Premixing device and combustion device equipped with the same

Abstract

To provide a premixing device capable of increasing a turndown ratio by means of a simple configuration while inhibiting disadvantages such as increase in pressure loss as much as possible.SOLUTION: A premixing device A comprises: a blade portion 41a that is arranged midway of a gas flow path 3a through which air flows, and that is provided with a fuel gas outlet 80a in a region near one end on a downstream side in an air flow direction; a pair of divided flow paths 30a that is configured in a state that a portion of the gas flow path 3a is divided by the blade part 41. The premixing device further comprises baffle portions 45a, 45b in a shape of a projection piece or step part, each of which is located on an inner peripheral surface of each divided flow path 30a and on an upstream side in an air flow direction of the fuel gas outlet 80a and projects inward of each divided flow path 30a. The baffle portion 45a, 45b is provided in at least a portion of an inner region Sa of each divided flow path 30a, and can increase a flow velocity of air flowing through an outer region Sb in each divided flow path 30a to be higher than a flow velocity of air passing through the inner region Sa.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] An example of a premixing device is shown in Figure 11. Figure 11 shows a configuration corresponding to Figure 6(c) of Patent Document 1. In the premixer Ae shown in the figure, a blade section 41a is provided in a gas flow passage 3a through which air supplied from the outside flows. The blade section 41a extends in a direction perpendicular to the paper surface of the figure, and at the location where the blade section 41a is provided, the gas flow passage 3a is divided into a pair of divided flow passages 30a sandwiching the blade section 41a. A fuel gas outlet 80a is provided in an area near one end on the downstream side of the blade section 41a in the air flow direction. With this configuration, it is possible to utilize the negative pressure generated by the air flow in the gas flow path 3a to cause fuel gas to flow from the fuel gas outlet 80a into the gas flow path, thereby generating a mixture of the fuel gas and air.

[0003] However, the above-described premixing device Ae has room for improvement, as described below.

[0004] That is, the air flowing into the gas flow passage 3a branches into a pair of divided flow passages 30a, and then merges at a position downstream of the blade portion 41a in the air flow direction, near the fuel gas outlet 80a. This type of air flow (the merge) makes it difficult to generate negative pressure at the position near the fuel gas outlet 80a, and an appropriate amount of fuel gas cannot be discharged from the fuel gas outlet 80a into the gas flow passage 3a, and the amount of fuel discharged tends to be insufficient. In this case, the mixture generated has an inappropriate mixture ratio of fuel lean, which is not preferable in terms of increasing the turndown ratio. This problem becomes more noticeable when the total air flow rate flowing through the gas flow passage 3a is small and the air flow speed is low, making it difficult to generate a strong negative pressure.

[0005] One possible solution to this problem is to reduce the opening area (flow area) of the pair of divided flow paths 30a to increase the air flow rate, but simply adopting such a solution would result in an increase in flow resistance of each divided flow path 30a, which would increase the pressure loss. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2022-99650 [Patent Document 2] Special Publication No. 62-35010 [Patent Document 3] JP 2003-130312 A [Patent Document 4] Patent No. 3686487 [Patent Document 5] Patent Publication No. 2022-3283 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been devised under the circumstances described above, and aims to increase the turndown ratio by a simple means while minimizing disadvantages such as an increase in pressure loss. The present invention has an object to provide a premixing device capable of performing the above-mentioned steps, and a combustion device equipped with the premixing device. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides the following technical solutions.

[0009] A premixing device provided according to a first aspect of the present invention includes a gas flow path forming member forming therein a gas flow path through which air supplied from outside flows, a blade portion disposed in a middle portion of the gas flow path and having a fuel gas outlet capable of causing a fuel gas to flow into the gas flow path by utilizing a negative pressure generated by the flow action of the air in an area near one end on the downstream side in the air flow direction, and a pair of separators arranged on both sides of the blade portion in an x ​​direction intersecting the air flow direction, the pair of separators being configured such that a part of the gas flow path is divided by the blade portion. and a split flow passage, further comprising a protrusion- or step-shaped baffle portion located on the inner circumferential surface of each of the divided flow passages upstream of the fuel gas outlet in the air flow direction and protruding inward of each of the divided flow passages, wherein this baffle portion is provided in at least a part of an inner region of each of the divided flow passages that is on the blade portion side, and is configured to be able to make the flow speed of air flowing through an outer region of each of the divided flow passages opposite the inner region faster than the flow speed of air passing through the inner region.

