Fuel gas premixer

Abstract

The invention discloses a fuel gas premixer which comprises a premixing unit, an anti-backfire unit and a backmixing unit which are sequentially connected in the gas flowing direction, the premixing unit is used for premixing fuel gas and air, and the backmixing unit is used for forcibly reversing the front of mixed gas flow and mixing the mixed gas flow with follow-up mixed gas; wherein the anti-backfire unit comprises a main pipeline and a plurality of resistance pipelines which are sequentially arranged along the main pipeline, the gas inlet end of the main pipeline is communicated with the premixing unit, the gas outlet end of the main pipeline is communicated with the backmixing unit, each resistance pipeline is arranged in a bent mode, and the two ends of each resistance pipeline are communicated with the main pipeline, so that during backfire, the resistance pipelines are communicated with the main pipeline. And the resistance pipeline is used for guiding part of reverse gas back to the main pipeline to collide with reverse gas in the main pipeline. The main pipeline and the resistance pipeline are matched for use, so that the effects of forward accelerated conduction and reverse cut-off are achieved, and the tempering phenomenon can be effectively prevented.

Description

Technical Field

[0001] The invention relates to the technical field of premixers, and in particular to a gas premixer. Background Art

[0002] In order to suppress pollutant emissions and achieve clean fuel combustion, the transition from non-premixed combustion to premixed low-temperature combustion can essentially reduce emissions of pollutants such as NOx and CO, while improving combustion efficiency.

[0003] CN207146391U A gas premixer, comprising a premixer shell, a supply pipe and a gas injection part; the premixer shell has an inner chamber on the inner side; the supply pipe is installed at the right end of the premixer shell, and a mixing flow path is formed on the inner side of the supply pipe, and the mixing flow path is connected with the inner chamber; a through hole is opened on the premixer shell, and the axis of the through hole coincides with the axis of the supply pipe; the gas injection part comprises: a nozzle, the inner side of which is provided with a gas supply flow path; a nozzle bracket, which is used to install and support the nozzle on the premixer shell; wherein the nozzle passes through the through hole and is located in the supply pipe.

[0004] However, the above-mentioned prior art has certain safety hazards due to the narrow combustion limit range and poor flame stability of premixed combustion, especially for premixed combustion of high-hydrogen or pure hydrogen fuel, which is prone to induce flashback risk. Summary of the invention

[0005] The purpose of the present invention is to overcome the above technical deficiencies and to provide a gas premixer to solve the technical problem that the prior art is prone to induce flashback danger and has certain safety hazards.

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical solutions: The present invention provides a gas premixer, comprising a premixing unit, an anti-flashback unit and a backmixing unit connected in sequence along the gas flow direction, wherein the premixing unit is used to premix gas and air, and the backmixing unit is used to force the front of the mixed gas flow to reverse and mix with the subsequent mixed gas; Among them, the anti-backfire unit includes a main pipeline and a plurality of resistance pipelines arranged in sequence along the main pipeline, the air inlet end of the main pipeline is connected to the premixing unit, and the air outlet end of the main pipeline is connected to the backmixing unit, and each of the resistance pipelines is bent and its two ends are connected to the main pipeline, so that during backfire, the resistance pipeline is used to guide part of the reverse gas back to the main pipeline to collide with the reverse gas in the main pipeline.

[0007] In some embodiments, the resistance pipe includes a first connecting section and a second connecting section connected in sequence along the gas flow direction, the first connecting section is bent in an arc shape from one end close to the air inlet end to the other end in the gas flow direction toward gradually away from the main pipe, and the angle between the tangent of the connection between the first connecting section and the main pipe and the axis of the main pipe is an acute angle, and the second connecting section is inclined in the gas flow direction toward gradually approaching the main pipe.

[0008] In some embodiments, the plurality of resistance pipes are arranged alternately along opposite sides of the main pipe; or The plurality of resistance pipes are symmetrically arranged along two opposite sides of the main pipe.

