Whole primary air combustion type burner

Abstract

To provide a whole primary air combustion type burner having excellent lift resistance regardless of the species of fuel gas, and capable of using either of hydrocarbon gas and hydrogen gas, as fuel gas.SOLUTION: The whole primary air combustion gas burner comprises: a burner body having an air-fuel mixture chamber to which an air-fuel mixture of fuel gas and primary air is fed; and a combustion plate covering an open face of the burner body facing the air-fuel mixture chamber. The combustion plate has: a frame-shaped burner frame 21; a sintered body sheet 23 prepared by sintering a laminate obtained by laminating metal fibers and covering an opening of the burner frame from the burner body side; and a distribution plate 24 with a plurality of slit-shaped distribution holes 24a formed thereon, sandwiching the sintered body sheet between itself and the burner frame. A plurality of distribution hole rows each consisting of the plurality of distribution holes arranged at intervals in a Y-axis direction which is a short side direction of the distribution holes are arranged in an X-axis direction which is a long side direction, with slit widths being set in a range of 0.3 mm to 0.6 mm and slit pitches being set in a range of 6 mm to 10 mm.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a full primary combustion burner, and more particularly to one that can use either hydrocarbon gas or hydrogen gas as the fuel gas. [Background technology]

[0002] Conventionally, as a full primary combustion burner using a hydrocarbon gas such as natural gas as the fuel gas, for example, the one described in Patent Document 1 is known. This burner is equipped with a burner body having a mixture chamber to which a mixture of fuel gas and primary air is supplied, and a combustion plate portion covering the open surface of the burner body facing the mixture chamber and having a number of flame holes arranged in a row. The mixture supplied to the mixture chamber is ejected and burned through each flame hole. Meanwhile, in recent years, hydrogen, which does not emit carbon dioxide, has been attracting attention as an alternative fuel to hydrocarbon gas in order to prevent global warming, but the mixture of hydrogen gas and primary air has a very fast combustion speed. Therefore, when the mixture of hydrogen gas and primary air is burned in the above-mentioned conventional full primary combustion burner, the mixture burns near the surface of the combustion plate portion, which tends to make the combustion plate portion hot, and there is a problem that a backfire is likely to occur in which the flame propagates into the mixture chamber.

[0003] As a solution to the above problem, the present patent applicant has proposed a full primary combustion burner having the following configuration in Japanese Patent Application No. 2022-86442. In this burner, the combustion plate portion is composed of a frame-shaped burner frame, a sintered sheet made by sintering a laminate of metal fibers or metal beads, which is provided so as to cover the opening surrounded by the burner frame from the burner body side, and a distribution plate that sandwiches the sintered sheet between the burner frame. In such a sintered sheet, the metal fibers are randomly entangled and bonded (welded) during sintering, resulting in the formation of countless minute gaps that are complex and smaller than the hole diameter of the so-called flashback limit, and moreover, there are few contact points between the metals, and the area of ​​the contact points is also small.

[0004] In the above-mentioned all-primary combustion burner, when a mixture of hydrogen gas and primary air is supplied into the mixture chamber, the mixture passes through each distribution hole of the distribution plate, is ejected from the numerous small gaps of the sintered sheet, and is burned. At this time, a relatively long flame is formed in the part of the sintered sheet facing each distribution hole. On the other hand, in the part of the sintered sheet facing the part of the distribution plate without distribution holes, a flame that is difficult to lift is formed by the mixture with a slow ejection speed that seeps out from the numerous small gaps of the sintered sheet, and the lift resistance is improved by the flame holding action of this flame. And even if the mixture burns near the surface of the combustion plate and the surface (combustion surface) side of the combustion plate becomes hot, the heat can be made difficult to transfer to the back side of the sintered sheet facing the mixture chamber, and further, when the mixture at room temperature is ejected through the small gaps of the metal fibers or metal beads, the contact area with the mixture is increased, and the temperature rise of the sintered sheet itself is also suppressed. As a result, backfire can be effectively suppressed.