[0010] According to this configuration, the following effects can be obtained. First, the baffle portion acts to increase the flow rate of air passing through the outer regions of each divided flow path and flowing in the region far from the fuel gas outlet. This makes it possible to suppress the phenomenon in which the air branching off from each of the divided flow paths and flowing through the pair of divided flow paths join together at positions close to the opposing fuel gas outlets, that is, the phenomenon that prevents the fuel gas from flowing out from the fuel gas outlet to the gas flow path. As a result, according to the present invention, although the negative pressure caused by the air flow acting on the fuel gas outlet is reduced compared to the conventional art, based on the above-mentioned action, it is possible to increase the overall amount of fuel gas flowing out from the fuel gas outlet to the gas flow path compared to the conventional art. For this reason, according to the present invention, even when the air flow rate in the gas flow path is reduced and the air flow rate is slow, it is possible to cause an appropriate amount of fuel gas corresponding to the air flow rate to flow into the gas flow path, thereby suppressing the mixture from becoming an inappropriate fuel-lean mixture ratio, and increasing the turndown ratio. On the other hand, in the present invention, since the baffle portion is provided on the inner peripheral surface of each divided flow path, the opening area (flow path area) of each divided flow path is narrower by that amount compared to a case where the baffle portion is not provided. However, since the baffle portion is a protrusion or step-like portion protruding inward from the inner peripheral surface of each divided flow path, and the inner diameter of the long dimension region of each divided flow path is not reduced, it is possible to suppress an increase in the flow path resistance of each divided flow path. Furthermore, the baffle portion only needs to be provided in the inner region of each divided flow path on the blade portion side, and does not need to be provided around the entire circumference of the inner peripheral surface of each divided flow path, so that it is possible to further suppress an increase in the flow path resistance of each divided flow path (gas flow path). Therefore, the pressure loss of the air flow can also be reduced.

[0011] In the present invention, the baffle portion is preferably provided so as to avoid at least a part of the outer region of each of the divided flow channels.

[0012] With this configuration, it is possible to more effectively prevent an increase in flow resistance of each divided flow passage (gas flow passage), and to more effectively increase the flow speed of air flowing through the outer regions of each divided flow passage. That is, unlike the above configuration, if baffle sections are provided not only in the inner regions of each divided flow passage, but also over the entire outer regions, the opening area (flow passage area) of each divided flow passage becomes significantly smaller, which is disadvantageous in that flow passage resistance increases. The baffle portion provided is hardly effective in increasing the flow speed of the air flowing through the outer regions of each divided flow passage, and is actually detrimental. In contrast, the above-mentioned configuration makes it possible to appropriately avoid such a disadvantage.

[0013] In the present invention, preferably, the baffle portion has an air receiving surface facing upstream in the air flow direction, and is configured so that air proceeding along the inner circumferential surface of each of the divided flow paths from a position upstream in the air flow direction toward this air receiving surface can be caused to collide with the air receiving surface, thereby generating a vortex of the air.

[0014] According to this configuration, a vortex of air can be generated in the upstream region of the air flow direction of the air receiving surface of the baffle, but this vortex itself does not flow at high speed toward the downstream side of the air flow direction through each divided channel. Therefore, it is effective in slowing down the flow speed of air flowing through the inner region of each divided channel. Therefore, it is possible to more effectively suppress the phenomenon in which air branches off from each of a pair of divided channels and flows together near opposing positions of the fuel gas outlet.

[0015] In the present invention, preferably, when viewed in the air flow direction in the gas flow path, the inner circumferential surface of each of the divided flow paths includes a pair of first regions adjacent to the blade portion and facing each other while being spaced apart in a y direction intersecting the x direction, and the baffle portion is provided in at least one of the pair of first regions, and the tip edge of this baffle portion is inclined so that the closer it is to the blade portion in the x direction, the closer it is to the center of each of the divided flow paths in the y direction.

[0016] With this configuration, it is possible to make the air flowing through the inner regions of each divided flow passage flow toward the outer regions by utilizing the baffle portions with inclined leading edges (see also the explanation using FIG. 5 etc. described later). This makes it possible to more thoroughly prevent the phenomenon in which the air flowing through each of the pair of divided flow passages branches off and joins together near the opposing fuel gas outlets.

[0017] A premixing device provided according to a second aspect of the present invention comprises: a gas flow path forming member forming therein a gas flow path through which air supplied from the outside flows; a blade portion disposed in a middle portion of the gas flow path and provided with a fuel gas outlet in a region near one end on the downstream side in the air flow direction, the fuel gas outlet being capable of causing a fuel gas to flow into the gas flow path by utilizing negative pressure generated by the flow action of the air; and a pair of divided flow paths arranged on both sides of the blade portion in an x ​​direction intersecting the air flow direction, the pair of fuel gas outlets being provided so as to open to both side surfaces of the region near the one end of the blade portion and facing the downstream regions in the air flow direction of each of the pair of divided flow paths.

