JPH0694220A - Low nitrogen oxide burner - Google Patents

Abstract

PURPOSE:To provide a low nitrogen oxide burner in which a flame can be held near a flame port even if a back fire starts to be generated in a flame of a fuel excess side burner at the time of low load combustion in which a heat generation amount is reduced, and drawing of the flame into the burner or arrival of the fame at fuel gas and primary air suction port can be prevented. CONSTITUTION:A burner has a second burner 2 for forming a flame port 21 at a side of a flame port 11 of a first burner 1 in such a manner that the burner 1 has a suction port for sucking fuel gas independently from the burner 1, and comprises a communication passage 3 formed at one of the burners 1 and 2 to supply fuel excess mixture gas of an ignition limit or more and supply air excess mixture gas to the other and formed near the port 21 of the second burner to guide air excess mixture gas into a burner of fuel excess mixture gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low nitrogen oxide burner used as a heat source for a gas water heater or the like.

[0002]

2. Description of the Related Art Sleeve fire burners are provided on both sides of a main crater of a flat main burner to form slit-shaped sleeve craters sandwiching the main crater. Either one of the main burner and the sleeve fire burner is in excess of air. A low nitrogen oxide burner has been proposed which supplies a fuel-air mixture (hereinafter referred to as an air-rich mixture) and a fuel-air mixture that includes excess fuel (including only fuel; hereinafter referred to as a gas-rich mixture) to the other.

Further, in Japanese Patent Laid-Open No. 3-263503, the excess air ratio of some burners is set to be larger than 1.4, and the excess air ratio of other burners is set to be less than 0.8, so that the whole is constant. 120pp when burned at the air-fuel ratio of
40-60 p of nitrogen oxide (NOx) discharged about m
A low nitrogen oxide (low NOx) burner that can be reduced to pm is disclosed.

However, since the burner has a small amount of air and a small amount of air-fuel mixture on the gas-rich air-fuel mixture side, the flow velocity of the air-fuel mixture becomes small. As a result, if this type of low-nitrogen oxide burner is used for a heating source such as a water heater that requires a large amount of heat generation depending on tapping conditions, the burner on the gas-rich mixture side mixes during low-load combustion. The flow velocity of air becomes smaller than the flame propagation velocity, and the flame tends to be sucked into the burner from the crater.

[0005]

If a flashback occurs and combustion continues with the flame being sucked into the burner, overheating of the components that make up the burner, the attachment of soot inside the burner, misfire, and noise Trouble such as occurrence occurs. The object of the present invention is to keep the flame of the gas-rich mixture side burner close to the crater even during low-load combustion where the calorific value is reduced, and the flame can be drawn into the burner or the intake port for fuel gas and primary air. It is to provide a low-nitrogen oxide burner that can prevent a flashback.

[0006]

The low nitrogen oxide burner of the present invention comprises a second burner forming a crater on the side of the crater of the first burner, the second burner and the first burner being the same as the first burner. Independently, in a burner having a suction port for sucking in fuel gas, one of the first burner and the second burner is supplied with an excess fuel mixture that is equal to or more than the ignition limit, and the other is supplied with an excess of air. It is characterized by forming a communication passage for supplying the air-fuel mixture and for guiding the air-excess air-fuel mixture into the burner of the fuel-air surplus mixture in the vicinity of the crater of the second burner.

[0007]

In the present invention, the gas-rich mixture on the gas-rich mixture side is supplied with a gas-rich mixture exceeding the ignition limit,
A communication passage is provided near the crater of the burner, and the mixture of the air-rich mixture-side burner is supplied to the gas-rich mixture-side burner via the communication passage to dilute it to a combustible air-fuel ratio.
Even when the flow velocity of the air-fuel mixture in the gas-rich air-fuel mixture burner starts to decrease during low-load combustion, the flame is only sucked up to the communication passage where the combustible air-fuel mixture exists. Therefore, troubles such as overheating of parts constituting the burner, adhesion of soot inside the burner, misfire, noise generation, etc. can be prevented, and safety is high.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a combustion part of a water heater in which low-nitrogen oxide burners 100 according to the present invention are fixed by a frame (not shown) and arranged in rows at a predetermined interval. Low nitrogen oxide burner 1
As shown in (a) of FIG. 1 and FIG. 2, 00 is a flat main burner having an elongated main crater 11 consisting of slits arranged in parallel at the upper end, and a mixture air intake 12 provided on the side. 1
(First burner).

The main burner 1 is provided with (b) in FIGS. 1 and 2.
As shown in FIG. 5, flat slit-shaped sleeve craters 21, 21 are formed on both sides of the main crater 11, and a sleeve fire burner 2 (second burner) provided with a common suction port 22 on the side is attached. . In the vicinity of the sleeve fire mouths 21, 21, a communication passage 3 formed of a slit row that connects the flow passage in the main burner 1 and the sleeve fire mouths 21, 21 of the sleeve fire burner 2 is formed.

