JP2023048282A - Premixing device, and combustion device and hot water device including the same - Google Patents

Abstract

To provide a premixing device capable of properly achieving both low NOx and improvement in ignition performance.SOLUTION: A premixing device A includes: a gas circulation passage 30 where air circulates; and a gas supply path R1 capable of guiding a fuel gas supplied to a fuel gas supply port 44 to first and second gas outflow ports 31, 32. The premixing device also includes: an additional gas supply path R2 capable of guiding an exhaust gas supplied to an exhaust gas supply port 45 to the second gas outflow port 32; and gas supply path switching means V1, V2 capable of selectively communicating one of the gas supply path R1 and the additional gas supply path R2 with the second gas outflow port 32.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a premixing device, a combustion device and a water heating device having the same.
Here, "premixing" is a process of premixing air and fuel gas to generate a combustible mixed gas for the purpose of performing premixing combustion.

Patent Documents 1 and 2 disclose specific examples of the premixing device.
The premixing devices described in these documents have a gas flow passage forming portion that forms a venturi-shaped gas flow passage therein, one end of which is open to the outside and the other end of which is connected to the intake side of a fan. I have. Further, a gas outlet facing the gas flow passage is provided on the inner peripheral surface portion of the gas flow passage.
In such a premixing device, air flows through the gas flow passage and negative pressure is generated near the gas outlet, so that the fuel gas flows out from the gas outlet into the gas flow passage and is mixed with the air. . Since the gas flow path is venturi-shaped, it is possible to increase the flow velocity of the air and effectively generate the negative pressure.

However, the prior art still has room for improvement as described below.

That is, from the viewpoint of environmental protection, a combustion apparatus using a premixing device is required to reduce NOx, as is the case with other types of combustion apparatus. Here, it is conceivable to use exhaust gas recirculation (EGR) as a means for reducing NOx (see, for example, Patent Documents 3 and 4). In this exhaust gas recirculation approach, a portion of the exhaust gas (combustion exhaust gas) is further mixed into the mixture of fuel gas and air. Since the exhaust gas contains an inert gas such as carbon monoxide, the oxygen concentration in the air-fuel mixture is lowered, and the combustion temperature is lowered. NOx is more likely to be generated as the combustion temperature is higher, and according to the exhaust gas recirculation technique described above, it is possible to lower the combustion temperature and reduce NOx.

On the other hand, a combustion device using a premixer is also required to have good ignition performance.
However, the air ratio of the air-fuel mixture is determined by the design specifications of the gas flow passage, the gas outlet, etc., and it is difficult to adjust the air-fuel mixture to an air ratio with low ignition energy when the combustion device is ignited. . In particular, if the exhaust gas recirculation (EGR) technique described above is used to reduce NOx, the ignition performance is considered to deteriorate further.
As a means for improving the ignition performance, it is conceivable to increase the discharge energy of the ignition device, but this leads to an increase in the size and cost of the ignition device.

JP 2018-132257 A Japanese Patent Application Laid-Open No. 2021-25722 JP-A-11-132404 Japanese Patent No. 2782407

The present invention has been conceived under the circumstances as described above, and a premixing device capable of appropriately achieving both reduction in NOx and improvement in ignition performance, a combustion device having the same, and The object is to provide a water heater.

In order to solve the above problems, the present invention takes the following technical means.

A premixing device provided by a first aspect of the present invention is a device main body having a gas flow passage for circulating air in a predetermined direction, and first and second gas outlets communicating with the gas flow passage. and a gas supply port having a fuel gas supply port at one end thereof, and guiding the fuel gas supplied to the fuel gas supply port to the first and second gas outlets so as to flow out to the gas flow passage. and a path, which has an exhaust gas supply port at one end, and guides the exhaust gas supplied to the exhaust gas supply port to the second gas outlet and into the gas flow passage an additional gas supply path capable of flowing out; a gas supply path switching means capable of selectively connecting one of the gas supply path and the additional gas supply path to the second gas outlet; is further provided.

