JP7656297B2 - Surface Combustion Burner - Google Patents

Description

The present invention relates to a surface combustion burner.

There are various types of burners that form a flame by burning fuel gas and combustion air. Among them, a surface combustion burner that mixes and burns fuel gas and combustion air on the surface of a breathable member is described in, for example, Patent Document 1. In this surface combustion burner, fuel gas that is ejected from the combustion header and flows from the inside to the outside of the breathable member and combustion air that flows outside the combustion header are mixed and burned on the surface of the breathable member to form a flame in the air pipe. This makes it difficult for the concentration of fuel gas ejected from the combustion header to become uneven.

JP 2017-146028 A

In surface combustion burners, a spark rod for igniting the mixture of fuel gas and combustion air is arranged facing the outside of the combustion header. However, in conventional surface combustion burners, no special consideration has been given to the positioning of the discharge rod end of the spark rod, which generates a spark between the discharge rod end and the earth part provided in the combustion header. This poses the problem that the discharge rod end of the spark rod is heated to a high temperature by the flame when the mixture is burned. Therefore, further consideration is needed to improve the durability of the discharge rod end.

The present invention was made in consideration of these problems, and aims to provide a surface combustion burner that can improve the durability of the discharge rod end of the spark rod.

One aspect of the present invention is
an air pipe through which combustion air passes;
a fuel pipe disposed within the air pipe and through which a fuel gas passes;
a combustion header connected to a tip end side of the fuel pipe and disposed within the air pipe, the combustion header having a nozzle portion and a flange portion provided on a base end side of the nozzle portion in the axial direction;
an air-permeable member provided on an outer surface of the nozzle portion and formed of a knitted fabric or a porous material;
a spark rod disposed through the flange portion and having a discharge rod end disposed at a position facing an outer surface of the nozzle portion;
the nozzle portion is formed with a plurality of fuel outlets for ejecting the fuel gas and a plurality of first air outlets for ejecting the combustion air, and the flange portion is formed with a plurality of second air outlets for ejecting the combustion air,
a discharge protrusion is formed on an outer surface of the nozzle portion at a base end side in the axial direction at a position facing the discharge rod end,
The fuel ejection ports are located in the surface combustion burner and are formed on the axial tip side of the position where the discharge protrusion is formed.

In the surface combustion burner of the above embodiment, the position of the discharge rod end of the spark rod and the position of the discharge protrusion of the nozzle part are devised. Specifically, the discharge protrusion is formed at a position facing the discharge rod end on the outer surface of the nozzle part at the base end side in the axial direction. The discharge rod end is also disposed at a position facing the outer surface of the nozzle part at the base end side in the axial direction. Furthermore, the multiple fuel ejection holes are formed on the axial tip side of the position where the discharge protrusion is formed.

With these configurations, when a mixture of fuel gas ejected from the multiple fuel nozzles of the nozzle section and combustion air ejected from the multiple first air nozzles of the nozzle section and the multiple second air nozzles of the flange section is combusted, it is possible to make it difficult for the flame caused by combustion near the surface of the breathable member to come into contact with the end of the discharge rod.

Therefore, the surface combustion burner of the above embodiment can improve the durability of the discharge rod end of the spark rod.

FIG. 4 is a cross-sectional view taken along line II in FIG. 3, showing the surface combustion burner according to the embodiment. FIG. 4 is a cross-sectional view taken along line II-II in FIG. 3, showing the surface combustion burner according to the embodiment. FIG. 3 is a view showing the surface combustion burner according to the embodiment, taken along the line III in FIG. 1 . FIG. 2 is an enlarged cross-sectional view of a portion of FIG. 1 showing the surface combustion burner according to the embodiment;

A preferred embodiment of the above-mentioned surface combustion burner will be described with reference to the drawings.
<Embodiment>
As shown in Fig. 1 to Fig. 3, the surface combustion burner 1 of this embodiment includes an air pipe 3, a fuel pipe 4, a combustion header 2, a gas-permeable member 26, and a spark rod 5. The air pipe 3 is configured to allow combustion air A to pass through. The fuel pipe 4 is disposed inside the air pipe 3, and configured to allow fuel gas F to pass through. The combustion header 2 is connected to the tip side L1 of the fuel pipe 4 in the axial direction L and disposed inside the air pipe 3, and has a nozzle portion 21 and a flange portion 24 provided on the base end side L2 of the nozzle portion 21 in the axial direction L. Note that the gas-permeable member 26 is omitted in Fig. 3.

