PREMIXING DEVICE AND COMBUSTION DEVICE INCLUDING THE SAME

Abstract

A premixing device which includes a premixing flow path including a first flow path and a second flow path, and a first fuel gas outlet and a second fuel gas outlet includes: a first blade section which is provided in the first flow path, and with which the first fuel gas outlet is provided; a protruding wall section which is provided on the first blade section; and a flapper which oscillates at a position downstream in the air flow direction than the first blade portion of the first flow path. When the flapper is in an open state below a specified opening degree, the flow of air from the first flow path to the first fuel gas outlet is capable of being suppressed by the protruding wall section.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefits of Japanese application no. 2023-199943, filed on Nov. 27, 2023. 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 disclosure relates to a premixing device and a combustion device including the same. Here, “premixing” refers to the process of mixing air and fuel gas in advance to generate a combustible mixture, with the purpose of performing premixing combustion.

Description of Related Art

A specific example of a premixing device is described in Patent Literature 1 (Japanese Patent Application Laid-Open No. 2021-99204).

The premixing device described in the document includes a Venturi-shaped premixing flow path that has one end side open to the exterior and the other end side connected to the intake side of a fan. When the fan is driven, external air is allowed to flow in from the opening at the one end side and flow in a specified direction. The premixing flow path is partitioned into a first flow path and a second flow path by a partition wall section, and a first fuel gas outlet and a second fuel gas outlet are provided on the inner peripheral wall surfaces of the first flow path and the second flow path, respectively. Additionally, a flapper that is capable of oscillating to open and close the first flow path is provided in the first flow path. The flapper is configured to change the opening degree thereof in response to the air flow rate, such that when the air flow rate in the first flow path is low, the opening degree is smaller than when the air flow rate is high.

In such a premixing device, when air flows through the premixing flow path and negative pressure acts on the first fuel gas outlet and the second fuel gas outlet, fuel gas flows out from the first fuel gas outlet and the second fuel gas outlet into the premixing flow path. The fuel gas mixes with the aforementioned air, generating a mixture. On the other hand, 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 when the air flow rate is low, an appropriate amount of fuel gas can be made to flow out from the second fuel gas outlet due to the aforementioned negative pressure. Such an effect is effective in increasing the turn-down ratio.

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

In other words, the flapper in the aforementioned conventional technology merely opens and closes the first flow path, leaving the first fuel gas outlet in an open state. Therefore, for example, even if the first flow path is switched from an open state to a closed state by the flapper, fuel gas may continue to flow out from the first fuel gas outlet for a period of time thereafter. Furthermore, due to pressure fluctuations in the first flow path caused by the influence of the air flow in the second flow path, air from the first flow path may flow into (backflow into) the first fuel gas outlet, or fuel gas may needlessly flow out from the first fuel gas outlet. This makes it difficult to maintain the mixture at the desired appropriate mixing ratio.

As a way to resolve the aforementioned, there is a method of providing an additional flapper to open and close the first fuel gas outlet (refer to Patent Literature 2 (U.S. Pat. No. 9,677,759)). 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, resulting in higher manufacturing costs.

Furthermore, when the flapper changes from a closed state to an open state, the effective flow path area of the premixing flow path changes abruptly. As a result, the flow velocity of the air flow that has been occurring in the second flow path may rapidly decrease due to the influence. This may lead to a sudden change in the mixing ratio of the mixture, causing the mixture be fuel lean, which is an inappropriate mixing ratio.

The disclosure provides a premixing device and a combustion device including the same, which are capable of increasing a turn-down ratio with a simple structural way, while also having exemplary performance of maintaining an appropriate mixing ratio of the mixture.

SUMMARY

The disclosure adopts the following technical way.

The premixing device provided according to a first aspect of the disclosure which includes a premixing flow path to which air is supplied from the outside and for generating a mixture by mixing fuel gas with the air, a partition wall section which divides the premixing flow path into a first flow path and a second flow path arranged in parallel, and a first fuel gas outlet and a second fuel gas outlet capable of discharging fuel gas into the first flow path and the second flow path, respectively, utilizing negative pressure generated by air flow in the first flow path and the second flow path includes: a first blade section provided in the first flow path and provided with the first fuel gas outlet facing a downstream side in an air flow direction; a protruding wall section provided on the first blade section to protrude from an edge section of the first fuel gas outlet towards the downstream side in the air flow direction; and a flapper which oscillates in a direction facing the first blade section, at a position downstream in the air flow direction than the first blade section within the first flow path, and is capable of opening and closing both the first flow path and the first fuel gas outlet according to an air flow rate of the premixing flow path while avoiding interference with the protruding wall section. The premixing device is configured such that when the flapper is in an open state below a specified opening degree, the flow of air from the first flow path to the first fuel gas outlet may be suppressed by the protruding wall section.

