Premixing device and combustion apparatus including the same

Abstract

To provide a premixing device capable of increasing a turndown ratio by means with a simple configuration and having an excellent function of maintaining an air-fuel mixture at an appropriate mixing ratio.SOLUTION: A premixing device A includes: a premixing flow passage 3 having first and second flow passages 3a, 3b; first and second fuel gas outflow ports 80a, 80b; and a swingable flapper 5 located in the first flow passage 3a. When the flapper 5 changes from a closed state to an opened state, auxiliary flow passages 38a, 38b on a base end side and a tip side are formed between regions on the base end part side and the tip part side of the flapper 5 and a predetermined seat part 47. Via the auxiliary flow passages 38a, 38b, air flows from a predetermined specific flow passage region 3a' to a downstream side region in an air flowing direction of the flapper 5, and fuel gas flows out from the first fuel gas outflow port 80a along with the air flow.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a premixing device and a combustion device including the same. Here, "premixing" is a process of premixing air and fuel gas in advance to generate a combustible mixture for the purpose of performing premixing combustion.

Background Art

[0002] As a specific example of the premixing device, there is one described in Patent Document 1. The premixing device described in the same document has a venturi-shaped premixing flow path whose one end is open to the outside and the other end is connected to the intake side of a fan. When the fan is driven, outside air flows in from the opening at the one end and flows in a predetermined direction. This premixing flow path is partitioned into first and second flow paths by a partition wall portion, and first and second fuel gas outlets are provided on the inner peripheral wall surfaces of these first and second flow paths, respectively. Further, a flapper that can swing to open and close the first flow path is provided in the first flow path. This flapper changes its opening degree corresponding to the air flow rate such that the opening degree is smaller when the air flow rate in the first flow path is small than when it is large.

[0003] In such a premixing device, air flows in the premixing flow path, and negative pressure acts on the first and second fuel gas outlets. As a result, fuel gas flows out from these first and second fuel gas outlets into the premixing flow path. This fuel gas is mixed with the air to generate a mixture. On the other hand, when the air flow rate is small, the flapper closes the first flow path of the premixing flow path. For this reason, the flow velocity of air in the second flow path becomes faster, and the negative pressure acting on the second fuel gas outlet is strengthened. As a result, even when the air flow rate is small, an appropriate amount of fuel gas can flow out from the second fuel gas outlet due to the negative pressure. Such an action is effective in increasing the turndown ratio.

[0004] However, in the prior art, as described below, there was still room for improvement.

[0005] That is, when the flapper changes from the closed state to the open state, the effective flow area of the premixing flow path changes abruptly. For this reason, due to the influence, in the second flow path, the flow velocity of the air flow that has been occurring decreases abruptly. As a result, the mixing ratio (air-fuel ratio) of the air-fuel mixture also changes abruptly, and there is a possibility that the air-fuel mixture may have an inappropriate mixing ratio that is fuel-lean.

[0006] In addition, the flapper only opens and closes the first flow path, and the first fuel gas outlet remains open. For this reason, even if the first flow path is switched from the open state to the closed state by the flapper, for example, there is a possibility that fuel gas may flow out from the first fuel gas outlet for a while thereafter. Furthermore, due to the pressure fluctuation of the first flow path affected by the air flow in the second flow path, there is also a possibility that air in the first flow path may flow into (backflow) the first fuel gas outlet, or fuel gas may flow out unnecessarily from the first fuel gas outlet. In this case, it is difficult to maintain the air-fuel mixture at a desired appropriate mixing ratio. As a means to solve this, there is a means of further providing an additional flapper for opening and closing the first fuel gas outlet (see Patent Document 2). However, according to such a means, since two flappers for the first flow path and the first fuel gas outlet are used, the total number of parts increases, and the manufacturing cost becomes high.

[0007] Furthermore, in the prior art (both Patent Documents 1 and 2), when the flapper changes from the closed state to the open state (when the flapper is at a small opening degree), the air flow rate in the first flow path is relatively small, and the air flow in the first flow path is at a low speed. For this reason, at that time, it is difficult to apply a strong negative pressure to the first fuel gas outlet, and the outflow amount of fuel gas from the first fuel gas outlet tends to be insufficient, and there is a possibility that the mixing ratio becomes inappropriate.

Prior Art Documents

Patent Documents

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2021-99204 [Patent Document 2] U.S. Patent No. 9,677,759 [Patent Document 3] Japanese Patent No. 5,948,440 [Patent Document 4] Japanese Patent No. 7,303,100 [Patent Document 5] Japanese Patent No. 6,738,493 [Summary of the Invention] [Problems to be Solved by the Invention]

[0009] The present invention has been conceived under the circumstances as described above, and it is an object of the present invention to provide a premixing device capable of increasing the turndown ratio and maintaining an appropriate air-fuel ratio of the air-fuel mixture with excellent performance by means of a simple configuration, and a combustion device equipped with the same. [Means for Solving the Problems]

[0010] To solve the above problems, the present invention takes the following technical means.