The nozzle portion 21 is formed with a plurality of fuel outlets 221, 222 for ejecting fuel gas F, and a plurality of first air outlets 23 for ejecting combustion air A. The flange portion 24 is formed with a plurality of second air outlets 241 for ejecting combustion air A.

The breathable member 26 is provided on the outer surface of the nozzle portion 21 and is formed of a metal knit. The spark rod 5 is disposed penetrating the flange portion 24 in the axial direction L, and has a discharge rod end 511 at a position facing the outer surface of the nozzle portion 21. A discharge protrusion 210 is formed at a position facing the discharge rod end 511 in the radial direction R on the outer surface of the nozzle portion 21 at the base end side L2 in the axial direction L. The multiple fuel ejection holes 221, 222 are formed on the tip side L1 in the axial direction L of the position where the discharge protrusion 210 is formed.

In this embodiment, the axial direction L refers to a direction parallel to the central axis of the air pipe 3 and the fuel pipe 4. In the axial direction L, the downstream side of the flow of combustion air A in the air pipe 3 and the downstream side of the flow of fuel gas F in the fuel pipe 4 are referred to as the tip side L1, and the opposite side of the tip side L1 is referred to as the base side L2. The circumferential direction C refers to a direction around the central axis of the air pipe 3 and the fuel pipe 4. The radial direction R refers to a radial direction perpendicular to the axial direction L and centered on the central axis of the air pipe 3 and the fuel pipe 4.

The surface combustion burner 1 of this embodiment will be described in detail below.
The surface combustion burner 1 of this embodiment is attached to a heating furnace or the like and is used to heat the atmospheric gas in the furnace. As shown in Fig. 1 and Fig. 2, the air pipe 3 and the fuel pipe 4 are arranged parallel to each other, and have a double pipe structure. The tip of the air pipe 3 in the axial direction L is located on the tip side L1 in the axial direction L further than the tip of the combustion header 2 in the axial direction L. The entire outer periphery of the combustion header 2 is covered by the air pipe 3. When the combustion header 2 is arranged in the air pipe 3, a small gap is formed between the flange portion 24 of the combustion header 2 and the air pipe 3. In the structure of the surface combustion burner 1 that is actually used, the air pipe 3 may be arranged on the inner periphery side of the exhaust pipe through which the exhaust gas after combustion flows.

(Combustion header 2)
1, the nozzle portion 21 of the combustion header 2 has a parallel portion 212 parallel to the axial direction L, and an inclined portion 211 located on the tip side L1 in the axial direction L of the parallel portion 212. The dimension of the inclined portion 211 in the radial direction R decreases as it approaches the tip side L1 in the axial direction L, and the breathable member 26 is disposed opposite the outer surface of the inclined portion 211. The outer surface of the inclined portion 211 of the nozzle portion 21 is formed as a tapered outer surface 201 whose outer shape (dimension in the radial direction R) decreases as it approaches the tip side L1 in the axial direction L.

As shown in Figures 2 and 3, the nozzle section 21 has a protrusion 22 in which a plurality of first fuel nozzles 221 are formed, and a plurality of recesses 230 that form the first air nozzles 23, which are arranged alternately in the circumferential direction C. Each recess 230 is recessed inward in the radial direction R from the outer surface of the protrusion 22. The first fuel nozzles 221 and the first air nozzles 23 are arranged alternately at multiple locations in the circumferential direction C of the combustion header 2.