[0009] In some embodiments, the gas premixer further comprises a cooling jacket, wherein the cooling jacket is disposed on the outer periphery of the anti-flashback unit, and the cooling jacket is used to cool the anti-flashback unit.

[0010] In some embodiments, the premixing unit includes a mixing chamber, a first pipe and a second pipe. The mixing chamber is also provided with a gas inlet, a mixed gas outlet and an air inlet. The gas inlet and the mixed gas outlet are arranged opposite to each other. The mixed gas outlet is connected to the air inlet end of the main pipe. One end of the first pipe is inserted into the mixing chamber from the gas inlet, and one end of the second pipe is connected to the air inlet.

[0011] In some embodiments, the first conduit and the second conduit are perpendicular to each other.

[0012] In some embodiments, a Laval nozzle is disposed at one end of the first pipe extending into the mixing chamber.

[0013] In some embodiments, the back-mixing unit includes a back-mixing cylinder and an air supply channel. The back-mixing cylinder is porous, one end of the back-mixing cylinder is connected to the air outlet end of the main pipeline, the air supply channel is sleeved on the outer periphery of the back-mixing cylinder, one end of which is sealed and connected to the back-mixing cylinder, and the other end is used to connect to the burner.

[0014] In some embodiments, the circumference of the back-mixing cylinder is porous, and one end of the back-mixing cylinder away from the main pipeline is flat or conical.

[0015] In some embodiments, the gas outlet end of the main pipe is inserted into the return-mixing cylinder, and the length of the main pipe extending into the return-mixing cylinder is equal to 1 / 3-1 / 2 of the length of the return-mixing cylinder.

[0016] Compared with the prior art, the gas premixer provided by the present invention has a resistance pipe that is bent and connected to the main pipe at both ends. When in use, the premixed fuel gas enters the main pipe. When the gas flows in the main pipe, only a small part of the gas enters the resistance pipe, and due to the change in pressure during the flow, the fluid will obtain an acceleration effect when flowing in the forward direction. At this time, the resistance pipe can accelerate the flow of the gas. When the gas refluxes, the gas is divided into two parts and enters the main pipe and the resistance pipe respectively. When the gas in the resistance pipe flows into the main pipe, it collides with the gas in the main pipe, thereby offsetting each other, thereby preventing the gas from flowing from the outlet to the inlet, thereby achieving the purpose of preventing backfire. The present application utilizes the coordinated use of the main pipe and the resistance pipe to play the role of forward acceleration conduction and reverse cutoff, which can effectively prevent the occurrence of backfire.

[0017] The premixing unit described in the present application is used for gas-injected air to form a premixed fuel gas and then send it into the anti-backfire unit. The anti-backfire unit is used to accelerate the premixed fuel gas and inject it into the backmixing unit to prevent backfire. The backmixing unit is used to force the accelerated fuel gas front to reverse and remix it with the subsequent fuel gas to enhance the fuel gas premixing effect and ensure that the gas and air are completely mixed.

[0018] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the preferred embodiments of the present invention are described in detail as follows with reference to the accompanying drawings. The specific implementation of the present invention is given in detail by the following embodiments and their accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of an embodiment of a gas premixer provided by the present invention; Figure 2 yes Figure 1 A partial schematic diagram of the premixing unit; Figure 3 yes Figure 1 Partial schematic diagram of the middle anti-flashback unit; Figure 4 yes Figure 1 Partial schematic diagram of the back-mixing unit.

[0020] Description of reference numerals: 1-premixing unit, 11-mixing chamber, 111-mixed gas outlet, 12-first pipeline, 121-Laval nozzle, 13-second pipeline, 2-anti-backfire unit, 21-main pipeline, 22-resistance pipeline, 221-first connecting section, 222-second connecting section, 23-cooling jacket, 3-backmixing unit, 31-backmixing cylinder, 32-gas supply channel. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0022] In order to solve the technical problem that the prior art is prone to induce flashback danger and has certain safety hazards, the present invention provides a gas premixer that can prevent gas from flowing from the gas outlet to the gas inlet, thereby achieving the purpose of preventing flashback.