According to the configuration, when the air flow rate supplied to the premixing flow path is low, the first flow path is closed by the flapper, and fuel gas discharged from the second fuel gas outlet is mixed with the air flowing through the second flow path. On the other hand, when the air flow rate is high, air also flows through the first flow path, and fuel gas discharged from the first fuel gas outlet is mixed with the air. Therefore, similar to Patent Literature 1, a turn-down ratio may be increased. Furthermore, the disclosure provides the following effects.

Firstly, the flapper is capable of not only opening and closing the first flow path but also opening and closing the first fuel gas outlet. Therefore, when the first flow path is in a closed state, needless fuel gas may be appropriately prevented from flowing out of the first fuel gas outlet afterwards by simultaneously closing the first fuel gas outlet. As a way to achieve this, two separate flappers for the first flow path and the first fuel gas outlet do not need to be used, so the overall configuration may be simplified, and manufacturing costs may be reduced.

Secondly, conventionally, when the flapper changed from a closed state to an open state below a specified opening degree (small open state), air from the first flow path might flow back into the first fuel gas flow path and the second fuel gas flow path through the first fuel gas outlet due to negative pressure generated in the second flow path. In contrast, in the disclosure, when the flapper changes from a closed state to an open state, the protruding wall section suppresses the air from the first flow path from flowing into the first fuel gas outlet. As a result, the aforementioned backflow of air may be appropriately prevented or suppressed. Therefore, when the flapper changes from a closed state to an open state, the formation of an inappropriate mixing ratio where the mixture becomes fuel lean is appropriately suppressed.

Thirdly, when the flapper changes from a closed state to an open state, the protruding wall section creates air resistance in the first flow path. As a result, when the flapper changes from a closed state to an open state, the air flow velocity in the second flow path, which has been occurring previously, can be prevented from rapidly decreasing. Consequently, the mixing ratio of the mixture may be appropriately suppressed from becoming an inappropriate fuel lean mixing ratio.

In the disclosure, preferably, as a way to avoid interference between the flapper and the protruding wall section, the flapper includes a hole section into which the protruding wall section enters when the flapper is in an open state below the specified opening degree.

According to the configuration, interference between the flapper and the protruding wall section can be accurately avoided with a simple configuration that merely requires providing a hole section in the flapper. This is preferable for suppressing increases in manufacturing costs and weight.

In the disclosure, preferably, the protruding wall section has a height such that the height allows the protruding wall section to exit from the hole section of the flapper when the flapper is in an open state greater than the specified opening degree.

According to the configuration, when the air flow rate supplied to the premixing flow path is high and the opening degree of the flapper is large, the air resistance of the protruding wall section can be prevented from becoming excessively high.

In the disclosure, preferably, the hole section of the flapper is an elongated hole extending in a specific direction from a base end side closer to an oscillation center of the flapper to a tip section, and the protruding wall section is rib-shaped extending in a direction corresponding to the specific direction, and a chamfered section that is a flat-surface shape or a curved-surface shape is provided on a corner section of the tip section of the protruding wall section that is farther from the oscillation center of the flapper.

According to the configuration, when the flapper oscillates, interference between the flapper and the corner section of the tip section of the protruding wall section may be appropriately avoided due to the existence of the chamfered section. This is preferable for reducing the size of the hole section provided in the flapper.

In the disclosure, preferably, the protruding wall section extends continuously along the first fuel gas outlet, and a length thereof is substantially the same as a length of the first fuel gas outlet.

According to the configuration, the length of the protruding wall section becomes neither excessive nor insufficient, or slightly less, compared to the length of the first fuel gas outlet. As a result, while avoiding the malfunction of needlessly large air resistance due to an excessively large protruding wall section, the intended effect of the disclosure can be appropriately obtained. Specifically, the effect is to suppress the flow of air from the first flow path into the first fuel gas outlet when the flapper is in an open state (small open state) below a specified opening degree.

