JP2006112721A - Combustion device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain low NOx equal that of a thick and thin fuel combustion burner while keeping advantages possessed by a bunsen burner such as simple structure, light weight and low HC. <P>SOLUTION: The ratio of secondary air flow velocity ejected from a secondary air port 34 to air-fuel mixture flow velocity ejected from a burner port 21 is set to 2 or more. By this, since an unburned material burned in an outer flame of low velocity is effectively sucked to secondary air by the sucking effect of the secondary air flow of high velocity, and burned in a further lean state, an increase in combustion temperature can be suppressed. Therefore, low NOx equal that of the thin and thick fuel combustion burner can be obtained while keeping advantages possessed by the bunsen burner such as simple structure, light weight, and low HC. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a combustion apparatus that achieves particularly low NOx in a combustion apparatus mainly for home use or business use.

  Conventional combustion apparatuses of this type are generally shown in Patent Documents 1 and 2.

  FIG. 7 is a view showing a conventional combustion apparatus described in Patent Document 1. In FIG. As shown in FIG. 7, the burner 1 is provided in the burner case 2 at a predetermined interval in a direction perpendicular to the paper surface of this figure. An air chamber 3 is formed at the bottom of the burner case 2 and a fan 4 is attached. A fuel nozzle 6 is provided facing the fuel / air inlet 5 of the burner 1.

  In the above configuration, air is supplied from the fan 4 to the air chamber 3, and part of the air flows from the fuel / air inlet 5 into the burner 1 as primary air. Further, fuel is ejected from the fuel nozzle 6 and flows into the burner 1 from the fuel / air inlet 5. The mixture of air and fuel is ejected from the burner 1 into the combustion chamber 7 to form an inner flame which is a premixed flame. The remaining air supplied to the air chamber flows between the burners 1 provided side by side and flows out into the combustion chamber as secondary air. The secondary air and the unburned material of the inner flame are mixed, and an outer flame which is a diffusion flame is formed outside the inner flame. This burner is generally called a Bunsen burner.

  FIG. 8 is a view showing a conventional combustion apparatus described in Patent Document 2. In FIG. As shown in FIG. 8, a lean burner unit 12 having a lean flame port 11 at the top and a rich burner unit 14 having a rich flame port 13 at the top are alternately provided.

In the above configuration, fuel and air flow from the lean inlet (not shown) of the lean burner unit 12 and are mixed in the lean burner unit 12 to generate a lean air-fuel mixture that is rich in air. The mixture flows out and forms a lean flame. On the other hand, fuel and air flow from the rich inlet (not shown) of the rich burner unit 14 and are mixed in the rich burner unit 14 to produce a rich mixture with less air, and the rich mixture flows out of the rich flame port 13. , Form a deep flame. A lean flame with a low flame temperature and a low NOx generation amount and a poor flammability is stabilized by a concentrated flame having a high flame temperature and a large amount of NOx generation, and can suppress the NOx generation amount as a whole. This burner is generally called a light and dark burner.
Japanese Utility Model Publication 2-85239 Japanese Patent No. 2839049

  A Bunsen burner like the prior art 1 (patent document 1) has a simple structure and has an advantage of light weight. However, since it is difficult to suppress the temperature of the flame caused by the secondary air, particularly the so-called outer flame which is a diffusion flame of the Bunsen flame, there is a problem that the flame temperature is high and thermal NOx is often generated.

  On the other hand, the light and dark burner as in Conventional Example 2 (Patent Document 2) has the advantage of low NOx. However, since two types of burners are required, the configuration becomes complicated and there are heavy problems. In addition, since the lean flame has a low burning rate and is difficult to burn, there is a problem that a large amount of unburned HC (hydrocarbon) is generated particularly when the air is excessive or ignition occurs.

  The present invention solves the above-described conventional problems, and an object thereof is to provide a combustion apparatus that realizes low NOx, low HC, a simple configuration, and light weight.

