Flat burner

Abstract

The present invention provides a flat burner that is relatively long in the front-rear direction, having a main flame port (63) at the upper end and side-fire flame ports (64) located at at least one lateral position of the main flame port (63), and using a hydrogen-containing fuel as the fuel, capable of preventing flashback at the side-fire flame ports where the gas ejection speed is relatively slow. A mixture of fuel and air that is leaner in fuel concentration than the stoichiometric air-fuel ratio is ejected from the main flame port (63), while only fuel gas is ejected from the side-fire flame ports (64). In addition, the height of the upper end of the side-fire flame ports (64) on the main flame port (63) side is set to be lower than the height of the upper end of the main flame port (63).

Description

Technical Field

[0001] The present invention relates to a flat burner that uses a hydrogen-containing fuel as a fuel. Background Art

[0002] Conventionally, as a flat burner that is long in the front-rear direction, a main flame port is provided at the upper end, and side-fire flame ports are provided at at least one side position in the lateral direction of the main flame port. Among them, a fuel mainly composed of hydrocarbons such as methane and propane is used as a fuel. Moreover, a mixed gas of fuel and air that is leaner in fuel concentration than the theoretical air-fuel ratio (lean mixed gas) is ejected from the main flame port, and the excess air contained in the lean mixed gas is used to lower the temperature of the main flame generated by the combustion of the lean mixed gas, thereby reducing the generation amount of NOx. In addition, a small amount of a mixed gas of fuel and air that is richer in fuel concentration than the theoretical air-fuel ratio (rich mixed gas) is ejected from the side-fire flame port, and the side fire generated by the combustion of the rich mixed gas is used to maintain the main flame (for example, refer to Patent Document 1).

[0003] However, recently, proposals for using renewable energy have been put forward in response to the global warming problem, and it is predicted that power generation equipment based on wind power and solar power will also increase, resulting in a large amount of surplus power. Therefore, countermeasures for surplus power need to be taken. As one of the countermeasures, the following countermeasure has been considered: converting surplus power into hydrogen for storage, and injecting the hydrogen into a gas pipeline, thereby supplying fuel as a hydrogen-containing fuel that can reduce CO2 emissions.

[0004] Here, when using a hydrogen-containing fuel as a fuel in the above flat burner, the following adverse situation occurs. That is, the combustion speed of the hydrogen-containing fuel is very fast, so flashback is likely to occur at the side-fire flame port where the gas ejection speed is slow.

[0005] Patent Document 1: Japanese Patent Laid-Open No. 10-288315 Summary of the Invention

[0006] In view of the above problems, the subject of the present invention is to provide a flat burner that uses a hydrogen-containing fuel as a fuel and can prevent flashback at the side-fire flame port.

[0007] To solve the above subject, the present invention is a flat burner that is long in the front-rear direction, which has a main flame port at the upper end and side-fire flame ports at at least one side position in the lateral direction of the main flame port, and uses a hydrogen-containing fuel as a fuel. It is characterized in that a mixed gas of fuel and air that is leaner in fuel concentration than the theoretical air-fuel ratio (lean mixed gas) is ejected from the main flame port, and only the gas of the fuel is ejected from the side-fire flame port.

[0008] According to the present invention, since only the fuel gas is ejected from the side fire flame port, the side fire formed at the side fire flame port constitutes a diffusion flame. Moreover, the mixed gas with the stoichiometric air-fuel ratio, which has the fastest combustion speed and the highest temperature and exists between the main flame formed by the combustion of the lean mixed gas ejected from the main flame port and the side fire, (the mixed gas formed by the excess air in the lean mixed gas ejected from the main flame port and the fuel ejected from the side fire flame port) undergoes a combustion reaction, and the region where this combustion reaction occurs can be at a position quite far from the upper end of the side fire flame port. As a result, the temperature rise at the upper end of the side fire flame port can be suppressed, thereby preventing flashback.

[0009] In addition, in the present invention, the height of the upper end of the side fire flame port on the main flame port side is preferably set to be lower than the height of the upper end of the main flame port. Accordingly, the excess air in the lean mixed gas ejected from the main flame port and the fuel ejected from the side fire flame port are mixed, and the position where this mixing starts is far from the upper end of the side fire flame port on the main flame port side and far from the distance corresponding to the height difference between the side fire flame port and the main flame port. Therefore, the region where the mixed gas with the stoichiometric air-fuel ratio between the main flame and the side fire burns can be further away from the upper end of the side fire flame port on the main flame port side, thereby improving the reliability of preventing flashback. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a sectional side view of a combustion device equipped with a flat burner according to an embodiment of the present invention.

[0011] Figure 2 is a perspective view of the flat burner according to the embodiment.

[0012] Figure 3 is a perspective view of the flat burner in an exploded state according to the embodiment.