[0023] See also Figure 1 , Figure 1 Schematic diagram of the structure of a gas premixer in one embodiment of the present invention.

[0024] The present invention provides a gas premixer, comprising a premixing unit 1, an anti-backfire unit 2 and a backmixing unit 3 connected in sequence along the gas flow direction, wherein the premixing unit 1 is used to premix gas and air, and the backmixing unit 3 is used to force the front of the mixed gas flow to reverse and mix with the subsequent mixed gas; wherein the anti-backfire unit 2 comprises a main pipeline 21 and a plurality of resistance pipelines 22 arranged in sequence along the main pipeline 21, wherein the air inlet end of the main pipeline 21 is connected to the premixing unit 1, and the air outlet end of the main pipeline 21 is connected to the backmixing unit 3, and each of the resistance pipelines 22 is bent and its two ends are connected to the main pipeline 21, so that when backfires, the resistance pipeline 22 is used to guide part of the reversed gas back to the main pipeline 21 to collide with the reverse gas in the main pipeline 21.

[0025] In this embodiment, the resistance pipe 22 is bent and both ends are connected to the main pipe 21. When in use, the premixed fuel gas enters the main pipe 21. When the gas flows in the main pipe 21, only a small part of the gas enters the resistance pipe 22. Due to the change in pressure during the flow, the gas will obtain an acceleration effect when flowing in the forward direction. At this time, the resistance pipe 22 can play a role in accelerating the flow of gas. When the gas refluxes, the reverse gas is divided into two parts and enters the main pipe 21 and the resistance pipe 22 respectively. The force pipe 22 is bent, and when the gas flows therein, it collides with the side wall of the resistance pipe 22, thereby losing some energy. Then, when the gas in the resistance pipe 22 flows into the main pipe 21, it collides with the gas in the main pipe 21, thereby offsetting each other and consuming the energy of the gas, thereby preventing the gas from flowing from the outlet to the inlet, thereby achieving the purpose of preventing backfire. The present application utilizes the coordinated use of the main pipe 21 and the resistance pipe 22 to play the role of forward acceleration conduction and reverse cutoff, which can effectively prevent the occurrence of backfire.

[0026] The premixing unit 1 described in the present application is used to inject gas into air to form a premixed fuel gas and then send it to the anti-backfire unit 2. The anti-backfire unit 2 is used to accelerate the premixed fuel gas and inject it into the backmixing unit 3 to prevent backfire. The backmixing unit 3 is used to force the accelerated fuel gas front to reverse and remix it with the subsequent fuel gas to enhance the fuel gas premixing effect and ensure that the gas and air are completely mixed.

[0027] It should be noted that the gas flowing from the gas inlet end to the gas outlet end in the main pipeline 21 is a forward gas flow, and the gas flowing from the gas outlet end to the gas inlet end is a reverse gas flow.

[0028] In some embodiments, see Figure 1 and Figure 3 The resistance pipe 22 includes a first connecting section 221 and a second connecting section 222 which are connected in sequence along the gas flow direction. The first connecting section 221 is bent in an arc shape from one end close to the air inlet end to the other end in the gas flow direction in a direction gradually away from the main pipe 21, and the angle between the tangent of the connection between the first connecting section and the main pipe and the axis of the main pipe is an acute angle. The second connecting section 222 is inclined in a direction gradually approaching the main pipe 21 in the gas flow direction.