  In order to solve the conventional problem, the ratio of the secondary air flow velocity ejected from the secondary air port to the mixture air flow velocity ejected from the flame port is set to 2 or more.

  As a result, the unburned material that burns in the low-speed external flame is effectively sucked into the secondary air by the suction effect of the high-speed secondary air flow, and burns in a leaner state. Can be suppressed.

  The combustion apparatus of the present invention can realize low NOx equivalent to that of a light and dark burner while maintaining the advantages of the simple structure, light weight, and low HC of the Bunsen burner.

  1st invention has provided the secondary air guide for forming a secondary air port between the said burner body which provided the burner body which formed the flame port and the primary air introduction port, and ejects from the said flame port The ratio of the secondary air flow velocity ejected from the secondary air port to the mixed gas flow velocity is set to 2 or more.

  The unburned material that burns in the low-speed external flame is effectively sucked into the secondary air due to the suction effect of the high-speed secondary air flow, and burns in a leaner state. And low NOx equivalent to that of a conventional light and dark burner can be realized. Compared with the light and dark burner, the structure can be simplified, the weight can be reduced, and the HC can be reduced.

  In the second invention, in particular, in the first invention, the ratio of the secondary air flow velocity ejected from the secondary air port to the mixed gas flow velocity ejected from the flame port is set to 5 or less.

  And since it can suppress that the secondary air flow rate becomes excessive and the pressure loss in a secondary air port becomes excessive, the operation | movement rotation speed of the fan which supplies combustion air can be suppressed, and it can reduce noise.

  In the third invention, in particular, in the first invention or the second invention, the distance between the secondary air port and the flame port is 2 mm or more.

  And the inflow of the secondary air to a flame base is suppressed, the combustion reaction in the part becomes slow, a flame temperature is suppressed, and also NOx can be reduced.

  In a fourth aspect of the invention, in particular, in any one of the first to third aspects of the invention, the burner body is provided with an interval, and the secondary air flows through the formed gap.

  Further, a secondary air passage can be formed without newly providing a secondary air flow passage, and the configuration can be simplified.

  In a fifth aspect of the invention, in particular, in any one of the first to fourth aspects of the invention, the secondary air port is provided in the vicinity of the central axis of the secondary air guide in the burner side direction.

  Further, the distance between the mouthless portions can be increased without increasing the pitch of the burner body, and the increase in the flame temperature can be suppressed and NOx can be reduced without increasing the size of the combustion device.

  In a sixth aspect of the invention, particularly in the first to fifth aspects of the invention, the secondary air port has a long hole shape that is long in the direction perpendicular to the burner body mounting direction.

  Further, the distance between the mouthless portions can be further increased without increasing the side width pitch of the burner body, and an increase in the flame temperature can be suppressed and NOx can be reduced without increasing the size of the combustion device.

  In the seventh invention, in particular, in the first to sixth inventions, the ratio of the primary air mixed with the fuel to the theoretical air amount is set to 0.7 or less.

  And flame temperature can be suppressed and NOx can be reduced.

(Embodiment 1)
1 is an overall cross-sectional view showing a combustion apparatus according to Embodiment 1 of the present invention, FIG. 2 is a cross-sectional view taken along line XX of FIG. 1, FIG. 3 is a plan view of the main part showing the combustion apparatus, and FIG. Fig. 5 is a characteristic diagram showing the relationship between the ratio of the secondary air flow velocity to the flow velocity and the relationship between NOx, noise and CO, and Fig. 5 is a characteristic diagram showing the relationship between the mouthless distance L and NOx and CO.

