Premixing device and combustion apparatus comprising the same

Abstract

To provide a premixing device having a high turndown ratio and an excellent performance of maintaining an air-fuel mixture at a suitable mixing ratio.SOLUTION: A premixing device A comprising a premixing flow path 3 including first and second flow paths 3a, 3b, and first and second fuel gas outflow ports 80a, 80b, comprises a first blade unit 41a disposed in the first flow path 3a and provided with a first fuel gas outflow port 80a, a protruding wall 45 provided in the first blade unit 41a, and a flapper 5 swinging on a downstream position in the air flow direction relative to the first blade unit 41a of the first flow path 3a, and the air present in the first flow path 3a can be suppressed from flowing toward the first fuel gas outflow port 80a by the protruded wall 45, when the flapper 5 is in an opened state of a predetermined or a lower opening degree.SELECTED DRAWING: Figure 6

Description

[Technical field]

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

[0002] A specific example of a premixing device is described in Patent Document 1. The premixing device described in the document is provided with a venturi-shaped premixing passage having one end opening to the outside and the other end connected to the intake side of a fan, and when the fan is driven, external air flows in from the opening at the one end and flows in a predetermined direction. The premixing passage is divided into first and second passages by a partition wall, and first and second fuel gas outlets are provided on the inner peripheral walls of the first and second passages, respectively. The first passage is provided with a flapper that can swing to open and close the first passage. The opening of the flapper is changed in response to the air flow rate so that when the air flow rate in the first passage is low, the opening is smaller than when the air flow rate is high.

[0003] In such a premixing device, air flows through the premixing passage, and negative pressure acts on the first and second fuel gas outlets, causing fuel gas to flow out from the first and second fuel gas outlets into the premixing passage. This fuel gas is mixed with the air to generate a mixture. On the other hand, when the air flow rate is low, the flapper closes the first passage of the premixing passage. This increases the flow rate of the air in the second passage, and the negative pressure acting on the second fuel gas outlet is strengthened. As a result, even when the air flow rate is low, an appropriate amount of fuel gas can be discharged from the second fuel gas outlet by the negative pressure. This action is effective in increasing the turndown ratio.

[0004] However, the above-mentioned conventional techniques still have room for improvement, as described below.

[0005] That is, the flapper in the conventional technology merely opens and closes the first flow passage, and the first fuel gas outlet remains open. Therefore, for example, even if the first flow passage is switched from an open state to a closed state by the flapper, there is a risk that the fuel gas will flow out from the first fuel gas outlet for a certain period of time thereafter. In addition, there is a risk that the air in the first flow passage will flow (reverse flow) into the first fuel gas outlet or that the fuel gas will unnecessarily flow out from the first fuel gas outlet due to the pressure fluctuation of the first flow passage being affected by the air flow in the second flow passage. This makes it difficult to maintain the mixture at a desired appropriate mixture ratio. One solution to this problem is to provide an additional flapper for opening and closing the first fuel gas outlet (see Patent Document 2). However, this solution requires the use of two flappers, one for the first flow path and one for the first fuel gas outlet, which increases the overall number of parts and increases the manufacturing cost.

[0006] Furthermore, when the flapper changes from the closed state to the open state, the effective flow area of ​​the premix flow passage changes suddenly. As a result, the flow velocity of the air flow that has been generated in the second flow passage may suddenly decrease. This may cause the mixture ratio of the mixture to change suddenly, and the mixture may become inappropriately fuel-lean. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 2021-99204 [Patent Document 2] U.S. Patent No. 9,677,759 [Patent Document 3] Patent No. 6738493 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention was conceived under the circumstances described above, and has an object to provide a premixing device that is capable of increasing the turndown ratio and having excellent performance of maintaining the air-fuel mixture at an appropriate mixture ratio by using means having a simple configuration, and a combustion device equipped with the same. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention provides the following technical solutions.

