PREMIXING DEVICE AND COMBUSTION DEVICE INCLUDING THE PREMIXING DEVICE

Abstract

A premixing device includes: a gas flow path for allowing air to flow; a gas outlet that allows fuel gas to flow out into the gas flow path by utilizing a negative pressure; and a flapper disposed in the gas flow path. The premixing device further includes an operation regulating part for the flapper which allows the opening degree of the flapper to change according to the air flow rate in a range below a predetermined upper limit position while preventing the flapper from rotating in an opening direction beyond the upper limit position. The operation regulating part is capable of selectively switching and setting one of a first upper limit position for normal combustion and a second upper limit position for fuel ignition. The opening degree of the flapper at the second upper limit position is smaller than that at the first upper limit position.

Claims

1. A premixing device comprising: a gas flow path for allowing air to flow in a predetermined direction; at least one gas outlet that allows fuel gas to flow out into the gas flow path by utilizing a negative pressure generated in the gas flow path; and a flapper disposed in the gas flow path, being rotatable around an axis extending in a direction intersecting a flow direction of the air, and changing an opening degree according to an air flow rate so that when the air flow rate in the gas flow path is small, the opening degree is smaller than when the air flow rate is large, the premixing device further comprising: an operation regulating part for the flapper which allows the opening degree of the flapper to change according to the air flow rate in a range below a predetermined upper limit position while preventing the flapper from rotating in an opening direction beyond the upper limit position, wherein the operation regulating part is capable of selectively switching and setting one of a first upper limit position for normal combustion and a second upper limit position for fuel ignition as the upper limit position of the flapper, and the opening degree of the flapper at the second upper limit position is smaller than the opening degree of the flapper at the first upper limit position.

2. The premixing device according to claim 1, wherein at least the second upper limit position of the first and second upper limit positions is changeable.

3. The premixing device according to claim 1, wherein the operation regulating part comprises a contact member for contacting the flapper and an actuator capable of moving the contact member, a configuration in which the upper limit position of the flapper is set to the second upper limit position is a configuration in which the contact member is contactable with the flapper to prevent the flapper from further rotation when the flapper is at the second upper limit position, and a configuration in which the upper limit position of the flapper is set to the first upper limit position is a configuration in which the contact member or a member other than the contact member is contactable with the flapper to prevent the flapper from further rotation when the flapper is at the first upper limit position.

4. The premixing device according to claim 2, wherein the operation regulating part comprises a contact member for contacting the flapper and an actuator capable of moving the contact member, a configuration in which the upper limit position of the flapper is set to the second upper limit position is a configuration in which the contact member is contactable with the flapper to prevent the flapper from further rotation when the flapper is at the second upper limit position, and a configuration in which the upper limit position of the flapper is set to the first upper limit position is a configuration in which the contact member or a member other than the contact member is contactable with the flapper to prevent the flapper from further rotation when the flapper is at the first upper limit position.

5. The premixing device according to claim 3, wherein the actuator is capable of reciprocally moving the contact member in a direction facing the flapper, and is capable of fixing the contact member at a desired position within a range of a reciprocating stroke.

6. The premixing device according to claim 4, wherein the actuator is capable of reciprocally moving the contact member in a direction facing the flapper, and is capable of fixing the contact member at a desired position within a range of a reciprocating stroke.

7. The premixing device according to claim 3, wherein the gas outlet comprises a first gas outlet and a second gas outlet provided on an inner peripheral wall of the gas flow path to be located in regions on opposite sides to each other across a center of the gas flow path, and the flapper is provided to be able to approach and separate from the first gas outlet, and the contact member is inserted into the second gas outlet without completely closing the second gas outlet, and one end of the contact member is contactable with the flapper, and the other end of the contact member is supported by the actuator provided outside the gas flow path.

8. The premixing device according to claim 4, wherein the gas outlet comprises a first gas outlet and a second gas outlet provided on an inner peripheral wall of the gas flow path to be located in regions on opposite sides to each other across a center of the gas flow path, and the flapper is provided to be able to approach and separate from the first gas outlet, and the contact member is inserted into the second gas outlet without completely closing the second gas outlet, and one end of the contact member is contactable with the flapper, and the other end of the contact member is supported by the actuator provided outside the gas flow path.

9. The premixing device according to claim 5, wherein the gas outlet comprises a first gas outlet and a second gas outlet provided on an inner peripheral wall of the gas flow path to be located in regions on opposite sides to each other across a center of the gas flow path, and the flapper is provided to be able to approach and separate from the first gas outlet, and the contact member is inserted into the second gas outlet without completely closing the second gas outlet, and one end of the contact member is contactable with the flapper, and the other end of the contact member is supported by the actuator provided outside the gas flow path.