In the disclosure, preferably, an x direction and a y direction that intersect with each other exist as directions which intersect with the air flow direction. The first blade section extends in the y direction so as to span between a part and another part of an inner wall of the first flow path, thereby dividing a part of the first flow path into a pair of divided flow paths. In the x direction, the first blade section and the first fuel gas outlet are positioned between the pair of divided flow paths. As the protruding wall section, a pair of protruding wall sections positioned at both edge sections in the x direction of the first fuel gas outlet is provided.

According to the configuration, when the flapper is in an open state and air flows through the first flow path, the air flows into the pair of divided flow paths positioned on both sides of the first fuel gas outlet in the x direction. Therefore, utilizing the negative pressure of the air flow, an amount of fuel gas corresponding to the air flow rate can be appropriately discharged from the first fuel gas outlet. On the other hand, in the case where the flapper is in an open state below a specified opening degree, the flow of air from each of the pair of divided flow paths into the first fuel gas outlet, causing backflow, is appropriately suppressed by the presence of the pair of protruding wall sections.

In the disclosure, preferably, no protruding wall sections are provided on both edge sections in the y direction of the first fuel gas outlet in the first blade section. The configuration is such that when the flapper is in an open state below the specified opening degree, the air in the first flow path is allowed to flow towards the both edge sections in the y direction of the first fuel gas outlet.

According to the configuration, when the flapper is in an open state below the specified opening degree, by allowing the air in the first flow path to flow near the both edge sections in the y direction of the first fuel gas outlet, the negative pressure caused by the air flow can be utilized to discharge fuel gas from the first fuel gas outlet into the first flow path. Due to the provision of the pair of protruding wall sections at the both edge sections in the x direction of the first fuel gas outlet, any hindrance to the discharge of fuel gas from the first fuel gas outlet may be appropriately prevented.

The disclosure preferably further includes: a premixing flow path forming member which forms the premixing flow path; a second blade section provided inside the second flow path with one end section connected to a peripheral wall section of the premixing flow path forming member and the other end section connected to the first blade section via the partition wall section, and provided with the second fuel gas outlet facing a downstream side in the air flow direction; a fuel gas receiving section which is provided on the peripheral wall section of the premixing flow path forming member, and receives a supply of fuel gas from the outside; a second fuel gas flow path provided inside the second blade section to be capable of leading a part of the fuel gas supplied to the fuel gas receiving section to the second fuel gas outlet; and a first fuel gas flow path provided to extend from inside the second blade section to inside the first blade section and capable of leading another part of the fuel gas supplied to the fuel gas receiving section to the first fuel gas outlet.

According to the configuration, by utilizing the first fuel gas flow path and the second fuel gas flow path provided inside the first blade section and the second blade section, fuel gas may be appropriately and rationally led from the fuel gas receiving section provided on an outer surface section of the premixing flow path forming member to the first fuel gas outlet and the second fuel gas outlet. The fuel gas receiving section may be provided in just one location, and it is needless to provide multiple fuel gas receiving sections corresponding to the respective first fuel gas outlet and second fuel gas outlet. Therefore, this is suitable for simplifying the overall configuration and reducing manufacturing costs.

Moreover, according to the configuration of the second blade section and the second fuel gas outlet provided on the second blade section, when air flows near the second blade section, negative pressure may be effectively generated, and the negative pressure may be strongly applied to the second fuel gas outlet. Therefore, in the case where the flapper of the first flow path is in a closed state due to a small amount of air supply to the premixing flow path, and fuel gas is discharged merely from the second fuel gas outlet, the discharge amount of fuel gas is sufficiently secured. This is even more preferable for increasing the turn-down ratio.

A combustion device provided according to a second aspect of the disclosure includes a fan, a premixing device which is provided on an intake side of the fan, generates a mixture by mixing air and fuel gas, and sends the mixture to the fan, and a burner section which receives a supply of the mixture from the fan and combusts the fuel gas. In the combustion device, the premixing device provided according to the first aspect of the disclosure is used as the aforementioned premixing device.

According to the configuration, similar effects as described for the premixing device provided according to the first aspect of the disclosure can be obtained.

The disclosure will become more apparent from the description of the embodiments of the disclosure to be given below with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic descriptive diagram showing an example of a combustion device including a premixing device related to the disclosure.

