Premixing device and combustion apparatus equipped therewith

Abstract

To provide a premixing device having a high turndown ratio and excellent performance for maintaining an air-fuel mixture at an appropriate air-fuel ratio.SOLUTION: A premixing device A includes first and second fuel gas outflow ports 80a, 80b enabling fuel gas to flow out to first and second flow passages 3a, 3b by using negative pressure generated by an air flow in the first and second flow passages 3a, 3b partitioned by a partition wall part 40 of a premixing flow passage 3. The premixing device further includes: a first blade part 41a provided in the first flow passage 3a and having the first fuel gas outflow port 80a facing the downstream side in an air flowing direction; a flapper 5 that has an opening changing in accordance with an air flow rate and opens / closes both of the first flow passage 3a and the first fuel gas outflow port 80a; and a pair of fin parts 55 provided in the flapper 5 in a projecting manner so as to be arranged while sandwiching the first fuel gas outflow port 80a and the first blade part 41a and forming gaps 97 between the fin parts and the first blade part 41a.SELECTED DRAWING: Figure 4

Description

Technical Field

[0003]

[0001] The present invention relates to a premixing device and a combustion device provided with the same. Here, "premixing" is a process of pre-mixing air and fuel gas to generate a combustible mixture for the purpose of performing premixing combustion.

Background Art

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

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

[0004] However, the aforementioned prior art still had room for improvement, as described below.

[0005] In other words, when the flapper changes from a closed state to an open state, the effective flow area of ​​the premixing channel changes abruptly. As a result, the flow velocity of the airflow that was already present in the second channel may decrease sharply. This can cause a sudden change in the mixture ratio, potentially resulting in an inappropriate mixture ratio that is lean fuel.

[0006] Furthermore, the flapper only opens and closes the first passage, and the first fuel gas outlet remains open. For this reason, even if the flapper switches the first passage from an open state to a closed state, there is a risk that fuel gas may leak out of the first fuel gas outlet for a period of time afterward. In addition, the pressure fluctuations in the first passage due to the influence of the airflow in the second passage may cause air in the first passage to flow into (backflow) the first fuel gas outlet, or fuel gas may leak out unnecessarily from the first fuel gas outlet. This makes it difficult to maintain the mixture at the desired appropriate mixing ratio. One way to resolve this is to provide an additional flapper for opening and closing the first fuel gas outlet (see Patent Document 2). However, such a method requires the use of two flappers, one for the first flow path and one for the first fuel gas outlet, which increases the total number of parts and thus the manufacturing cost.

[0007] Furthermore, in the aforementioned prior art (both Patent Documents 1 and 2), for example, when the opening of the flapper is not very large and the airflow rate in the first channel is relatively low, the air in the first channel Because the flow is slow, it is difficult to apply a strong negative pressure to the first fuel gas outlet. Therefore, in such cases, the amount of fuel gas flowing out from the first fuel gas outlet may be insufficient, potentially resulting in an inappropriate mixture ratio. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2021-99204 [Patent Document 2] U.S. Patent No. 9677759 [Overview of the project] [Problems that the invention aims to solve]

[0009] The present invention was conceived under the circumstances described above, and its objective is to provide a premixing device and a combustion device equipped therewith that can achieve a high turndown ratio and excellent performance in maintaining the air-fuel mixture at an appropriate mixing ratio using simple means. [Means for solving the problem]

[0010] To solve the above problems, the present invention employs the following technical measures.

[0011] A premixing device provided in a first aspect of the present invention comprises: a premixing channel into which air is supplied from the outside and mixed with fuel gas to generate a fuel mixture; a partition wall portion that divides the premixing channel into first and second channels arranged in a direction intersecting the airflow direction; and first and second fuel gas outlets that can discharge fuel gas into the first and second channels by utilizing the negative pressure generated by the airflow in the first and second channels, wherein the premixing device comprises a first blade portion provided in the first channel and provided so that the first fuel gas outlet faces the downstream side in the airflow direction, and the The device further comprises a flapper positioned downstream of the first blade portion in the airflow direction of the flow path, which is pivotable to open and close both the first flow path and the first fuel gas outlet, and whose opening degree changes according to the airflow rate such that the opening degree is smaller when the airflow rate of the premixing flow path is low than when it is high; and a pair of fin portions that protrude from the flapper so as to sandwich the first fuel gas outlet and the first blade portion in a direction intersecting the airflow direction, and which form a gap between them that allows air to pass through.

