Gas burner and heating cooker

Abstract

This gas burner includes: a burner body 4 rising from a downstream end of a gas inflow pipe 3; and a burner head 5 placed on the burner body 4. The burner body 4 has therein a distribution chamber 42 into which gas flows through the gas inflow pipe 3. The burner head 5 has an exposed annular wall 51 on an outer peripheral surface of the burner head. A plurality of flame holes 52a for ejecting gas from the distribution chamber 42 are provided to the annular wall at intervals in a circumferential direction. In the gas burner, manufacturing control of the burner head 5 is facilitated, and combustion performance including backfire suppression performance can be stabilized.　The burner head 5 has therein a distribution passage 53 for distributing gas from the distribution chamber 42 to the flame hole. A backfire suppression member 54 composed of a porous body made from metal or ceramic is interposed in the distribution passage 53 so that the gas passing through the backfire suppression member 54 is distributed to the flame holes 52a.

Description

Gas burners and cooking appliances

[0001] The present invention relates to a gas burner suitable for using hydrogen gas as fuel gas, which includes a burner body rising from the downstream end of a gas inlet pipe and a burner head placed on the burner body, and to a cooking appliance equipped with this gas burner.

[0002] Originally, this type of gas burner had a burner body with a distribution chamber inside, into which gas flows via a gas inlet pipe, and a burner head with an annular wall exposed on the outer periphery of the burner head, with a plurality of flame holes spaced apart in the circumferential direction to eject the gas from the distribution chamber. Furthermore, when hydrogen gas is used as the fuel gas, it is necessary to take measures against flashback because of the extremely fast combustion speed.

[0003] As a countermeasure against such flashbacks, a stack of partition plates is arranged in the burner head with gaps in the vertical direction, and gas from the distribution chamber is ejected from the flame holes through the gaps between the partition plates of the stack, as disclosed in Patent Document 1. In this system, flashbacks can be suppressed by making the gaps between the partition plates equal to or smaller than the quenching distance.

[0004] However, with this method, it becomes difficult to control the gaps between the partition plates after the stack is installed in the burner head. If the gaps between the partition plates are too narrow, the amount of gas ejected from the flame holes will decrease due to pressure loss. Conversely, if the gaps between the partition plates are too wide, the effect of suppressing flashback will decrease. As a result, it becomes difficult to stabilize combustion performance.

[0005] Japanese Patent Application Laid-Open No. 2021-124271

[0006] In view of the above, the present invention aims to provide a gas burner that facilitates manufacturing control of the burner head and stabilizes combustion performance, including backfire suppression performance, as well as a heating cooker equipped with this gas burner.

[0007] In order to solve the above problems, a first invention of the present application is a gas burner comprising a burner body rising from the downstream end of a gas inlet pipe and a burner head mounted on the burner body, the burner body having an internal distribution chamber into which gas flows via the gas inlet pipe, the burner head having an annular wall exposed on the outer circumferential surface of the burner head, and a plurality of flame holes for ejecting gas from the distribution chamber at intervals in the circumferential direction, the burner head having an internal distribution passage for distributing gas from the distribution chamber to the flame holes, and a flashback suppression member made of a porous material made of metal or ceramic interposed in the distribution passage, so that the gas passing through the flashback suppression member is distributed to the flame holes. Also, a second invention of the present application is a cooking appliance comprising the gas burner of the first invention.

[0008] According to the present invention (first invention), the flashback suppression member is made of a porous material, and therefore, unlike the laminated body of partition plates in the above-mentioned conventional example, there is no variation in the gas permeability of the flashback suppression member. Furthermore, because such a flashback suppression member is interposed in the distribution passage within the burner head, manufacturing control of the burner head is easier, and there is no decrease in the amount of gas ejected from the flame holes or in the flashback suppression effect. Therefore, combustion performance can be stabilized.

[0009] In the present invention, the burner holes are preferably formed so that the opening area of ​​the burner holes relative to the outer peripheral surface of the annular wall is larger than the opening area of ​​the burner holes relative to the inner peripheral surface of the annular wall. This makes the density of gas ejected from the burner holes on the outer peripheral surface of the annular wall lower than the density of gas flowing into the burner holes on the inner peripheral surface of the annular wall. This reduces the energy density at the burner holes during ignition, thereby reducing the noise during ignition.

