Totally aerated combustion burner

Abstract

Provided is a totally aerated combustion burner that has good lift resistance regardless of fuel gas types and can use both hydrocarbon gas and hydrogen gas as fuel gas.　The totally aerated combustion burner is provided with: a burner body (1) that has an air-fuel mixture chamber (11) which is supplied with an air-fuel mixture of fuel gas and primary air; and a combustion plate part (2) that covers an open surface of the burner body, facing the air-fuel mixture chamber. The combustion plate part includes: a frame-shaped burner framework (21); a sintered body sheet (23) which covers an opening part of the burner framework from the burner body side and which is obtained by sintering a laminate having metal fibers laminated therein; and a distribution plate (24) which, together with the burner framework, sandwiches the sintered body sheet and which has formed therein a large number of slit-shaped distribution holes (24a). A plurality of distribution hole rows comprising a plurality of distribution holes arranged at intervals in the Y-axis direction, which is the short direction of the distribution holes, are arranged side by side in the X-axis direction, which is the long direction. The slit width is set in a range of 0.3-0.6 mm, and the slit pitch is set in a range of 6-10 mm.

Description

All primary combustion burner

[0001] The present invention relates to an all-primary combustion burner, and more particularly to one that can use either hydrocarbon gas or hydrogen gas as fuel gas.

[0002] A conventional all-primary combustion burner using a hydrocarbon gas such as natural gas as the fuel gas is known, for example, as described in Patent Document 1. This burner 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 and having a number of flame holes arranged in a row. The mixture supplied to the mixture chamber is ejected and burned through the flame holes. Meanwhile, in recent years, hydrogen, which does not emit carbon dioxide, has been attracting attention as an alternative fuel to hydrocarbon gas to prevent global warming. However, a mixture of hydrogen gas and primary air has an extremely fast combustion rate. Therefore, when a mixture of hydrogen gas and primary air is burned in the above-mentioned conventional all-primary combustion burner, the mixture burns near the surface of the combustion plate portion, which tends to become hot, resulting in a problem of flashback, in which the flame propagates into the mixture chamber.

[0003] As a solution to the above problem, the present applicant has proposed in Japanese Patent Application No. 2022-86442 a full primary combustion burner having the following configuration: In this burner, the combustion plate section is composed of a frame-shaped burner frame, a sintered sheet made of a sintered laminate of metal fibers or metal beads that is provided 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 and the frame. During sintering, the metal fibers of this sintered sheet randomly intertwine and bond (weld), resulting in the formation of numerous complex microscopic gaps that are smaller than the pore size of the so-called flashback limit. Furthermore, there are few contact points between the metals, and the contact areas are small.

[0004] In the all-primary combustion burner, when a mixture of hydrogen gas and primary air is supplied to the mixture chamber, it passes through the distribution holes in the distribution plate and ejects from the numerous tiny gaps in the sintered body sheet, where it burns. A relatively long flame forms in the portion of the sintered body sheet facing the distribution holes. Meanwhile, in the portion of the sintered body sheet facing the portion of the distribution plate without distribution holes, a flame that is difficult to lift is formed due to the slow-flowing mixture that seeps through the numerous tiny gaps in the sintered body sheet. This flame-holding effect improves lift resistance. Even if the mixture burns near the surface of the combustion plate and the surface (combustion surface) of the combustion plate becomes hot, this heat is prevented from transferring to the back side of the sintered body sheet facing the mixture chamber. Furthermore, when the room-temperature mixture is ejected through the tiny gaps in the metal fibers or metal beads, the increased contact area with the mixture suppresses the temperature rise of the sintered body sheet itself. As a result, flashback is effectively suppressed.

[0005] The distribution plate used has a large number of slit-shaped distribution holes. The longitudinal direction of the distribution holes is the X-axis direction, and the transverse direction is the Y-axis direction. Typically, multiple distribution hole rows, each consisting of a large number of distribution holes spaced apart in the Y-axis direction, are arranged in parallel in the X-axis direction. However, when the fuel gas is changed to hydrocarbon gas and a mixture of hydrocarbon gas and primary air is burned, it has been found that lift resistance may deteriorate. Therefore, the inventors conducted extensive research and found that, particularly when the slit pitch, which is the distance between the sides of adjacent distribution holes in each distribution hole row in the Y-axis direction, becomes narrow, the flame formed in the portion of the sintered sheet facing the portion of the distribution plate without distribution holes tends to spread, impairing the flame-holding effect. In such cases, using combustion plates for hydrogen gas and hydrocarbon gas depending on the type of fuel gas results in a lack of versatility for the gas appliance.

