JPH116605A - Lean combustion burner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase of adhesion of flame to the edge part of a burner port by a method wherein the combustion surface of a plane-form gas burner surface of a gas burner which premixture lean fuel is composed of a burner port plate having a plurality of burner ports longitudinally and laterally formed at intervals of a proper distance. SOLUTION: In a premixture part, air-fuel mixture branched into the right and the left once by air-fuel mixture passages 13 out both sides is agitated by an eddy current generated by the front edge of a triangle block 14, and air-fuel mixtures fed from the right and the left to a mixture space between the front of the triangle clock 14 and a burner port plate 1, and mixture is further promoted. The mixture is injected through the burner ports 2 to are external part and flames into which flame is divided at the respective burner ports an burnt. An air-fuel mixture passage 13 is formed such that a sectional area is formed at approximately constant value along an advancing direction. Thus, the incurring of a pressure loss in the air-fuel mixture passage 13 is extremely low. This constitution performs suction of quantities of air for lean conbustion, coupled with constitution of the burner port 1 having a high total burner port area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lean burn type low NOx gas burner used for domestic water heaters and fan heaters.

[0002]

2. Description of the Related Art Regarding the reduction of NOx in household gas appliances, a NOx value of about 30 to 50 ppm is currently achieved by a concentration combustion system or a two-stage combustion system. Even lower NOx
And the conventional method has its limitations. On the other hand, the lean burn system that mixes the combustion air to a stoichiometric air ratio or more,
Although the low NOx effect is extremely large, the flame is easy to lift due to the high flow velocity, and the high supply pressure and large mixing space are required because the mixing of the fuel gas and air greatly affects the combustion state. However, there is a problem that the cost is increased and the size of the device is increased.

[0003]

In the lean burn system, it is important how to make a uniform mixture. If the mixture becomes uneven, NOx is generated in a portion where the concentration of the fuel gas is high. The low NOx value increases. In lean combustion, it is necessary to uniformly mix a small amount of fuel and a large amount of air.However, an inexpensive sirocco-type fan inevitably has insufficient pressure and insufficient mixing. However, there is a problem that the mixing tube becomes long. Even if a fan mixer is used, a uniform air-fuel mixture can be obtained.However, due to the structure in which fuel gas is injected into the fan, if the turndown is increased, the danger of external gas leakage and backfire may occur. Risk of explosion due to Further, even if the mixing is improved, a larger amount of air is mixed in than the stoichiometric air ratio, so that the combustion speed is reduced and lift combustion is easily caused, so that there is a problem that a stable flame is hardly obtained. The present invention solves such a problem and provides a low-cost, compact, low-N
It is intended to provide an Ox burner.

[0004]

As shown in FIGS. 1 and 2, a lean burn burner according to the present invention has a flat combustion surface of a gas burner to which a premixed lean fuel is supplied, which is spaced apart from each other by an appropriate distance. A wire mesh 3 is formed in each of the flame holes 2 by forming a flame hole plate 1 having a plurality of flame holes 2 arranged vertically and horizontally (Claim 1). Alternatively, as shown in FIG. The combustion surface is formed by the porous plate 4 and the grid-like plate 5 is adhered or adhered to the downstream surface of the porous plate 4 (claim 2).
In the structure of the first aspect, even if the area of the flame hole is relatively large, the difference in the ejection speed between the central portion and the side portion of the flame hole 2 can be made relatively small by the wire mesh 3. ,
In addition, by generating a vortex within the space between the flame holes 2, the adhesion of the flame to the peripheral portion of the flame hole 2 is increased, thereby preventing the flame from blowing out. In addition, a large amount of primary air for lean combustion can be mixed by reducing the pressure loss in the flame hole 2, and the porous plate 4 That the air-fuel mixture oozing through the air is so thin that lift combustion occurs entirely without the grid plate 5,
The vortex generated in front of the grid plate 5 enhances the adhesion of the flame at the edge of the grid plate 5, thereby stabilizing the combustion.

[0005]

1 to 3 show an embodiment of a lean burn burner according to the present invention, wherein a sirocco type fan 7 is connected to a lower part of a rectangular parallelepiped burner body 6, and FIG. The primary air supplied by the fan 6 passes through a current plate 8 composed of a punching panel and is supplied to a premixing unit 9 provided above. The premixing section 9 includes an air introduction section B whose cross-sectional area gradually decreases toward the narrowest section A,
An expanded portion C whose cross-sectional area gradually increases from the narrowest portion A toward the front is formed by the side wall plates 10 bent in a dogleg shape, and a pipe extends along the ridge line of the narrowest portion A. A gas nozzle 11 having a rectangular shape is provided, and a large number of nozzle holes 12 are arranged in a tube wall of the gas nozzle 11. Further, a passage 13 for the air-fuel mixture is provided between the widening portion C and the side wall plates 8.
A triangular block 14 having an isosceles triangular cross section is disposed with an interval of と. The mixture is supplied between the front surface of the triangular block 14 and the flame hole plate 1 provided in front of the triangular block. A mixing space 15 having a fixed width for sufficiently stirring and mixing is formed.