[0010] However, when wind blows toward a burner hole from the outside, the wind may pass from one burner hole to another through the space inside the burner head, causing a flashback. Therefore, in the present invention, it is desirable that the flashback suppression member be formed in an annular shape, and that the outer circumferential surface of the flashback suppression member abut against or closely face the inner circumferential surface of the annular wall. In this way, the flashback suppression member functions as an obstacle that prevents wind from passing through the space inside the burner head. Therefore, flashbacks caused by wind passing through can be suppressed.

[0011] In this case, it is also desirable to provide the burner head with a plurality of stoppers spaced apart in the circumferential direction that abut against or closely face the inner circumferential surface of the flashback suppression member, so that even if a user pushes the flashback suppression member inward during maintenance, the flashback suppression member will not fall off into the burner.

[0012] Furthermore, it is desirable that the stopper portion be provided at a circumferential position that coincides with the burner hole. In this way, even if a hole is made in the flashback suppression member by inserting a rod-shaped cleaning tool into the burner hole to clean the burner hole, the hole will be closed by the stopper portion. Therefore, the flashback suppression effect will not be impaired.

[0013] Furthermore, in the present invention, if the gas flowing in from the gas inlet pipe is fuel gas that is not mixed with primary air and is ejected from the flame holes for diffusion combustion, flashback can be more effectively suppressed even if the fuel gas is hydrogen gas.

[0014] 1 is a perspective view of a main part of a cooking device equipped with a gas burner according to an embodiment of the present invention; 2 is a cross-sectional side view taken along line II-II in Fig. 1; 3 is a cross-sectional front view taken along line III-III in Fig. 2; 4 is a cross-sectional plan view taken along line IV-IV in Fig. 2; 5 is a perspective view of an exploded state of the gas burner according to an embodiment of the present invention;

[0015] 1 to 3 show a cooking appliance equipped with a gas burner A according to an embodiment of the present invention. The cooking appliance has a top plate 1 that covers the top surface of a cooking appliance body (not shown). A trivet 2 having a plurality of trivet claws 21 is placed on the top plate 1 so as to surround a burner opening 11 that faces the gas burner A provided in the top plate 1. The gas burner A is also provided with an ignition electrode Aa and a thermocouple Ab for flame detection.

[0016] The gas burner A comprises an annular burner body 4 supported by a support frame 12 fixed to the cooking appliance body and rising from the downstream end of a gas inlet pipe 3 located under the top plate 1 toward a burner opening 11, and an annular burner head 5 placed on the burner body 4. The upstream end of the gas inlet pipe 3 is connected to a gas outlet 31a of a casing 31 of a fuel gas valve unit. A gas nozzle 32 for injecting fuel gas is provided at the downstream end of the valve unit, which communicates with the gas outlet 31a. Therefore, the gas flowing into the gas inlet pipe 3 is fuel gas without primary air being mixed in. Hydrogen gas is used as the fuel gas. Note that "hydrogen" includes not only pure hydrogen but also hydrogen containing small amounts of additives for flavoring, etc.

[0017] A port portion 41 is protruding from one location on the periphery of the lower part of the burner body 4. The port portion 41 has a connection port 41a for a joint 33 provided at the downstream end of the gas inlet pipe 3. The burner body 4 has an annular distribution chamber 42 inside, into which gas (fuel gas) from the gas inlet pipe 3 flows. The burner head 5 has an annular wall 51 exposed to the outer circumferential surface of the burner head 5. This annular wall 51 has a plurality of flame holes 52 spaced apart in the circumferential direction, through which the gas (fuel gas) from the distribution chamber 42 is ejected. The fuel gas is ejected from the flame holes 52 and undergoes diffusion combustion. Small flame holes 52a for flame holding and flame transfer are provided between circumferentially adjacent flame holes 52, 52. The burner head 5 also has a distribution passage 53 inside, which distributes gas from the distribution chamber 42 to the flame holes 52 and the small flame holes 52a.