10. The premixing device according to claim 6, wherein the gas outlet comprises a first gas outlet and a second gas outlet provided on an inner peripheral wall of the gas flow path to be located in regions on opposite sides to each other across a center of the gas flow path, and the flapper is provided to be able to approach and separate from the first gas outlet, and the contact member is inserted into the second gas outlet without completely closing the second gas outlet, and one end of the contact member is contactable with the flapper, and the other end of the contact member is supported by the actuator provided outside the gas flow path.

11. A combustion device comprising: a fan; a premixing device provided on an intake side of the fan and mixing air and fuel gas and then sending it to the fan; and a burner that burns the fuel gas by receiving a mixture of the air and the fuel gas from the fan, the premixing device according to claim 1 is used as the premixing device.

12. The combustion device according to claim 11, wherein at least the second upper limit position of the first and second upper limit positions is changeable.

13. The combustion device according to claim 11, wherein the operation regulating part comprises a contact member for contacting the flapper and an actuator capable of moving the contact member, a configuration in which the upper limit position of the flapper is set to the second upper limit position is a configuration in which the contact member is contactable with the flapper to prevent the flapper from further rotation when the flapper is at the second upper limit position, and a configuration in which the upper limit position of the flapper is set to the first upper limit position is a configuration in which the contact member or a member other than the contact member is contactable with the flapper to prevent the flapper from further rotation when the flapper is at the first upper limit position.

14. The combustion device according to claim 12, wherein the operation regulating part comprises a contact member for contacting the flapper and an actuator capable of moving the contact member, a configuration in which the upper limit position of the flapper is set to the second upper limit position is a configuration in which the contact member is contactable with the flapper to prevent the flapper from further rotation when the flapper is at the second upper limit position, and a configuration in which the upper limit position of the flapper is set to the first upper limit position is a configuration in which the contact member or a member other than the contact member is contactable with the flapper to prevent the flapper from further rotation when the flapper is at the first upper limit position.

15. The combustion device according to claim 13, wherein the actuator is capable of reciprocally moving the contact member in a direction facing the flapper, and is capable of fixing the contact member at a desired position within a range of a reciprocating stroke.

16. The combustion device according to claim 14, wherein the actuator is capable of reciprocally moving the contact member in a direction facing the flapper, and is capable of fixing the contact member at a desired position within a range of a reciprocating stroke.

17. The combustion device according to claim 13, wherein the gas outlet comprises a first gas outlet and a second gas outlet provided on an inner peripheral wall of the gas flow path to be located in regions on opposite sides to each other across a center of the gas flow path, and the flapper is provided to be able to approach and separate from the first gas outlet, and the contact member is inserted into the second gas outlet without completely closing the second gas outlet, and one end of the contact member is contactable with the flapper, and the other end of the contact member is supported by the actuator provided outside the gas flow path.

18. The combustion device according to claim 14, wherein the gas outlet comprises a first gas outlet and a second gas outlet provided on an inner peripheral wall of the gas flow path to be located in regions on opposite sides to each other across a center of the gas flow path, and the flapper is provided to be able to approach and separate from the first gas outlet, and the contact member is inserted into the second gas outlet without completely closing the second gas outlet, and one end of the contact member is contactable with the flapper, and the other end of the contact member is supported by the actuator provided outside the gas flow path.

19. The combustion device according to claim 15, wherein the gas outlet comprises a first gas outlet and a second gas outlet provided on an inner peripheral wall of the gas flow path to be located in regions on opposite sides to each other across a center of the gas flow path, and the flapper is provided to be able to approach and separate from the first gas outlet, and the contact member is inserted into the second gas outlet without completely closing the second gas outlet, and one end of the contact member is contactable with the flapper, and the other end of the contact member is supported by the actuator provided outside the gas flow path.

20. The combustion device according to claim 16, wherein the gas outlet comprises a first gas outlet and a second gas outlet provided on an inner peripheral wall of the gas flow path to be located in regions on opposite sides to each other across a center of the gas flow path, and the flapper is provided to be able to approach and separate from the first gas outlet, and the contact member is inserted into the second gas outlet without completely closing the second gas outlet, and one end of the contact member is contactable with the flapper, and the other end of the contact member is supported by the actuator provided outside the gas flow path.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 is a schematic illustration view showing an example of a combustion device including a premixing device according to the disclosure.