[0010] A premixing device provided according to a first aspect of the present invention includes a premixing flow passage to which air is supplied from the outside and which generates an air-fuel mixture by mixing the air with a fuel gas, a partition wall portion which divides the premixing flow passage into first and second flow passages arranged in parallel, and first and second fuel gas outlets which are capable of discharging fuel gas into the first and second flow passages by utilizing negative pressure generated by air flows in the first and second flow passages, the premixing device including a first blade portion which is provided in the first flow passage and has the first fuel gas outlet facing downstream in the air flow direction, and a first blade portion which extends from an edge of the first fuel gas outlet to the first flow passage. The premix flow passage has a protruding wall portion provided on the first blade portion so as to protrude toward the downstream side in the air flow direction, and a flapper that swings in a direction facing the first blade portion at a position in the first flow passage downstream of the first blade portion in the air flow direction and is capable of opening and closing both the first flow passage and the first fuel gas outlet in accordance with the air flow rate of the premix flow passage while avoiding interference with the protruding wall portion, and is configured such that when the flapper is in an open state at a predetermined opening degree or less, the protruding wall portion can prevent the air in the first flow passage from flowing to the first fuel gas outlet.

[0011] According to this configuration, when the air flow rate supplied to the premixing passage is low, the first passage is closed by the flapper, and the air flowing through the second passage is mixed with the fuel gas flowing out from the second fuel gas outlet. On the other hand, when the air flow rate is high, air also flows through the first passage, and the fuel gas flowing out from the first fuel gas outlet is mixed with this air. Therefore, as in 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 open and close not only the first flow path but also the first fuel gas outlet. Therefore, when the first flow path is closed, the first fuel gas outlet is also closed at the same time, and it is possible to appropriately prevent fuel gas from unnecessarily flowing out from the first fuel gas outlet thereafter. Since there is no need to use two flappers, one for the first flow path and one for the first fuel gas outlet, as a means for achieving this, it is possible to simplify the overall configuration and reduce manufacturing costs. Secondly, in the past, when the flapper changed from a closed state to an open state (small opening state) below a predetermined opening degree, there was a risk that the air in the first flow path would flow back from the first fuel gas outlet to the first and second fuel gas flow paths due to the negative pressure generated in the second flow path. In contrast, in the present invention, when the flapper changes from a closed state to an open state, the protruding wall portion prevents the air in the first flow path from flowing into the first fuel gas outlet, so that the backflow of air can be appropriately prevented or suppressed. Therefore, when the flapper changes from a closed state to an open state, the mixture is appropriately suppressed from becoming an inappropriate fuel-lean mixture ratio. Third, when the flapper changes from a closed state to an open state, the protruding wall portion This generates air resistance that causes the airflow to flow through the second flow passage when the flapper is changed from the closed state to the open state. This prevents the flow rate of the airflow that has been generated in the second flow passage from suddenly decreasing when the flapper is changed from the closed state to the open state. As a result, it is possible to appropriately prevent the mixture ratio from becoming an inappropriate mixture ratio that is fuel lean.

[0012] In the present invention, preferably, as a means for avoiding interference between the flapper and the protruding wall portion, the flapper is provided with a hole into which the protruding wall portion enters when the flapper is in an open state below the specified opening degree.

[0013] According to this configuration, interference between the flapper and the protruding wall can be appropriately avoided by a simple configuration of merely providing a hole in the flapper, which is preferable in terms of suppressing increases in manufacturing costs and weight.

[0014] In the present invention, preferably, the protruding wall portion has a height enabling it to escape from the hole of the flapper when the flapper is in an open state greater than the predetermined opening degree.

[0015] With this configuration, when the flow rate of air supplied to the premix flow passage is large and the opening degree of the flapper is large, the air resistance of the protruding wall portion can be prevented from becoming too large.

[0016] In the present invention, preferably, the hole portion of the flapper is a long hole extending in a specific direction from the base end side near the swing center of the flapper to the tip end, the protruding wall portion is a rib extending in a direction corresponding to the specific direction, and a flat or curved chamfered portion is provided at the corner of the tip portion of the protruding wall portion away from the swing center of the flapper.

[0017] With this configuration, the chamfered portion can appropriately prevent the flapper from interfering with the corner of the tip of the protruding wall when the flapper swings, which is preferable in terms of reducing the size of the hole provided in the flapper.

[0018] In the present invention, preferably, the protruding wall portion extends continuously along the first fuel gas outlet, and the length thereof is approximately the same as the length of the first fuel gas outlet.

