only have a uniform mixing of fuel and air due to the generation of blade tip vortices, but also have a rectifying function. To do.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a vertical sectional view of the first embodiment, and FIG.
2 is a sectional view taken along line XX of FIG. The fuel injection nozzle 1 is cylindrical and has a tapered portion 16 at its tip to blow fuel into air to facilitate mixing, and a cylindrical primary air supply portion 2 is provided at the center of the primary air supply portion 2. Air supply port 1
Primary air is supplied from 1. Further, a fuel pipe connecting portion 12 is provided at the rear portion, and a fuel pipe (not shown) is connected to supply fuel. A fuel supply unit 3 is provided in the fuel injection nozzle 1 so as to surround the primary air supply unit 2 in communication with the fuel pipe connection unit 12, and fuel is injected from the surroundings to the air discharged from the primary air supply unit 2 to mix the air. It is supposed to do. A part of the fuel supply unit 3 is branched to form the secondary fuel supply unit 13, and the fuel is injected into the shroud 4 described later from a large number of openings provided on the outer periphery of the fuel injection nozzle 1.

A cylindrical shroud 4 is provided coaxially with the fuel injection nozzle 1 and having a gap with the nozzle 1. The tip of the shroud 4 is tapered to match the tip of the nozzle 1 and is connected to the premixing pipe 7. This gap constitutes the secondary air supply unit 5. A strut 14 is provided in the gap in the vicinity of the opening of the secondary fuel supply unit 13 and on the downstream side, and both ends of the strut 14 are fixed to the outer circumference of the nozzle 1 and the inner circumference of the shroud 4. The struts 14 are evenly provided along the outer circumference of the nozzle 1. Although FIG. 1 shows a case of eight, the number is not limited to this, and the number is appropriate according to the application. A wing 15 having a predetermined length is attached to each strut 14. The struts 14 are arranged such that the lengthwise direction thereof is the radial direction of the shroud 4, and the blades 15 are attached to the struts 4 such that the lengthwise directions of the blades 15 are orthogonal to each other. As a result, the air flowing into the secondary air supply unit 5 becomes turbulent due to the vortices generated from the blade tips. The blade length is such that adjacent blade tips do not come into contact with each other and do not hinder the generation of blade tip vortices. Further, by uniformly disposing the blades 15 in the gap, uniform blade tip vortices can be obtained.

Next, the operation will be described. Air compressed by a compressor (not shown) is supplied. Air supply port 1
The air entering 1 enters the primary air supply unit 2 and directly enters the secondary air supply unit 5. The fuel supplied from the fuel pipe connection portion 12 is supplied to the fuel supply portion 3 and a part of the fuel is injected from the tip and mixed with the primary air from the primary air supply portion 2 to mix with the premixing pipe 7.
Is injected into. Further, fuel is also injected from the secondary fuel supply unit 13 branched from the fuel supply unit 3, and the secondary air supply unit 5
Of the secondary air, passes through the blade 15, is uniformly mixed by the generated blade tip vortex, and enters the premixing pipe 7. In the premixing pipe 7, the mixed gas of the primary air and the fuel is mixed so that the mixed gas of the secondary air and the fuel mixed by the blade tip vortex is wrapped from the outside, and is uniformly mixed by the blade tip vortex. . Since a swirler is not used as in the conventional case, a swirling flow is not generated, a region where the flow velocity is slow or a backflow region is not generated, and the flow is almost straight. Therefore, it is possible to prevent the occurrence of flashback and self-ignition. Further, since the fuel is evenly distributed, a high concentration part is not locally generated, and low NOx combustion becomes possible. Since flashback and self-ignition are unlikely to occur in this way, it is suitable for use in a gas turbine for aircraft, which has high combustor inlet pressure and inlet temperature.

Next, a second embodiment will be described. FIG. 3 shows a longitudinal section of the second embodiment, and FIG. 4 is a view taken along the line YY of FIG. The difference between this embodiment and the first embodiment is that the blade 15 has two stages and is provided in the tapered portion 16 of the fuel injection nozzle 1, and the tapered portion 17 of the shroud 4 is placed downstream of the blade 15. . By forming the blades 15 in two stages in the air flow direction, the amount of blade tip vortices generated is increased, and the mixing of fuel and air is further homogenized. In addition, by forming the blades 15 in two stages, the secondary air flow does not separate from the blades 15 and the tapered portion 16 of the nozzle 1
Flow into. If the blade 15 has only one stage, separation is likely to occur. FIG.
In the above, the blades 15 are straight in the length direction, but by making them arcuate, a better rectifying effect and a stronger blade tip vortex can be obtained. In this embodiment, as in the first embodiment, the fuel concentration is uniform, flashback and self-ignition can be prevented, and low NOx combustion can be achieved.

