PREMIXING DEVICE AND COMBUSTION DEVICE INCLUDING THE SAME

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Japan application serial no. 2024-006704, filed on Jan. 19, 2024. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

BACKGROUND
Technical Field

The invention relates to a premixing device and a combustion device including the same. Here, “premixing” refers to a process of mixing air and a fuel gas in advance to generate a combustible gas mixture for the purpose of performing premixing combustion.

Description of Related Art

Patent Document 1 discloses as a specific example of a premixing device. The premixing device described in the same document includes a venturi-shaped premixing flow path that has an end open to the exterior and the other end side connected to the intake side of a fan, and when the fan is driven, external air flows in from the opening on the end side and flows in a predetermined direction. The premixing flow path is divided into first and second flow paths by a partition wall part, and first and second fuel gas outlets are provided on the inner peripheral wall surfaces of the first and second flow paths, respectively. In addition, a flapper that can swing to open and close the first flow path is provided in the first flow path. The flapper changes the opening degree in accordance with the air flow rate so that in the case where the air flow rate in the first flow path is low, the opening degree becomes smaller than the case where the air flow rate is high.

In such a premixing device, air flows through the premixing flow path, and a negative pressure acts on the first and second fuel gas outlets, causing fuel gas to flow out from the first and second fuel gas outlets into the premixing flow path. The fuel gas is mixed with the air, and a gas mixture is generated. Meanwhile, when the air flow rate is low, the flapper closes the first flow path of the premixing flow path. As a result, the air flow velocity in the second flow path increases, and the negative pressure acting on the second fuel gas outlet is strengthened. Consequently, even in the case where the air flow rate is low, an appropriate amount of fuel gas can be discharged from the second fuel gas outlet because of the negative pressure. Such effect is effective in increasing the turndown ratio.

However, in the conventional technology, there is still room for improvement as described below.

That is, at the time when the flapper changes from the closed state to the open state, the effective flow path area of the premixing flow path changes suddenly. Due to such influence, on the second flow path, the flow rate of the air flow generated previously decreases suddenly. As a result, the mixing ratio (air-fuel ratio) of the gas mixture also changes suddenly, and the gas mixture may become an inappropriate fuel-lean mixing ratio.

In addition, the flapper merely opens and closes the first flow path, while the first fuel gas outlet remains open. Therefore, for example, even if the first flow path is switched from an open state to a closed state by the flapper, there is a risk that the fuel gas may continue to flow out from the first fuel gas outlet for a certain period afterward. Furthermore, due to the pressure fluctuations in the first flow path caused by the influence of the air flow in the second flow path, there is also a risk that air from the first flow path may flow into (flow reversely into) a first fuel gas outlet, or that fuel gas may unnecessarily flow out from the first fuel gas outlet. This makes it difficult to maintain the gas mixture at the desired appropriate mixing ratio. As a means to resolve the issue, there is a method of further providing an additional flapper to open and close the first fuel gas outlet (see Patent Document 2). However, with such a method, since two flappers are used, one for the first flow path and one for the first fuel gas outlet, the total number of parts increases, and the manufacturing cost increases.

Moreover, in the conventional art (Patent Documents 1 as well as 2), when the flapper is changed from the closed state to the open state (when the flapper is at a small opening degree), the air flow rate of the first flow path is relatively low, and the air flow of the first flow path is at a low speed. Therefore, at this time, it is difficult to apply a strong negative pressure at the first fuel gas outlet, the amount of fuel gas outflow from the first fuel gas outlet may become insufficient, and the mixing ratio may become inappropriate.

Prior Art Document(s)

- [Patent Document 1] Japanese Patent Application Laid-open No. 2021-99204
- [Patent Document 2] U.S. Pat. No. 9,677,759
- [Patent Document 3] Japanese Patent No. 5948440
- [Patent Document 4] Japanese Patent No. 7303100
- [Patent Document 5] Japanese Patent No. 6738493

The invention provides a premixing device and a combustion device including the same, which exhibit excellent performance of being able to maintain a high turndown ratio and maintain a gas mixture at a suitable mixing ratio through simple means.