[0011] The premixing device provided by the first aspect of the present invention includes a premixing flow path for supplying air from the outside and mixing fuel gas with this air to generate a mixture gas, a partition wall portion that partitions this premixing flow path into first and second flow paths arranged in parallel, and first and second fuel gas outlets that can discharge fuel gas into the first and second flow paths by utilizing the negative pressure generated by the air flow in the first and second flow paths. There are x and y directions that intersect each other as directions intersecting the air flow direction in the first and second flow paths. It is a premixing device, and includes a blade portion provided in the first flow path and with the first fuel gas outlet provided facing the downstream side in the air flow direction, a specific flow path region as a part of the first flow path that is adjacent to both sides or one side of the blade portion in the x direction, a flapper provided at a position downstream of the blade portion and the specific flow path region in the air flow direction in the first flow path, and a seat portion for the flapper including the peripheral edge of the first fuel gas outlet and the opening peripheral edge on the downstream side in the air flow direction of the specific flow path region. The flapper has a base end portion supported by a support portion and can swing around this support portion, and can set a closed state in which the base end portion and the tip end portion face and contact the seat portion in a manner arranged in the y direction. Thus, the first fuel gas outlet and the specific flow path region can be opened and closed corresponding to the air flow rate of the premixing flow path. When the flapper changes from the closed state to the open state, auxiliary flow paths are formed between the respective regions on the base end side and the tip end side of the flapper and the seat portion, and through these auxiliary flow paths, an air flow from the specific flow path region to a region downstream of the flapper in the air flow direction and a fuel gas outflow from the first fuel gas outlet accompanying this air flow occur. This is the characteristic configuration.

[0012] According to such a configuration, when the air flow rate supplied to the premixing flow path is small, the first flow path (specific flow path region) is closed by the flapper, and the fuel gas flowing out from the second fuel gas outlet is mixed with the air flowing through the second flow path. On the other hand, when the air flow rate is large, air also flows in the first flow path, and the fuel gas flowing out from the first fuel gas outlet is mixed with this air. Therefore, similar to Patent Document 1, it is possible to increase the turndown ratio. Furthermore, according to the present invention, the following effects can be obtained. First, the flapper can not only open and close the first flow path (specific flow path region), but also open and close the first fuel gas outlet. Therefore, when the first flow path is in the closed state, the first fuel gas outlet is also simultaneously in the closed state, and it is possible to appropriately prevent situations such as unnecessary outflow of fuel gas from the first fuel gas outlet. As a means to achieve such a thing, it is not necessary to use a total of two flappers for the first flow path and the first fuel gas outlet. Therefore, it is possible to simplify the overall configuration and reduce the manufacturing cost. Second, when the flapper changes from the closed state to the open state (when the opening degree of the flapper is at a small opening degree of a predetermined value or less), it is possible to cause an air flow from the specific flow path region of the first flow path toward the region downstream of the flapper in the air flow direction via the auxiliary flow paths on the base end side and the tip end side formed between the respective regions on the base end side and the tip end side of the flapper and the seat portion. Along with this, it is also possible to cause the negative pressure due to the air flow to act on the first fuel gas outlet and cause the fuel gas to flow out. Therefore, it is possible to sufficiently ensure the outflow amount of the fuel gas to the first flow path. Also, when the flapper changes from the closed state to the open state, the air flowing through the first flow path flowing into the first fuel gas outlet and flowing backward to the second flow path side is also suppressed. From such things, according to the present invention, when the flapper changes from the closed state to the open state, it is possible to prevent the air-fuel mixture from becoming an inappropriate air-fuel ratio with a lean fuel, and it can be made excellent in the performance of maintaining the air-fuel mixture at an appropriate air-fuel ratio.

[0013] In the present invention, preferably, when the flap is in the closed state, the first fuel gas outlet is fully closed by the flap, while the specific flow path region is in a non-fully closed state in which a part located closer to the base end portion of the flap is in an open state, and it is configured such that an air flow can occur from the specific flow path region to a region downstream of the flap in the air flow direction via the open part.

[0014] According to such a configuration, even when the flap is in the closed state and the outflow of fuel gas from the first fuel gas outlet is blocked, the specific flow path region is not in a fully closed state, and a part closer to the base end portion of the flap is in an open state, so that an air flow can be generated in the vicinity of the base end portion of the flap. Therefore, even immediately after the flap changes from the closed state to the open state and when the opening degree of the flap is quite small, a large amount of air flow can be generated in the auxiliary flow path on the base end side. This is advantageous for promoting the outflow of fuel gas from the first fuel gas outlet.

[0015] In the present invention, preferably, the flap includes a plate-shaped flap main body portion that contacts the seat portion in the closed state of the flap, and an extension portion that is connected to the flap main body portion and at least a part of which is included in the base end portion. The support portion is a portion that supports the extension portion so as to be swingable around a center line extending in the x direction, and is provided so as to be located on the downstream side of the flap main body portion in the air flow direction and on the partition wall portion side when the flap is in the closed state.