[0005] The distribution plate used has a large number of slit-shaped distribution holes. The longitudinal direction of the distribution hole is the X-axis direction, and the lateral direction is the Y-axis direction. Usually, a plurality of distribution hole rows consisting of a large number of distribution holes arranged at intervals in the Y-axis direction are arranged in parallel in the X-axis direction. However, it was found that when the fuel gas is changed to a hydrocarbon gas and a mixture of the hydrocarbon gas and primary air is burned, the lift resistance may deteriorate. Then, the inventors conducted extensive research and found that, particularly when the slit pitch, which is the distance in the Y-axis direction between the sides of the distribution holes adjacent to each other in each distribution hole row, becomes narrow, the flame formed in the part of the sintered sheet facing the part of the distribution plate without distribution holes becomes easy to spread, and the flame holding effect is impaired. In such a case, if the combustion plate part is used separately for hydrogen gas and for hydrocarbon gas according to the type of fuel gas, there is a problem that the versatility of the gas appliance is lacking. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2001-263614 A Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention was made based on the above findings, and its object is to provide a full primary combustion burner that has good lift resistance regardless of the type of fuel gas and can be used with either hydrocarbon gas or hydrogen gas as fuel gas. [Means for solving the problem]

[0008] In order to solve the above problems, the all-primary combustion burner of the present invention includes a burner body having a mixture chamber to which a mixture of fuel gas and primary air is supplied, and a combustion plate portion covering the open surface of the burner body facing the mixture chamber, the combustion plate portion having a frame-shaped burner frame, a sintered sheet made of a laminate of metal fibers or metal beads, which is provided so as to cover the opening surrounded by the burner frame from the burner body side, and a distribution plate having a large number of slit-shaped distribution holes formed therein, which sandwiches the sintered sheet between the burner frame and the burner frame, the longitudinal direction of the distribution holes being the X-axis direction and the short side direction being the Y-axis direction, a plurality of distribution hole rows consisting of a plurality of distribution holes arranged at intervals in the Y-axis direction are arranged in parallel in the X-axis direction, the slit width of each distribution hole in the Y-axis direction is in the range of 0.3 mm to 0.6 mm, and the slit pitch between the sides of the distribution holes adjacent to each other in each distribution hole row is in the range of 6 mm to 10 mm, and both hydrocarbon gas and hydrogen gas can be used as the fuel gas.

[0009] According to the present invention, even when a hydrocarbon gas is used as the fuel gas, the flame formed in the portion of the sintered sheet facing the portion of the distribution plate without the distribution holes is prevented from spreading, and the flame holding effect of this flame improves the lift resistance. As a result, the device has good lift resistance regardless of the type of fuel gas, and can use either a hydrocarbon gas or a hydrogen gas as the fuel gas without any special modification of the combustion plate.

[0010] Here, if the slit width is smaller than 0.3 mm, the air flow resistance when the mixture of fuel gas and primary air passes through each distribution hole of the distribution plate becomes too large. On the other hand, if the slit width is larger than 0.6 mm, the speed when passing through each distribution hole decreases, and there is a risk that flashback cannot be prevented when the fuel gas is hydrogen gas. Therefore, the lower and upper limits of the slit width are set to 0.3 mm and 0.6 mm. Also, if the slit pitch is smaller than 6 mm, when the fuel gas is hydrocarbon gas, the flame formed in the part of the sintered body sheet facing the part of the distribution plate without distribution holes will spread, and the flame holding effect will be impaired. On the other hand, even if the slit pitch is larger than 10 mm, there is almost no change in the flame holding effect when the fuel gas is hydrocarbon gas, and rather the slit pitch becomes too large, and there is a risk that the mixture cannot be evenly supplied to the sintered body sheet over its entire surface. Therefore, the lower and upper limits of the slit pitch are set to 6 mm and 10 mm.