[0012] With this configuration, when the air flow rate supplied to the premixing channel is low, the flapper closes the first channel, and the fuel gas flowing out from the second fuel gas outlet is mixed with the air flowing through the second channel. On the other hand, when the air flow rate is high, air also flows through the first channel, and the fuel gas flowing out from the first fuel gas outlet is mixed with this air. Therefore, as with Patent Document 1, it is possible to increase the turndown ratio. Furthermore, the present invention provides the following effects. Firstly, the flapper can not only open and close 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, making it possible to appropriately prevent unnecessary leakage of fuel gas from the first fuel gas outlet afterward. As a means of achieving this, it is not necessary to use two flappers, one for the first flow path and one for the first fuel gas outlet, thus simplifying the overall configuration and reducing manufacturing costs. Secondly, when the flapper changes from a closed state to an open state, at the initial stage of opening the flapper, a portion of the first flow path is still blocked by the pair of fins, thereby substantially preventing a sudden change in the effective flow area of ​​the premixing flow path. Therefore, when the flapper changes from a closed state to an open state, the airflow that has been occurring in the second flow path prior to that point... This prevents a sudden drop in flow velocity. As a result, it is possible to effectively suppress the mixture ratio from becoming an inappropriate lean fuel mixture ratio. Thirdly, in the case where a structure is adopted in which the first and second fuel gas passages are in communication with each other, when the flapper changes from a closed state to an open state, there is a risk that the air in the first passage will flow back into the first and second fuel gas passages from the first fuel gas outlet due to the negative pressure generated in the second passage. In contrast, in the present invention, the pair of fins creates resistance to such airflow. Therefore, the phenomenon of backflow is suppressed, and the mixture becoming an inappropriate fuel-lean mixture ratio is more effectively suppressed. Fourth, when the flapper opens from a closed state, it is possible to generate a high-velocity airflow in the gap between the pair of fin sections and the first blade section. Furthermore, this airflow can be generated in the vicinity regions on both sides of the first fuel gas outlet. Therefore, a strong negative pressure can be applied to the first fuel gas outlet, ensuring a sufficient amount of fuel gas flows into the first flow path. Consequently, the mixture is less likely to have an inappropriate lean fuel mixture ratio.

[0013] In the present invention, preferably, in a view in the direction of the pivot center line of the flapper, at least the region of each fin portion closer to the flapper has a tip that is arc-shaped with respect to the pivot center, and its radius is greater than or equal to the distance from the pivot center to the first fuel gas outlet.

[0014] With this configuration, when the flapper begins to swing from a closed state to an open state, at least the region of each fin closest to the flapper can be reliably positioned on both sides of the first fuel gas outlet and the first blade, thereby appropriately achieving the intended effect of the present invention. On the other hand, as a means of achieving such an effect, it is not necessary to form each fin in an unnecessarily large size and complex shape.

[0015] In the present invention, preferably, when the flapper is fully open, each fin portion is located downstream of the first blade portion in the airflow direction and is not present on either side of the first blade portion.

[0016] This configuration yields the following effects: In other words, if the airflow rate in the first passage becomes considerably high and the flapper is fully open, and the fins are still located on either side of the first blade, then the fins will create significant resistance that obstructs the airflow. The above configuration makes it possible to appropriately prevent this. Furthermore, if the airflow rate in the first passage is high enough that the flapper is fully open, the velocity of the airflow is inherently fast and can generate a strong negative pressure. Therefore, even if no gap is formed between the fins and the first blade, it is possible to appropriately discharge an appropriate amount of fuel gas from the first fuel gas outlet.

[0017] In the present invention, preferably, a protruding step portion is provided on the inner surface of the peripheral wall of the first flow path and partially protrudes closer to the center of the first flow path than other general portions of the inner surface of the peripheral wall, and a support member is attached to the protruding step portion and disposed within the first flow path, and supports the flapper so as to be swingable.

[0018] With this configuration, the flapper can be swingably supported using the support member placed in the first flow path, which is preferable for achieving overall compactness. Unlike the above configuration, if the flapper support member is attached outside the first flow path, a sealing means is required to prevent fuel gas from leaking to the outside, but with the above configuration, such a necessity can be eliminated.