In the premixing section 7, the mixture passages 1 on both sides are provided.
The air-fuel mixture once branched left and right by 3 is agitated by the vortex generated at the leading edge of the triangular block 14, and is supplied from the left and right in the mixing space between the front surface of the triangular block 14 and the flame hole plate 1. The air-fuel mixture collides with each other to further promote the mixing, and is injected outside from each of the flame holes 2 to form a flame divided for each flame hole 2 on the front surface of the flame hole plate 1 and burn. Each of the mixture passages 13 is formed such that the cross-sectional area thereof is substantially constant along the traveling direction. Therefore, the pressure loss in the mixture passage 13 is extremely small, and this is because the flame holes having a large total flame hole area are large. In combination with the configuration of the plate 1, a large amount of air for lean combustion can be sucked.

In the embodiment shown in FIGS. 1 to 3, the flat combustion surfaces of the gas burners to which the relatively low-pressure lean premix is supplied are arranged vertically and horizontally at appropriate intervals from each other. And a wire mesh 3 is stretched in each of the flame holes 2, and a wire between the central portion and the side portion in each of the flame holes 2 is formed by the wire mesh 3. By reducing the difference in the ejection speed and keeping the flow velocity at the center of the flame hole within the combustion speed, and as shown in FIG. 3, by generating a vortex within the interval between the flame holes 2, the combustion heat of the flame is reduced. It is transmitted to the rear air-fuel mixture through the backflow of the vortex to enhance the flammability of the flame at the periphery of the flame hole 2, so that even if the flame hole area is large, the flame does not lift and the turndown is sufficient. Even if it is large, flashback is prevented by the wire netting 3 and the flame holes 2 To a kick pressure loss can be made sufficiently small, in which contamination of a large amount of primary air for even lean combustion without the use of high pressure blower becomes possible. The flame holes 2 can be not only rectangular but also circular, and if the flame holes 2 are arranged in a staggered manner, the flame holding effect is further improved. It is preferable that the wire mesh 3 is provided with being slightly retracted from the front edge of the flame hole, as shown in the figure, whereby it is possible to prevent red heat of the wire mesh at the edge of the flame hole 2 at the time of turndown. Further, since the allowable range of the flow velocity between the blowout and the red heat is widened, it is possible to increase the turndown ratio. FIG. 4 shows an example of a method for manufacturing the above-mentioned flame-perforated plate 1.
6 is inserted, and then the space between the two cuts 16 is made to protrude by pressing. The plate 1 on which the flame holes 2 are formed in advance is overlapped with this, and the protruding portion 17 is fitted into each flame hole 2.

FIG. 5 shows an embodiment of the second aspect of the present invention, in which the burning surface of the burner is formed by pressing metal fibers.
A lattice-shaped baffle plate 5 is welded to the front surface of the porous plate 4. In the case of the wire mesh 3, the center of the flame hole 2 had a higher flow velocity than the side, but in the case of the porous plate 4, the flow velocity of the air-fuel mixture oozing through the porous plate 4 was almost equal to the whole. It is like. However, since the air-fuel mixture is thin, the entire surface of the porous plate 5 is lifted without the lattice plate 5 if there is no lattice plate. With the provision of 5, the eddy current generated at the front of each grid can enhance the adhesion of the flame at the edge of each grid 5, and can prevent the lift of the flame as a whole.

[0010]

As described above, the present invention has a plurality of flame holes 2 which are provided with a flat combustion surface of a gas burner to which a premixed lean fuel is supplied, which are arranged vertically and horizontally at appropriate intervals from each other. Due to the configuration of the flame hole plate 1, the mixing is promoted by the vortex generated within the space between the flame holes 2, and the adhesion of the flame at the edge of the flame hole 2 can be increased. Since the porous plate 3 is stretched or filled, the difference in the ejection speed between the central portion and the side portion of the flame hole 2 is reduced, thereby preventing the blowout of the flame and the red heat of the flame hole, and simultaneously, There is an advantage that the pressure loss can be reduced and a large amount of primary air can be sucked in for lean combustion.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of the present invention.

FIG. 2 is a top view of the flame hole plate used in the above.

FIG. 3 is a sectional view of a main part of a flame hole plate.

FIG. 4 is a process chart showing an example of the method for manufacturing a flame-perforated plate.

FIG. 5 is a perspective view of a main part of another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flame hole plate 2 Flame hole 3 Porous plate 4 Burner main body 5 Porous plate 6 Grid plate 7 Sirocco fan 8 Rectifier plate 9 Premixing part 10 Side wall plate 11 Pipe-shaped gas nozzle 12 Nozzle hole 13 Mixed air passage 14 Triangular block 15 Mixed space 16 Cut 17 Projecting part

Claims (2)

[Claims] 1. A flat combustion surface of a gas burner to which a premixed lean fuel is supplied is constituted by a flame plate having a plurality of flame holes arranged vertically and horizontally at appropriate intervals from each other. Lean burner with wire mesh stretched over. 2. A lean burner in which a plate-like combustion surface of a gas burner to which a premixed lean fuel is supplied is constituted by a porous plate, and a lattice plate is adhered or adhered to a downstream surface of the porous plate. Burning burner.