[0019] According to this configuration, the length of the protruding wall portion is just right or shorter than the length of the first fuel gas outlet, which avoids the drawback of the protruding wall portion being unnecessarily large and increasing air resistance, and appropriately achieves the intended effect of the present invention, that is, the effect of preventing air in the first flow path from flowing into the first fuel gas outlet when the flapper is in an open state (small opening state) below a predetermined opening degree.

[0020] In the present invention, preferably, there are x and y directions that intersect with the air flow direction, and the first blade portion extends in the y direction so as to be bridged between one part of the inner wall of the first flow path and another part, thereby dividing a part of the first flow path into a pair of divided flow paths, and in the x direction, the first blade portion and the first fuel gas outlet are located between the pair of divided flow paths, and the protruding wall portion comprises a pair of protruding wall portions located on both edges of the first fuel gas outlet in the x direction.

[0021] According to this configuration, when the flapper is in an open state and air flows through the first flow passage, the air flows through a pair of divided flow passages located on both sides of the first fuel gas outlet in the x direction. Therefore, by utilizing the negative pressure of this air flow, a gas flow rate corresponding to the air flow rate is output from the first fuel gas outlet. On the other hand, when the flapper is in an open state of not more than a predetermined opening degree, the provision of the pair of protruding walls appropriately prevents air from flowing back from each of the pair of divided flow paths to the first fuel gas outlet.

[0022] In the present invention, preferably, the first blade portion does not have the protruding wall portion on both edges in the y direction of the first fuel gas outlet, and when the flapper is in an open state at or below the specified opening degree, the air in the first flow path can flow toward both edges in the y direction of the first fuel gas outlet.

[0023] According to this configuration, when the flapper is in an open state of not more than a predetermined opening degree, the air in the first flow path is caused to flow near both edges of the first fuel gas outlet in the y direction, and the negative pressure caused by this air flow can be utilized to cause the fuel gas to flow out of the first fuel gas outlet into the first flow path. It is possible to appropriately prevent the occurrence of any hindrance to the flow of fuel gas from the first fuel gas outlet due to the pair of protruding walls being provided on both edges of the first fuel gas outlet in the x direction.

[0024] In the present invention, preferably, the premixing flow passage forming member forms the premixing flow passage; a second blade portion provided in the second flow passage with one end connected to a peripheral wall portion of the premixing flow passage forming member and the other end connected to the first blade portion via the partition wall portion, the second fuel gas outlet being provided facing downstream in the air flow direction; a fuel gas receiving portion provided on the peripheral wall portion of the premixing flow passage forming member and receiving a supply of fuel gas from the outside; a second fuel gas flow passage provided in the second blade portion capable of guiding a portion of the fuel gas supplied to the fuel gas receiving portion to the second fuel gas outlet; and a first fuel gas flow passage provided extending from within the second blade portion into the first blade portion capable of guiding another portion of the fuel gas supplied to the fuel gas receiving portion to the first fuel gas outlet.

[0025] According to this configuration, it is possible to appropriately and rationally guide the fuel gas from the fuel gas receiving portion provided on the outer surface of the premix flow passage forming member to the first and second fuel gas outlets by utilizing the first and second fuel gas flow passages provided in the first and second blade portions. One fuel gas receiving portion is sufficient, and it is not necessary to provide multiple fuel gas receiving portions corresponding to the first and second fuel gas outlets, respectively. This simplifies the overall configuration and is suitable for reducing manufacturing costs. Furthermore, the configuration of the second blade portion and the second fuel gas outlet provided in the second blade portion makes it possible to effectively generate negative pressure when air flows near the second blade portion and to have this negative pressure act strongly on the second fuel gas outlet. Therefore, when the flapper of the first flow passage is closed due to a small amount of air supplied to the premix flow passage and fuel gas flows out only from the second fuel gas outlet, a sufficient amount of outflowing fuel gas can be ensured, which is more preferable in terms of increasing the turndown ratio.

[0026] A combustion device provided according to a second aspect of the present invention is a combustion device comprising: a fan; a premixing device provided on the intake side of the fan for generating a mixture by mixing air and fuel gas and sending the mixture to the fan; and a burner unit for receiving the mixture from the fan and combusting the fuel gas, wherein the premixing device provided according to the first aspect of the present invention is used as the premixing device.