[0018] As shown in Figure 4, the burner holes 52 are formed so that the opening area of ​​the burner holes relative to the outer peripheral surface of the annular wall 51 is larger than the opening area of ​​the burner holes relative to the inner peripheral surface of the annular wall 51. This makes the density of gas ejected from the burner holes 52 (the amount of gas per unit area) on the outer peripheral surface side of the annular wall 51 lower than the density of gas flowing into the burner holes 52 on the inner peripheral surface side of the annular wall 51. The lower density of the ejected gas reduces the energy density at the burner holes 52 during ignition, thereby reducing the noise during ignition. In this embodiment, the circumferential length of the burner holes 52 is longer on the outer peripheral surface side of the annular wall 51 than on the inner peripheral surface side. However, it is also possible to make the vertical width of the burner holes 52 larger on the outer peripheral surface side of the annular wall 51 than on the inner peripheral surface side, so that the opening area of ​​the burner holes relative to the outer peripheral surface of the annular wall 51 is larger than the opening area of ​​the burner holes relative to the inner peripheral surface of the annular wall 51.

[0019] The structure of the burner head 5 will be described in more detail with reference to Figure 5. The burner head 5 is composed of three upper and lower members: an annular lower member 5L that contacts the burner body 4, an annular intermediate member 5M that is placed on the lower member 5L, and an annular upper member 5U that covers the intermediate member 5M from above. These three members 5L, 5M, and 5U are fastened together by short screws 5a at two circumferential locations near the inner periphery to form the burner head 5. The assembled burner head 5 is then fastened to the burner body 4 by long screws 5b at two circumferential locations near the inner periphery that are out of phase with the short screws 5a.

[0020] An outer cylindrical portion 5La and an inner cylindrical portion 5Lb are vertically attached to the lower surface of the lower member 5L, and are fitted to the outer and inner peripheries of the burner body 4. The lower member 5L is also formed with a plurality of arc-shaped through-holes 531 at intervals in the circumferential direction, which penetrate the lower member 5L in the vertical direction and communicate with the distribution chamber 42. The upper portions of the through-holes 531 are continuous in the circumferential direction and have an annular shape.

[0021] The upper surface of the intermediate member 5M is provided with the above-mentioned annular wall 51, which is located on the outer periphery and has the flame holes 52, and further formed with a downwardly recessed annular groove 532 located between the annular wall 51 and the inner half. The intermediate member 5M also has a plurality of communicating holes 533, which are arc-shaped in plan view and open into the inner periphery of the groove 532, formed at intervals in the circumferential direction and communicate with the through hole 531 of the lower member 5L. The distribution passage 53 is composed of the through hole 531, the communicating holes 533, and the groove 532.

[0022] In the gas burner A of this embodiment, as described above, fuel gas is ejected from the flame holes 52 for diffusion combustion, so that even if the fuel gas is hydrogen gas, flashback into the burner can be suppressed during combustion. However, since the distribution passage 53 and the distribution chamber 42 are replaced with air when not in use, when fuel gas flows in from the gas inlet pipe 3 during ignition, a mixture of fuel gas and air is generated in the distribution passage 53 and the distribution chamber 42, which may cause flashback inside the burner. Therefore, in this embodiment, a flashback suppression member 54 is provided in the distribution passage 53 so that the gas that passes through the flashback suppression member 54 is distributed to the flame holes 52.

[0023] The flashback suppression member 54 is made of a porous material made of metal or ceramic. Specifically, the flashback suppression member 54 is made of a porous material with numerous minute gaps less than the quenching distance, such as a sintered body made by sintering a laminate of metal fibers or metal beads, a knitted body made by knitting metal fibers, or porous ceramic. The flashback suppression member 54 made of such a porous material does not exhibit variation in gas permeability. Furthermore, because the flashback suppression member 54 is interposed in the distribution path 53 within the burner head 5, manufacturing control of the burner head 5 is facilitated, and there is no decrease in the amount of gas ejected from the flame holes 52 or in the flashback suppression effect. Therefore, combustion performance can be stabilized.

