JPH0814516A - Combustion apparatus - Google Patents

Abstract

PURPOSE:To suppress combustion noise when NOx is reduced and to prevent vibrating combustion. CONSTITUTION:A plurality of first burners 8 and a plurality of second burners 12 are alternately provided in a burner case 16. A space 17 opened above is provided in the same width as that of a second burner port 14 between adjacent first burner port 10 and the port 14. Further, a mixture passage 18 for communicating a second mixture chamber 13 with the space 17 is provided at the side of the burner 12. Enriched mixture of excess fuel is supplied to the burner 8, and lean mixture to be injected from the port 10 is injected substantially at the same flowing velocity as that of the enriched mixture to be injected from the port 10 is injected from the space 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low NOx combustion device used for a water heater, a heater, etc., which burns gas and gas obtained by vaporizing petroleum.

[0002]

2. Description of the Related Art Conventionally, a low NOx combustion device of this type is shown in FIG.
As shown in FIG. 1, a first burner 3 having a first flame opening portion 1 and a first mixture chamber 2 communicating with the first flame opening portion 1, a second flame opening portion 4, and a second flame. Second air-fuel mixture chamber 5 communicating with the mouth 4
And a plurality of second burners 6 each having the above are alternately placed side by side and housed inside the combustion chamber 7, and the first burner 3 contains a rich fuel-excess rich mixture of fuel and combustion air. The second burner 6 is supplied with a lean air-fuel mixture that is a mixture of fuel and combustion air and is jetted from the first flame opening 1 and the second flame opening 4 respectively, In the flame mouth portion 1, the rich fuel-rich mixture burns while attracting the lean air-fuel mixture ejected from the second flame mouth 4 to form a stable rich flame with low oxygen concentration, In the second flame port 4, the lean air-fuel mixture with excess air is burned by receiving the thermal influence of the rich flame formed on the first flame port 1 to form a lean flame having a low NOx concentration. As a result, stable combustion is realized as a whole inside the combustion chamber 7 to reduce the amount of NOx generated.

[0003]

However, in the above-mentioned conventional configuration, in order to reduce the amount of NOx produced, it is necessary to reduce the amount of rich flame and increase the amount of lean flame. The amount of rich flame formed on the mouth portion 1 is reduced, and the flow velocity of the lean air-fuel mixture jetted from the second flame outlet portion 4 is increased. As a result, at the first flame outlet portion 1. The flame base of a stable rich flame with a low oxygen concentration formed became unstable, causing an increase in combustion noise and the occurrence of oscillatory combustion. Particularly in a small-sized combustion device, there is no space for sound insulation and noise reduction, and it has been difficult to achieve both reduction of NOx generation amount and combustion noise.

The present invention solves the above-mentioned problems, and NO
It is an object of the present invention to realize the suppression of combustion noise and the prevention of oscillating combustion by a simple method even with a small combustion device when the amount of x generated is reduced.

[0005]

In order to achieve the above-mentioned object, the present invention provides a first flame nozzle for ejecting a rich air-fuel mixture containing a mixture of fuel and combustion air, and the first A first burner having a first air-fuel mixture chamber that communicates with the flame opening and a lean air-fuel mixture that mixes fuel and combustion air are ejected in a larger amount and at a higher speed than the first burner. A plurality of second burner portions and a second burner having a second air-fuel mixture chamber that communicates with the second flame outlet portion are alternately arranged, and the adjacent first flame outlet portion and the second A space portion opened upward is provided between the second flame burner portion and the second burner, and a mixture passage that connects the second mixture chamber and the space portion is provided in the second burner.

[0006]

According to the present invention, by the above means, the above-mentioned second burner provided in the second burner is provided in the upwardly open space provided between the adjacent first flame mouth portion and second flame mouth portion. A lean air-fuel mixture that flows into the space from the air-fuel mixture passage that connects the air-fuel mixture chamber to the space, and then jets from the second flame mouth from the upper opening to the air-rich lean mixture. It jets at a flow velocity slower than the flow velocity of air.