The flange portion 24 has a disk shape and is formed at the end of the base end side L2 in the axial direction L of the combustion header 2, protruding outward in the radial direction R beyond the nozzle portion 21. In addition to a plurality of second air outlets 241, the flange portion 24 is formed with an insertion hole 242 for inserting the spark rod 5. One of the second air outlets 241 also functions as a flame monitoring port 243 in which a flame detector is disposed to monitor the flame formation state.

As shown in Figures 1 and 2, a fuel passage 20 is formed in the center, including the central axis, of the nozzle portion 21 and the flange portion 24, to which fuel gas F is supplied from the fuel pipe 4. The tip side L1 of the fuel passage 20 in the axial direction L is closed. The central axis of the combustion header 2 is parallel to the central axes of the air pipe 3 and the fuel pipe 4. The fuel passage 20 is formed in the center, including the central axis of the combustion header 2.

As shown in Figures 1 and 3, the multiple first fuel ejection holes 221 are formed in the multiple protrusions 22, branching outward from the fuel passage 20 in the radial direction R. The multiple first fuel ejection holes 221 are formed at multiple locations around the central axis of the combustion header 2, in a state in which the fuel passage 20 communicates with the tapered outer surface 201. The multiple first fuel ejection holes 221 are formed along the radial direction R.

As shown in FIG. 2, the base end side L2 of the multiple first air outlets 23 in the axial direction L is formed as a through hole 231, and the tip end side L1 of the multiple first air outlets 23 in the axial direction L is formed as a recess 230 that communicates with the through hole 231. The multiple second air outlets 241 are aligned in the circumferential direction C of the flange portion 24 and are formed in a state where they penetrate the flange portion 24 in the axial direction L.

As shown in FIG. 1, the multiple fuel ejection holes 221, 222 in this embodiment are composed of multiple first fuel ejection holes 221 and second fuel ejection holes 222 located on the base end side L2 in the axial direction L of the multiple first fuel ejection holes 221. The multiple first fuel ejection holes 221 are formed at multiple locations in the axial direction L and circumferential direction C in the inclined portion 211 of the nozzle portion 21. The second fuel ejection hole 222 is formed in the parallel portion 212 of the nozzle portion 21 at a position on the base end side L2 in the axial direction L of the formation position of the multiple first fuel ejection holes 221 and on the tip end side L1 in the axial direction L of the formation position of the discharge protrusion 210.

As shown in FIG. 4, the second fuel nozzle 222 is formed at a position overlapping the position of the discharge rod end 511 in the circumferential direction C of the parallel portion 212 of the nozzle portion 21. In other words, the second fuel nozzle 222 is formed at a position facing the radial direction R of the discharge rod end 511, or at a position on the tip side L1 in the axial direction L of the position facing the radial direction R of the discharge rod end 511. The fuel gas F ejected from the second fuel nozzle 222 is ejected around the location where sparks are generated by the discharge rod end 511 and the discharge protrusion 210. This can improve the ignition of the mixture by the sparks generated between the discharge rod end 511 and the discharge protrusion 210.

As shown in FIG. 3, the position of the second fuel ejection port 222 in the circumferential direction C of the parallel portion 212 of the nozzle portion 21 that overlaps with the position of the discharge rod end 511 may be, for example, a position within 5° on both sides of the circumferential direction C of the center position of the discharge rod end 511 in the circumferential direction C. In this embodiment, only one second fuel ejection port 222 is formed. The second fuel ejection ports 222 may be formed in a distributed manner on both sides of the circumferential direction C centered on the position of the discharge rod end 511 in the circumferential direction C.

