JPH0384304A - Low nox bunsen burner - Google Patents

Abstract

PURPOSE:To reduce the generation of NOx by covering a projecting flame opening body with a flame holding plate which has flame holding sections and notch sections alternately along the longitudinal direction of a burner and forming divided main flame opening sections in each of the notch sections and providing in the central section an auxiliary flame opening for transferring flame. CONSTITUTION:the flame opening section 6 of a burner main body 3 at which a gas fuel or a gassified fuel is jetted out of a nozzle 2 and primary air is drawn by the energy of its jetting and the fuel and air are burned as a premixture combustible gas has a flame opening body 7 projecting in the shape of a mountain peak and made of a metal net, etc. and has flame holding sections 8 and notch sections 9 arranged alternately and covers the flame opening body 7 with a flame holding plate 10 and forms main flame openings 11 in the notch sections 9. With this flame opening section 6 projected substantially in the shape of a mountain peak and dividing it along its longitudinal direction the supply of secondary air into the flames becomes efficient, and by providing an auxiliary flame opening 12 for transferring flame at the central section of the flame holding plate the temperature in the high temperature section in the flame is reduced, the flames are stabilized in the low combustion area by the flame holding plate, and the time of oxidation of nitrogen is shortened to reduce NOx.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a Bunsen burner used in household heaters, water heaters, and the like.

Conventional technology A Bunsen burner according to the prior art ejects gaseous fuel or gasified fuel from a nozzle, sucks in primary air using the ejected energy, supplies it to the flame opening as so-called premixed combustible gas, and combusts it. High efficiency. As a result, the flame becomes high temperature, and nitrogen oxides (hereinafter referred to as NO) in the air
There is a drawback that the concentration of (referred to as X) becomes high.

For example, if natural gas (CH4) is diluted with -2 air, 8.7
FIG. 10 shows an example of the flame temperature distribution when a combustible mixture with a concentration of % natural gas is combusted.

As shown in the figure, the temperature at the center 15 of the secondary flame is much higher than that at the center 14 of the primary flame, and the high temperature region exceeding 1800° C. is extremely wide. The reason for this is that because of the premixed gas, the mixture ratio is close to the stoichiometric mixture at the center of the flame, indicating that sufficient combustion is possible even without the supply of secondary air from outside the flame.

Therefore, in order to reduce NOx, a) excessive secondary air is supplied to the high temperature region to lower the flame temperature.

b. Shorten the nitrogen oxidation reaction time by narrowing the high temperature region.

These two points are the technical points for reducing NOx.

Below, we will specifically extract problems with typical conventional techniques.

(1) Japanese Utility Model Application Publication No. 54-165335 discloses a burner in which the flame opening portion of the burner is divided into four parts in the column direction and four parts in the longitudinal direction.

Considering this as a single burner port, the length of the burner port is extremely large compared to the length of the non-flame port in the longitudinal direction of the burner.

Due to this length of the no-flame nozzle, some secondary air is supplied between adjacent nozzles, but because the no-flame nozzle length is large, the flame temperature distribution at the center of the no-flame nozzle becomes close to the distribution shown in Figure ♀. ing.

Further, since the wire gauze mouth is flat, the flow rate of secondary air supplied from the non-flame mouth part is small.

Furthermore, since there is no flame holding plate, the flame tends to become unstable when combustion is low.

(2) Japanese Utility Model Application No. 55-153427 discloses a burner in which the flame opening portion of the burner is divided into four parts in the longitudinal direction and four parts in the row direction.

This specific example also has the same structure as the above-mentioned Japanese Utility Model Publication No. 54-165335, and has exactly the same drawbacks.

(3) Japanese Utility Model Application Publication No. 57-30535 discloses a burner which is divided into a large number of burners in the longitudinal direction and into two in the column direction.

The first drawback of this method is that, like the above-mentioned one, since the flame opening surface is flat, the supply of secondary air is insufficient, the flame temperature becomes high, and NOx is generated in large quantities.

The second drawback is that the flame tends to become unstable during low combustion because there is no flame holding plate.

The third drawback is that the distance between the flame ports in the row direction is long, so the flame transfer in the row direction is poor. Therefore, it is necessary to provide a fire transfer structure using other members.

(4), Japanese Utility Model Application No. 59-18], Publication No. 24 discloses a burner in which the burner's flame port is divided into two in the row direction and into five in the longitudinal direction, and auxiliary flame ports are provided at both ends. There is.