[0011] In the present invention, it is preferable that the distribution hole row includes a first distribution hole row and a second distribution hole row in which the position of each distribution hole is shifted from the position of each distribution hole of the first distribution hole row by a half pitch in the Y-axis direction, and the first distribution hole row and the second distribution hole row are alternately arranged in parallel in the X-axis direction. This is advantageous in that it is possible to uniformize the heat distribution. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a cross-sectional view showing the full primary combustion burner of the present embodiment installed in a combustion case. [Diagram 2] FIG. 2 is a perspective view of the all-primary combustion burner shown in FIG. 1. [Diagram 3] FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, with reference to the drawings, an embodiment of the all-primary combustion burner CB of the present invention that can use either hydrocarbon gas or hydrogen gas as fuel gas will be described. Note that the "hydrogen" in the present invention is not limited to pure hydrogen, and also includes, for example, the case where a small amount of odorant is added to give an odor.

[0014] 1 to 4, the all-primary combustion burner CB includes a burner body 1 having a mixture chamber 11 to which a mixture of fuel gas and primary air is supplied, and a combustion plate portion 2 covering a downward open surface 12 of the burner body 1 facing the mixture chamber 11. The all-primary combustion burner CB is fastened by a screw (not shown) to a flange portion Fb1 of a combustion housing Fb in which a heat exchanger for a water heater (not shown) is housed at a peripheral portion of the open surface 12 of the burner body 1, i.e., a lower peripheral portion 13, and is used to heat the heat exchanger. The burner body 1 also has an inlet 14 through which the mixture is supplied by a fan (not shown). Although not particularly shown or described in detail, the controller of the water heater stores in advance a combustion data table (such as the opening degree of a needle valve that adjusts the flow rate of the fuel gas and the rotation speed of the fan) for a case in which the fuel gas is hydrogen gas and a case in which the fuel gas is hydrocarbon gas, and when the water heater is used, various devices are controlled based on a predetermined data table according to the selected fuel gas type.

[0015] As shown in Fig. 3, the combustion plate section 2 is composed of a burner frame 21 made of sheet metal and in the shape of a long frame in one direction, a sintered body sheet (hereinafter referred to as "first sintered body sheet 23") provided so as to cover the rectangular first opening 22 surrounded by the burner frame 21 from the burner body 1 side (upper side), and a distribution plate 24 in which a large number of distribution holes 24a are formed, which is arranged to be superimposed on the back surface (upper surface) of the first sintered body sheet 23, which is the surface on the upstream side in the flow direction of the mixed gas. The burner frame 21 has an opening peripheral portion 21a located on the same plane as the first opening 22, a side plate portion 21b bent from the opening peripheral portion 21a to the burner body 1 side (upper side), and a frame flange portion 21c extending outward from the upper end of the side plate portion 21b. Then, with the distribution plate 24 superimposed on the back surface of the first sintered body sheet 23, these peripheral portions are spot-welded to the opening peripheral portion 21a of the burner frame 21 at regular intervals to be assembled. In this state, it is attached to the lower peripheral edge 13 of the burner body 1 via the frame flange portion 21c. The first opening 22 has a cross-sectional shape along the front-rear direction curved in an arc. Similarly, the first sintered sheet 23 and the distribution plate 24 also have cross-sectional shapes along the front-rear direction curved in an arc, in other words, they are formed into a curved shape that is convex toward the downstream side in the flow direction of the mixture gas.

[0016] The first sintered sheet 23 is a sintered laminate of metal fibers 23a, which are stacked without weaving or knitting. The metal fibers 23a are composed of Fe and at least one selected from Al, Cr, Mn, and Si, or carbides thereof, such as stainless steel fibers mainly composed of Fe, and have a wire diameter in the range of 50 μm to 100 μm. The first sintered sheet 23 can be produced by known methods such as hot pressing (hot processing method) and HIP (Hot Isostatic Pressing), which simultaneously perform pressure molding and sintering. For example, when producing by hot pressing, although not particularly illustrated and described, the metal fibers 23a are stacked in the cavity of a mold without weaving or knitting to produce a laminate. At this time, the weight per unit area is 1200 g / m 2 ~1800g / m 2Next, pressure is applied to the laminate from one axial direction by a punch, and in this state, the laminate is heated and held at a predetermined temperature via a die. At this time, the first sintered sheet 23 is formed into a curved shape that is convex toward the downstream side in the flow direction of the mixture gas.