[0019] In the present invention, preferably, a premixing channel forming member that forms the premixing channel; a second blade portion provided in the second channel such that one end is connected to the peripheral wall of the premixing channel forming member and the other end is connected to the first blade portion via the partition wall, and the second fuel gas outlet is provided facing downstream in the direction of airflow; a fuel gas receiving portion provided in the peripheral wall of the premixing channel forming member and receiving fuel gas from the outside; a second fuel gas channel provided in the second blade portion so as to be able to guide a portion of the fuel gas supplied to the fuel gas receiving portion to the second fuel gas outlet; and a first fuel gas channel provided extending from the second blade portion to the first blade portion so as to be able to guide another portion of the fuel gas supplied to the fuel gas receiving portion to the first fuel gas outlet.

[0020] According to such a configuration, by utilizing the first and second fuel gas flow paths provided in the first and second blade portions, it is possible to appropriately and reasonably guide the fuel gas from the fuel gas receiving portion provided on the outer surface portion of the premixing flow path forming member to the first and second fuel gas outlets. The fuel gas receiving portion may be provided at one location, and it is not necessary to provide a plurality of them corresponding to each of the first and second fuel gas outlets. Therefore, it is suitable for simplifying the overall configuration and reducing the manufacturing cost. Also, in the above configuration, the configuration of the second blade portion and the second fuel gas outlet provided in the second blade portion is similar to the configuration of the first blade portion and the first fuel gas outlet provided in the first blade portion. According to such a configuration, when air flows near the first and second blade portions, it is preferable for effectively generating a negative pressure and strongly acting this negative pressure on the first and second fuel gas outlets to sufficiently ensure the outflow amount of the fuel gas.

[0021] In the present invention, preferably, the second blade portion has a greater thickness in the air flow direction than the first blade portion, and in the second blade portion, the first and second fuel gas flow paths are provided in an overlapping arrangement in the air flow direction.

[0022] According to such a configuration, it is possible to suppress the first and second blade portions from becoming wide (a shape having a wide width in a direction intersecting the air flow direction), and to appropriately provide the first and second fuel gas flow paths in the first and second blade portions while ensuring the flow path opening areas of the first and second flow paths.

[0023] The combustion device provided by the second aspect of the present invention is a combustion device including a fan, a premixing device provided on the intake side of the fan and generating a mixture of air and fuel gas and feeding it to the fan, and a burner receiving the supply of the mixture from the fan and burning the fuel gas, wherein the premixing device provided by the first aspect of the present invention is used as the premixing device.

[0024] With this configuration, the same effects as those described for the premixing apparatus provided by the first aspect of the present invention can be obtained.

[0025] Other features and advantages of the present invention will become more apparent from the description of embodiments of the invention given below with reference to the accompanying drawings. [Brief explanation of the drawing]

[0026] [Figure 1] This is a schematic diagram illustrating an example of a combustion apparatus equipped with a premixing device according to the present invention. [Figure 2] Figure 1 is a perspective view of the premixing apparatus. [Figure 3] Figure 2 is an exploded perspective view. [Figure 4] (a) is a front cross-sectional view of the premixing apparatus shown in Figure 1, (b) is a cross-sectional view of the premixing apparatus at a different location than (a), and (c) is a cross-sectional view of the IVc-IVc main section (right side cross-sectional view) of (b). [Figure 5] (a) is a front cross-sectional view showing the flapper of the premixing apparatus shown in Figure 4(a) in a half-open state, and (b) is a cross-sectional view of the main right side of (a). [Figure 6] (a) is a front cross-sectional view showing the flapper of the premixing apparatus shown in Figure 4(a) in the fully open state, and (b) is a cross-sectional view of the main right side of (a). [Figure 7] (a) is a plan view of the premixing channel forming member of the premixing apparatus shown in Figures 2 and 3, and (b) is a plan cross-sectional view thereof. [Figure 8] (a) is a perspective view of the flapper of the premixing apparatus shown in Figures 1 and 2, (b) is a front view thereof, and (c) is a right side view thereof. [Figure 9] (a) is a perspective view showing another example of a flapper, (b) is a front view thereof, and (c) is a right side view thereof. [Figure 10](a) is a plan cross-sectional view showing another example of a premixing apparatus according to the present invention, and (b) is an exploded plan cross-sectional view of (a). [Modes for carrying out the invention]

[0027] Preferred embodiments of the present invention will be described in detail below with reference to the drawings.