SUMMARY

A premixing device provided according to a first aspect of the invention includes: a premixing flow path, supplied with air from outside and provided for mixing a fuel gas with the air to generate a gas mixture; a partition wall part, partitioning the premixing flow path into a first flow path and a second flow path in parallel arrangement; and a first fuel gas outlet and a second fuel gas outlet, through which the fuel gas is able to flow out to the first flow path and the second flow path by using a negative pressure generated due to air flows in the first flow path and the second flow path. X and y directions intersecting each other are provided as directions intersecting an air flow direction in the first and second flow paths, and the premixing device includes: a blade part, provided on the first flow path, wherein the first fuel gas outlet is provided toward a downstream side of the air flow direction; a specific flow path region, as a portion of the first flow path and disposed in adjacency with a single side or both sides of the blade part in the x direction; a flapper, provided, in the first flow path, at a position downstream of the blade part and the specific flow path region; and a seat part, provided for the flapper, and including a periphery part of the first fuel gas outlet and an opening periphery part on a downstream side of the specific flow path region in the air flow direction. A proximal end of the flapper is supported by a support art to swing with the support part as a center, and, the flapper is settable to a closed state opposite to and in contact with the seat part in a configuration where the proximal end and a distal end are arranged in the y direction, so as to be able to open and close the first fuel gas outlet and the specific flow path region in accordance with an air flow rate of the premixing flow path. The premixing device is configured that, when the flapper is changed from the closed state to an open state, auxiliary flow paths on a proximal end side and a distal end side are formed between respective regions on the proximal end side and the distal end side of the flapper and the seat part, and through the auxiliary flow paths, an air flow from the specific flow path region toward a region downstream of the flapper in the air flow direction and a fuel gas outflow from the first fuel gas outlet, which accompanies the air flow, are generated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing an example of a combustion device including a premixing device according to the invention.

FIG. 2 is a perspective view illustrating the appearance of the premixing device of FIG. 1.

FIG. 3 is an exploded perspective view of FIG. 2.

FIG. 4A is a front cross-sectional view of the premixing device shown in FIG. 1, FIG. 4B is a cross-sectional view of the premixing device at a different location from FIG. 4A, and FIG. 4C is a cross-sectional view of main components (cross-sectional view of main components on a right side surface) taken along a line IVc-IVc of FIG. 4B.

FIG. 5A is a front cross-sectional view showing the case where a flapper of the premixing device shown in FIG. 4A is in a fully open state, FIG. 5B is a cross-sectional view of the premixing device at a different location from FIG. 5A, and FIG. 5C is a cross-sectional view of main components (cross-sectional view of main components on the right side surface) taken along a line Vc-Vc of FIG. 5B.

FIG. 6A is a front cross-sectional view showing the case where a flapper of the premixing device shown in FIG. 4A is in a fully open state, FIG. 6B is a cross-sectional view of the premixing device at a different location from FIG. 6A, and FIG. 6C is a cross-sectional view of main components (cross-sectional view of main components on the right side surface) taken along a line VIc-VIc of FIG. 6B.

FIG. 7A is a plan view of a premixing flow path forming member of the premixing device shown in FIG. 2 and FIG. 3, FIG. 7B is an enlarged view of main components, and FIG. 7C is a plan cross-sectional view of FIG. 7A.

FIG. 8A is a perspective view of the flapper of the premixing device shown in FIG. 1 and FIG. 2, FIG. 8B is a front view thereof, and FIG. 8C is a right side view thereof.

FIG. 9A is an explanatory diagram of an effect of the flapper shown in FIGS. 8A to 8C, FIG. 9B is an explanatory diagram showing Comparative Example 1 (not corresponding to an embodiment of the invention) in comparison with FIG. 9A.

FIG. 10A is another explanatory diagram of an effect of the flapper shown in FIG. 8, and FIG. 10B is an explanatory diagram showing Comparative Example 2 (corresponding to an embodiment of the invention) in comparison with FIG. 10A.

FIG. 11 is a cross-sectional view of main components illustrating another example of the invention.

FIG. 12 is a perspective view illustrating another example of the invention.

DESCRIPTION OF THE EMBODIMENTS

According to the configuration, in the case where the flow rate of the air supplied to the premixing flow path is low, the first flow path (specific flow path region) is in the closed state by the flapper, and the fuel gas flowing out from the second fuel gas outlet is mixed with the air flowing through the second flow path. Meanwhile, in the case where the air flow rate is high, the air also flows on the first flow path, the fuel gas flowing out from the first fuel gas outlet is mixed with the air. Therefore, like Patent Document 1, it is possible to increase the turndown ratio. In addition, according to the invention, effects as follows are obtained. Firstly, in addition to opening and closing the first flow path (specific flow path region), the flapper is also able to open and close the first fuel gas outlet. Therefore, when the first flow path is in the closed state, the first fuel gas outlet is simultaneously in the closed state. The issue that the fuel gas unnecessarily flows out from the first fuel gas outlet afterwards can be appropriately prevented. As a means for such purpose, it is not necessary to use a total of two flappers for the first flow path and the first fuel gas outlet. Therefore, it is possible to simplify the overall configuration and reduce the manufacturing cost.