The first drawback of this is the above-mentioned Utility Model Application No. 54-165335
Similar to the publication, the length of the flame opening is long and the length of the flameless opening is short. This increases the flame temperature and increases the generation of NO'X.

The second drawback is that the secondary air is supplied from the outside of each flame port by 4J (seeing in the row direction), and the supply of D (from the inside) is almost nil. , N
This means that more OX will be produced.

Problems to be Solved by the Invention As mentioned above, the conventional technology generates a lot of NOx.

Therefore, the present invention reduces the generation of NOX, and at the same time prevents fire transfer.
The object is to obtain a Bunsen burner with improved flame stability.

Means for Solving the Problems In order to solve the above problems, in the present invention, a burner mouth body such as a wire mesh constituting the burner mouth part is protruded in a substantially mountain shape, and the longitudinal length of the burner is attached to the protruding flame mouth body. Cover with a flame holding plate having flame holding parts and notches alternately along the direction,
A main flame port is formed in each notch.

In addition, an auxiliary flame port for flame transfer is provided in the center of the flame holding plate.

The fuel used in the Bunsen burner is of extremely high quality because the fuel itself does not contain nitrogen.

Therefore, all NOx produced by combustion is so-called thermal NOx, which is produced by the oxidation of nitrogen in the air.
It is.

In the present invention, the flame port protrudes almost in a mountain shape and is divided along the longitudinal direction to improve the supply of secondary air into the flame, and an auxiliary flame port for flame transfer is provided in the center of the flame holding plate. This reduces the temperature in the high humidity part of the flame, stabilizes the flame in the low combustion region with the flame stabilizing plate, shortens the oxidation time of nitrogen, and reduces NOx.

In addition, the auxiliary flame port allows for good flame transfer from the main flame port.

Example Embodiments of the present invention will be described below with reference to the drawings.

In the figure, 1 is a fuel pipe, 2 is a nozzle, and 3 is a burner body. The burner body 3 includes a venturi 4 whose base end opening faces the tip of the nozzle 2, a strainer 5 provided at the outlet of the venturi 4 for evenly distributing the mixed gas, and a strainer 5 formed on the upper surface of the burner body 3. It is formed by a burner port 6 that is The flame mouth part 6 is made of a wire mesh or a perforated steel plate, etc., and includes a flame mouth body 7 whose center part protrudes in an almost chevron shape, a non-porous flame holding part 8 along the longitudinal direction, and a perforated cutout part 9 arranged like a ladder. [Flame stabilizing plates arranged alternately] 0 and more,
By tightly covering the upper surface of the burner port body 7 with this flame stabilizing plate 10, a main burner port 11 divided into each notch portion 9 is formed.

Also, @D of the main flame opening and @E of the flame holding part 8 are E/D=0
．． 2 or more, and when the width E of the flame holding part 8 is increased, the center of the flame holding part 8 is cut out and an auxiliary flame port 12 for flame transfer is provided as shown in FIGS. 2 and 3. There is.

The auxiliary flame opening 12 can also be formed by cutting out a part or the entire center of the flame holding part 8 as shown in FIG.

Note that reference numeral 13 indicates secondary air holes provided on both sides of the flame opening portion 6 and corresponding to the flame holding portion 8.

Next, its operation will be explained.

The fuel supplied from the fuel pipe is supplied to the venturi 4 from the nozzle 2 in the form of a jet stream. The primary air is sucked into the venturi 4 by this jet of gas and becomes a mixed gas, which is evenly distributed by the strainer 5 and then supplied to the flame port 6. On the flame opening 6, the primary flame 1 is generated due to combustion.
4 is generated, and a secondary flame I5 is formed on top of it.

As is well known, a high temperature region is formed within the secondary flame 15, so it is necessary to supply the secondary air 17 into this region early to prevent the temperature from increasing.

In the present invention, the burner port body 7 is protruded in a substantially mountain shape, and the main burner port I
By partitioning I with the flame holding part 8, secondary air is supplied deep into the center of the flame along the slope of the flame port body 7 as shown by the arrow 16, thereby preventing the formation of the above-mentioned high temperature region. can.

Furthermore, a small amount of gaseous fuel is supplied above the flame holding part 8 by the vortex caused by the flow from the main flame opening 11, so the fuel on the flame holding part 8 is completed early, and gases with relatively large specific heats such as cO2 and H2O are It mixes with the flame of the generated post-burning outlet 11, resulting in a so-called self-exhaust gas recirculation effect, which promotes lowering of the temperature of the secondary flame.