FIG. 2 is an external perspective view 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 shown in FIG. 1 at a different position from FIG. 4A, and FIG. 4C is a cross-sectional view taken along line IVc-IVc (cross-sectional view of a main part on the right side) in FIG. 4A.

FIG. 5A is a front cross-sectional view of the premixing device in the case where the flapper of the premixing device shown in FIG. 4A is in a fully open state, and FIG. 5B is a cross-sectional view of a main part on the right side in FIG. 5A.

FIG. 6A is a front cross-sectional view of the premixing device in the case where the flapper of the premixing device shown in FIG. 4A is in an open state below a specified opening degree, FIG. 6B is a cross-sectional view of a main part of the right side in FIG. 6A, and FIG. 6C is an enlarged cross-sectional view of a part in FIG. 6B.

FIG. 7A is a plan view of the premixing flow path forming member of the premixing device shown in FIG. 2 to FIG. 6A to FIG. 6C, FIG. 7B is a partially enlarged view thereof, and FIG. 7C is a plan cross-sectional view of the premixing flow path forming member.

FIG. 8 is a cross-sectional view of a main part showing the relationship between the flapper and the protruding wall section of the premixing device shown in FIG. 2 to FIG. 6A to FIG. 6C.

DESCRIPTION OF THE EMBODIMENTS

The disclosure will now be described in detail with reference to the drawings according to an exemplary embodiment.

FIG. 1 shows a hot water device WH. The hot water device WH is a water heating device 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 section 2 with 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, but using the premixing device A, a mixture (combustible mixture) of air and fuel gas is generated, and the mixture is supplied to the burner section 2 via the fan 1. The burner section 2 includes a perforated plate 21 having multiple air holes 20 (flame holes) and is housed in a case 10. The burner section 2 is provided with accessories such as an unillustrated ignition plug and a flame detection sensor. The aforementioned mixture passes through the air holes 20 and combusts below the perforated plate 21. The combustion gas generated by the burner section 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 a desired hot water supply destination.

As well shown in FIG. 2 to FIG. 6C, the premixing device A includes a device main body section A0 and a flapper 5 assembled to the device main body section A0.

In the figures, an x direction and a y direction are directions that intersect each other, and both intersect with an air flow direction in a premixing flow path 3 to be described later. In the embodiment, the air flow direction in the premixing flow path 3 is an up-down height direction of the premixing device A.

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

The premixing flow path forming member 4 includes a tubular section 49 that forms a Venturi-shaped premixing flow path 3 internally, a flange section 48 connected to the upper end of the tubular section 49, and a stepped base section 44 protruding on the outer surface section of the tubular section 49. The pipe body joint section 70 is attached to the base section 44 using screw members 90 such as screws in a manner that sandwiches the fuel gas control plate.

As shown in FIG. 1, the premixing device A has the pipe body joint section 70 thereof connected to a gas pipe 99, and receives fuel gas supply from an unillustrated fuel gas supply source via a zero governor V1. On the other hand, the premixing device A is directly or indirectly connected to the intake side of the fan 1 utilizing the flange section 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 section 49). Due to the negative pressure effect generated by the air flow, fuel gas flows out from the first fuel gas outlet 80a and the second fuel gas outlet 80b to be described later, and a mixture of the fuel gas and the aforementioned air is generated. The mixture is supplied to the burner section 2 via the fan 1.

As well shown in FIG. 4B, a partition wall section 40 extending in the up-down height direction, which is the air flow direction, is provided in the premixing flow path 3. As a result, a part of the premixing flow path 3 is partitioned into a first flow path 3a and a second flow path 3b arranged side by side in the y direction with the partition wall section 40 therebetween. The partition wall section 40 is disposed offset in the y direction from the center of the tubular section 49, and the first flow path 3a has a larger flow path area than the second flow path 3b. However, the first flow path 3a and the second flow path 3b may have the same flow path area.

As well shown in FIG. 4A to FIG. 7C, a first blade section 41a and a second blade section 41b (shown as dotted pattern sections in FIG. 7A and FIG. 7C) are provided in the first flow path 3a and the second flow path 3b. On the upper surface sections, which are the main surface sections facing the downstream side in the air flow direction, of the first blade section 41a and the second blade section 41b, a first fuel gas outlet 80a and a second fuel gas outlet 80b are provided in an upward opening state.