[0016] According to such a configuration, the flapper main body swings around the center line extending in the x direction of the support portion, while the support portion is located on the downstream side of the flapper main body in the air flow direction and on the partition wall portion side when the flapper is in the closed state. Therefore, when changing the flapper from the closed state to the open state, the entire area from the base end side to the tip end side of the flapper main body (the area having a width in the y direction) can be immediately separated from the seat portion, and a gap can be accurately generated between them. As a result, these gaps can be used as portions corresponding to the auxiliary flow paths on the base end side and the tip end side, and the action intended by the present invention can be appropriately obtained.

[0017] In the present invention, preferably, the continuous portion is configured to be separated from the seat portion such that a first gap is formed between the continuous portion and the seat portion when the flapper is in the closed state. When the flapper changes from the closed state to the open state, the first gap is configured to form the auxiliary flow path on the base end side.

[0018] According to such a configuration, since the auxiliary flow path on the base end side formed when the flapper changes from the closed state to the open state is formed using the first gap, it is possible to surely and simply achieve increasing the overall size of the auxiliary flow path on the base end side.

[0019] In the present invention, preferably, the continuous portion of the flapper has an inclined surface portion inclined such that the separation distance from the seat portion increases as it approaches the support portion side from the flapper main body portion side in the region facing the seat portion when the flapper is in the closed state.

[0020] According to such a configuration, as can be understood from the description to be described later with reference to FIG. 10, when the flapper is in the open state, a part of the air can be made to travel along the inclined surface portion, and it is possible to suppress the occurrence of inappropriate turbulence in the air flow. Therefore, it is possible to smoothly cause the fuel gas to flow out from the first fuel gas outlet.

[0021] In the present invention, preferably, between the continuous portion and the partition wall portion, when the flapper is in the closed state and when it changes from the closed state to the open state, a second gap is formed that communicates the first gap with a region downstream of the flapper in the air flow direction.

[0022] According to such a configuration, when the flapper changes from the closed state to the open state, air can smoothly flow from the specific flow path region to the region downstream of the flapper in the air flow direction via the first and second gaps. Therefore, such an air flow can appropriately promote the outflow of the fuel gas from the first fuel gas outlet.

[0023] In the present invention, preferably, at the base end portion of the flapper, when the flapper is in the closed state and when it changes from the closed state to the open state, a hole or notch is provided that communicates the first gap with a region downstream of the flapper in the air flow direction of the first flow path.

[0024] According to such a configuration, when the flapper changes from the closed state to the open state, air can smoothly flow from the first gap through the hole or notch of the flapper toward the region downstream of the flapper in the air flow direction. Therefore, the outflow of the fuel gas from the first fuel gas outlet can be appropriately promoted.

[0025] The combustion device provided by the second aspect of the present invention is a combustion device including a premixing device that generates a mixture of air and fuel gas, and a burner unit that receives the supply of the mixture from the premixing device and burns the fuel gas, wherein the premixing device used is the premixing device provided by the first aspect of the present invention.

[0026] According to such a configuration, the same effects as those described for the premixing device provided by the first aspect of the present invention can be obtained.

[0027] Other features and advantages of the present invention will become more apparent from the following description of embodiments of the invention with reference to the accompanying drawings.

Brief Description of the Drawings

[0028]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Mode for Carrying Out the Invention

[0029] Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the drawings.

[0030] FIG. 1 shows a hot water device WH. This hot water device WH is a hot water supply device and includes a premixing device A, a combustion device B (premixed combustion device), and a heat exchanger 11. The combustion device B is configured by combining a fan 1 and a burner section 2 with the premixing device A. The fan 1 is variable in speed (variable in air volume).

[0031] Details of the premixing device A will be described later. Using this premixing device A, an air-fuel gas mixture (flammable mixture) is generated, and this mixture is supplied to the burner section 2 via the fan 1. The burner section 2 includes a porous plate 21 having a plurality of ventilation holes 20 (flame holes) and is housed in a case 10. An ignition plug, a flame detection sensor, etc., not shown, are attached to the burner section 2. The above mixture passes through the plurality of ventilation holes 20 and burns below the porous plate 21. The combustion gas generated by the burner section 2 acts on the heat exchanger 11, and the hot water passing through the heat exchanger 11 is heated. Thereby, hot water is generated, and this hot water is supplied to a desired hot water supply destination.

[0032] As clearly shown in FIGS. 2 to 6, the premixing device A includes a device main body portion A0 and a flapper 5 assembled to the device main body portion A0. In the figure, the x and y directions intersect each other and both intersect the air flow direction in the premixing channel 3 described later. In the present embodiment, the air flow direction in the premixing channel 3 is the vertical height direction of the premixing device A.

[0033] The device main body A0 includes a premixing channel forming member 4 and a pipe joint part 70. The premixing channel forming member 4 includes a cylindrical part 49 that forms a venturi-shaped premixing channel 3 inside, a flange part 48 continuously provided at the upper end of the cylindrical part 49, and a stepped pedestal part 44 protruding from the outer surface part of the cylindrical part 49. The pipe joint part 70 is attached to the pedestal part 44 using a screw member 90 such as a screw so as to sandwich a fuel gas control plate 71 described later.

