JP2004205176A - Two-stage combustion device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a two-stage combustion device capable of minimizing NOx by maintaining a burner port flame while using excessively rich mixture with an excess air ratio lowered near an inflammable limit. <P>SOLUTION: A porous flame holding member 9 is disposed so as to cover the combustion space 3 side of a mixture spraying port 51 forming a burner port part 5b. A burner port flame 52 is formed at an upper surface position when the excessively rich mixture sprayed from the mixture spray port passes through the continuous small hole of the flame holding member. The flame holding member is heated reddish by hot combustion gas produced from the burner port flame to hold the burner port flame. The combustion gas including unburned components produced from the burner port flame is guided by a guide wall and flowed to an air spraying part, and completely burned by secondary air from the air spraying port. Swirl flow may be caused by the collision of the spraying flow of the excessively rich mixture and the entrainment thereof at end edges and a flow passage may be rapidly enlarged to maintain the flame. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
According to the present invention, in a first stage, a rich mixture having an excessively high fuel concentration is burned on a flame surface, and secondary air is blown out in a second stage with respect to a combustion gas containing a large amount of unburned components generated by the combustion. In particular, the present invention relates to a technique for reducing NOx as much as possible by reliably holding a flame in the flame hole surface by the rich mixture. .
[0002]
[Prior art]
Conventionally, it is said that a Bunsen-type burner hardly generates combustion oscillation (combustion noise) and can realize a high TDR (Turn Down Ratio: throttle ratio), but has a large NOx emission. To reduce NOx, secondary air is blown into the outer flame of the Bunsen flame to lower the outer flame temperature and complete combustion of unburned components, thereby reducing NOx. A combustion device that blows out such secondary air is also known (for example, see Patent Document 1). In this device, secondary air is blown out in parallel to a flame hole flame formed on a flame hole surface.
[0003]
As another example, an obstacle is installed at the center in the combustion space in order to promote the mixing of the combustion gas generated from the flame and the secondary air with the boiler furnace, and the combustion gas and A vortex is generated in both of the secondary air to positively generate turbulence (for example, see Patent Document 2).
[0004]
[Patent Document 1]
Japanese Patent Publication No. 4-32287
[Patent Document 2]
JP-A-10-169910
[0005]
[Problems to be solved by the invention]
However, in the combustion device proposed in Patent Document 1 described above, when the secondary air comes into direct contact with the flame flame, the generation of NOx is increased, and the unburned component and the secondary air Mixing promotion cannot be achieved. On the other hand, in the combustion device proposed in Patent Document 2 described above, 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.
[0006]
In view of the above, the applicant of the present application has filed Japanese Patent Application No. 2002-253584 in which the turbulence of combustion gas is suppressed as much as possible to suppress the generation of combustion noise, while promoting the mixing of unburned components with secondary air. And proposed a two-stage combustion device that can achieve low NOx.
[0007]
The present applicant has been developing and testing a two-stage combustion device capable of further reducing NOx while obtaining a predetermined action and effect equal to or higher than that of the proposed two-stage combustion device. Of knowledge. That is, if the fuel concentration of the rich mixture (primary mixture) for forming the primary flame which is the incomplete combustion flame in the two-stage combustion is set to a predetermined high concentration range, in other words, the excess air ratio is reduced as much as possible. It was found that if possible, NOx could be reduced as much as possible.
[0008]
FIG. 15 shows the experimental results when methane gas was used as fuel. According to the experimental results, the NOx generation concentration was extremely low until the excess air ratio (m value) of the primary air-fuel mixture was around 0.65. However, when the m value becomes larger than about 0.65, the NOx generation concentration increases at a high rate with the increase of the m value. That is, in the relationship between the NOx generation concentration and the m value, there is an inflection point (m value = about 0.65) in the m value, and the low m value region up to the inflection point is a low NOx concentration region. At the inflection point, the NOx generation concentration becomes a minimum, and when the value of m increases from the inflection point, the NOx generation concentration increases dramatically. This tendency is considered to be the same for fuels other than methane gas. In the experiments described above, both the generation of the primary air-fuel mixture and the supply of the secondary air are performed by supplying air from the same blower fan. For this reason, the overall air excess ratio mt based on the sum of the amount of air contained in the primary air-fuel mixture and the amount of secondary air increases almost linearly with an increase in the air excess m of the primary air-fuel mixture. It can be understood from FIG. 15 that the inflection point exists although the total excess air ratio mt is weak.
[0009]
From the above, if the rich mixture having a considerably low m value near the inflection point near the flammability limit is used as the primary mixture, the NOx can be reduced as much as possible along with the lowering of the flame temperature. In addition, it is considered that the required amount of air supply is also reduced, which contributes to downsizing of the blower fan. On the other hand, when the m value is set to such a low value, the burning speed of the flame hole flame is remarkably reduced, and accordingly, a lift or a blow-off is caused, so that it becomes difficult to hold the flame or the flame hole flame becomes longer. This is expected to cause a disadvantage that the two-stage combustion device is enlarged due to separation of the flame and the secondary air.
