JP2011202879A - Low nox burner and gas water heater using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-NOx burner which equalizes concentration distribution of low-concentration air-fuel mixture ejected from a lean flame hole by facilitating mixing of fuel gas and air and which reduces a degree of temporal concentration change in the low-concentration air-fuel mixture, and to provide a gas water heater using the low-NOx burner.SOLUTION: The low-NOx burner 10 includes the thin/long lean flame hole 13 for ejecting upward the low-concentration air-fuel mixture introduced from a gas-air inlet port 12 of a first tubular flow passage 11 with the fuel concentration lower than a theoretical air-fuel ratio, and thin/long rich flame holes 16, 16a arranged to surround the lean flame hole 13 for ejecting upward the high-concentration air-fuel mixture introduced from a gas-air inlet port 15 of a second tubular flow passage 14 with the fuel concentration higher than the theoretical air-fuel ratio. The first tubular flow passage 11 arranged in the longitudinal direction is provided with a swirling part 43 which gives a swirl flow to the low-concentration air-fuel mixture while forming inclined parts 41a, 42a on which the low-concentration air-fuel mixture advancing straight abutts and moving along on tube walls 41, 42.

Description

The present invention relates to a low NOx burner that generates combustion gas for heating water and a gas water heater using the low NOx burner.

In order to reduce the amount of NOx in the combustion gas generated at the time of combustion, a thin flame mouth elongated in the front-rear direction formed by a divided flame mouth group that ejects a low-concentration mixture whose fuel concentration is lower than the theoretical air-fuel ratio And a so-called low-NOx burner, which is disposed around the pale flame port and ejects a high-concentration gas mixture having a fuel concentration higher than the stoichiometric air-fuel ratio, and a specific example thereof is, for example, a patent It is described in Document 1.
The low NOx burner of Patent Document 1 has a flow path area near the inlet of the low-concentration mixture so that the fuel gas and air are mixed at a uniform concentration before the low-concentration mixture is ejected from the pale flame outlet. It is narrowed.

JP 7-42917 A

However, in the low NOx burner disclosed in Patent Document 1, since the low-concentration air-fuel mixture passes through a portion having a narrow flow path area with almost no change in the traveling direction, mixing of fuel gas and air is limited, and the light flame outlet However, there is a problem that a flame is not formed stably and noise during combustion is increased.
The present invention has been made in view of such circumstances, and promotes the mixing of fuel gas and air to make the concentration distribution of the low-concentration mixture ejected from the pale flame port uniform, and to reduce the time of the low-concentration mixture. An object of the present invention is to provide a low NOx burner that reduces the degree of typical concentration change and a gas water heater using the low NOx burner.

The low NOx burner according to the first invention that meets the above-described object is an elongated type that ejects upward a low-concentration gas mixture having a fuel concentration lower than the stoichiometric air-fuel ratio introduced from the gas and air inlets of the first tubular flow path. And a high-concentration mixture having a fuel concentration higher than the stoichiometric air-fuel ratio introduced from the gas and air inlets of the second tubular flow channel is ejected upward. In the low NOx burner having an elongated thick flame opening, the first tubular flow path arranged along the front-rear direction has a sloping portion along which the low-concentration mixture that goes straight backwards hits the tube wall. A swirl unit is provided that provides a swirl flow to the low concentration mixture.

In the low NOx burner according to the first aspect of the present invention, the first tubular channel is formed in a vertically long oval shape by the tube wall divided into two on the left and right, and the two inclined portions are It is preferable to be provided at the upper part of one of the split pipe walls and at the lower part of the other pipe wall.

In the low NOx burner according to the first invention, it is preferable that the first tubular flow path has a projecting portion projecting outward on the tube wall.

A gas water heater according to a second invention that meets the above object is a gas water heater that uses the low NOx burner according to the first invention, and takes in the combustion gas from the low NOx burner and the low NOx burner. A primary heat exchanger for heating water, and a secondary heat exchanger for preheating water supplied to the primary heat exchanger by the combustion gas discharged from the primary heat exchanger.