Second, when the flapper is changed from the closed state to the open state (when the opening degree of the flapper is a small opening degree equal to or less than a predetermined level), through the auxiliary flow paths on the proximal end side and the distal end side formed between the respective regions of the proximal end side and the distal end side of the flapper and the seat part, it is possible to generate an air flow from the specific flow path region of the first flow path toward the region downstream of the flapper in the gas flow region. Additionally, accompanying with this, the negative pressure due to the air flow acts on the first fuel gas outlet, and a fuel gas outflow can be also generated. Therefore, it is possible to sufficiently secure the outflow amount of the fuel gas to the first flow path. In addition, when the flapper is changed from the closed state to the open state, the issue that the air flowing through the first flow path flows into the first fuel gas outlet and reversely flows to the side of the second flow path is also suppressed. In this way, according to the invention, when the flapper is changed from the closed state to the open state, the gas mixture is prevented from having an inappropriate fuel-lean mixture ratio, and the performance of maintaining the gas mixture at an appropriate mixture ratio can be excellent.

In the invention, it may also be that, when the flapper is in the closed state, the first fuel gas outlet is arranged in a fully closed state by using the flapper, while the specific flow path region is arranged in a non-fully closed state in which a portion located close to the proximal end of the flapper is in the open state, and it is configured that, the air flow from the specific flow path region toward the region downstream of the flapper in the air flow direction is able to be generated through a portion of the open state.

According to the configuration, even when the flapper is in the closed state, and the outflow of the fuel gas from the first fuel gas outlet is prevented, the specific flow path region is not fully closed, a portion of the flapper close to the proximal end is in the open state, and the air flow can be generated in the vicinity of the proximal end of the flapper. Therefore, immediately after the flapper is changed from the closed state to the open state, even when the opening degree of the flapper is quite small, a large amount of air flow can be generated in the auxiliary flow passage on the proximal end side. This helps promote fuel gas outflow from the first fuel gas outlet.

In the invention, it may also be that the flapper includes a flapper body part and a connection part, the flapper body part has a plate shape and is opposite to and in contact with the seat part when the flapper is in the closed state, and the connection part is connected with the flapper body part and at least a portion of the connection part is included in the proximal end, and the support part is a portion that supports the connection part to be able to swing around a center line extending in the x direction, and is located on a downstream side with respect to the flapper body part in the air flow direction and on a side of the partition wall part when the flapper is in the closed state.

According to the configuration, the flapper body art swings around the center line of the support part that extends in the x-direction, while the support part is located downstream of the flapper body part in the air flow direction and on the side of the partition wall part when the flapper is in a closed state. Therefore, when the flapper is changed from the closed state to the open state, the entire region from the proximal end side of the flapper body part to the distal end (the area having a width in the y direction) can be immediately separated from the seat part, and a gap is accurately generated therebetween. As a result, such gap corresponds to the auxiliary flow paths on the proximal end side and the distal end side, and the intended function of the invention can be appropriately obtained.

In the invention, it may also be that the connection part is configured to be spaced apart from the seat part when the flapper is in the closed state, so that a first gap is formed between the connection part and the seat part, and the connection part is configured so that, when the flapper is changed from the closed state to the open state, the first gap forms the auxiliary flow path on the proximal end side.

According to the configuration, the auxiliary flow path on the proximal end side, which is formed when the flapper is changed from the closed state to the open state is formed by using the first gap. Therefore, the size of the entirety of the auxiliary flow path on the proximal end side can be reliably and easily achieved.

In the invention, it may also be that, the connection part of the flapper has an inclined surface part inclined so that, in a region facing the seat part when the flapper is in the closed state, the closer from a side of the flapper body part toward a side of the support part, the greater a separation distance with respect to the seat part.

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

In the invention, it may also be that, a second gap is formed between the connection part and the partition wall part for communication of the first gap with the region downstream of the flapper in the air flow direction when the flapper is in the closed state and when the flapper is changed from the closed state to the open state.

With such configuration, when the flapper is changed from the closed state to the open state, the air can smoothly flow to the region downstream of the flapper in the air flow direction from the specific flow path region through the first gap and the second gap. Therefore, by using the air flow, the fuel gas outflow from the first fuel gas outlet can be appropriately facilitated.

In the invention, it may also be that a hole part or a notch part is provided on the proximal end part of the flapper for communication of the first gap with the region of the first flow path downstream of the flapper in the air flow direction when the flapper is in the closed state and when the flapper is changed from the closed state to the open state.

With such configuration when the flapper is changed from the closed state to the open state, the air travels through the hole part or the notch part of the flapper from the first gap, and smoothly flows to the region downstream of the flapper in the air flow direction. Therefore, the fuel gas outflow from the first fuel gas outlet can be appropriately facilitated.