The first blade section 41a and the second blade section 41b extend in the y direction to cross the first flow path 3a and the second flow path 3b in a horizontal direction, respectively, and one end section of each is connected to the peripheral wall inner surface section of the premixing flow path 3 (the inner surface section of the peripheral wall section of the tubular section 49), and the other end section of each is connected to each other with the partition wall section 40 therebetween. As well shown in FIG. 7A to FIG. 7C, the first blade section 41a divides a part of the first flow path 3a into a pair of divided flow paths 3a′ through which air is able to flow. As a result, in the x direction, the first blade section 41a and the first fuel gas outlet 80a are positioned between the pair of divided flow paths 3a′.

The second blade section 41b divides a part of the second flow path 3b into a pair of divided flow paths 3b′ through which air is able to flow, and in the x direction, the second blade section 41b and the second fuel gas outlet 80b are positioned between the pair of divided flow paths 3b′.

In FIG. 44A, the pipe body joint section 70 forms a fuel gas receiving section 81 internally to receive a supply of fuel gas from the outside. The fuel gas supplied to the fuel gas receiving section 81 passes through openings 71a and 71b of a fuel gas control plate 71 and a first fuel gas flow path 8a and a second fuel gas flow path 8b, and is led to the first fuel gas outlet 80a and the second fuel gas outlet 80b.

Here, while the second fuel gas flow path 8b is provided inside the second blade section 41b and the base section 44, the first fuel gas flow path 8a is provided inside the first blade section 41a, the second blade section 41b, and the base section 44. The second blade section 41b is made greater in up-down thickness than the first blade section 41a, and inside the second blade section 41b, the first fuel gas flow path 8a and the second fuel gas flow path 8b overlap in the up-down height direction. According to the configuration, the fuel gas supply structure to the first fuel gas outlet 80a and the second fuel gas outlet 80b can be simplified. Additionally, by overlapping the first fuel gas flow path 8a and the second fuel gas flow path 8b in the up-down height direction, the width of the second blade section 41b in the horizontal direction (x direction) may be prevented from becoming too large, thus ensuring sufficient opening area for the pair of divided flow paths 3b′.

The fuel gas control plate 71, as described earlier, is attached to the base section 44 and includes two openings 71a and 71b facing the tip opening sections of the first fuel gas flow path 8a and the second fuel gas flow path 8b. By adjusting the opening areas of the openings 71a and 71b, the amount of fuel gas flowing from the fuel gas receiving section 81 into the first fuel gas flow path 8a and the second fuel gas flow path 8b may be controlled.

In the lower part and the upper part of the tubular section 49, an air inlet section 3c and an air outlet section 3d are formed, which are connected to the first flow path 3a and the second flow path 3b. In response to the fan 1 being driven, external air may flow into the air inlet section 3c and then branch into the first flow path 3a and the second flow path 3b. Due to the negative pressure effect generated by the air flow in the first flow path 3a and the second flow path 3b, as described earlier, fuel gas flows out from the first fuel gas outlet 80a and the second fuel gas outlet 80b, creating a mixture of air and fuel gas. The mixture flows out from the air outlet section 3d to the exterior of the tubular section 49.

The flapper 5, for example, is a resin molded product and is placed on the upper side (downstream side in the air flow direction) of the first blade section 41a in the first flow path 3a. The flapper 5 is capable of oscillating in opposition to the upper surface section of the first blade section 41a to simultaneously open and close the first flow path 3a (strictly speaking, the pair of divided flow paths 3a′) and the first fuel gas outlet 80a (refer to FIG. 4A to FIG. 6C). To describe more specifically, a shaft body 61, which serves as the oscillation point (oscillation center), is inserted through the rear part of the flapper 5, and the shaft body 61 is supported by a pair of left and right support members 60. Additionally, the pair of support members 60 is attached to a step section 43, which is separately provided in the first flow path 3a, using screw members 92 or the like.

The flapper 5 changes the opening degree thereof according to the air flow rate in the premixing flow path 3, such that the opening degree becomes smaller when the aforementioned air flow rate is low compared to when the aforementioned air flow rate is high. In the case where the aforementioned air flow rate is low, the flapper 5 lies horizontally due to its own weight, resulting in the closed state (fully closed state) shown in FIG. 4A to FIG. 4C. As the aforementioned air flow rate increases, the flapper 5 is lifted by the upward air flow, changing to, for example, the open state (fully open state) shown in FIG. 5A to FIG. 5B. FIG. 6A to FIG. 6C show a small open state where the opening degree of the flapper 5 is below a specified level.