According to such a configuration, the following effects are obtained.
That is, when the premixing device according to the present invention is used as a component of a combustion device equipped with a burner, during normal combustion of the combustion device, the additional gas is supplied to the second gas outlet of the premixing device. Keep the paths connected. In this state, the exhaust gas supplied to the exhaust gas supply port is led to the second gas outlet and flows out to the gas flow passage. Of course, the fuel gas flows out to the gas flow path from the first gas outlet. Therefore, the technique of exhaust gas recirculation (EGR) can lower the combustion temperature and appropriately reduce NOx.
On the other hand, in the combustion device, when the fuel is ignited, the gas supply path can be switched to communicate with the second gas outlet of the premixer. In this state, the fuel gas is led to the second gas outlet, and the fuel gas flows out from both the first and second gas outlets into the gas flow path. Therefore, it is possible to make the air-fuel mixture generated by the premixing device have an air ratio with small ignition energy and improve the ignition performance.
Thus, according to the present invention, it is possible to appropriately achieve both reduction in NOx and improvement in ignition performance.

In the present invention, preferably, the first gas outlet is located downstream of the second gas outlet in the air flow direction in the gas flow passage.

Such a configuration is preferable for stabilizing the flow rate of the fuel gas from the first gas outlet port to the gas flow path and maintaining the air-fuel mixture at an appropriate air ratio.
That is, the premixing device is generally used in such a manner that the intake side of the fan is connected to the downstream side of the gas flow passage in the air flow direction. In such a mode of use, the first gas outlet is closer to the fan than the second gas outlet. Even if the flue gas flows into the gas flow path at an unstable flow rate from the gas outlet of 2, it is possible to avoid being affected so much). As a result, it is possible to suppress variations in the amount of heat generated when the air-fuel mixture is burned.

In the present invention, preferably, the device main body includes a gas flow passage forming portion that forms the gas flow passage, and a housing portion that surrounds the gas flow passage forming portion. A supply path is formed by the housing portion and the gas flow path forming portion, and the gas supply path switching means is assembled to the apparatus main body.

Such a configuration is advantageous in terms of simplification and miniaturization of the overall configuration of the premixer. In the present invention, unlike the above configuration, for example, the gas supply path and the additional gas supply path are configured using piping members, or the gas supply path switching means is assembled to a member different from the main body of the apparatus. Although it is possible to connect it to the main body of the device with a pipe, this would make the configuration of the device as a whole complicated and large. On the other hand, according to the said structure, it is possible to avoid such a malfunction.

In the present invention, preferably, the device main body includes a first chamber communicating with the fuel gas supply port and the first gas outlet, a second chamber communicating with the second gas outlet, and the A third chamber that communicates with the exhaust gas supply port and a fourth chamber that communicates with the first to third chambers through first to third communication holes are defined, and the first , the second and fourth chambers constitute the gas supply path, the second to fourth chambers constitute the additional gas supply path, and the gas supply path switching means comprises the It includes a valve capable of individually opening and closing the first and third communication holes.

According to this configuration, the valve opens the first communication hole and closes the third communication hole, thereby causing the fuel gas to flow out from both the first and second gas outlets. be able to. Further, by closing the first communication hole and opening the third communication hole, the fuel gas and the exhaust gas can be discharged from the first and second gas outlets, respectively.
In this way, the configuration using the predetermined first to fourth chambers and the valves provided in the apparatus main body allows the gas supply path, the additional gas supply path, and the gas supply path having the functions intended by the present invention. The path switching means can be constructed appropriately.

A combustion device provided by a second aspect of the present invention comprises a fan, a premixing device provided on the intake side of the fan and for mixing air and fuel gas before sending them to the fan, and and a burner for receiving a mixture of the air and the fuel gas to burn the fuel gas, the combustion device provided by the first aspect of the present invention as the premixing device. and a part of the flue gas of the combustion gas generated by the burner is supplied to the flue gas supply port of the premixing device.

With such a configuration, the same effects as those described for the premixing device provided by the first aspect of the present invention can be obtained.

In the present invention, preferably, an exhaust gas purging operation for discharging exhaust gas remaining in the combustion device to the outside is executed after the drive combustion of the burner is finished, and the premixing is performed. During the exhaust gas purging operation, the additional gas supply path communicates with the second gas outlet, while after the exhaust gas purging operation is completed, the gas supply path is connected to the second gas outlet. It is configured to be set to communicate with two gas outlets.

