A combustion system having annular heat exchange passages

Abstract

The utility model discloses a kind of combustion systems with annular heat exchange passage, belong to combustion equipment technical field, including heat exchanger, combustion mechanism, heat exchanger is formed by the coaxial several heat exchange sleeve, form a ring heat exchange passage between two adjacent heat exchange sleeve, heat exchange passage includes air passage and flue gas passage, the end of heat exchanger is equipped with air inlet and flue gas inlet;Heat exchanger outside is equipped with gas collection shell, gas collection shell inside forms cold air cavity and flue gas cavity, flue gas passage is equipped with several smoke exhaust pipe extending to flue gas cavity;The axial position of heat exchanger forms hot air cavity, air passage is equipped with several exhaust pipe extending to the inside of hot air cavity;Combustion mechanism is equipped with adjacent gas pipe and ignition electrode, the end of gas pipe and ignition electrode is commonly equipped with combustion chamber in communication with hot air cavity;The combustion system of the utility model can improve the heat exchange efficiency between flue gas and combustion air.

Description

Technical Field

[0001] This utility model relates to the field of combustion equipment technology, specifically to a combustion system with an annular heat exchange channel. Background Technology

[0002] In industrial heat treatment furnaces and heating furnaces, most use combustion systems based on burners for heating. To improve fuel utilization, heat exchangers are usually installed in the combustion system to recover the heat carried in the flue gas. This heat is used to preheat the combustion air. To improve the heat exchange efficiency of the heat exchanger, the internal channels of the heat exchanger are modified by methods such as fluid turbulence and fluid segmentation to improve the flow mode or flow path of the fluid. Fluid turbulence improves heat exchange efficiency by reducing the fluid flow velocity or extending the flow path. However, the fluid can still easily accumulate and form fluid clusters inside the heat exchanger. The center of the fluid cluster cannot make contact with the heat transfer medium, resulting in inefficient heat exchange. Fluid segmentation usually uses small-diameter tube bundles to form fine fluids inside the tube bundles, allowing the fluid to make more full contact with the tube walls and use the tube walls as the heat transfer medium to achieve heat exchange. However, this method can only allow the flue gas or combustion air to flow inside the tube bundles. The other fluid can only flow in the space outside the tube bundles, which makes the fluid flowing outside the tube bundles easy to accumulate and form fluid clusters, also resulting in lower heat exchange efficiency.

[0003] Based on the above, Chinese patent document CN111322889A discloses a self-preheating burner tube bundle heat exchange tube, a self-preheating burner, and a heat exchange method for improving the heat exchange efficiency of the self-preheating burner. The self-preheating burner tube bundle heat exchange tube includes an outer tube and an inner tube. One end of the inner tube extends out of the outer tube, and the other end extends into the outer tube. The inner tube consists of an inner tube inlet, an inner tube wall, and an inner tube outer inlet. The inner tube inlet is located inside the outer tube. The outer tube consists of an outer tube bottom, an outer tube wall, and an outer tube inlet. A gap is provided between the inner tube inlet and the outer tube bottom. The inner tube and the inner tube and the outer tube form a fluid flow channel.

[0004] The aforementioned patent documents disclose a heat exchange tube and burner that increase the heat exchange area by using thin-walled tube bundles as heat exchange elements. The thin-walled tube bundles can divide the combustion air into several fine fluid streams, thereby increasing the specific surface area of ​​the flame-retardant air. However, since the flue gas needs to contact the outer surface of the thin-walled tube bundle, it is difficult to form a fine fluid stream by dividing it. During the flow of the flue gas inside the flue outside the thin-walled tube bundle, it is easy to form a fluid cluster due to aggregation. The fluid cluster is difficult to fully contact the surface of the thin-walled tube bundle, thereby affecting the efficiency of heat transfer from the flue gas to the thin-walled tube bundle, and thus affecting the heat exchange efficiency. Therefore, the heat exchange tube and burner in the aforementioned patent documents still have room for improvement. Utility Model Content