[0028] Figure 1 shows the hot water supply system WH. This hot water supply system WH is a hot water supply system and consists of a premixing unit A, a combustion unit B (premixed combustion unit) which is configured by combining the premixing unit A with a fan 1 and a burner 2, and a primary heat exchanger 11a and a secondary heat exchanger 11b which are configured by combining the combustion unit B.

[0029] Details of the premixing device A will be described later, but this premixing device A is used to generate a mixture of air and fuel gas (combustible mixture), and this mixture is supplied to the burner 2 via the fan 1. The burner 2 is configured to have a porous plate 21 having a plurality of vent holes 20 (flame holes) and is housed in the case 10. The burner 2 is equipped with an ignition plug and a flame detection sensor (not shown). The mixture passes through the plurality of vent holes 20 and burns below the porous plate 21. The combustion gas generated by the burner 2 acts sequentially on the primary heat exchanger 11a for sensible heat recovery and the secondary heat exchanger 11b for latent heat recovery, and the hot water passing inside these primary heat exchangers 11a and secondary heat exchangers 11b is heated. This generates hot water, which is supplied to the desired hot water destination.

[0030] As clearly shown in Figures 2 to 4, the premixing device A comprises a main body A0, a flapper 5 assembled to the main body A0, and a pair of left and right support members 60 and a shaft 61 for pivotably supporting the flapper 5.

[0031] The main body of the device A0 includes a premixing channel forming member 4 and a pipe joint 70. The premixing channel forming member 4 comprises a cylindrical portion 49 that forms a venturi-shaped premixing channel 3 inside, a flange portion 48 connected to the upper end of the cylindrical portion 49, and a stepped base portion 44 protruding from the outer surface of the cylindrical portion 49. The pipe joint portion 70 is attached to the base portion 44 using screw members 90 such as screws, sandwiching the fuel gas control plate 71 which will be described later.

[0032] As shown in Figure 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 unit (not shown) via a pressure equalizing valve (zero governor) V1. On the other hand, the premixing device A is directly connected to the intake side of the fan 1 using a flange portion 48, or indirectly connected by piping. When the fan 1 is driven, outside air flows into the premixing passage 3 from the opening at one end and flows toward the opening at the other end. Due to the negative pressure effect caused by this airflow, the first and second fuel gas flows, which will be described later, enter the premixing passage 3. Fuel gas flows out from outlets 80a and 80b, creating a mixture of air and fuel gas which is then drawn into fan 1.

[0033] As clearly shown in Figure 4(b), the premixing channel 3 is provided with a partition wall 40 extending in the vertical direction (corresponding to the airflow direction), and a portion of the premixing channel 3 is partitioned by the partition wall 40 into first and second channels 3a and 3b that are aligned horizontally (corresponding to an example of a direction intersecting the airflow direction). These first and second channels 3a and 3b may have the same volume, but in this embodiment, the partition wall 40 is positioned off-center from the center of the premixing channel 3 to the left side of Figure 4(b), so the volume of the second channel 3b is smaller than the volume of the first channel 3a.

[0034] As clearly shown in Figures 4(a) and 7, the premixing channel 3 is further provided with first and second blade sections 41a and 41b (shown as the halftone pattern in Figure 7), which are equipped with first and second fuel gas outlets 80a and 80b. The first and second blade sections 41a and 41b extend horizontally across the first and second flow paths 3a and 3b, respectively, with one end of each 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 section 49), and their other ends connected to each other across the partition wall section 40. As shown in Figure 7, the first and second flow paths 3a and 3b have openings on both the left and right sides of the first and second blade sections 41a and 41b, allowing air to pass through these openings. The first and second blade portions 41a and 41b have first and second main surface portions 42a and 42b which are upward-facing surfaces facing downstream in the direction of airflow, and first and second fuel gas outlets 80a and 80b are provided in these portions with upward-facing openings.

[0035] In Figure 4(a), the pipe joint 70 has a fuel gas receiving section 81 inside which it receives fuel gas from the outside. The fuel gas supplied to this fuel gas receiving section 81 is guided to the first and second fuel gas outlets 80a and 80b through the openings 71a and 71b of the fuel gas control plate 71, and the first and second fuel gas passages 8a and 8b.

[0036] Here, the second fuel gas passage 8b is provided inside the second blade portion 41b and the base portion 44, while the first fuel gas 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 greater vertical thickness than the first blade portion 41a, and within the second blade portion 41b, the first and second fuel gas passages 8a and 8b overlap in the vertical height direction.