  1 to 5, a burner body 23 having a flame port 21 at the top and a primary air inlet 22 at the lower side is provided at a predetermined interval, and burner case A24, burner case B25, burner case C26, burner case D27. The burner unit 28 is configured. A fan 29 is attached to the bottom of the burner unit 28. Opposite to the primary air inlet 22, the same number of fuel ejection nozzles 30 for ejecting fuel gas as the burner body 23 are provided. The burner case A24 is provided with a secondary air inlet 31 for guiding the secondary air. A gap formed with the burner body 23 is a secondary air passage 32, and a secondary air guide 33 is provided at the end. A secondary air port 34 having a round hole shape is provided in the vicinity of the central axis of the secondary air guide 33 in the burner attachment direction. The distance L between the opening portion 35 (so-called rim portion) between the flame port 21 and the secondary air port 34 is set to an appropriate value (for example, 4 mm) of 2 mm or more. An ignition means 37 is provided in the combustion chamber 36.

  Next, the operation and action will be described. The fan 29 supplies air, and the air flows as primary air together with the fuel gas ejected from the fuel ejection nozzle 30 from the primary air introduction port 22 to each burner body 23. In each burner body 23, fuel and air are mixed to form a combustible air-fuel mixture, which flows out from the flame port 21 to the combustion chamber 36 to form a so-called Bunsen flame inner flame (not shown). Here, in the range where the primary excess air ratio (ratio of primary air to the theoretical air amount) is about 0.7 to 0.9, as the primary excess air ratio increases, the flame temperature rises rapidly, and the NOx It has the characteristic of generating more. Therefore, in order to reduce NOx, it is preferable to set the primary excess air ratio to 0.7 or less. However, if the primary excess air ratio is set too low, yellow chips are generated, so the primary excess air ratio is preferably set to about 0.6.

  The remaining air supplied by the fan 29 flows through the secondary air inlet 31 and the secondary air passage 32 and flows out from the secondary air port 34 to the combustion chamber 36 as secondary air. The secondary air forms an outer flame outside the inner flame and burns completely. As shown in FIG. 4, the inventors of the present invention have a ratio (V2 / Vmix, hereinafter referred to as a flow rate ratio) of a secondary air flow rate (hereinafter referred to as V2) to a mixture flow rate (hereinafter referred to as Vmix) of 2 or more. It has been found that the amount of NOx generated is equivalent to that of a conventional light and dark burner. This is because the unburned material that burns in the low-speed external flame is effectively sucked into the secondary air by the suction effect of the high-speed secondary air flow, and burns in a leaner state. This is thought to be because the high temperature can be suppressed. However, if the flow rate ratio becomes excessive, the secondary air flow rate becomes excessive, the pressure loss at the secondary air port 34 becomes excessive, and the load on the fan 29 becomes excessive. Also, the secondary air suction effect becomes excessive, the combustion temperature becomes too low, and CO increases. For this reason, the flow rate ratio is preferably 5 or less.

  Further, the present inventors have found that the NOx generation amount can be suppressed low when the mouthless distance L is 2 mm or more as shown in FIG. This is presumably because the inflow of secondary air to the flame base is suppressed, the combustion reaction at that portion becomes slow, and the flame temperature is suppressed. However, if L is too large (6 mm or more), the amount of secondary air flowing into the flame base becomes too small, the combustion speed becomes too slow, the flame base becomes unstable, resulting in increased CO and noise. Also grows. Further, if the pitch and the number of the burner bodies 23 are not changed, the size of the burner body is increased. Considering NOx and CO generation amounts and dimensions, the optimum value of L is about 4 mm.

  As explained above, by setting the flow rate ratio to 2 or more, the unburned material that burns in the low-speed outer flame is effectively sucked into the secondary air by the suction effect of the high-speed secondary air flow. Since the combustion is performed in a lean state, it is possible to achieve a low NOx equivalent to that of a conventional light and dark burner by suppressing a high combustion temperature. Compared with the light and dark burner, the structure can be simplified, the weight can be reduced, and the HC can be reduced.

  In addition, by setting the flow rate ratio to 5 or less, it is possible to prevent the secondary air flow rate from becoming excessive and the pressure loss at the secondary air port from becoming excessive. Noise can be suppressed and reduced.

