Combustion device and gas water heater

Abstract

The utility model relates to the technical field of gas water heaters, in particular to a combustion device and a gas water heater. The combustion device comprises a combustion chamber, a combustor, a flow limiting plate and a gas distribution pipe assembly, the combustor is installed in the combustion chamber, a shell of the combustor divides the combustion chamber into a combustion cavity and an air inlet cavity which are communicated, and a plurality of injection holes are formed in the side, close to the gas distribution pipe assembly, of the shell of the combustor. The gas distribution pipe assembly comprises a gas distribution pipe installed in the combustion chamber, and the gas distribution pipe is right opposite to the multiple injection holes and used for distributing fuel gas to the multiple injection holes. And an openable and closable injection gap is formed between the gas distribution pipe and the side wall with the injection hole in the shell. The gas water heater comprises the combustion device, so that the gas water heater can be suitable for a hydrogen-rich gas source and a pure hydrogen gas source, and the applicability of the gas water heater is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of gas water heaters, in particular to a combustion device and a gas water heater. Background Art

[0002] In gas water heaters, with the widespread application of natural gas hydrogen-blended combustion technology, hydrogen is blended into natural gas to achieve mixed combustion of natural gas and hydrogen, improve combustion efficiency, and achieve clean combustion.

[0003] At present, when a small amount of hydrogen is mixed into natural gas (the volume ratio of hydrogen is generally within 30%), primary air is provided through the primary air injection structure of the burner, and secondary air is supplied to assist combustion during the combustion process. When the gas source is pure hydrogen, due to the characteristics of hydrogen such as low ignition energy, easy ignition, and high combustion speed, the propagation speed of the premixed combustion flame is very high, and the combustion is prone to flashback during low-load operation, resulting in combustion problems such as deflagration and detonation. Therefore, the existing combustion device is only applicable to a single gas source (natural gas or natural gas mixed with a small amount of hydrogen), and has poor applicability. Utility Model Content

[0004] One of the technical problems solved by the utility model is to provide a combustion device, which can effectively solve the technical problem that the combustion device in the prior art is only applicable to a single gas source and has poor applicability.

[0005] The second technical problem solved by the present invention is to provide a gas water heater, which can effectively solve the technical problem that the gas water heater in the prior art is only applicable to a single gas source and has poor applicability.

[0006] The first technical problem mentioned above is solved by the following technical solution:

[0007] A combustion device, comprising a combustion chamber, a burner and an air distribution pipe assembly, wherein the burner is installed in the combustion chamber, and a shell of the burner is provided with a plurality of injection holes on one side close to the air distribution pipe assembly;

[0008] The gas distribution pipe assembly includes a gas distribution pipe installed in the combustion chamber, the gas distribution pipe is arranged opposite to the multiple injection holes and is used to distribute fuel gas to the multiple injection holes; an openable and closable injection gap is formed between the gas distribution pipe and the side wall of the shell with the injection holes.

[0009] Compared with the background technology, the combustion device described in the utility model has the following beneficial effects:

[0010] In the combustion device, when the gas source is hydrogen-rich (when the amount of hydrogen blended in natural gas is high), the ejector gap is opened to make the primary air supply channel conductive and effectively control the primary air supply amount, avoiding flashback during hydrogen-rich combustion and causing combustion problems such as deflagration and detonation, thereby improving the stability of hydrogen-rich combustion. When the gas source is pure hydrogen, the ejector gap is closed, the primary air supply channel is closed, and hydrogen is directly premixed with air at the fire hole of the burner's fire row for combustion, avoiding flashback during pure hydrogen combustion and causing combustion problems such as deflagration and detonation, thereby improving the stability of pure hydrogen combustion, making the combustion device applicable to both hydrogen-rich and pure hydrogen gas sources, thereby improving the applicability of the combustion device.

[0011] In one of the embodiments, the combustion device further comprises a sealing gasket, which can be selectively installed in the ejection gap to seal or removed from the ejection gap.

[0012] In one of the embodiments, the sealing gasket is clamped between the side wall of the shell having the ejection hole and the gas distribution pipe, and the sealing gasket is provided with avoidance holes, which are connected to the ejection holes in a one-to-one correspondence.