[0037] This configuration simplifies the fuel gas supply structure to the first and second fuel gas outlets 80a and 80b. Furthermore, by overlapping the first and second fuel gas passages 8a and 8b in the vertical direction, the horizontal width of the second blade section 41b (width L1 shown in Figure 7) is kept from becoming too large, and sufficient area is secured for the opening regions on both the left and right sides of the second blade section 41b.

[0038] As clearly shown in Figure 3, the fuel gas control plate 71 is attached to the base portion 44 using screw members 91 such as screws, and has two upper and lower openings 71a, 71b facing the front openings of the first and second fuel gas passages 8a, 8b. The amount of fuel gas flowing from the fuel gas receiving portion 81 to the first and second fuel gas passages 8a, 8b can be controlled by the opening area of ​​these openings 71a, 71b. In this embodiment, as previously described, since the volume of the second passage 3b is smaller than that of the first passage 3a, the second fuel gas outlet 80b and the upper opening 71b corresponding to the second passage 3b are... It is set to have a smaller area than the opening 71a.

[0039] Furthermore, by using the fuel gas control plate 71, it becomes possible to easily accommodate changes in the type of fuel gas. Specifically, multiple types of fuel gas control plates 71 are prepared, each with openings 71a and 71b set to an opening area corresponding to a predetermined number of fuel gases. When assembling the premixing device A, it is convenient to select and use the fuel gas control plate 71 that corresponds to the type of fuel gas actually used from among the multiple types of fuel gas control plates 71.

[0040] The flapper 5 is, for example, a resin molded product and is positioned above the first blade portion 41a (downstream in the airflow direction) of the first flow path 3a. It is also pivotable in a direction opposite to the first main surface portion 42a of the first blade portion 41a so as to simultaneously open and close the first flow path 3a and the first fuel gas outlet 80a (see Figures 4 to 6). The opening of the flapper 5 changes according to the airflow rate, such that the opening is smaller when the airflow rate of the premixing flow path 3 is low than when it is high. When the airflow rate is low, the flapper 5 lies on its side due to its own weight and is in the closed state shown in Figure 4. As the airflow rate increases, the flapper 5 is lifted by the upward airflow and changes as shown in Figures 5 and 6, for example.

[0041] Preferably, the first fuel gas outlet 80a is provided near the outer end of the first blade portion 41a (the end opposite to the partition wall portion 40). With this configuration, the first fuel gas outlet 80a can be opened and closed by the region near the tip of the flapper 5 (the region far from the shaft 61, which is the pivot center of the flapper 5), and the sealing performance when the first fuel gas outlet 80a is closed can be improved.

[0042] In Figure 3, the pair of support members 60 are members that support the flapper 5 so that it can swing using the shaft 61, as previously described. The shaft 61 is inserted in a substantially horizontal direction through a hole 53 provided at one end of the flapper 5. Each support member 60 has, for example, a substantially L-shape when viewed from the side, and is equipped with a recess 60a into which the end of the shaft 61 can be fitted and held. The pair of support members 60 are attached to a pair of left and right protruding steps 43 provided on the inner surface of the peripheral wall of the first flow path 3a. As a means of attachment, for example, screw holes 43b that open in the upper surface 43a of each protruding step 43, and screw members 92 such as screws that are screwed into them are used. In this embodiment, the attachment of the support members 60 and the shaft 61 is completed within the premixing flow path 3. For this reason, it is not necessary to provide holes through the peripheral wall of the premixing flow path forming member 4, and it is not necessary to provide a separate sealing means to prevent the mixed gas from leaking to the outside from these holes.

[0043] The pair of protruding steps 43 are portions of the inner surface of the peripheral wall of the first flow path 3a that partially protrude closer to the center of the first flow path 3a than other general portions. In addition, the height of the upper surface 43a of each protruding step 43 is set to be higher than the height of the first main surface 42a. As shown in Figures 4 to 6, the flapper 5 is provided to swing through the region between the pair of protruding steps 43. In the state shown in Figure 5(a), the flapper 5 is half-open, and in this state, as shown in Figure 5(b), the pair of protruding steps 43 are located on both sides of the flapper 5. Therefore, air (and fuel gas) rising from below toward the flapper 5 is prevented from flowing upward through both sides of the flapper 5.