[0010]
The present invention has been made in view of such circumstances, and the purpose thereof is to achieve flame holding of a flame hole flame while using a rich air-fuel mixture with a considerably low excess air ratio. An object of the present invention is to provide a two-stage combustion device capable of reducing NOx as much as possible.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, according to a first aspect of the present invention, as a two-stage combustion device, a combustion space defined by a cylindrical inner surface having an open front end and a closed base end, and a base end side of the combustion space. A flame hole for disposing an air-fuel mixture having a smaller amount of air than the theoretical combustion air amount and having a high fuel concentration toward the combustion space; and a flame hole directed toward the tip opening side of the combustion space from the flame hole. An air ejection portion that is disposed so as to protrude and blows out secondary air from the protruding end portion, and a combustion gas generated from a flame hole flame formed in the flame hole portion is projected to the protruding end portion of the air ejection portion. Guidance means for guiding toward the vehicle. In addition, a flame holding member is disposed in the flame hole portion so as to oppose and cover the air-fuel mixture jet port from which the rich air-fuel mixture is jetted out.
[0012]
In the case of the first aspect of the invention, the flame flame formed by the combustion of the rich mixture injected from the mixture outlet is reliably held by the flame holding member, so that the rich mixture is extremely low. Even if the excess air ratio is set, the flame stoma can be stably maintained and maintained. Then, the combustion gas containing a large amount of unburned components generated from the flame flame is guided by the above-mentioned guide means and guided to the protruding end of the air jetting portion, and is mixed with the secondary air blown out from the protruding end. The unburned components are completely burned. As described above, even if the excess air ratio of the rich air-fuel mixture jetted from the flame hole is made extremely low to suppress the NOx generation amount, the two-stage combustion can be stably realized. In particular, by adopting a configuration in which a rich air-fuel mixture having an excess air ratio that is higher than the flammability limit and has an excess air ratio near the flammability limit is ejected from the flame hole portion (claim 2), Even when a low NOx is to be achieved, it is possible to stably maintain the flame of the flame hole and to reliably continue the two-stage combustion.
[0013]
The following various components can be adopted as a more specific configuration of the flame holding member employed above. First, as the flame holding member, a vortex is generated by colliding with the rich mixture jetted from the mixture jet, and a flame flame is formed by the vortex rich mixture. It has a configuration (claim 3). In this case, the turbulent vortex is generated in the wake area of the object when the object is placed in the fluid and collides with the object. The vortex of the air-fuel mixture stably holds the base of the flame. The flame holding member having such a configuration may be formed so as to have a collision wall surface that intersects with the jet flow of the rich mixture from the mixture jet port and an edge that generates a vortex. 4). That is, the jet flow colliding with the collision wall surface causes a vortex at the edge. The collision wall surface may be a wall surface orthogonal to the jet flow, a wall surface expanding in an inclined direction, or any wall surface that can make the flow of the jet flow non-streamlined.
[0014]
Secondly, the flame holding member is heated and glows red by being heated by contact with a combustion gas generated from a flame flame formed by the rich mixture blown out from the mixture gas outlet from the gas mixture spouting port. The flame holding of the hole flame is performed (claim 5). In this case, the flame stabilizing member is heated by contacting with the high-temperature combustion gas generated from the flame streaks and glows red, and this red hot state is maintained. And will be maintained. The flame holding member having such a configuration may be formed of a material having good heat conductivity and heat resistance, such as metal or ceramics, but the rich mixture ejected from the mixture ejection port passes therethrough. It is preferably formed of a porous member having continuous pores that can be formed (claim 6). In this case, while the flame stove flame is formed from the continuous fine hole outlet of the flame stabilizing member, the flame stabilizing member itself is heated by the combustion gas from the flame stoma flame and glows red. For example, a porous ceramic or a metal fiber entangled like a nonwoven fabric is applicable.
[0015]
According to the second aspect of the present invention, as a two-stage combustion device, a combustion space defined by a cylindrical inner surface having an open front end and a closed base end, and a stoichiometric air space disposed on the base end side of the combustion space and having a combustion amount A flame hole for burning an enriched air-fuel mixture having a smaller fuel concentration than the air amount toward the combustion space, and is disposed so as to protrude from the flame hole toward the front end opening side of the combustion space. An air ejection portion for blowing secondary air from the protruding end portion, and guide means for guiding a combustion gas generated from a flame hole flame formed in the flame hole portion toward the protruding end portion of the air ejection portion. Shall be provided. The flame hole is provided with a flame holding means having a wall surrounding the air-fuel mixture outlet from which the rich air-fuel mixture is ejected, and a concave portion at the tip of the wall to generate a vortex of the rich air-fuel mixture. (Claim 7).