As shown in FIG. 7A to FIG. 7C, a pair of protruding wall sections 45 is provided on the upper surface section of the first blade section 41a.

The pair of protruding wall sections 45 protrudes upward from the upper surface section of the first blade section 41a and is positioned at both edge sections of the first fuel gas outlet 80a in the x direction. As a result, in the x direction, the first blade section 41a, the pair of protruding wall sections 45, and the first fuel gas outlet 80a are positioned between the pair of divided flow paths 3a′. Each of the protruding wall sections 45 is rib-shaped, extending continuously in the y direction along the first fuel gas outlet 80a. Preferably, a length La of each of the protruding wall sections 45 in the y direction is approximately the same as a length Lb of the first fuel gas outlet 80a.

On the other hand, on the upper surface section of the first blade section 41a, no protruding wall section 45 or similar part is provided at both edge sections 46 in the y direction of the first fuel gas outlet 80a.

The flapper 5 has a pair of hole sections 55 as a way to avoid interference with the pair of protruding wall sections 45 during oscillation motion thereof. The pair of hole sections 55 are through holes that allow each of the protruding wall sections 45 to enter when the flapper 5 is in the closed state or small open state as shown in FIG. 4A to FIG. 4C and FIG. 6A to FIG. 6C. Additionally, each of the hole sections 55 has a shape corresponding to each of the protruding wall sections 45 and is in the form of an elongated hole extending in a specific direction from the base end section side closer to the oscillation center of the flapper 5 to the tip section.

Each of the protruding wall sections 45 is formed to a size capable of blocking the area between each of the pair of divided flow paths 3a′ of the first flow path 3a and the first fuel gas outlet 80a when the flapper 5 is in a specified small open state as shown in FIG. 6A to FIG. 6C, and a gap is formed between the flapper 5 and the first blade section 41a. As a result, each of the protruding wall sections 45 serves the role of suppressing the flow of air from the first flow path 3a into the first fuel gas outlet 80a. The height of each of the protruding wall sections 45 is such that the height allow the protruding wall section 45 to exit from the hole section 55 of the flapper 5 when the flapper 5 is not in a small open state with the opening degree below the specified level, but in an open state greater than the small open state.

As shown in FIG. 8, the side view shape of each of the protruding wall sections 45 is approximately rectangular. However, on a corner section 45a of the tip section of each of the protruding wall sections 45 that is farther from the shaft body 61, which is the oscillation center of the flapper 5, a chamfered section 45b in a curved-surface shape with a radius of curvature Ra is provided. This is preferable in order to avoid interference with the corner section 45a of the protruding wall section 45 when a peripheral section al on one end side of the hole section 55 of the flapper 5 shown in FIG. 8 moves along a circular arc trajectory with a radius Rb centered on the shaft body 61. The chamfered section 45b can also be made as a chamfered section in a flat-surface shape instead of a curved-surface shape.

Next, the operation of the aforementioned premixing device A and the combustion device B including the same will be described.

At the start of drive combustion of the burner section 2 of the combustion device B, or during subsequent normal drive combustion, the driving speed of the fan 1 is changed. As a result, the flow rate of the mixture supplied from the premixing device A to the burner section 2 is also changed, enabling control of the drive combustion power of the burner section 2.

In this case, when the driving speed of the fan 1 is low and the air flow rate in the premixing flow path 3 is small, as shown in FIG. 4A to FIG. 4C, the flapper 5 is in a closed state, and air does not flow into the first flow path 3a. In this case, air flows merely in the second flow path 3b. Therefore, by accelerating the air flow in the second flow path 3b and applying strong negative pressure to the second fuel gas outlet 80b, an appropriate amount of fuel gas corresponding to the air flow rate can be discharged into the second flow path 3b. On the other hand, when the driving speed of the fan 1 is high, for example, as shown in FIG. 5A to FIG. 5B, the flapper 5 is in an open state. In this case, air flows in both the first flow path 3a and the second flow path 3b, and an appropriate amount of fuel gas corresponding to the air flow rate can be discharged from both the first fuel gas outlet 80a and the second fuel gas outlet 80b. As a result, a turn-down ratio may 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 closed, the first fuel gas outlet 80a is also simultaneously closed, thus appropriately preventing malfunctions such as needless fuel gas flowing out from the first fuel gas outlet 80a afterwards. As a way to achieve this, two separate flappers for the first flow path 3a and the first fuel gas outlet 80a are not used, so the overall configuration of the premixing device A may be simplified, and manufacturing costs may be reduced.