[0034] As shown in FIG. 1, in the premixing device A, the pipe joint part 70 is connected to the gas pipe 99, and receives the supply of fuel gas from a fuel gas supply source (not shown) via a pressure equalizing valve (zero governor) V1. On the other hand, the premixing device A is directly or indirectly connected to the intake side of the fan 1 using the flange part 48. When the fan 1 is driven, external air flows into the premixing channel forming member 4 (the premixing channel 3 inside the cylindrical part 49). Due to the negative pressure action generated by this air flow, fuel gas flows out from the first and second fuel gas outlets 80a and 80b described later, and a mixture of this fuel gas and the air is generated. This mixture is supplied to the burner part 2 via the fan 1.

[0035] As well represented in FIGS. 4(b), 5(b), and 6(b), a partition wall part 40 extending in the vertical height direction, which is the air flow direction, is provided in the premixing channel 3. As a result, a part of the premixing channel 3 is partitioned into first and second channels 3a and 3b arranged in the y direction with the partition wall part 40 interposed therebetween. The partition wall part 40 is arranged offset in the y direction from the center of the cylindrical part 49, and the first channel 3a has a larger flow area than the second channel 3b. However, alternatively, the first and second channels 3a and 3b may have the same flow area.

[0036] As well represented by FIGS. 4 to 7, the first and second flow paths 3a and 3b are provided with first and second blade portions 41a and 41b (the hatched portions in FIGS. 7(a) and (c)). Among these first and second blade portions 41a and 41b, first and second fuel gas outlets 80a and 80b are provided in an upward opening manner on the upper surface portions as the main surface portions facing the downstream side in the air flow direction. Note that the first blade portion 41a corresponds to an example of the blade portion of the present invention. The first and second blade portions 41a and 41b extend in the y direction so as to horizontally cross the first and second flow paths 3a and 3b respectively, and one ends thereof are connected to the inner surface portion of the peripheral wall of the premixing flow path 3 (the inner surface portion of the peripheral wall portion of the cylindrical portion 49), and the other ends thereof are connected to each other with the partition wall portion 40 interposed therebetween.

[0037] As well represented by FIG. 7, the first blade portion 41a divides a part of the first flow path 3a into a pair of specific flow path regions (divided flow paths) 3a' through which air can flow. As a result, in the x direction, a pair of specific flow path regions 3a' are located on both sides of the first blade portion 41a. On the other hand, the second blade portion 41b divides a part of the second flow path 3b into a pair of divided flow paths 3b' through which air can flow. As a result, in the x direction, a pair of divided flow paths 3b' are located on both sides of the second blade portion 41b.

[0038] As shown in FIGS. 4(a), 5(a), and 6(a), the pipe joint portion 70 forms a fuel gas receiving portion 81 inside that receives the supply of fuel gas from the outside. The fuel gas supplied to this fuel gas receiving portion 81 is guided to the first and second fuel gas outlets 80a and 80b through the openings 71a and 71b of the fuel gas control plate 71 and the first and second fuel gas flow paths 8a and 8b.

[0039] The second fuel gas flow path 8b is provided inside the second blade portion 41b and the pedestal portion 44, while the first fuel gas flow path 8a is provided inside the first and second blade portions 41a, 41b and the pedestal portion 44. The second blade portion 41b has a greater vertical thickness than the first blade portion 41a, and within the second blade portion 41b, the first and second fuel gas flow paths 8a, 8b overlap in the vertical height direction. With such a configuration, it is possible to simplify the fuel gas supply structure to the first and second fuel gas outlets 80a, 80b. Further, by overlapping the first and second fuel gas flow paths 8a, 8b in the vertical height direction, the horizontal (x-direction) width of the second blade portion 41b is prevented from becoming overly large, ensuring a sufficient opening area for the pair of divided flow paths 3b'. This becomes possible.

[0040] The fuel gas control plate 71 is attached to the pedestal portion 44 as described above and has two openings 71a, 71b facing the tip openings of the first and second fuel gas flow paths 8a, 8b. By setting the opening areas of these openings 71a, 71b, the amount of fuel gas flowing into the first and second fuel gas flow paths 8a, 8b from the fuel gas receiving portion 81 can be controlled.

[0041] An air inlet portion 3c and an air outlet portion 3d communicating with the first and second flow paths 3a, 3b are formed in the lower and upper portions within the cylindrical portion 49. When the fan 1 is driven, external air can flow into the air inlet portion 3c and then branch into the first and second flow paths 3a, 3b. Due to the negative pressure action generated by the air flow in the first and second flow paths 3a, 3b, as described above, fuel gas flows out from the first and second fuel gas outlets 80a, 80b to generate a mixture of air and fuel gas. This mixture flows out of the air outlet portion 3d to the outside of the cylindrical portion 49.

[0042] As shown in FIGS. 4 to 6, the flapper 5 can simultaneously open and close the first flow path 3a (a pair of specific flow path regions 3a') and the first fuel gas outlet 80a, and more specifically, has the following configuration.