A combustion device provided according to a second aspect of the invention includes: a premixing device, generating a gas mixture mixing air and a fuel gas; and a burner part, receiving supply of the gas mixture from the premixing device to cause combustion of the fuel gas. The premixing device provided by the first aspect of the invention is used as the premixing device.

According to such configuration, the same effects are obtained as described for the premixing device provided by the first aspect of the invention.

The following describes exemplary embodiments of the invention with reference to the drawings.

FIG. 1 shows a hot water apparatus WH. The hot water apparatus WH is a hot water supply apparatus, and includes a premixing device A, a combustion device B (premixing combustion device), and a heat exchanger 11. The combustion device B is configured by combining a fan 1 and a burner part 2 in the premixing device A. The fan 1 is variable in speed (variable in air flow rate).

The details of the premixing device A will be described later. However, a gas mixture (combustible gas mixture) of air and a fuel gas is generated by using the premixing device A, and the gas mixture is supplied to the burner part 2 via the fan 1. The burner part 2 includes a porous plate 21 having multiple air holes 20 (flame holes) and is accommodated in a case 10. The burner part 2 is provided with accessories such as an ignition plug and a flame detection sensor, which are not shown. The gas mixture passes through the air holes 20 and causes combustion below the porous plate 21. The combustion gas generated by the burner part 2 acts on the heat exchanger 11, and the water passing through the heat exchanger 11 is heated. As a result, hot water is generated, and the hot water is supplied to the desired hot water supply destination.

As well shown in FIG. 2 to FIG. 6C, the premixing device A includes a device body part A0 and a flapper 5 assembled to the device body part A0. In the figures, x and y directions intersect each other, and also intersect with the air flow direction in the premixing flow path 3 to be described afterwards. In the embodiment, the air flow direction in the premixing flow path 3 is an upper-lower height direction of the premixing device A.

The device body part A0 includes a premixing flow path forming member 4 and a pipe joint part 70.

The premixing flow path forming member 4 includes a tubular part 49, a flange part 48, and a base part 44. A venturi-shaped premixing flow path 3 is formed inside the tubular part 49. The flange part 48 is connected to the upper end of the tubular part 49. The stepped base part 44 protrudes on the outer surface part of the tubular part 49. The pipe joint part 70 is attached to the base part 44 by using a screw member 90, such as a screw, by sandwiching a fuel gas control plate 71 to be described later.

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

As well shown in FIG. 4B, FIG. 5B, and FIG. 6B, a partition wall part 40 extending in the upper-lower height direction, which is the air flow direction, is provided in the premixing flow path 3. As a result, a portion of the premixing flow path 3 is divided into first and second flow paths 3a, 3b arranged in the y direction by sandwiching the partition wall part 40. The partition wall part 40 is disposed to be offset from the center of the tubular part 49 in the y direction, and the first flow path 3a has a flow path area larger than that of the second flow path 3b. However, differing from the above, the first and second flow paths 3a, 3b may have the same flow path area.

As well shown in FIG. 4A to FIG. 7C, first and second blade parts 41a, 41b (shown as dotted pattern portions in FIGS. 7A and 7C) are provided in the first and second flow paths 3a, 3b. On the upper surface parts, which are the main surface parts facing the downstream side in the air flow direction, of the first and second blade parts 41a, 41b, first and second fuel gas outlets 80a, 80b are provided as upward-facing openings. The first blade part 41a corresponds to an example of the blade part of the invention.

The first and second blade parts 41a, 41b extend in the y direction to traversely cross the first and second flow paths 3a, 3b in the horizontal direction, respectively. An end of each of the first and second blade parts 41a, 41b is connected to a peripheral wall inner surface part of the premixing flow path 3 (the inner surface part of the peripheral wall part of the tubular part 49), and the other ends of the first and second blade parts 41a, 41b are connected to each other by sandwiching the partition wall part 40.

As well shown in FIGS. 7A to 7C, the first blade part 41a divides a portion of the first flow path 3a into a pair of specific flow path regions (divided flow paths) 3a′ through which air is able to flow. Accordingly, in the x direction, the pair of specific flow path regions 3a′ are located on both sides of the first blade part 41a.

Meanwhile, the second blade part 41b divides a portion of the second flow path 3b into a pair of divided flow paths 3b′ through which air is able to flow. Accordingly, in the x direction, the pair of divided flow paths 3b′ are located on both sides of the second blade part 41b.

