JPH07190367A - Fuel nozzle for gas combustion - Google Patents

Abstract

(57) [Abstract] [Purpose] As part of solving environmental problems, in order to realize combustion that reduces the concentration of nitrogen oxides (NOx) generated by combustion, it is determined by the extent to which the flame can be stabilized. To be done. The purpose of the present invention is to extend the stabilization of this flame to ultimately suppress the generation of NOx. [Structure] A flame holding ring (including a flame holding plate) is installed so as to be orthogonal to the air flow, and flame holding fuel is made to flow behind the flame holding ring to expand flame stability, and at the same time, the temperature of the flame holding ring. Is designed to be kept low. [Effect] According to the present invention, the following effects can be obtained. 1. Ensuring flame stability during low NOx combustion. 2. Complete prevention of combustion vibration. 3. Ensuring the reliability of combustion equipment through reliable combustion. 4. Prolonged service life of combustion equipment due to quiet combustion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion device for combusting a gas fuel, and more particularly to a fuel nozzle used in a gas combustion boiler, a gas turbine combustor, a gas combustion furnace, a gas combustion instrument or the like. In particular, the stable combustion area of the combustor is expanded to prevent combustion vibration that tends to occur during low NOx combustion,
It is used for a quiet and highly reliable gas combustor.

[0002]

2. Description of the Related Art With respect to a gas fuel nozzle, a technique closest to the present invention will be described. For example, in Japanese Patent Laid-Open No. 50-2221, as shown in FIGS. 8, 9, and 10,
The flame-holding fuel injected from the opening 44 (shown as 6 nozzles in the figure) is shown to be stably burned in the flame-holding plate 46 after being mixed with the air supplied from the openings 47 and 48. Has been done. As is well known, in the case where a gas fuel and air are premixed and then burned, the combustion range is determined by the mixing ratio with air, and further, there is a drawback that the combustion is narrow, and if premixing progresses, a flashback occurs. A phenomenon also occurs.

Referring to FIG. 8, a front view of the fuel nozzle is shown, and a main gas injection port 42 is circumferentially divided into 8 at the tip of the fuel nozzle 40, and a total of 16 dual gas nozzles are provided in the radial direction. Has been. Furthermore, on its outer periphery,
Eight air intakes A47 are provided. A flame holding ring 46 is provided on the outside thereof. FIG. 9 shows X- of FIG.
A cross section of X is shown, and a fuel nozzle 40 is provided at the tip of the fuel supply pipe 41. The fuel nozzle 40 has a main gas injection port 42 at its tip and a flame holding gas injection port 44 at its upstream side. Then, it is supplied to the mixing chamber 49 from the flame holding gas injection port 44.

On the other hand, the mixing cylinder is provided with an air intake A47 at the bottom, and an air intake B48 is also provided around the cylinder.
Is provided. That is, the flame holding gas and the air are mixed in the mixing chamber 49, and the flame holding ring 46 holds the flame. FIG. 10 is a cross-sectional view taken along line YY of FIG. 16, in which the fuel nozzle 40 provided outside the fuel supply pipe 41 is provided with six flame holding gas injection holes 44. An air inlet A47 provided at the bottom of the mixing cylinder 50 is provided. As can be seen from these structures, the flame holding gas is mixed in the mixing chamber 49, and then the flame holding ring 4 is mixed.
6 is trying to stabilize the flame.

As described above, in the prior art, after the flame holding gas and the air are mixed in advance, the flame is stabilized by the flame holding ring 46, so that the stable combustion width is narrow and sometimes the flashback occurs. There were drawbacks such as.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a gas burner having a wide margin by expanding a stable combustion width.

A second object of the present invention is to completely prevent combustion oscillation in a combustion state close to the limit, for example, in the case of low NOx combustion, and as a result, a large N
Achieving reduction of Ox (nitrogen oxide).

A third object of the present invention is to provide a gas burner which is highly reliable and has a long life without the risk of burnout or overheating.