FIG. 3 shows a water heater, which corresponds to the intake port 12 of the main burner 1 of the low-nitrogen oxide burner 100 and the common intake port 22 of the sleeve fire burner 2, and the fuel gas supply pipes 4 and 5 are provided.
Are juxtaposed. Proportional valves 41 and 51 for controlling the flow rate of the fuel gas are provided in each of the supply pipes 4 and 5, and nozzles 42 and 52 are arranged in a row. For example, the main burner 1 should have twice as much combustion as the sleeve fire burner 2,
A large amount of fuel gas ejected from the nozzle 42 entrains a large amount of primary air and flows from the suction port 12 into the main burner 1 at a high flow velocity. As a result, the internal pressure of the main burner 1 becomes higher than the internal pressure of the sleeve fire burner 2, and as shown in FIG.
Burns at 1.

The small amount of fuel gas injected from the nozzle 52 entrains a small amount of primary air and flows from the common suction port 22 to the sleeve fire burner 2 at a low flow velocity, becomes lower than the internal pressure of the main burner 1 and is dispersed on both sides. Then, the sleeve craters 21 and 21 burn. The low pressure near the sleeve crater 21 of the sleeve fire burner 2 can be maintained by setting the area of the sleeve crater 21 larger than the area of the main crater 1.

The excess air ratio as the combustion condition of the main burner 1 is set to be a lean air-fuel ratio of 1.4, for example, and the excess air ratio at the sleeve fire burner 2 is a fuel-rich air-fuel ratio outside the flammability limit. (For example, when the fuel gas is methane, the excess air ratio is 0.6 or less). The sleeve fire burner 2 is outside the flammable limit, so continuous ignition and combustion cannot be performed.
Since there is a relative difference in internal pressure between the main burner 1 and the sleeve fire burner 2, the air-rich mixture in the main burner 1 is supplied from the communication passages 3 and 3. Therefore, sleeve fire burner 2
Above the communication passages 3 and 3, the air-fuel ratio is such that ignition and combustion are possible. As a result, the flame of the sleeve fire burner 2 causes the nozzle 5 to
It is possible to prevent flashback up to 2.

In accordance with the setting of the hot water supply temperature of the water heater, the combustion amount is increased or decreased, for example, from a maximum of 30,000 kcal to a minimum of 3,000 kcal. Due to the reduction of the combustion load, the flow velocity of the air-fuel mixture in the main burner 1 and the sleeve burner 2 respectively decreases as shown in FIG. In this case, in the sleeve fire burner 2, the flow velocity of the gas-rich mixture on the sleeve outlet 21 side of the communication passage 3 may be equal to or lower than the flame propagation velocity.

At this time, the flame F is a slit-shaped sleeve crater 21.
Although it penetrates into the sleeve fire burner 2 from the inside, since the air-fuel ratio beyond the communication passages 3 and 3 is non-ignitable, the flame is prevented from propagating to the inside of the sleeve fire burner 2. When the combustion load increases and the flow velocity of the air-fuel mixture in the sleeve fire burner 2 increases,
The flame F returns to the sleeve crater 21. Since the opening areas of the communication passages 3 and 3 are set to a small width of 0.5 mm or less and a length of 3 to 4 mm, the flame F is prevented from entering the main burner 1 from the communication passages 3 and 3. It

Although the sleeve fire burner 2 has been described as the burner having a gas-rich mixture and the main burner 1 as the low nitrogen oxide burner 100 having the air-rich mixture as described above, the air-fuel ratio of the mixture may be reversed. Alternatively, the fuel gas containing no primary air may be supplied to the burner on the gas-rich mixture side. Further, the communication passage 3 may be formed of a row of holes other than the slit, and the burner structure may be other than this. Further, the structure of the low oxynitride burner may be a structure in which one main burner 1 is sandwiched by two sleeve fire burners each having an independent inlet.

[Brief description of drawings]

FIG. 1 is a perspective view of a combustion part of a gas water heater using the low nitrogen oxide burner of the present invention.

FIG. 2 is a cross-sectional view of a low nitrogen oxide burner.

FIG. 3 is a schematic view of a gas water heater equipped with a low nitrogen oxide burner.

FIG. 4 is a cross-sectional view of a low nitrogen oxide burner.

[Explanation of symbols]

 1 Main burner (1st burner) 2 Sleeve fire burner (2nd burner) 3 Communication passage 4 Fuel gas supply pipe for main burner 5 Fuel gas supply pipe for sleeve fire burner 11 Main crater (crater) 12 Suction port 21 Sleeve crater ( 22) Common suction port 100 Low nitrogen oxide burner

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Yagi 2-26 Fukuzumicho, Nakagawa-ku, Nagoya-shi Rinnai Co., Ltd.

Claims (1)

[Claims] 1. A burner having a second burner forming a crater on a side of a crater of the first burner, the second burner having an inlet for sucking a fuel gas independently of the first burner. In (1), either one of the first burner and the second burner is supplied with an excess fuel mixture above the ignition limit, and the other is supplied with an excess air mixture, and is close to the crater of the second burner. A low nitrogen oxide burner is characterized in that a communication passage for guiding the excess air-fuel mixture into the burner for the excess fuel mixture is formed.