[0006] Japanese Patent Application Laid-Open No. 2001-263614

[0007] The present invention was made based on the above findings, and its object is to provide an all-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.

[0008] In order to solve the above problems, the present invention provides an all-primary combustion burner comprising 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, wherein the combustion plate portion comprises a frame-shaped burner frame, a sintered sheet made of a sintered 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, and a plurality of distribution hole rows each 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 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 wherein either hydrocarbon gas or hydrogen gas can be used as the fuel gas.

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

[0010] If the slit width is less than 0.3 mm, the airflow resistance of the fuel gas and primary air mixture passing through each distribution hole in the distribution plate becomes too large. On the other hand, if the slit width is greater than 0.6 mm, the velocity of the fuel gas passing through each distribution hole decreases, and flashback may not 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. Furthermore, if the slit pitch is less than 6 mm, when the fuel gas is hydrocarbon gas, the flame formed on the portion of the sintered body sheet facing the portion of the distribution plate without distribution holes will extend, impairing the flame stabilization effect. On the other hand, if the slit pitch is greater than 10 mm, there is almost no change in the flame stabilization effect when the fuel gas is hydrocarbon gas. In fact, the slit pitch becomes too large, and there is a risk that the mixture will not be evenly supplied to almost the entire surface of the sintered body sheet. 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 also preferable that the distribution hole arrays include a first distribution hole array and a second distribution hole array 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 in the first distribution hole array, and that the first distribution hole arrays and the second distribution hole arrays are alternately arranged in parallel in the X-axis direction. This is advantageous in that it is possible to uniformize the heat distribution.

[0012] The present invention relates to a burner for a combustion chamber, a combustion chamber ...

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

[0014] 1 to 4, the all-primary combustion burner CB comprises 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 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 screws (not shown) to a flange Fb1 of a combustion housing Fb that houses a heat exchanger for a water heater (not shown) at the peripheral portion of the open surface 12 of the burner body 1, i.e., the 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 specifically illustrated or explained in detail, the water heater's control controller pre-stores combustion data tables (such as the opening of the needle valve that adjusts the flow rate of the fuel gas and the fan rotation speed) for when the fuel gas is hydrogen gas and when the fuel gas is hydrocarbon gas, and when the water heater is in use, various devices are controlled based on the specified data table depending on the type of fuel gas selected.

[0015] As shown in Figure 3, the combustion plate section 2 is composed of a burner frame 21 made of sheet metal and shaped like a long frame; a sintered body sheet (hereinafter referred to as the "first sintered body sheet 23") that covers a rectangular first opening 22 surrounded by the burner frame 21 from the burner body 1 side (above); and a distribution plate 24 with numerous distribution holes 24a that is disposed on the back surface (upper surface) of the first sintered body sheet 23, which is the upstream surface 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 that bends from the opening peripheral portion 21a toward the burner body 1 (above), and a frame flange portion 21c that protrudes outward from the upper end of the side plate portion 21b. The distribution plate 24 is then assembled by spot welding the peripheral portions of the first sintered body sheet 23 to the opening peripheral portion 21a of the burner frame 21 at regular intervals, with the back surface of the first sintered body sheet 23 overlapping the distribution plate 24. In this state, the first opening 22 is attached to the lower peripheral edge 13 of the burner body 1 via the frame flange 21c. The cross section of the first opening 22 along the front-rear direction is curved in an arc shape. Similarly, the cross section of the first sintered sheet 23 and the distribution plate 24 along the front-rear direction is also curved in an arc shape, in other words, they are formed into a curved shape that is convex toward the downstream side in the flow direction of the air-fuel mixture.

[0016] The first sintered sheet 23 is formed by sintering a laminate in which metal fibers 23a 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 primarily composed of Fe, and have a wire diameter in the range of 50 μm to 100 μm. Known methods such as hot pressing (hot processing), which simultaneously performs pressure molding and sintering, and HIP (hot isostatic pressing) can be used to manufacture the first sintered sheet 23. For example, when manufacturing by hot pressing, although not specifically illustrated or described, the metal fibers 23a are stacked in a mold cavity without weaving or knitting to form a laminate. In this case, the weight per unit area is 1200 g / m. ２ ~1800g / m ２ Next, pressure is applied to the laminate in one axial direction using a punch, and in this state the laminate is heated and held at a predetermined temperature via a mold. 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 air-fuel mixture.