According to such a configuration, the following effects are obtained.
That is, during the exhaust gas purging operation of the combustion device, the second gas outlet of the premixer is in communication with the additional gas supply path, so that the exhaust gas remaining inside the premixer is It is possible to purge to the outside of the combustion device. Further, after the exhaust gas purging operation of the combustion device is completed, the second gas outlet of the premixing device is switched to a state in which it communicates with the gas supply path. Water vapor is also appropriately prevented from entering the premixer through the exhaust gas inlet of the premixer. If water vapor or exhaust gas enters the premixing device, the water vapor or exhaust gas may flow back to the fuel gas supply port side if the exhaust side of the combustion device receives a strong wind and a back pressure is generated in the combustion device. However, according to the above configuration, there is no such fear.

The water heater provided by the third aspect of the present invention includes the combustion device provided by the second aspect of the present invention, and sensible heat and latent heat are respectively recovered from the combustion gas of the combustion device to heat hot water. a primary heat exchanger and a secondary heat exchanger capable of It is characterized in that the exhaust gas after passing through the vessel is utilized.

According to such a configuration, the following effects are obtained.
That is, the exhaust gas after passing through the secondary heat exchanger of the water heater has a lower temperature and a lower water vapor content than other exhaust gases generated in the water heater. Therefore, when the exhaust gas is returned to the premixing device for use, it is necessary to prevent problems such as abnormally high temperatures at the locations where the exhaust gas comes in contact with, and excessive condensation at the locations. It is possible.

Other features and advantages of the present invention will become clearer from the following description of embodiments of the invention with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic explanatory drawing which shows an example of the hot water apparatus provided with the premixing apparatus which concerns on this invention. FIG. 2 is an explanatory view schematically showing the schematic configuration of the premixing device of FIG. 1; FIG. 2 is an external perspective view of the premixing device of FIG. 1; (a) is a cross-sectional view taken along IVa-IVa in FIG. 3, and (b) is an explanatory view of the operation at the time of valve switching in the configuration shown in (a). FIG. 4B is a cross-sectional view taken along the line VV of FIG. 4(a); (a) is a cross-sectional view showing another example of the present invention, and (b) is an explanatory view of the operation at the time of valve switching in the configuration shown in (a).

Preferred embodiments of the present invention will be specifically described below with reference to the drawings.

FIG. 1 shows a premixing device A, a combustion device B (premixed combustion device) configured by combining the premixing device A with a fan 1 and a burner 2, and primary heat exchangers 11a and 2 in the combustion device B. A water heater WH configured by combining secondary heat exchangers 11b is shown.

Details of the premixing device A will be described later, but the premixing device A is used to generate a mixed gas (combustible mixed gas) of air and fuel gas, and this mixed gas passes through the fan 1. supplied to the burner 2. The burner 2 includes a perforated plate 21 having a plurality of vent holes 20 and is housed within the case 10 . The burner 2 is provided with an ignition plug, a flame detection sensor, and the like (not shown). The mixed gas passes through a plurality of vent holes 20 and burns below the perforated plate 21 . The combustion gas generated by the burner 2 sequentially acts on the primary heat exchanger 11a for sensible heat recovery and the secondary heat exchanger 11b for latent heat recovery. Hot water passing through the inside of the vessel 11b is heated. Hot water is generated by this, and this hot water is supplied to a desired hot water supply destination. Exhaust gas of the combustion gas that has passed through the primary heat exchanger 11a and the secondary heat exchanger 11b passes through the exhaust duct 12 and is discharged to the outside.
The water heater WH includes a control section 13 configured using a microcomputer or the like. This control section 13 also controls the valves V1 and V2 of the premixer A as described later.

The premixer A includes an apparatus main body A0 and a pair of valves V1 and V2 assembled to the apparatus main body A0.

As shown well in FIGS. 3 to 5, the apparatus main body A0 includes a cylindrical gas flow passage forming portion 3 that forms a venturi-shaped gas flow passage 30 therein, and a flange that surrounds the cylindrical gas flow passage forming portion 3. 43 , a housing portion 4 having a fuel gas supply port 44 and an exhaust gas supply port 45 .

As shown in FIG. 1, fuel gas is supplied to the fuel gas supply port 44 from a fuel gas supply unit such as a gas pipe through a pressure equalizing valve (zero governor) V3. Exhaust gas after passing through the secondary heat exchanger 11b of the water heater WH is supplied to the exhaust gas supply port 45 via the pipe portion 19 . In addition, the halftone dot portion in FIG. 4 indicates the exhaust gas supply point.