[0043] That is, the flapper 5 is, for example, a resin molded product, and as well represented in FIG. 8, includes a plate-shaped flapper main body portion 50, a continuous portion 51 in the shape of a protruding step portion continuously provided on a part thereof, and a pair of fin portions 55 protruding downward from the flapper main body portion 50. The base end portion 5a of the flapper 5 is a portion including the continuous portion 51. A support portion 52 is provided on the continuous portion 51 of the flapper 5. The support portion 52 is a portion that supports the continuous portion 51 so as to be swingable around a center line CL extending in the x direction, and a shaft body 61 serving as a swing fulcrum of the flapper 5 is provided through the continuous portion 51, and this shaft body 61 is a portion supported by a pair of auxiliary members 60 having support holes 60a as well represented in FIG. 3. The pair of auxiliary members 60 are attached to a step portion 43 separately provided in the first flow path 3a using a screw member 92 or the like.

[0044] The flapper 5 is disposed above the first blade portion 41a (downstream side in the air flow direction) in the first flow path 3a and is swingable in the vertical height direction around the support portion 52 (strictly speaking, the center line CL). As a result, the pair of specific flow path regions 3a' of the first flow path 3a and the first fuel gas outlet 80a can be simultaneously opened and closed (see FIGS. 4 to 6). The swing of the flapper 5 is performed with the self-weight of the flapper 5 as the downward force and the air flow traveling upward in each specific flow path region 3a' as the upward force, and the opening degree of the flapper 5 changes according to the air flow rate so that the opening degree is smaller when the air flow rate in the premixing flow path 3 is small than when it is large. When the air flow rate is small, the flapper 5 lies down due to its self-weight and assumes the closed state (fully closed state) shown in FIG. 4. When the air flow rate increases, the flapper 5 is lifted by the upward air flow and changes to, for example, the open state (fully open state) shown in FIG. 5. FIG. 6 shows the state when the flapper 5 changes from the closed state to the open state (a small opening state where the opening degree is below a predetermined value).

[0045] When the flapper 5 is in the fully open state as shown in FIG. 5, it is set to stand upright in the vertical height direction. In this fully open state, the center of gravity of the flapper 5 is located closer to the center of the first flow path 3a than directly above the swing center (center line CL) of the flapper 5, and a rotational moment for lowering the flapper 5 is generated. Therefore, when the air flow rate in the first flow path 3a decreases, the flapper 5 correspondingly descends and its opening degree becomes smaller.

[0046] The closed state of the flapper 5 is a state in which the flapper main body portion 50 is in contact with the seat portion 47 as shown in FIG. 4. Here, the seat portion 47 is an upward-facing surface portion of the first blade portion 41a that includes the peripheral edge of the first fuel gas outlet 80a and the upper opening peripheral edge (the opening peripheral edge on the downstream side in the air flow direction) of each specific flow path region 3a'.

[0047] In the closed state of the flapper 5, as shown in FIG. 4(a), the first fuel gas outlet 80a is configured to be fully closed by the flapper 5. On the other hand, as shown in FIG. 4(b), each specific flow path region 3a' is not fully closed by the flapper 5, and a part 3a" located closer to the base end portion 5a of the flapper 5 in each specific flow path region 3a' is configured to be in an open state. In the closed state of the flapper 5, an air flow from each specific flow path region 3a' to the region on the downstream side in the air flow direction from the flapper 5 can be generated via the part 3a".

[0048] The support portion 52 is provided in an offset arrangement on the side of the partition wall portion 40, downstream in the air flow direction from the flapper main body portion 50 and the first fuel gas outlet 80a when the flapper 5 is in the closed state. The continuous part 51 of the flap 5 is arranged to be spaced above the seat part 47 when the flap 5 is in the closed state, and a first gap C1 is formed between the continuous part 51 and the seat part 47. Further, in the downward region of the continuous part 51 facing the seat part 47, an inclined surface part 51a is formed which is inclined so that the separation distance La (see Fig. 8(b)) from the seat part 47 increases as it approaches the support part 52 side from the flap main body part 50 side. A second gap C2 communicating with the first gap C1 is formed between the continuous part 51 and the partition wall part 40.

[0049] When the flap 5 changes from the closed state shown in Fig. 4 to the open state (small opening state) shown in Fig. 6, auxiliary flow paths 38a and 38b on the base end side and the tip end side are formed between the respective regions on the base end part 5a side and the tip end part 5b side of the flap and the seat part 47. As a result, an air flow is generated from each specific flow path region 3a' via these auxiliary flow paths 38a and 38b on the base end side and the tip end side to the region downstream of the flap 5 in the air flow direction, and a fuel gas outflow from the first fuel gas outlet 80a is generated by the suction negative pressure action due to this air flow. More specifically, when the flap 5 is in the small opening state, the fuel gas and air (mixture) that have advanced into the auxiliary flow path 38b on the tip end side pass through the third gap C3 between the tip end part 5b of the flap 5 and the inner wall part of the first flow path 3a and flow into the region downstream of the flap 5 in the air flow direction. On the other hand, the fuel gas and air (mixture) that have advanced into the auxiliary flow path 38a on the base end side pass through the second gap C2 and flow into the region downstream of the flap 5 in the air flow direction. The auxiliary flow path 38a on the base end side is formed so as to include the above-mentioned first gap C1.