[0009]

In the present invention, unlike the above-mentioned prior art, in order to expand the stable combustion width, the fuel itself is directly supplied to the flame holding ring while avoiding mixing with air in advance. is there. Further, in order to expand the stable width of combustion, flame holding rings are provided so as to be orthogonal to the air flow as much as possible, and reliable flame holding is ensured by the vortices that can flow in the subsequent flow. Furthermore, in order to prevent overheating of the flame holding ring, a thick fuel that is out of the flammability limit is flown to the back of the flame holding ring (the part where the flame exists), and only direct contact between the flame and the flame holding ring is possible. It has a structure to avoid. That is, the heat transfer amount to the flame holding ring is minimized.

[0010]

The operation according to the present invention is as follows.

(1) A flame holding ring is provided so as to be orthogonal to the air flow, and in addition to the gas fuel supplied from the main gas injection port, a flame holding fuel supplied from the flame holding gas injection port is provided and mixed with air. It is supplied to the back of the flame holding ring while avoiding this, and is supplied into the strong vortex that can be formed in the wake of the flame holding ring to expand the stable combustion width.

(2) Since the flame-holding fuel of (1) is supplied on the back surface of the flame-holding ring outside the flammability limit, the flame and the flame-holding ring generated in the wake of the flame-holding ring are separated from each other. By avoiding direct contact as much as possible, it is possible to prevent the flame ring from overheating.

(3) Since the area ratio between the main gas injection port and the flame holding gas injection port is always constant, the ratio is kept constant corresponding to the change in the total gas fuel flow rate, so that the load changes. It is possible to greatly improve the proof stress.

(4) The strong vortices formed in the wake of the flame holding ring cause a rapid diffusion of the flame holding fuel and air, so that the amount of NOx generated there can be suppressed to a minimum. Especially, the faster the air velocity is, the more remarkable this effect is.

(5) The combustion gas generated in the flame holding ring (O ₂ partial pressure is lowered) is mixed with the main fuel gas supplied in the downstream flow, and a further kind of exhaust gas mixing effect results in further improvement. Low NOx can be achieved.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. FIG. 1 is a view showing a cross section of a fuel nozzle and a combustion chamber according to the present invention. The gas fuel 1 is supplied from the left end as shown by the arrow, and most of it is supplied from the plurality of main injection ports 2 to the combustion chamber 25.
Is injected and supplied at a certain angle. A very small amount of gas fuel is supplied to the flame holding fuel chamber 4 through the flame holding fuel supply hole 3, passes through the first stage throttle 5, the flame holding fuel passage 17, and the second stage throttle 7, and the flame holding fuel distribution unit 10 is provided. The flame holding fuel is changed in direction to flow on the back surface of the flame holding ring 11 and is supplied to the periphery thereof. On the other hand, the air flow 12 passes through the main combustion air holes 13, is partially blocked by the flame holding ring 11, and then is supplied into the combustion chamber 25 constituted by the combustion cylinder 14 and burns. As is well known, after the air flow 12 enters through the main combustion air holes 13,
When a part of the flow is blocked by the flame holding ring 11,
The flow is separated from the tip a portion of the flame holding ring 11, and a vortex is generated in the subsequent flow. The strength of this vortex is determined by the flow velocity of the air flow 12, and the higher the flow velocity, the stronger the vortex. Fuel can be supplied to the vortex portion from the back surface of the flame holding ring 11 to form a stable flame. Guide ring 9
Plays an important role in changing the direction of the flame holding fuel and making the fuel flow along the back surface of the flame holding ring 11. The guide ring 9 also plays an important role in preventing the temperature rise of the flame holding ring 11. It is well known that the flame formed on the back surface of the flame holding ring has a considerably high heat transfer coefficient in the very vicinity of the tip a.
Since the rich fuel gas outside the flammability limit flows on the back surface of the flame holding ring, direct contact with the flame is prevented and the amount of heat transfer is reduced, so that the temperature of the flame holding ring can be kept low. Furthermore, the guide ring 9 has an effect of blocking radiant heat from the flame generated in the combustion chamber 25, and the temperature of the flame holding ring 11 can be suppressed to a low level. On the other hand, the heat transfer amount of the guide ring 9 is not so large as that of the flame holding ring 11, and is mainly the radiant heat from the flame formed in the combustion chamber 25 and is cooled by the gas fuel 1 from inside and the fuel flowing through the main injection port 2. , Can be kept at a sufficiently low temperature. Flowing the back side of the flame holding ring without premixing the flame holding fuel with air as in the present invention not only expands the stable combustion range, but also thermally blocks the flame holding ring 11 to serve as a cooling surface. Since it works, it is possible to provide the characteristic that the temperature can be kept low over a wide combustion range.