As shown in Figures 1 and 2, the combustion header 2 of this embodiment is formed by joining a first header part 2A in which a fuel passage 20, a nozzle part 21, a plurality of first fuel nozzles 221, a part of the second fuel nozzles 222, and a plurality of first air nozzles 23 are formed, and a second header part 2B in which a discharge protrusion 210, the remaining part of the second fuel nozzle 222, a flange part 24, and a plurality of second air nozzles 241 are formed. The second header part 2B is attached to the outer periphery of the base end side L2 in the axial direction L of the first header part 2A.

(Breathable member 26)
1 and 2, the breathable member 26 in this embodiment is made of a metal knit formed by weaving together a heat-resistant metal fiber material as a fiber material. The breathable member 26 is disposed facing the tapered outer surface 201 of the convex portion 22 of the inclined portion 211 in the nozzle portion 21 of the combustion header 2. An end portion on the base end side L2 in the axial direction L of the breathable member 26 is joined by welding or the like to a position on the tip side L1 in the axial direction L of the parallel portion 212 of the nozzle portion 21.

In addition to metal knit, the breathable member 26 may be made of metal or ceramics having multiple pores or gaps that allow gas to pass through. The breathable member 26 may be made of glass wool made of glass fiber material, for example. The breathable member 26 may also be made of various materials that are heat resistant, breathable, and non-flammable.

(Spark Rod 5)
1 and 4, the spark rod 5 is composed of a central conductor 51 made of a conductive metal material, and an insulator 52 made of an insulating ceramic material that covers the outer periphery of the central conductor 51. The insulator 52 is not provided at the end of the tip side L1 in the axial direction L of the central conductor 51. The end of the tip side L1 in the axial direction L of the central conductor 51 is exposed to the outside as a discharge rod end 511. The central axis of the spark rod 5 is parallel to the central axes of the air tube 3 and the fuel tube 4.

(Relationship between discharge rod end 511 and discharge protrusion 210)
1 to 4, the discharge protrusion 210 is formed on the outer surface of the parallel portion 212 of the nozzle portion 21 of the combustion header 2, protruding outward in the radial direction R beyond the general portion of the parallel portion 212. The discharge protrusion 210 is formed in a band shape whose length in the circumferential direction C is longer than its length in the axial direction L. With this configuration, even if the portion of the discharge protrusion 210 facing the discharge rod end 511 is worn away by discharge, a discharge can be generated between the portions of the discharge protrusion 210 on both sides of the worn portion in the circumferential direction C and the discharge rod end 511. Therefore, the discharge performance can be maintained for a long period of time.

As shown in FIG. 4, the width c of the discharge protrusion 210 in the axial direction L is 3 to 5 mm. This configuration allows a discharge to be generated appropriately between the discharge rod end 511 and the discharge protrusion 210. The length of the discharge protrusion 210 in the circumferential direction C should be greater than the width of the discharge protrusion 210 in the axial direction L and should be 5 mm or more.

As shown in FIG. 3, the discharge convex portion 210 of this embodiment is formed continuously around the entire circumference in the circumferential direction C in the parallel portion 212 of the nozzle portion 21. This configuration makes it easy to form the discharge convex portion 210 in the parallel portion 212 of the nozzle portion 21. The outer surface in the radial direction R of the discharge convex portion 210 of this embodiment is formed along the circumferential direction C parallel to the axial direction L. The shape of the axial direction L of the outer surface in the radial direction R of the discharge convex portion 210 may be a convex curved surface.

As shown in FIG. 4, in this embodiment, the distance b from the end face 245 of the tip side L1 of the flange portion 24 in the axial direction L to the end face 213 of the base end side L2 of the discharge protrusion 210 in the axial direction L is set within a range of 6 to 12 mm. In addition, the distance a from the end face 245 of the tip side L1 of the flange portion 24 in the axial direction L to the end position 521 of the base end side L2 in the axial direction L of the discharge rod end portion 511 (the end position 521 of the tip side L1 of the insulator portion 52 in the axial direction L) is set within a range of b-1 mm to b+2 mm with respect to the distance b.