[0018] According to this configuration, the following effects can be obtained. That is, before the air that branches off from each of the pair of divided flow paths advances downstream of the blade portion in the air flow direction and joins with each other, it is possible to apply negative pressure due to the air flow to each of the pair of fuel gas outlets. Therefore, even if the air flow rate in the gas flow path is reduced and the air flow speed is slow, it is possible to discharge an appropriate amount of fuel gas corresponding to the air flow rate into the gas flow path, thereby preventing the mixture from becoming an inappropriate fuel-lean mixture ratio and increasing the turndown ratio. Meanwhile, since it is not necessary to narrow the opening area (flow path area) of each divided flow path, pressure loss in the air flow can be reduced.

[0019] In the present invention, it is also possible to combine the characteristic configuration of the premixing device provided according to the first aspect of the present invention with the characteristic configuration of the premixing device provided according to the second aspect of the present invention (Claim 5). According to such a configuration, a more preferable effect in solving the problem of the present invention can be obtained.

[0020] In the present invention, the fuel gas outlet preferably comprises a pair of fuel gas outlets that open to both side surfaces of the region near one end of the blade portion and face the downstream regions in the air flow direction of each of the pair of divided flow paths.

[0021] With this configuration, it is possible to apply negative pressure due to the air flow to each of the pair of fuel gas outlets at a stage before the air that has branched off from each of the pair of divided flow paths advances downstream of the blade section in the air flow direction and joins with each other. Therefore, even when the flow rate of air supplied to the gas flow path is low, an appropriate amount of fuel gas corresponding to the low flow rate can be more accurately caused to flow into the gas flow path.

[0022] In the present invention, preferably, the gas flow path and the fuel gas outlet are a first gas flow path and a first fuel gas outlet, respectively, and further include: a second gas flow path provided in the gas flow path forming member while being separated from the first gas flow path via a partition wall portion; an air inlet portion provided in the gas flow path forming member so as to enable air supplied from the outside to branch off and proceed into each of the first and second gas flow paths; a second fuel gas outlet capable of discharging fuel gas into the second gas flow path by utilizing negative pressure generated by the flow action of the air in the second gas flow path; and a flapper capable of closing the second gas flow path so that the air flows only through the first gas flow path of the first and second gas flow paths when the total air flow rate of the first and second gas flow paths is less than a predetermined value.

[0023] According to this configuration, the following effects can be obtained. That is, when the air flow rate in the gas flow path is greater than a predetermined amount, the flapper is opened to allow air to flow through both the first and second gas flow paths (first mode). In this first mode, fuel gas is discharged from both the first and second fuel gas outlets, and the air can be appropriately mixed with an appropriate amount of fuel gas corresponding to the flow rate. On the other hand, differently from that, when the air flow rate in the gas flow path is small and less than a predetermined amount, the flapper can be closed to allow air not to flow through the second gas flow path (second mode). In this second mode, fuel gas is discharged only from the first fuel gas outlet with respect to the air flowing through the first gas flow path, and the amount of fuel gas discharged can be reduced. In the present invention, when the air flow rate in the first gas flow path is significantly reduced when this second mode is set, the outflow of fuel gas can be promoted by the above-mentioned action of the blade portion (suppression of air merging at a position near the opposing first fuel gas outlet). Therefore, the above-mentioned configuration is more preferable in terms of increasing the turndown ratio.

[0024] A combustion device provided according to a third aspect of the present invention is a combustion device comprising a premixing device that generates a mixture by mixing air and fuel gas, and a burner unit that receives the mixture from the premixing device and burns the fuel gas, wherein the premixing device provided according to the first aspect of the present invention is used as the premixing device.

[0025] 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.

[0026] Further features and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments with reference to the accompanying drawings, in which: This will become clearer from the explanation of the form. [Brief description of the drawings]

