JP2004092981A - Two-stage combustion device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a two-stage combustion device promoting the mixing with secondary air and reducing NOx, while inhibiting the generation of a combustion noise by minimizing the turbulence. <P>SOLUTION: An air blowout port 3 is formed on a central position in a state of being projected to a front side of a combustion space 2 and being higher than a plurality of burner port flames 42 from burner port faces 4, 4, and a narrowed part 23 is formed near the air blowout port 3, by projecting guide walls 22, 22 into a combustion space 2 in a state of covering the burner port faces 4. The burner port flames are formed on the burner port faces by an excessively enriched fuel gas having high concentration of the fuel of insufficient air, and the combustion gas including much unburnt component generated from the burnt port flames of which the elongation is inhibited by the guide walls, is guided to a narrowed part by the guide walls. The secondary air from the air blowout port is blown out to the combustion gas flowing to the narrowed part toward a front part of the combustion space, so that the unburnt component in the combustion gas can be completely burnt while inhibiting the turbulence and promoting the mixing. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
In the present invention, the rich fuel-air mixture is burned at the flame hole surface in the first stage, and the secondary air is blown out in the second stage for the combustion gas containing a large amount of unburned components generated by the combustion so as to be completely burned. In particular, the present invention relates to a technique for sufficiently mixing the blown-out secondary air and combustion gas while preventing the turbulent flow between the two and reducing NOx.
[0002]
[Prior art]
Conventionally, it is said that a Bunsen-type burner hardly generates combustion vibration (combustion noise) and can realize a high TDR (Turn Down Ratio: turndown ratio or throttle ratio), but emits a large amount of NOx. For example, as shown in FIG. 8, secondary air is blown to the outer flame Bo of the Bunsen flame B to lower the outer flame temperature to achieve complete combustion of unburned components, thereby reducing the NOx. It is also considered to plan. An example of such a combustion device that blows out secondary air is proposed in Japanese Patent Publication No. 4-32287. In this device, secondary air is blown out in parallel to a flame hole flame formed on a flame hole surface.
[0003]
Another example is proposed in JP-A-10-169910. In this apparatus, an obstacle is installed in the center of the combustion space in order to promote the mixing of the combustion gas and the secondary air generated from the flame with the boiler furnace, and the combustion gas and the secondary A vortex is generated in both the air to make it turbulent.
[0004]
[Problems to be solved by the invention]
However, in the combustion device proposed in Japanese Patent Publication No. 4-32287, there is a disadvantage that when the secondary air is brought into direct contact with the flame flame, the generation of NOx is increased. The mixing with the secondary air cannot be promoted. On the other hand, in the combustion device proposed in the above-mentioned Japanese Patent Application Laid-Open No. 10-169910, significant combustion noise is generated due to the active formation of the vortex. Although this is not a problem in the case of a boiler furnace, such a technique cannot be applied to a combustion device such as a water heater in which combustion noise is to be minimized.
[0005]
The present invention has been made in view of such circumstances, and an object of the present invention is to suppress mixing of turbulence as much as possible and to suppress generation of combustion noise, while promoting mixing with secondary air. It is an object of the present invention to provide a two-stage combustion device capable of reducing NOx.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention, a flame hole surface in which an air concentration is lower than the theoretical combustion air amount and a rich fuel gas having a high fuel concentration is burned toward a combustion space, and the flame hole surface is formed on the flame hole surface. And a blow-off section for blowing secondary air to the combustion gas generated from the flame hole flame. In addition, a flame flame from the flame hole surface is provided on the combustion space side of the flame hole surface. And a guide wall for guiding the flow of the combustion gas from the flame flame toward the air ejection portion side (claim 1).
In the case of the present invention, since the rich fuel gas is burned on the flame surface, the flame generates a combustion gas containing a large amount of unburned components, and the combustion gas is guided to the air ejection portion by the guide wall. Then, the fuel is completely burned by the secondary air blown out from the air blowing part. At this time, since the guide wall is opposed by the guide wall so as to cover the flame, the extension of the flame is suppressed, and the direct contact between the secondary air from the air ejection part and the flame is suppressed. , The secondary air will be blown out directly to the combustion gases and not to the flame. As a result, it is possible to avoid NOx increase due to direct contact between the secondary air and the flame, thereby reducing NOx. In addition, since the combustion gas is guided toward the air ejection portion by the guide wall, the combustion gas can be mixed with the secondary air without turbulence. Thereby, mixing can be promoted while suppressing generation of combustion noise.
