JPH05231621A - Nitrogen oxide low generation burner - Google Patents

Abstract

(57) [Summary] [Purpose] In a small-scale combustion device for household use, small-scale business use, etc., it is possible to obtain a large combustion amount by increasing the packing density of burners, and at the same time, a fuel-lean mixture. Nitrogen oxides and noise will be reduced by ensuring stable combustion. [Structure] A vertical flat burner body is provided with a flame hole portion on the upper side, and fuel gas and air introduction portions 4a, 4b are formed on the lower side of the burner body, and a mixing pipe portion from the introduction portion to the flame hole portion is constructed. A plurality of the first and second burner units are alternately arranged in a row, and the first burner unit has the introduction portion located below the introduction portion of the second burner unit and has a large diameter. It is configured so that a larger amount of fuel gas and air can be introduced, and the fuel gas ejection portions are arranged corresponding to the respective introduction portions of the first and second burner units. Then, in the flame hole portion of the second burner unit, in order to ignite and detect the flame, and in order to perform them smoothly, the flame holding portion of the second burner unit has a flame holding flame. Is configured to form a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-nitrogen-oxide generating burner used in a small-sized combustion apparatus for household use, small-sized business use, or the like.

[0002]

2. Description of the Related Art Nitrogen oxides (NOx) in the combustion gas of burners in various combustion devices are not only toxic in themselves, but are also considered to be one of the causes of acid rain and photochemical smog. The burner used in the equipment has this NO
Various measures have been developed and taken to reduce the generation amount of x.

[0003]

However, these measures have hitherto been mainly applied to large-scale combustion devices for industrial use, etc., which are legally regulated. Since the combustion device has a problem such as noise, it cannot be said that sufficient measures are taken.

That is, in a large-scale combustion apparatus, since the static pressure of the combustion fan can be made large, it is easy to control the flow of combustion gas and air, there is a high degree of freedom in the layout of the burner, and noise countermeasures are also taken. Due to advantages such as being easy,
Since the conditions for noise countermeasures are not strict and the combustion chamber can be large, there is an advantage that even if a so-called slow combustion NOx reduction measure is taken, it is easy to completely burn the fuel. A combustion device configured to obtain a large combustion amount does not have these advantages, and it is difficult to take NOx reduction measures as compared with a large combustion device. An object of the present invention is to increase the packing density of burners to obtain a large combustion amount, and to stably perform combustion with a lean fuel-air mixture to reduce nitrogen oxides and noise. This is intended to be achieved.

[0005]

Means for solving the above-mentioned problems will be described with reference to the drawings corresponding to the embodiments. A low-nitrogen-oxide generating burner of the present invention is a vertical flat burner unit. A plurality of first and second burner units each having a flame hole portion in the upper part of the body, a fuel gas and air introduction part in the lower lateral side, and a mixing pipe part extending from the introduction part to the flame hole part are provided. The first burner unit is configured by alternately arranging the above-mentioned introduction portion below the introduction portion of the second burner unit and has a large diameter so that a larger amount of fuel gas and air can be generated. In addition to enabling introduction, a fuel gas jetting portion is arranged corresponding to each introduction portion of these first and second burner units, and the first burner unit is fuel-lean,
In addition, the second burner unit is configured to supply the air-fuel mixture whose fuel gas amount is larger than that supplied to the second burner unit and to supply the fuel-rich air-fuel mixture to the second burner unit. It is configured such that ignition is performed in the flame hole portion. Further, the present invention is configured to detect a flame in the flame hole portion of the second burner unit. Further, the present invention is configured such that a flame holding flame is formed in the second burner unit. Further, the present invention is
The burner body comprises an upper portion having a smaller thickness and a lower portion having a larger thickness, a flame hole portion is configured at an upper end of the upper portion, and an introduction portion and a mixing pipe portion are configured at a lower portion. The lower part of the second burner unit is made to correspond to the upper part of the burner unit.

[0007]

In the first burner unit, the introduction parts of the fuel gas and the air are located below the introduction parts of the second burner unit, and these introduction parts are configured in high and low stages. These first and second burner units can be arranged in high density by alternately arranging them. At this time, the upper portion forming the flame hole portion of the first burner unit is made thinner than the lower portion forming the introducing portion and the mixing pipe portion, and the second burner is formed on the adjacent upper portion thereof. If the lower parts of the units are made to correspond to each other, a higher density of rows can be provided.