[0016]
In the case of the second invention, the outer portion of the jet flow of the rich mixture from the gas mixture jet outlet flows along the wall portion, and is caught in the concave portion at the tip thereof to generate a vortex and to be decelerated. Become. Therefore, the base of the flame flame is stably maintained by the vortex of the rich mixture. Thereby, even if the rich mixture is set to an extremely low excess air ratio, it is possible to stably maintain and maintain the flame flame. Then, the combustion gas containing a large amount of unburned components generated from the flame flame is guided by the above-mentioned guide means and guided to the protruding end of the air jetting portion, and is mixed with the secondary air blown out from the protruding end. The unburned components are completely burned. As described above, even in the second aspect of the present invention, even if the excess air ratio of the rich air-fuel mixture ejected from the flame hole is made extremely low to suppress the NOx generation amount, the two-stage combustion is stably performed. It can be realized.
[0017]
According to the third aspect of the present invention, as a two-stage combustion device, a combustion space defined by a cylindrical inner surface having an open front end and a closed base end, and a theoretical combustion air disposed on the base end side of the combustion space. A flame hole for burning the rich mixture having a lower fuel concentration than the amount toward the combustion space, and disposed so as to protrude more toward the front end opening side of the combustion space than the flame hole. An air ejection portion for blowing secondary air from the projecting end portion, and guide means for inducing combustion gas generated from the flame hole flame formed in the flame hole portion toward the projecting end portion of the air ejection portion. It shall be assumed. An air supply port is disposed in the flame hole portion adjacent to the air-fuel mixture outlet from which the rich air-fuel mixture is blown out, and the air supply port is used as an air supply port for the jet of the rich air-fuel mixture from the air-fuel mixture air-outlet. A small amount of air is discharged and supplied to the vicinity of the outer surface (claim 8).
[0018]
In the case of the third aspect of the invention, at the air supply port, supplementary flame is formed while the air discharged and supplied from the air supply port and the outer surface of the jet flow of the rich mixture are diffused and mixed. . Then, this supplementary flame is formed as a stable flame while being supplied with air from the air supply port. For this reason, it becomes possible to maintain the flame hole flame of the flame hole portion in the flame holding state by this supplementary flame. Thereby, even if the rich mixture is set to an extremely low excess air ratio, it is possible to stably maintain and maintain the flame flame. Then, the combustion gas containing a large amount of unburned components generated from the flame flame is guided by the above-mentioned guide means and guided to the protruding end of the air jetting portion, and is mixed with the secondary air blown out from the protruding end. The unburned components are completely burned. As described above, even in the third aspect of the present invention, even if the excess air ratio of the rich air-fuel mixture jetted from the flame hole is made extremely low to suppress the NOx generation amount, the two-stage combustion can be stably performed. It can be realized.
[0019]
Such an air supply port in the third aspect of the invention can be disposed so as to surround the air-fuel mixture outlet (claim 9). In this case, since the supplementary flame is formed so as to surround the periphery of the base of the flame stove, the flame holding of the flame stoma can be more stably and surely maintained.
[0020]
Further, a rich mixture having an excess air ratio near the flammable limit is ejected from the air-fuel mixture outlet of the flame hole, and the amount of air discharged and supplied from the air supply port is ejected from the air-fuel mixture outlet. It can be set to a small amount of about 10% of the amount of air contained in the rich air-fuel mixture. In this case, the amount of air supplied and supplied from the air supply port is specified, and it is more reliable that the flame holding of the flame hole flame by the formation of the supplementary flame and the reduction of NOx as much as possible in the third aspect of the invention are more reliable. Will be realized.
[0021]
【The invention's effect】
As described above, according to the two-stage combustion apparatus according to any one of claims 1 to 6, the flame mixture formed in the flame hole portion by the rich mixture injected from the mixture injection port is maintained. The flame can be reliably held by the flame member. Therefore, even if the excess air ratio of the rich air-fuel mixture is set extremely low to suppress the NOx generation amount, the flame flame can be stably maintained and maintained. Step combustion can be realized.
[0022]
In particular, according to the second aspect, it is possible to reduce NOx as much as possible, and at the same time, to stably maintain the flame of the flame hole to reliably continue the two-stage combustion.
[0023]
According to the third aspect, the base of the flame hole flame can be stably maintained by the vortex of the rich mixture generated in the downstream region of the flame holding member. The flame holding member can be specified more specifically.
[0024]
According to the fifth aspect, the flame holding member can be glowed by radiant heat from the flame stove itself to maintain the glow state, and the flame stabilizing member in the red glow state can stably form and maintain the flame stoma. Can be done. According to the sixth aspect, a flame stove flame can be formed at the continuous pore outlet of the flame stabilizing member formed of a porous member, and the flame stabilizing member itself is heated by the flame stoma to heat the flame stabilizing member itself. can do.
[0025]
According to the two-stage combustion device of the seventh aspect, the rich air-fuel mixture ejected from the air-fuel mixture ejection port and flowing along the wall of the flame holding means is caught in the recess at the tip of the wall to generate a vortex. The vortex of the rich mixture can stably hold the base of the flame. As a result, even if the excess air ratio of the rich air-fuel mixture ejected from the flame hole is set to be extremely low so as to suppress the NOx generation amount to a low level, the flame flame is stably retained and the flame is stably retained. Stage combustion can be realized.