[0007]
The “enriched fuel gas having an air concentration lower than the theoretical combustion air amount and a higher fuel concentration” means that the excess air ratio is less than 1.0, which is smaller than the theoretical combustion air amount required for complete combustion. In addition to the rich fuel-air mixture containing a deficient amount of air, it is intended to include the fuel gas itself containing no air.
[0008]
In the above-described two-stage combustion device of the present invention, it is preferable that the blowing direction of the secondary air from the air blowing part is set so that the secondary air is blown toward the front of the combustion space (claim 2). . In this case, since the secondary air is blown toward the front of the combustion space from the air ejection part, the combustion gas and the secondary air are mixed without greatly disturbing the flow of the combustion gas guided to the air ejection part. Is performed. Then, the unburned components in the combustion gas that has received the secondary air burn toward the front of the combustion space. In other words, the above setting of the secondary air blowing direction rectifies the flow of the combustion gas guided to the air jetting portion into a flow forward of the combustion space without significantly disturbing the flow, and changes the direction of combustion of the unburned components. It becomes possible to arrange in front of the combustion space.
[0009]
In this case, it is preferable to employ, as the guide wall, a configuration in which the combustion gas is guided so that the secondary air intersects the flow of the combustion gas guided to the air ejection portion at a shallow angle. (Claim 3). By blowing such secondary air, the turbulence of the flow of the combustion gas is further suppressed, and the secondary air penetrates into the flow of the combustion gas to further promote the mixing with the secondary air. Can be achieved.
[0010]
As a more specific configuration for realizing the two-stage combustion device according to any one of claims 1 to 3, the following various specific configurations can be employed.
[0011]
That is, as a first specific configuration, the air ejection portion is provided so as to protrude forward of the combustion space from the flame hole flame from the flame hole surface (claim 4). In the case of this configuration, the secondary air blown out from the air ejection part and the flame flame from the flame hole surface are surely separated and cut off, and the secondary air emits the combustion gas generated from the flame hole flame. Can be brought into contact only with As a result, it is possible to more reliably avoid an increase in NOx due to direct contact between the secondary air and the flame, and to achieve a more reliable NOx reduction.
[0012]
As a second specific configuration, between the air ejection portion and the flame hole surface, the flame hole flame from the flame hole surface and the mutual contact between the air and the secondary air from the air ejection portion are separated from each other. A partition wall projecting forward of the combustion space from the flame flame is provided (claim 5). In the case of this configuration, the same operation as that of the fourth aspect can be obtained by means different from the fourth aspect. That is, the secondary air blown out from the air jetting section and the flame hole flame from the flame hole surface are reliably separated and cut off by the partition wall, and the secondary air is separated from the combustion gas generated from the flame hole flame. Only contact. As a result, it is possible to more reliably avoid an increase in NOx due to direct contact between the secondary air and the flame, and to achieve a more reliable NOx reduction. In addition, in the case of this specific configuration, it is possible to set the position of the air jetting portion to a position that is concave instead of a position that protrudes from the flame hole surface.
[0013]
When the first and second specific configurations are further embodied, the air ejection portion is disposed at the center position with respect to the combustion space, and the flame hole surface is disposed at the side position of the air ejection portion, respectively. A narrow portion is formed in the combustion space by the edge, and the secondary air from the air ejection portion is blown toward the front of the combustion space with respect to the combustion gas passing through the narrow portion ( Claim 6). In this case, both promotion of mixing of the combustion gas and the secondary air and prevention of turbulence of the combustion gas by blowing the secondary air are more reliably achieved.
[0014]
In the case of the above configuration, the following various specific configurations may be added.
[0015]
That is, first, the inner edge of the guide wall is bent toward the front of the combustion space, and the opening area of the constriction formed by the inner edge gradually decreases toward the front of the combustion space. It is formed (claim 7). In this case, the flow of the combustion gas that has been blown out of the secondary air is rectified into a flow that is directed forward of the combustion space, thereby further preventing turbulence.
[0016]
Secondly, the guide wall is configured such that the combustion space from the flame hole surface to the narrowed portion is continuously narrowed (claim 8). In this case, smooth guidance of the combustion gas can be realized, which can contribute to prevention of turbulence in the constricted portion.
[0017]
Thirdly, the flow velocity of the secondary air from the air ejection part is set to be lower than the flow velocity of the combustion gas passing through the constricted part (claim 9). Thus, turbulence is prevented.