[0029] In this embodiment, the first connecting section 221 has a first end and a second end that are relatively set, and the second connecting section 222 has a third end and a fourth end that are relatively set, the first end is communicated with the main pipeline 21, the second end is communicated with the third end, and the fourth end is communicated with the main pipeline 21, the flow direction of the gas in the resistance pipeline 22 is from the first end to the fourth end, the first connecting section 221 is bent in an arc shape from the first end to the second end in the direction of gas flow gradually away from the main pipeline 21, the first connecting section 221 has a first tangent at the first end, and the angle between the first tangent and the axis of the main pipeline 21 is less than ninety degrees, the second connecting section 222 is linearly arranged, and the tangent of the second connecting section 222 at the fourth end is the axis of the second connecting section 222, and the first The angle between the axis of the second connecting section 222 and the axis of the main pipeline 21 is less than ninety degrees. With such a configuration, on the one hand, when the gas flows from the air inlet end to the air outlet end in the main pipeline 21, only a small part of the gas enters the resistance pipeline 22. Due to the special structure of the resistance pipeline 22, the gas in the resistance pipeline 22 will flow into the main pipeline 21 unimpeded, thereby accelerating the gas in the main pipeline 21. On the other hand, when the gas refluxes, part of the reverse gas can easily enter the resistance pipeline 22 from the fourth end, and the first connecting section 221 can change the gas flow direction, so that the flow direction of the gas discharged from the first end is opposite to the gas flow direction of the main pipeline 21, and the collision and consumption of the two airflows are utilized to prevent the occurrence of reflux, thereby achieving the purpose of preventing backfire.

[0030] In some embodiments, see Figure 1 and Figure 3 The plurality of resistance pipes 22 are alternately arranged along opposite sides of the main pipe 21 .

[0031] In this embodiment, in order to further enhance the reverse blocking effect, the plurality of resistance pipes 22 are divided into two groups. The two groups of resistance pipes 22 are respectively located on two opposite sides of the main pipe 21 , and the two groups of resistance pipes 22 are staggered.

[0032] Furthermore, the head end and the tail end of the adjacent resistance pipes 22 correspond to each other, that is, the first end and the fourth end of the adjacent resistance pipes 22 correspond to each other. With such an arrangement, when gas reflux occurs, the reverse gas is divided into three parts and respectively enters the main pipe 21, enters the previous resistance pipe 22 from the first end of the previous resistance pipe 22, and enters the next resistance pipe 22 from the fourth end of the next resistance pipe 22, thereby realizing multi-directional diversion of gas and playing a role in increasing reverse resistance.

[0033] In other embodiments, the plurality of resistance pipes 22 are symmetrically arranged along opposite sides of the main pipe 21 .

[0034] Specifically, the plurality of resistance pipes 22 are divided into two groups and are located on two opposite sides of the main pipe 21 and are arranged correspondingly.

[0035] In some embodiments, see Figure 1 and Figure 3 The gas premixer further comprises a cooling jacket 23 , wherein the cooling jacket 23 is sleeved on the outer periphery of the anti-flashback unit 2 , and the cooling jacket 23 is used for cooling the anti-flashback unit 2 .

[0036] In this embodiment, in order to further enhance the anti-flashback effect, a cooling jacket 23 is also provided on the periphery of the anti-flashback unit 2. The cooling medium in the cooling jacket 23 can exchange heat with the gas in the main pipeline 21 and the resistance pipeline 22, thereby reducing the temperature of the gas in the main pipeline 21 and the resistance pipeline 22, thereby preventing the occurrence of flashback.

[0037] Specifically, the cooling jacket 23 includes a shell, and the shell is sleeved on the outer periphery of the anti-backfire unit 2, that is, the main pipe 21 and the resistance pipe 22 are both located inside the shell, and both ends of the main pipe 21 extend out of the shell, and the connection between the main pipe 21 and the shell is sealed. The interior of the shell is used to accommodate a cooling medium, and the shell is also provided with a liquid inlet and a liquid outlet, and the liquid inlet and the liquid outlet are connected to an external coolant circulation device so that the cooling medium circulates in the shell and between the coolant circulation device, and the liquid inlet is located on the lower side of the shell, and the liquid outlet is located on the upper side of the shell, and the liquid inlet and the liquid outlet are arranged diagonally. Such a setting can extend the residence time of the cooling medium in the shell and improve the cooling effect.