Furthermore, as shown in FIGS. 2 and 3, secondary air holes 13 are provided corresponding to the flame stabilizing portions 8, so that the secondary air 17 can be easily supplied.

Furthermore, since the auxiliary flame port 12 is provided at the top of the flame holding part 8, the large flame transfer is improved.

Next, FIGS. 7 to 9 show an embodiment in which the Bunsen burner described above is incorporated into a heater. The combustor main body 18 is divided into a lower air chamber 2o and an upper combustion chamber 2 by a stage 19.
1, and a burner main body 3 is attached to a stage 19. Further, secondary air chambers 22 are provided on the stage 9 so as to correspond to both sides of the flame holding plate 10.
It communicates with the air chamber 20 through a secondary air supply port 23 provided in the air chamber 20 .

[Flame stabilizing plate of secondary air chamber 22] On the O side, secondary air holes 24 are provided in multiple vertical stages (two stages in the figure) so as to correspond to the flame stabilizing section 8. Reference numeral 25 denotes a tertiary air supply port provided at the outermost side of stage 9, which connects the air chamber 20 and the combustion chamber 21. 26 is a fan that sends combustion air to the air chamber 20.

In the above configuration, secondary air can be supplied to the center of the main flame port 11 by providing the secondary air holes 24 in multiple stages up and down. In addition, the supply of secondary air becomes excessive over the flame stabilizing section 8, causing a kind of concentrated combustion to become an appropriate combustible mixture above the main flame port 11, and the temperature of the high temperature section in the secondary flame decreases. It is possible to measure the reduction of NOx.

On the other hand, tertiary air is also supplied to the combustion chamber 21 from the tertiary air supply port 25, but the main purpose of this air is to cool the combustion chamber wall and has little to do with reducing NOx. Therefore, it is also possible to supply all of the air to the secondary air chamber 22 as secondary air.

Effects of the Invention The first effect of the present invention is that the generation of a high temperature region within the secondary flame can be prevented, thereby significantly reducing the amount of thermal NOX generated.

The second effect of the present invention is that a stable flame can be formed by the flame stabilizing portion, so that the good combustion range can be further expanded.

The third effect of the present invention is that secondary air is supplied from above the flame holding part, which improves the diffusion of secondary air within the flame, reduces the limit of red flame (luminous flame) generation, and creates a good combustion zone. Can be expanded.

[Brief Description of the Drawings] Fig. 1 is a sectional view of a Bunsen burner according to the present invention, Fig. 2 is a view from A in Fig. 1, Fig. 3 is a BB sectional view in Fig. 2, and Fig. 4 is a sectional view of a Bunsen burner according to the present invention.
The figure is a sectional view taken along the line C-C in FIG. 2, FIGS. 5 and 6 are perspective views of the flame nozzle according to the present invention, and FIG. 7 is a sectional view of the Bunsen burner according to the present invention installed in a combustor. , Figure 8 is the 7th
9 is a cross-sectional view taken along line EE in FIG. 7, and FIG. 10 is a typical temperature distribution diagram of a Bunsen burner flame. In the figure, 3 is the burner main body, 6 is the burner port, 7 is the burner port, 8 is the flame holding part, 9 is the notch, 10 is the flame holding plate, 11 is the main burner port, 12 is the auxiliary burner port, 13 .24 is a secondary air hole.

Claims (3)

[Claims] (1) A Bunsen burner in which gaseous fuel or gasified fuel is ejected from a nozzle (2), primary air is sucked by the ejection energy, and is burned as a premixed combustible gas at a flame port (6). It has a flame mouth body (7) such as a wire mesh with a flame mouth part (6) protruding in a substantially chevron shape, and flame holding parts (8) and cutout parts (9) alternately along the longitudinal direction of the burner, A low NOx Bunsen burner consisting of a flame holding plate (10) placed over a burner port body (7), with a main flame port (11) formed in the notch (9). (2) A low NOx Bunsen burner according to claim 1, wherein an auxiliary flame port (12) for flame transfer is provided in the center of the flame holding plate (10). (3) In claim 1, secondary air chambers (22) are provided on both sides of the flame stabilizing plate (10), and the secondary air chambers (22)
A low NOx Bunsen burner with vertically multistage secondary air holes (24) at positions corresponding to the flame holding part (8).