[0018]
【The invention's effect】
As described above, according to the two-stage combustion device according to any one of claims 1 to 9, the elongation of the flame hole flame from the flame hole surface can be suppressed by the guide wall, and from the air ejection portion. The direct contact between the secondary air and the flame can be suppressed, and the secondary air can be blown out directly to the combustion gas instead of to the flame. Thus, it is possible to avoid an increase in NOx caused by the direct contact between the secondary air and the flame and reduce NOx. In addition, since the combustion gas is guided to the air ejection side by the guide wall, the combustion gas can be mixed with the secondary air while suppressing the turbulence of the combustion gas, thereby suppressing the generation of combustion noise. Mixing can be promoted.
[0019]
In particular, according to the second aspect, by setting the blowing direction of the secondary air to be blown toward the front of the combustion space, the flow of the combustion gas guided to the air blowing portion is not significantly disturbed. By rectifying the flow to the front of the combustion space, the direction of combustion of the unburned component can be adjusted to the front of the combustion space. According to the third aspect, while further suppressing the turbulence of the flow of the combustion gas, the secondary air penetrates to the inside of the flow of the combustion gas to further promote the mixing with the secondary air. Can be planned.
[0020]
According to any one of the first to third aspects, according to the fourth aspect, the secondary air blown from the air jetting portion and the flame hole flame from the flame hole surface are reliably separated and blocked. The secondary air can be brought into contact only with the combustion gas generated from the flame. Thus, it is possible to more reliably avoid the increase in NOx caused by the direct contact between the secondary air and the flame, and to realize the lower NOx more reliably. According to the fifth aspect, the same effect as that of the fourth aspect can be obtained by means different from the fourth aspect.
[0021]
Further, according to the sixth aspect, it is possible to more reliably achieve both the promotion of mixing of the combustion gas and the secondary air and the prevention of turbulence of the combustion gas by blowing the secondary air. In addition, according to claim 7, the flow of the combustion gas blown out of the secondary air is rectified into a flow directed forward of the combustion space, whereby further prevention of turbulence can be achieved. According to this aspect, it is possible to realize smooth guidance of the combustion gas and to contribute to the prevention of turbulence in the constricted portion. It is possible to ensure the prevention of fluidization.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0023]
<First embodiment>
FIG. 1 shows a two-stage combustion device according to a first embodiment of the present invention. In this combustion device, an air ejection portion 3 protruding a predetermined amount toward the front combustion space 2 is disposed at the center position, and one or more combustion tubes 41, 41 are provided at side positions of the air ejection portion 3. ,... Are provided. The above "center position" and "side position" mean that if the combustion device is a cylindrical type, the air ejection portion 3 is disposed at the center side of the combustion device, and the flame hole surface 4 is located at the outer peripheral side so as to surround the air ejection portion 3. That is, if the combustion device is a rectangular cylinder having a rectangular shape in a plan view, the air ejection portion 3 is provided at the center position in the width direction, and the flame hole surfaces 4 are provided at both outer positions with the air ejection portion 3 interposed therebetween. It is to be arranged.
[0024]
The combustion space 2 is a space defined by the wall 21 of the apparatus main body and expanding from the flame hole surface 4 to the front side (downstream side; upper side in FIG. 1). Is arranged. For example, in the case of a water heater, a heat exchanger for heat-exchanging and heating water passing therethrough is provided as a heating target.
[0025]
A guide wall 22 projecting from the wall 21 toward the center from the wall 21 is provided at a position on the front side (downstream position) of the front end of the air ejection section 3, and the inner end edge 221 of the guide wall 22 causes the combustion. A constriction 23 is formed in the space 2. The guide wall 22 is disposed so as to face the flame hole surface 4 at a position (downstream position) on the front side of the combustion space with respect to the flame hole surface 4, while facing the opening position of the constricted portion 23 to discharge the air. The part 3 is arranged.
[0026]
The guide wall 22 is configured such that a cooling fluid (for example, air) 222 is circulated therein, and the cooling fluid is circulated to the inner edge 221 to expose the wall surface exposed to the combustion space 2. Is to be cooled.
[0027]
The air blow-out section 3 is configured to blow air into the inside thereof. The air blows out from the blow-out holes 31, 31,... Combustion gas is blown out. Each of the ejection holes 31 is opened toward the constricted portion 23 so that secondary air (see the dotted arrow in FIG. 1) is ejected toward the front of the combustion space 2. Further, the air ejection portion 3 is disposed so as to protrude forward (downstream) of the combustion space 2 from flame hole flames 42, 42,... From the flame hole surface 4.