[0027] With such a configuration, it is possible to obtain the same effects as those described for the premixing device provided according to the first aspect of the present invention.

[0028] Other features and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings. [Brief description of the drawings]

[0029] [Figure 1] 1 is a schematic explanatory diagram showing an example of a combustion apparatus equipped with a premixing device according to the present invention. [Diagram 2] FIG. 2 is a perspective view of the premixing device of FIG. 1. [Diagram 3] FIG. 3 is an exploded perspective view of FIG. 2. [Figure 4] 1, (b) is a cross-sectional view of the premixing device shown in FIG. 1 at a position different from that in (a), and (c) is a cross-sectional view taken along line IVc-IVc in (a) (cross-sectional view of the main part on the right side). [Diagram 5] 4(a) is a front cross-sectional view showing the premixer shown in FIG. 4(a) when a flapper is in a fully open state, and FIG. 4(b) is a cross-sectional view of a main part on the right side of FIG. 4(a). [Figure 6] 4(a) is a front cross-sectional view showing the state in which the flapper of the premixing device shown in FIG. 4(a) is in an open state below a predetermined opening degree, (b) is a cross-sectional view of the main part on the right side of (a), and (c) is an enlarged cross-sectional view of a part of (b). [Figure 7] FIG. 7(a) is a plan view of a premixing channel-forming member of the premixing device shown in FIGS. 2 to 6, (b) is a partially enlarged view thereof, and (c) is a plan cross-sectional view of the premixing channel-forming member. [Figure 8] 7 is a cross-sectional view of a main part showing the relationship between a flapper and a protruding wall portion of the premixer shown in FIGS. 2 to 6. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

[0031] 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 the premixing device A with a fan 1 and a burner section 2. The fan 1 has a variable speed (variable airflow rate).

[0032] The details of the premixing device A will be described later, but the premixing device A is used to generate a mixture of air and fuel gas (a combustible mixture), and the mixture is supplied to the burner section 2 via the fan 1. The burner section 2 is equipped with a porous plate 21 having a plurality of vent holes 20 (flame holes), and is housed in a case 10. The burner section 2 is provided with an ignition plug and a flame detection sensor (not shown). The mixture passes through the plurality of vent holes 20 and is combusted 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. This generates hot water, which is supplied to a desired hot water supply destination.

[0033] As clearly shown in FIGS. 2 to 6, the premixing device A includes a device main body A0 and a flapper 5 assembled to the device main body A0. In the figure, the x and y directions intersect each other and also intersect with the air flow direction in the premixing channel 3 described below. In this embodiment, the air flow direction in the premixing channel 3 is the vertical height direction of the premixing device A.

[0034] The device main body A0 includes a premixing flow passage forming member 4 and a pipe joint portion . The premixing flow passage forming member 4 includes a cylindrical portion 49 that defines the venturi-shaped premixing flow passage 3 therein, a flange portion 48 connected to the upper end of the cylindrical portion 49, and a stepped base portion 44 that protrudes from the outer surface of the cylindrical portion 49. The pipe joint portion 70 is attached to the base portion 44 using a screw member 90 such as a screw so as to sandwich a fuel gas control plate 71 (described later).

[0035] As shown in FIG. 1, the premixing device A has a pipe joint 70 connected to a gas pipe 99, and receives 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 by using a flange portion 48. When the fan 1 is driven, external air flows into the premixing flow passage forming member 4 (the premixing flow passage 3 in the cylindrical portion 49). Due to the negative pressure caused by this air flow, the 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 portion 2 via the fan 1.

[0036] 4(b), the premix flow channel 3 is provided with a partition wall 40 extending in the vertical direction, which is the air flow direction. This divides a part of the premix flow channel 3 into first and second flow channels 3a, 3b arranged in the y direction with the partition wall 40 in between. The partition wall 40 is disposed offset in the y direction from the center of the cylindrical section 49, and the first flow channel 3a has a larger flow channel area than the second flow channel 3b. However, the first and second flow channels 3a, 3b may have the same flow channel area.