[0038] In some embodiments, see Figure 1 and Figure 2 The premixing unit 1 includes a mixing chamber 11, a first pipeline 12 and a second pipeline 13. The mixing chamber 11 is also provided with a gas inlet, a mixed gas outlet 111 and an air inlet. The gas inlet and the mixed gas outlet 111 are arranged opposite to each other. The mixed gas outlet 111 is connected to the air inlet end of the main pipeline 21. One end of the first pipeline 12 is inserted into the mixing chamber 11 from the gas inlet, and one end of the second pipeline 13 is connected to the air inlet.

[0039] In this embodiment, the mixing chamber 11 is provided with the gas inlet and the mixed gas outlet 111 on opposite sides along the gas flow direction, and the air inlet is located beside the mixing chamber 11. The first pipe 12 is sealed and connected to the gas inlet, and a portion of the first pipe 12 is located in the mixing chamber 11. One end of the first pipe 12 is arranged close to the mixed gas outlet 111, and the other end of the first pipe 12 is used to communicate with the gas source so as to transport the gas into the mixing chamber 11 through the first pipe 12. One end of the second pipe 13 is sealed and connected to the air inlet, and the other end of the second pipe 13 is used to communicate with the air source or the outside world so as to transport air into the mixing chamber 11 through the second pipe 13, thereby promoting the mixing of gas and air to form a premixed fuel gas.

[0040] In some embodiments, see Figure 1 and Figure 2 , the first pipe 12 and the second pipe 13 are perpendicular to each other.

[0041] In this embodiment, since the first pipe 12 and the second pipe 13 are perpendicular to each other, the flow directions of the gas flow and the air flow are perpendicular to each other, thereby increasing the premixing time and premixing distance of the gas and air, thereby enhancing the premixing effect.

[0042] In some embodiments, see Figure 1 and Figure 2 A Laval nozzle 121 is provided at one end of the first pipe 12 extending into the mixing chamber 11 .

[0043] In this embodiment, in order to increase the flow rate of the gas entering the mixing chamber 11, a Laval nozzle 121 is installed at one end of the first pipe 12. The diameter of the Laval nozzle 121 is gradually reduced from both ends to the middle. When the gas enters the front half of the Laval nozzle 121, the movement of the gas follows the principle that "when the fluid moves in the tube, the flow rate is large at a small cross-section and the flow rate is small at a large cross-section", so the airflow is continuously accelerated. When the gas reaches the middle of the Laval nozzle 121, the flow rate has exceeded the speed of sound. However, the transonic fluid no longer follows the principle of "the flow rate is large at a small cross-section and the flow rate is small at a large cross-section" when moving, but on the contrary, the larger the cross-section, the faster the flow rate. In the rear half of the Laval nozzle 121, the speed of the gas flow is further accelerated. Therefore, when the gas enters the Laval nozzle 121 from the first pipeline 12, the jet is accelerated. The accelerated gas generates a certain negative pressure in the mixing chamber 11. At the same time, air enters vertically from the air inlet. Since the mixing chamber 11 is in a negative pressure state, the air is sucked into the mixing chamber 11 to mix with the gas, thereby improving the premixing effect.

[0044] In some embodiments, see Figure 1 and Figure 4 The back-mixing unit 3 includes a back-mixing cylinder 31 and an air supply channel 32. The back-mixing cylinder 31 is porous. One end of the back-mixing cylinder 31 is connected to the air outlet end of the main pipeline 21. The air supply channel 32 is sleeved on the outer periphery of the back-mixing cylinder 31, and one end thereof is sealed and connected to the back-mixing cylinder 31, and the other end is used to connect to the burner.