[0028]
Each combustion pipe 41 constituting the flame hole surface 4 is supplied with a rich fuel mixture having a high fuel concentration and an excess air ratio set to less than 1.0 (100%). On the hole surface 4, flames 42, 42,... Which are incompletely burned flames are formed by the primary combustion of the rich fuel mixture. Then, the combustion gas containing a large amount of unburned components generated from the flame 42 is guided by the guide wall 22 and flows toward the constricted portion 23, that is, the air ejection portion 3 side. Secondary air is blown out of the fuel cell 3 so that unburned components in the combustion gas are completely burned (secondary combustion). It should be noted that primary combustion may be performed by supplying a fuel gas itself that is not premixed with air to each of the combustion pipes 41 instead of the rich fuel mixture. Also in this case, the two-stage combustion in the present embodiment can be applied only by increasing the unburned components in the combustion gas. Further, the above-described rich fuel gas (rich fuel mixture or fuel gas itself) supplied for primary combustion at the flame hole surface 4 is the same in the following embodiments.
[0029]
In the case of the two-stage combustion device of the first embodiment described above, since the guide wall 22 covers the front of the flame hole surface 4, the expansion of the flame hole flames 42, 42,. , Only the combustion gas can be guided, and the secondary air from the air jetting section 3 can be blown only to the combustion gas. That is, the guide wall 22 separates and blocks the direct contact between the secondary air from the air ejection part 3 and the flame hole flames 42, 42,..., And is generated from the flame hole flames 42, 42,. The function of guiding the flow of the combustion gas so as to intersect with the secondary air blown out from the air blowing unit 3 is exhibited. By the separation / shutoff function, it is possible to avoid the increase in NOx caused by the secondary air coming into direct contact with the flames 42, 42,. Thereby, the secondary air can be penetrated and supplied to the inside of the combustion gas while suppressing the turbulence of the combustion gas, so that the mixing of the combustion gas and the secondary air can be promoted. By suppressing the turbulence, the generation of combustion noise can be suppressed as much as possible, and the unburned components can be completely burned by promoting the mixing. Further, the temperature of the combustion gas can be reduced by contact with the secondary air to contribute to the reduction of NOx.
[0030]
In addition, the secondary air is blown toward the front of the combustion space 2 through the opening of the constriction 23, and the combustion gas is blown toward the front of the combustion space 2 by the secondary air. The secondary combustion of unburned components in the combustion gas can be directed to the front of the combustion space 2 while blowing the combustion gas toward the front of the combustion space 2 without significantly disturbing the flow of the combustion gas.
[0031]
<Second embodiment>
FIG. 2 shows a two-stage combustion device according to a second embodiment of the present invention. The two-stage combustion apparatus of the second embodiment has the same principle of the two-stage combustion as that of the first embodiment, but employs a guiding wall having a shape different from that of the first embodiment. Since the other components are the same as those of the first embodiment, the same components are denoted by the same reference numerals, and detailed description thereof will be omitted.
[0032]
In the second embodiment, the guide wall 22a is formed by bending the wall 21a of the apparatus body so as to draw a gentle curve from the position of the flame hole surface 4 to the front (upward in FIG. 2) so as to reduce the diameter or reduce the inner width. The constriction 23a is formed between the inner edges 221a, which are the minimum constrictions. The air ejection portion 3 is arranged so as to face the narrowed portion 23a from a position before the narrowed portion 23a.
[0033]
In the second embodiment, the combustion gas from the flames 42, 42,... Is more smoothly guided toward the constricted portion 23a and the air ejection portion 3 than in the first embodiment. Is blown out in a direction obliquely intersecting the flow of the combustion gas at a shallower angle than in the case of the first embodiment. This makes it possible to suppress or avoid turbulence due to the blowing of the secondary air at the position of the constricted portion 23a as compared with the case of the first embodiment, and to realize quiet combustion with low combustion noise.
[0034]
<Third embodiment>
FIG. 3 shows a two-stage combustion device according to a third embodiment of the present invention. The two-stage combustion device according to the third embodiment employs the guide wall of the second embodiment while adopting a structure different from that of the second embodiment as the air ejection portion.