FIG. 2 shows an A view of FIG.
In particular, this is an example showing the situation of the main injection port 2 having multiple injection ports. The main injection port is often determined by the shape of the combustion chamber 25 and the dispersion state of the fuel to be supplied, and is not necessarily the arrangement shown in the drawing. In other words, it has a character to be determined according to the purpose of combustion and the shape of the combustion chamber 25. still,
The cross section of the main injection port 2 of FIG. 1 shows the EE cross section of FIG.

FIG. 3 is a cross section showing an example of the BB cross section of FIG. The flame holding fuel supply hole 3 shown in FIG.
The area is less than a few percent at most, compared to
The number of fuel cells is about the number, and the fuel flow rate is likely to be unbalanced in the circumferential direction. Therefore, in the present invention, the fuel flowing into the flame holding fuel chamber 4 is made to uniformly flow in the circumferential direction in the flame holding fuel throttle hole 15 provided in the first stage throttle 5. Further, the flame holding fuel passage 17 is further homogenized by the second stage throttle 7 so that the flame holding fuel passage 17 passes through the flame holding fuel distribution portion 10 and flows to the back surface of the flame holding ring 11.

FIG. 4 shows an example of the CC cross section of FIG. 1 and has a structure similar to that of FIG. However, since the flame-holding fuel is depressurized, the passage itself becomes large. Therefore, the throttle hole 16 for the second-stage flame-holding fuel is
It is configured to be larger than 5.

FIG. 5 shows an example of the DD cross section of FIG. The flame holding fuel supplied from the flame holding fuel outlet passage 18 flows through the fuel distribution passage 19 and is supplied to the back surface of the flame holding ring 11. As is well known, a condition for a good burner is to be able to burn stably over a wide range of fuel flow rate changes. Therefore, in the present invention, the fuel supplied to the circumference of the guide ring 9 should have a certain distribution. An example in which the protrusion 20 is provided is shown in FIG. The figure shows an example in which the fuel distribution passage is divided into six, but the number of distributions is not particularly limited. Further, the width of the fuel distribution passage 19 can be changed, and the protrusion 20 may be provided with a narrow and shallow gas passage. In short, it is important to give a certain flow rate distribution to the flame-holding fuel supplied from the periphery of the guide ring 9 to create a stable flame on the flame-holding ring 11 regardless of whether the fuel flow rate is low or high. That is.

FIG. 6 is a diagram showing this relationship. For example, in the R portion where the fuel flow rate is high on the circumference of the guide ring 9 in FIG. 5, sufficient fuel for flame holding can be supplied when the total fuel flow rate is relatively low, so that the flame stable region is as shown in FIG. As shown.

On the other hand, the portion S having a small fuel flow rate on the circumference of the guide ring 9 can supply the flame holding fuel 11 with an appropriate amount of flame holding fuel for holding flame when the total fuel flow rate is high. After all, the region where a stable flame can be formed by the flame holding ring 11 of the fuel nozzle can be widened as shown in the figure. As a matter of course, since the R section and the S section are continuously connected, for example, even if the R section and the S section in FIG. You can make it. That is, it is possible to realize a stable combustion width that is twice or more the normal combustion width. Thus, giving a certain flow rate distribution to the amount of the flame holding fuel supplied onto the flame holding ring is an extremely effective means for a wide range of combustion.