In the low NOx burner according to the first invention and the gas water heater according to the second invention, an inclined portion is formed in the middle of the first tubular flow path along the wall of the low-concentration gas mixture that goes straight on the tube wall. Since the swirl unit that provides swirling flow to the low-concentration mixture is provided, mixing of combustion gas and air is promoted, the concentration distribution of the low-concentration mixture is made uniform, and the low-concentration mixture The degree of temporal density change can be reduced.

Further, in the low NOx burner according to the first invention and the gas water heater according to the second invention, the inclined portion is provided at the upper part of one pipe wall divided into two and at the lower part of the other pipe wall. The swirl flow can be stably generated in the low-concentration air-fuel mixture, and the concentration distribution of the low-concentration air-fuel mixture can be made uniform to stabilize the flame generated at the light flame outlet.

In the low NOx burner according to the first invention and the gas water heater according to the second invention, when the first tubular flow path has a protruding portion protruding outward on the tube wall, a plurality of low NOx burners are provided. When closely arranged in parallel at equal intervals, an air layer can be formed by providing a gap between adjacent low NOx burners, and the temperature of the low NOx burner does not become too high due to the cooling effect of this air layer. It is possible to do so. In addition, by keeping the interval between adjacent low NOx burners constant, the amount of secondary and cooling air flowing through the gap can be made uniform, and combustion can be stabilized.

It is the perspective view which looked at the low NOx burner which concerns on one embodiment of this invention from the left side. It is the perspective view which looked at the same low NOx burner from the right side. It is a perspective view of the gas burner unit using the same low NOx burner. It is a schematic diagram of the gas water heater using the low NOx burner. It is a top view of the low NOx burner. It is a front view of the low NOx burner. (A), (B) is a partial side view of the low NOx burner, respectively.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
As shown in FIGS. 1 to 3, 5, and 6, a low NOx gas burner 10 according to an embodiment of the present invention is introduced from a gas and air inlet 12 of a first tubular flow path 11. An elongated pale flame port 13 for jetting upward a low-concentration gas mixture having a fuel concentration lower than the stoichiometric air-fuel ratio, and the pale flame port 13 are disposed, and the gas and air inlet 15 of the second tubular channel 14 is disposed. This is a low NOx gas burner provided with elongate rich flame ports 16 and 16a for injecting upward a high-concentration mixture having a fuel concentration higher than the stoichiometric air-fuel ratio introduced from above. Hereinafter, these will be described in detail.

As shown in FIG. 3, the low NOx burner 10 is disposed in parallel inside the outer case 29 that is open to the top, and the gas burner unit 17 is configured to include a plurality of low NOx burners 10 and the outer case 29.
The gas burner unit 17 jets an air-fuel mixture obtained by mixing fuel gas and air supplied from a gas pipe 18 (see FIG. 4) above the low NOx burner 10 to form a flame and generate combustion gas. Here, since the low NOx burner 10 is a light and dark burner in which the amount of NOx generated is reduced, the pH of the acidic water produced when NOx is taken into the water is improved, and the drain water can be easily treated. is there. In FIG. 3, the two low NOx burners 10 are depicted as being arranged at a distance in the outer case 29, but actually, a plurality of, for example, 15 to 20 low NOx burners 10 are illustrated. NOx burners 10 are arranged close to each other in parallel.

As shown in FIG. 4, the gas burner unit 17 supplies combustion gas to a primary heat exchanger 19 disposed on the upper part of the gas burner unit 17. The primary heat exchanger 19 heats water directly by sensible heat of the combustion gas taken from the lower part to make hot water, sends the hot water to the mixing valve 20 and discharges the combustion gas from the upper part. The mixing valve 20 mixes hot water produced by the primary heat exchanger 19 with tap water flowing through the water pipe 21 to produce hot water at a predetermined temperature, and supplies the hot water to the hot water pipe 22.
A fan 23 for supplying air into the gas burner unit 17 is fixed to the bottom of the gas burner unit 17.

