JP2921615B2 - Nitrogen oxide low generation light and burner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-concentration nitrogen oxide burner for use in a small-sized combustion device for home use, small business use, and the like.

[0002]

2. Description of the Related Art Nitrogen oxides (NOx) in the combustion gas of a burner in various combustion apparatuses cause environmental destruction. Therefore, a burner used in a combustion apparatus is designed to reduce the amount of NOx generated. Various measures have been developed and taken. As a countermeasure example, there is application of a lean burn method or a lean burn method in which the flame temperature is reduced by burning excess air to suppress thermal NOx.

Conventionally, these countermeasures have been mainly applied to large-scale combustion equipment for industrial use and commercial boilers, which are legally regulated. Due to problems such as costs and costs, sufficient measures were not taken.

Accordingly, the present inventors have previously proposed a burner in which the above-described concentration combustion method is effectively applied to a small-sized combustion device for home use, small business use, or the like. (For example, refer to the specification and drawings attached to the application such as 1991 Patent Application No. 272062.)

In the burner proposed by the present inventors, a rich burner unit that supplies a fuel-rich mixture to form a straight flame, and a fuel-lean mixture to supply a straight flame. The light burner units to be formed are arranged alternately adjacent to each other, and the amount of gas supplied to the light burner unit is made larger than the amount of gas supplied to the rich burner unit for combustion.

Such a burner aims to reduce the amount of NOx generated as a whole by increasing the proportion of excess air burned by a fuel-lean mixture, and generally has a poor fuel stability due to poor flame stability. The flame of the air-fuel mixture is stabilized by the flame of the fuel-air-rich air-fuel mixture, thereby preventing the generation of CO due to incomplete combustion.

Accordingly, in this burner, NOx
In order to reduce the fuel consumption, it is necessary to further increase the total excess air ratio and further increase the combustion ratio of the fuel-lean mixture.

[0008]

In order to further increase the total excess air ratio, it is necessary to increase the air flow by the fan. However, if the air flow is increased in this manner, fan noise and combustion noise increase, and noise is increased. Therefore, application to products is difficult. In addition, if the excess air ratio is excessively increased, CO is easily generated due to incomplete combustion, and the flame becomes unstable, so that the combustion range is narrowed. Therefore, it is difficult to apply the present invention to products. .

On the other hand, the method of further increasing the combustion ratio of a fuel-lean mixture also results in an increase in combustion noise.

Therefore, the present invention solves the above-mentioned conventional problems, further reduces NOx in the above-described burner, realizes low noise, and prevents the combustion range from becoming narrow. It is the purpose.

[0011]

In order to solve the above-mentioned problems, according to the present invention, a rich burner unit for supplying a fuel-rich mixture to form a flame in a straight line and a fuel-lean mixture are supplied. Light burner units that form a flame in a straight line are arranged adjacently and alternately, and the amount of gas supplied to the light burner unit is greater than the amount of gas supplied to the rich burner unit. In addition, the present invention proposes a nitrogen oxide low-emission light / dark burner in which a flame cooling rod is installed in a flame along an appropriate number of dark burner units.

According to the present invention, it is proposed that the flame cooling rod is formed as a solid rod or a pipe in the burner having the above structure.

Further, in the present invention, when the flame cooling rod is formed as a pipe, a structure for flowing a cooling fluid through the pipe is proposed. In addition, when the burner of this configuration is applied to a water heater, it is proposed that hot water downstream of a heat exchanger of a water pipe of the water heater be flowed into a pipe as a cooling fluid.

Further, according to the present invention, in the above burner,
It is proposed to install an appropriate number of flame cooling rods per rich burner unit.

[0015]

Combustion of excess air by a fuel-lean mixture in a lean burner unit has poor flame stability by itself, but adjacent to these flames formed linearly,
Since there are stable linear flames due to the fuel-rich mixture in the rich burner unit, these stable flames act as pilot flames to stabilize the excess air flame.

Since the combustion of the fuel-lean mixture stabilized in this manner is the combustion of excess air, the temperature of the flame is maintained at a low temperature by the cooling action due to the increase in the heat capacity, and the amount of generated NOx is reduced. It is kept very low.

The flame of a fuel-rich mixture becomes relatively high in temperature as it is and generates a relatively large amount of NOx. In the present invention, however, this flame is cooled by a cooling rod so that NOx is reduced. The amount generated is reduced. Therefore, as described above, the amount of fuel gas supplied to the combustion as a fuel-lean mixture is larger than the amount of fuel gas supplied to the fuel-rich mixture, and thus the entire burner is burned. The amount of generated NOx can be kept very low.