Further, because of the above construction, the distance from the introduction portion of the first burner unit to the flame hole portion is longer than that of the second burner unit, and the mixing of fuel gas and air is performed well. .. Therefore, in the first burner unit, a large amount of air-fuel mixture in which the fuel is lean and uniformly mixed can be supplied to the flame hole portion.

In the above structure, the fuel-lean mixture is ejected from the flame hole of the first burner unit and burns, and the fuel-rich mixture is ejected from the flame hole of the second burner unit. And burn.

Combustion of excess air by a fuel-lean mixture has poor flame stability by itself, but since there is a stable flame due to the above-mentioned rich fuel mixture adjacent to these flames. , These stable flames act as a pilot flame to stabilize the excess air flame. Thus, the flame obtained in the second burner unit is
Since the mixture is rich in fuel, the flame itself is stable, but the stability of the flame is further improved by forming a flame-holding flame in the second burner unit, and it is possible to improve the stability of adjacent flames. It is possible to further stabilize the flame due to air. Therefore, the lift of the flame and the oscillatory combustion do not occur, and the generation of noise is suppressed.

Since the combustion of the fuel-lean mixture, which is stabilized by the flame of the fuel-rich mixture as described above, is combustion of excess air, the temperature of the flame is kept low by the cooling action of the excess air. The generation of NOx is reduced. In addition, the amount of fuel gas used for combustion as a fuel-lean mixture is
Since the amount of fuel gas is greater than the amount of fuel gas supplied as a rich fuel-air mixture, the amount of NOx generated is small with respect to the combustion amount of the entire burner.

Further, the ignition of the fuel gas at the ignition plug or the like due to the high-pressure discharge ejects a fuel-rich mixture.
By igniting the burner unit of the above, reliable ignition can be performed, and the detection of the flame by the electrodes using the conductive action and rectifying action of the flame is also performed by the stable flame with the rich fuel mixture. The safety can be further improved. In addition, the flame formed in the second burner unit is held by the flame for holding flame, so that the flame is further stabilized, and the ignition and detection described above are performed reliably.

[0013]

Embodiment Next, an embodiment of the present invention will be described with reference to the drawings. 1 and 4 are perspective views showing examples of the first and second burner units 1a and 1b in the present invention, respectively. Each of the first and second burner units 1a and 1b has a flame hole 3 at the upper portion of the vertical flat burner body 2a or 2b.
a, 3b, fuel gas and air inlets 4a on the lower lateral side,
4b, and the flame holes 3a, 3 from the introduction portions 4a, 4b.
The mixing pipes 5a and 5b leading to b are constructed. The first burner unit 1a has the burner body 2a.
The vertical width of the burner unit 2b of the second burner unit 1b
Wider than the upper and lower width of the flame hole 3 from the introduction portion 4a
The distance to a is set longer than that of the second burner unit 1b. The second burner unit 1b is provided with a flame holding air-fuel mixture outlet hole 24 so that the sleeve fire forming plate 1 can be formed.
A flame holding flame 19c is formed in the zero portion. Further, as shown in FIG. 5, the second burner unit 1b has a high-voltage connector.
An ignition device 20 including a window 21 is provided and a detection code is provided.
The flame detection device 22 equipped with a switch is installed.

The first and second burner units 1a, 1
The burner units 2a and 2b of b are the upper part u having a small thickness.
And a thick lower portion d, flame holes 3a and 3b are formed at the upper end of the upper portion u, and the introduction portion 4 is formed in the lower portion d.
a, 4b and the mixing pipe parts 5a, 5b. The flame hole portions 3a and 3b are configured as a plurality of short slit-shaped opening portions arranged in a line by narrowing the long slit-shaped opening portions 6a and 6b at the upper end of the upper portion u at predetermined intervals. In addition, the flame hole portions 3a and 3b may have an appropriate configuration such as a configuration in which a plurality of transverse slits are arranged in a row.

The introduction portions 4a and 4b are formed as openings which are open to one end of the lower portion d, and throat portions 7a and 7b are formed inside the openings. Then, from the throat portions 7a, 7b toward the other end of the lower portion d,
Mixing pipe portions 5a and 5b that are folded back and reach the lower end of the upper portion u
Are configured. The introduction section 4a and the mixing tube section 5b of the first burner unit 1a are configured to have a larger diameter than those of the second burner 1b, and a larger amount of fuel gas and air can be introduced.