[0050] The pair of fin portions 55 of the flapper 5 project downward from the lower surface portion of the flapper 5 in a state of facing each other in parallel with a space therebetween (see also FIG. 8). As shown in FIGS. 4 and 6, when the flapper 5 is in the closed state and when it changes from the closed state to the open state, these pair of fin portions 55 are provided so as to sandwich the left and right sides of the first fuel gas outlet 80a and the first blade portion 41a. As will be described later, when the flapper 5 changes from the closed state to the open state, these pair of fins 55 help to suppress the phenomenon that the air in the first flow path 3a flows backward into the first and second fuel gas flow paths 8a and 8b due to the negative pressure generated in the second flow path 3b from the first fuel gas outlet 80a.

[0051] Next, the operation of the premixing device A described above and the combustion device B equipped with the same will be described.

[0052] During the driving combustion of the burner portion 2 of the combustion device B, the driving speed of the fan 1 is changed, and the flow rate of the air-fuel mixture supplied from the premixing device A to the burner portion 2 is changed, whereby the control of the driving combustion heat of the burner portion 2 is executed. Here, when the driving speed of the fan 1 is low and the air flow rate in the premixing flow path 3 is small, as shown in FIG. 4, the flapper 5 is in the closed state, and each specific flow path region 3a' of the first flow path 3a is blocked except for a part 3a" thereof, and air flows through the second flow path 3b. Therefore, the air flow in the second flow path 3b can be accelerated, a strong negative pressure can be applied to the second fuel gas outlet 80b, and an appropriate amount of fuel gas corresponding to the air flow rate can be made to flow out into the second flow path 3b. On the other hand, when the driving speed of the fan 1 is high, for example, as shown in FIG. 5, the flapper 5 is in the open state, air flows sufficiently through both the first and second flow paths 3a and 3b, and an appropriate amount of fuel gas corresponding to the air flow rate can be made to flow out from both the first and second fuel gas outlets 80a and 80b. From this, the turndown ratio can be increased.

[0053] The flapper 5 not only opens and closes the first flow path 3a, but also simultaneously opens and closes the first fuel gas outlet 80a. Therefore, for example, when the first flow path 3a is in a closed state, the first fuel gas outlet 80a is also in a closed state at the same time, so that problems such as unnecessary outflow of fuel gas from the first fuel gas outlet 80a afterwards are appropriately prevented. As a means to achieve such a thing, since a total of two flappers for the first flow path 3a and the first fuel gas outlet 80a are not used, the overall configuration of the premixing device A can be simplified and the manufacturing cost can be reduced.

[0054] When the air flow rate in the premixing flow path 3 increases from less than a predetermined value to more than the predetermined value, as described above, the flapper 5 changes from the closed state shown in FIG. 4 to the open state (small opening state) shown in FIG. 6. At this time, in the present embodiment, auxiliary flow paths 38a and 38b on the base end side and the tip end side communicate with the second gap C2 and the third gap C3 between each region of the base end portion 5a side and the tip end portion 5b side of the flapper 5 and the seat portion 47, respectively, to be formed. For this reason, a smooth air flow is generated from each specific flow path region 3a' of the first flow path 3a toward the region downstream of the flapper 5 in the air flow direction via these portions. Along with this, the negative pressure due to the air flow can also be applied to the first fuel gas outlet 80a to cause fuel gas outflow. Therefore, immediately after the flapper 5 changes from the closed state to the open state, it is possible to sufficiently secure the outflow amount of fuel gas to the first flow path 3a and suppress the air-fuel mixture from having an inappropriate mixing ratio with a fuel lean state. As a result, it is possible to make the performance of maintaining a constant mixing ratio excellent.

[0055] In particular, in the present embodiment, even when the flapper 5 is in the closed state shown in FIG. 4, each specific flow path region 3a' is not in a completely closed state, and a part 3a" near the base end portion 5a of the flapper 5 is in an open state, and an air flow is generated in this part. For this reason, even immediately after the flapper 5 changes to the open state, it is preferable for sufficiently securing the air flow rate in the auxiliary flow path 38a on the base end side of the flapper 5 and promoting the fuel gas outflow from the first fuel gas outlet 80a. When the flapper 5 changes from the closed state to the open state, as shown in FIG. 6, the flapper 5 is inclined so that the tip portion 5b side is separated from the seat portion 47 more than the base end portion 5a side. For this reason, originally, the auxiliary flow path 38a on the base end side would be a narrower flow path than the auxiliary flow path 38b on the tip end side, and the air flow rate in the auxiliary flow path 38a on the base end side would tend to be small. On the other hand, according to the above configuration of the present embodiment, it helps to eliminate such a situation.