As shown in FIG. 4A, FIG. 5A, and FIG. 6A, the pipe joint part 70 internally forms a fuel gas receiving part 81 for receiving fuel gas supplied from the outside. The fuel gas supplied to the fuel gas receiving part 81 is guided to the first and second fuel gas outlets 80a, 80b through the openings 71a, 71b of the fuel gas control plate 71 and first and second fuel gas flow paths 8a, 8b.

While the second fuel gas flow path 8b is provided inside the second blade part 41b and the seat part 44, the first fuel gas flow path 8a is provided inside the first and second blade parts 41a, 41b and the seat part 44. The second blade part 41b is made thicker in the upper-lower direction than the first blade part 41a, and, within the second blade part 41b, the first and second fuel gas flow paths 8a, 8b overlap in the upper-lower height direction. With such configuration, it is possible to simplify the fuel gas supply structure to the first and second fuel gas outlets 80a, 80b. In addition, by overlapping the first and second fuel gas flow paths 8a, 8b in the upper-lower height direction, it becomes possible to prevent the width of the second blade part 41b in the horizontal direction (x direction) from becoming excessively large, and to sufficiently secure the opening area of the pair of divided flow paths 3b′.

As described above, the fuel gas control plate 71 is attached to the seat part 44 and has two openings 71a, 71b facing distal end openings of the first and second fuel gas flow paths 8a, 8b. By adjusting the opening areas of the openings 71a, 71b, it is possible to control the fuel gas inflow amount from the fuel gas receiving part 81 into the first and second fuel gas flow paths 8a, 8b.

In the lower and upper parts inside the tubular part 49, an air inlet part 3c and an air outlet part 3d are formed. The air inlet part 3d and the air outlet part 3d are in communication with the first and second flow paths 3a, 3b. When the fan 1 is driven, the air from the outside can flow into the air inlet part 3c and then be branched and flow into the first and second flow paths 3a, 3b. Due to the negative pressure effect generated by the air flow in the first and second flow paths 3a, 3b, as described earlier, fuel gas flows out from the first and second fuel gas outlets 80a, 80b, and a gas mixture of air and fuel gas is generated. The gas mixture flows out from the air outlet part 3d to the outside of the tubular part 49.

As shown in FIG. 4A to FIG. 6C, the flapper 5 is capable of simultaneously opening and closing the first flow path 3a (a pair of specific flow path regions 3a′) and the first fuel gas outlet 80a. More specifically, the flapper 5 has a configuration as follows.

That is, the flapper 5 is, for example, a resin molded product. As well shown in FIGS. 8A to 8C, the flapper 5 includes a plate-shaped flapper body part 50, a protruding step-shaped connection part 51 connected to a portion of the flapper body part 50, and a pair of fin parts 55 protruding downward from the flapper body part 50. A proximal end 5a of the flapper 5 is a portion including the connection part 51.

A support part 52 is provided at the connection part 51 of the flapper 5. The support part 52 is a portion that supports the connection part 51 to be able to swing around a center line CL extending in the x direction. A shaft body 61 serving as the swing fulcrum of the flapper 5 is provided to penetrate the connection part 51. As well shown in FIG. 3, the shaft body 61 is a part supported by a pair of auxiliary members 60 having support holes 60a. The pair of auxiliary members 60 are attached to a step part 43 provided separately in the first flow path 3a by using screw members 92, etc.

In the first flow path 3a, the flapper 5 is provided on the upper side of the first plate part 41a (downstream side in the air flow direction), and is able to swing in the upper-lower height direction with the support part 52 (more specifically the central line CL) as the center. This enables simultaneous opening and closing of the pair of specific flow path regions 3a′ of the first flow path 3a and the first fuel gas outlet 80a (refer to FIG. 4A to FIG. 6C).

The swinging of the flapper 5 is performed by using the self-weight of the flapper 5 as a downward force and the upward air flow through each specific flow path region 3a′ as an upward force. The opening degree of the flapper 5 changes according to the air flow rate, so that the opening degree decreases in the case where the air flow rate in the premixing flow path 3 is low, as compared to the case where the air flow rate is high. In the case where the air flow rate is low, the flapper 5 lies down horizontally due to the self-weight. As a result, the flapper is in the closed state (fully closed state) shown in FIGS. 4A to 4C. As the air flow rate increases, the flapper 5 is lifted by the upward air flow, and is changed to, for example, the open state (fully open state) shown in FIGS. 5A to 5C. FIGS. 6A to 6C show the state (small opening degree state where the opening degree is equal to or lower than a predetermined level) when the flapper 5 changes from the closed state to the open state.