[0045] In this embodiment, the diameter of the return-mixing cylinder 31 is larger than the diameter of the main pipeline 21, and the diameter of the air supply channel 32 is larger than the diameter of the return-mixing cylinder 31. One end of the return-mixing cylinder 31 corresponds to the main pipeline 21 and is sealed and connected to the side wall of the cooling sleeve 23. The air supply channel 32 is sleeved on the outer periphery of the return-mixing cylinder 31, and one end of the air supply pipeline is sealed and connected to the side wall of the cooling sleeve 23. The premixed gas that has been forward accelerated enters the return-mixing cylinder 31, and the high-speed airflow front reaches the return-mixing cylinder 31 and collides with it. The airflow front is forced to be deflected in the reverse direction and remixed with the subsequent fuel gas to enhance the premixing effect of the fuel gas, and then overflows through the holes of the return-mixing cylinder 31 into the air supply pipeline, and finally is supplied to the burner through the air supply pipeline. Such a setting can enhance the premixing effect of the fuel gas and ensure that the gas and air are completely mixed.

[0046] In some embodiments, see Figure 1 and Figure 4 The circumference of the return mixing cylinder 31 is porous, and one end of the return mixing cylinder 31 away from the main pipeline 21 is flat or conical.

[0047] In this embodiment, one end of the return-mixing cylinder 31 is blocked in a flat or conical shape, and a plurality of holes are opened on the side wall of the return-mixing cylinder 31. The plurality of holes are arranged in an array around the return-mixing cylinder, and the diameter of the holes is much smaller than the diameter of the return-mixing cylinder 31. When the high-speed airflow front enters the return-mixing cylinder 31, it collides with the blocked end of the return-mixing cylinder 31, so that the airflow front is forced to be deflected in the reverse direction so that it can be mixed with the subsequent fuel gas again, and the mixed gas flows from the plurality of holes to the gas supply pipe 32.

[0048] In some embodiments, see Figure 1 and Figure 4 The outlet end of the main pipe 21 is inserted into the return mixing cylinder 31, and the length of the main pipe 21 extending into the return mixing cylinder 31 is equal to 1 / 3-1 / 2 of the length of the return mixing cylinder 31. This arrangement can prevent the high-speed airflow front from escaping in the front section of the return mixing cylinder, so that it can directly collide with the blocked end of the return mixing cylinder 31.

[0049] In order to better understand the present invention, the following Figures 1 to 4The technical solution of the present invention is described in detail: The gas is transported into the mixing chamber 11 through the first pipeline 12, and the air is transported into the mixing chamber 11 through the second pipeline 13. The gas is accelerated by the Laval nozzle 121, and the accelerated gas generates a certain negative pressure in the mixing chamber 11. At the same time, air enters vertically from the air inlet. Since the mixing chamber 11 is in a negative pressure state, the air is sucked into the mixing chamber 11 and mixed with the gas to form a premixed fuel gas. The premixed fuel gas enters the main pipeline 21. The forward acceleration conduction and reverse cutoff characteristics of the main pipeline 21 and the resistance pipeline 22 are utilized to effectively prevent the occurrence of backfire, and the ignition temperature of the premixed fuel gas can be reduced by the cooling sleeve 23. Then, the gas is transported to the return mixing cylinder 31 through the main pipeline 21, and the air flow front enters the return mixing cylinder 31 and collides with the blocked end of the return mixing cylinder 31, so that the air flow front is forced to be deflected in the reverse direction so that it can be mixed with the subsequent fuel gas again, and then overflows into the gas supply pipeline through the hole of the return mixing cylinder 31, and is finally supplied to the burner for use through the gas supply pipeline.

[0050] The present application provides a premixing unit 1 and utilizes the fuel gas to induce air for forced mixing, thereby enhancing the fuel gas mixing effect.