A secondary heat exchanger 24 that preheats water supplied to the primary heat exchanger 19 by the combustion gas discharged from the primary heat exchanger 19 is disposed downstream of the primary heat exchanger 19. Therefore, the gas water heater 25 having the gas burner unit 17, the primary heat exchanger 19, the secondary heat exchanger 24, and the like uses the sensible heat and latent heat of the combustion gas in the primary heat exchanger 19 and the secondary heat exchanger 24, respectively. Water can be efficiently heated. The water preheated by the secondary heat exchanger 24 is supplied from the water pipe 21.
The primary heat exchanger 19 is connected to a circulation circuit 27 through which water is circulated by the operation of a circulation pump 26 provided in the gas water heater 25. The primary heat exchanger 19 supplies hot water used for hot water supply. While heating, the water flowing through the circulation circuit 27 is heated and supplied to a bathtub or the like. It should be noted that functional parts, members, and the like constituting the gas water heater 25 including the gas burner unit 17 are arranged and fixed in a box-shaped casing 28.

As shown in FIG. 3, an ignition and flame detection means 31 having an electrode 30 for igniting the low NOx burner 10 is provided on the outer wall portion of the outer case 29, and a horizontal direction is provided below the ignition and flame detection means 31. A plurality of openings 32 are formed at equal intervals. The low-concentration air-fuel mixture is generated from the fuel gas and air introduced from the opening 32 and supplied to the low NOx burner 10 disposed in the outer case 29.
In addition, a plurality of openings (not shown) through which fuel gas and air for generating a high-concentration gas mixture supplied to the low NOx burner 10 are introduced are formed in the upper part of the opening 32.

As shown in FIGS. 1, 2, and 5, the low NOx burner 10 arranged in parallel in the outer case 29 is arranged in parallel with the thin flame port 13 elongated in the front and rear and the pale flame port 13 interposed therebetween (that is, Are provided with elongated thick flame ports 16 and 16a in front and rear. A blocking region 33 that does not eject air-fuel mixture or the like is provided between the pale flame port 13 and the rich flame ports 16 and 16a, and the flame generated at the pale flame port 13 and the rich flame ports 16 and 16a. To prevent interference. The pale flame mouth 13 and the rich flame mouths 16, 16 a are arranged at substantially the same height above the low NOx burner 10, and both are formed over the entire front and rear direction of the low NOx burner 10.
As shown in FIG. 5, the rich flame mouth 16 (the same applies to the rich flame mouth 16 a) has a plurality of (in this embodiment) arranged in a straight line along the longitudinal direction (that is, the front-rear direction) of the rich flame mouth 16. 4) Elongate high-concentration gas mixture outlets. The pale flame mouth 13 is provided with a plurality of slits 34 (three in the present embodiment) elongated in the front-rear direction arranged closely in parallel in the left-right direction, and each slit 34 has a straight line along the front-rear direction. A plurality (four in this embodiment) of elongated low-concentration gas mixture outlets arranged are provided.

The low NOx burner 10 is provided with a gas and air inlet 12 of the first tubular channel 11 serving as an inflow port for the low-concentration gas mixture on the lower front side, and at the rear of the first tubular channel 11 The lower end part of the connection flow path 35 which connects the 1st tubular flow path 11 and the pale flame opening 13 is connected.
In addition, the low NOx burner 10 introduces the gas and air in the second tubular channel 14 serving as the inlet of the high-concentration air-fuel mixture above the gas and air inlet 12 in the first tubular channel 11. A mouth 15 is provided. As shown in FIGS. 1, 2, and 6, the second tubular flow channel 14 is partitioned at the center in the left-right direction up and down to form lateral flow channels 36 and 36 a that are independent on the left and right. The low NOx burner 10 has a lower end connected to the rear part of the horizontal flow path 36, a wide flow path 37 connecting the horizontal flow path 36 and the rich flame port 16, and a lower end connected to the rear part of the horizontal flow path 36a. A widened flow path 37a that connects the horizontal flow path 36a and the rich flame port 16a is provided.
With this structure, the low-concentration gas mixture introduced from the gas and air inlet 12 into the first tubular channel 11 is sent to the pale flame port 13 through the connection channel 35, and the gas and air inlet The high-concentration air-fuel mixture introduced from 15 into the lateral flow paths 36 and 36a passes through the widened flow paths 37 and 37a and is sent to the rich flame ports 16 and 16a, respectively.

