JPH0637967B2 - Premixed gas burner - Google Patents

Description

TECHNICAL FIELD The present invention relates to a premixed gas burner used as an industrial, commercial or household heating device.

2. Description of the Related Art Conventionally, a gas burner often adopts a premixed combustion system and uses a radiant heat, so that a Schbank burner or a NO _x burner is used.
Metal slit burners or wire mesh burners have been used to reduce emissions.

Problems to be Solved by the Invention In such a premixed combustion type burner, the air ratio (m) is often used at 1 or more as shown by the formula disclosed in the Examples column. Therefore, the combustion amount variable range (hereinafter referred to as TDR)
Was narrow and was operating with a nearly constant amount of combustion. Therefore, since this type of burner has a narrow TDR, it is necessary to repeatedly use fire extinguishing and ignition when reducing the combustion amount, which consumes more fuel than a burner with a wide TDR and is more difficult to use. But it was bad.

Therefore, in order to widen the TDR, as shown in FIG. 3, a counterflow burner has been proposed in which the flame port 1 and the flame port 2 are opposed to each other with a constant distance therebetween to form the opposed flame 3. . In this burner, the premixed gases 4, 5 are fed through the fuel passages 6, 7. This burner can have a larger TDR than conventional slit burners and wire mesh burners, but the opposing flame shown in FIG. 3 has a high flow rate of the premixed gas ejected from the flame port and a large air ratio. The flame was deformed or fluctuated, and there was a problem in stability of the flame. Therefore T
We could not secure enough DR.

Means for Solving the Problems The present invention is to make the fuel chamber walls provided with flame ports face each other through a gap of a constant distance, arrange the opposing flame ports on the same axis, and use the gap as a combustion chamber, In the premixed gas burner, the outlet of the premixed gas supply passage provided on the outer wall of the combustion chamber wall is a flame port, and the outer wall of the fuel chamber wall and the outer wall of the premixed gas supply passage are cooling surfaces.

Action According to the present invention, the opposing flame is formed in parallel with the wall of the combustion chamber and in a planar shape, and a stable flame is formed without deformation or fluctuation. Therefore, TDR can be sufficiently secured. Moreover, since the outer wall of the combustion chamber wall and the outer wall of the premixed gas supply passage are cooled, the opposing flame can be suppressed to a low level, and the NO _x emission amount is small.

Embodiment FIG. 1 is a perspective view showing an embodiment of the present invention. 8, 9
Are flame outlets, which face each other and are arranged on the same axis. Reference numerals 10 and 11 are walls of the combustion chamber. 12, 1
3 is a premixed gas that mixes combustion gas and air. Reference numerals 14 and 15 denote premixed gas supply passages, and the combustion chamber wall 1
It is provided on the outer wall of Nos. 0 and 11, and the outlets are flame openings 8 and 9. The cross sections of the premixed gas supply paths 14 and 15 and the flame ports 8 and 9 are equal. The combustion chamber walls 10 and 11 are arranged in parallel via a gap 16. Reference numeral 17 is an opposing flame, which is composed of opposing planar flames 18 and 19. 20 is the stagnation point. Reference numerals 21 and 22 are outer walls of the combustion chamber walls, and indicate outer surfaces of the combustion chamber walls 10 and 11, respectively. Reference numerals 23 and 24 denote outer walls of the premixed gas supply passages, which indicate outer surfaces of the premixed gas supply passages 14 and 15, respectively.
Almost the entire circumference of 15 is the outer wall 21, 22 of the combustion chamber wall. The void 16 becomes the combustion chamber 25.

The premixed gases 12 and 13 are supplied to the flame openings 8 and 9 from the premixed gas supply paths 14 and 15. Then, it is supplied to the combustion chamber 25 and burns.

The flame openings 8 and 9 are opposed to each other with a gap 16 therebetween, and premixed gas is ejected from each flame opening to form a stagnation point 20. The flame openings 8 and 9 are rectangular or slit-shaped, but may be circular. When the premixed gases 12 and 13 ejected to the combustion chamber 25 are ignited, the opposing flame 17 is formed. At this time, if the premixed gases 12 and 13 are laminar, the stable opposing flame 1
7 are formed parallel to the combustion chamber walls 10, 11. A stagnation point 20 is formed between the two flame surfaces of the opposing flame 17. The stagnation point 20 ideally has a velocity of 0, and the flow velocity is small near this. Since the flame surface is close to the stagnation point, the flow velocity at the flame surface is small. Therefore, the stagnation point 20 contributes to the stability of the opposing flame 17.