[0017] As shown in the partially enlarged view in Figure 3, the first sintered sheet 23 manufactured as described above has numerous minute gaps 23b formed during sintering, whereby the metal fibers 23a are randomly entangled and bonded (welded) together, resulting in a complex structure with numerous minute gaps 23b smaller than the flashback limit pore size. This reduces the number of contact points between the metal fibers 23a and also reduces the area of ​​the contact points. In this case, the first sintered sheet 23 has a porosity ranging from 60% to 80% and a thickness of 0.5 mm to 3.0 mm. If the diameter of the metal fibers is less than 50 μm, the area where the metal fibers are entangled (contacting) during sintering increases, facilitating heat transfer to the back side of the sintered sheet 23. However, if the diameter is greater than 100 μm, the minute gaps 23b may become too large, potentially making it difficult to suppress flashback. Furthermore, when the fiber weight is 1200 g / m², the area where the metal fibers are entangled (contacting) increases during sintering, making it easier for heat to be transferred to the back side of the sintered sheet 23. 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. ２If the porosity is greater than this, the porosity will not fall within the above range, resulting in increased resistance to the passage of the air-fuel mixture. If the porosity is outside this 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 is formed by penetrating the plate in the thickness direction by, for example, punching, and has a slit-shaped outline. As shown in a partially enlarged view in Figure 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 is made up of a plurality of distribution holes 24a arranged at intervals in the Y-axis direction. 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. ２ and a first distribution hole row 24L. １ and the second distribution column 24L ２ The slit width Sw of each distribution hole 24a in the Y-axis direction 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 and the second distribution hole row 24L ２ The distance Sh between the one end of each distribution hole 24a and the other end of the distribution hole 24a in the X-axis direction is set appropriately, for example, taking into consideration the workability of each distribution hole 24a.

[0019] In this embodiment, a flashback suppression plate 3 is further disposed within the mixture chamber 11 to reliably prevent flashback when hydrogen gas is used as the fuel gas. 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. The frame 31 surrounds a second opening 32 having the same contour as the first opening 22. The second opening 32 is surrounded by the frame 31. The second opening 32 is provided to cover the second opening 32 from the opposite side (above) of the combustion plate 2. The second opening 32 is fabricated in the same manner as the first opening 22. The second opening 32 is fastened to the frame-shaped seat 15 formed within the mixture chamber 11 via the support frame 31 with screws (not shown). When the flashback suppression plate 3 is fastened, the second opening 33 faces the first opening 23 with a gap Gp between them. 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 when the combustion plate 2 is heated by a flame, the radiant heat from the combustion plate 2 will prevail and the flashback suppression plate 3 will be overheated, while if the gap is longer than 30 mm, a large amount of the air-fuel mixture will remain in the gap Gp between the combustion plate 2 and the flashback suppression plate 3, causing a loud noise when the flame propagates through the gap Gp.

[0020] In the all-primary combustion burner CB, the air-fuel mixture supplied from the inlet 14 of the burner body 1 into the air-fuel mixture chamber 11 passes through numerous small gaps (not shown) in the second sintered body sheet 33 and is supplied to the combustion plate 2. The air-fuel mixture passing through the second sintered body sheet 33 then passes through the gap Gp between the combustion plate 2 and the flashback suppression plate 3, passes through the distribution holes 24a of the distribution plate 24, and is ejected from the small gaps 23b of the sintered body sheet 23 of the combustion plate 2, resulting in all-primary combustion (combustion without secondary air). When the fuel gas is hydrogen gas, a relatively long flame is formed in the portion of the first sintered body sheet 23 facing the distribution holes 24a, while in the portion of the first sintered body sheet 23 facing the portion of the distribution plate 24 without the distribution holes 24a, a flame that is difficult to lift is formed due to the air-fuel mixture seeping through the small gaps 23b and having a slow ejection velocity. This flame stabilization improves lift resistance.