The above is a description of the case where the flame holding ring 11 is circular, but as another embodiment of the present invention, it is not a flame holding ring but a straight line (not necessarily a straight line, a curved line is also included in the present invention. Can be applied in the same manner.

FIG. 7 is a partial view showing a specific example in the case of linear expansion. First, with reference to the drawings, a throttle 36 is provided in the flame holding fuel passage 37 composed of the belly plate 31 and the back plate 32, and the flame holding fuel 35 flows as shown. A flame holding fuel distribution plate 38 is provided at the outlet of the flame holding fuel passage 37 so as to be orthogonal to the flow, and the flame holding fuel is supplied to the back surface of the flame holding plate 33 with a certain distribution. Although the diaphragm 36 is shown as a single stage in the drawing, it may be formed in multiple stages when the uniformity is emphasized. An airflow 39 exists on the abdomen of the belly plate 31 and the back of the back plate 32. This air stream 39 may sometimes be a premixed mixture of fuel and air. Such a configuration is just an application of the above ring shape, and this is also included in the present invention.

The present invention proposes a method capable of greatly improving the combustion stability, particularly the combustion of a gaseous fuel.
In particular, a combustion method has recently been proposed which suppresses nitrogen oxides (NOx) generated by combustion as much as possible.
In the Ox combustion state, the flame tends to become unstable, and as a result, there are technical problems that must be solved, such as combustion vibration, failure due to extinction, shortening of the life of the combustor, and reliability of the device. The present invention can solve these technical problems.

The effects of the present invention will be described below. The first effect of the present invention is that flame stabilization can be reliably achieved over a wide combustion range, so pressure fluctuations in the furnace and combustion chamber that occur due to combustion can be suppressed, and a quiet combustion state can be achieved. That is what you can get. A second effect of the present invention is that it is possible to solve a phenomenon in which the flame blows out at the time of ignition of a gas turbine combustor having a wide combustion width. As a result, the gas turbine can be started reliably, and high reliability can be ensured.

The third effect of the present invention is that the quiet combustion state described above can be realized, so that vibrations of the furnace and combustor and wear caused by vibrations can be suppressed, and the life of the equipment can be greatly extended. It can be postponed. The fourth effect of the present invention is that the amount of fuel required for flame holding is a few% or less of the main fuel amount, and therefore a very small amount of fuel is sufficient. Therefore, it is possible to easily realize low NOx combustion by lean combustion, for example. A fifth effect of the present invention is that the combustion of the flame-holding fuel proceeds in advance, so the combustion gas generated by the combustion can be mixed with the main fuel to promote the reduction of NOx. The sixth effect of the present invention is that the flame can be reliably stabilized with an extremely small amount of flame-holding fuel, so that, for example, the main fuel is premixed with combustion air to form a premixed mixture, and then combustion is performed. Premixed combustion can be easily realized. That is,
Extremely low NOx combustion can be realized. A seventh effect of the present invention is that flame propagation in the combustor can be reliably and easily realized by the flame holding fuel.

[0028]

INDUSTRIAL APPLICABILITY As described above, the present invention is extremely effective in improving the performance of a combustor, ensuring reliability, and extending the life of the combustor, and has great economic and environmental benefits. .

[Brief description of drawings]

FIG. 1 is a detailed explanatory view of a combustion unit according to the present invention and is a cross-sectional view showing the relationship between fuel and air.

FIG. 2 is a front view of the fuel nozzle as viewed from A of FIG.

FIG. 3 is a sectional view of the fuel nozzle according to the present invention shown in FIG.

4 is a cross-sectional view taken along line CC of the fuel nozzle according to the present invention shown in FIG.

