JPH11153306A - Premix combustor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combustor which enables application for a diversified shapes of a combustion chamber under a lower production cost while promoting a lower NOx designing with the stability of flames. SOLUTION: A flame holding chamber 12 is arranged to be closed by a bottom plate 14 with the side thereof surrounded by a plate-shaped body 13b. A burner port part 17 which comprise a plurality of burner port 16 to inject a premixed gas to the flame holding chamber 12 and a part without the burner port are arranged alternately at least on a part of surfaces 13b as opposed to each other of the plate-shaped body while the part without the burner port is arranged on a surface facing the burner port part 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a premixed combustor for gas combustion used for a fluid heater such as a boiler.

[0002]

2. Description of the Related Art Premixed combustion is widely used in boilers, gas turbines, and the like in recent years because low NOx combustion is possible. FIG. 11 shows the combustion characteristics of the premixed combustion. From this graph, it can be seen that the NOx emission value is maximum near the theoretical air ratio where the air ratio is 1, and when the air ratio is increased to make the fuel lean, the NOx emission value is reduced. When the air ratio is further increased, the CO emission value is increased. It has a characteristic that it extinguishes soon after it increases.

[0003] By utilizing this characteristic, the fuel is made lean and low N
When Ox combustion is performed, the amount of combustion gas for the same amount of combustion increases because the air ratio is large, and the exhaust gas loss increases,
Thermal efficiency deteriorates. Conversely, if the air ratio approaches the stoichiometric air ratio in order to improve the thermal efficiency, the NOx emission value increases as described above, and low NOx combustion cannot be realized. As described above, in the premixed combustion, the improvement of the thermal efficiency, that is, the reduction of the exhaust gas loss and the low NOx combustion have a contradictory relationship.

Therefore, in order to solve this problem and reduce NOx in the normal air ratio, a self-exhaust gas recirculation type combustor utilizing recirculation of combustion gas has been proposed. It is known that the recirculation of the combustion gas suppresses the generation of thermal NOx.
Applying this principle, low NOx combustion is performed by recirculating the combustion gas using the flow characteristics of the flame and the combustion gas in the combustion chamber and mixing it with the unburned premixed gas. .

Conventionally, as a self-exhaust gas recirculation type combustor of this type, for example, as shown in FIG. 12, a flat flame hole group having a plurality of flame holes 1 provided at predetermined intervals is provided. The body 3 is mounted facing the combustion chamber 4, and the premixed gas P is ejected from each of the flame holes 1 of the flame hole body 3. The combustion chamber 4 is located in a region sandwiched between the flames 5 and 5 where no flame hole 1 exists between the flames 2 and 2.
It is known that a recirculating flow 6 of a combustion gas is generated by generating a circulating flow that flows backward from the side toward the flame hole group 2. In this method, the NOx reduction can be achieved with a simple configuration by indirectly utilizing the momentum accompanying the flame ejection to cause the recirculation flow of the combustion gas.

In order to sufficiently generate a recirculating flow of the combustion gas, a flame hole is formed in a part of a peripheral wall of a cylindrical combustion chamber, and the flame hole is formed inside the combustion chamber from the flame hole. There has also been developed one in which a premixed gas is injected substantially in a tangential direction of the combustion chamber.

[0007]

However, in the above-described prior art in which the flame holes provided with the flame holes arranged at predetermined intervals are provided facing the combustion chamber, the self exhaust gas recirculation is indirectly performed. Therefore, the effect of reducing NOx is not sufficient. Further, in the case where a flame hole is formed in a part of the peripheral wall of the cylindrical combustion chamber, the production is considerably troublesome because the flame hole is provided on the peripheral wall of the cylindrical combustion chamber. Not only leads to increased costs,
For example, there is a problem that the method cannot be applied to a rectangular combustion chamber and there is a great restriction in design.

The present invention has been made in view of the above circumstances, and is intended to be applicable to various combustion chamber shapes at a low NOx in the combustion gas, high flame stability, and low production cost. It is an object of the present invention to provide a premixed combustor.

[0009]

SUMMARY OF THE INVENTION A premixed combustor according to the present invention includes a flame holding chamber surrounded by a plate-like body and closed by a bottom plate, and at least one pair of opposing surfaces of the plate-like body. In each of the above, a flame hole portion composed of a plurality of flame holes for ejecting the premixed gas toward the flame holding chamber and a flame holeless portion are alternately arranged, and the facing of the flame hole portion is a flame hole. It is characterized in that a no-part is arranged.

[0010] With this arrangement, since a group of flame holes composed of a plurality of flame holes is ejected as a group, and the non-flame hole portions are disposed on the opposite sides, the premixed gas flows alternately without colliding with each other. Combustion of the premixed air by the local swirl flow causes local swirl flame and self-recirculation flow to stabilize the flame and perform low NOx combustion.

Here, in a large-capacity premixed combustor, the flame holding chamber has a rectangular shape, and the short-side plate-like body has a shape of 1 mm.
It is preferable to arrange two flame hole groups and non-flame hole portions, a plurality of flame hole groups and non-flame hole portions in a plate-like body on the long side alternately along the same circumferential direction. A strong swirling flow is also formed at both ends on the short side of the flame holding chamber having the shape, and the effect of the swirling flame can be further enhanced.