[0013] In one embodiment, the shell includes a front plate, the front plate includes a first part and a second part connected in a stepped structure, and the second part is located on the rear side of the first part, the second part is provided with the injection hole, the bottom of the air distribution pipe abuts against the step surface between the first part and the second part, and the outer side surface of the air distribution pipe and the second part forms the injection gap.

[0014] In one of the embodiments, first limiting flanges are extended on both sides of the second portion along the length direction, and the two first limiting flanges are respectively abutted against the left and right ends of the gas distribution pipe so that the injection gap has an upwardly disposed inlet.

[0015] In one of the embodiments, the air distribution pipe is downwardly extended to be provided with an ear plate, and the ear plate is attached to and installed on the outer side surface of the second part through fasteners.

[0016] In one of the embodiments, the width of the ejection gap along the front-to-back direction is 2 mm to 5 mm.

[0017] The above second technical problem is solved by the following technical solution:

[0018] A gas water heater comprises a shell assembly and a heat exchanger. The gas water heater also comprises the above-mentioned combustion device. The combustion device and the heat exchanger are both installed in the shell assembly.

[0019] Compared with the background technology, the gas water heater of the utility model has the following beneficial effects:

[0020] By using the above-mentioned combustion device, the gas water heater can avoid backfire during the combustion of hydrogen-rich or pure hydrogen, which may lead to combustion problems such as deflagration and detonation, so that both gas sources can burn stably in the combustion device, making the gas water heater applicable to both hydrogen-rich and pure hydrogen gas sources, thereby improving the applicability of the gas water heater.

[0021] In one of the embodiments, the combustion device is located above the heat exchanger, and the lower end of the combustion chamber is sealed and connected to the top opening of the heat exchanger.

[0022] In one of the embodiments, the gas water heater further includes a smoke collecting hood and a water collecting box, the bottom opening of the heat exchanger is sealed and connected to the top of the smoke collecting hood, a water collecting hole is provided at the bottom of the smoke collecting hood, and the water collecting box is provided below the smoke collecting hood and is sealed and connected to the smoke collecting hood through the water collecting hole. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the internal structure of the gas water heater provided by the embodiment of the utility model;

[0024] Figure 2 It is a schematic diagram of the assembly structure of the combustion device and the fan assembly provided in the embodiment of the utility model;

[0025] Figure 3 is a cross-sectional view of a combustion device provided by an embodiment of the utility model;

[0026] Figure 4 It is a schematic diagram of the assembly structure of the burner and the flow limiting plate provided in the embodiment of the utility model;

[0027] Figure 5 It is a schematic diagram of the structural decomposition of a burner, a flow limiting plate and a sealing gasket provided in an embodiment of the utility model.

[0028] The names and numbers of the components in the figure are as follows:

[0029] 1. Combustion device; 11. Combustion chamber; 110. Air inlet cavity; 12. Burner; 120. Combustion cavity; 121. Front plate; 1211. First part; 1212. Second part; 12121. Injection hole; 12122. First limit flange; 1213. Third part; 12131. Through hole; 12132. Second limit flange; 122. Back plate; 123. Fire grate; 13. Current limiting plate; 131. Ventilation hole; 14. Air distribution pipe assembly; 140. Injection gap; 141. Air distribution pipe; 1411. Ear plate; 15. Sealing pad; 151. Avoidance hole;

[0030] 2. Shell assembly; 3. Heat exchanger; 4. Smoke hood; 5. Water collecting box; 6. Air inlet pipe; 7. Fan assembly; 8. Smoke exhaust pipe; 9. Water outlet pipe. DETAILED DESCRIPTION

[0031] In order to make the technical problems solved by the present invention, the technical solutions adopted and the technical effects achieved clearer, the technical solutions of the present invention are further described below in conjunction with the accompanying drawings and through specific implementation methods. It is understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for the convenience of description, only the parts related to the present invention are shown in the accompanying drawings, rather than all of them.