[0027] [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] 5(a) is a front cross-sectional view of the premixing device shown in FIGS. 1 to 3 (corresponding to the cross-sectional portion of FIG. 5(a) IVa-IVa of the gas flow path forming member), (b) is a cross-sectional view of (a) taken along line IVb-IVb, and (c) is a front cross-sectional view showing the configuration when the flapper portion in the closed state shown in (a) is in the open state. [Diagram 5] 5(a) is a plan view of the gas flow path forming member of the premixing device shown in FIGS. 1 to 4, (b) is an enlarged view of portion Vb of (a), (c) is a partially sectional plan view of (b), and (d) is a partially sectional plan view of the configuration shown in (c) in which the baffle portion is omitted. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI of FIG. [Figure 7] 5(a)-5(v) are cross-sectional views of the premixing device shown in FIG. 1 to FIG. 3 (corresponding to a cross-sectional portion of the gas flow passage forming member taken along VII-VII in FIG. 5(a)). [Figure 8] FIG. 8(a) is an explanatory view of the operation of the baffle portion of the embodiment shown in FIGS. 1 to 7, and FIG. 8(b) is an explanatory view of the operation of a comparative example. [Figure 9] 9A and 9B show another example of the present invention, in which FIG. 9A is a partially sectional plan view of a gas flow path forming member, and FIG. 9B is a sectional view taken along line IXb-IXb of FIG. 9A. [Figure 10] 5A and 5B show another example of the present invention, in which (a) is a plan view of a gas flow path forming member, and (b) is a cross-sectional view taken along the line XX in (a). [Figure 11] FIG. 1 is a cross-sectional view showing an example of a conventional technique. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. For ease of understanding, elements that are the same as or similar to those in the prior art shown in FIG. 11 are given the same reference numerals as in FIG.

[0029] 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).

[0030] The details of the premixing device A will be described later, but a mixture (combustible mixture) of air and fuel gas is generated using this premixing device A, and this mixture is supplied to the burner section 2 via the fan 1. The burner section 2 has a perforated plate 21 having a plurality of vent holes 20 (flame holes) and is arranged in the 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 burned below the perforated plate 21. The combustion gas generated by the burner section 2 is heat-recovered by the heat exchanger 11. The heat exchanger 11 is provided with, for example, a primary heat exchanger 11a for sensible heat recovery and a secondary heat exchanger 11b for latent heat recovery, and the combustion gas acts on the primary heat exchanger 11a and the secondary heat exchanger 11b in sequence, and the hot water passing through these is heated. The hot water generated by this hot water heating is supplied to a desired hot water supply destination.

[0031] As shown in FIGS. 2 to 7, the premixing device A includes a device main body A0 and a flapper 5 attached to the device main body A0. The device main body A0 is provided with a gas flow path forming member 4. This gas flow path forming member 4 includes a cylindrical portion 49 in which first and second gas flow paths 3a and 3b (described later) are formed, a flange portion 48 connected to the upper end of the cylindrical portion 49, and a step portion 49 protruding from the outer surface of the cylindrical portion 49. The fuel gas supply pipe joint 70 and a fuel gas control plate 71 (described later) are attached to the base 44 via screw members 90, 91 such as screws.

[0032] As shown in FIG. 1, the premixing device A has a pipe joint 70 connected to a gas pipe 99, and receives a 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 by using a flange portion 48. When the fan 1 is driven, external air flows into the gas flow passage forming member 4 (inside the cylindrical portion 49). Due to the negative pressure caused by this air flow, the fuel gas flows out from first and second fuel gas outlets 80a, 80b, which will be 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.

[0033] 2, 3 and 7, a partition wall 40 that stands upright in the vertical direction (the air flow direction in this embodiment) and extends in the x direction intersecting the air flow direction is provided in the cylindrical portion 49 of the gas flow path forming member 4. As a result, first and second gas flow paths 3a, 3b are formed in the cylindrical portion 49, arranged horizontally with the partition wall 40 in between. Of the first and second gas flow paths 3a, 3b, the first gas flow path 3a corresponds to an example of a "gas flow path" in the claims. The partition wall 40 is disposed offset in the y direction (a direction intersecting the x direction and the air flow direction) from the center of the cylindrical portion 49, and the flow path area of ​​the first gas flow path 3a is smaller than the flow path area of ​​the second gas flow path 3b. However, the first and second gas flow paths 3a and 3b may have the same flow path area.

[0034] 4 to 6, the first and second gas flow paths 3a and 3b are provided with first and second blade portions 41a and 41b (portions with a dotted pattern in FIG. 5), and are further provided with first and second fuel gas outlets 80a and 80b on their upper surfaces, the outlets opening upward. Here, of the first and second blade portions 41a, 41b, the first blade portion 41a corresponds to an example of a "blade portion" in the claims. Of the first and second fuel gas outlets 80a, 80b, the first fuel gas outlet 80a corresponds to an example of a "fuel gas outlet" in the claims. The first and second blade portions 41a, 41b extend in the y direction so as to horizontally cross the first and second gas flow paths 3a, 3b, respectively, and one end of each of them is connected to the inner surface of the peripheral wall of the gas 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.