In a small capacity premixed combustor,
A plate-like body that surrounds a side surface of the flame-holding chamber along the same circumferential direction as one flame hole group and a non-flame-hole portion in each of the plate-like bodies on each side. It is preferable to alternately arrange the whirlpools, so that one strong swirling flow can be formed in the flame holding chamber, thereby improving the low NOx property and the stability of the flame.

Further, it is preferable to provide a flame hole group consisting of a large number of flame holes for jetting a premixed gas toward the flame holding chamber on the bottom plate, whereby the combustion capacity can be increased.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show a first embodiment of the present invention, in which a combustion chamber 1 surrounded by a furnace wall 10 is shown.
Inside 1, a combustor 13 having a flame holding chamber 12 that opens in a rectangular shape facing the combustion chamber 11 from the furnace wall 10 is provided. The combustor 13 includes a substantially rectangular hollow flame holding chamber 1.
2 is a plate-shaped body, that is, a pair of short-side end plates 13a,
It is surrounded by a pair of long side inner plates 13b in a rectangular shape, and the bottom of the hollow flame holding chamber 12 is closed by a bottom plate 14.

An outer plate 13c extends along the outer peripheral surface on the long side of the combustor 13, and a premixed gas chamber 15 for holding and guiding the premixed gas P is formed inside the outer plate 13c. ing. As a result, the fuel gas is blown into the air sent from the blower (not shown) to generate a premixed gas P, and the premixed gas P is guided into the premixed gas chamber 15 and held.

A plurality of flame holes 16 communicating between the flame holding chamber 12 and the premixed gas chamber 15 are formed in an inner plate 13b of the combustor 13.
Is formed. This flame hole group 17
In this embodiment, are arranged alternately with the non-flame hole portion 17a at predetermined intervals of three groups on each inner plate 13b. That is, the air-fuel mixture P ejected as a group from each of the flame hole groups 17 flows alternately without colliding with each other, because the air-fuel mixture P faces the non-flame hole portion 17a.

Next, the operation of the above combustor will be described. The premixed gas P held in the premixed gas chamber 15 is directed toward the flame holding chamber 12 from a flame hole group 17 including a flame hole 16 provided in an inner plate 13 b near the bottom of the rectangular flame holding chamber 12. When ignited by an ignition source (not shown), a flame is formed in the hollow flame holding chamber 12. At this time, each inner plate 13
b, the flame hole group 17 is provided alternately with the non-flame hole portion while being separated by a predetermined distance, and the facing of the flame hole group 17 is a flame hole no portion 17a. Forming a local swirling flow between the flowing and adjacent, opposing flows,
As a result, a swirling flame 18 is formed locally between each flame hole group 17 and the flameless portion 17a. In this embodiment, five swirl flames 18 are formed between each flame hole group 17 and the non-flame hole portion 17a.

Here, the premixed gas P forms a swirling flame. Therefore, the heat and radicals of one flame are supplied to the unburned premixed air facing to preheat and protect the facing flame. Can flame. Further, one of the flames supplies combustion gas to the facing flame to lower the oxygen concentration in the combustion region of the facing flame, thereby suppressing the generation of thermal NOx and lowering the NOx.
Combustion can be realized. In addition, the flame is the flame holding room 1
Since the side wall is formed along a part of the inner side surface, the side wall is heated, and the unburned premixture is preheated by the heated side wall, so that the flame holding property is enhanced.

When the swirling flame is formed, the pressure of the airflow at the center of the swirl is reduced, and a self-circulating flow is generated in the center, which flows backward from the combustion chamber 11 toward the bottom plate 14. Further, it works to improve the low NOx property by mixing with the unburned premixed gas. As described above, low NOx combustion can be performed by locally turning and burning the flame.

FIGS. 4 to 6 show a second embodiment of the present invention suitable for a large-capacity combustor, which has a long side surrounding the hollow rectangular flame holding chamber 12. An inner plate 13b extending along the inner peripheral surface of the side surface, an inner end plate 13d extending along the inner peripheral surface on the short side of the combustor 13, and a bottom plate 14 are closed. Further, the premixing chamber 15 for holding and guiding the air-fuel mixture P inside the outer plate 13c extending along the outer peripheral surface on the long side of the combustor 13 and the outer end plate 13e extending along the outer peripheral surface on the short side. Are formed.

In addition to the inner plate 13b in the first embodiment, each of the inner end plates 13d has a plurality of flame holes 1 provided thereon.
Each of the flame hole groups 17 is formed of a group of six. Each of the flame hole groups 17 approaches one corner of the flame holding chamber 12 along the same circumferential direction. A holeless portion 17a is arranged.

Thus, a strong swirling flame 18 can be formed at both short-side end portions of the flame holding chamber 12.
That is, at both end portions of the flame holding chamber 12, two groups of the flame hole groups 17 and the non-flame hole portion 17a provided at positions facing each other on the inner plate 13b, and the flame hole group 17 provided at the inner end plate 13d.
And the configuration of the non-air hole portion 17a, a total of three groups
The swirl flame can be formed by the premixed gas ejected from the nozzle, so that all the flames become flames having a sufficient swirl force, and the effect accompanying the swirl flame can be further enhanced.