At the time of being in the fully open state as shown in FIGS. 5A to 5C, the flapper 5 is set to assume a posture upright in the upper-lower height direction. In the fully open state, the center of gravity of the flapper 5 is located closer to the center of the first flow path 3a than the position directly above the swing center (center line CL) of the flapper 5, a rotational moment is generated to lower the flapper 5. Therefore, when the air flow rate in the first flow path 3a decreases, the flapper 5 correspondingly lowers, and the opening degree decreases.

The closed state of the flapper 5 is a state where the flapper body part 50 is opposite to and in contact with the seat part 47, as shown in FIGS. 4A to 4C. Here, the seat part 47 is a portion with an upward-facing surface of the first blade part 41a, including the periphery part of the first fuel gas outlet 80a and the upper opening periphery part (opening periphery part on the downstream side in the air flow direction) of each specific flow path region 3a′.

In the closed state of the flapper 5, as shown in FIG. 4A, the first fuel gas outlet 80a is configured to be in a fully closed state using the flapper 5. Comparatively, as shown in FIG. 4B, the specific flow path region 3a′ is not in the fully closed state using the flapper 5. Instead, a portion 3a″ close to the proximal end 5a of the flapper 5 among each specific flow path region 3a′ is configured to be in an open state. In the closed state of the flapper 5, it is possible to generate an air flow from each specific flow path region 3a′ to the region downstream of the flapper 5 in the air flow direction via the portion 3a″.

The support part 52 is disposed to be offset toward the side of the partition wall part 40 and downstream in the air flow direction from the flapper body part 50 and the first fuel gas outlet 80a when the flapper 5 is in the closed state.

The connection part 51 of the flapper 5 is disposed to be spaced above the seat part 47 when the flapper 5 is in the closed state, and a first gap C1 is formed between the connection part 51 and the seat part 47. Additionally, in the downward-facing region of the connection part 51 that faces the seat part 47, an inclined surface part 51a is formed. The inclined surface part 51a is inclined, so that, the closer from the side of the flapper body part 50 toward the side of the support part 52, the greater a separation distance La (see FIG. 8B) with respect to the seat part 47 becomes. A second gap C2 in communication with the first gap C1 is formed between the connection part 51 and the partition wall part 40.

The flapper 5 is configured so that, at the time of changing from the closed state shown in FIGS. 4A to 4C to the open state (small opening degree state) shown in FIGS. 6A to 6C, auxiliary flow paths 38a and 38b on the proximal end side and the distal end side are formed between the respective regions on side of the proximal end 5a and side of the distal end 5b of the flapper and the seat part 47. Accordingly, an air flow is generated from each specific flow path region 3a′ to the region downstream of the flapper 5 in the air flow direction via the auxiliary flow paths 38a and 38b on the proximal end side to the distal end side. In addition, due to the suction negative pressure effect caused by the air flow, the fuel gas outflow from the first fuel gas outlet 80a is generated.

More specifically, in the small opening degree state of the flapper 5, the fuel gas and the air (gas mixture) that have advanced to the auxiliary flow path 38b on the distal end side flow to the region downstream of the flapper 5 in the air flow direction through a third gap C3 between the distal end 5b of the flapper 5 and the inner wall part of the first flow path 3a.

Meanwhile, the fuel gas and air (gas mixture) that have advanced into the auxiliary flow path 38a on the proximal side flow to the region downstream of the flapper 5 in the air flow direction through the second gap C2. The auxiliary flow path 38a on the proximal side is formed to include the first gap C1.

The pair of fin parts 55 of the flapper 5 protrude downward from the lower surface part of the flapper 5 in a parallel, facing arrangement with a space therebetween (see also to FIGS. 8A to 8C). As shown in FIGS. 4A to 4C and FIGS. 6A to 6C, the pair of fin parts 55 are disposed to sandwich the left and right sides of the first fuel gas outlet 80a and the first blade part 41a at the time when the flapper 5 is in the closed state and when the flapper 5 changes from the closed state to the open state. As will be described later, the pair of fin parts 55 serve to suppress the phenomenon that the air of the first flow path 3a flows reversely in the first and second fuel gas flow paths 8a, 8b from the first fuel gas outlet 80a due to the negative pressure that occurs in the second flow path 3b when the flapper 5 changes from the closed state to the open state.

Then, the operation of the premixing device A and the combustion device B including the premixing device A will be described.

When the burner part 2 of the combustion device B is driven and performs combustion, the control of the driving combustion power of the burner part 2 is executed by changing the driving speed of the fan 1 and the flow rate of the gas mixture supplied from the premixing device A to the burner part 2.