First and second gas outlet openings facing the gas flow passage 30 are provided in the portion of the gas flow passage forming portion 3 (the inner peripheral wall of the gas flow passage 30) where the inner diameter is partially reduced. 31, 32 are provided.
The device main body A0 is directly connected to the intake side of the fan 1 using the flange portion 43, or is connected to a pipe. When the fan 1 is driven, external air flows into the gas flow passage 30 from one end side opening 30a and flows toward the other end side opening 30b. As will be described later, the fuel gas flows into the gas flow passage 30 from the first gas outlet 31 due to the negative pressure effect generated by this air flow. Fuel gas or exhaust gas flows out from the second gas outlet 32 . As a result of this action, a mixture of air and fuel gas or a mixture of this with exhaust gas is generated and drawn into the fan 1 .

The first gas outlet 31 is located downstream of the second gas outlet 32 in the air flow direction in the gas flow passage 30 . This configuration is preferable for stabilizing the flow rate of the fuel gas from the first gas outlet port 31 to the gas flow path 30 . This is because the first gas outflow port 31 is closer to the fan 1 than the second gas outflow port 32, so compared with the second gas outflow port 32, the suction negative pressure can be stabilized, and the second gas outflow port 32 is closer to the fan 1. This is because even if the exhaust gas flows out from the gas outlet port 32 into the gas flow passage 30 at an unstable flow rate, it is possible to avoid the influence of the flue gas.

The housing portion 4 is a portion positioned around the gas flow path forming portion 3 . Specifically, the housing portion 4 includes a main housing portion 40 having the fuel gas supply port 44 and the exhaust gas supply port 45, and a plate-like partition wall portion attached to the peripheral wall portion of the main housing portion 40. 41 and an auxiliary housing portion 42 attached to the partition wall portion 41 are combined.

The apparatus main body A0 forms first to fourth chambers C1 to C4 shown in FIG.
Here, each of the first to third chambers C1 to C3 has a pair of annular partitions in which the gap between the main housing portion 40 and the gas flow passage forming portion 3 is provided in the gas flow passage forming portion 3. It is a portion defined by the wall portion 38 and arranged in order from the downstream side to the upstream side in the air flow direction of the gas flow passage 30 . The first chamber C<b>1 communicates with the fuel gas supply port 44 and the first gas outlet 31 . The second chamber C2 communicates with the second gas outlet 32 . The third chamber C3 communicates with the exhaust gas supply port 45 .
The fourth chamber C<b>4 is a portion surrounded by the auxiliary housing portion 42 and the partition wall portion 41 . The partition wall portion 41 is provided with first to third communication holes 61 to 63 for communicating the fourth chamber C4 with the first to third chambers C1 to C3, respectively.

The pair of valves V1 and V2 correspond to a specific example of the "gas supply path switching means" according to the invention, and are attached to the auxiliary housing portion 42. As shown in FIG. These valves V1 and V2 are electromagnetic valves, for example, and allow the valve bodies 5 arranged opposite to the first and third communication holes 61 and 63 to reciprocate by using electromagnetic force.

FIG. 4(a) shows a case where the first communication hole 61 is opened and the third communication hole 63 is closed by the valves V1 and V2. In this case, the fuel gas supplied to the fuel gas supply port 44 can flow out from both the first and second gas flow outlets 31 and 32 to the gas flow path 30 . The first, second and fourth chambers C1, C2 and C4 guide the fuel gas supplied to the fuel gas supply port 44 to the first and second gas outlets 31 and 32 to the gas flow path 30. It constitutes a gas supply route R1 that allows the gas to flow out. The state of FIG. 4A is a state in which the gas supply path R1 communicates with the second gas outlet 32. FIG.

On the other hand, in FIG. 4B, the operating states of the valves V1 and V2 are switched to a state different from that in FIG. indicates the case. In this case, the fuel gas can flow out from the first gas outlet 31 and the exhaust gas can flow out from the second gas outlet 32 to the gas flow passage 30 . In this case, the second to fourth chambers C2 to C4 provide an additional gas supply path that guides the exhaust gas supplied to the exhaust gas supply port 45 to the second gas outlet 32 and allows it to flow out to the gas flow passage 30. constitutes R2. The state of FIG. 4B is a state in which the additional gas supply route R2 communicates with the second gas outlet 32. FIG.