[0026]
According to the two-stage combustion chamber device according to any one of claims 8 to 10, a supplementary flame can be formed at the air supply port adjacent to the air-fuel mixture outlet from which the rich air-fuel mixture is jetted. The flame flame of the flame hole portion can be surely maintained in a flame holding state by the supplementary flame formed as (1). As a result, even if the rich mixture is set to an extremely low excess air ratio and the NOx generation amount is suppressed to a low level, it is possible to stably maintain the flame of the flame hole and stably realize the two-stage combustion. Will be able to
[0027]
In particular, according to the ninth aspect, the supplementary flame can be formed so as to surround the periphery of the base of the flame hole flame, and the flame holding of the flame hole flame can be more stably and surely maintained.
[0028]
According to the tenth aspect, the amount of air to be supplied and discharged from the air supply port is specified to more reliably realize both the flame holding of the flame flame by the formation of the supplementary flame and the reduction of NOx as much as possible. be able to.
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0030]
<First embodiment>
FIG. 1 shows a two-stage combustion device according to a first embodiment of the present invention. In FIG. 1, reference numeral 2 denotes a cylindrical body having a cylindrical inner surface 22 whose front end (upper end in the figure) is an opening 21 and a base end (lower end in the figure) is closed, and 3 is a cylindrical body of the cylindrical body 2. The combustion space 4 defined by the inner surface 22 is air protruding a predetermined amount from the central position near the central axis X of the combustion space 3 toward the tip opening 21 of the combustion space 3 at the base end position of the combustion space 3. The ejection portions 5a and 5b are at the base end of the combustion space 3 and are located outside the air ejection portion 4 so as to surround the air ejection portion 4, and 6 is the air ejection portion. A guiding wall as a guiding means protruding into the combustion space 3 from a cylindrical inner surface 22 at a position closer to the front opening 21 of the combustion space 3 than a front end portion (upper end in FIG. 1) of the combustion space 3. A heating target (not shown) is arranged above the distal end opening 21 in FIG. 1. For example, in the case of a water heater, heat for heat exchange heat of water passing therethrough is provided. An exchanger is provided for heating.
[0031]
Note that the two-stage combustion device can be configured in various cylindrical shapes such as a cylindrical shape or a rectangular cylindrical shape. In the case of a cylindrical shape, the cylindrical inner surface 22 is the cylindrical inner surface, and the central axis X is the center. On the axis, the air ejection portion 4 has a cylindrical shape in the central area, the flame holes 5a and 5b surround the air ejection portion 4 at an outer peripheral position, and the guide wall 6 has a donut plate shape and a square cylindrical shape. In the case of the above, the cylindrical inner surface 22 is located on the inner surface of the rectangular cylinder, the air ejection portion 4 is located at the center position in the width direction, the flame holes 5a and 5b are located on both outer positions across the same, and the guide wall 6 is located on both sides. In the form of an overhanging plate. Hereinafter, the two-stage combustion device will be described as having a cylindrical configuration.
[0032]
The combustion space 3 has a base end section defined by the flame holes 5 a and 5 b and the air ejection section 4, and an outer periphery section defined by the cylindrical inner surface 22. A narrow portion 7 is formed in the combustion space 3 by the inner edge 61 of the guide wall 6. The guide wall 6 is disposed so as to be opposed to the flame hole 5b at a position closer to the distal opening 21 of the combustion space 3 than the flame hole 5b at the base end side, while the opening position of the constricted portion 7 is set. The air jetting section 4 is disposed facing the air outlet.
[0033]
The air blow-out section 4 is configured to blow air into the combustion space 3 through the air blow-out ports 41, 41,... So as to blow out a combustion gas described later. Each of the air outlets 41 is opened toward the constricted portion 7 so that secondary air is blown out toward the distal end opening 21 toward a central region of the combustion space 3 near the central axis X.
[0034]
The flame holes 5a and 5b are supplied with a predetermined rich air-fuel mixture and ejected therefrom, so that primary combustion of the rich air-fuel mixture in the flame holes 5a and 5b causes incomplete combustion flame in an air-deficient state. The flames 51, 51,... Are formed. The flame hole portion 5a is disposed at a position facing the air ejection portion 4 side (inner peripheral side) on the cylindrical inner surface 22 that defines the outer peripheral side of the base end of the combustion space 3. Is disposed at a position facing the distal end opening 21 side of the combustion space 3 on the base end side of the combustion space 3.
[0035]
The rich mixture is a rich fuel mixture having a high fuel concentration and an excess air ratio of less than 1.0 (100%), and the excess air ratio is defined as the excess air ratio at the flammable limit of the fuel gas. It is desirable to use an rich mixture set to a value close to (for example, 0.6 to 0.7). For example, if the fuel gas is methane gas, the excess air ratio at the flammable limit of 0.63 is in the range of 0.64 to 0.70 or in the range of ± 0.05 with 0.70 interposed therebetween, preferably about 0.65. Rich mixture having an excess air ratio of
[0036]
In addition, an injection port 23 is opened at one or both side positions (one side position is illustrated in FIG. 1) near the base position of the combustion space 3 near the root position of the guide wall 6 and on the front end opening 21 side or the base end side. The air supplied from behind each of the outlets 23 along the back of the cylindrical inner surface 22 is blown toward the inside of the combustion space 3 along the guide wall 6.