[0056] In the present embodiment, when the flapper 5 is in the closed state, a first gap C1 is formed between the continuous portion 51 of the flapper 5 and the seat portion 47, as well represented in FIG. 9(a). As shown, when the flapper 5 changes to the open state, the first gap C1 is included in the auxiliary flow path 38a on the base end side and forms this auxiliary flow path 38a. Therefore, it is easily achievable to increase the overall size of the auxiliary flow path 38a on the base end side and secure the air flow rate in this portion. Also, in the present embodiment, the distance Lb from the swing center of the flapper 5 to the base end 50a of the flapper main body portion 50 is taken to be relatively large. For this reason, when the flapper 5 changes to the open state, it is also possible to increase the dimensional length Lc between the base end 50a of the flapper main body portion 50 and the seat portion 47 (see the right figure in FIG. 9(a)).

[0057] FIG. 9(b) shows a comparative example 1 with the present embodiment. In this comparative example 1, when the flapper 5E shown in the left figure of the same drawing is in the closed state, the portion corresponding to the first gap C1 of the present embodiment is not formed. Also, when the flapper 5E shown in the right figure of the same drawing changes to the open state, the lower surface of the base end portion of the flapper 5E is in contact with the seat portion 47, and the portion corresponding to the auxiliary flow path 38a on the base end side of the present embodiment is not formed. According to such a configuration, it is difficult to appropriately discharge the fuel gas from the first fuel gas outlet 80a. On the other hand, according to the present embodiment, such a situation is appropriately eliminated.

[0058] In this embodiment, as shown in the right diagram of Fig. 10(a), when the flapper 5 has a slightly larger opening degree, a part of the air traveling from below collides with the continuous portion 51. On the other hand, an inclined surface portion 51a is formed on the continuous portion 51, and the air colliding with this inclined surface portion 51a can be smoothly advanced obliquely upward.

[0059] Fig. 10(b) shows Comparative Example 2 with respect to this embodiment. In this Comparative Example 2, a portion corresponding to the inclined surface portion 51a of the present invention is not provided on the flapper 5F. In this Comparative Example 2, as shown in the right diagram of the figure, when air collides with the base end portion of the flapper 5F, this air becomes turbulent flow that reflects in various directions. In this way, the smooth outflow of the fuel gas is inhibited. On the other hand, according to this embodiment, such a situation is appropriately resolved.

[0060] The first and second fuel gas flow paths 8a and 8b communicate with each other via the fuel gas receiving portion 81. Therefore, originally, when the flapper 5 changes from the closed state to the open state, the air in each specific flow path region 3a' of the first flow path 3a may flow backward into the first and second fuel gas flow paths 8a and 8b from the first fuel gas outlet 80a due to the negative pressure generated in the second flow path 3b. On the other hand, according to this embodiment, as described above, by forming the auxiliary flow paths 38a and 38b on the base end side and the tip end side, the air flow to the region downstream of the flapper 5 in the air flow direction is promoted, so the above-mentioned air backflow is appropriately suppressed. Also, in this embodiment, the pair of fin portions 55 serve as a resistance to the backflow, and the phenomenon of the backflow is more reliably suppressed.

[0061] Figs. 11 and 12 show other embodiments of the present invention. In these figures, elements that are the same as or similar to those in the above embodiment are denoted by the same reference numerals as in the above embodiment, and redundant descriptions are omitted.

[0062] In the embodiment shown in FIG. 11, a hole portion 56a is provided at the base end portion 5a of the flapper 5. This hole portion 56a is a portion that communicates the first gap C1 to a region downstream of the flapper 5 in the air flow direction in the first flow path 3a when the flapper 5 is in the closed state and when it changes from the closed state to the open state. In the embodiment shown in FIG. 12, instead of the hole portion 56a in FIG. 11, a notch portion 56b is provided at the base end portion 5a of the flapper 5.

[0063] In any of the embodiments of FIGS. 11 and 12, when the flapper 5 changes from the closed state to the open state, air can smoothly flow from the first gap C1 in each specific flow path region 3a' of the first flow path 3a through the hole portion 56a or the notch portion 56b of the flapper to the region downstream of the flapper 5 in the air flow direction. Therefore, the outflow of the fuel gas from the first fuel gas outlet 80a can be appropriately promoted. The configuration of the present embodiment is particularly suitable, for example, when the width of the second gap C2 cannot be increased and the air flow rate in the second gap C2 is somewhat insufficient.

[0064] The present invention is not limited to the content of the above-described embodiments. The specific configurations of each part of the premixing device and the combustion device according to the present invention can be variously designed and changed within the scope intended by the present invention.

[0065] The premixing flow path is preferably venturi-shaped, but is not limited thereto. The specific shapes, sizes, materials, etc. of the first and second blade portions and the flapper are not limited to the above-described embodiments. The first and second fuel gas outlets may be provided, for example, in plural instead of one each. The specific flow path region is not limited to a configuration in which a pair is provided on both sides of the first blade portion in the x direction, and may also be a configuration in which it is provided only on one side of the first blade portion.

[0066] The flapper may also have a configuration that does not include the pair of fins. As means for enabling the flapper to swing, instead of using a shaft body made of metal or the like that is separate from the flapper, for example, a convex portion that serves as the swing center of the flapper can be provided on one of the flapper or the support member of the flapper, and a concave portion into which the convex portion is fitted can be provided on the other. Furthermore, it is also possible to configure the flapper to swing using, for example, the driving force of a motor.