[0044] The flapper 5 has a pair of fin portions 55 integrally molded into it. However, it is not limited to this configuration, and a pair of fin portions 55 formed separately may be assembled to the flapper 5. As clearly shown in Figure 8, the pair of fin portions 55 protrude downward from the lower surface of the flapper 5, facing each other parallel to one another with a distance between them, and in a front view of the flapper 5... For example, it is a sector shape of a quarter circle. Here, the front view of the flapper 5 corresponds to Figure 8(b), which corresponds to the "view in the direction of the flapper's oscillation centerline" as referred to in this invention. The oscillation centerline is, for example, the line labeled CL in Figure 3, and the view in the direction of the oscillation centerline corresponds to the view in the direction of arrow D in Figure 3.

[0045] As shown in Figure 4, the pair of fin sections 55 are arranged to sandwich the first fuel gas outlet 80a and the first blade section 41a on both sides when the flapper 5 is in the closed state.

[0046] On the other hand, when the flapper 5 changes from a closed state to an open state, as shown in Figure 5, a gap 97 with a width L3 is formed between the pair of fin portions 55 and the first blade portion 41a, allowing air to pass through. In Figure 4, the gap 97 is also formed (however, in Figure 4, the flapper 5 is in the closed state, so air does not pass through the gap 97). As previously described, each fin portion 55 is a sector shape as a quarter circle when viewed from the front, and its tip portion 55a is an arc shape centered on the pivot center (shaft 61) of the flapper 5, but its radius R is set to be greater than or equal to the distance from the pivot center (shaft 61) to the first fuel gas outlet 80a (preferably the distance to the part of the first fuel gas outlet 80a furthest from the pivot center). With this configuration, as the flapper 5 changes from a closed state to an open state and its opening degree increases, it is possible to maintain the pair of fin portions 55 in an arrangement that sandwiches both sides of the first fuel gas outlet 80a and the first blade portion 41a for a relatively long period of time. Furthermore, it is possible to prevent the size of the fin portions 55 from becoming unnecessarily large.

[0047] When the flapper 5 is fully open, the protrusion 54 on the flapper 5 abuts against the partition wall 40, resulting in the angle shown in Figure 6. In contrast, when the flapper 5 is at that angle, each fin portion 55 is positioned above the first blade portion 41a and is not present on either side of the first blade portion 41a.

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

[0049] At the start of the driven combustion of burner 2 of combustion device B, and during the subsequent normal driven combustion, the driving speed of fan 1 is changed, and the flow rate of the air-fuel mixture supplied from premixing device A to burner 2 is changed, thereby controlling the driven combustion heat of burner 2. Here, when the fan 1 is driven at a low speed and the airflow rate in the premixing passage 3 is low, as shown in Figure 4, the flapper 5 is closed, and no air flows through the first passage 3a, while air flows only through the second passage 3b. Therefore, by increasing the speed of this airflow and applying a strong negative pressure to the second fuel gas outlet 80b, an appropriate amount of fuel gas corresponding to the airflow rate can be released into the second passage 3b. On the other hand, when the fan 1 is driven at a high speed, as shown in Figures 5 and 6, the flapper 5 is open, and air flows through both the first and second passages 3a and 3b, allowing an appropriate amount of fuel gas corresponding to the airflow rate to be released from both the first and second fuel gas outlets 80a and 80b. As a result, the turndown ratio can be increased.

[0050] The flapper 5 not only opens and closes the first flow path 3a, but also opens and closes the first fuel gas outlet 80a at the same time. Therefore, for example, when the first flow path 3a is closed, the first fuel gas outlet 80a is also closed at the same time, so that problems such as unnecessary leakage of fuel gas from the first fuel gas outlet 80a are appropriately prevented. As a means to achieve this, the first flow path 3a and the first fuel gas outlet 8 Since the two flappers for 0a are not used, the overall configuration of premixing unit A can be simplified, making it possible to reduce manufacturing costs.

[0051] When the airflow rate in the premixing passage 3 increases from below a predetermined level to above a predetermined level, as described above, the flapper 5 changes from the closed state shown in Figure 4 to the open state shown in Figure 5. At this stage, unlike in this embodiment, if, for example, the flapper 5 is not provided with a pair of fins 55, the effective flow area of ​​the premixing passage 3 changes abruptly (expands rapidly), causing the airflow velocity in the second passage 3b to drop sharply, and there is a risk that the mixture will abruptly change to a lean fuel mixture ratio. In contrast, according to this embodiment, when the flapper 5 is in the open state, a part of the first passage 3a is blocked by the pair of fins 55, so that the effect is substantially the same as suppressing abrupt changes in the effective flow area of ​​the premixing passage 3. As a result, the above-mentioned risk is eliminated, and it is possible to prevent the mixture ratio of the mixture from becoming an inappropriate lean fuel value.