[0032] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] In the present utility model, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0034] In the description of this embodiment, the terms "upper", "lower", "right", "left" and other directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for the convenience of description and simplified operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0035] The technical solution of the utility model is further explained below with reference to the accompanying drawings and through specific implementation methods.

[0036] like Figure 1As shown, this embodiment provides a gas water heater, which includes a combustion device 1, a shell assembly 2 and a heat exchanger 3, wherein the combustion device 1 and the heat exchanger 3 are both installed in the shell assembly 2. The existing gas source is mostly natural gas or natural gas mixed with a small amount of hydrogen. The high-temperature flue gas generated by the combustion of the gas source in the combustion device 1 heats the water in the heat exchange tube of the heat exchanger 3, so that the gas water heater can stably output hot water.

[0037] When the gas source is rich hydrogen or pure hydrogen, after combustion, the surface of the heat exchanger 3 and the combustion chamber 11 (such as Figure 2 A large amount of condensed water is generated on the inner wall of the housing assembly 2 (as shown). In order to prevent the condensed water from affecting the normal use of the combustion device 1 and to prevent the condensed water from corroding the various components in the housing assembly 2, the combustion device 1 of this embodiment is located above the heat exchanger 3, and the lower end of the combustion chamber 11 is sealed and connected to the top opening of the heat exchanger 3. By adopting the installation structure of the upper burner 12 and the lower heat exchanger 3, it is ensured that the gas water heater is not affected by condensed water when burning rich hydrogen or pure hydrogen.

[0038] Specifically, Figure 1 and Figure 2 As shown, the gas water heater also includes a smoke hood 4, a water collecting box 5, an air inlet pipe 6, a fan assembly 7, a smoke exhaust pipe 8 and a water outlet pipe 9. The combustion device 1 includes a combustion chamber 11, a burner 12 and a gas distribution pipe assembly 14, and the burner 12 is installed in the combustion chamber 11. The air inlet pipe 6 is connected to the gas distribution pipe assembly 14, and the gas distribution pipe assembly 14 guides the natural gas, hydrogen-rich or pure hydrogen in the air inlet pipe 6 to the burner 12 for combustion to generate high-temperature flue gas. The fan assembly 7 is installed on the top of the combustion chamber 11 to transport combustion-supporting air to the burner 12 in the combustion chamber 11. The bottom opening of the heat exchanger 3 is sealed and connected to the top of the smoke hood 4, and the upper end of the smoke hood 4 is connected to the smoke exhaust pipe 8 to discharge the smoke passing through the heat exchanger 3 from the housing assembly 2 through the smoke exhaust pipe 8. Cold water enters the heat exchanger 3 through the water inlet pipe to complete heat exchange and temperature rise, and then flows out from the water outlet pipe 9. A water collecting hole is provided at the bottom of the smoke collecting hood 4, and the water collecting box 5 is provided below the smoke collecting hood 4 and is sealed and connected to the smoke collecting hood 4 through the water collecting hole. Condensed water generated during the combustion of rich hydrogen or pure hydrogen flows into the smoke collecting hood 4 through the heat exchanger 3, and is finally collected into the water collecting box 5 through the water collecting hole for unified discharge. In addition, after the condensed water enters the water collecting box 5, it acts as a water seal to prevent the smoke in the smoke collecting hood 4 from leaking out of the water collecting box 5.

[0039] When a small amount of hydrogen is mixed into natural gas, the primary air injection structure of the existing burner provides primary air, and secondary air is supplied to assist combustion during the combustion process. When the gas source is pure hydrogen, due to the characteristics of hydrogen such as low ignition energy, easy ignition, and high combustion speed, the premixed combustion flame propagation speed is very high, and the combustion is prone to flashback during low-load operation, resulting in combustion problems such as deflagration and detonation. Therefore, the existing combustion device is only suitable for a single gas source and has poor applicability.