[0005] To address the technical deficiencies in the prior art, this utility model proposes a combustion system with an annular heat exchange channel, which solves the aforementioned technical problems and meets practical needs. The specific technical solution is as follows: A combustion system with an annular heat exchange channel includes a heat exchanger and a combustion mechanism. The heat exchanger is composed of several coaxial heat exchange tubes, and an annular heat exchange channel is formed between two adjacent heat exchange tubes. The heat exchanger has at least two heat exchange channels inside, including at least one air channel and at least one flue gas channel. The ends of the heat exchanger are provided with air inlets and flue gas inlets that are respectively matched with the air channel and the flue gas channel. The heat exchanger is fitted with a gas collecting shell on the outside. The gas collecting shell forms an independent cold air cavity and a flue gas cavity inside. The surface of the gas collecting shell is provided with an air inlet and a flue gas outlet that are respectively matched with the cold air cavity and the flue gas cavity. The cold air cavity is matched with an air inlet. The flue gas passage is provided with several exhaust pipes extending to the flue gas cavity at the end away from the flue gas inlet. A hot air cavity is formed inside the heat exchange sleeve closest to the axis of the heat exchanger, and a number of exhaust pipes extending into the hot air cavity are provided at the end of the air passage away from the air inlet. The combustion mechanism is provided with an adjacent gas pipe and an ignition electrode. One end of the gas pipe outlet and the ignition end of the ignition electrode are fitted together with a combustion chamber, which is connected to a hot air cavity.

[0006] As a further technical solution of this utility model, the heat exchanger is composed of at least six heat exchange sleeves and at least five heat exchange channels are formed inside the heat exchanger. The heat exchange channels include at least two air channels and at least three flue gas channels, and any one of the air channels is located between two adjacent flue gas channels.

[0007] As a further technical solution of this utility model, a plurality of air bridge connectors are provided between two adjacent air channels to connect the two air channels, and the air bridge connectors are located at the end of the air channel away from the air inlet.

[0008] As a further technical solution of this utility model, a plurality of flue gas bridge pipes are provided between two adjacent flue gas channels to connect the two flue gas channels. The flue gas bridge pipes are located at the end of the flue gas channel away from the flue gas inlet, and the flue gas bridge pipes are matched with the positions of the exhaust pipes.

[0009] As a further technical solution of this utility model, a number of connecting ribs are provided between any two adjacent heat exchange sleeves in the heat exchange channel.

[0010] As a further technical solution of this utility model, several heat exchange sleeves are used together to form an integrally formed heat exchanger, and the two heat exchange sleeves forming the air channel are fixedly connected to each other at the end away from the air inlet to form a closed end. The two heat exchange sleeves forming the flue gas passage are fixedly connected to each other at the end away from the flue gas inlet to form a closed end; The air inlet and flue gas inlet are located at opposite ends of the heat exchanger.

[0011] As a further technical solution of this utility model, the wall thickness of the heat exchange sleeve is 2~5mm, and the gap thickness between two adjacent heat exchange sleeves is 1~5mm.

[0012] As a further technical solution of this utility model, the gas pipe and the ignition electrode are both fixedly connected to the gas collecting shell, the gas pipe and the ignition electrode both extend along the hot air cavity, and the opening at one end of the exhaust pipe faces the combustion chamber.

[0013] As a further technical solution of this utility model, an air intake pipe and a radiant pipe are provided between the heat exchanger and the combustion mechanism. One end of the air intake pipe is connected to the hot air cavity and the other end is connected to the combustion chamber. One end of the radiant pipe is connected to the combustion chamber and the other end is connected to the end of the heat exchanger that has a flue gas inlet.

[0014] The beneficial effects of this utility model are as follows: This utility model discloses a combustion system that achieves efficient heat exchange between flue gas and combustion air through an internal annular heat exchange channel. The flue gas generated after combustion flows in a relatively narrow heat exchange channel inside the heat exchanger, while the combustion air flows in a heat exchange channel adjacent to the flue gas. The flue gas and combustion air exchange heat through the tube wall of the heat exchange sleeve. The heat exchange channel is relatively thin, making it difficult for the flue gas and combustion air to accumulate and form fluid clumps. This allows both the flue gas and combustion air to have sufficient contact with the heat exchange sleeve, enabling the flue gas and combustion air inside the heat exchanger to achieve high heat exchange efficiency. This allows the combustion air after heat exchange to better improve the combustion efficiency of the combustion mechanism. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a combustion system with an annular heat exchange channel. Figure 1 .