In the upper half of the low NOx burner 10, an enlarged flow channel 37, a connection channel 35, and an enlarged flow channel 37a are arranged in order from the left in the left-right direction, and each channel is arranged along the vertical direction. It is partitioned by a metal plate. Further, as shown in FIGS. 1 and 2, the wide flow channel 37 (the same applies to the wide flow channel 37 a) has a plurality of inner protrusions 38 on the outlet side (rear side) of the high-concentration mixture in the horizontal flow channel 36. And the high-concentration mixture that travels backward along the horizontal flow path 36 collides with the inner projecting portion 38 and diffuses in the widened flow path 37, toward different locations in the front-rear direction of the rich flame port 16. It flows evenly.

As shown in FIGS. 1, 2, and 6, the main metal fitting 40 of the low NOx burner 10 that forms the first tubular channel 11, the gas and air inlet 12, etc. is formed by pressing a metal plate material. The horizontally formed burner forming members are bent by 90 degrees left and right in a valley fold with reference to a fold line along the front-rear direction provided in the center. The first tubular flow path 11 arranged along the front-rear direction is formed by combining the tube walls 41 and 42 provided on the burner forming member from the left and right sides. The tube walls 41 and 42 divided into two are formed into a vertically long oval shape in the vertical direction.

And the inclined part 41a along which the low-concentration mixed gas which introduce | transduces from the inlet 12 of gas and air, respectively, and advances straight inside the 1st tubular flow path 11 hits the lower part of the pipe wall 41 and the upper part of the pipe wall 42, respectively. , 42a are provided.
The inclined portions 41a and 42a are formed from the rear of the formation portion of the gas and air inlet 12, and are inclined upward and downward, respectively, and the inclination angle with respect to the axial center of the first tubular channel 11 in the front-rear direction, that is, They are θ1 and θ2, respectively. In this embodiment, θ1 and θ2 are angles of 5 to 20 degrees, specifically, θ1 = θ2 = 15 degrees (see FIGS. 7A and 7B).
In the first tubular flow channel 11, the flow channel area of the low-concentration mixture gradually decreases from the gas and air inlet 12 toward the center in the front-rear direction by the inclined portions 41a and 42a, and the inclined portions 41a and 42a. The flow path area of the low-concentration air-fuel mixture gradually increases behind the formation site.

The low-concentration gas mixture that has flowed in from the gas and air inlets 12 hits the inclined portions 41a and 42a and moves upward in the left inclined portion 41a when traveling backward (straightly) along the first tubular flow path 11. Since the vector is obtained as a downward vector at the right inclined portion 42a, the first tubular flow channel 11 can give a swirling flow clockwise to the low concentration mixture. Therefore, the low-concentration air-fuel mixture passes through the first tubular flow channel 11 to facilitate the mixing of the fuel gas and air, and can have a uniform concentration distribution. Moreover, it has confirmed by experiment that the stability of the flame produced | generated by a pale flame mouth improves about 10 to 15% compared with the gas burner which does not provide an inclination part. In the present embodiment, the inclined portions 41a and 42a form the swirling portion 43 that gives a swirling flow to the low-concentration air-fuel mixture.