The gas burner of the present invention uses a premixed gas, and if the air ratio (m) is large and the combustion amount is small, there is a risk of flashback.

Therefore, the flame openings 8 and 9 are often smaller than the extinction distance in order to prevent flashback. Therefore, as shown in FIG. 3, the thickness of the flow of the premixed gas ejected from the slit flame ports 8 and 9 is thin, the flow velocities of the premixed gases 12 and 13 are slightly different from each other, or the directions of the flows are not coaxial. In this case, the opposing flame 17 is deformed, causing combustion instability. At this time, the premixed gas 12, 13 near the stagnation point 20
Alternatively, the flow velocity of the combustion gas is low, but increases as it moves away from the stagnation point (above or below the stagnation point in FIG. 1). Therefore, the flame tends to become unstable as it moves away from the stagnation point.

In the present invention, the parallel combustion chamber walls 10 and 11 are provided, and since the flow of the combustion gas is rectified upward or downward in the combustion chamber, the flame is stably formed even if it is separated from the stagnation point. Further, when the flame port projects from the combustion chamber wall, the distance between the combustion chamber walls 10 and 11 is larger than the distance between the slit flame ports 8 and 9. In this case, the flow velocity of the combustion gas 26 becomes slow, and the flame stability of the portion of the opposing flame 17 away from the stagnation point is good.

FIG. 2 shows a stable combustion region of the burner shown in FIG.
The horizontal axis is 1 / m, and the vertical axis is the premixed gas at the flame outlet 1
The flow velocities are 2 and 13 and are shown as relative values when the flow velocity at the time of extinction of the conventional burner with m = 1 is 1. Here, the air ratio (m) can be expressed by the following equation.

The solid line shows the blow-off limit and the flame-extinguishing limit of the conventional slit burner, and the shaded area shows the stable combustion region between both limits. The broken line is the blow-off limit and the extinction limit of the burner of the present invention, the stable combustion region is between the two limits, the stable combustion region of the conventional burner is within the stable combustion region of the burner of the present invention, the burner of the present invention. It can be seen that the stable region of is large. The blow-off limit extends to a region where the flow velocity is high and a region where the air velocity is small (region where the air ratio m is large).

When the flame openings 8 and 9 are smaller than the extinction distance, a flame is formed on the flame openings when the premixed gas flow rate is reduced. At this time,
Despite the heat loss to the burner, it is difficult to extinguish the flame because the flames are facing each other. In this case, when the flow rate of the premixed gas is increased, the flame rises from the flame mouth, but the flame burns stably near the stagnation point. As described above, the burner of the present invention has little heat loss and good flame stability because the flames face each other. In particular, the flame near the stagnation point has good heat stability because there is no heat loss to the burner and the premixed gas flow velocity is close to zero.

In this burner, since the outer wall 21 and the premixed gas supply passage outside wall 23, 24 of the combustion chamber wall cooling, it increased to prevent the opposing flame temperature, it is possible to suppress the flame temperature low, of the NO _x Emissions can be kept low.

In FIG. 1, a pair of flame ports are opposed to each other, but the same effect can be obtained by arranging them in rows at a predetermined interval. At this time, dividing the flame mouth prevents flashback.

EFFECTS OF THE INVENTION According to the present invention, the TDR can be increased by premixed combustion and the stable combustion can be obtained in a region where the air ratio is large, by making the combustion chamber walls provided with the flame openings face each other at a certain distance via a gap. Further, by cooling the combustion chamber wall and the premixed gas supply passage, the flame temperature becomes low, and it is expected that the NO _x will be reduced.

[Brief description of drawings]

FIG. 1 is a perspective view of a main part of a gas burner according to an embodiment of the present invention,
FIG. 2 is a perspective view of a main part of a conventional gas burner, and FIG. 3 is a view showing a stable combustion region of the gas burner. 8, 9 ... Flame port, 10, 11 ... Combustion chamber wall, 16 ... Void, 17 ... Opposing flame.

Claims (2)

[Claims] 1. A combustion chamber wall provided with a flame port is opposed to each other through a gap having a constant distance, the opposing flame ports are arranged on the same axis line, and the gap serves as a combustion chamber, and the outer wall of the combustion chamber wall is provided. The outlet of the provided premixed gas supply unit is a flame port having a cross section equal to that of the premixed gas supply passage, and the cooling surface is formed over almost the entire circumference of the outer wall of the premixed gas supply passage and the outer wall of the combustion chamber wall. And a premixed gas burner. 2. The premixed gas burner according to claim 1, wherein there are a plurality of flame openings on the wall of the combustion chamber and they are arranged in a row.