On the other hand, the first and second burner units 1a,
1b is an upper portion u, and a narrowed portion 8 across the upper portion u.
a and 8b are formed, and the first burner unit 1
On the upstream side of the narrowed portion 8a, a narrowed portions 9 are formed at predetermined intervals to form a rectifying portion. Although not shown in FIG. 4, a sleeve fire forming plate 10 is provided outside the upper portion u of the second burner unit 1b as shown in FIG. Corresponding to the above, the flame holding mixture air outflow hole 24 is provided in the upper portion u, and the flame holding flame 19c is formed in this portion.

5 to 8 show the construction of the burner constituted by the above-mentioned first and second burner units 1a and 1b, and FIG. 5 shows the entire construction with a part of the similar construction omitted. A plan view, FIG. 6 is an overall front view showing an air chamber 11 and a part of the first and second nozzle holders 12a and 12b, which will be described later, and FIG. 7 is an enlarged view of a main part of FIG. FIG. 8 is an enlarged front view of an essential part showing a state, and FIG. 8 is a side view.

As shown in these figures, the burner of the present invention has a large number of the above-mentioned first and second burner units 1a, 1b and their flame hole portions 3a, 3b at the same height or a slight height difference. Support boxes 13 in a state where they are alternately arranged in a row.
It is configured to support. In the embodiment, as shown in FIGS. 6 and 7, the height of the flame hole portion 3a of the first burner unit 1a is made slightly lower than the height of the flame hole portion 3b of the second burner unit 1b, and the sleeve It is installed at a height substantially equal to the upper end of the fire forming plate 10. Further, as is apparent from FIGS. 5 and 6, the second burner unit 1b is located on both ends of the burner.

As described above, the first burner unit 1a
Is configured such that the vertical width of the burner body 2a is wider than the vertical width of the burner body 2b of the second burner unit 1b. Therefore, as shown in FIG. 6, FIG. 7 and FIG. The introduction part 4a of the unit 1a is the second burner unit 1b.
Are arranged side by side in a row below the introduction portion 4b. Since the introduction portions 4b of the second burner unit 1b are aligned in a horizontal line between the upper portions u of the burner units 2a of the first burner unit 1a, the first burner unit 1a is
Despite having the large-diameter introducing section 4a and the mixing tube section 5a, the first and second burner units 1a and 1b can be installed with a narrow gap between the adjacent upper members u. Therefore, these first and second burner units 1
The a and 1b can be mounted in high density in a line.

The support box 13 has nozzle holders 12a, 1 in two upper and lower stages corresponding to the upper and lower rows of the introduction portions 4a, 4b of the first and second burner units 1a, 1b.
2b, that is, the lower first nozzle holder 12a and the second burner unit 1 corresponding to the first burner unit 1a.
The second upper nozzle holder 12b corresponding to b is installed. These nozzle holders 12a,
12b is installed in an air chamber 11 having an opening on the front side, and air is supplied from a fan 14 into this air chamber 11.

The first and second nozzle holders 12a and 12b are provided with nozzles 15a and 15b for ejecting fuel gas corresponding to the introduction portions 4a and 4b, respectively. The diameters and positions of the nozzles 15a and 15b, the opening diameters of the introduction portions 4a and 4b, and the like are set so as to satisfy the following conditions. That is, these constituent elements corresponding to the first burner unit 1a supply to the flame hole portion 3a an air-fuel mixture that is lean in fuel and has a larger amount of fuel gas than the supply amount to the second burner unit 1b. The conditions are set to satisfy the conditions, and the above-described constituent elements corresponding to the second burner unit 1b are set to satisfy the conditions for supplying the fuel-rich mixture to the flame hole portion 3b. For example, the flame hole portion 3 of the first and second burner units 1a, 1b
The air ratio of the air-fuel mixture supplied to a and 3b is the theoretical air amount λ = 1.
Then, it is possible to set λ≈1.2 to 1.5 and λ≈0.4, respectively. In addition, each flame hole 3a,
The ratio of the amount of fuel gas supplied to 3b is, for example, the first burner unit 1a: the second burner unit 1b = 8: 2.
It can be set to be about 6: 4. However, the air ratio and the fuel gas amount ratio of each of these can be appropriately determined beyond these ranges.