[0040] To solve the above problems, Figure 3 to Figure 5 As shown, the shell of the burner 12 divides the combustion chamber 11 into a combustion chamber 120 and an air inlet chamber 110 that are connected to each other. A plurality of ejection holes 12121 are provided on one side of the shell of the burner 12 close to the gas distribution pipe assembly 14, and a plurality of ventilation holes 131 are provided on the same side of the air inlet chamber 110. The gas distribution pipe assembly 14 includes a gas distribution pipe 141 installed in the combustion chamber 11, and the gas distribution pipe 141 is arranged opposite to the plurality of ejection holes 12121 and is used to distribute gas to the plurality of ejection holes 12121. It should be noted that a plurality of gas outlet nozzles are arranged in the gas distribution pipe 141, and the plurality of gas outlet nozzles are arranged opposite to the plurality of ejection holes 12121 one by one. An ejection gap 140 that can be opened and closed is formed between the gas distribution pipe 141 and the side wall of the shell having the ejection holes 12121, and when the ejection gap 140 is opened, the air inlet chamber 110, the ventilation holes 131, the ejection gap 140 and the combustion chamber 120 are connected in sequence.

[0041] In the combustion device 1, the air inlet chamber 110, the air vent 131, the opened ejection gap 140 and the combustion chamber 120 are connected in sequence to form a supply channel for providing primary air. When the gas source is hydrogen-rich, the ejection gap 140 is opened to make the supply channel conductive and effectively control the supply amount of primary air, thereby avoiding flashback during hydrogen-rich combustion and causing combustion problems such as deflagration and detonation, and improving the stability of hydrogen-rich combustion. When the gas source is pure hydrogen, the ejection gap 140 is closed, the supply channel is closed, and the hydrogen is directly premixed with the air at the fire hole of the fire row 123 of the burner 12 to burn, thereby avoiding flashback during pure hydrogen combustion and causing combustion problems such as deflagration and detonation, and improving the stability of pure hydrogen combustion, so that the combustion device 1 can be used for both hydrogen-rich and pure hydrogen gas sources, thereby improving the applicability of the combustion device 1.

[0042] Specifically, the combustion device 1 further includes a flow limiting plate 13, and the supply channel effectively controls the supply amount of primary air under the action of the air holes 131 of the flow limiting plate 13. The shell of the burner 12 is surrounded by a front plate 121 and a rear plate 122, and the front plate 121, the flow limiting plate 13 and the top plate of the combustion chamber 11 form an air inlet cavity 110. The front plate 121 of the burner 12 also forms a combustion cavity 120 with a fire grate 123 installed with the rear plate 122 of the burner 12, and the front plate 121 is provided with a through hole 12131, and the air inlet cavity 110 is connected to the combustion cavity 120 through the through hole 12131. The gas distribution pipe 141 of the gas distribution pipe assembly 14 is located in the combustion chamber 11 and is installed on the portion of the front plate 121 having the ejection hole 12121, and an ejection gap 140 that can be opened and closed is formed between the gas distribution pipe 141 and the front plate 121. The ejection gap 140 is connected to the ejection channel of the corresponding fire row 123 in the combustion chamber 120 through the ejection hole 12121. The flow limiting plate 13 is provided with a vent hole 131 for limiting the air flow, and the air inlet chamber 110 is connected to the opened ejection gap 140 through the vent hole 131.

[0043] like Figure 3 and Figure 4 As shown, the front plate 121 includes a first portion 1211 and a second portion 1212 connected in a stepped structure, and the second portion 1212 is located at the rear side of the first portion 1211, and the second portion 1212 is provided with an injection hole 12121. The bottom of the gas distribution pipe 141 abuts against the stepped surface between the first portion 1211 and the second portion 1212, and the outer side surface of the gas distribution pipe 141 and the second portion 1212 surrounds the injection gap 140. When the gas distribution pipe 141 is installed on the second portion 1212, the nozzle of the gas distribution pipe 141 is arranged one by one opposite to the injection hole 12121 of the second portion 1212, so that the rich hydrogen or pure hydrogen in the intake pipe 6 is uniformly injected into the combustion chamber 120 through the multiple injection holes 12121, and is uniformly burned at the fire hole of the fire row 123 located in the combustion chamber 120.