[0035] 4(a) and (c), the pipe joint portion 70 has therein a fuel gas receiving portion 81 which receives a supply of fuel gas from the outside, and the fuel gas supplied to this fuel gas receiving portion 81 passes through openings 71a, 71b of the fuel gas control plate 71 and the first and second fuel gas flow paths 8a, 8b, and is guided to the first and second fuel gas outlets 80a, 80b.

[0036] As described above, the fuel gas control plate 71 is attached to the base portion 44, and has two openings 71a, 71b facing the tip openings of the first and second fuel gas flow paths 8a, 8b. Depending on the opening area of ​​these openings 71a, 71b, it is possible to control the amount of fuel gas flowing from the fuel gas receiving portion 81 into the first and second fuel gas flow paths 8a, 8b.

[0037] The cylindrical portion 49 has a lower portion and an upper portion, which are connected to the first and second gas flow paths 3a and 3b. An air inlet section 3c and an air outlet section 3d are formed. When the fan 1 is driven, external air flows into the air inlet section 3c and then branches into the first and second gas flow paths 3a, 3b. As described above, negative pressure caused by the air flow in the first and second gas flow paths 3a, 3b causes fuel gas to flow 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 cylindrical section 49 from the air outlet section 3d.

[0038] As shown clearly in Figure 6, the first blade portion 41a divides a portion of the first gas flow path 3a into a pair of divided flow paths 30a, and in the x direction, the pair of divided flow paths 30a are arranged side by side on either side of the first blade portion 41a. The pair of divided flow paths 30a corresponds to an example of the "pair of divided flow paths" in the claims. In this embodiment, the pair of divided flow paths 30a is provided with baffle sections 45a and 45b as a configuration associated with the pair of divided flow paths, and this configuration is a major feature. However, the details will be described later.

[0039] A part of the second gas flow passage 3b is divided into a pair of divided flow passages 30b sandwiching the second blade portion 41b, but the pair of divided flow passages 30b does not correspond to the "pair of divided flow passages" in the claims. In this embodiment, the configuration using the baffle portions 45a, 45b is applied only to the first gas flow passage 3a side of the first and second gas flow passages 3a, 3b.

[0040] The flapper 5 operates in response to the air flow rate so that the opening degree is smaller when the total air flow rate of the first and second gas flow paths 3a, 3b is small than when the total air flow rate is large, and the objects of the opening and closing control are the second gas flow path 3b and the second fuel gas outlet 80b. More specifically, a shaft body 61 serving as a rotation fulcrum is inserted into the rear part of the flapper 5, and the shaft body 61 is supported by a pair of left and right support members 60. In addition, the pair of support members 60 are attached to a step portion 43 separately provided in the second gas flow path 3b using a screw member 92 or the like. As a result, the flapper 5 can rotate around the shaft body 61 on the upper side of the second blade portion 41b in response to the air flow rate. When the air flow rate is less than a predetermined value, the flapper 5 is closed by its own weight as shown in FIG. 4(a), and blocks the second gas flow path 3b and the second fuel gas outlet 80b. On the other hand, when the flow rate is equal to or higher than a predetermined value, for example as shown in FIG. 4(c), the flapper 5 is pushed up by the air flow, and the second gas flow passage 3b and the second fuel gas outlet 80b are opened. In this embodiment, the flapper 5 includes a pair of fin portions 55 that can be disposed close to each other via a gap 97 on both sides of the second blade portion 41b (see FIG. 4(b)). However, the present invention is not limited to this.

[0041] As shown clearly in Figures 5 to 7, for example, two baffle portions 45a, 45b are provided on the inner circumferential surface of each divided flow passage 30a of the first gas flow passage 3a (shown in light ink in Figure 5(c)). The baffle portions 45a, 45b are portions of each divided flow passage 30a that are intended to increase the flow speed of air flowing through the outer region Sb on the opposite side relative to the flow speed of air flowing through the inner region Sa on the first blade portion 41a side (the specific functions and operations will be described in detail later).

[0042] The baffle portions 45a, 45b are located on the inner circumferential surface of each divided flow passage 30a upstream of the first fuel gas outlet 80a in the air flow direction, and are in the form of a protrusion or step protruding inward of each divided flow passage 30a. As shown in Figs. 6 and 7, the baffle portions 45a, 45b have an air receiving surface 450 facing downward (upstream of the air flow direction). protrudes in a substantially horizontal direction from a general portion of the inner circumferential surface of each divided flow passage 30a.