Here, as shown in FIGS. 7 and 8, a flame hole group 17 comprising a large number of flame holes 16 communicating the flame holding chamber 12 and the premixing chamber 15 is provided on the bottom plate 14 at predetermined intervals. It is preferable that the combustion capacity can be further increased. This is the same in the first embodiment and the following embodiments.

FIGS. 9 and 10 show a third embodiment of the present invention suitable for a small-capacity combustor, which is a flame holding chamber 12 having a substantially square cross section as a combustor 13. And, on each of the inner plate 13b and the inner end plate 13d surrounding the flame holding chamber 12, a flame hole group 17 and a flame holeless portion 17a are arranged along the same circumferential direction. On the opposite side of the group 17, a non-flame hole portion 17a is arranged.

As a result, the premixed gas P is jetted from the flame hole group 17 provided at the four corners so as to form a swirling flow, so that one strong air is injected into the substantially square flame holding chamber 12. The swirl flame 18 can be formed to further enhance the excellent characteristics of the swirl flame.

In each of the above embodiments, the combustion chamber 11 may be cylindrical or rectangular as long as it has a size larger than the flame holding chamber 12. Thereby, the applicable range of the combustor can be extremely widened. Further, a plurality of flame holding chambers can be provided in the combustion chamber.

Further, since the flame holes are provided in the plate-like body, the work of providing the flame holes in the plate-like body can be performed extremely easily. As this material, for example, a flat plate excellent in heat insulation and heat resistance such as a ceramic material or a heat-resistant stainless steel material having a refractory material attached to the surface is suitable. Both materials are readily available and can be easily manufactured at very low manufacturing costs.

[0028]

As described above, according to the present invention, a plurality of flame holes are blown out as a group from a plurality of flame holes, and a flameless portion is provided on the opposing surface of the combustor. The combustion by the local swirl flow formed by the premixed gas flowing alternately without collision is performed,
Low NOx combustion can be performed by causing a local swirling flame and a self-recirculating flow.

Moreover, since the flame holes are provided in the plate-like body,
The operation of providing the flame holes is extremely easy, and the manufacturing cost is reduced.The combustion chamber may be cylindrical or rectangular, as long as the dimensions are larger than the flame holding chamber. Thereby, the applicable range of the combustor can be extremely widened.

Further, the flame holding chamber is formed in a rectangular shape, and a flame hole group is provided in each plate-like body surrounding the flame holding chamber, so that a structure suitable for a large-capacity combustor can be made. By providing a group of flame holes in each plate-like body surrounding the flame holding chamber to generate one strong swirling flame, a configuration suitable for a small-volume combustor can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view (FIG. 2) showing a first embodiment of the present invention;
AA sectional view of FIG.

FIG. 2 is a sectional view taken along line BB of FIG. 1;

FIG. 3 is a sectional view taken along line CC of FIG. 2;

FIG. 4 is a sectional view (FIG. 5) showing a second embodiment of the present invention;
DD sectional view).

FIG. 5 is a sectional view taken along line EE of FIG. 4;

FIG. 6 is a sectional view taken along line FF of FIG. 5;

FIG. 7 is a sectional view (a sectional view taken along line GG of FIG. 8) showing a modification of the second embodiment of the present invention;

FIG. 8 is a sectional view taken along line HH of FIG. 7;

FIG. 9 is a sectional view (FIG. 1) showing a third embodiment of the present invention;
0 II line cross-sectional view).

FIG. 10 is a sectional view taken along line JJ of FIG. 9;

FIG. 11 is a graph showing combustion characteristics of premixed combustion.

FIG. 12 is a cross-sectional view of a conventional premixed combustor.

[Explanation of symbols]

 Reference Signs List 12 flame holding chamber 13 combustor 14 bottom plate 15 premixing chamber 16 flame hole 17 flame hole group 18 swirling flame

Claims (4)

[Claims] 1. A flame holding chamber which is surrounded by a plate-shaped body and closed by a bottom plate, wherein a premixed gas is supplied to each of at least one pair of opposed surfaces of the plate-shaped body. Premixed combustion characterized by alternately arranging a flame hole portion composed of a plurality of flame holes ejected toward the nozzle and a non-flame hole portion, and facing the flame hole portion with a flame holeless portion. vessel. 2. The flame holding chamber is formed in a rectangular shape, and one flame hole group and a non-flame hole portion are formed on a short side plate, and a plurality of flame hole groups and a flame are formed on a long side plate. 2. The non-perforated portions are alternately arranged along the same circumferential direction.
A premixed combustor as described. 3. The flame holding chamber has a substantially square shape, and one flame hole group and one flame hole-free portion are alternately arranged on the plate-like body on each side along the same circumferential direction. The premixed combustor according to claim 1, wherein 4. The preheating apparatus according to claim 1, wherein a flame hole group including a large number of flame holes for jetting a premixed gas toward the flame holding chamber is provided on the bottom plate. Mixed combustor.