[0017] As shown in a partially enlarged view in FIG. 3, the first sintered sheet 23 manufactured as described above has numerous minute gaps 23b that are complex and smaller than the pore size of the flashback limit, as the metal fibers 23a are randomly entangled and bonded (welded) during sintering, and the number of contact points between the metal fibers 23a is small, and the area of ​​the contact points is also small. In this case, the first sintered sheet 23 has a porosity in the range of 60% to 80% and a plate thickness of 0.5 mm to 3.0 mm. If the wire diameter of the metal fibers is smaller than 50 μm, the area where the metal fibers are entangled (contacted) during sintering increases, making it easier for heat to be transferred to the back side of the sintered sheet 23, while if the wire diameter is larger than 100 μm, the minute gaps 23b become too large and there is a risk that flashback cannot be suppressed. In addition, the weight per unit area is 1200 g / m 2 If it is less than 1800 g / m, there is a risk that each minute gap 23b becomes too large and flashback cannot be suppressed. 2 If the porosity is larger than the above range, the porosity will not be within the above range, and the resistance to the passage of the air-fuel mixture will increase. If the porosity is outside the above range, the pressure loss when the air-fuel mixture passes through the sintered sheet 23 will increase.

[0018] The distribution plate 24 is made of sheet metal, and each distribution hole 24a formed by penetrating the plate in the thickness direction by punching, for example, has a slit-shaped outline. As shown in a partially enlarged view in FIG. 3, the longitudinal direction of the distribution hole 24a is the X-axis direction, and the lateral direction is the Y-axis direction, and a distribution hole row 24L consisting of a plurality of distribution holes 24a arranged at intervals in the Y-axis direction is formed. 1 ,24L 2 In this case, the first distribution hole row 24L is 1 The positions of the distribution holes 24a are in the first distribution hole row 24L. 1 The second distribution hole row 24L is shifted by half a pitch in the Y-axis direction from the positions of the distribution holes 24a. 2The first distribution hole row 24L 1 and the second distribution column 24L 2 The slit width Sw in the Y-axis direction of each distribution hole 24a is set in the range of 0.3 mm to 0.6 mm, and each distribution hole row 24L 1 ,24L 2 The slit pitch Sp between the sides of adjacent distribution holes 24a is set in the range of 6 mm to 10 mm. 1 One end of the distribution hole 24a of the first distribution hole row 24L 2 The distance Sh between one end of each distribution hole 24a and the corresponding distribution hole 24a in the X-axis direction is appropriately set, for example, in consideration of the workability of each distribution hole 24a.

[0019] In this embodiment, in order to reliably prevent flashback when hydrogen gas is used as the fuel gas, a flashback suppression plate 3 is further disposed in the mixture chamber 11. As shown in FIG. 4, the flashback suppression plate 3 includes a frame-shaped support frame 31 made of sheet metal and extending in one direction, and a sintered body sheet (hereinafter referred to as the "second sintered body sheet 33") different from the first sintered body sheet 23, which is provided so as to cover the second opening 32, which has the same contour as the first opening 22 and is surrounded by the support frame 31, from the opposite side (upper side) of the combustion plate 2. The second sintered body sheet 33 is manufactured in the same manner as the first sintered body sheet 23. The second sintered body sheet 33 is fastened to the frame-shaped seat 15 formed in the mixture chamber 11 via the support frame 31 with screws (not shown). When the flashback suppression plate 3 is fastened, the second sintered body sheet 33 faces the first sintered body sheet 23 with a gap Gp. The gap Gp between the two sintered sheets 23, 33 is set in the range of 5 mm to 30 mm. If the gap is shorter than 5 mm, there is a risk that the radiant heat from the combustion plate 2 will be dominant when the combustion plate 2 is heated by a flame, and the flashback suppression plate 3 will be overheated, while if the gap is longer than 30 mm, the amount of air-fuel mixture that remains in the gap Gp between the combustion plate 2 and the flashback suppression plate 3 will increase, and a loud noise will be generated when the flame propagates through the gap Gp.