[0043] In the plan view or plan cross-sectional view (viewed in the air flow direction) shown in Figures 5(b) and (c), the baffle portions 45a, 45b are arranged to face each other with a space therebetween in the y direction, and at least a portion of the baffle portions 45a, 45b is located in the inner region Sa of each divided flow passage 30a. The baffle portions 45a, 45b are arranged to avoid the central portion in the longitudinal direction (y direction) of the first blade portion 41a. More specifically, the inner peripheral surface of each divided flow passage 30a includes a pair of first regions 30a' adjacent to the first blade portion 41a and facing each other with a space therebetween in the y direction. In contrast, the baffle portions 45a, 45b are provided in each of the pair of first regions 30a'. Further, the leading edges 45a', 45b' of the baffle portions 45a, 45b are inclined in the x direction so that the closer they are to the first blade portion 41a, the closer they are to the center of each divided flow passage 30a in the y direction. The baffle portions 45a, 45b are arranged to avoid at least a part of the outer region Sb of each divided flow path 30a (the outer region Sb has a portion where the baffle portions 45a, 45b are not provided).

[0044] Next, the operation of the premixing device A and the combustion device B equipped with the same will be described.

[0045] At the start of the driving combustion of the burner section 2 of the combustion device B and during the subsequent normal driving combustion, the driving speed of the fan 1 is changed and the flow rate of the mixture supplied from the premixing device A to the burner section 2 is changed, thereby controlling the driving combustion firepower of the burner section 2. Here, when the driving speed of the fan 1 is low and the air flow rate in the gas flow path forming member 4 is low, as shown in FIG. 4(a), the flapper 5 is in a closed state, and air does not flow in the second gas flow path 3b, but only in the first gas flow path 3a. In this case, when the air flow rate in the first gas flow path 3a becomes considerably low, the negative pressure due to the air flow does not act strongly on the first fuel gas outlet 80a. On the other hand, if a phenomenon occurs in which the air passing through each of the pair of divided flow paths 30a of the first gas flow path 3a joins at a position near the opposing first fuel gas outlet 80a in a large proportion, the amount of fuel gas flowing out from the first fuel gas outlet 80a is further reduced, as in the conventional technology described with reference to FIG. 11. In contrast, according to this embodiment, it is possible to appropriately suppress such a problem as described below.

[0046] That is, due to the action of the baffle portions 45a, 45b, the flow velocity of the air passing through the outer region Sb of each divided flow passage 30a becomes faster than the flow velocity of the air passing through the inner region Sa. To explain this point, in the comparative example of FIG. 8(b), the baffle portions 45a, 45b are not provided on the inner peripheral surface of the divided flow passage 30a. In this case, the air simply flows along the inner peripheral surface of the divided flow passage 30a. In contrast, in this embodiment, as shown in FIG. 8(a), a part of the air flowing along the inner peripheral surface of the divided flow passage 30a collides with the baffle portion 45a (45b), and a vortex is generated in the upstream region of the baffle portion 45a (45b) in the air flow direction. The baffle portion 45a (45b) has an air receiving surface 450 facing the upstream side in the air flow direction, which is advantageous in generating the vortex appropriately.

[0047] When the above-mentioned vortex flow occurs, the following effects are obtained. First, the vortex itself does not proceed downstream. Also, the flow speed of the air flowing near the vortex is affected by the vortex and is likely to decrease. Meanwhile, the baffle sections 45a, 45b are provided in the inner region Sa of each divided flow passage 30a, and the vortex occurs in this region. Therefore, the flow speed of the air passing through the inner region Sa becomes slower, and the flow speed of the air passing through the outer region Sb becomes relatively faster. Secondly, as shown in FIG. 8(a), the air flows from the upstream side toward the baffle portion 45a (45b). Most of the air moving from the first blade portion 41a moves in such a way that it bulges out to the side of the vortex, and its moving direction changes so that it moves closer to the inside of the divided flow passage 30a than its original moving direction. Meanwhile, the leading edges 45a', 45b' of the baffle portions 45a, 45b are in a predetermined inclined state as described with reference to Figs. 5(b) and (c). Therefore, the air passing near the leading edges 45a', 45b' of the baffle portions 45a, 45b flows in the direction opposite to the first blade portion 41a, as shown by arrows Na and Nb. Therefore, the air flow rate in the outer region Sb of each divided flow passage 30a increases, and the air flow speed in the outer region Sb increases. Unlike the present embodiment, if a portion of the baffle portions 45a, 45b were extended to the outer region Sb, there would be a risk that the portion of the baffle portions 45a, 45b would act to cause the air moving through the outer region Sb to flow toward the inner region Sa. In the present embodiment, such a risk can be appropriately avoided.