[0052] The first and second fuel gas passages 8a and 8b are in communication with each other via the fuel gas receiving section 81. Therefore, normally, when the flapper 5 changes from a closed state to an open state, the air in the first passage 3a may flow back into the first and second fuel gas passages 8a and 8b from the first fuel gas outlet 80a due to the negative pressure generated in the second passage 3b. In contrast, according to this embodiment, the pair of fin sections 55 create resistance to such airflow. Therefore, the phenomenon of backflow is suppressed, and the mixture is more reliably prevented from becoming an inappropriate lean fuel mixture.

[0053] Furthermore, during the intermediate stages from when the flapper 5 begins to open until it is fully open, the flapper 5 will be at an angle as shown in Figure 5, for example. At this stage, a high-velocity airflow can be generated in the gap 97 between the pair of fin sections 55 and the first blade section 41a. This airflow occurs in the close-proximity areas on both sides of the first fuel gas outlet 80a. Therefore, a strong negative pressure is applied to the first fuel gas outlet 80a, ensuring a sufficient outflow rate of fuel gas into the first flow path 3a. Consequently, the mixture is less likely to have an inappropriate lean fuel mixture ratio.

[0054] On the other hand, when the flapper 5 is in the fully open state shown in Figure 6, the pair of fin sections 55 are spaced apart above the first blade section 41a. In this state, it is possible to suppress the air resistance of the pair of fin sections 55 and reduce pressure loss. When the flapper 5 is in the fully open state, the airflow velocity is sufficiently high, so unlike in the case shown in Figure 5, there is little or no need to use the fin sections 55 and the first blade section 41a to generate a higher-speed airflow.

[0055] Figures 9 and 10 show other embodiments of the present invention. In these figures, elements identical or similar to those in the above embodiments are denoted by the same reference numerals, and redundant explanations are omitted.

[0056] The pair of fin sections 55A shown in Figure 9 have a smaller vertical width L2 compared to that of the fin section 55 shown in Figure 8. With this configuration, when the flapper 5 changes from a closed state to an open state and the degree of opening increases, the fin sections 55A separate from both sides of the first blade section 41a at an earlier timing than the fin section 55 shown in Figure 8. This is more preferable in avoiding the fin sections 55A becoming air resistance and causing pressure loss.

[0057] In both Figure 8 and Figure 9, the entire tip portion 55a of each fin portion 55, 55A is arc-shaped with a predetermined radius R, but the present invention is not limited thereto. Fin portion in the present invention It is also possible to have a configuration in which only a portion of the tip near the flapper is shaped like a predetermined arc, while the tip of the rest of the fin is not shaped like an arc. Of course, the entire length of the tip of the fin can also be shaped not like an arc.

[0058] In the embodiment shown in Figure 10, the flapper 5 is approximately semicircular in plan view, and a bolt-shaped shaft 61A passes through a hole 53 at one end of the flapper 5. This shaft 61A is inserted into and supported by a pair of through holes 46 provided in the peripheral wall of the cylindrical portion 49 of the premixing channel forming member 4. The shaft 61A is fixed to the premixing channel forming member 4 by tightening a nut 62 screwed onto a threaded portion 610 provided at its tip, and the flapper 5 is pivotable around this shaft 61A. Although not shown in the diagram, a sealing member is provided at the insertion point of the shaft 61A into the through hole 46 to prevent the mixed gas from leaking out of the premixing channel forming member 4 to the outside.

[0059] In this embodiment as well, similar to the previous embodiment, it is possible to support the flapper 5 in a way that allows it to swing appropriately with a simple configuration. In addition, in the present invention, as a means of making the flapper oscillate, instead of using a separate metal or other shaft from the flapper, a means can be used in which a protrusion that serves as the pivot point of the flapper is provided on either the flapper or the flapper's support member, and a recess into which the protrusion is fitted is provided on the other.

[0060] The present invention is not limited to the embodiments described above. The specific configurations of each part of the premixing device and combustion device according to the present invention can be modified in various ways within the scope intended by the present invention.