[0033] FIG. 2 is an external perspective view of the premixing device of FIG. 1.

[0034] In FIG. 3, (a) is a cross-sectional view of the premixing device of FIGS. 1 and 2, and (b) is a cross-sectional view of IIIb-IIIb of (a).

[0035] FIG. 4 is a cross-sectional view showing an example of a state in which the position of the contact member of the premixing device shown in FIG. 3 is changed.

[0036] FIG. 5 is a perspective view of the flapper used in the premixing device shown in FIGS. 1 to 4.

DESCRIPTION OF EMBODIMENTS

[0037] Hereinafter, exemplary embodiments of the disclosure will be specifically described with reference to the drawings.

[0038] FIG. 1 shows a premixing device A, a combustion device B (premixing combustion device) configured by combining the premixing device A with a fan 1 and a burner 2, and a hot water device WH configured by combining the combustion device B with a primary heat exchanger 11a and a secondary heat exchanger 11b.

[0039] The details of the premixing device A will be described later, and a mixed gas (combustible mixed gas) of air and fuel gas is generated using this premixing device A, and this mixed gas is supplied to the burner 2 via the fan 1. The burner 2 is configured to include a porous plate 21 having multiple ventilation holes 20 and is housed in a case 10. The burner 2 is provided with a spark plug (not shown), a flame detection sensor, and the like. The mixed gas passes through the multiple ventilation holes 20 and burns below the porous plate 21. The combustion gas generated by the burner 2 acts sequentially on the primary heat exchanger 11a for recovering the sensible heat and the secondary heat exchanger 11b for recovering the latent heat, and hot water that passes through the inside of the primary heat exchanger 11a and the secondary heat exchanger 11b is heated. This produces hot water, which is supplied to the desired hot water supply destination.

[0040] The hot water device WH includes a control part 13 configured by using a microcomputer or the like, and the control part 13 also executes operation control of an actuator 7 of the premixing device A, as will be described later.

[0041] As shown in FIGS. 2 and 3, the premixing device A includes a device body A0, a flapper 5 assembled to the device body A0, a contact member 6 for contacting the flapper 5 to regulate operation, and an actuator 7 for moving the contact member 6.

[0042] The combination of the contact member 6 and the actuator 7 corresponds to an example of the operation regulating part for the flapper in the disclosure.

[0043] The device body A0 is configured by the combination of a tubular gas flow path forming part 3 and a housing part 4 surrounding the outer periphery thereof; the tubular gas flow path forming part 3 has a Venturi-shaped gas flow path 30 formed therein and is provided with first and second gas outlets 31a and 31b on the inner peripheral wall of the gas flow path 30.

[0044] The housing part 4 has a flange part 40 and a fuel gas supply port 41. Fuel gas is supplied to the fuel gas supply port 41 from a fuel gas supply part such as a gas pipe via a pressure equalizing valve (zero governor) V1 (see FIG. 1). A space 48 is formed between the gas flow path 30 and the housing part 4, and the space 48 functions as a flow path that may guide the fuel gas supplied to the fuel gas supply port 41 to the first and second gas outlets 31a and 31b.

[0045] The device body A0 is directly connected to the intake side of the fan 1 by using the flange part 40, or is connected by piping. When the fan 1 is driven, external air flows into the gas flow path 30 from the opening on one end side thereof and flows toward the opening on the other end side. Due to the negative pressure action generated due to this air flow, fuel gas flows out from the first and second gas outlets 31a and 31b into the gas flow path 30, a mixture of air and fuel gas is generated, and is taken into the fan 1.

[0046] A partition wall 32 for partitioning the gas flow path 30 into the first and second flow paths 30a and 30b is provided at or near the central part of the gas flow path 30. The first and second gas outlets 31a and 31b are located in regions opposite to each other with the center of the gas flow path 30 in between so as to face the first and second flow paths 30a and 30b individually.

[0047] The flapper 5 is a member that rotates in response to the air flow rate in the gas flow path 30 and changes the area that blocks the gas flow path 30. More specifically, as shown in FIG. 5, the flapper 5 includes a substantially semicircular plate-shaped flapper body 50, an extension 51 extending upward from the tip part of the flapper body 50, and a base end 52 for rotation support. The base end 52 is supported by a shaft part 9 provided to be located below the partition wall 32, and the flapper 5 is rotatable around an axis CL (corresponding to the central axis of the shaft part 9; see also FIG. 5) extending in a direction intersecting the air flow direction in the gas flow path forming part 3.