When the burner of the present invention is applied to a water heater, if the above-described flame is cooled by a cooling rod as a pipe connected to a water pipe of a heat exchanger, the flame is cooled. The recovered heat can be used effectively, and the thermal efficiency does not decrease.

As described above, according to the present invention, NOx generation can be reduced without increasing the excess air ratio of the fuel-lean mixture or increasing the combustion ratio of the fuel-lean mixture. The noise does not increase and the combustion range does not narrow.

[0020]

Next, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 conceptually shows a part of an embodiment of a burner according to the present invention in a cross-sectional view.
Reference numerals a and 1b denote a dense burner unit and a light burner unit in which slit-shaped flame ports a and b are arranged, respectively. These burner units 1a and 1b are arranged adjacently and alternately to form a burner. In the illustrated embodiment, the burners are constituted by arranging dark burner units 1a and 1b at both ends and arranging six dark burner units 1a and five light burner units 1b in a row.

The burner units 1a and 1b are supplied with a fuel-rich mixture and a fuel-lean mixture through appropriate fuel mixing means (not shown), respectively, and burned. Can be applied to a nozzle mixing Bunsen burner or any other suitable structure used for a premix burner.

Assuming that the air ratio of the air-fuel mixture supplied to each of the rich burner unit 1a and the light burner unit 1b is the theoretical air amount λ = 1, for example, λ ≒ 1.6-2.
2. Set so that λ ≒ 0.5 to 0.8. The total ratio of the amount of fuel gas supplied to each of the burner units 1a and 1b is, for example, about 8: 2 to 6: 4 for the rich burner unit 1a: light burner unit 1b,
The total amount of gas supplied to b is set to be larger than the total amount of gas supplied to rich burner unit 1a. However, these air ratios and fuel gas amount ratios can be appropriately determined beyond these ranges.

By the supply of the air-fuel mixture as described above, a flame 3a formed by combustion of the fuel-rich air-fuel mixture is linearly formed on the flame port a of the rich burner unit 1a, and the flame port of the light burner unit 1b. On line b, a flame 3b formed by combustion of a fuel-lean mixture is formed linearly, and because they are adjacent to each other, they burn in contact with each other. At this time, since the rich burner unit 1a is located at both ends of the burner, the flame 3
The flame 3a always exists on both sides of b.

Since the flame 3b is due to combustion of a fuel-lean mixture, its stability is poor alone, but the flames 3a located on both sides thereof are stable due to combustion of a fuel-rich mixture. The stable flame 3a acts as a pilot flame to stabilize the flame 3b with the fuel-lean mixture. Therefore, lift and vibration combustion of the flame 3b due to the fuel-lean mixture are unlikely to occur, and generation of noise is suppressed.

Since the combustion of the fuel-lean mixture stabilized as described above is the combustion of excess air, the temperature of the flame 3b is maintained at a low temperature by the cooling action, and the amount of generated NOx is extremely low. Will be maintained.

The flame 3a formed on the flame opening a of the rich burner unit 1a by the combustion of the fuel-rich mixture becomes relatively high in temperature as it is and generates a relatively large amount of NOx. Therefore, in the present invention, the cooling rod 4 is installed in the flame 3a along the rich burner unit 1a. 2 and 3, the cooling rod 4 is configured as a solid rod made of stainless steel, ceramics, or the like. In FIG. 2, one cooling rod 4 is provided for each dense burner unit 1a, and in FIG. In 2
Books are set up. The cooling rod 4 may be configured as a pipe instead of a solid rod. Such a cooling rod 4
Is intended to reduce the temperature of the flame 3a by being heated by the flame 3a and glowing red, and dissipating the amount of heat generated by the flame as radiant heat.

FIG. 4 shows a specific example in which the burner of the present invention is applied to a water heater. The cooling rod 4 is formed as a pipe. Reference numeral 5 denotes a heat exchanger that heats the water flowing through the water pipe 6 by being heated by the burner of the present invention. The heat exchanger 5 branches a portion of the water pipe 6 on the downstream side of the heat exchanger 5 to constitute a going pipe 7a. The outgoing pipe 7a is connected to the manifold 8
a to one end of each cooling rod 4 and the other end of each cooling rod 4 to a return pipe 7b via a manifold 8b, which is connected to the downstream side of the branch point. At the water pipe 6. In addition, the going pipe 7a and the return pipe 7b may be configured in series with the water pipe 6, that is, by bypassing the water pipe 6 itself, instead of being configured in parallel with the water pipe 6 as in the above configuration.