[0067] The fuel gas is, for example, natural gas or LP gas, and its specific type is not limited. The combustion device according to the present invention is not limited to being used for a hot water device, and can also be a combustion device for other uses such as heating or incineration. Also, it is not limited to the type in which the combustion gas travels downward, and can also be a type in which the combustion gas travels upward, for example.

Explanation of Reference Signs

[0068] A Premixing device B Combustion device C1, C2 First and second gaps 1 Fan 2 Burner 3 Premixing flow path 3a, 3b First and second flow paths 3a' Specific flow path region (of the first flow path) 3a” Part (of the specific flow path region) 38a, 38b Auxiliary flow paths on the base end side and the tip end side 4 Premixing flow path forming member 40 Partition wall portion 41a First blade portion (blade portion) 41b Second blade portion 47 Seat portion 5 Flapper 5a Base end portion (of the flapper) 5b Tip end portion (of the flapper) 50 Flapper main body portion 51 Connecting portion 51a Inclined surface portion 52 Support portion 56a Hole portion 56b Notch portion 61 Shaft body 8a, 8b First and second fuel gas flow paths 80a, 80b First and second fuel gas outlets

Claims

1. A premixing flow path for supplying air from the outside and mixing fuel gas with this air to generate a mixture gas, A partition wall portion that divides this premixing flow path into first and second flow paths arranged in parallel, First and second fuel gas outlets that can discharge fuel gas into the first and second flow paths by utilizing the negative pressure generated by the air flow in the first and second flow paths, Comprising, A premixing device having x and y directions that intersect each other as directions intersecting the air flow direction in the first and second flow paths, A blade portion provided in the first flow path and having the first fuel gas outlet provided facing the downstream side in the air flow direction, A specific flow path region as a part of the first flow path that is adjacent to both sides or one side of the blade portion in the x direction, A flapper provided at a position downstream of the blade portion and the specific flow path region in the air flow direction in the first flow path, A seat portion for the flapper including the peripheral edge of the first fuel gas outlet and the opening peripheral edge on the downstream side in the air flow direction of the specific flow path region, Comprising, The flapper has a base end portion supported by a support portion and can swing around this support portion, and can set a closed state in which the base end portion and the tip end portion face and contact the seat portion in a manner arranged in the y direction, so that the first fuel gas outlet and the specific flow path region can be opened and closed corresponding to the air flow rate in the premixing flow path, When the flapper changes from the closed state to the open state, auxiliary flow paths on the base end side and the tip end side are formed between the respective regions on the base end side and the tip end side of the flapper and the seat portion, and through these auxiliary flow paths, an air flow from the specific flow path region to a region downstream of the flapper in the air flow direction and a fuel gas outflow from the first fuel gas outlet accompanying this air flow are generated. A premixing device characterized by this configuration.

2. The premixing device according to Claim 1, When the flapper is in the closed state, the first fuel gas outlet is completely closed by the flapper, while the specific flow path region is in a non-fully closed state in which a part located closer to the base end portion of the flapper is in an open state, and an air flow from the specific flow path region to a region downstream of the flapper in the air flow direction can be generated through the open part. A premixing device having such a configuration.

3. The premixing device according to claim 1, wherein the flapper includes a plate-shaped flapper body portion that contacts the seat portion in a closed state of the flapper, and a connecting portion that is connected to the flapper body portion and at least a part of which is included in the base end portion, the support portion is a portion that supports the connecting portion so as to be swingable around a center line extending in the x direction, and is provided so as to be located on the downstream side in the air flow direction and on the partition wall portion side with respect to the flapper body portion when the flapper is in the closed state. A premixing device.

4. The premixing device according to claim 3, wherein the connecting portion is configured to be separated from the seat portion such that a first gap is formed between the connecting portion and the seat portion when the flapper is in the closed state, when the flapper changes from the closed state to the open state, the first gap is configured to form an auxiliary flow path on the base end side. A premixing device.

5. The premixing device according to claim 4, wherein the connecting portion of the flapper has an inclined surface portion that is inclined such that the separation distance from the seat portion increases as it approaches the support portion side from the flapper body portion side in a region facing the seat portion when the flapper is in the closed state. A premixing device.

6. The premixing device according to claim 4, wherein a second gap is formed between the connecting portion and the partition wall portion to communicate the first gap to a region on the downstream side in the air flow direction with respect to the flapper when the flapper is in the closed state and when the flapper changes from the closed state to the open state. A premixing device.

7. The premixing device according to claim 4, wherein a hole or notch is provided at the base end portion of the flapper to communicate the first gap to a region on the downstream side in the air flow direction with respect to the flapper in the first flow path when the flapper is in the closed state and when the flapper changes from the closed state to the open state. A premixing device.

8. A combustion device comprising a premixing device for generating a mixture of air and fuel gas, and a burner unit that receives the supply of the mixture from the premixing device and burns the fuel gas, wherein the premixing device used is the premixing device according to any one of claims 1 to 7. ​

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