[0037]
In addition to the above configuration, the flame holes 5a and 5b are opposed to the air-fuel mixture outlets 51 constituting the flame hole 5b as shown in FIG. The flame holding member 8 is disposed so as to cover the mixture jet 51. Each of the flame-holding members 8 is formed of a plate-shaped member having a V-shaped cross section, and the collision wall surfaces 81, on which the jet flow of the rich mixture impinges on both sides of the lower point 80, 81, and edges 82, 82 at both ends. Then, after the jet flow of the rich mixture collides with each of the collision wall surfaces 81 and forcibly changes its direction, a part is caught at each edge 82 to generate a vortex 521, and this turbulent vortex state The flame hole flame 52 (see FIG. 1) is formed based on the swirl 521 region of FIG. In FIG. 1, the illustration of the flame holding member 8 for the flame hole 5a is omitted, but the same flame holding member 8 as that shown in FIG. 2 is provided.
[0038]
As a preferable arrangement state of each of the flame holding members 8, assuming that the width of each air-fuel mixture outlet 51 is P and the distance from each air-fuel mixture outlet 51 is H, a V-shaped H is 0 or more and 4P. It should be in the following range. This takes into account that when the gas is ejected from the ejection port, the region that the ejection energy reaches is up to a distance several times the diameter of the ejection port. Further, the inclination angle α of each of the collision wall surfaces 81 is set in a range of 0 ° to 45 ° with respect to the direction of the jet flow (vertical direction in FIG. 2). That is, it may be V-shaped or perpendicular to the jet flow.
[0039]
3A and 3B show various aspects of the relationship between the air outlet 51 and the flame holding member 8 in the flame hole 5b. FIG. 3A shows the case of the slit-shaped air outlet 51, and FIG. 3 (c) shows the case of the flame holding member 8 in which the hole-shaped air ejection ports 51, 51,... Are arranged in an arc shape and curved in an arc shape. ing. These may be appropriately selected according to the overall shape of the two-stage combustion device and the like.
[0040]
In the case of the first embodiment, the rich mixture is swirled by the flame holding member 8, and the base of the flame hole flame 52 is formed by the rich mixture of the turbulent vortex. 8 can be stably held. For this reason, even if the rich mixture injected from the flame holes 5a and 5b is set extremely low to the excess air ratio near the flammable limit, the combustion state of the flame 52 formed by the rich mixture is stabilized. And thus NOx can be reduced as much as possible. The combustion gas (see the dashed line arrow in FIG. 1) containing a large amount of unburned components generated from the flame 52 is guided by the guide wall 6 and flows toward the constricted portion 7, that is, toward the tip end of the air ejection portion 4. Secondary air is blown out of the flowing combustion gas from each of the air injection ports 41 of the air injection section 4 and mixed with the secondary air to completely burn unburned components in the combustion gas (secondary combustion). Will be. At this time, a part of the combustion gas flowing along the cylindrical inner surface 22 and the guide wall 6 is completely burned by the secondary air blown out from the injection port 23, and thus, the combustion gas is not completely burned and the tip opening is kept as it is. Flow to the side 21 is reliably prevented. At the same time, the wall exposed on the combustion space 3 of the guide wall 6 can be cooled by the secondary air ejected from the ejection port 23.
[0041]
In addition, supplementing the function of the guide wall 6 at the time of the two-stage combustion, the guide wall 6 covers the tip opening 21 side of the flame holes 5a and 5b, so that the extension of the flame hole flame 52 is suppressed, Only the combustion gas can be guided to the tip of the air ejection section 4, and the secondary air from the air ejection section 4 can be ejected only to the combustion gas. That is, the guide wall 6 has a function of separating and blocking the direct contact between the secondary air from the air ejection part 4 and the flame stove flame 52, and the function of separating the flow of the combustion gas generated from the flame stoma 52 into the air ejection part. And a function of inducing the secondary air blown from 4 to cross. The separation / shutoff function reliably prevents the increase in NOx caused by the secondary air coming into direct contact with the flame 52, and reduces the NOx as much as possible based on the setting of the excess air ratio of the rich mixture. NOx conversion can be realized. In addition, the above-described guiding function is combined with the fact that secondary air is blown out from each air outlet 41 through the opening of the constricted portion 7 toward the front end opening 21 side of the combustion space 3, and the combustion gas is discharged. The secondary air penetrates and is supplied to the inside of the combustion gas while suppressing the turbulence of the gas, so that the mixing of the combustion gas and the secondary air can be promoted.
[0042]
In addition, as another form of the flame holding member 8 of the first embodiment, as shown in FIG. 4A, a collision wall surface orthogonal to the jet flow of the rich mixture from each of the hole-shaped mixture jets 51. The flame-holding member 8a may be formed such that a portion between the two adjacent gas mixture outlets 51, 51 is notched, or a part is inserted into the gas mixture outlet 51 to divide the jet flow. The flame holding member 8b integrally having the inserted piece 83 as described above may be used.