The premixing device A has a basic configuration as shown in FIG. 2 when simplified and schematically shown. That is, by switching the valves V1 and V2, the gas supply path R1 communicates with the second gas outlet 32, and the fuel gas can flow out from both the first and second gas outlets 31 and 32 (Fig. 4(a)), the additional gas supply path R2 communicates with the second gas outlet 32, and the fuel gas and the exhaust gas can flow out from the first and second gas outlets 31, 32, respectively. Either one of the states (the state of FIG. 4(b)) can be selectively set.

The control unit 13 can execute operation control of each unit of the water heater WH and various data processing. During normal combustion, the valves V1 and V2 are controlled so as to set the state shown in FIG. 4(b). The control unit 13 also controls an exhaust gas purge operation, which will be described later.

Next, the operation of the premixing device A, the combustion device B, and the water heating device WH will be described.

First, when fuel ignition is performed in the burner 2 of the combustion device B, the premixing device A is set to the state shown in FIG. As a result, the fuel gas flowing out from both the first and second gas outlets 31 and 32 can be mixed with the air flowing through the gas flow passage 30 . Therefore, the air-fuel mixture can be made to have a fuel-rich air ratio and a small ignition energy, and the ignition performance can be improved.

Then, when fuel ignition is completed and the burner 2 is in normal combustion mode, the premixer A is switched to the state shown in FIG. 4(b). As a result, the fuel gas flowing out from the first gas outlet 31 and the exhaust gas flowing out from the second gas outlet 32 can be mixed with the air flowing through the gas flow passage 30 . Therefore, it is possible to lower the combustion temperature in the burner 2 and appropriately reduce NOx by means of exhaust gas recirculation (EGR). Thus, according to the present embodiment, both reduction in NOx and improvement in ignition performance are appropriately achieved.

In this embodiment, the exhaust gas after passing through the secondary heat exchanger 11b is used as the exhaust gas. It is lower and has a lower water vapor content. Therefore, when the exhaust gas is sent to the premixing device A, the premixing device A does not reach an abnormally high temperature or dew condensation occurs.

After the drive combustion of the burner 2 is finished, an exhaust gas purging operation is performed to exhaust the exhaust gas remaining inside the case 10 and the exhaust duct 12 to the outside. This exhaust gas purging operation is executed by continuously operating the fan 1. At this time, the premixing device A is in the state shown in FIG. 4(b). As a result, the exhaust gas remaining inside the premixer A can also be purged to the outside.

After completion of the exhaust gas purging operation, the premixing device A is in the state shown in FIG. 4(a). As a result, even if water vapor exists inside the case 10 or the exhaust duct 12, the water vapor can be prevented from entering the premixing device A through the exhaust gas supply port 45. FIG.

As described above, the premixing device A of the present embodiment has a configuration as shown in FIG. 2 when simplified and schematically shown. However, the premixing device A itself is not provided with a piping portion connecting the valves V1 and V2, and the first to fourth chambers C1 to C4 provided in the device main body A0 are connected to the gas supply path. It constitutes R1 and an additional gas supply path R2. Therefore, the overall configuration of the premixer A is rational, simple and compact. As a result, it is possible to appropriately reduce the manufacturing cost of the premixer A and improve the convenience in handling.

FIG. 6 shows another embodiment of the invention. In the figure, elements identical or similar to those in the above embodiment are denoted by the same reference numerals as in the above embodiment, and repeated explanations are omitted.

A premixing device Aa shown in FIG. The pair of first gas outlets 31a and 31b are arranged to face each other with the center of the gas flow passage 30 interposed therebetween. Further, the premixing device Aa is provided with a partition wall portion 7 and flappers 71 and 72 . The partition wall portion 7 is positioned between the first gas outlets 31a and 31b, and divides the gas flow path 30 into a region Sa closer to the first gas outlet 31a and a region Sa closer to the first gas outlet 31b. Sb. The flappers 71 and 72 rotate around the shaft portions 71 a and 72 a so as to open and close the region Sb of the gas flow passage 30 according to the air flow rate of the gas flow passage 30 . When the air flow rate is small, the opening degrees of the flappers 71 and 72 are small, narrowing the area Sb. Therefore, it is possible to suppress a decrease in the flow velocity of the air and allow an appropriate amount of fuel gas to flow out from the first gas outlet 31b.
For this reason, the premixing device Aa of the present embodiment is preferable for increasing the turndown ratio.

The invention is not limited to the content of the embodiments described above. The specific configuration of each part of the premixing device, the combustion device, and the water heating device according to the present invention can be changed in various ways within the intended scope of the present invention.