  Also, by setting the distance between the secondary air port 34 and the flame port 21 to 2 mm or more, the inflow of secondary air to the flame base is suppressed, and the combustion reaction at that portion becomes slow. The flame temperature is suppressed and the NOx can be further reduced.

  Further, the burner body 23 is provided with an interval, and the secondary air flows through the formed gap. Thereby, the secondary air passage 32 can be formed without newly providing a flow path for secondary air flow, and the configuration can be simplified.

  Further, the secondary air port 34 is provided in the vicinity of the central axis of the secondary air guide 33 in the direction in which the burner is provided. As a result, the distance between the mouthless portions can be increased without increasing the pitch of the burner body, and the increase in the flame temperature can be suppressed and the NOx can be reduced without increasing the size of the combustion device.

  In addition, the ratio of primary air mixed with fuel to the theoretical air amount is set to 0.7 or less. Thereby, flame temperature can be suppressed and NOx can be reduced.

(Embodiment 2)
FIG. 6 is a plan view of an essential part showing a combustion apparatus according to Embodiment 2 of the present invention.

  In FIG. 6, this embodiment is different from the first embodiment in that the secondary air port 341 is not a round hole, but has a long hole shape in which the direction perpendicular to the burner body side direction is long.

  As a result, the secondary air opening area equivalent to that of the first embodiment can be maintained, the opening distance can be further increased without increasing the adjacent pitch of the burner body, and the flame can be increased without increasing the size of the combustion apparatus. Temperature rise can be suppressed and NOx can be reduced.

  In each embodiment, the fuel has been described as a gas fuel such as city gas. However, a liquid fuel such as kerosene may be gasified and used.

  As described above, the combustion apparatus according to the present invention uses gas fuel such as city gas or liquid fuel such as gasified kerosene, and burns with low NOx and low HC while having a simple structure and light weight. Therefore, it can be widely applied as a combustion apparatus for hot water supply, heating or cooking.

Whole sectional view showing a combustion apparatus of Embodiment 1 of the present invention XX sectional view of the combustion apparatus in FIG. Plan view of the main part of the combustion device Characteristic diagram showing the relationship between the ratio of the secondary air flow rate to the mixture flow rate and NOx, noise, and CO of the combustion device Characteristic diagram showing the relationship between the mouthless distance L of the combustion device and NOx, CO The principal part top view which shows the combustion apparatus of Embodiment 2 of this invention Overall sectional view showing a first conventional combustion apparatus Overall sectional view showing a second conventional combustion apparatus

Explanation of symbols

21 Flame port 22 Primary air inlet port 23 Burner body 32 Secondary air passage 33 Secondary air guides 34, 341 Secondary air port 35 Non-portion

Claims (7)

A burner body having a flame port and a primary air inlet is provided side by side, a secondary air guide for forming a secondary air port is provided between the burner bodies, and the second air flow rate for the air-fuel mixture jetted from the flame port is A combustion apparatus in which the ratio of the secondary air flow velocity ejected from the secondary air port is 2 or more. The combustion apparatus according to claim 1, wherein a ratio of a secondary air flow velocity ejected from the secondary air port to a mixture air flow velocity ejected from the flame orifice is 5 or less. The combustion apparatus according to claim 1 or 2, wherein a distance between the secondary air port and the flame port is 2 mm or more. The combustion apparatus according to any one of claims 1 to 3, wherein the burner bodies are provided side by side, and the secondary air flows through the formed gap. The combustion apparatus according to any one of claims 1 to 4, wherein the secondary air port is formed in the vicinity of the central axis of the secondary air guide in the direction in which the burner is provided. The combustion apparatus according to any one of claims 1 to 5, wherein the secondary air port has a long hole shape in which a direction perpendicular to the burner body mounting direction is long. The combustion apparatus according to any one of claims 1 to 6, wherein a ratio of primary air mixed with fuel to a theoretical air amount is set to 0.7 or less.

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