[0061] The premixing channel is preferably venturi-shaped, but is not limited thereto. The specific shapes, sizes, and materials of the first and second blade sections, the flapper, the pair of fin sections, etc., are not limited to the embodiments described above. The first and second fuel gas outlets may be provided in multiples, rather than just one each.

[0062] The fuel gas may be natural gas or LPG, but the specific type is not limited. The combustion device according to the present invention is not limited to hot water systems, but can also be used for other purposes such as heating or incineration. Furthermore, it is not limited to a type that directs the combustion gas downwards, but can also be a type that directs the combustion gas upwards, for example. [Explanation of symbols]

[0063] A Premixer B Combustion device 1 fan 2 burners 3 Premixing channel 3a, 3b First and second channels 4. Premixing channel forming member 40 Partition wall section 41a, 41b First and second blade sections 43 Projecting step 5 Flappa 55, 55A Fin section 55a Tip 60 Support member 61. Axis (center of oscillation) 8a,8b First and second fuel gas flow paths 80a, 80b First and second fuel gas outlets 81 Fuel gas receiving section 97 gaps

Claims

1. A premixing channel is provided for supplying air from the outside and mixing this air with fuel gas to generate a fuel-air mixture. This premixing channel is divided into first and second channels arranged in a direction intersecting the airflow direction by a partition wall, First and second fuel gas outlets capable of discharging fuel gas into the first and second passages by utilizing the negative pressure generated by the airflow in the first and second passages, A premixing device equipped with, A first blade portion is provided within the first flow path, and the first fuel gas outlet is provided facing downstream in the direction of the airflow, A flapper is provided, which is located downstream of the first blade portion in the airflow direction of the first flow path, is pivotable to open and close both the first flow path and the first fuel gas outlet, and whose opening degree changes according to the airflow rate such that the opening degree is smaller when the airflow rate of the premixing flow path is low than when it is high. A pair of fin portions are provided on the flapper so as to sandwich the first fuel gas outlet and the first blade portion in a direction intersecting the airflow direction, and the fin portions form a gap between them that allows air to pass through. A premixing apparatus characterized by further comprising the following features.

2. A premixing apparatus according to claim 1, A premixing device in which, when viewed in the direction of the pivot center of the flapper, at least the region of each fin portion closer to the flapper has a tip that is arc-shaped with respect to the pivot center, and the radius thereof is greater than or equal to the distance from the pivot center to the first fuel gas outlet.

3. A premixing apparatus according to claim 1, A premixing device in which, when the flapper is fully open, each fin portion is located downstream of the first blade portion in the direction of airflow and is not present on either side of the first blade portion.

4. A premixing apparatus according to claim 1, A protruding step portion is provided on the inner surface of the peripheral wall of the first flow path and partially protrudes closer to the center of the first flow path than other general parts of the inner surface of the peripheral wall, A support member is attached to this protruding step and positioned within the first flow path, and supports the flapper so that it can swing; A premixing device that is further equipped with this feature.

5. A premixing apparatus according to claim 1, A premixing channel forming member that forms the premixing channel, A second blade is provided in the second flow path such that one end is connected to the peripheral wall of the premixing flow path forming member and the other end is connected to the first blade via the partition wall, and the second fuel gas outlet is provided facing downstream in the direction of airflow, A fuel gas receiving portion is provided on the peripheral wall portion of the premixing channel forming member and receives fuel gas from the outside, A second fuel gas passage is provided within the second blade portion so that a portion of the fuel gas supplied to this fuel gas receiving portion can be guided to the second fuel gas outlet, A first fuel gas passage is provided extending from within the second blade portion into the first blade portion so that it can guide another portion of the fuel gas supplied to the fuel gas receiving portion to the first fuel gas outlet, A premixing device that is further equipped with this feature.

6. A premixing apparatus according to claim 5, A premixing device wherein the second blade portion has a greater thickness in the airflow direction than the first blade portion, and within the second blade portion, the first and second fuel gas passages are arranged to overlap in the airflow direction.

7. Fans, A premixing device is provided on the intake side of this fan and generates a mixture of air and fuel gas, which is then sent to the fan. A burner that receives the air-fuel mixture from the fan and burns the fuel gas, A combustion device equipped with, A combustion apparatus characterized in that the premixing device described in any one of claims 1 to 6 is used as the premixing device.

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