[0016] Figure 2 A schematic diagram of the structure of a heat exchanger for a combustion system with an annular heat exchange channel. Figure 1 .

[0017] Figure 3 yes Figure 2 Sectional view at point AA.

[0018] Figure 4 yes Figure 2 Sectional view at point BB.

[0019] Figure 5 yes Figure 2 Sectional view at point CC.

[0020] Figure 6 yes Figure 2 Sectional view at point DD.

[0021] Figure 7 yes Figure 3 A partial schematic diagram at point E in the middle.

[0022] Figure 8 yes Figure 3 A partial schematic diagram at point F in the middle.

[0023] Figure 9 yes Figure 4 A partial schematic diagram at point G in the middle.

[0024] Figure 10 yes Figure 4 A partial schematic diagram at point H in the middle.

[0025] Figure 11 yes Figure 3 A partial schematic diagram of point I in the middle.

[0026] Figure 12 This is a schematic diagram of a combustion system with an annular heat exchange channel. Figure 2 .

[0027] Figure 13 A schematic diagram of the structure of a heat exchanger for a combustion system with an annular heat exchange channel. Figure 2 .

[0028] Figure 14 yes Figure 13 A partial schematic diagram at point J in the middle.

[0029] Wherein: 1-Heat exchanger, 11-Heat exchange sleeve, 12-Heat exchange channel, 121-Air channel, 122-Flue gas channel, 123-Air inlet, 124-Flue gas inlet, 125-Closed end, 13-Exhaust pipe, 14-Hot air cavity, 15-Exhaust pipe, 16-Air bridge connector, 17-Flue gas bridge connector, 18-Connecting rib, 2-Combustion mechanism, 21-Gas pipe, 22-Ignition electrode, 23-Combustion chamber, 3-Gas collection shell, 31-Cold air cavity, 32-Flue gas cavity, 33-Air inlet, 34-Flue gas outlet, 4-Inlet pipe, 5-Radiant tube. Detailed Implementation

[0030] The embodiments of this utility model will be described below with reference to the accompanying drawings and related examples. The embodiments of this utility model are not limited to the following examples, and this utility model relates to relevant necessary components in this technical field, which should be regarded as well-known technology in this technical field and can be known and mastered by those skilled in this technical field.

[0031] A combustion system with an annular heat exchange channel includes a heat exchanger 1 and a combustion mechanism 2. The heat exchanger 1 is composed of several coaxial heat exchange tubes 11. An annular heat exchange channel 12 is formed between two adjacent heat exchange tubes 11. The heat exchanger 1 is provided with at least two heat exchange channels 12. The heat exchange channel 12 includes at least one air channel 121 and at least one flue gas channel 122. The ends of the heat exchanger 1 are provided with an air inlet 123 and a flue gas inlet 124 that are respectively matched with the air channel 121 and the flue gas channel 122. The heat exchanger 1 is fitted with a gas collecting shell 3 on the outside. The gas collecting shell 3 forms an independent cold air cavity 31 and a flue gas cavity 32. The surface of the gas collecting shell 3 is provided with an air inlet 33 and a flue gas outlet 34 that are respectively matched with the cold air cavity 31 and the flue gas cavity 32. The cold air cavity 31 is matched with the air inlet 123. The end of the flue gas passage 122 away from the flue gas inlet 124 is provided with a number of exhaust pipes 13 extending to the flue gas cavity 32. The number of exhaust pipes 13 are arranged in an array with the axis of the heat exchanger 1 as the center. A hot air cavity 14 is formed inside the heat exchange sleeve 11 closest to the axis of the heat exchanger 1. A number of exhaust pipes 15 extending into the hot air cavity 14 are provided at the end of the air passage 121 away from the air inlet 123. The number of exhaust pipes 15 are arranged in an array with the axis of the hot air cavity 14 as the center. The combustion mechanism 2 is provided with an adjacent gas pipe 21 and an ignition electrode 22. One end of the gas pipe 21 and the ignition end of the ignition electrode 22 are fitted together with a combustion chamber 23, and the combustion chamber 23 is connected to the hot air cavity 14.