Here, in the case where the driving speed of the fan 1 is low and the air flow rate in the premixing flow path 3 is low, as shown in FIGS. 4A to 4C, the flapper 5 is in the closed state, and each specific flow path region 3a′ of the first flow path 3a is blocked except for the portion 3a″, and air flows into the second flow path 3b. Therefore, the air flow in the second flow path 3b can be accelerated, a strong negative pressure acts on the second fuel gas outlet 80b, and an appropriate amount of fuel gas corresponding to the air flow rate can be discharged to the second flow path 3b. Meanwhile, when the driving speed of the fan 1 is high, for example, as shown in FIGS. 5A to 5C, the flapper 5 is in the open state, air flows sufficiently into both the first and second flow paths 3a, 3b, and an appropriate amount of fuel gas corresponding to the air flow rate can be discharged from both the first and second fuel gas outlets 80a, 80b. As a result, the turndown ratio can be increased.

The flapper 5 not only opens and closes the first flow path 3a but also simultaneously opens and closes the first fuel gas outlet 80a. Therefore, for example, when the first flow path 3a is in the closed state, the first fuel gas outlet 80a is simultaneously in the closed state. Therefore, the issue that a fuel gas flow unnecessarily flows out from the first fuel gas outlet 80a afterwards can be appropriately prevented. As a means for such purpose, two flappers for the first flow path 3a and the first fuel gas outlet 80a are not used, so it is possible to simplify the overall structure of the premixing device A and reduce manufacturing costs.

At the time when the air flow rate of the premixing flow path 3 increases from a state below a predetermined level to a state equal to or over the predetermined level, as previously described, the flapper 5 changes from the closed state shown in FIGS. 4A to 4C to the open state (small opening degree state) shown in FIGS. 6A to 6C. At this time, in the embodiment, the auxiliary flow paths 38a and 38b on the proximal side and the distal side are formed in communication with the second gap C2 and the third gap C3 between the respective regions on the side of the proximal end 5a and the side of the distal end 5b of the flapper 5 and the seat part 47. Therefore, a smooth air flow is generated through these portions from each specific flow path region 3a′ of the first flow path 3a toward the region downstream of the flapper 5 in the air flow direction. Additionally, accompanying with this, the negative pressure due to the air flow acts on the first fuel gas outlet 80a, a fuel gas outflow can be generated. Therefore, immediately after the flapper 5 changes from the closed state to the open state, it is possible to sufficiently secure the amount of fuel gas outflow to the first flow path 3a and suppress the gas mixture from becoming an inappropriate fuel-lean mixing ratio. As a result, it is possible to achieve excellent performance in maintaining a constant mixing ratio.

In particular, in the embodiment, even when the flapper 5 is in the closed state as shown in FIGS. 4A to 4C, each specific flow path region 3a′ is not fully closed. Instead, the portion 3a″ close to the proximal end 5a of the flapper 5 remains in the open state, and an air flow occurs in such portion. As a result, even immediately after the flapper 5 changes to the open state, it is possible to sufficiently secure the air flow rate in the auxiliary flow path 38a on the proximal end side of the flapper 5, which is preferable in terms of facilitating the fuel gas outflow from the first fuel gas outlet 80a.

When the flapper 5 changes from the closed state to the open state, as shown in FIGS. 6A to 6C, the flapper 5 assumes a posture inclined so that the side of the distal end 5b of the flapper 5 is more separated from the seat part 47 than the side of the proximal end 5a. Originally, the auxiliary flow path 38a on the proximal end side would become a flow path narrower than the auxiliary flow path 38b on the distal end side, and the air flow rate in the auxiliary flow path 38a on the proximal end side would decrease.

Comparatively, according to the configuration of the embodiment, this issue is alleviated.

In the embodiment, when the flapper 5 is in the closed state, the first gap C1 is formed between the connection part 51 of the flapper 5 and the seat part 47. As clearly shown in FIG. 9A, when the flapper 5 changes to the open state, the first gap C1 is included in the auxiliary flow path 38a on the proximal end side, and the auxiliary flow path 38a is formed. Therefore, the overall size of the auxiliary flow path 38a on the proximal end side is increased, and the air flow rate in such portion can be easily secured.

In addition, in the embodiment, a distance Lb from the swing center of the flapper 5 to a proximal end 50a of the flapper body part 50 is set to be relatively long. Therefore, when the flapper 5 changes to the open state, it becomes possible to increase a dimension Le between the proximal end 50a of the flapper body part 50 and the seat part 47 (see to the right part in FIG. 9A).