[0051] The present application utilizes the coordinated use of the main pipeline 21 and the resistance pipeline 22 to enable the gas to be accelerated in the forward direction and cut off in the reverse direction, thereby effectively preventing the occurrence of backfire. The ignition temperature of the premixed fuel gas can be reduced through the cooling jacket 23, thereby further enhancing the anti-backfire effect.

[0052] The present application uses the back-mixing unit 3 to force the fuel gas flow to reverse the front direction and remix it with the subsequent fuel gas, thereby further enhancing the fuel gas premixing effect and ensuring that the fuel gas and air are completely mixed.

[0053] The specific implementation of the present invention described above does not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A gas premixer, characterized in that: It includes a premixing unit, an anti-flashback unit and a backmixing unit which are sequentially connected along the gas flow direction, wherein the premixing unit is used to premix the gas and the air, and the backmixing unit is used to force the front of the mixed gas flow to reverse and mix with the subsequent mixed gas; Among them, the anti-backfire unit includes a main pipeline and a plurality of resistance pipelines arranged in sequence along the main pipeline, the air inlet end of the main pipeline is connected to the premixing unit, and the air outlet end of the main pipeline is connected to the backmixing unit, and each of the resistance pipelines is bent and connected to the main pipeline at both ends, so that during backfire, the resistance pipeline is used to guide part of the reverse gas back to the main pipeline to collide with the reverse gas in the main pipeline.

2. The gas premixer according to claim 1, characterized in that: The resistance pipe includes a first connecting section and a second connecting section which are connected in sequence along the gas flow direction. The first connecting section is bent in an arc shape from one end close to the air inlet end to the other end in the gas flow direction toward gradually away from the main pipe, and the angle between the tangent of the connection between the first connecting section and the main pipe and the axis of the main pipe is an acute angle, and the second connecting section is inclined in the gas flow direction toward gradually approaching the main pipe.

3. The gas premixer according to claim 1, characterized in that: The plurality of resistance pipes are arranged alternately along opposite sides of the main pipe; or The plurality of resistance pipes are symmetrically arranged along two opposite sides of the main pipe.

4. The gas premixer according to claim 1, characterized in that: The gas premixer further comprises a cooling jacket, which is arranged on the outer periphery of the anti-flashback unit and is used for cooling the anti-flashback unit.

5. The gas premixer according to claim 1, characterized in that: The premixing unit includes a mixing chamber, a first pipeline and a second pipeline. The mixing chamber is also provided with a gas inlet, a mixed gas outlet and an air inlet. The gas inlet and the mixed gas outlet are arranged opposite to each other. The mixed gas outlet is connected to the air inlet end of the main pipeline. One end of the first pipeline is inserted into the mixing chamber from the gas inlet, and one end of the second pipeline is connected to the air inlet.

6. The gas premixer according to claim 5, characterized in that: The first pipe and the second pipe are perpendicular to each other.

7. The gas premixer according to claim 5, characterized in that: A Laval nozzle is disposed at one end of the first pipe extending into the mixing chamber.

8. The gas premixer according to claim 1, characterized in that: The back-mixing unit includes a back-mixing cylinder and an air supply channel. The back-mixing cylinder is porous. One end of the back-mixing cylinder is connected to the air outlet end of the main pipeline. The air supply channel is sleeved on the outer circumference of the back-mixing cylinder, and one end of the back-mixing cylinder is sealed and connected to the back-mixing cylinder, and the other end is used to connect to the burner.

9. The gas premixer according to claim 8, characterized in that: The circumference of the return-mixing cylinder is arranged in a multi-hole configuration, and one end of the return-mixing cylinder away from the main pipeline is arranged in a flat plate or a pointed cone.

10. The gas premixer according to claim 8, characterized in that: The gas outlet end of the main pipeline is inserted into the return mixing cylinder, and the length of the main pipeline extending into the return mixing cylinder is equal to 1 / 3-1 / 2 of the length of the return mixing cylinder.

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