[0032] This utility model discloses a combustion system that achieves efficient heat exchange between flue gas and combustion air through an internal annular heat exchange channel, referring to... Figure 1 The combustion system mainly consists of a combustion mechanism 2 and a heat exchanger 1. The combustion mechanism 2 is mainly used to burn the mixture formed by mixing fuel and combustion air. The gas pipe 21 guides the gas to the combustion chamber 23 to mix with the combustion air. The ignition electrode 22 ignites the mixture by means of electric spark to achieve combustion. The heat generated by combustion is used for industrial heat treatment through direct heating or thermal radiation. The heat exchanger 1 is mainly used to exchange heat between the flue gas generated by combustion in the combustion mechanism 2 and the combustion air. The hot air formed by preheating the combustion air participates in combustion in the combustion mechanism 2, thereby improving combustion efficiency. Reference Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9 , Figure 10 , Figure 11 The heat exchanger 1 is composed of several coaxial heat exchange tubes 11 with gradually increasing diameters. The gap between adjacent heat exchange tubes 11 forms an annular heat exchange channel 12. The heat exchange channel 12 mainly serves as a channel for the flow of combustion air or flue gas for heat exchange. The heat exchange channel 12 is composed of an air channel 121 for guiding the combustion air and a flue gas channel 122 for guiding the flue gas. Usually, the number of flue gas channels 122 is more than that of air channels 121. This is because the combustion air entering the heat exchanger 1 is only a part of all the combustion air participating in combustion. The amount of flue gas produced after combustion is usually greater than the amount of combustion air. Therefore, the heat exchanger 1 needs more flue gas channels 122 to provide sufficient space for the flow of flue gas. The gas collecting shell 3 guides the combustion air into the cold air chamber 31 through the air inlet 33. The combustion air in the cold air chamber 31 enters the air passage 121 through the air inlet 123. The flue gas generated after combustion enters the flue gas passage 122 through the flue gas inlet 124. The flue gas passage 122 and the air passage 121 are arranged alternately from the inside to the outside with the axis of the heat exchanger 1 as the center. During the flow of flue gas and combustion air in the heat exchanger 1, heat exchange is carried out through the heat exchange sleeve 11 as the heat transfer medium. The heat carried in the flue gas is transferred to the combustion air and the temperature of the combustion air is raised to form hot air. The hot air enters the hot air chamber 14 through the exhaust pipe 15. After the heat exchange is completed, the flue gas enters the flue gas chamber 32 through the exhaust pipe 13 and is discharged from the flue gas outlet 34. It should be noted that the wall thickness of the heat exchanger tube 11 is 2~5mm, preferably less than 3mm, and the thickness of the gap between two adjacent heat exchanger tubes 11, i.e., the thickness of the heat exchange channel 12, is 1~5mm, preferably less than 3mm. The heat exchanger 1 of this invention simultaneously cuts the flue gas and combustion air through the heat exchanger tubes 11, causing the flue gas and combustion air to form a fluid with a thickness of less than 5mm that flows inside the heat exchange channel 12. During the flow of the fluid inside the heat exchange channel 12, heat is transferred through the tube wall of the heat exchanger tubes 11, and any two adjacent heat exchanger tubes 11... A number of connecting ribs 18 are provided in the heat exchange channel 12 between the heat exchange tubes 11 and 12. The connecting ribs 18 can serve as a medium for heat transfer between adjacent heat exchange tubes 11, avoiding thermal stress caused by temperature difference between different heat exchange tubes 11, and enhancing the heat transfer efficiency inside the heat exchanger 1. Flue gas and combustion air can release or absorb heat through the heat exchange tubes 11 on both sides inside the heat exchange channel 12. Furthermore, flue gas and combustion air are difficult to accumulate and form fluid masses inside the narrow heat exchange channel 12, so the flue gas and combustion air inside the heat exchanger 1 can achieve high heat exchange efficiency. It should be further explained that the heat exchanger 1 of this utility model is preferably made by 3D printing technology. During the manufacturing process, the heat exchanger 1 is formed by melting and stacking metal materials layer by layer along the axial extension direction of the heat exchanger 1 using a high-energy beam, or by solidifying ceramic slurry layer by layer along the axial extension direction of the heat exchanger 1 to form a green body, and then sintering the green body at high temperature after resin removal. The heat exchange sleeve 11 and the connecting rib 18 can be formed simultaneously during the manufacturing process of the heat exchanger 1. However, it is difficult to fix several connecting ribs 18 between the heat exchange sleeve 11 using traditional welding methods. The connecting rib 18 can also serve as a support structure between adjacent heat exchange sleeves 11. The heat exchanger 1 can be formed into a continuous integral structure by using the above-mentioned 3D printing method, which can avoid cracking of the welded structure due to stress, thereby improving the structural stability of the heat exchanger 1.