[0024] Incidentally, when wind blows toward the burner holes 52 from the outside, the wind may pass from one burner hole 52 to another burner hole 52 through the space within the burner head 5, causing a flashback. Therefore, in this embodiment, an annular flashback suppression member 54 is installed in the groove 532 of the distribution path 53 so that its outer circumferential surface abuts against the inner circumferential surface of the annular wall 51. This allows the flashback suppression member 54 to function as an obstacle that prevents the wind from passing through the space within the burner head 5, thereby suppressing flashbacks caused by the wind passing through. Note that even if the outer circumferential surface of the flashback suppression member 54 does not abut against the inner circumferential surface of the annular wall 51, a similar effect can be obtained as long as it is closely opposed to the inner circumferential surface of the annular wall 51 with only a small gap between them.

[0025] The burner head 5 is provided with a plurality of stopper portions 55 spaced apart in the circumferential direction, positioned in the recessed groove 532 of the intermediate member 5M and abutting against the inner circumferential surface of the flashback suppression member 54. The stopper portions 55 may be located closely opposite the inner circumferential surface of the flashback suppression member 54. By providing the stopper portions 55 in this manner, even if a user inserts a rod-shaped cleaning tool for cleaning the flame hole into the flame hole 52 during maintenance to push the flashback suppression member 54 inward, the flashback suppression member 54 will not fall off into the burner.

[0026] Furthermore, if a rod-shaped cleaning tool for cleaning the flame holes is inserted too forcefully into the flame holes 52, a hole may be created in the flashback suppression member 54. Therefore, the stopper portion 55 is provided at a circumferential position that coincides with the flame holes 52. With this, even if a hole is created in the flashback suppression member 54 as described above, the hole will be blocked by the stopper portion 55. Therefore, the flashback suppression effect will not be impaired. The circumferential length of the stopper portion 55 is slightly longer than the circumferential length of the flame holes 52 on the inner circumferential surface of the annular wall 51. Furthermore, because a cleaning tool cannot be inserted too forcefully into the small flame holes 52a, the stopper portion 55 is not provided at a circumferential position that coincides with the small flame holes 52a.

[0027] Incidentally, for cleaning purposes, the burner head 5 may be removed from the burner body 4 by loosening the fastening with the long screw 5b. After cleaning, there is a possibility that the user may perform an ignition operation while forgetting to attach the burner head 5 to the burner body 4. In this case, there is a risk that a backfire will occur through the distribution chamber 42 in the burner body 4 and the gas inlet pipe 3 to the gas nozzle 32, causing the gas nozzle 32 to burn out.

[0028] Therefore, in this embodiment, the distribution chamber 42 is provided with a second flashback suppression member 43 having a vent through which gas passes. This prevents flashback from reaching the gas nozzle 32 even if the ignition operation is performed while the burner head 5 is not attached to the burner body 4. Therefore, flashback can be prevented from reaching the gas nozzle 32, eliminating the risk of the gas nozzle 32 being burned. The second flashback suppression member 43 can also be made of a porous material like the flashback suppression member 54. However, in this embodiment, in order to reduce costs, the second flashback suppression member 43 is made of a sheet metal member having a plurality of small holes 431 formed therein, each of which serves as a vent and has a hole diameter (e.g., 0.6 mm) equal to or smaller than the quenching distance.

[0029] Here, the distribution chamber 42 is composed of a lower distribution chamber 421 into which gas flows in from the gas inlet pipe 3, and a wide upper distribution chamber 422 located above the lower distribution chamber 421. The upper distribution chamber 422 is surrounded by an annular upper distribution chamber bottom 4221 having a lower distribution chamber communication port 4221a communicating with the lower distribution chamber 421, an upper distribution chamber outer peripheral wall 4222 erected on the outer periphery of the upper distribution chamber bottom 4221, and an upper distribution chamber inner peripheral wall 4223 erected on the inner periphery of the upper distribution chamber bottom 4221. The second flashback suppression member 43 is laid on the upper distribution chamber bottom 4221 so that a small hole 431 serving as a vent is located above the lower distribution chamber communication port 4221a, and in this state is fastened to the burner body 4 with a plurality of screws 432.