In the above-described embodiment, the apparatus main body A0 is provided with the first to fourth chambers C1 to C4, which constitute the predetermined gas supply route R1 and the additional gas supply route R2. is not limited to this. The gas supply route R1 and the additional gas supply route R2 can also be configured using means other than the chamber (for example, using a piping member, or forming a hole serving as a piping member in the main body of the apparatus). configuration such as setting up).
The gas supply path switching means of the present invention is not limited to two electromagnetic valves. For example, in FIG. 2, it is possible to replace the two valves V1 and V2 with one three-way valve.

The fuel gas is, for example, natural gas or LP gas, but its specific type does not matter. The exhaust gas is preferably exhaust gas after passing through the secondary heat exchanger, but is not limited to this.
The combustion apparatus according to the present invention is not limited to use in hot water systems, but may also be used in other applications such as heating or incineration. Further, the type is not limited to the type in which the combustion gas travels downward, and a type in which the combustion gas travels upward, for example, may be used.
The water heater according to the present invention is not limited to general hot water supply, and can be used for hot water heating, for example.

A, Aa Premixing device A0 Apparatus main body B Combustion devices C1 to C4 First to fourth chambers R1 Gas supply route R2 Additional gas supply routes V1, V2 Valves (gas supply route switching means)
WH Water heater 1 Fan 2 Burner 11a Primary heat exchanger 11b Secondary heat exchanger 3 Gas flow passage forming portion 30 Gas flow passages 31, 32 First and second gas outlets 4 Housing portion 44 Fuel gas supply port 45 Exhaust gas supply port

Claims (7)

an apparatus main body having a gas flow path for circulating air in a predetermined direction and first and second gas outlets communicating with the gas flow path;
a gas supply path having a fuel gas supply port at one end and guiding the fuel gas supplied to the fuel gas supply port to the first and second gas outlets so that it can flow out to the gas flow path;
A premixing device comprising:
an additional gas supply path having an exhaust gas supply port at one end and guiding the exhaust gas supplied to the exhaust gas supply port to the second gas outlet so that it can flow out to the gas flow passage;
gas supply path switching means capable of selectively connecting one of the gas supply path and the additional gas supply path to the second gas outlet;
A premixing device, further comprising: A premixing device according to claim 1,
The premixing device, wherein the first gas outlet is located downstream of the second gas outlet in the air flow direction in the gas flow passage. The premixing device according to claim 1 or 2,
The apparatus main body includes a gas flow passage forming portion forming the gas flow passage, and a housing portion surrounding the gas flow passage forming portion, and the gas supply passage and the additional gas supply passage are connected to the housing portion. and the gas flow path forming portion,
The premixing device, wherein the gas supply path switching means is attached to the device main body. A premixing device according to claim 3,
The apparatus body includes a first chamber communicating with the fuel gas supply port and the first gas outlet, a second chamber communicating with the second gas outlet, and a second chamber communicating with the exhaust gas supply port. 3 chambers and a fourth chamber communicating with each of the first to third chambers through first to third communication holes,
The first, second and fourth chambers constitute the gas supply path, and the second to fourth chambers constitute the additional gas supply path,
The premixing device, wherein the gas supply path switching means includes valves capable of individually opening and closing the first and third communication holes. with a fan
a premixing device provided on the intake side of the fan for mixing air and fuel gas and then feeding the mixture to the fan;
a burner for receiving a mixture of the air and the fuel gas supplied from the fan and burning the fuel gas;
A combustion device comprising
The premixing device according to any one of claims 1 to 4 is used as the premixing device, and part of the exhaust gas of the combustion gas generated by the burner is supplied to the exhaust gas supply port of the premixing device. Combustion device, characterized in that it is adapted to be fed. A combustion device according to claim 5, wherein
After the drive combustion of the burner is completed, an exhaust gas purging operation is performed for discharging the exhaust gas remaining in the combustion device to the outside,
In the premixing device, the additional gas supply path communicates with the second gas outlet during the exhaust gas purging operation. is set to communicate with the second gas outlet. A combustion device according to claim 5 or 6;
a primary heat exchanger and a secondary heat exchanger capable of respectively recovering sensible heat and latent heat from the combustion gas of the combustion apparatus to heat hot water;
A water heater comprising
A water heater, wherein the exhaust gas after passing through the secondary heat exchanger is used as the exhaust gas supplied to the exhaust gas supply port of the premixer.

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