In order to burn low NOx, it is necessary to lower the flame temperature, so that the fuel concentration is made thin and uniform. Further, it is necessary to burn the fuel in a vaporized state. Therefore, the premixing pipe 7 premixes the fuel and air and prevaporizes the fuel. If combustion occurs due to flashback or self-ignition without sufficient mixing and evaporation, NOx emissions may increase and the fuel injection valve may burn out. Therefore, it is necessary to prevent flashback and self-ignition. is there. Therefore, in the present invention, a swirling flow is not generated, a small vortex is uniformly generated by the blade tip vortex, and a linearly mixed flow that is uniformly mixed is generated. However, at a dilute concentration, combustion stability is poor. On the other hand, the method of using the swirling flow without arranging the premixing pipe is not preferable in that the NOx emission amount is large, but is excellent in performing stable combustion. Therefore, the fuel injection valve of the present invention is effective when used together with a fuel injection valve equipped with a swirler.

FIG. 5 is a diagram showing an example of use of the fuel injection valve of the present invention. The combustor 20 has a fuel injection valve 2 having a swirler.
1 and the fuel injection valve 22 of the present invention are provided so as to surround the same, and the fuel and the air from the compressor are mixed and burned, and the combustion gas is supplied to the turbine. When the load is low, combustion is performed only by the fuel injection valve 21 with a swirler, and when the load increases, the fuel injection valve 22 of the present invention is also used for combustion. As a result, stable combustion is always performed by the mixed gas from the swirler-equipped fuel injection valve 21, and the combustion gas also allows the mixed gas from the fuel injection valve 22 of the present invention to continue stable combustion. In this way, by utilizing the features of both the injection valves 21 and 22, low NOx combustion can be stably performed as a whole.

In the above embodiment, the secondary fuel supply unit 13 is provided and the fuel is also injected into the secondary air supply unit 5. However, this fuel injection is not always necessary, and the fuel may be injected only into the primary air. Good. Further, although the blades 15 are arranged orthogonally to the radial direction of the shroud 4 as shown in the sectional view of FIG. Further, although the blade is provided in the secondary flow path of air, it may be provided in the primary flow path.

[0022]

As is apparent from the above description, the present invention promotes mixing of fuel and air by providing a plurality of blades of a constant length in the air flow and generating blade tip vortices.
A homogeneous mixture is obtained, which allows low NOx combustion to be achieved. The flow generated by the blade tip vortex locally generates turbulence to promote mixing, but the overall flow is a straight flow, so the flow velocity becomes slow on the axis of the premixing tube like swirling flow, Since backflow does not occur, flashback and self-ignition can be prevented. As a result, the inlet pressure and inlet temperature of the combustor are high, and it can also be used in aircraft gas turbines that are prone to backfire and autoignition.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a first embodiment.

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

FIG. 3 is a vertical sectional view of a second embodiment.

FIG. 4 is a view as seen in the direction of arrows YY in FIG.

FIG. 5 is a diagram showing a usage example of the present invention.

FIG. 6 is a diagram showing a configuration of a conventional fuel injection valve.

FIG. 7 is a diagram showing a fuel concentration distribution of a conventional fuel injection valve.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fuel injection nozzle (nozzle) 2 Primary air supply part 3 Fuel supply part 4 Shroud 5 Secondary air supply part (air supply means) 6 Swirler 7 Premixing pipe 11 Air supply port 12 Fuel pipe connection part 13 Secondary fuel supply Part (fuel supply device) 14 strut 15 blade 16 tapered portion of nozzle 17 tapered portion of shroud 20 combustor 21 fuel injection valve with swirler 22 fuel injection valve of the present invention

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akihito Saito 4-21-1, Honmachi, Tanashi City, Tokyo No. 1 Hikari Building Ishikawajima Jet Service Co., Ltd.

Claims (4)

[Claims] 1. A nozzle for mixing and injecting fuel and air, a shroud having a gap with the outer circumference of the nozzle and provided coaxially, and a predetermined length in the gap between the shroud and the outer circumference of the nozzle. A turbulent mixed fuel injection valve having a plurality of blades each having a blade length of 10 mm and arranged so as to intersect an air flow flowing into the gap. 2. The turbulent mixed fuel injection valve according to claim 1, wherein a fuel supply device for injecting fuel from the upstream side of the blade is provided in the gap. 3. The turbulent flow mixed fuel injection valve according to claim 1 or 2, wherein a plurality of stages are provided in a flow direction of air flowing into the blade. 4. The blades are arranged along the tapered shape in the gap between the tapered portion at the tip of the nozzle and the shroud so that the flow of air flows along the tapered portion. 4. The turbulent mixed fuel injection valve according to any one of 3 above.