[0043]
<Second embodiment>
FIG. 5 shows a two-stage combustion device according to a second embodiment of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.
[0044]
In the second embodiment, the flame holding member 9 is disposed so as to cover the combustion space 3 side of each of the air-fuel mixture outlets 51 constituting the flame hole 5b. As shown in detail in FIG. 6, the flame holding member 9 is made of a porous ceramic (porous member) having a large number of continuous pores and having a predetermined thickness. Heated by the high-temperature combustion gas generated from the fuel gas 52, the gas becomes a red-hot body and holds the flame 52. Although FIG. 5 shows a state in which the flame holding member 9 is not provided in the flame hole 5a, the flame holding member 9 on the side of the flame hole 5b emits red light to the flame hole 5a. Therefore, the flame holding member 9 may or may not be provided.
[0045]
It is preferable that the interval S between the flame holding member 9 and each of the air-fuel mixture jet ports 51 is zero or as small as possible so as not to be too large. Assuming that the width or diameter of each air-fuel mixture ejection port 51 is L, for example, the air-fuel mixture outlet 51 may be limited to a range of 0 <S <L. If the interval S is too large, the rich mixture flows into the gap and then passes through the flame holding member 9, so that the velocity distribution of the rich mixture after the passage is flattened, and each flame is flattened. The hole flames 52 are not individual flames but are connected at the base of each other. As a result, the area of the flame holding member 9 exposed to the combustion gas is reduced, the heat reception from the combustion gas is reduced, and the red heat effect is reduced. As a result, the flame holding effect is also reduced. Further, the thickness T of the flame holding member 9 may be set in the range of 0 <T <3L in relation to the width or the diameter L of the mixing jet 51. If the thickness T is excessively increased, the velocity distribution of the rich mixture is flattened with the jet flow from each mixture jet when passing through the flame holding member 9, and the above-mentioned interval S is too large. As in the case, the flame holding effect is reduced.
[0046]
In the case of the second embodiment, the rich mixture ejected from each mixture ejection port 51 passes through the continuous pores of the flame holding member 9 as it is, and forms a flame 52 on the upper surface thereof. A region where the rich mixture passes to form the flame 52 is referred to as a passage region 91, and a region where the flame 52 is not formed and is exposed to the combustion space 3 is referred to as a non-passage region 92. The non-passage area 92 is exposed to the high-temperature combustion gas generated from the flame 52 and is heated to a high temperature and glows red. On the other hand, the passage area 91 continues to pass the jet flow of the low-temperature rich mixture. Although it receives radiant heat from the flame 52, it is not heated so much and is advantageous in heat resistance. Then, since the non-passage area 92 is in a red-hot state, the flame 52 is maintained, and this state is maintained.
[0047]
For this reason, even if the rich air-fuel mixture ejected from the flame holes 5a and 5b is set very low to the excess air ratio near the flammable limit similarly to the first embodiment, the flame air-fuel mixture formed by the rich air-fuel mixture is used. The combustion state of the flame 52 can be stably maintained, and as a result, NOx can be reduced as much as possible.
[0048]
<Third embodiment>
FIG. 7 shows a two-stage combustion device according to a third embodiment of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.
[0049]
In the third embodiment, each air-fuel mixture outlet 51 is formed such that the cross-sectional area of the flow path is larger than that of each air-fuel mixture outlet 51 with respect to the combustion space 3 side of each air-fuel mixture outlet 51 constituting the flame hole 5b. Is provided with a projecting wall portion 10 surrounding the wall. If each air-fuel mixture outlet 51 is a hole having a diameter L (see FIG. 8), the projecting wall portion 10 may be formed in a cylindrical shape having an inner diameter D (L <D). Is a slit having a width L, the protruding wall portion 10 may be constituted by groove-shaped side walls having an inner width D (L <D).
[0050]
In the case of the third embodiment, when the rich air-fuel mixture is jetted from each air-fuel mixture outlet 51 toward the combustion space 3, the flow path cross-sectional area of each air-fuel mixture jet 51 is rapidly expanded by the projecting wall portion 10. Therefore, a vortex is generated in the protruding wall portion 10, and the flame hole flame 52 extends to the combustion space 3 in a state where the flame base is held by the vortex. Moreover, since the protruding wall portion 10 protrudes into the combustion space 3, the protruding wall portion 10 is heated by being exposed to the high-temperature combustion gas generated from the flame hole flame 52, and is swirled in the heated protruding wall portion 10 by the swirling flow. The combustion speed at the flame base of 52 is increased, and the flame holding action is further enhanced.
[0051]
<Fourth embodiment>
FIG. 9 shows a two-stage combustion device according to a fourth embodiment of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.
[0052]
In the fourth embodiment, as shown in FIG. 10, each air-fuel mixture ejection port 51 of the flame hole 5b is formed by a wall 11 surrounding the same, and a recess 12 is formed behind the wall 11. If each gas mixture ejection port 51 has a hole shape, the wall portion 11 is formed in a tubular shape, and the concave portion 12 is arranged in a donut shape. The concave portions 12 are formed on both outer sides. The wall portion 11 and the concave portion 12 constitute a flame holding means.