[0037] 4 to 7, first and second blade portions 41a and 41b (shown in halftone dot patterns in FIGS. 7(a) and 7(c)) are provided in the first and second flow paths 3a and 3b. First and second fuel gas outlets 80a and 80b are provided in the upper surfaces of the first and second blade portions 41a and 41b, which serve as main surfaces facing downstream in the air flow direction, and which open upward. The first and second blade portions 41a, 41b extend in the y direction so as to horizontally cross the first and second flow paths 3a, 3b, respectively, and one end of each of them is connected to the inner surface of the peripheral wall of the premixing flow path 3 (the inner surface of the peripheral wall of the cylindrical portion 49), and the other ends of each of them are connected to each other across the partition wall portion 40. 7, the first blade portion 41a divides a part of the first flow passage 3a into a pair of divided flow passages 3a' through which air can flow. As a result, the first blade portion 41a and the first fuel gas outlet 80a are located between the pair of divided flow passages 3a' in the x direction. The second blade portion 41b divides a portion of the second flow passage 3b into a pair of divided flow passages 3b' through which air can flow, and in the x-direction, the second blade portion 41b and the second fuel gas outlet 80b are located between the pair of divided flow passages 3b'.

[0038] 4(a), the pipe joint portion 70 has a fuel gas receiving portion 81 formed therein for receiving a supply of fuel gas from the outside. The fuel gas supplied to the fuel gas receiving portion 81 passes through openings 71a and 71b of the fuel gas control plate 71 and the first and second fuel gas flow passages 8a and 8b, and is guided to the first and second fuel gas outlets 80a and 80b.

[0039] Here, the second fuel gas flow passage 8b is provided inside the second blade portion 41b and the base portion 44, whereas the first fuel gas flow passage 8a is provided inside the first and second blade portions 41a, 41b and the base portion 44. The second blade portion 41b has a larger vertical thickness than the first blade portion 41a, and the first and second fuel gas flow passages 8a, 8b overlap each other in the vertical height direction within the second blade portion 41b. With this configuration, it is possible to simplify the structure for supplying fuel gas to the first and second fuel gas outlets 80a, 80b. In addition, by overlapping the first and second fuel gas flow passages 8a, 8b in the vertical height direction, it is possible to prevent the width of the second blade portion 41b in the horizontal direction (x direction) from becoming too large, and to ensure a sufficient opening area of ​​the pair of divided flow passages 3b'.

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

[0041] An air inlet section 3c and an air outlet section 3d communicating with the first and second flow paths 3a and 3b are formed at the lower and upper parts of the cylindrical section 49. When the fan 1 is driven, the outside air flows into the air inlet section 3c and then branches into the first and second flow paths 3a and 3b. As described above, the negative pressure caused by the air flow in the first and second flow paths 3a and 3b causes the fuel gas to flow out of the first and second fuel gas outlets 80a and 80b, generating a mixture of air and fuel gas. This mixture flows out of the cylindrical section 49 from the air outlet section 3d.

[0042] The flapper 5 is, for example, a resin molded product, and is disposed above the first blade portion 41a (downstream in the air flow direction) of the first flow passage 3a, and is swingable opposite to the upper surface of the first blade portion 41a so as to simultaneously open and close the first flow passage 3a (strictly speaking, a pair of divided flow passages 3a') and the first fuel gas outlet 80a (see Figs. 4 to 6). More specifically, a shaft body 61 serving as a swing fulcrum (swing center) is inserted into the rear portion of the flapper 5, and the shaft body 61 is supported by a pair of left and right support members 60. The pair of support members 60 are attached to a step portion 43 separately provided in the first flow passage 3a by using a screw member 92 or the like.

[0043] The opening degree of this flapper 5 changes according to the air flow rate in the premixing channel 3 so that when the air flow rate is low, the opening degree is smaller than when the air flow rate is high. When the air flow rate is low, the flapper 5 falls over by its own weight and goes to 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 small open state where the opening degree of the flapper 5 is below a predetermined level.

[0044] As shown in FIG. 7, a pair of protruding walls 45 are provided on the upper surface of the first blade portion 41a. The pair of protruding walls 45 protrude upward from the upper surface of the first blade portion 41a and are located at both edges in the x direction of the first fuel gas outlet 80a. As a result, the first blade portion 41a, the pair of protruding walls 45, and the first fuel gas outlet 80a are located between the pair of divided flow channels 3a' in the x direction. Each protruding wall portion 45 is in the form of a rib extending continuously in the y direction along the first fuel gas outlet 80a, and preferably, the length La in the y direction of each protruding wall portion 45 is approximately the same as the length Lb of the first fuel gas outlet 80a. On the other hand, on both edge portions 46 of the upper surface of the first blade portion 41a in the y direction of the first fuel gas outlet 80a, no protruding wall portion 45 or a portion similar thereto is provided.