[0044] It should be noted that the top of the second part 1212 is horizontally extended backward to be provided with a third part 1213, and the third part 1213 is a flat plate structure and is evenly provided with through holes 12131. The rear side and the left and right sides of the third part 1213 are bent upward to form three second limiting flanges 12132, and the limiting plate 13 and the three second limiting flanges 12132 form a semi-enclosed structure, and the semi-enclosed structure and the top plate of the combustion chamber 11 form an air inlet cavity 110. After the fan assembly 7 delivers air to the air inlet cavity 110, most of the air enters the combustion cavity 120 through the through hole 12131, and a small amount of air enters the ejection gap 140 through the air hole 131 of the limiting plate 13. When the gas source is rich in hydrogen, the ejection gap 140 is opened to make the supply channel conductive. When the gas source is pure hydrogen, the ejection gap 140 is closed and the supply channel is disconnected.

[0045] like Figure 3 and Figure 4 As shown, the second portion 1212 is provided with first limiting flanges 12122 extending on both sides along the length direction. The two first limiting flanges 12122 are respectively in contact with the left and right ends of the air distribution pipe 141, so that the ejection gap 140 has an entrance facing upward. The two first limiting flanges 12122 play a limiting and guiding role in the assembly of the air distribution pipe 141, avoiding the misalignment of the air distribution pipe 141, and improving the installation efficiency and installation accuracy of the air distribution pipe 141. At the same time, the two air distribution pipes 141 block the left and right sides of the ejection gap 140, so that the entrance of the ejection gap 140 faces upward and is close to the flow limiting plate 13, so as to ensure that the primary air quickly passes through the entrance and enters the ejection gap 140.

[0046] Specifically, Figure 5 As shown, the air distribution pipe 141 is provided with an ear plate 1411 extending downward, and the ear plate 1411 is attached to and installed on the outer side of the front plate 121 through fasteners. Specifically, the air distribution pipe 141 is threadedly connected to the second portion 1212 of the front plate 121 through the ear plate 1411, so that the air distribution pipe 141 can be detachably assembled, the disassembly and assembly efficiency of the air distribution pipe 141 is improved, and the opening and closing control of the injection gap 140 is facilitated.

[0047] It should be noted that when the gas source is hydrogen-rich, it is necessary to reduce the supply of primary air to avoid flashback during hydrogen-rich combustion and combustion problems such as deflagration and detonation, thereby improving the stability of hydrogen-rich combustion. A plurality of air holes 131 are evenly arranged on the limiting plate 13 to adjust the supply of primary air. At the same time, the width H of the ejection gap 140 in the front-to-back direction of this embodiment is 2mm to 5mm to minimize the volume of the ejection gap 140, thereby controlling the supply of primary air. The width H of the ejection gap 140 in the front-to-back direction of this embodiment can be 2mm, 3mm, 4mm or 5mm, etc. Compared with the width of the ejection gap of about 10mm when the gas source is natural gas, the volume of the ejection gap 140 in this embodiment is smaller, reducing the supply of primary air.

[0048] like Figure 5As shown, the combustion device 1 also includes a sealing gasket 15, which can be selectively installed in the ejection gap 140 or removed from the ejection gap 140. When the gas source is rich in hydrogen, there is no need to install the sealing gasket 15, and the ejection gap 140 remains open to allow the supply channel to be connected and realize a primary air supply. When the gas source is pure hydrogen, the sealing gasket 15 is installed in the ejection gap 140, and the ejection gap 140 is closed, so that the supply channel is disconnected and the primary air supply is eliminated. Through the selective installation of the sealing gasket 15, the rapid opening and closing of the ejection gap 140 is achieved, so that the combustion device 1 can be used for both hydrogen-rich and pure hydrogen gas sources, thereby improving the applicability of the combustion device 1. Specifically, the sealing gasket 15 is clamped and installed between the second part 1212 of the front plate 121 and the gas distribution pipe 141, without the need to use additional fasteners such as bolts, which simplifies the disassembly and assembly operation of the sealing gasket 15 and improves the disassembly and assembly efficiency of the sealing gasket 15.