[0053]
In the case of the fourth embodiment, when the rich air-fuel mixture is jetted from each air-fuel mixture outlet 51 toward the combustion space 3, the outer part of the jet flow is applied to the wall portion 11 constituting each air-fuel mixture jet 51. When the air flows along the air-fuel mixture jet port 51 at the tip, it is caught in the concave portion 12 to generate a vortex, which is decelerated. Then, the flame base is stably formed by the swirling portion, and the flame 52 is held.
[0054]
<Fifth embodiment>
FIG. 11 shows a two-stage combustion device according to a fifth embodiment of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.
[0055]
In the fifth embodiment, an air supply pipe 13 is provided adjacent to each of the air-fuel mixture outlets 51 of the flame hole portion 5b, and a tip of the air-supply / supply pipe 13 protruding from the above-described air-fuel mixture outlet 51 by a predetermined amount. The opening opens the air supply port 14 facing the combustion space 3 (see also FIG. 12). Further, as shown in FIG. 13, a plurality of the air supply ports 14 are provided around the air / fuel mixture ejection ports 51 so as to surround the respective air / fuel mixture ejection ports 51. A small amount of air supplied from each air supply port 14 through the air supply pipe 13 is discharged and supplied to the vicinity of the outer surface of the jet flow of the rich mixture from each mixture gas outlet 51. .
[0056]
While the rich mixture similar to that described in the first embodiment is ejected from the flame hole portion 5b, each air supply port 14 emits a mixture of about 10% of the amount of air contained in the rich mixture. It is set so that a small amount of air is discharged and supplied, whereby the excess air ratio when combining the rich mixture from the mixture jet 51 and the air from the air supply port 14 is 0.70. It is set so as to be in the range of plus / minus 0.05. For example, when methane is used as the fuel gas, the excess air ratio of the rich mixture is set to 0.60 to 0.65, and an air amount of 10% of the air amount is discharged and supplied from the air supply port 14. To make it work.
[0057]
In the case of the fifth embodiment, the air from the air supply port 14 and the rich air-fuel mixture on the outer side of the jet flow from the air-fuel mixture outlet 51 are diffused and mixed. A flame 15 (see FIG. 12) is formed, and the flame 52 is held in a stable combustion state by being surrounded by the supplementary flame 15. For this reason, even if the excess air ratio of the rich mixture is set to a value close to the flammability limit, the flame 52 can be surely maintained and the NOx can be reduced as much as possible. .
[0058]
FIG. 14 shows another embodiment configured using the same principle as that of the fifth embodiment. In this case, a concave portion 16 opened only on the combustion space 3 side between an air-fuel mixture outlet 51 and an air supply port 14 is provided. Has formed. In this case, the inside of the concave portion 16 tends to have a negative pressure due to the ejection of the rich mixture from the mixture-air outlet 51 and the discharge of the air from the air supply port 14. A part of the air-fuel mixture is drawn into the concave portion 16 to generate a vortex. For this reason, in addition to the formation of the supplementary flame 15, the flame stabilization of the flame hole flame 52 is achieved by the eddy current.
[0059]
<Other embodiments>
It should be noted that the present invention is not limited to the above embodiments, but encompasses various other embodiments. In other words, in each of the above embodiments, the guide wall 6 is used as the guide means, but instead of the guide wall 6, a flame for guidance may be formed separately. That is, a jet port is provided on the inner surface of the cylinder substantially at the same position as the guide wall 6, and the air-fuel mixture, for example, the same as the rich air-fuel mixture from the flame hole is directed from the jet port toward the tip end side of the air jetting section 4. The fuel gas is jetted out, thereby forming an induction flame for guiding the combustion gas generated from the flame hole flame at the flame hole portion to the tip end side. Guidance means is constituted by such an induction flame.
[0060]
Further, instead of the above-described guide wall 6, the inner surface of the cylinder may have a shape whose inner cross section is gradually reduced so as to form a stenosis portion at a position in front of the distal end portion of the air ejection portion 4. In this case, such a cylindrical inner surface constitutes the guiding means.
[Brief description of the drawings]
FIG. 1 is an explanatory end view showing a first embodiment of the present invention.
FIG. 2 is an enlarged view of the flame holding member of FIG. 1;
FIGS. 3A and 3B are partial perspective views of various forms of the air-fuel mixture outlet and the flame holding member of FIG. 1; FIG. 3A shows a case where the air-fuel mixture outlet is slit-shaped; FIG. In the case of a hole, FIG. 3 (c) shows a case where the air-fuel mixture ejection ports are arranged in an arc shape.
4A and 4B show another embodiment of the flame holding member of FIG. 1; FIG. 4A is a partial perspective view in a case where the flame is orthogonal to a jet flow, and FIG. The end views are respectively shown.
FIG. 5 is an end view illustrating a two-stage combustion device according to a second embodiment.
FIG. 6 is a partially enlarged view of the flame holding member of FIG. 5;
FIG. 7 is an end view illustrating a two-stage combustion device according to a third embodiment.