[0045] The flapper 5 has a pair of holes 55 as a means for avoiding interference with the pair of protruding wall portions 45 during its swinging motion. The pair of holes 55 are through holes into which the respective protruding wall portions 45 can enter when the flapper 5 is in the closed state or the partially open state shown in Fig. 4 and Fig. 6. Each hole 55 has a shape corresponding to the respective protruding wall portion 45, and is an elongated hole extending in a specific direction from the base end side near the swing center of the flapper 5 to the tip end.

[0046] When the flapper 5 is in a predetermined slightly open state as shown in FIG. 6 and a gap is formed between the flapper 5 and the first blade portion 41a, each of the protruding wall portions 45 closes the area between each of the pair of divided flow passages 3a' of the first flow passage 3a and the first fuel gas outlet 80a. The protruding wall portions 45 are formed to have a size that allows the air in the first flow passage 3a to flow into the first fuel gas outlet 80a. The height of each protruding wall portion 45 is set to a height that allows the air to escape from the hole 55 of the flapper 5 when the flapper 5 is not in a small opening state of a predetermined opening degree or less but in a larger opening state.

[0047] As shown in Fig. 8, each protruding wall portion 45 has a substantially rectangular shape in side view. However, at the tip of each protruding wall portion 45, a corner portion 45a on the side farther from the shaft body 61 that is the swing center of the flapper 5 is provided with a curved chamfered portion 45b with a curvature radius Ra. This is preferable in order to avoid interference with the corner portion 45a of the protruding wall portion 45 when the one end side peripheral portion a1 of the hole portion 55 of the flapper 5 shown in Fig. 8 moves in an arc trajectory with a radius Rb centered on the shaft body 61. The chamfered portion 45b may be a flat chamfered portion instead of a curved chamfered portion.

[0048] Next, the operation of the premixing device A and the combustion device B equipped with the same will be described.

[0049] At the start of the drive combustion of the burner section 2 of the combustion device B and during the subsequent normal drive combustion, the drive speed of the fan 1 is changed. This changes the flow rate of the mixture supplied from the premixer A to the burner section 2, making it possible to control the drive combustion heat of the burner section 2. Here, when the driving speed of the fan 1 is low and the air flow rate in the premixing flow path 3 is low, the flapper 5 is closed as shown in FIG. 4, and air does not flow in the first flow path 3a. In this case, air flows only in the second flow path 3b. Therefore, by increasing the speed of the air flow in the second flow path 3b and applying a strong negative pressure to the second fuel gas outlet 80b, an appropriate amount of fuel gas corresponding to the air flow rate can be discharged to the second flow path 3b. On the other hand, when the driving speed of the fan 1 is high, the flapper 5 is opened as shown in FIG. 5, for example. In this case, air flows in 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 discharged from both the first and second fuel gas outlets 80a and 80b. For this reason, it is possible to increase the turndown ratio.

[0050] The flapper 5 not only opens and closes the first flow passage 3a, but also opens and closes the first fuel gas outlet 80a at the same time. Therefore, for example, when the first flow passage 3a is closed, the first fuel gas outlet 80a is also closed at the same time, so that a problem such as unnecessary outflow of fuel gas from the first fuel gas outlet 80a is appropriately prevented. As a means for achieving this, two flappers, one for the first flow passage 3a and the other for the first fuel gas outlet 80a, are not used, so that the overall configuration of the premixing device A can be simplified and the manufacturing cost can be reduced.

[0051] The first and second fuel gas flow paths 8a, 8b communicate with each other via a fuel gas receiving portion 81. For this reason, when the flapper 5 changes from a closed state to a slightly open state as shown in FIG. 6, there is a risk of air in the first flow path 3a flowing into the fuel gas outlet 80a due to the negative pressure generated in the second flow path 3b, causing an air backflow phenomenon. However, according to this embodiment, the pair of protruding wall portions 45 obstruct the air flow. Therefore, the air backflow phenomenon is suppressed, and the mixture is appropriately prevented from becoming an inappropriate fuel-lean mixture ratio.