[0013] Figure 4 is taken Figure 2 along the line IV-IV in

[0014] DESCRIPTION OF REFERENCE NUMERALS

[0015] 6... flat burner, 63... main flame port, 64... side fire flame port. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] Refer to Figure 1, 1 denotes a combustion casing that constitutes a combustion device such as a heat source machine for hot water supply. The upper surface of the combustion casing 1 is open, and objects to be heated such as heat exchangers (not shown) are disposed above the combustion casing 1. A partition plate 4 is provided inside the combustion casing 1, and the space inside the combustion casing 1 is divided into a combustion chamber 2 and an air supply chamber 3 below it by this partition plate 4. A fan outside the drawing is connected to the bottom surface of the air supply chamber 3 via a pipe 5, and thus air is supplied from the fan to the air supply chamber 3. A plurality of distribution holes 4a are formed in the partition plate 4, and the air supplied to the air supply chamber 3 is supplied as secondary air to the combustion chamber 2 via these distribution holes 4a.

[0017] Inside the combustion chamber 2, a plurality of flat burners 6 that are long in the front-rear direction are arranged side by side in the lateral direction. In addition, a standing portion 41 is formed by bending the front edge of the partition plate 4, and a manifold 7 is installed in front of the standing portion 41 so as to block the lower front surface of the combustion casing 1. The manifold 7 is provided with gas nozzles 71, 72 facing the inlets 65a, 67a of the inflow pipe portions 65, 67 (described later) of each flat burner 6.

[0018] Refer to Figures 2 to 4 , the flat burner 6 of the embodiment of the present invention includes: a burner main body 61 that is long in the front-rear direction, and a burner cover 62 that covers the upper part of the burner main body 61. At the upper end of the burner main body 61, there is provided: a main flame port 63 having an elongated shape with an open upper part. In addition, by means of the burner cover 62, there are provided: side fire flame ports 64 located on both lateral sides of the main flame port 63.

[0019] The burner main body 61 is composed of a pair of side plates 61a, 61a opposed to each other in the lateral direction. In addition, one plate is bent into a closed state by a fold line that becomes the lower edge of the burner main body 61, thereby forming the two side plates 61a, 61a. Moreover, by punching each side plate 61a, in the burner main body 61, there are formed: a main flame port 63 at the upper end, a main flame inflow pipe portion 65 at the lower part, and a distribution chamber portion 66 that guides the gas from the above-mentioned inflow pipe portion 65 to the main flame port 63.

[0020] The main flame inflow pipe portion 65 extends rearward from an inlet 65a located at the lower front end of the burner main body 61. Moreover, the distribution chamber portion 66 extends upward while expanding forward from the rear end portion of the main flame inflow pipe portion 65. In addition, in the front part of the burner main body 61, a side fire inflow pipe portion 67 is formed so as to be located between the main flame inflow pipe portion 65 and the distribution chamber portion 66. The side fire inflow pipe portion 67 extends slightly rearward from an inlet 67a located at the front end of the burner main body 61 to form an end, and an air vent hole 67b is provided on the side surface of its rear end portion.

[0021] The burner cover 62 has: a pair of side plates 62a, 62a that cover the outside of a pair of side plates 61a, 61a of the burner body 61; and bridging portions 62b at multiple locations in the front and rear that connect the two side plates 62a, 62a at the upper edges of the two side plates 62a, 62a. Moreover, between the side plate 61a of the burner body 61 and the side plate 62a of the burner cover 62, there are defined: a side fire flame port 64 at the upper end, and a passage that guides the gas flowing out of the burner body 1 to the outside through the vent hole 67b via the side fire inflow pipe portion 67 to the side fire flame port 64. In addition, recesses 62c are formed at multiple locations in the front and rear that coincide with the bridging portions 62b of the side plate 62a of the burner cover 62. The recesses 62c are in contact with the outer side surface of the side plate 61a of the burner body 61 and separate the side fire flame port 64 in the front and rear directions.

[0022] In addition, a rectifying member 68 is installed in the main flame port 63. The rectifying member 68 has: a plurality of rectifying plates 68a arranged horizontally. In the rectifying member 68 and at multiple locations in the front and rear that coincide with the bridging portions 62b of the burner cover 62, there are formed abutting portions 68b that cause the rectifying plates 68a to abut against each other and separate the flame port flow paths defined between the rectifying plates 68a in the front and rear directions. In addition, in the upper part of the side plate 61a of the burner body 61, there is formed: a recess 63a that is in contact with the outer side surface of the rectifying member 68 and is relatively long in the front and rear directions. Moreover, between the portion of the side plate 61a above the recess 63a and the rectifying member 68, there is defined: a blind slit 63b where no gas is ejected; and a part of the gas ejected from the main flame port 63 flows back onto the blind slit 63b.

[0023] Here, the flat burner 6 of the present embodiment uses a hydrogen-containing fuel as the fuel. However, the combustion speed of the hydrogen-containing fuel is very fast, so it is easy to generate flashback at the side fire flame port 64 where the gas ejection speed is relatively slow.