[0033] As one of the preferred embodiments of this utility model, refer to Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9 , Figure 10The heat exchanger 1 is composed of at least six heat exchange tubes 11 and at least five heat exchange channels 12 are formed inside the heat exchanger 1. The heat exchange channels 12 include at least two air channels 121 and at least three flue gas channels 122. Any one air channel 121 is located between two adjacent flue gas channels 122. The heat exchanger 1 can form more heat exchange channels 12 by being composed of more heat exchange tubes 11, thereby cutting the flue gas and combustion air into multiple fluids with lower thickness, thereby increasing the specific surface area of ​​the flue gas and combustion air inside the heat exchanger 1, which is beneficial to improving the heat exchange efficiency. Furthermore, several air bridge pipes 16 are provided between two adjacent air channels 121 to connect the two air channels 121. The air bridge pipes 16 are located at the end of the air channel 121 away from the air inlet 123. Since the inner diameters of different air channels 121 are different, the volume of the air channel 121 farther from the axis of the heat exchanger 1 is larger, and more combustion air flows in the air channel 121. At the same time, the inner diameter of the hot air cavity 14 is fixed, and the number of exhaust pipes 15 arranged in an array around the axis of the hot air cavity 14 is fixed. If each air channel 121 is provided with the same number of exhaust pipes 15, the flow rate of the combustion air in the larger air channel 121 will be slower. In order to balance the flow rate of the combustion air in each air channel 121, part of the combustion air in the larger air channel 121 is diverted to the smaller air channel 121 through the air bridge pipes 16 to balance the flow rate of the combustion air in different air channels and ensure that the combustion air flows uniformly inside the heat exchanger 1. Furthermore, several flue gas bridge pipes 17 are provided between two adjacent flue gas passages 122 to connect the two flue gas passages 122. The flue gas bridge pipes 17 are located at the end of the flue gas passage 122 away from the flue gas inlet 124, and the positions of the flue gas bridge pipes 17 and the exhaust pipes 13 are matched. Since the inner diameter of the flue gas passage 122 closer to the axis of the heat exchanger 1 is smaller, fewer exhaust pipes 13 can be installed in the flue gas passage 122. In order to ensure the flow rate of flue gas inside the flue gas passage 122 with a smaller inner diameter, the two adjacent flue gas passages 122 are connected by the flue gas bridge pipes 17. The flue gas bridge pipes 17 and the exhaust pipes 13 together serve as channels for flue gas to leave the two adjacent flue gas passages 122, so that the flue gas inside the flue gas passage 122 with a smaller inner diameter also has more channels to discharge the flue gas.

[0034] As one of the preferred embodiments of this utility model, refer to Figure 2 , Figure 3 , Figure 5 , Figure 7 , Figure 8Several heat exchange tubes 11 together form an integrally molded heat exchanger 1. Two heat exchange tubes 11 forming an air passage 121 are fixedly connected to each other at the end away from the air inlet 123 to form a closed end 125; two heat exchange tubes 11 forming a flue gas passage 122 are fixedly connected to each other at the end away from the flue gas inlet 124 to form a closed end 125; the air inlet 123 and the flue gas inlet 124 are located at opposite ends of the heat exchanger 1. The heat exchanger 1 with the above structure allows the flue gas and combustion air to flow independently in adjacent heat exchange channels 12, and the two flow in opposite directions to achieve countercurrent heat exchange. The temperature of the flue gas decreases as it flows inside the heat exchanger 1, and it is eventually discharged through the exhaust pipe 13 near the closed end 125. Meanwhile, the temperature of the combustion air increases as it flows inside the heat exchanger 1, and it is eventually discharged through the exhaust pipe 15 near the closed end 125. This ensures that the low-temperature flue gas and low-temperature combustion air are matched inside the heat exchanger 1, and the high-temperature flue gas and high-temperature combustion air are matched, so that the heat in the flue gas can be efficiently transferred to the combustion air.