In other words, the end position of the base end side L2 in the axial direction L of the discharge rod end 511 is set within a range of 1 mm on the base end side L2 in the axial direction L and 2 mm on the tip end side L1 in the axial direction L with respect to the axial position of the end face 213. This configuration allows an appropriate discharge to be generated between the discharge rod end 511 and the discharge protrusion 210.

If the end position 521 on the base end side L2 in the axial direction L of the discharge rod end 511 is separated from the end face 213 on the base end side L2 in the axial direction L of the discharge protrusion 210 by more than 1 mm on the base end side L2 in the axial direction L, the following is of concern. That is, discharge may occur not only between the discharge rod end 511 and the discharge protrusion 210, but also between the discharge rod end 511 and the general part of the parallel part 212 located on the base end side L2 in the axial direction L of the discharge protrusion 210, which may cause an ignition delay.

As shown in FIG. 4, the second fuel nozzle 222 is formed in the general portion of the parallel portion 212 of the nozzle portion 21, at a position on the tip side L1 in the axial direction L from the position where the discharge protrusion 210 is formed. In this embodiment, the second fuel nozzle 222 is formed at a position between the end position of the base end side L2 in the axial direction L of the breathable member 26 and the end face of the tip side L1 in the axial direction L of the discharge protrusion 210.

(Combustion in surface combustion burner 1)
In the surface combustion burner 1, the combustion header 2 guides the fuel gas F and the combustion air A through separate paths up to just before the breathable member 26, and the fuel gas F and the combustion air A are mixed and burned on the surface of the breathable member 26. When combustion is performed in the surface combustion burner 1, the fuel gas F passes through the fuel pipe 4 and the fuel passage 20 of the combustion header 2, branches from the fuel passage 20 to a plurality of first fuel ejection ports 221 and second fuel ejection ports 222, and is ejected from the open tips of the fuel ejection ports 221, 222 of the nozzle portion 21, passing through the breathable member 26 from the inside to the outside in the radial direction R.

Meanwhile, the combustion air A passes through the air pipe 3 and branches into the multiple first air outlets 23 of the nozzle portion 21 of the combustion header 2 and the multiple second air outlets 241 of the flange portion 24 of the combustion header 2. The combustion air A is then ejected from the opening tips of the multiple first air outlets 23 of the nozzle portion 21, passes through the breathable member 26 from the inside to the outside in the radial direction R, and is ejected from the multiple second air outlets 241 of the flange portion 24, passing to the tip side L1 in the axial direction L of the combustion header 2.

The fuel gas F ejected from the first fuel nozzles 221 and the combustion air A ejected from the first air nozzles 23 move in the circumferential direction C near the surface of the breathable member 26 and mix with each other. In addition, near the surface of the breathable member 26, the fuel gas F ejected from the first fuel nozzles 221 and the combustion air A ejected from the first air nozzles 23 are mixed with the combustion air A ejected from the second air nozzles 241. This allows the fuel gas F and the combustion air A to be sufficiently mixed near the surface of the breathable member 26, making it difficult for the concentration of the fuel gas F in the mixture to become uneven.

The mixture of fuel gas F and combustion air A is ignited by a spark generated between the discharge rod end 511 of the spark rod 5 and the discharge protrusion 210 of the nozzle portion 21, and burns near the surface of the breathable member 26, forming a flame in the air tube 3. At this time, since there is little bias in the concentration of fuel gas F in the mixture, a stable flame can be formed.

(Action and Effect)
In the surface combustion burner 1 of this embodiment, the positions at which the discharge rod end 511 of the spark rod 5 and the discharge protrusion 210 of the nozzle portion 21 are formed are devised. Specifically, the discharge protrusion 210 is formed at a position facing the discharge rod end 511 in the radial direction R on the outer surface of the parallel portion 212 of the nozzle portion 21. The discharge rod end 511 is also disposed at a position facing the discharge protrusion 210 in the radial direction R. Furthermore, the multiple first fuel ejection holes 221 and second fuel ejection holes 222 are formed on the tip side L1 in the axial direction L relative to the position at which the discharge protrusion 210 is formed.