The first fuel gas flow path 8a and the second fuel gas flow path 8b are in communication with each other through the fuel gas receiving section 81. Therefore, normally, when the flapper 5 changes from a closed state to a small open state as shown in FIG. 6A to FIG. 6C, an air backflow phenomenon may occur where air from the first flow path 3a flows into the fuel gas outlet 80a due to the negative pressure generated in the second flow path 3b. However, according to the embodiment, the pair of protruding wall sections 45 impede the aforementioned air flow. As a result, the aforementioned air backflow phenomenon is suppressed, and it is appropriately prevented that the mixture becomes an inappropriate mixing ratio that is fuel lean.

While the pair of protruding wall sections 45 are provided on both edge sections in the x direction among the peripheral section of the first fuel gas outlet 80a, no protruding wall sections 45 or similar parts are provided on the both edge sections 46 in the y direction (refer to FIG. 7A and FIG. 7B). Therefore, when the flapper 5 is in a small open state, the air from the first flow path 3a may be made to flow towards the both edge sections 46 in the y direction of the first fuel gas outlet 80a and proceed to the downstream side of the first flow path 3a. As a result, fuel gas may be made to appropriately flow from the first fuel gas outlet 80a into the first flow path 3a by utilizing the negative pressure created by the air flow. The insufficient fuel gas outflow when the flapper 5 is in a small open state, which may occur due to the provision of the pair of protruding wall sections 45, is appropriately avoided.

Furthermore, when the flapper 5 changes from a closed state to an open state, the effective flow path area of the premixing flow path 3 changes abruptly (rapid expansion).

Therefore, normally, the flow velocity of the air flow in the second flow path 3b may rapidly decrease, causing the mixing ratio of the mixture to abruptly change to a fuel lean state. However, in the embodiment, when the flapper 5 changes from a closed state to an open state, the pair of protruding wall sections 45 generate air resistance in the first flow path 3a. As a result, flow velocity of the air flow that has been occurring in the second flow path 3b may be prevented from rapidly decreasing when the flapper 5 changes from a closed state to an open state. Consequently, the mixing ratio of the mixture may be more appropriately suppressed from becoming an inappropriate fuel lean mixing ratio.

On the other hand, the pair of protruding wall sections 45 are capable of entering the hole sections 55 of the flapper 5 when the flapper 5 is in a specified small open state. However, the pair of protruding wall sections 45 are sized to be able to exit from the hole sections 55 when the opening degree of the flapper 5 becomes larger than the small open state below the specified level. Therefore, when the opening degree of the flapper 5 is large, it is appropriately avoided that the air resistance of the pair of protruding wall sections 45 becomes excessive, and pressure loss may be minimized.

The disclosure is not limited to the content of the aforementioned embodiment. The specific configuration of each of sections of the premixing device and combustion device related to the disclosure can be freely redesigned in various ways within the intended scope of the disclosure.

The premixing flow path is preferably Venturi-shaped, but is not limited thereto.

The specific shapes, sizes, materials, etc. of the first blade section and second blade section, flapper, protruding wall section, and others are not limited to the aforementioned embodiment. The first fuel gas outlet and second fuel gas outlet may be provided in multiple numbers each, rather than one each. The shape, size, number, disposition, etc. of the protruding wall section can be appropriately modified in accordance with the specific configuration of the first fuel gas outlet. The protruding wall section may be provided with at least one positioned between the first flow path and the first fuel gas outlet, and does not need to be provided in a pair.

The hole section for avoiding interference between the flapper and the protruding wall section does not need to be a through hole. For example, the hole section can be a concave hole section (non-through hole) that is deeper than the height of the protruding wall section and allows the entry of the protruding wall section. In the disclosure, the flapper and the protruding wall section may be in a relationship where interference with each other is avoided when the flapper is in an open state below a specified opening degree, and the specific way for this is not limited.