[0048] The upper part of the flapper 5 is located in the first flow path 30a, and when the air flow rate in the gas flow path 30a is smaller than a predetermined flow rate, the flapper 5 is in a in a closed state that closes the first flow path 30 and the first gas outlet 31a, respectively. In addition, when the air flow rate is greater than or equal to the predetermined flow rate, the flapper 5 is in an open state rotated in a direction away from the first gas outlet 31a. However, as described later, the upper limit position of the rotation may be switched to one of the first and second upper limit positions P1 and P2.

[0049] The contact member 6 has, for example, a shaft shape, is inserted into the second gas outlet 31b and a hole 33 provided in the partition wall 32, and a tip (one end) side of the contact member 6 is disposed to be able to contact the flapper 5. The base end (other end) side of the contact member 6 is supported by the actuator 7. The second gas outlet 31b has a larger opening size than the first gas outlet 31a to avoid a fully closed state or an insufficient opening size due to the contact member 6 being inserted. The vicinity of the boundary between the flapper body 50 and the extension 51 is bent to be recessed on the side opposite to the contact member 6 in the side view. The tip of the contact member 6 may be in contact with the bent part in a stable state.

[0050] The actuator 7 allows the contact member 6 to move reciprocally in the direction facing the flapper 5 (horizontal direction), and for example, it is a linear motion type stepping motor, and is assembled to the outer surface of the device body A0 by using a screw member 98 or the like. Further, the actuator 7 may fix the contact member 6 at a desired position within the range of the reciprocating stroke of the contact member 6.

[0051] The contact member 6 sets the position where the flapper 5 contacts the contact member 6 as the upper limit position of the rotation of the flapper 5, and prevents the flapper 5 from rotating with a large opening degree beyond this upper limit position. However, it is allowed for the flapper 5 to rotate to an opening degree smaller than that.

[0052] The control part 13 executes operation control and various data processing of each part of the hot water device WH, and by controlling the actuator 7 and changing the fixed position of the contact member 6, selectively switches and sets one of the first and second upper limit positions P1 and P2 as the upper limit position of the rotation of the flapper 5.

[0053] Here, the first upper limit position P1 is a position for normal combustion of the combustion device B, and, for example, as shown in FIG. 4, the distance L1 between the tip end of the contact member 6 and the inner wall surface of the gas flow path 30 is relatively large, so the flapper 5 is at a position where it comes into close contact with or comes into contact with the partition wall 32. When setting the first upper limit position P1, the tip end of the contact member 6 may be brought into contact with the flapper 5 to regulate the position of the flapper 5, but instead of this, for example, the flapper 5 may be brought into contact with the partition wall 32 to prevent further rotation, and the tip end of the contact member 6 may be disposed to be separated from the flapper 5.

[0054] The second upper limit position P2 is a position for fuel ignition. For example, as shown in (a) of FIG. 3, the distance L2 between the tip end of the contact member 6 and the inner wall surface of the gas flow path 30 is shorter than the distance L1, so the maximum opening degree of the flapper 5 is smaller than that in the case of the first upper limit position P1, and the flapper 5 is located at a position where the flapper 5 approaches the first gas outlet 31a.

[0055] The upper limit position of the flapper 5 is selectively switched to one of the first and second upper limit positions P1 and P2, and this switching setting is executed by the control of the control part 13 corresponding to the operation mode of the combustion device B. Specifically, in the burner 2 of the combustion device B, when the fuel is ignited, the second upper limit position P2 of the flapper 5 shown in (a) of FIG. 3 is set. During normal combustion after ignition, the first upper limit position P1 of the flapper 5 shown in FIG. 4 is set.

[0056] The actuator 7 may fix the contact member 6 at a desired position within the range of the reciprocating stroke of the contact member 6, and the disposition may be changed. Therefore, both the first and second upper limit positions P1 and P2 of the flapper 5 may be appropriately changed. This change may be made by operating, for example, a remote controller (not shown) provided in the combustion device B (hot water device WH), an operation part provided separately, or the like.

[0057] Next, the operations of the premixing device A and the combustion device B described above will be described.

[0058] First, when fuel ignition is performed in the burner 2 of the combustion device B, the premixing device A is controlled by the control part 13 and set to a state in which the upper limit position of the flapper 5 is the second upper limit position P2, as shown in (a) of FIG. 3. In this state, since the opening degree of the flapper 5 is suppressed to be small, the flow velocity of the air flowing near the first gas outlet 31a is increased, and the negative pressure acting on the first gas outlet 31a is strengthened. When the air flow rate in the gas flow path 30 is large, the flapper 5 normally rotates greatly as shown in FIG. 4, but at the time of fuel ignition, such rotation is blocked by the contact member 6, and the state of (a) of FIG. 3 described above is set. Therefore, the amount of fuel gas flowing out from the first gas outlet 31a to the gas flow path 30 is increased, and the air-fuel mixture can have a fuel-rich air-fuel ratio and a small ignition energy. This improves the ignition performance.