[0035]
In the third embodiment, the inner width is gradually or gradually increased from the flame hole surface 4 formed by the flame holes at the tip ends of the plurality of combustion tubes 41, 41,... Toward the front of the combustion space 2 (upward in FIG. 3). The guide wall 22b is formed by narrowing it narrowly, and the constriction 23b is formed by the distal end edge 221b which is the inner edge. In addition, the air supply passages 51, 51 are formed behind the guide wall 22b using the guide wall 22b, and the air is converted into secondary air toward the front of the narrowed portion 23b (upward in FIG. 3) at the distal end edge 221b. The ejection holes 52 to be ejected are formed. The supply passage 51 and the ejection hole 52 constitute the air ejection portion 5.
[0036]
In the case of the third embodiment, the air can be blown out to the combustion gas as secondary air while cooling the guide wall 22b so as not to be overheated by the supplied air.
[0037]
<Fourth embodiment>
FIG. 4 shows a two-stage combustion device according to a fourth embodiment of the present invention. The two-stage combustion device of the fourth embodiment is provided with a guide wall 22c that covers the flame hole surface 4 constituted by the flame holes at the tip end of one or more combustion tubes 41, 41,. At the positions on both sides of the flame hole surface 4, projecting portions 24, 24 are formed opposite to the projecting portions of the guide wall 22 c to form the primary combustion space 2 a.
[0038]
Then, both side edges (inner edges) 221c, 221c of the guide wall 22c and the respective edges 241 of the both overhang portions 24, 24 are formed in a convex shape, and constricted portions 23c, 23c are formed therebetween.
[0039]
Further, an air supply path 61 is formed behind the guide wall 22c, and air supply paths 62, 62 are formed behind the projecting portions 24. The air flows at the narrowed portions 23c. The ejection holes 63 are formed so as to blow out as secondary air. The supply passages 61 and 62 and the respective ejection holes 63 constitute the air ejection unit 6.
[0040]
In the fourth embodiment, the flames 42, 42,... From the flame hole surface 4 are covered by the guide wall 22c to suppress the elongation, and the combustion gas generated from the flames 42, 42,. And are guided so as to flow to the constricted portions 23c. Then, the unburned components in the combustion gas are completely burned toward the secondary combustion space 2b by receiving the blowing of the secondary air at the positions of the constrictions 23c. In addition, when the air for the secondary air passes through the supply passages 61, 62, and 62, the guide wall 22c and the walls of the overhang portions 24 are cooled so as not to be overheated.
[0041]
<Fifth embodiment>
FIG. 5 shows a two-stage combustion device according to a fifth embodiment of the present invention. In the two-stage combustion device of the fifth embodiment, the partition wall 25 for separating the flame hole flames 42 from the flame hole surface 4 from direct contact with the secondary air from the air ejection part 7 to separate them. , 25 are provided.
[0042]
That is, the air ejecting portion 7 at the center position is disposed at a position (a lower position in FIG. 5) closer to the flame hole surfaces 4 and 4 on both sides thereof, and the air ejecting portion 7 is Partition walls 25, 25 projecting forward (downstream side; upper side in the drawing) of the combustion space 2 from flame hole flames 42, 42,... The projecting dimension of each partition wall 25 may be determined in consideration of the pressure, flow rate, and the like of the rich fuel mixture to the flame hole surface 4, but in the case of the present embodiment, a flame hole formed by a guide wall 22d described later. Considering the suppression of the elongation of the flames 42, 42,..., A relatively short one is sufficient. A guide wall 22d is provided in front of each of the burnt hole surfaces 4 so as to cover each of the burnt hole surfaces 4, and a narrowed portion 23d is provided between the inner end edges 221d and 221d of the guide walls 22d. The blowing direction and the positional relationship of the secondary air from each blowout hole 71 of the air blowout portion 7 to the constricted portion 23d and the combustion space 2 are the same as in the first embodiment.
[0043]
In the case of the fifth embodiment, the combustion gas from the flame holes 42, 42 formed on each flame surface 4 is guided by the guide wall 22d, and the inner edge 221d of the partition wall 25 and the guide wall 22d. And the unburned component in the combustion gas is completely combusted toward the front of the combustion space 2 by receiving the secondary air blown from the air jetting portion 7 at the constricted portion 23d. become. At this time, it is possible to reliably prevent the secondary air from being directly blown out to the flames 42, 42,... By the partition walls 25, 25 and to blow out the secondary air only to the combustion gas. As a result, it is possible to realize more reliable NOx reduction. Further, the unburned components are also burned by the secondary air blown out from the ejection holes 7 of the air ejection portion 7a provided at the front side position (the upper side position in FIG. 5) of the guide walls 22d, 22d. Become.