[0020] In the above-mentioned full primary combustion burner CB, the mixture gas supplied from the inlet 14 of the burner body 1 into the mixture chamber 11 passes through numerous small gaps (not shown) of the second sintered body sheet 33 and is supplied to the combustion plate section 2. Then, the mixture gas that has passed through the second sintered body sheet 33 passes through the gap Gp between the combustion plate section 2 and the flashback suppression plate section 3, passes through each distribution hole 24a of the distribution plate 24, and is ejected from each small gap 23b of the sintered body sheet 23 of the combustion plate section 2, and full primary combustion (combustion that does not require secondary air) occurs. At this time, when the fuel gas is hydrogen gas, a relatively long flame is formed in the part of the first sintered body sheet 23 facing each distribution hole 24a, while a flame that is difficult to lift is formed by the mixture gas that seeps out from the small gap 23b at a slow ejection speed in the part of the first sintered body sheet 23 facing the part of the distribution plate 24 without the distribution hole 24a, and the lift resistance is improved by the flame holding action of this flame.

[0021] In addition, even if the air-fuel mixture burns near the surface of the first sintered body sheet 23 of the combustion plate section 2 and the surface (combustion surface) side of the combustion plate section becomes hot, the heat is unlikely to be transferred to the back side of the first sintered body sheet 23 facing the air-fuel mixture chamber, and when the air-fuel mixture at room temperature is ejected through the minute gaps 23b of the metal fibers, the contact area with the air-fuel mixture is increased, so that the temperature rise of the first sintered body sheet 23 itself is also suppressed. As a result, the first sintered body sheet 23 has only minute gaps, and the back side of the first sintered body sheet 23 is unlikely to become hot, which effectively suppresses backfire. At this time, since the first sintered body sheet 23 is formed into a curved shape that is convex toward the downstream side in the flow direction of the air-fuel mixture, when the combustion surface side of the first sintered body sheet 23 is heated, the sintered body sheet 23 itself is unlikely to be distorted, and the first sintered body sheet 23 is unlikely to become locally hot and cause backfire.

[0022] On the other hand, when the fuel gas is a hydrocarbon gas, the flame formed in the portion of the first sintered sheet 23 facing the portion of the distribution plate 24 without the distribution holes 24a is less likely to spread, and the flame holding action of this flame improves the lift resistance. In this way, the all-primary combustion burner CB of this embodiment has good lift resistance regardless of the type of fuel gas, and can use either hydrocarbon gas or hydrogen gas as the fuel gas without any special modification of the combustion plate part 2, thereby improving the versatility of the gas appliance. If the slit width Sw is smaller than 0.3 mm, the air flow resistance when the mixture of the fuel gas and the primary air passes through each distribution hole 24a of the distribution plate 24 becomes too large. On the other hand, if the slit width Sw is larger than 0.6 mm, the speed when passing through each distribution hole 24a decreases, and there is a risk that flashback cannot be prevented when the fuel gas is hydrogen gas. Therefore, the lower and upper limits of the slit width Sw are set to 0.3 mm and 0.6 mm. Furthermore, if the slit pitch Sp is smaller than 6 mm, when the fuel gas is a hydrocarbon gas, the flame formed in the part of the first sintered sheet 23 facing the part of the distribution plate 24 without the distribution holes 24a will spread, impairing the flame stabilization effect. On the other hand, even if the slit pitch Sp is larger than 10 mm, there will be almost no change in the flame stabilization effect when the fuel gas is a hydrocarbon gas, and instead the slit pitch will become larger, and there is a risk that the mixture cannot be supplied evenly over almost the entire surface of the first sintered sheet 23. Therefore, the lower and upper limits of the slit pitch Sp are set to 6 mm and 10 mm.