[0048] As described above, when the flow velocity of the air in the outer region Sb is increased, the air that has branched off from the pair of divided flow paths 30a and flowed therethrough is prevented from joining at the opposing positions near the first fuel gas outlet 80a. The joining of the air described above hinders the outflow of the fuel gas from the first fuel gas outlet 80a to the first gas flow path 3a, but this is appropriately prevented. As a result, according to this embodiment, the negative pressure of the air flow acting on the first fuel gas outlet 80a may be slightly reduced compared to the case where the baffle portions 45a and 45b are not provided, but the amount of fuel gas flowing out from the first fuel gas outlet 80a can be increased overall. Therefore, even when the air flow rate is low, an appropriate amount of fuel gas corresponding to the air flow rate can be mixed with the air to obtain a mixture with an appropriate mixture ratio, and the turndown ratio can be increased.

[0049] On the other hand, in this embodiment, although the baffle portions 45a, 45b are provided on the inner circumferential surface of each divided flow passage 30a, the baffle portions 45a, 45b are protruding or stepped, and do not reduce the inner diameter of the long dimension area of ​​each divided flow passage 30a. In addition, the baffle portions 45a, 45b are not provided long over the entire circumference of the inner circumferential surface, but are provided partially, such as not being provided on the inner circumferential surface of the outer region Sb. Therefore, the flow resistance of each divided flow passage 30a does not increase significantly. Therefore, the pressure loss of the air flow can be reduced.

[0050] Unlike the above, when the driving speed of the fan 1 is set to high speed and the air flow rate in the gas flow path forming member 4 is greater than a predetermined value, the flapper 5 opens as shown in FIG. 4(c), and air also flows into the second gas flow path 3b. Here, the second gas flow path 3b is not provided with a means corresponding to the baffle portions 45a and 45b described above. However, when air flows into the second gas flow path 3b, the air flow rate is high, and the second fuel gas outlet 80b is strongly negatively pressurized by the air flow, so there is no or almost no risk of a shortage in the amount of fuel gas flowing out. Therefore, although the second gas flow path 3b is not provided with a means corresponding to the baffle portions 45a and 45b, this does not cause any particular inconvenience.

[0051] 9 and 10 show another embodiment of the present invention. In these figures, elements that are the same as or similar to those in the above embodiment are given the same reference numerals as in the above embodiment, and repeated explanations will be omitted.

[0052] In the embodiment shown in Fig. 9, a pair of baffle portions 45c (shown in light black in Fig. 9(a)) are provided on both side surfaces of the first blade portion 41a. The both side surfaces correspond to a part of the inner circumferential surface of the first gas flow path 3a.

[0053] According to this embodiment, the air that has traveled toward the baffle portion 45c changes direction in the x direction, as indicated by the arrow Nc, in a direction away from the first blade portion 41a. Therefore, the air passing through the pair of divided flow paths 30a is prevented from joining together at a position near the opposing first fuel gas outlet 80a. This allows the fuel gas to flow appropriately from the first fuel gas outlet 80a. If the width Lc of the baffle portion 45c is too large, the location where the air flows will be too far from the first fuel gas outlet 80a, making it impossible to effectively apply negative pressure to the first fuel gas outlet 80a. However, by setting the width Lc to an appropriate value, it is possible to appropriately avoid this.

[0054] In the embodiment shown in Fig. 10, a pair of first fuel gas outlets 80a are provided as first fuel gas outlets, opening sideways, on both side surfaces of an area near the upper end of the first blade portion 41a (an area near one end on the downstream side in the air flow direction). The pair of first fuel gas outlets 80a faces the downstream areas of the pair of divided flow channels 30a in the air flow direction. A gas flow channel blocking wall 41c is provided above and between the pair of first fuel gas outlets 80a, so that the gas in the first fuel gas flow channel 8a is prevented from flowing out from a location other than the pair of first fuel gas outlets 80a opening sideways.

[0055] According to this embodiment, before the air flows branching off from the pair of divided flow paths 30a advance downstream in the air flow direction beyond the first blade portion 41a and join together, a negative pressure due to the air flow can be applied to each of the pair of first fuel gas outlets 80a. Therefore, when the air flow rate in the first gas flow path 3a is low, the outflow amount of fuel gas is more reliably prevented from becoming too small.

[0056] 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.

[0057] The gas flow path (the first gas flow path in the above embodiment) in the present invention is preferably, but not limited to, a Venturi shape. Also, the gas flow path forming member does not necessarily have to have the first and second gas flow paths, and may have, for example, only one gas flow path. In addition, when there are first and second gas flow paths and a flapper is provided in the second gas flow path as in the above-described embodiment, the flapper can be, for example, a type of flapper that is opened and closed by a motor.