[0044]
FIG. 6 shows an example in which a slightly different shape from that of the two-stage combustion device of FIG. 5 is adopted as belonging to the fifth embodiment. In the two-stage combustion device of FIG. This indicates that the relative position of the air ejection portion 7 with respect to the vertical direction in FIG. 6 may be set at a position ahead (upper position) of the flame hole surface 4.
[0045]
<Other embodiments>
Note that the present invention is not limited to the above-described first to fifth embodiments, but includes various other embodiments. That is, the shapes of the inner edges 221, 221a, 221b, 221d of the guide walls 22, 22a, 22b, 22d in the first to third and fifth embodiments are gradually opened toward the front of the combustion space 2. A bell mouth shape that reduces the area may be employed. For example, like the guide wall 22e shown in FIG. 7 illustrating the first embodiment as an example, the inner end edge 221e is bent forward (upward in FIG. 7) of the combustion space 2 so that the constriction portion goes forward. The bell mouth shape may be such that the opening area of 23e is reduced.
[Brief description of the drawings]
FIG. 1 is an explanatory sectional view showing a first embodiment of the present invention.
FIG. 2 is an explanatory sectional view showing a second embodiment.
FIG. 3 is an explanatory sectional view showing a third embodiment.
FIG. 4 is an explanatory sectional view showing a fourth embodiment.
FIG. 5 is an explanatory sectional view showing a fifth embodiment.
FIG. 6 is an explanatory sectional view showing another example of the fifth embodiment.
FIG. 7 is an explanatory sectional view showing an example of another embodiment.
FIG. 8 is an explanatory sectional view for explaining a conventional problem.
[Explanation of symbols]
2 Combustion space 3,5,6,7 Air ejection part 4 Flame hole surface 22,22a, 22b, 22c, 22d Guiding wall 23,23a, 23b, 23c, 23d Narrow part 25 Partition wall 42 Flame hole flames 221, 221a, 221d Inner edge 221b Tip edge (inner edge)
221c Side edge (inner edge)

Claims (9)

A flame surface for burning rich fuel gas having a lower air concentration than the theoretical combustion air amount and a higher fuel concentration toward the combustion space, and a combustion gas generated from a flame formed on the flame surface as a secondary gas. A two-stage combustion device having an air ejection portion for blowing air,
A guide wall is formed on the combustion space side of the flame hole surface so as to cover the flame hole flame from the flame hole surface, and guides the flow of combustion gas from the flame hole flame to the air ejection portion side. A two-stage combustion device characterized by being performed. The two-stage combustion device according to claim 1,
The two-stage combustion device, wherein the secondary air is blown from the air blowing part in such a manner that the secondary air is blown toward the front of the combustion space. The two-stage combustion device according to claim 2, wherein
The two-stage combustion device, wherein the guide wall is configured to guide the combustion gas such that the secondary air intersects the flow of the combustion gas guided to the air ejection part at a shallow angle. The two-stage combustion device according to any one of claims 1 to 3, wherein
The two-stage combustion device, wherein the air ejection portion is provided so as to protrude forward of the combustion space from a flame hole flame from the flame hole surface. The two-stage combustion device according to any one of claims 1 to 3, wherein
Between the air ejection portion and the flame hole surface, the combustion space is larger than the combustion hole flame so as to separate the contact between the flame flame from the flame hole surface and the secondary air from the air ejection portion. A two-stage combustion device provided with a partition wall protruding forward. The two-stage combustion device according to claim 4 or claim 5,
The air ejection portion is disposed at the center position with respect to the combustion space, and the flame hole surface is disposed at the side position of the air ejection portion, respectively,
A constriction is formed in the combustion space by the inner edge of the guide wall,
A two-stage combustion device, wherein the secondary air from the air ejection part is blown toward the front of the combustion space toward the combustion gas passing through the narrowed part. The two-stage combustion device according to claim 6,
The inner edge of the guide wall is bent toward the front of the combustion space, and is formed in a bell-mouth shape in which the opening area of the constriction formed by the inner edge gradually decreases toward the front of the combustion space. Stage combustion device. The two-stage combustion device according to claim 6,
The two-stage combustion device, wherein the guide wall is configured such that a combustion space from a flame hole surface to a narrow portion is continuously narrowed. The two-stage combustion device according to claim 6,
A two-stage combustion device, wherein a flow velocity of secondary air from the air ejection part is set to be lower than a flow velocity of combustion gas passing through the narrow part.

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