5 is a cross-sectional view of the fuel nozzle according to the present invention shown in FIG.

FIG. 6 is a diagram for explaining the effect of the flame holding fuel distribution unit, and is an explanatory diagram showing that the stable combustion region can be expanded when a certain distribution is given to the fuel flow rate in the circumferential direction of the flame holding ring.

FIG. 7 is an explanatory view showing a flame holding structure when a flame holding ring is linearized as another specific example according to the present invention.

FIG. 8 is a diagram showing a specific example of a conventional technique.

FIG. 9 is a diagram showing a specific example of a conventional technique.

FIG. 10 is a diagram showing a specific example of a conventional technique.

[Explanation of symbols]

1 ... Gas fuel, 2 ... Main injection port, 3 ... Flame holding fuel supply hole, 4 ...
Flame holding fuel chamber, 5 ... First stage throttle, 6 ... Fuel nozzle body, 7
... 2nd stage throttle, 8 ... Outer cylinder, 9 ... Guide ring, 10 ... Flame holding fuel distribution part, 11 ... Flame holding ring.

Front Page Continuation (72) Inventor Isao Sato 3-1-1 1-1 Saiwaicho, Hitachi City, Ibaraki Hitachi Ltd., Hitachi Works

Claims (9)

[Claims] 1. A combustion apparatus for supplying combustion air to burn gas fuel, comprising one or a plurality of fuel nozzles for supplying gas fuel, each fuel nozzle having a main fuel injection port. One or a plurality of flame holding fuel supply holes are provided separately from the main fuel, and the flame holding fuel is supplied to the flame holding ring having an L-shaped cross section through the flame holding fuel passage. Fuel nozzle structure for gas combustion. 2. The fuel nozzle according to claim 1, wherein the flame holding fuel supplied through the flame holding fuel passage is made to flow along the back surface of the flame holding ring and is supplied to the tip of the flame holding ring. Fuel nozzle structure for gas combustion. 3. The fuel nozzle according to claim 1, wherein one or a plurality of stages of throttles are provided downstream of the flame holding fuel supply hole in order to equalize the flow rate of the flame holding fuel in the circumferential direction of the flame holding fuel passage. A fuel nozzle structure for gas combustion characterized by being provided. 4. The fuel nozzle according to claim 1, wherein the flame-holding fuel supplied through the flame-holding fuel passage is supplied through the flame-holding fuel distributor, and the flow rate of the flame-holding fuel supplied in the circumferential direction of the flame-holding ring is changed. A fuel nozzle structure for gas combustion, characterized in that 5. The fuel nozzle according to claim 1, wherein a guide ring is provided at the tip of the flame holding fuel passage so that the flame holding fuel flows along the back surface of the flame holding ring and is supplied to the tip of the flame holding ring. A fuel nozzle structure for gas combustion, characterized in that 6. A bellows plate and a back plate constitute one or a plurality of flame holding fuel passages, and the tip of the belly plate has an L-shaped cross section to form a flame holding plate, which is provided on the back surface of the flame holding play. A gas combustion structure characterized by supplying flame fuel to stabilize the flame. 7. The gas combustion structure according to claim 6, wherein the flame-holding fuel passage formed by the belly plate and the back plate is provided with one or more stages of throttles to obtain a flame-holding fuel flow rate distribution in the passage cross-sectional direction. Gas combustion structure characterized by being made uniform. 8. The flame-holding fuel to be supplied to the flame-holding plate according to claim 6, wherein a flame-holding fuel distribution plate is provided at the tip of the flame-holding fuel passage formed by the belly plate and the back plate. A structure of gas combustion characterized by changing the flow rate. 9. The gas combustion structure according to claim 6, wherein a guide plate having an L-shaped cross section is provided on the back surface of the flame holding plate, and the flame holding fuel is supplied to the back surface of the flame holding plate. The structure of burning gas.