[0052] A pair of protruding walls 45 are provided on both x-direction edges of the periphery of the first fuel gas outlet 80a, but no protruding walls 45 or similar parts are provided on both y-direction edges 46 (see FIGS. 7(a) and 7(b)). Therefore, when the flapper 5 is in the partially open state, the air in the first flow path 3a can be made to flow toward both y-direction edges 46 of the first fuel gas outlet 80a, and proceed downstream of the first flow path 3a. By utilizing the negative pressure caused by this air flow, the fuel gas can be appropriately discharged from the first fuel gas outlet 80a to the first flow path 3a. The provision of the pair of protruding walls 45 appropriately prevents the amount of fuel gas flowing out from becoming insufficient when the flapper 5 is in the slightly open state.

[0053] Furthermore, when the flapper 5 changes from the closed state to the open state, the effective flow path area of ​​the premix flow path 3 changes (suddenly expands). For this reason, the flow velocity of the air flow in the second flow path 3b is likely to suddenly decrease, and the mixture may suddenly change to a fuel-lean mixture ratio. However, in this embodiment, when the flapper 5 changes from the closed state to the open state, the pair of protruding wall portions 45 generate air resistance in the first flow path 3a. As a result, when the flapper 5 changes from the closed state to the open state, it is possible to prevent the flow velocity of the air flow that has been generated in the second flow path 3b from suddenly decreasing. As a result, it is possible to more appropriately prevent the mixture ratio from becoming an inappropriate fuel-lean mixture ratio.

[0054] On the other hand, the pair of protruding walls 45 are sized to be able to enter the hole 55 of the flapper 5 when the flapper 5 is in a predetermined small open state, but to be able to escape from the hole 55 when the opening degree of the flapper 5 becomes larger than the predetermined small open state or less. Therefore, when the opening degree of the flapper 5 is large, the air resistance of the pair of protruding walls 45 is appropriately prevented from becoming excessive, and pressure loss can be reduced.

[0055] The present invention is not limited to the contents of the above-described embodiment. The specific configurations of the premixing device and each part of the combustion device according to the present invention can be freely designed and modified in various ways within the intended scope of the present invention.

[0056] The premixing passage is preferably, but not limited to, a venturi shape. The specific shapes, sizes, materials, etc. of the first and second blade portions, flappers, protruding wall portions, etc. are not limited to those in the above-mentioned embodiment. The first and second fuel gas outlets may not be provided one by one, but may be provided in multiples, for example. The shape, size, number, arrangement, etc. of the protruding wall portions may be appropriately changed in accordance with the specific configuration of the first fuel gas outlet. At least one protruding wall portion may be provided between the first flow path and the first fuel gas outlet, and is not necessarily provided in a pair.

[0057] The hole for avoiding interference between the flapper and the protruding wall portion does not have to be a through hole. For example, it may be a recessed hole (non-through hole) that is deeper than the height of the protruding wall portion and allows the protruding wall portion to enter. In the present invention, it is sufficient that the flapper and the protruding wall portion are in a relationship that avoids interference with each other when the flapper is in an open state below a predetermined opening degree, and the specific means for this purpose are not limited. As a means for making the flapper swingable, instead of using a metal shaft separate from the flapper, it is possible to use a means in which a convex portion serving as the swing center of the flapper is provided on one of the flapper or the support member for the flapper, and a concave portion into which the convex portion fits is provided on the other. Furthermore, it is also possible to configure the flapper to swing using the driving force of a motor, for example.