Next, FIG. 9 shows a state of the portion related to the nozzle holder as viewed from the back side of the nozzle,
FIG. 10 shows a state as viewed from the side surface side, and the first and second nozzle holders 12a and 12b are both provided with a partition plate 16
a, 16b divides the left, right, and middle three parts l, r, and m, and these parts are respectively connected to the communication pipes 17l, 17b.
r, 17m, and fuel gas supply pipe 1 for each
8l, 18r and 18m are provided. As can be seen from the arrangement of the nozzles 15a and 15b in these drawings, the second burner unit 1b is provided on both ends of the burner of the present invention which is formed by arranging a large number of burner units 1a and 1b. It is located. And the second nozzle holder 1
The second burner unit 1b corresponding to the nozzles 15b on both ends of the intermediate portion m of the second nozzle 2b has the first nozzle holder 12
a corresponding to the nozzles 15a on both ends of the intermediate portion m of a
The burner unit 1a is configured to be adjacent to the outside.

In the burner of the present invention having the above structure, first, the fuel gas is supplied to all the fuel gas supply pipes 18l, 18r, 18m, and the first and second fuel gas supply pipes 18l, 17r, 17m are provided. Fuel gas is supplied to the nozzle holders 12a and 12b, and air is supplied from the fan 14 into the air chamber 11 for combustion.

The first and second nozzle holders 12a, 12
The fuel gas supplied to b is supplied to the nozzles 15a and 15b, respectively.
Introducing part 4 of corresponding burner unit 1a, 1b from b
It is ejected in the a and 4b directions and is introduced into the burner units 2a and 2b while sucking the surrounding air by the ejected energy. In this way, from the introduction parts 4a, 4b to the burner body 2a,
The fuel gas and air introduced into 2b move through the mixing pipe portions 5a and 5b while mixing, and reach the respective flame hole portions 3a and 3b, from which they are ejected as a mixture gas for combustion. At this time, as described above, the fuel-lean air-fuel mixture is jetted from the flame hole portion 3a of the first burner unit 1a, and
Of the burner unit 1b of the first burner unit 1b ejects a rich fuel-air mixture, and the amount of the fuel gas in the mixture of gas ejected from the flame hole 3a of the first burner unit 1a is equal to that of the second burner unit 1b. Is larger than the amount of fuel gas in the air-fuel mixture ejected from the flame hole portion 3b.

By the supply of the air-fuel mixture as described above, a flame (first flame 19a) is formed above the flame hole portion 3a of the first burner unit 1a by the combustion of the fuel-lean air-fuel mixture, and Above the flame hole portion 3b of the second burner unit 1b, a flame (second flame 1
9b) is formed. At this time, the second burner unit 1
Since b is located at both ends of the burner, the first flame 1
The second flame 19b always exists on both sides of 9a. Further, a flame holding flame 19c is formed on the second burner unit 1b.

Since the first flame 19a is due to the combustion of a fuel-lean mixture, the stability is poor by itself, but the second flames 19b located on both sides thereof are due to the combustion of a fuel-rich mixture. Therefore, it is stable, and the stable second flame 19b acts as a pilot flame to stabilize the first flame 19a. Further, the second flame 1
Since 9b is flame-held from its surroundings by the flame-holding flame 19c, its stability is further improved. As a result, lift and oscillatory combustion of the first flame 19a are less likely to occur, and noise generation is suppressed.

As described above, the second flame 19b becomes an extremely stable flame, but the second burner unit 1b which generates the flame 19b is equipped with a high-pressure cord 21 as an ignition device. Since the detection device 22 including the 20 and the detection code 23 is provided, the ignition detection can be performed extremely reliably.

By the way, the stability of the first flame 19a due to lean fuel combustion also depends on the mixing state of the air-fuel mixture, and the stability is poor unless a sufficiently uniform mixture is formed. In this regard, in the burner of the present invention, as described above, the distance from the introduction portion 4a of the first burner unit 1a to the flame hole portion 3a is longer than that of the second burner unit 1b. Therefore, since the mixing distance is long, the fuel gas and the air are mixed well, and even if the fuel is lean, a large amount of the uniformly mixed gas can be supplied to the flame hole portion 3a. Therefore, in the burner of the present invention, the stability of the first flame 19a is good in this respect as well.