Further, as shown in FIGS. 1, 2, and 6, projecting portions 44 and 45 projecting outward are formed on the tube walls 41 and 42 in the first tubular channel 11. The protrusions 44 and 45 have the same protrusion height, and protrude in the range of 0.2 to 1.2 mm (0.5 mm in this embodiment) on the left and right. Since the low NOx burner 10 is arranged in parallel in the outer case 29 with the projecting portions 44 and 45 abutting against the adjacent low NOx burner 10, two low NOx burners 10 are sent from the fan 23 between the adjacent low NOx burners 10. A flow path for secondary air and cooling air is secured. Therefore, the low NOx burner 10 is cooled so that the temperature does not become too high due to the secondary air / cooling air flowing along the outer surface of the low NOx burner 10. Further, since the intervals through which the secondary air and cooling air pass are the same, the combustion can be stabilized.

Further, as shown in FIGS. 1, 2, and 6, the low NOx burner 10 is provided with a lateral groove 46 formed in the front-rear direction at the upper part of the left and right side surfaces. In addition to having the effect of maintaining the strength of the side surface of the low NOx burner 10, the lateral groove 46 makes the rising speed of the high-concentration mixture moderate by diffusing by narrowing the flow passage areas of the wide flow passages 37 and 37a. The ejection speed of the high-concentration mixture from the front end to the rear end of the ports 16 and 16a is made uniform.
The circular protrusions 47 formed in front of the upper portions of the left and right side surfaces of the low NOx burner 10 raise the gaps between the plurality of low NOx burners 10 arranged in close proximity by the operation of the fan 23 (see FIG. 4). The air flow rate is partially suppressed. Therefore, the circular protrusion 47 provides an environment in which the flame ignited by the low NOx burner 10 located in the center easily transfers to the low NOx burner 10 disposed adjacent to the left and right.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and all changes in conditions and the like that do not depart from the gist are within the scope of the present invention.
For example, the inclined portion provided in the first tubular channel may have a shape that imparts a counterclockwise (direction) swirling flow toward the rear side to the low concentration mixture.

10: Low NOx burner, 11: First tubular channel, 12: Gas and air inlet, 13: Pale flame port, 14: Second tubular channel, 15: Gas and air inlet, 16, 16a: Rich flame outlet, 17: Gas burner unit, 18: Gas pipe, 19: Primary heat exchanger, 20: Mixing valve, 21: Water pipe, 22: Hot water pipe, 23: Fan, 24: Secondary heat exchanger, 25: Gas water heater, 26: Circulation pump, 27: Circulation circuit, 28: Casing, 29: Outer case, 30: Electrode, 31: Ignition and flame detection means, 32: Opening, 33: Shut-off area, 34: Slit, 35: connection flow path, 36, 36a: lateral flow path, 37, 37a: widening flow path, 38: inner projecting portion, 40: body fitting, 41: tube wall, 41a: inclined portion, 42: tube wall, 42a: inclined Part, 43: turning part, 44, 45: protrusion part, 46: transverse groove, 47: Form the protrusion

Claims (4)

An elongated pale flame port for jetting upward a low-concentration gas mixture having a fuel concentration lower than the stoichiometric air-fuel ratio introduced from the gas and air inlets of the first tubular flow path, and surrounding the pale flame port In a low NOx burner having an elongated rich flame port for ejecting upward a high-concentration mixture having a fuel concentration higher than the stoichiometric air-fuel ratio introduced from the gas and air inlets of the second tubular channel,
In the first tubular flow path arranged along the front-rear direction, an inclined portion is formed on the tube wall along which the low-concentration gas mixture that goes straight hits to give a swirl flow to the low-concentration gas mixture. A low NOx burner characterized in that a swivel unit is provided. 2. The low NOx burner according to claim 1, wherein the first tubular flow path is formed in a vertically long oval shape by the tube wall divided into two on the left and right, and the inclined portion is divided into two. The low NOx burner is provided at the upper part of the one pipe wall and the lower part of the other pipe wall. 3. The low NOx burner according to claim 1, wherein the first tubular flow path has a protruding portion protruding outward on the tube wall. 4. A gas water heater using the low NOx burner according to any one of claims 1 to 3, wherein the low NOx burner and a primary heat exchanger that heats water by taking combustion gas from the low NOx burner And a secondary heat exchanger for preheating water supplied to the primary heat exchanger by the combustion gas discharged from the primary heat exchanger.

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