In this configuration, the flame 3a is cooled by applying heat to the water flowing therethrough via the cooling rod 4, and the amount of heat recovered in association with the cooling of the flame 3a increases as the temperature of the hot water rises. Can be used effectively and does not lower the thermal efficiency. As shown in the figure, in the case where the outgoing pipe 7a and the return pipe 7b are arranged in parallel with the water pipe 6, it is possible to provide a means for adjusting the amount of water flowing through the cooling rod 4 at the branching point or the merging point. it can.

In the present invention, since the flame 3a formed by the combustion of the fuel-rich mixture formed above the rich burner unit 1a is cooled as described above, the amount of NOx generated can be reduced. Therefore, in the present invention, as described above, the amount of fuel gas provided for combustion as a fuel-lean mixture is
Combined with the fact that the amount of fuel gas supplied as a fuel-rich mixture is larger, the amount of NOx generated in the entire burner can be kept very low.

In other words, when the NOx generation amount is to be maintained at the same level, the excess air amount can be reduced as compared with the case where the flame 3a is not cooled. By reducing the noise level, the noise level due to the fan noise and the combustion noise can be reduced.

The disturbance of the streamline of the flame 3a caused by the installation of the flame cooling rod 4 as described above is caused by the flame 3a.
Is small because the jet flow velocity of the fuel-rich mixture forming the gas is smaller than the jet flow velocity of the fuel-lean mixture.
It is easy to keep anyone in the streamline negligible.

FIG. 9 shows an example of the NOx emission characteristics of the burner of the present invention. In this example, a burner as shown in the drawing (note that various configurations such as the shapes of the flame ports a and b in each burner unit 1a and 1b are appropriately selected) is used in the dense burner unit 1a. The air ratio of the fuel-rich mixture is set to λ = 0.4 to 0.7, and the lean fuel in the light burner unit 1b is set so that the air ratio of the burner as a whole becomes the value shown on the horizontal axis in the figure. It shows the generation amount of NOx when the air ratio of the air-fuel mixture is adjusted and burned. The air ratio shown is for burner unit 1.
When the cooling air flows around the areas a and 1b, the value includes the cooling air, and the air ratio in parentheses indicates the value not including the cooling air. The ratio between the amount of fuel gas burned in the light burner unit 1b and the amount of fuel gas burned in the first burner unit 1a is:
7.5: 2.5. As shown in the figure, in the burner to which the present invention is applied, it can be seen that the generation amount of NOx is significantly reduced as compared with the conventional general Bunsen burner.

FIG. 10 shows an example of the lift limit of the flame 3b of the light burner unit 1b in the burner of the present invention, in comparison with the others. First, A shows a burner to which the present invention is applied, in which a fuel-lean mixture is supplied only to the lean burner unit 1b, and the lean burner unit 1b in a case where flame holding by the flame 3a of the rich burner unit 1a is not performed. It indicates the lift limit of the flame 3b, and this limit is about λ = 0.7. On the other hand, B indicates a lift limit in a conventional general Bunsen burner having a flame holding mechanism, and this limit is about λ = 1.3. C denotes the lift limit of the light burner unit 1b when the burners 1a and 1b are simultaneously burned in the burner to which the present invention is applied.
= 3.0.

In the burner to which the present invention is applied,
It can be seen that higher excess air can be stably burned as compared with a conventional general Bunsen burner, and thus NOx can be reduced by combustion of the high excess air.

Next, another example of a burner to which the present invention is applied will be described. First, in FIGS. 5 and 6, the dense burner unit 1a is provided with a tip-outlet 9 having a slit-shaped flame port a on the upper side.
Are formed narrowly to form a space between the side wall 10 and the front-end ejection portion 9 is formed with a sleeve flame port 11. On the other hand, the light burner unit 1b has a ribbon 12
Is installed to form a large number of flame outlets.

FIG. 7 shows still another embodiment. In the burner of this embodiment, the slit-shaped flame port a of the dense burner unit 1a in the construction of FIGS. A ribbon 13 is provided at the tip end similarly to the flame port b of the light burner unit 1b to form a large number of flame ports a, and the sleeve flame port 11 and the sleeve flame forming side wall 10 are spaced apart from each other. It is formed.