The rich fuel-rich air-fuel mixture ejected from the first flame nozzle burns while attracting a lean air-fuel mixture whose flow velocity is slower than that of the second flame nozzle, so that the conventional technique is used. In comparison, a rich flame with a low oxygen concentration can be formed without disturbing the flame base part too much. Further, in the second flame mouth portion, a large amount of lean air-fuel mixture with a high flow velocity is burned by receiving the thermal influence of the rich flame formed on the first flame mouth portion as usual, and NOx. Forms a lean flame with low concentration.

As a result of stabilization of the flame base of this rich flame, the combustion noise is maintained at the same level as in the prior art, and it also contributes to the prevention of oscillating combustion. Realize the device.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show an embodiment of a combustion apparatus of the present invention, and FIG. 1 is a sectional view of a burner portion of the combustion apparatus of the embodiment.

In FIG. 1, reference numeral 8 is a first burner that encloses a first air-fuel mixture chamber 9, and the first burner 8 has an upper surface provided with a large number of slits for ejecting air-fuel mixture. Of the first burner 8, and a throat portion 11 is formed on the upstream side of the first burner 8. Reference numeral 12 is a second burner that encloses the second air-fuel mixture chamber 13, and a second flame port 14 is formed on the upper surface of the second burner 12 by providing a number of slits for ejecting the air-fuel mixture. The throat portion 15 is formed on the upstream side of the second burner 12.

A plurality of such first burners 8 and second burners 12 are alternately arranged side by side inside the burner case 16, and the adjacent first flame mouth portions 10 are arranged.
And the second flame opening portion 14 are provided with a space portion 17 which is opened upward with a width substantially equal to the slit width for ejecting the air-fuel mixture provided in the second flame opening portion 14, and Burner 1
An air-fuel mixture passage 18 that connects the second air-fuel mixture chamber 13 and the space 17 is provided on the side surface of the second side, and constitutes a combustion unit 19 as a whole.

FIG. 2 is a partial sectional view showing the overall construction of the combustion apparatus of the embodiment of the present invention constituted by the combustion section 19. A nozzle 2 for ejecting fuel facing the throat portion 11 of the first burner and the throat portion 15 of the second burner.
A fuel passage 23 having 0, 21 and a fuel control device 22 is provided. Also, the throat part 1 of the first burner
1. The throat part 15 of the second burner has dampers 24, 2 for adjusting the ratio of the amount of air entering each burner.
5 are provided. A blower 26 is provided in the burner case 16.
Is provided to supply air to the combustion section. A control device 27 controls the fuel control device 22 to control the combustion amount, and also controls the blower 26 to supply the optimal air amount required for combustion to the combustion portion. 28 is a heat exchanger, 2
9 is an exhaust stack.

In the above structure, the fuel is controlled by the fuel control device 22 and is supplied from the nozzles 20 and 21 through the fuel passage 23 to the throat portion 11 of the first burner and the throat portion 15 of the second burner. Further, the optimum air amount required for burning this fuel is supplied from the blower 26 to the combustion unit 19, and the ratio of the air amount is adjusted via the dampers 24 and 25 to adjust the throat unit 11 of the first burner to the first unit. After entering the throat section 15 of the second burner and mixing the fuel and air in the first air-fuel mixture chamber 9 and the second air-fuel mixture chamber 13 to make them uniform, the first flame mouth portion 10 and the first air outlet portion 10, respectively. It jets from above the second flame port 14 and the space 17.

In order to reduce the amount of NOx generated during combustion, the total amount of fuel supplied to the first burner 8 is about 2
The size of the nozzles 20 and 21 is adjusted in advance so that 5% of the fuel is supplied to the second burner 12 and about 75% of the total fuel, and the air-fuel mixture in the first air-fuel mixture chamber 9 has excess air. The rich air-fuel mixture having a ratio of 0.25 to 0.5 and the air-fuel mixture in the second air-fuel mixture chamber 13 are supplied with an air amount which becomes a lean air-fuel mixture having an air excess ratio of 1.8 to 2. So that the damper 2
The sizes of 4 and 25 are adjusted.

Further, a part of the lean air-fuel mixture has a second burner 12 in a space portion 17 which is provided between the first flame opening portion 10 and the second flame opening portion 14 which are adjacent to each other and which is opened upward. The second mixture gas chamber 13 and the space portion 17 are provided to communicate with each other, and flow out from the mixture gas passage 18, and then are ejected from the upper opening.