The combustion of the fuel-lean air-fuel mixture which is stabilized as described above is combustion of excess air, and therefore the temperature of the flame 19a is maintained at a low temperature by its cooling action, and the generation of NOx is reduced. .. Further, since the amount of the fuel gas used for combustion as a fuel-lean mixture is larger than the amount of fuel gas used for a fuel-rich mixture, the NOx content of the burner as a whole is increased. The amount generated is also small.

Next, in the above combustion state, the supply of the fuel gas from the fuel gas supply pipe 18r on the right side of the drawing is stopped, and the right side portion r of the first and second nozzle holders 12a and 12b is removed. When the supply of all the fuel gas is stopped, the first and second burner units 1a and 1b corresponding to the nozzles 15a and 15b in this portion are extinguished, and the nozzle holder 1
Nozzle 15 between middle part m of 2a and 12b and left part 1
1st, 2nd burner unit 1 corresponding to a, 15b
The combustion of only the a and 1b groups continues.

This burning burner unit 1a, 1
Since the second burner units 1b are located at both ends of the group b, the second flames 19b always exist on both sides of the first flame 19a as in the above-described combustion state, and therefore the above-mentioned first flame 19b is present. The stabilizing action of the first flame 19a by the second flame 19b is not hindered.

Next, in the above combustion state, when the supply of the fuel gas from the intermediate fuel gas supply pipe 18m is stopped, the first and second nozzle holders 12a and 12b corresponding to the intermediate portion m of the first and second nozzle holders 12a and 12b. 1, 2nd burner unit 1a, 1
Only group b continues to burn. Even in this combustion state,
Since the second flame 19b always exists on both sides of the first flame 19a, the stabilizing action of the first flame 19a by the second flame 19b described above is not hindered.

As described above, in the above-mentioned embodiments, the flame hole area to be burned can be changed stepwise without impeding the stabilizing action of the first flame 19a by the second flame 19b. By using a well-known combustion amount control method such as proportional control together, it is possible to suitably adjust the combustion amount over a wide range.

FIG. 11 shows NOx in the burner of the present invention.
It is an example of an emission characteristic. In this example, in the burner as shown in the figure, the air ratio of the fuel rich mixture in the second burner unit 1b is set to λ = 0.4 to 0.7 and the air ratio of the burner as a whole is set. Represents the amount of NOx produced when the air ratio of the fuel-lean mixture in the first burner unit 1a is adjusted so that the value becomes the value shown on the horizontal axis in the figure. The indicated air ratio is a value including the cooling air when the cooling air is flown around the burner units 1a and 1b,
The air ratio in parentheses is a value that does not include this cooling air. Further, the ratio of the amount of fuel gas burned in the first burner unit 1a to the amount of fuel gas burned in the first burner unit 1b is 7.5: 2.5.
As shown in the figure, in the burner of the present invention, the NOx generation amount is significantly reduced as compared with the conventional general Bunsen burner.

Further, FIG. 12 shows an example of the lift limit of the first flame 19a by the first burner unit 1a in the burner of the present invention in comparison with other ones. First, in the burner of the present invention, A is a case where the fuel-lean air-fuel mixture is supplied only to the first burner unit 1a and the flame holding by the second flame of the second burner unit 1b is not performed. 1 shows the lift limit of the burner unit 1a of No. 1 and this limit is about λ = 0.7. On the other hand, B
Shows the lift limit in a conventional general Bunsen burner having a flame holding mechanism, and this limit is about λ = 1.3. C indicates the lift limit of the first burner unit 1a when the first and second burner units 1a and 1b are burned in the burner of the present invention, and λ = 3.0. It is a degree. As described above, in the burner of the present invention, it can be seen that the combustion of the high excess air can be performed more stably and the NOx reduction due to the combustion of the high excess air can be achieved as compared with the conventional general Bunsen burner. ..