[0024] Therefore, in the present embodiment, a mixed gas of fuel and air (lean mixed gas) with a fuel concentration thinner than the theoretical air-fuel ratio, for example, a lean mixed gas with an air excess ratio of 2.0 or more, is ejected from the main flame port 63, and only the gas of the fuel is ejected from the side fire flame port 64. Refer to Figure 1, fuel ejected from the main flame gas nozzle 71 facing the inlet 65a of the inflow pipe portion 65 for the main flame flows into the inlet 65a, and air also flows into the inlet 65a. The lean mixture gas generated by the mixing of the fuel and the air is ejected from the main flame port 63. Further, a shielding cylinder 69a protrudes from a baffle plate 69 overlapping the front surface of the upright portion 41 at the leading edge of the partition plate 4. The front end portion of the side flame gas nozzle 72 is fitted into the shielding cylinder 69a so that air does not flow into the inlet 67a of the side flame inflow pipe portion 7. Therefore, only the fuel ejected from the side flame gas nozzle 72 flows toward the inlet 67a of the side flame inflow pipe portion 67, and thus only the fuel gas is ejected from the side flame port 64.

[0025] If the air excess ratio of the lean mixture gas is set to 2.0 or more, even for hydrogen-containing fuels with a relatively high combustion speed, a flame (main flame) will be formed at a position sufficiently far from the upper end of the main flame port 63. Thereby, the temperature rise at the upper end of the main flame port 63 can be suppressed, and flashback at the main flame port 63 can be prevented.

[0026] In addition, since only the fuel gas is ejected from the side flame port 64, the side flame formed at the side flame port 64 becomes a diffusion flame in which the excess air in the lean mixture gas ejected from the main flame port 63 and the secondary air around the side flame port 64 are mixed into the fuel ejected from the side flame port 64, and the mixed gas after this mixing burns. Moreover, the mixture gas with the stoichiometric air-fuel ratio, which has the fastest combustion speed and the highest temperature, existing between the main flame formed by the combustion of the lean mixture gas ejected from the main flame port 63 and the side flame will undergo a combustion reaction, and the region where this combustion reaction occurs can be made to be at a position quite far from the upper end of the side flame port 64. As a result, the temperature rise at the upper end of the side flame port 64 can be suppressed, and flashback can be prevented.

[0027] And, in the present embodiment, the height of the upper end of the side flame port 64 on the main flame port 63 side (which is consistent with the height of the upper end of the side plate 61a of the burner main body 61) is set to be lower than the height of the upper end of the main flame port 63 (which is consistent with the height of the upper end of the rectifying member 68). Accordingly, the excess air in the lean mixture gas ejected from the main flame port 63 is mixed with the fuel ejected from the side flame port 64, and the position where this mixing starts is far from the upper end of the side flame port 64 on the main flame port 63 side and far from the distance corresponding to the height difference between the side flame port 64 and the main flame port 63. Therefore, the region where the mixture gas with the stoichiometric air-fuel ratio existing between the main flame and the side flame burns can be made to be further away from the upper end of the side flame port 64 on the main flame port 63 side, and thus the reliability of preventing flashback is improved.

[0028] As described above, the embodiments of the present invention have been described with reference to the accompanying drawings, but the present invention is not limited thereto. For example, in the above-described embodiment, the height of the upper end on the side opposite to the main flame port 63 of the side fire flame port 64 (which is the same as the height of the upper end of the side plate 62a of the burner cover 62) is set to be higher than the height of the upper end of the main flame port 63 side of the side fire flame port 64 and slightly lower than the height of the upper end of the main flame port 63, but it is not limited thereto. That is, regarding the height of the upper end on the side opposite to the main flame port 63 side of the side fire flame port 64, it can be set to be equal to the height of the upper end of the main flame port 63 side of the side fire flame port 64 or equal to the height of the upper end of the main flame port 63. In short, as long as the height of the upper end on the side opposite to the main flame port 63 side of the side fire flame port 64 is greater than or equal to the height of the upper end of the main flame port 63 side of the side fire flame port 64 and less than or equal to the height of the upper end of the main flame port 63. In addition, the flat burner 6 of the above-described embodiment has side fire flame ports 64 on both lateral sides of the main flame port 63, but it can also have a side fire flame port only on one lateral side of the main flame port. In addition, the hydrogen-containing fuel may have components other than hydrogen or may not have components other than hydrogen.

Claims

1. A flat burner, which is a burner with the longitudinal direction being the front-rear direction, and has: A burner body, which includes a pair of side plates opposed to each other in the lateral direction; A burner cover, which includes a pair of side plates disposed outside the pair of side plates of the burner body; A main flame port, which is located at the upper end of the burner body, and a rectifying member is installed in the main flame port; and Side fire flame ports, which are located on the lateral sides of the main flame port, It is characterized in that The side fire flame ports are formed between the side plates of the burner body and the side plates of the burner cover, such that the height of the upper end of the side fire flame port on the main flame port side is lower than the height of the upper end of the main flame port, wherein the height of the upper end of the side fire flame port on the main flame port side is consistent with the height of the upper end of the side plate of the burner body, and the height of the upper end of the main flame port is consistent with the height of the upper end of the rectifying member, Using a hydrogen-containing fuel as the fuel, Spraying from the main flame port: a mixed gas of fuel and air that is leaner than the theoretical air-fuel ratio, and only spraying from the side fire flame ports: fuel gas.

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