[0058] The fuel gas may be, for example, natural gas or LP gas, but the specific type is not important. The combustion device according to the present invention is not limited to a hot water device, but may be a combustion device for other purposes such as heating or incineration. In addition, the combustion device is not limited to a type in which the combustion gas advances downward, but may be a type in which the combustion gas advances upward, for example. [Explanation of symbols]

[0059] A Premixer B Combustion device 1 Fan 2 Burner section 3 Premixing channel 3a, 3b First and second flow paths 4 Premixing flow path forming member 40 Partition wall 41a, 41b First and second blade portions 45 Projecting wall part 45a Corner 45b Chamfered part 5. Flapper 55 Hole 8a, 8b First and second fuel gas flow paths 80a, 80b First and second fuel gas outlets 81 Fuel gas receiver

Claims

1. a premixing flow passage into which air is supplied from the outside and which mixes the air with a fuel gas to generate an air-fuel mixture; a partition wall portion that divides the premixing flow path into first and second flow paths arranged in parallel; first and second fuel gas outlets capable of discharging a fuel gas into the first and second flow paths by utilizing a negative pressure generated by an air flow in the first and second flow paths; A premixing device comprising: a first blade portion provided in the first flow passage, the first fuel gas outlet being provided facing a downstream side in an air flow direction; a protruding wall portion provided on the first blade portion so as to protrude from an edge portion of the first fuel gas outlet toward a downstream side in the air flow direction; a flapper that is located in the first flow passage downstream of the first blade portion in the air flow direction and that swings in a direction facing the first blade portion and is capable of opening and closing both the first flow passage and the first fuel gas outlet in accordance with an air flow rate in the premixing flow passage while avoiding interference with the protruding wall portion; It is equipped with a protruding wall portion that is configured to prevent air in the first flow path from flowing into the first fuel gas outlet when the flapper is in an open state at a predetermined opening degree or less.

2. 2. The premixing device of claim 1, a premixing device, wherein as a means for avoiding interference between the flapper and the protruding wall portion, the flapper is provided with a hole into which the protruding wall portion enters when the flapper is in an open state at or below the predetermined opening degree.

3. 3. The premixing device of claim 2, a protruding wall portion having a height allowing the protruding wall portion to escape from the hole portion of the flapper when the flapper is in an open state larger than the predetermined opening degree.

4. 4. The premixing device of claim 3, The hole of the flapper is an elongated hole extending in a specific direction from a base end side near a swing center of the flapper to a tip end side, a premixing device, wherein the protruding wall portion is in the form of a rib extending in a direction corresponding to the specific direction, and a flat or curved chamfered portion is provided at a corner of a tip of the protruding wall portion that is farther from a swing center of the flapper.

5. 2. The premixing device of claim 1, the protruding wall portion extends continuously along the first fuel gas outlet, and the length of the protruding wall portion is approximately the same as the length of the first fuel gas outlet.

6. 2. The premixing device of claim 1, There are x and y directions intersecting with the air flow direction, the first blade portion extends in a y direction so as to span between a part of an inner wall of the first flow passage and another part of the inner wall of the first flow passage, thereby dividing a part of the first flow passage into a pair of divided flow passages, and the first blade portion and the first fuel gas outlet are located between the pair of divided flow passages in the x direction, the protruding wall portion being a pair of protruding wall portions located on both edges in an x-direction of the first fuel gas outlet.

7. 7. The premixing device of claim 6, further comprising: the first blade portion does not have the protruding wall portion on both edges in a y direction of the first fuel gas outlet, and when the flapper is in an open state at or below the predetermined opening degree, the air in the first flow path can flow toward both edges in the y direction of the first fuel gas outlet.

8. 2. The premixing device of claim 1, a premixing flow path forming member that forms the premixing flow path; a second blade portion that is provided in the second flow passage such that one end is connected to the peripheral wall portion of the premixing flow passage forming member and the other end is connected to the first blade portion via the partition wall portion, and the second fuel gas outlet is provided facing a downstream side in the air flow direction; a fuel gas receiving portion that is provided on the peripheral wall portion of the premixing flow passage forming member and receives a supply of fuel gas from an outside; a second fuel gas flow passage provided in the second blade portion so as to be capable of directing a portion of the fuel gas supplied to the fuel gas receiving portion to the second fuel gas outlet; a first fuel gas flow passage extending from within the second blade portion into the first blade portion so as to be capable of guiding another portion of the fuel gas supplied to the fuel gas receiving portion to the first fuel gas outlet; The premixing device further comprises:

9. With fans, a premixer that is provided on the intake side of the fan and that generates a mixture of air and fuel gas and sends the mixture to the fan; a burner unit that receives the mixture from the fan and combusts the fuel gas; A combustion device comprising: A combustion system, comprising the premixing device according to any one of claims 1 to 8 as the premixing device.

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