[0035]

As described above, the present invention has the following effects. A first burner unit that burns a lean fuel mixture and a second burner unit that burns a rich fuel mixture can be alternately and densely mounted, and a compact burner with a large combustion amount can be obtained. .. Since the ratio of the fuel gas amount used for combustion of excess air is large, the amount of NOx generated is small with respect to the combustion amount of the entire burner. Combustion of excess air can be stably performed without causing lift of a flame or oscillating combustion, so that generation of noise is suppressed. A lean fuel-air mixture is obtained by mixing the fuel gas and air for each burner unit, so even if flashback occurs due to clogging etc. and mixing is not performed smoothly, it is limited to the local area and a loud noise is generated. And damage is prevented. Since the second flame is a fuel rich flame, it is a stable flame itself, but the stable flame is further stabilized by the flame holding flame, and the second burner that generates such a stable flame. Since the ignition device 20 and the detection device 22 are provided in the unit 1b, the ignition detection can be performed extremely reliably.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a first burner unit constituting a burner of the present invention.

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

3 is a sectional view taken along line YY of FIG.

FIG. 4 is a perspective view showing an embodiment of a second burner unit constituting the burner of the present invention.

FIG. 5 is a plan view in which the structure of the burner of the present invention is partially omitted.

FIG. 6 is a front view showing the structure of the burner of the present invention with a part thereof cut away.

FIG. 7 is an enlarged front view of an essential part showing an enlarged part of FIG. 6;

FIG. 8 is a side view showing the configuration of the burner of the present invention.

FIG. 9 is a front view showing a nozzle holder constituting the burner of the present invention as viewed from the back side of the nozzle.

FIG. 10 is a side view of the nozzle holder shown in FIG.

FIG. 11 is an explanatory diagram showing the amount of NOx generated by the burner of the present invention in comparison with a conventional Bunsen burner.

FIG. 12 is an explanatory diagram showing an example of the flame lift limit of the first burner unit in the burner of the present invention in comparison with others.

[Explanation of symbols]

 1a 1st burner unit 1b 2nd burner unit 2a, 2b Burner body 3a, 3b Flame hole part 4a, 4b Introduction part 5a, 5b Mixing pipe part 6a, 6b Long slit-shaped opening part 7a, 7b Throat part 8a, 8b throttle part 9 constriction part 10 sleeve fire forming plate 11 air chamber 12a, 12b nozzle holder 13 support box body 14 fan 15a, 15b nozzle 16a, 16b partition plate 17l, 17r, 17m communication pipe 18l, 18r, 18m fuel gas supply pipe 19a 1st flame 19b 2nd flame 19c Flame holding flame l Left side part r Right side part m Intermediate part 20 Ignition device 21 High pressure code 22 Detection device 23 Detection code 24 Flame mixture mixture outflow hole

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kimio Mochizuki 201 Nishi-Kashiwabara Nitta, Fuji City, Shizuoka Prefecture Takagi Sangyo Co., Ltd. (72) Shigenori Akiyama 201 Nishi-Kashiwabara Shinden, Fuji City, Shizuoka Prefecture Within the corporation

Claims (4)

[Claims] 1. A vertical flat burner unit having a flame hole at an upper portion thereof.
A plurality of first and second burner units, each of which constitutes an inlet for fuel gas and air and which constitutes a mixing pipe portion extending from the inlet to the flame hole, are alternately arranged in a row on the lower lateral side. In the first burner unit, the introduction portion is located below the introduction portion of the second burner unit and has a large diameter to allow introduction of a larger amount of fuel gas and air. A fuel gas jetting portion is arranged corresponding to each introduction portion of the first and second burner units, and the first burner unit has a lean fuel and an amount of fuel gas to the second burner unit. In addition to supplying an air-fuel mixture that is larger than the supply amount, a fuel-rich air-fuel mixture is supplied to the second burner unit, and ignition is performed in the flame hole portion of the second burner unit. Characteristic nitrogen oxide low generation burner 2. A structure for detecting a flame in a flame hole portion of a second burner unit.
Nitrogen oxide low generation burner described 3. The low-nitrogen-oxide generating burner according to claim 1, wherein the second burner unit is configured to form a flame for holding flame. 4. The burner body comprises an upper portion having a thin thickness and a lower portion having a large thickness, a flame hole portion is formed at an upper end of the upper portion, and an introducing portion and a mixing pipe portion are formed at a lower portion. And
2. The low-nitrogen-oxide generating burner according to claim 1, wherein the lower part of the second burner unit is made to correspond to the upper part of the first burner unit.