FIG. 8 shows still another embodiment. In the burner of this embodiment, a large number of flame ports a and b constituting the dense burner unit 1a and the light burner unit 1b are formed of ceramic or metal. The burner unit 1a, the light burner unit 1b, and the burner as a whole are formed integrally by the plate 14. That is, on the thick plate 14, a large number of flame ports a and b are linearly arranged to form a flame port group, and these flame port groups are alternately arranged in a row to form the dense burner unit 1a. And the light burner units 1b are alternately arranged in rows. Although the diameter of the flame port b of the light burner unit 1b is smaller than that of the flame port a of the dense burner unit 1a, the number is larger,
In the figure, by arranging in two rows, a large amount of fuel-lean mixture can be supplied to the flame port b.

In addition to the above-described embodiment, the burner to which the present invention is applied is such that a rich burner unit for supplying a fuel-rich mixture and a light burner unit for supplying a fuel-lean mixture are alternately arranged adjacent to each other. A specific configuration is appropriate as long as it is a light and light burner in which the amount of gas supplied to the light burner unit is larger than the amount of gas supplied to the light burner unit.

[0039]

As described above, the present invention can reduce the characteristics of the low-density NOx burner, that is, the amount of NOx generated and the height of the combustion chamber can be reduced.
Effectively increases noise while maintaining characteristics such as enabling high-load combustion, good flame holding properties, low combustion noise, less methane slip and other inconveniences, and ensuring complete combustion. This has the effect of suppressing the combustion range and not narrowing the combustion range.

[Brief description of the drawings]

FIG. 1 is a partially sectional perspective view conceptually showing a configuration example of a burner to which the present invention is applied.

FIG. 2 is a front view of FIG. 1 conceptually showing an example of installation of a flame cooling rod.

FIG. 3 is a front view of FIG. 1 conceptually showing another example of installation of a flame cooling rod.

FIG. 4 is an explanatory perspective view conceptually showing still another example of installation of a flame cooling rod.

FIG. 5 is a sectional view conceptually showing another example of the configuration of a burner to which the present invention is applied.

FIG. 6 is a sectional view conceptually showing still another example of the configuration of a burner to which the present invention is applied.

FIG. 7 is a sectional view conceptually showing still another example of the configuration of a burner to which the present invention is applied.

FIG. 8 is a sectional view conceptually showing still another example of the configuration of a burner to which the present invention is applied.

FIG. 9 is an explanatory diagram showing the amount of NOx generated by a burner to which the present invention is applied in comparison with a conventional Bunsen burner.

FIG. 10 is an explanatory diagram showing an example of a flame lift limit of a light burner unit in a burner to which the present invention is applied, in comparison with the others.

[Explanation of symbols]

 1a Concentrated burner unit 1b Light burner unit 2 Burner unit surface 3a, 3b Flame 4 Cooling rod 5 Heat exchanger 6 Water pipe 7a Outgoing pipe 7b Return pipe 8a, 8b Manifold 9 Tip ejection section 10 Side wall 11 Sleeve flame port 12,13 Ribbon 14 thick plate

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Shigetoshi Akiyama 201 Nishi-Kashiwara Nitta, Fuji City, Shizuoka Prefecture Inside Takagi Sangyo Co., Ltd. (56) References JP-A-3-263503 (JP, A) JP-A-5-263 280715 (JP, A) JP-A-6-50512 (JP, A) JP-A-62-180220 (JP, U) JP-A-5-25129 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F23D 14/02 F23D 14/08 F23C 11/00 329-330 F23D 14/78

Claims (7)

(57) [Claims] 1. A rich burner unit for supplying a fuel-rich mixture to form a flame in a straight line and a light burner unit for supplying a fuel-rich mixture to form a flame in a straight line and alternately. In the light and dark burners where the amount of gas supplied to the light burner unit is larger than the amount of gas supplied to the light burner unit, the flame is cooled in the flame along the appropriate number of dark burner units. A low-emission nitrogen oxide burner characterized by installing a rod 2. The burner according to claim 1, wherein the flame cooling rod is a solid rod. 3. The burner according to claim 1, wherein the flame cooling rod is a pipe. 4. The burner according to claim 3, wherein a cooling fluid flows through a pipe constituting the flame cooling rod. 5. The burner according to claim 4, wherein the burner is used for a water heater, and the hot water downstream of the heat exchanger of a water pipe of the water heater is used as a cooling fluid in a pipe constituting a flame cooling rod. Low-concentration nitrogen oxide burner characterized by having a flowing configuration 6. The burner according to claim 1, wherein one flame cooling rod is provided for each rich burner unit. 7. The burner according to claim 1, wherein a plurality of flame cooling rods are provided for each rich burner unit.