As a way to enable the oscillation of the flapper, instead of using a separate metal shaft body, for example, a way can be used where a convex section serving as the oscillation center of the flapper is provided on either the flapper or the support members of the flapper, and a concave section into which the aforementioned convex section fits is provided on the other. Furthermore, the flapper may also be configured to oscillate 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 disclosure is not limited to use in hot water devices, but can also be used for other purposes such as heating or incineration. Moreover, it is not limited to the type that directs combustion gas downward, but can also be of a type that directs combustion gas upward, for example.

Claims

1. A premixing device which comprises a premixing flow path to which air is supplied from the outside and for generating a mixture by mixing fuel gas with the air,a partition wall section which divides the premixing flow path into a first flow path and a second flow path arranged in parallel, anda first fuel gas outlet and a second fuel gas outlet that are capable of discharging fuel gas into the first flow path and the second flow path by utilizing negative pressure generated by air flow in the first flow path and the second flow path,the premixing device comprising:a first blade section, provided in the first flow path, and provided with the first fuel gas outlet facing a downstream side in an air flow direction;a protruding wall section, provided on the first blade section so as to protrude from an edge section of the first fuel gas outlet towards a downstream side in the air flow direction; anda flapper, oscillating in a direction facing the first blade section, at a position downstream in the air flow direction than the first blade section within the first flow path, and being capable of opening and closing both the first flow path and the first fuel gas outlet according to an air flow rate of the premixing flow path while avoiding interference with the protruding wall section, andwhen the flapper is in an open state below a specified opening degree, a configuration being such that flow of air from the first flow path into the first fuel gas outlet is capable of being suppressed by the protruding wall section.

2. The premixing device according to claim 1, wherein as a way to avoid interference between the flapper and the protruding wall section, the flapper comprises a hole section into which the protruding wall section enters when the flapper is in an open state below the specified opening degree.

3. The premixing device according to claim 2, wherein the protruding wall section has a height such that the height allows the protruding wall to exit from the hole section of the flapper when the flapper is in an open state greater than the specified opening degree.

4. The premixing device according to claim 3, wherein the hole section of the flapper is an elongated hole extending in a specific direction from a base end section side closer to an oscillation center of the flapper to a tip section,the protruding wall section is rib-shaped extending in a direction corresponding to the specific direction, and a chamfered section that is a flat-surface shape or a curved-surface shape is provided on a corner section of a tip section of the protruding wall section that is farther from the oscillation center of the flapper.

5. The premixing device according to claim 1, wherein the protruding wall section extends continuously along the first fuel gas outlet, and a length thereof is substantially the same as a length of the first fuel gas outlet.

6. The premixing device according to claim 1, wherein an x direction and a y direction that intersect with each other exist as directions which intersect with the air flow direction,the first blade section extends in the y direction so as to span between a part and another part of an inner wall of the first flow path, thereby dividing a part of the first flow path into a pair of divided flow paths, and in the x direction, the first blade section and the first fuel gas outlet are positioned between the pair of divided flow paths, anda pair of protruding wall sections is positioned at both edge sections in the x direction of the first fuel gas outlet as the protruding wall section.

7. The premixing device according to claim 6, wherein the protruding wall sections are not provided on the both edge sections in the y direction of the first fuel gas outlet of the first blade section, and when the flapper is in an open state below the specified opening degree, a configuration is such that air in the first flow path is allowed to flow towards the both edge sections in the y direction of the first fuel gas outlet.

8. The premixing device according to claim 1, further comprising: a premixing flow path forming member, forming the premixing flow path;a second blade section, provided inside the second flow path with one end section connected to a peripheral wall section of the premixing flow path forming member and the other end section connected to the first blade section via the partition wall section, and provided with the second fuel gas outlet facing a downstream side in the air flow direction;a fuel gas receiving section, provided on the peripheral wall section of the premixing flow path forming member and receiving a supply of fuel gas from the outside;a second fuel gas flow path, provided inside the second blade section to be capable of leading a part of the fuel gas supplied to the fuel gas receiving section to the second fuel gas outlet; anda first fuel gas flow path, provided to extend from inside the second blade section to inside the first blade section, and capable of leading another part of the fuel gas supplied to the fuel gas receiving section to the first fuel gas outlet.

9. A combustion device, comprising: a fan;a premixing device, provided on an intake side of the fan, generating a mixture by mixing air and fuel gas, and sending the mixture to the fan; anda burner section, receiving a supply of the mixture from the fan and combusting the fuel gas, andthe premixing device according to claim 1 being used as the premixing device.