[0059] When the fuel ignition is completed and the burner 2 is in the normal combustion mode, the premixing device A is controlled by the control part 13 and set to a state in which the upper limit position of the flapper 5 is the first upper limit position P1 as shown in FIG. 4. In this state, since the opening degree of the flapper 5 may be made larger than that at the time of fuel ignition, it is possible to avoid the air-fuel ratio of the air-fuel mixture from becoming fuel-rich, and the mixture with an air-fuel ratio suitable for the normal combustion mode of the burner 2 may be obtained. In addition, although the upper limit position of the flapper 5 is restricted to the first upper limit position P1 by the contact member 6, the rotation of the flapper 5 at an angle lower than that is not hindered by the contact member 6. Therefore, the flapper 5 has good responsiveness, and when the air flow rate in the gas flow path 30 becomes smaller than the predetermined flow rate, the flapper 5 rotates rapidly to close the first flow path 30a and the first gas outlet 31a. As a result, the flow velocity of the air in the second flow path 30b becomes high, and an appropriate amount of fuel gas outflow from the second gas outlet 31b to the second flow path 30b may be appropriately continued.

[0060] As described above, according to this embodiment, it is possible to achieve good responsiveness of the operation of the flapper 5, and good performance of maintaining the air-fuel mixture at an appropriate air-fuel ratio during normal combustion of the burner 2. It is also suitable for obtaining a high turndown ratio.

[0061] The operation of the flapper 5 to quickly close the first flow path 30a and the first gas outlet 31a when the air flow rate in the gas flow path 30 becomes smaller than the predetermined flow rate may be similarly generated even in the setting state shown in (a) of FIG. 3, that is, when the upper limit position of the flapper 5 is set to the second upper limit position P2.

[0062] In this embodiment, as described above, each of the first and second upper limit positions P1 and P2 of the flapper 5 may be appropriately changed. Therefore, there is an advantage that the first and second upper limit positions P1 and P2 may be adjusted to the optimum positions in consideration of the specific usage conditions of the premixing device A, such as the output of the fan 1 and the type of fuel gas.

[0063] The disclosure is not limited to the contents of the above-described embodiments. The specific configuration of each part of the premixing device and the combustion device according to the disclosure may be variously redesigned within the scope of the disclosure.

[0064] The flapper 5 in the above-described embodiment switches between an open state and a closed state depending on whether the air flow rate of the first flow path 30a is greater than or equal to a predetermined flow rate, but it is not limited thereto. In the disclosure, for example, it may be configured that the opening degree of the flapper 5 changes in a stepless or multi-stepped way according to the air flow rate so that the opening degree of the flapper 5 gradually decreases as the air flow rate of the first flow path 30a decreases.

[0065] Further, in the above-described embodiment, the gas flow path 30 is divided into the first and second flow paths 30a and 30b, and the flapper 5 is disposed in the first flow path 30a, but the disclosure is not limited thereto. It is also possible to have a configuration in which the flapper 5 is provided without dividing the gas flow path 30 into multiple flow paths.

[0066] In the above-described embodiment, the operation regulating part for the flapper is configured by combining a shaft-shaped contact member and an actuator that reciprocally moves the shaft-shaped contact member, but the disclosure is not limited thereto. For example, as the contact member 6, a member other than a shaft-shaped one may be used. Further, as the actuator, a device other than the linear motion type stepping motor may also be used.

[0067] The first and second upper limit positions of the flapper in the disclosure may be appropriately selected or changed according to the usage conditions of the premixing device and the like, and the specific positions thereof are not limited.

[0068] The gas flow path is preferably, but not limited to, Venturi-like. It is not necessary to provide multiple gas outlets, and at least one gas outlet may be provided. The specific shape, material, size, and the like of the flapper are not limited.

[0069] The fuel gas is, for example, natural gas or LP gas, but the specific type of the fuel gas is not limited. The combustion device according to the disclosure is not limited to being applied to the hot water device, and may be a combustion device for other purposes such as for heating and incinerator. Further, the type is not limited to the type in which the combustion gas advances downward, and the type in which the combustion gas advances upward, for example, may be used.