[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 Sa Inner region (of the divided channel) Sb Outer region (of the divided channel) 1 Fan 2 Burner section 3a First gas flow path (gas flow path) 3b Second gas flow path 30a Divided channel 30a' First region (of the inner circumferential surface of the divided flow passage) 4 Gas flow path forming member 40 Partition wall 41a, 41b First and second blade portions 45a~45c Baffle section 45a', 45b' Tip edge (of baffle) 450 Air bearing surface 5. Flapper 80a First fuel gas outlet (fuel gas outlet) 80b second fuel gas outlet

Claims

1. a gas flow path forming member that forms a gas flow path therein through which air supplied from the outside flows; a blade portion that is disposed in the middle of the gas flow path and has a fuel gas outlet that is provided in a region near one end on a downstream side in an air flow direction and that is capable of causing a fuel gas to flow into the gas flow path by utilizing a negative pressure generated by an action of the air flow; a pair of divided flow paths arranged on both sides of the blade portion in an x ​​direction intersecting the air flow direction; A premixing device comprising: the fuel gas supply pipe further includes a baffle portion having a protrusion or step shape that protrudes inwardly of each of the divided flow paths and is located upstream of the fuel gas outlet in the air flow direction on an inner circumferential surface of each of the divided flow paths, This premixing device is characterized in that the baffle portion is provided in at least a part of the inner region of each of the divided flow paths, which is on the blade portion side, and is configured to be able to make the flow speed of air flowing through the outer region of each of the divided flow paths opposite the inner region faster than the flow speed of air passing through the inner region.

2. 2. The premixing device of claim 1, A premixing device, wherein the baffle portion is provided so as to avoid at least a portion of the outer region of each of the divided flow paths.

3. 2. The premixing device of claim 1, The baffle portion has an air receiving surface facing upstream in the air flow direction, This premixing device is configured so that air proceeding along the inner circumferential surfaces of the divided flow paths from a position upstream of the air flow direction toward the air receiving surface can be collided with the air receiving surface, thereby generating a vortex of the air.

4. 4. The premixing device of claim 3, When viewed in an air flow direction in the gas flow path, the inner circumferential surface of each of the divided flow paths includes a pair of first regions that are adjacent to the blade portion and are spaced apart from each other in a y direction intersecting the x direction, and that face each other, the baffle portion is provided in at least one of the pair of first regions, and a leading edge of the baffle portion is inclined so as to be positioned closer to the center of each of the divided flow paths in the y direction as it approaches the blade portion in the x direction.

5. 2. The premixing device of claim 1, the premixing device comprising a pair of fuel gas outlets that open onto both side surfaces of the blade portion in the region near the one end thereof and face downstream regions of the pair of divided flow paths in the air flow direction,

6. a gas flow path forming member that forms a gas flow path therein through which air supplied from the outside flows; a blade portion that is disposed in the middle of the gas flow path and has a fuel gas outlet that is provided in a region near one end on a downstream side in an air flow direction and that is capable of causing a fuel gas to flow into the gas flow path by utilizing a negative pressure generated by an action of the air flow; A part of the gas flow path is divided by the blade portion, and a pair of dividing members are arranged on both sides of the blade portion in an x ​​direction intersecting the air flow direction. a tubular flow path; A premixing device comprising: the premixing device comprising a pair of fuel gas outlets that open onto both side surfaces of the blade portion in the region near the one end thereof and face downstream regions of the pair of divided flow paths in the air flow direction,

7. 2. The premixing device of claim 1, the gas flow path and the fuel gas outlet are a first gas flow path and a first fuel gas outlet, respectively; a second gas flow path provided in the gas flow path forming member in a state where the second gas flow path is separated from the first gas flow path via a partition wall; an air inlet portion provided in the gas flow path forming member so that air supplied from the outside can be branched into the first and second gas flow paths and travel therethrough; a second fuel gas outlet capable of discharging a fuel gas into the second gas flow path by utilizing a negative pressure generated by an action of the air flow in the second gas flow path; a flapper capable of closing the second gas flow path when a total air flow rate of the first and second gas flow paths is less than a predetermined value, so that the air flows only through the first gas flow path of the first and second gas flow paths; The premixing device further comprises:

8. A premixing device that generates a mixture of air and fuel gas; a burner unit that receives the mixture from the premixing device and burns the fuel gas; A combustion device comprising: A combustion system, comprising the premixing device according to any one of claims 1 to 7 as the premixing device.

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