[0049] like Figure 5 As shown, the sealing gasket 15 is provided with an avoidance hole 151, and the sealing gasket 15 is clamped between the side wall of the shell with the injection hole 12121 (i.e., the second part 1212 of the front plate 121) and the gas distribution pipe 141, and the avoidance hole 151 is connected with the injection hole 12121 in a one-to-one correspondence, so that when the injection gap 140 is closed, the nozzle of the gas distribution pipe 141 injects rich hydrogen or pure hydrogen into the combustion chamber 120 through the connected avoidance hole 151 and the injection hole 12121, thereby ensuring the normal operation of the combustion chamber 11.

[0050] The above embodiments are only to illustrate the basic principles and characteristics of the present invention. The present invention is not limited by the above embodiments. Without departing from the spirit and scope of the present invention, the present invention may be subject to various changes and modifications, which are within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A combustion device, characterized in that: It comprises a combustion chamber (11), a burner (12) and an air distribution pipe assembly (14); the burner (12) is installed in the combustion chamber (11); a shell of the burner (12) is provided with a plurality of injection holes (12121) on one side close to the air distribution pipe assembly (14); The gas distribution pipe assembly (14) comprises a gas distribution pipe (141) installed in the combustion chamber (11); the gas distribution pipe (141) is arranged opposite to the multiple injection holes (12121) and is used to distribute fuel gas to the multiple injection holes (12121); an openable and closable injection gap (140) is formed between the gas distribution pipe (141) and the side wall of the shell having the injection holes (12121).

2. The combustion device according to claim 1, characterized in that: The combustion device (1) further comprises a sealing gasket (15), wherein the sealing gasket (15) can be selectively installed in the ejection gap (140) to seal or removed from the ejection gap (140).

3. The combustion device according to claim 2, characterized in that: The sealing gasket (15) is sandwiched between the side wall of the shell having the ejection hole (12121) and the gas distribution pipe (141), and the sealing gasket (15) is provided with an avoidance hole (151), and the avoidance hole (151) is connected to the ejection hole (12121) in a one-to-one correspondence.

4. The combustion device according to claim 1, characterized in that: The shell includes a front plate (121), the front plate (121) includes a first part (1211) and a second part (1212) connected in a stepped structure, and the second part (1212) is located on the rear side of the first part (1211), the second part (1212) is provided with the injection hole (12121), the bottom of the gas distribution pipe (141) is in contact with the stepped surface between the first part (1211) and the second part (1212), and the outer side surfaces of the gas distribution pipe (141) and the second part (1212) form the injection gap (140).

5. The combustion device according to claim 4, characterized in that: The second portion (1212) is provided with first limiting flanges (12122) extending on both sides along the length direction, and the two first limiting flanges (12122) are respectively abutted against the left and right ends of the gas distribution pipe (141) so that the injection gap (140) has an upwardly arranged entrance.

6. The combustion device according to claim 4, characterized in that: The gas distribution pipe (141) is provided with an ear plate (1411) extending downward, and the ear plate (1411) is attached to and installed on the outer side surface of the second part (1212) through a fastener.

7. The combustion device according to any one of claims 1 to 6, characterized in that: The width of the ejection gap (140) along the front-to-back direction is 2 mm to 5 mm.

8. A gas water heater, comprising a housing assembly (2) and a heat exchanger (3), characterized in that: The gas water heater further comprises a combustion device (1) according to any one of claims 1 to 7, and the combustion device (1) and the heat exchanger (3) are both installed in the housing assembly (2).

9. The gas water heater according to claim 8, characterized in that: The combustion device (1) is located above the heat exchanger (3), and the lower end of the combustion chamber (11) is sealed and connected to the top opening of the heat exchanger (3).

10. The gas water heater according to claim 8, characterized in that: The gas water heater further comprises a smoke collecting hood (4) and a water collecting box (5); the bottom opening of the heat exchanger (3) is in sealed communication with the top of the smoke collecting hood (4); a water collecting hole is provided at the bottom of the smoke collecting hood (4); the water collecting box (5) is arranged below the smoke collecting hood (4) and is in sealed communication with the smoke collecting hood (4) via the water collecting hole.

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