[0035] As one of the preferred embodiments of this utility model, refer to Figure 1 Both the gas pipe 21 and the ignition electrode 22 are fixedly connected to the gas collecting shell 3. Both the gas pipe 21 and the ignition electrode 22 extend along the hot air cavity 14. The opening at one end of the exhaust pipe 15 faces the combustion chamber 23. In the gas system of this utility model, the heat exchanger 1 and the combustion mechanism 2 can be integrated. This combustion system is mainly used for open flame heating. The combustion system performs open flame heating in equipment such as heating furnaces. The flue gas passage 122 is connected to the inside of the furnace through the flue gas inlet 124, so that the flue gas in the furnace can enter the heat exchanger 1 for heat exchange. The hot air formed after heat exchange is discharged from the exhaust pipe 15 and then directly mixed with the fuel in the combustion chamber 23 to participate in the combustion reaction. If the power of the combustion system is 100kW, the surface area of ​​the heat exchange sleeve 11 inside the heat exchanger 1 is not less than 4m². 2 It can meet the heating conditions of up to 1100℃, and the exhaust temperature of the flue gas after heat exchange is below 300℃.

[0036] As one of the preferred embodiments of this utility model, refer to Figure 12 , Figure 13 , Figure 14A gas inlet pipe 4 and a radiant pipe 5 are provided between the heat exchanger 1 and the combustion mechanism 2. One end of the gas inlet pipe 4 is connected to the hot air cavity 14 and the other end is connected to the combustion chamber 23. One end of the radiant pipe 5 is connected to the combustion chamber 23 and the other end is connected to the end of the heat exchanger 1 with a flue gas inlet 124. In the combustion system of this utility model, the heat exchanger 1 and the combustion mechanism 2 can be designed separately. The combustion system with this structure is mainly used for radiant tube heating. The combustion mechanism 2 burns at one end of the radiant pipe 5 to generate a flame. The flue gas flows along the radiant pipe 5 and radiates heat to the outside. It enters the heat exchanger 1 through the flue gas inlet 124 at the other end of the radiant pipe 5 for heat exchange. The hot air formed after heat exchange leaves the hot air cavity 14 and flows to the combustion chamber 23 through the gas inlet pipe 4 and mixes with the fuel to participate in the combustion reaction. If the power of the combustion system is 100kW, the surface area of ​​the heat exchange sleeve 11 inside the heat exchanger 1 is not less than 4m². 2 It can meet the heating conditions of up to 950℃, and the exhaust temperature of the flue gas after heat exchange is below 300℃.

[0037] In summary, this utility model discloses a combustion system that achieves efficient heat exchange between flue gas and combustion air through an internal annular heat exchange channel. The flue gas generated after combustion in the combustion mechanism 2 flows in a relatively narrow heat exchange channel 12 inside the heat exchanger 1. At the same time, the combustion air flows in the heat exchange channel 12 adjacent to the flue gas. The flue gas and combustion air exchange heat through the tube wall of the heat exchange sleeve 11. The heat exchange channel 12 has a low thickness, making it difficult for the flue gas and combustion air to accumulate and form fluid masses. This allows the flue gas and combustion air to fully contact the heat exchange sleeve 11, enabling the flue gas and combustion air inside the heat exchanger 1 to achieve high heat exchange efficiency. This allows the combustion air after heat exchange to better improve the combustion efficiency of the combustion mechanism 2.

[0038] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present utility model, and these improvements and modifications should also be considered within the protection scope of the present utility model.