With these configurations, when a mixture of fuel gas F ejected from the multiple first fuel nozzles 221 of the nozzle portion 21 and combustion air A ejected from the multiple first air nozzles 23 of the nozzle portion 21 and the multiple second air nozzles 241 of the flange portion 24 is burned, the flame caused by the combustion near the surface of the breathable member 26 is less likely to come into contact with the discharge rod end 511. This makes it difficult for the spark rod 5 to heat up, and makes it possible to suppress deformation of the spark rod 5 due to overheating when it is ignited.

In addition, in this embodiment, the formation of the second fuel nozzle 222 prevents poor ignition by the spark rod 5 even in a configuration in which the discharge rod end 511 is shifted toward the base end side L2 in the axial direction L from the position where the flame is formed. In addition, the configuration of the discharge protrusion 210 in a band shape that is long in the circumferential direction C maintains the ignition performance of the spark rod 5 for a long period of time.

Therefore, the surface combustion burner 1 of this embodiment can improve the durability of the discharge rod end 511 of the spark rod 5.

The present invention is not limited to the embodiments, and further different embodiments can be constructed without departing from the spirit of the invention. The present invention also includes various modifications, modifications within the scope of equivalents, etc.

REFERENCE SIGNS LIST 1 Surface combustion burner 2 Combustion header 21 Nozzle portion 210 Discharge convex portion 211 Inclined portion 212 Parallel portion 221 First fuel nozzle 222 Second fuel nozzle 23 First air nozzle 24 Flange portion 241 Second air nozzle 26 Breathable member 3 Air pipe 4 Fuel pipe 5 Spark rod 511 Discharge rod end portion

Claims (4)

an air pipe through which combustion air passes;
a fuel pipe disposed within the air pipe and through which a fuel gas passes;
a combustion header connected to a tip end side of the fuel pipe in an axial direction along a central axis thereof and disposed within the air pipe, the combustion header having a nozzle portion and a flange portion provided on a base end side of the nozzle portion in the axial direction;
a breathable member provided on an outer surface of the nozzle portion and made of a fiber material or a porous material;
a spark rod disposed through the flange portion and having a discharge rod end disposed at a position facing an outer surface of the nozzle portion;
the nozzle portion is formed with a plurality of fuel outlets for ejecting the fuel gas and a plurality of first air outlets for ejecting the combustion air, and the flange portion is formed with a plurality of second air outlets for ejecting the combustion air,
a discharge protrusion is formed on an outer surface of the nozzle portion at a base end side in the axial direction at a position facing the discharge rod end,
A surface combustion burner, wherein the fuel ejection ports are formed on a tip side in the axial direction relative to a position where the discharge protrusion is formed. The surface combustion burner according to claim 1, wherein the discharge protrusion is formed in a band shape whose circumferential length around the central axis of the fuel tube is longer than its axial length. The surface combustion burner according to claim 1 or 2, wherein the multiple fuel ejection ports are composed of multiple first fuel ejection ports formed at multiple locations in the axial direction of the nozzle portion and in the circumferential direction around the central axis of the fuel tube, and a second fuel ejection port formed at a position that is closer to the base end in the axial direction than the positions where the multiple first fuel ejection ports are formed, closer to the tip end in the axial direction than the position where the discharge protrusion is formed, and overlaps with the arrangement position of the discharge rod end in the circumferential direction. the nozzle portion has a parallel portion parallel to the axial direction, and an inclined portion located on a tip side of the parallel portion in the axial direction, the inclined portion having a radial dimension about a central axis of the fuel pipe decreasing toward the tip side in the axial direction, and the air-permeable member is disposed in the inclined portion,
4. The surface combustion burner according to claim 1, wherein the discharge protrusion is formed continuously over the entire circumferential direction around the central axis of the fuel pipe in the parallel portion.

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