[0021] Furthermore, 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) of the combustion plate section becomes hot, the heat is less likely to be transmitted to the back side of the first sintered body sheet 23 facing the air-fuel mixture chamber. Furthermore, when the room-temperature air-fuel mixture is ejected through the minute gaps 23b in the metal fibers, the contact area with the air-fuel mixture is increased, thereby suppressing the temperature rise of the first sintered body sheet 23 itself. As a result, the fact that the first sintered body sheet 23 has only minute gaps and the back side of the first sintered body sheet 23 does not easily become hot effectively suppresses flashback. 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, the sintered body sheet 23 itself is less likely to distort when the combustion surface side of the first sintered body sheet 23 is heated, and this also suppresses the first sintered body sheet 23 from becoming locally hot and causing flashback.

[0022] On the other hand, when the fuel gas is a hydrocarbon gas, the flame formed on 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 this flame stabilization improves lift resistance. As such, the all-primary combustion burner CB of this embodiment has good lift resistance regardless of the type of fuel gas, and can be used with either hydrocarbon gas or hydrogen gas as the fuel gas without any special modifications to the combustion plate 2, improving the versatility of the gas appliance. Note that if the slit width Sw is less than 0.3 mm, the airflow resistance of the fuel gas and primary air mixture passing through each distribution hole 24a of the distribution plate 24 becomes too large. On the other hand, if the slit width Sw is greater than 0.6 mm, the velocity of the mixture passing through each distribution hole 24a decreases, potentially making it impossible to prevent flashback 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, respectively. 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 body 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 in fact the slit pitch will become larger, which may prevent the air-fuel mixture from being supplied evenly over almost the entire surface of the first sintered body sheet 23. Therefore, the lower and upper limits of the slit pitch Sp are set to 6 mm and 10 mm.

[0023] Furthermore, by disposing the flashback suppression plate 3 having the second sintered body sheet 33 as in this embodiment, the contact area with the room-temperature air-fuel mixture when it passes through the second sintered body sheet 33 is increased, thereby suppressing the temperature rise of the second sintered body sheet 33, i.e., the flashback suppression plate 3 itself. Furthermore, the formation of numerous minute gaps 33b also suppresses pressure loss. Therefore, even if a flame propagates into the gap Gp between the combustion plate 2 and the flashback suppression plate 3, the temperature rise of the flashback suppression plate 3 is suppressed, so the flashback suppression plate 3 can extinguish the flame. Furthermore, even if the flame propagating into the gap Gp remains unextinguished, the flashback suppression plate 3 has only the minute gap 23b, thereby suppressing its propagation upstream. As a result, by disposing an additional flashback suppression plate 3, flashback can be reliably suppressed.

[0024] Furthermore, the all-primary combustion burner CB may be configured as shown in Fig. 4, 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 into the gap Gp is ​​not extinguished and burns on the surface (lower surface) of the second sintered body sheet 33 facing the gap Gp, the temperature sensor 4 can detect the resulting temperature rise, and by, for example, stopping the supply of the mixture, the combustion that could damage the hydrogen combustion burner CB can be quickly stopped.

[0025] Although the above describes an embodiment of the present invention, 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 provided. However, for example, if a small amount of reducing agent is added to the air-fuel mixture to lower the flame temperature, components such as the flashback suppression plate 3 and the sensor 4 can be omitted. Furthermore, in the above embodiment, the first and second sintered body sheets 23, 33 are formed by sintering a laminate of metal fibers 23a, 33a. However, this is not limiting, as long as the sintered body can be formed into a complex structure with numerous minute gaps smaller than the flashback limit pore size. For example, a sintered body sheet can be formed by sintering a laminate of metal beads composed of Fe and at least one selected from Al, Cr, Mn, and Si or their carbides, with a particle size in the range of 50 μm to 500 μm, using the same method as above. In this case, the basis weight is 1200 g / m. ２ ~1800g / m ２ is set to the range.

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

Claims

1. A full primary combustion burner comprising a burner body having a mixture chamber to which a mixture of fuel gas and primary air is supplied, and a combustion plate covering the open surface of the burner body facing the mixture chamber, wherein the combustion plate comprises a frame-shaped burner frame, a sintered sheet made of a laminate of metal fibers or metal beads arranged 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, sandwiching 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 lateral 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 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 wherein either hydrocarbon gas or hydrogen gas can be used as the fuel gas.

2. A full primary combustion burner as described in 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 in 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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