At this time, the flow velocity of the rich air-fuel mixture ejected from the first flame port 10 is about 0.5 to 1 m / s, and the second flame port 14
The flow velocity of the lean air-fuel mixture with excess air is about 4-5m
/ S, but the flow velocity of the lean air-fuel mixture jetted from the space 17 is slower than that of the lean air-fuel mixture jetted from the second flame port 14 about 1 to 1 .5
The ventilation resistance is set so that the air is ejected at m / s.

In the first flame port portion 10, the lean air-fuel mixture ejected from the space portion 17 is burned while attracting it as a supply gas of combustion oxygen to form a stable rich flame having a low oxygen concentration. Since the flow rate of the lean air-fuel mixture that is jetted from the space portion 17 is substantially equal to the flow rate of the rich air-fuel mixture that is jetted from the first flame mouth portion 10, the attraction action of the air-fuel mixture is smoothly performed. Then, the lean air-fuel mixture from this space portion 17 alleviates the influence of the lean air-fuel mixture that is jetted at a high speed from the second flame port portion 14, so that the flame base portion of the rich flame is prevented from becoming unstable. it can. The lean air-fuel mixture ejected from the second flame port 14 is given the thermal effect of this rich flame in the conventional manner to give an appropriate flame forming atmosphere temperature to form a stable flame surface. Burns, NOx
Forms a lean flame with low concentration.

Here, the characteristics of the lean flame and NOx will be described. The generation amount of thermal NOx decreases as the temperature of the combustion reaction zone decreases. Therefore, the heat capacity increases and the flame temperature decreases as the air-fuel mixture contains a large amount of air.
Although the amount of NOx can be reduced, on the other hand, the leaner the air-fuel mixture, the more unstable the holding performance of the flame at the flame mouth, and the flame base blows off from the flame mouth, resulting in incomplete combustion.

Therefore, in the above structure, even if the amount of the lean air-fuel mixture jetted from the second flame port 14 is increased in order to further reduce the amount of NOx generated, the first flame port 10 does. The lean air-fuel mixture necessary for stabilizing the flame base of the burning rich flame can be supplied from the space portion 17 at a substantially equal speed, and the rich flame and the fast flow velocity can be obtained by stabilizing the flame base of the rich flame. Since interference between lean flames can be prevented, it is possible to reduce the amount of NOx generated, suppress combustion noise, and prevent oscillating combustion without increasing the size of the combustion device or adding parts with noise reduction and sound insulation effects. You can

[0020]

As is apparent from the above description, according to the combustion apparatus of the present invention, the following effects can be obtained. A lean air-fuel mixture produced by the second burner is provided between the first and second burners by providing a space portion for ejecting the lean air-fuel mixture leaked from the second burner and having a speed lower than that of the second burner. It is possible to reduce the total amount of NOx generated while increasing the ratio of (1) to stabilize combustion of the first burner.

[Brief description of drawings]

FIG. 1 is a sectional view of a burner portion of a combustion apparatus according to an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view showing the overall configuration of the device.

FIG. 3 is a sectional view of a burner portion of a conventional combustion device.

[Explanation of symbols]

 8 1st burner 9 1st air-fuel mixture chamber 10 1st flame mouth part 11 1st burner throat part 12 2nd burner 13 2nd air-fuel mixture chamber 14 2nd flame mouth part 15 2nd Throat part of burner 16 Burner case 17 Space 18 Mixture passage 20, 21 Nozzle 22 Fuel control device 24, 25 Damper 26 Blower 27 Control device

Claims (1)

[Claims] 1. A first flame mouth portion for ejecting a rich air-fuel mixture containing excess fuel, which is a mixture of fuel and combustion air, and a first air-fuel mixture chamber communicating with the first flame mouth portion. The first burner,
A second flame port that is a mixture of fuel and combustion air and is jetted at a higher speed and at a higher speed than the first burner, and a second flame port that communicates with the second flame port. A plurality of second burners having an air-fuel mixture chamber are alternately arranged side by side, and a space portion provided so as to open upward between the adjacent first flame mouth portion and the second flame mouth portion. And a mixture passage that connects the second mixture chamber and the space to the second burner.