FIG. 9B shows Comparative Example 1 with respect to the embodiment. In Comparative Example 1, as shown in the left part of the same figure, when a flapper 5E is in the closed state, a portion corresponding to the first gap C1 of the embodiment is not formed. Furthermore, as shown in the right part of the same figure, when the flapper 5E changes to the open state, the lower surface of the proximal end of the flapper 5E comes into contact with the seat part 47, and a portion corresponding to the auxiliary flow path 38a on the proximal end side of the embodiment is not formed. With such a configuration, it is difficult to appropriately discharge fuel gas from the first fuel gas outlet 80a. Comparatively, the embodiment appropriately resolves such issue.

In the embodiment, as shown in the right part of FIG. 10A, when the flapper 5 is at a relatively large opening degree, a portion of the air advancing from below collides with the connection part 51. Comparatively, an inclined surface part 51a is formed on the connection part 51, and it is possible to smoothly guide the air that collides with the inclined surface part 51a to advance obliquely upward.

FIG. 10B shows Comparative Example 2 with respect to the embodiment. In Comparative Example 2, a portion corresponding to the inclined surface part 51a of the embodiment of the invention is not provided in the flapper 5F. In Comparative Example 2, as shown in the right part of the same figure, when air collides with the proximal end of the flapper 5F, the air becomes a turbulent flow that reflects in various directions. Thus, the smooth outflow of the fuel gas is obstructed. Comparatively, the embodiment appropriately resolves such issue.

The first and second fuel gas flow paths 8a, 8b are in communication with each other through the fuel gas receiving part 81. Therefore, originally, when the flapper 5 changes from the closed state to the open state, there is a risk that the air of each specific flow path region 3a′ of the first flow path 3a may flow reversely into the first and second fuel gas flow paths 8a, 8b from the first fuel gas outlet 80a due to the negative pressure generated in the second flow path 3b. Comparatively, according to the embodiment, as described earlier, by forming the auxiliary flow paths 38a, 38b on the proximal end side and the distal end side, the air flow to the region downstream of the flapper 5 in the air flow direction is facilitated, and the reverse flow of air is appropriately suppressed. Furthermore, in the embodiment, the pair of fin parts 55 act as resistance against the reverse flow, and the reverse flow phenomenon is further suppressed.

FIGS. 11 and 12 illustrate other embodiments of the invention. In the drawings, elements that are the same as or similar to those in the above embodiment are assigned the same reference numerals as those in the above embodiment, and repeated descriptions will be omitted.

In the embodiment shown in FIG. 11, a hole part 56a is provided at the proximal end 5a of the flapper 5. The hole part 56a is a portion that allows communication of the first gap CI with a region of the first flow path 3a downstream of the flapper 5 in the air flow direction when the flapper 5 is in the closed state and when the flapper 5 is changed from the closed state to the open state.

In the embodiment shown in FIG. 12, in place of the hole part 56a of FIG. 11, a notch part 56b is provided at the proximal end 5a of the flapper 5.

In either of the embodiments shown in FIGS. 11 and 12 as well, when the flapper 5 is changed from the closed state to the open state, air can smoothly flow from the first gap C1 of each specific flow path region 3a′ of the first flow path 3a to the region downstream of the flapper 5 in the air flow direction via the hole part 56a or the notch part 56b of the flapper. Therefore, the fuel gas outflow from the first fuel gas outlet 80a can be appropriately facilitated. The configuration of the embodiment is particularly suitable for the case where, for example, the width of the second gap C2 cannot be made large and the flow rate of the air in the second gap C2 tends to be insufficient.

The invention is not limited to the contents of the above embodiment. The specific configuration of each part of the premixing device and combustion device related to the invention can be freely modified in design within the intended scope of the invention.

The premixing flow path is preferably venturi-shaped, but is not limited thereto. The specific shapes, sizes, and materials of the first and second blade parts, flapper, and other components are not limited to the embodiment described above. One or more of each of the first and second fuel gas outlets may be provided, for example.

The specific flow path region is not limited to the configuration where a pair thereof are provided on both sides of the first blade part in the x direction, but can also be configured as being provided on only one side of the first blade part.

The flapper may also be configured as not being provided with the pair of fin parts. As a means to make the flapper swingable, instead of using a separate metal shaft body, for example, a means can be used where a convex part serving as the swing center of the flapper is provided on one of the flapper and the support member of the flapper, and a concave part into which the convex part is fit is provided on the other. Moreover, it is possible to configure to swing by using the driving force of a motor, for example.

The fuel gas may be, for example, natural gas or LP gas, but the specific type is not limited. The combustion device related to the invention is not limited to a device for a hot water device, but may also be a combustion device used for other purposes such as for heating or incineration. Furthermore, it is not limited to the type where the combustion gas progresses downward, but may also be of a type where the combustion gas progresses upward, for example.

PREMIXING DEVICE AND COMBUSTION DEVICE INCLUDING THE SAME

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