[0030] According to this, when an ignition operation is performed while the burner head 5 is not attached to the burner body 4, the location of the flame generation, except for the initial stage of ignition, is generally in the area between the outer peripheral wall 4222 and the inner peripheral wall 4223 of the upper distribution chamber 422, which is away from the upper distribution chamber bottom 4221. Therefore, the second flashback suppression member 43 installed on the upper distribution chamber bottom 4221 is prevented from being directly burned by the flame, and thermal deformation of the second flashback suppression member 43 can be prevented. Therefore, there is no risk of a gap being created between the second flashback suppression member 43 and the upper distribution chamber bottom 4221 due to thermal deformation of the second flashback suppression member 43, which would impair the flashback suppression effect.

[0031] This embodiment further includes a positioning means 44 for positioning the second flashback suppression member 43 relative to the upper distribution chamber 422. The positioning means 44 is composed of notches 441 formed at two locations around the inner periphery of the second flashback suppression member 43 and ribs 442 protruding from two locations around the outer periphery of the upper distribution chamber inner wall portion 4223. The notches 441 are engaged with the ribs 442 to position the second flashback suppression member 43 relative to the upper distribution chamber 422. Positioning the second flashback suppression member 43 in this manner prevents the small hole 431, which serves as a vent, from shifting from its position above the lower distribution chamber communication port 4221a. This ensures that gas can flow reliably from the lower distribution chamber 421 to the upper distribution chamber 422 through the small hole 431.

[0032] Furthermore, a heat insulating material 45 having a lower thermal conductivity than the material (e.g., aluminum alloy) of the burner body 4 is interposed between the upper distribution chamber bottom portion 4221 and the second flashback suppression member 43. This makes it possible to suppress heat conduction from the burner body 4 to the second flashback suppression member 43 by the heat insulating material 45. Therefore, thermal deformation of the second flashback suppression member 43 can be more effectively prevented.

[0033] Although the embodiments of the present invention have been described above with reference to the drawings, the present invention is not limited thereto. For example, in the above embodiment, the gas burner A is a diffusion combustion burner. However, it is also possible to use a premixing burner in which the gas inlet pipe 3 is a mixing pipe type and a mixture of fuel gas and primary air is ejected from the flame holes 52. However, when hydrogen gas is used as the fuel gas, a diffusion combustion burner is desirable in order to suppress flashback. Furthermore, in the above embodiment, the flashback suppression member 54 is disposed in the groove 532, which is a downstream portion of the distribution passage 53. However, it is also possible to dispose the flashback suppression member 54 in the communication hole 533 or the through hole 531, which is a portion of the distribution passage 53 upstream of the groove 532.

[0034] A...gas burner, 3...gas inlet pipe, 4...burner body, 42...distribution chamber, 5...burner head, 51...annular wall, 52...flame hole, 53...distribution passage, 54...flashback suppression member, 55...stopper portion.

Claims

1. A gas burner comprising a burner body rising from the downstream end of a gas inlet pipe and a burner head mounted on the burner body, wherein the burner body has a distribution chamber inside into which gas flows via the gas inlet pipe, and the burner head has an annular wall exposed on the outer periphery of the burner head, and this annular wall has a plurality of flame holes spaced circumferentially to eject gas from the distribution chamber, wherein the burner head has a distribution passage inside which distributes gas from the distribution chamber to the flame holes, and a flashback suppression member made of a porous material made of metal or ceramic is interposed in the distribution passage, and the gas that passes through the flashback suppression member is distributed to the flame holes.

2. A gas burner according to claim 1, wherein the burner holes are formed so that the opening area of the burner holes relative to the outer peripheral surface of the annular wall is larger than the opening area of the burner holes relative to the inner peripheral surface of the annular wall.

3. A gas burner according to claim 1, wherein the flashback suppression member is formed in an annular shape, and the outer circumferential surface of the flashback suppression member abuts or closely faces the inner circumferential surface of the annular wall.

4. A gas burner according to claim 3, characterized in that a plurality of stopper portions are provided on said burner head at intervals in the circumferential direction, which stopper portions abut against or closely face the inner peripheral surface of said flashback suppression member.

5. A gas burner according to claim 4, wherein said stopper portion is provided at a circumferential position that coincides with said flame hole.

6. A gas burner as claimed in claim 1, characterized in that the gas flowing in from the gas inlet pipe is fuel gas not mixed with primary air, and the fuel gas is ejected from the flame holes to cause diffusion combustion.

7. A cooking device comprising the gas burner according to any one of claims 1 to 6.

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