[0023] In addition, if the flashback suppression plate 3 having the second sintered sheet 33 is arranged as in this embodiment, the contact area with the air-fuel mixture at room temperature when it passes through the second sintered sheet 33 is increased, thereby suppressing the temperature rise of the second sintered sheet 33, i.e., the flashback suppression plate 3 itself. Moreover, since a countless number of minute gaps 33b are formed, pressure loss is also suppressed. Therefore, even if a flame propagates to the gap Gp between the combustion plate 2 and the flashback suppression plate 3, the flashback suppression plate 3 can extinguish the flame because the temperature rise of the flashback suppression plate 3 is suppressed. Furthermore, even if the flame propagated to the gap Gp remains without being extinguished, the flashback suppression plate 3 has only the minute gap 23b, so that the propagation to the upstream side is suppressed. As a result, if the flashback suppression plate 3 is further arranged, flashback can be reliably suppressed.

[0024] Furthermore, in the all-primary combustion burner CB, as shown in Fig. 4, a configuration may be adopted in which a temperature sensor 4 is disposed in the portion of the mixture chamber 11 located between the combustion plate portion 2 and the flashback suppression plate portion 3. Known devices such as a thermocouple or a bimetal switch can be used as the temperature sensor 4. In this way, if the flame that has propagated to the gap Gp is ​​not extinguished and burns on the surface (lower surface) of the second sintered sheet 33 facing the gap Gp, the temperature rise caused by this can be detected by the temperature sensor 4, and the supply of the mixture can be stopped, for example, to quickly stop the combustion that would damage the hydrogen combustion burner CB.

[0025] Although the embodiment of the present invention has been described above, various modifications are possible without departing from the scope of the technical concept of the present invention. In the above embodiment, the flashback suppression plate 3 and the sensor 4 are further arranged, but in the case where a small amount of reducing agent is added to the air-fuel mixture to lower the flame temperature, the flashback suppression plate 3 and the sensor 4 can be omitted. In the above embodiment, the first and second sintered sheets 23, 33 are formed by sintering a laminate in which metal fibers 23a, 33a are laminated, but the present invention is not limited to this, as long as a complex and numerous minute gaps smaller than the pore size of the flashback limit can be formed after sintering. For example, a sintered sheet can be formed by sintering a laminate in which metal beads are laminated by the same method as above, using metal beads composed of Fe and at least one selected from Al, Cr, Mn, and Si or carbides thereof, and having a particle size in the range of 50 μm to 500 μm. In this case, the weight per unit area is 1200 g / m. 2 ~1800g / m 2 is set to the range. [Explanation of symbols]

[0026] CB...Full primary combustion burner, 1...burner body, 11...air-fuel mixture chamber, 12...open surface, 2...combustion plate portion, 21...burner frame, 23...sintered sheet, 24...distribution plate, 24a...distribution hole, 24L 1 ,24L 2 …Each distribution hole row

Claims

1. A full primary combustion burner including a burner body having a mixture chamber to which a mixture of fuel gas and primary air is supplied, and a combustion plate portion covering an open surface of the burner body facing the mixture chamber, The combustion plate portion includes a frame-shaped burner frame, a sintered sheet formed by sintering a laminate of metal fibers or metal beads, the sintered sheet being provided so as to cover an opening surrounded by the burner frame from the burner body side, and a distribution plate having a large number of slit-shaped distribution holes formed therein and sandwiching the sintered sheet between the burner frame and the distribution plate, A full primary combustion burner characterized in that a plurality of distribution hole rows are arranged in parallel in the X-axis direction, each row consisting of a plurality of distribution holes arranged at intervals in the Y-axis direction, with the longitudinal direction of the distribution hole being the X-axis direction and the short side direction being the Y-axis direction, the slit width of each distribution hole in the Y-axis direction being in the range of 0.3 mm to 0.6 mm, and the slit pitch between the sides of adjacent distribution holes in each distribution hole row being in the range of 6 mm to 10 mm, and that either hydrocarbon gas or hydrogen gas can be used as the fuel gas.

2. 2. The all-primary combustion burner according to claim 1, characterized in that the distribution hole rows include a first distribution hole row and a second distribution hole row in which the positions of the distribution holes are shifted by half a pitch in the Y-axis direction from the positions of the distribution holes of the first distribution hole row, and the first distribution hole row and the second distribution hole row are alternately arranged in parallel in the X-axis direction.

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