Claims

1. A combustion system with an annular heat exchange channel, comprising a heat exchanger (1) and a combustion mechanism (2), characterized in that, The heat exchanger (1) is composed of several coaxial heat exchange sleeves (11), and an annular heat exchange channel (12) is formed between two adjacent heat exchange sleeves (11). The heat exchanger (1) is provided with at least two heat exchange channels (12), and the heat exchange channel (12) includes at least one air channel (121) and at least one flue gas channel (122). The ends of the heat exchanger (1) are provided with an air inlet (123) and a flue gas inlet (124) that are respectively matched with the air channel (121) and the flue gas channel (122). The heat exchanger (1) is fitted with a gas collecting shell (3) on the outside. The gas collecting shell (3) forms an independent cold air cavity (31) and a flue gas cavity (32) inside. The surface of the gas collecting shell (3) is provided with an air inlet (33) and a flue gas outlet (34) that are respectively matched with the cold air cavity (31) and the flue gas cavity (32). The cold air cavity (31) is matched with the air inlet (123). The flue gas passage (122) is provided with a number of exhaust pipes (13) extending to the flue gas cavity (32) at the end away from the flue gas inlet (124). A hot air cavity (14) is formed inside the heat exchange sleeve (11) closest to the axis of the heat exchanger (1). The air passage (121) is provided with a number of exhaust pipes (15) extending into the hot air cavity (14) at the end away from the air inlet (123). The combustion mechanism (2) is provided with an adjacent gas pipe (21) and an ignition electrode (22). The outlet end of the gas pipe (21) and the ignition end of the ignition electrode (22) are together fitted with a combustion chamber (23), and the combustion chamber (23) is connected to the hot air cavity (14).

2. The combustion system with an annular heat exchange channel according to claim 1, characterized in that, The heat exchanger (1) consists of at least six heat exchange sleeves (11) and at least five heat exchange channels (12) are formed inside the heat exchanger (1). The heat exchange channels (12) include at least two air channels (121) and at least three flue gas channels (122). Any one of the air channels (121) is located between two adjacent flue gas channels (122).

3. The combustion system with an annular heat exchange channel according to claim 2, characterized in that, A plurality of air bridges (16) are provided between two adjacent air channels (121) to connect the two air channels (121), and the air bridges (16) are located at the end of the air channel (121) away from the air inlet (123).

4. The combustion system with an annular heat exchange channel according to claim 1, characterized in that, A plurality of flue gas bridge pipes (17) are provided between two adjacent flue gas passages (122) to connect the two flue gas passages (122). The flue gas bridge pipes (17) are located at the end of the flue gas passage (122) away from the flue gas inlet (124), and the flue gas bridge pipes (17) are matched with the position of the exhaust pipe (13).

5. The combustion system with an annular heat exchange channel according to claim 1, characterized in that, A number of connecting ribs (18) are provided in the heat exchange channel (12) between any two adjacent heat exchange sleeves (11).

6. The combustion system with an annular heat exchange channel according to claim 1, characterized in that, Several heat exchange sleeves (11) together form an integral heat exchanger (1), and the two heat exchange sleeves (11) forming the air passage (121) are fixedly connected to each other at the end away from the air inlet (123) to form a closed end (125). The two heat exchange sleeves (11) forming the flue gas passage (122) are fixedly connected to each other at the end away from the flue gas inlet (124) to form a closed end (125). The air inlet (123) and the flue gas inlet (124) are located at opposite ends of the heat exchanger (1).

7. The combustion system with an annular heat exchange channel according to claim 1, characterized in that, The wall thickness of the heat exchange sleeve (11) is 2~5mm, and the gap thickness between two adjacent heat exchange sleeves (11) is 1~5mm.

8. The combustion system with an annular heat exchange channel according to claim 1, characterized in that, The gas pipe (21) and the ignition electrode (22) are both fixedly connected to the gas collection shell (3). The gas pipe (21) and the ignition electrode (22) extend along the hot air cavity (14). The opening at one end of the exhaust pipe (15) faces the combustion chamber (23).

9. The combustion system with an annular heat exchange channel according to claim 1, characterized in that, The heat exchanger (1) and the combustion mechanism (2) are provided with an air intake pipe (4) and a radiation pipe (5). One end of the air intake pipe (4) is connected to the hot air cavity (14) and the other end is connected to the combustion chamber (23). One end of the radiation pipe (5) is connected to the combustion chamber (23) and the other end is connected to the end of the heat exchanger (1) that is provided with a flue gas inlet (124).

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