FIG. 8 is a partially enlarged view of FIG. 7;
FIG. 9 is an end view illustrating a two-stage combustion device according to a fourth embodiment.
FIG. 10 is a partially enlarged view of FIG. 9;
FIG. 11 is an explanatory end view showing a two-stage combustion device according to a fifth embodiment.
FIG. 12 is a partially enlarged sectional view of FIG. 11;
FIG. 13 is an enlarged view taken on line AA of FIG. 11;
FIG. 14 is a partially enlarged end view showing another mode belonging to the fifth embodiment.
FIG. 15 is a diagram showing the relationship between the excess air ratio of the primary air-fuel mixture and the NOx concentration and the overall excess air ratio.
[Explanation of symbols]
3 combustion space
4 Air ejection section
5a, 5b Flame hole
6 guide wall (guide means)
8, 8a, 8b flame holding member
9 Flame holding member (porous member)
10 Protrusions (walls)
11 Wall
12 recess
14 Air supply port
15 Supplementary flame
22 cylindrical inner surface
52 Flame Flame
81 Collision Wall
82 Edge

Claims (10)

A combustion space defined by a cylindrical inner surface having an open end and a closed base end, and an over-mixed mixture provided at the base end side of the combustion space and having an air amount smaller than the theoretical combustion air amount and a high fuel concentration. A flame hole for burning air toward the combustion space, and air that is disposed so as to protrude from the flame hole toward the front end opening side of the combustion space and blows out secondary air from the protruding end. A two-stage combustion device comprising: an ejection portion, and a guide means for guiding a combustion gas generated from a flame hole flame formed in the flame hole portion toward a protruding end of the air ejection portion,
A two-stage combustion device, characterized in that a flame holding member is disposed in the flame hole so as to face and cover an air-fuel mixture outlet from which an rich mixture is injected. The two-stage combustion device according to claim 1,
A two-stage combustion device configured to eject a rich mixture having an excess air ratio that is higher than the flammability limit and near the flammability limit from the flame hole. The two-stage combustion device according to claim 1 or claim 2,
The flame stabilizing member is configured to generate a vortex by colliding with the rich mixture ejected from the mixture outlet, and a flame flame is formed by the vortex rich mixture. There is a two-stage combustion device. The two-stage combustion device according to claim 3, wherein
The two-stage combustion device, wherein the flame holding member is formed to have a collision wall surface that intersects the jet flow of the rich mixture from the mixture jet port and an edge that generates a vortex. The two-stage combustion device according to claim 1 or claim 2,
The flame stabilizing member is heated and glows red by contact with a combustion gas generated from a flame streak formed by the rich mixture ejected from the mixture bubbling port. A two-stage combustion device that is configured to: The two-stage combustion device according to claim 5, wherein
The two-stage combustion device, wherein the flame holding member is formed of a porous member having continuous pores through which the rich air-fuel mixture ejected from the air-fuel mixture outlet can pass. A combustion space defined by a cylindrical inner surface having an open end and a closed base end, and an over-mixed mixture provided at the base end side of the combustion space and having an air amount smaller than the theoretical combustion air amount and a high fuel concentration. A flame hole for burning air toward the combustion space, and air that is disposed so as to protrude from the flame hole toward the front end opening side of the combustion space and blows out secondary air from the protruding end. A two-stage combustion device comprising: an ejection portion, and a guide means for guiding a combustion gas generated from a flame hole flame formed in the flame hole portion toward a protruding end of the air ejection portion,
The flame hole is provided with a flame holding means having a wall surrounding an air-fuel mixture jet outlet from which the rich air-fuel mixture is jetted, and a concave portion at a tip of the wall to generate a vortex of the rich air-fuel mixture. A two-stage combustion device. A combustion space defined by a cylindrical inner surface having an open end and a closed base end, and an over-mixed mixture provided at the base end side of the combustion space and having an air amount smaller than the theoretical combustion air amount and a high fuel concentration. A flame hole for burning air toward the combustion space, and air that is disposed so as to protrude from the flame hole toward the front end opening side of the combustion space and blows out secondary air from the protruding end. A two-stage combustion device comprising: an ejection portion, and a guide means for guiding a combustion gas generated from a flame hole flame formed in the flame hole portion toward a protruding end of the air ejection portion,
An air supply port is disposed in the flame hole portion adjacent to a mixture jet from which the rich mixture is ejected,
The two-stage combustion device, wherein the air supply port is configured to discharge and supply a small amount of air to the vicinity of the outer surface of the jet flow of the rich mixture from the mixture jet. The two-stage combustion device according to claim 8, wherein
The two-stage combustion device, wherein the air supply port is provided so as to surround a periphery of the mixture jet. The two-stage combustion device according to claim 8 or 9, wherein:
The flame hole is configured such that a rich mixture having an excess air ratio near the flammable limit is ejected from the mixture ejection port,
A two-stage combustion apparatus, wherein the amount of air discharged and supplied from the air supply port is set to a small amount of about 10% of the amount of air contained in the rich mixture ejected from the mixture outlet.

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