A multi-fuel burner and method employing a dual-swirl micro-mixing structure

Abstract

This invention discloses a multi-fuel burner and method employing a dual-swirl micro-mixing structure. The burner includes a first cylinder, a second cylinder, and a third cylinder arranged sequentially from the outside to the inside. An outer swirl structure is provided between the first and second cylinders, and an inner swirl structure is provided between the second and third cylinders. The space between the first and second cylinders serves as a mixing channel for hydrogen and air, the space between the second and third cylinders serves as a mixing channel for methane and air, and the interior of the third cylinder serves as a mixing channel for ammonia and air. This invention enables the mixing of hydrocarbon fuels and fuels such as hydrogen and ammonia, as well as the stable combustion of a single fuel, solving the problem of limited fuel adaptability of existing burners and flexibly realizing the conversion of traditional hydrocarbon fuels.

Description

Technical Field

[0001] This invention relates to the field of combustion appliance technology, and specifically to a multi-fuel burner and method employing a dual-swirl micro-mixing structure. Background Technology

[0002] Methane, as a common clean fuel in the energy sector, is widely used in power generation, heating, and fuel transportation. However, methane combustion produces greenhouse gases such as carbon dioxide. To achieve a low-carbon transition in combustion and reduce greenhouse gas emissions from methane combustion, the possibility of burning alternative fuels such as hydrogen and ammonia has been explored. Ammonia, as an alternative fuel, has advantages such as high hydrogen content, ease of storage and transportation, and mature production processes. Its widespread application can significantly reduce carbon dioxide emissions. However, ammonia has a low energy density, low flame propagation speed, and high ignition energy requirements, greatly weakening the stability of pure ammonia combustion, and the combustion process has a significant potential for NOx emissions. Hydrogen is considered one of the most important green and clean energy sources for the future. This gas has the opposite characteristics to ammonia; it burns quickly, releases heat rapidly, and theoretically produces only H2O with no CO2 emissions. However, due to hydrogen's high diffusion characteristics and high reactivity, its transportation, storage, and combustion processes present a series of safety issues, including potential leakage, explosion, and backfire.

[0003] Due to the significant differences in fuel characteristics between hydrogen, hydrocarbon fuels, and ammonia fuels, different types of fuels produce different calorific values, ignition points, and combustion rates. Fuel mixtures often result in poor combustion and are prone to flameout and backfire. Existing burners are designed to meet specific gaseous fuel characteristics. Furthermore, most existing burners are single-gas fuel burners, with a few containing two types of gaseous fuels. This makes it difficult for burners to adapt to the mixing ratios of various fuels, especially when dealing with gases with significantly different combustion characteristics, such as traditional hydrocarbon fuels, hydrogen, and ammonia. Poor mixing ratios will affect combustion efficiency and make it difficult to achieve low-NOx combustion. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a multi-fuel burner and method employing a dual-swirl micro-mixing structure, which can achieve the mixing of hydrocarbon fuels and fuels such as hydrogen and ammonia, as well as the stable combustion of a single fuel. This solves the problem of existing burners being adaptable to a limited range of fuels and flexibly enables the conversion of traditional hydrocarbon fuels.

[0005] The technical solution of the present invention is as follows:

[0006] In a first aspect of the invention, a multi-fuel burner employing a dual-swirl micro-mixing structure is provided, comprising a first cylinder, a second cylinder, and a third cylinder arranged sequentially from the outside to the inside. An outer swirl structure is provided between the first cylinder and the second cylinder, and an inner swirl structure is provided between the second cylinder and the third cylinder. The space between the first cylinder and the second cylinder serves as a mixing channel for hydrogen and air, the space between the second cylinder and the third cylinder serves as a mixing channel for methane and air, and the interior of the third cylinder serves as a mixing channel for ammonia and air.

[0007] In some embodiments of the present invention, the interior of the first cylinder is provided with a hydrogen annular channel, a first cooling water annular channel, and a methane annular channel.

[0008] In some embodiments of the present invention, the hydrogen annular channel is connected to a plurality of hydrogen pipes arranged radially, the ends of the hydrogen pipes are fixed on a second cylinder, and a plurality of hydrogen outlets are uniformly arranged radially between the hydrogen pipes located between the first cylinder and the second cylinder.

[0009] In some embodiments of the present invention, the methane annular channel is connected to a plurality of methane tubes arranged radially, the methane tubes pass through a second cylinder, the ends of the methane tubes are fixed on a third cylinder, and a plurality of methane outlets are uniformly arranged radially between the second cylinder and the third cylinder.

[0010] In some embodiments of the present invention, a second cooling water annular channel is provided inside the second cylinder, and the second cooling water annular channel is connected to the first cooling water annular channel through a plurality of radially arranged cooling water pipes.

[0011] In some embodiments of the present invention, the first cooling water annular channel is an annular channel with a notch, the first cooling water annular channel is connected to the cooling water inlet pipe, and the cooling water pipe located at the notch is connected to the cooling water outlet pipe.

[0012] In some embodiments of the present invention, an ammonia gas channel is provided inside the third cylinder, the upper end of the ammonia gas channel is a blunt body structure, and a plurality of ammonia gas outlets are uniformly arranged along the circumference of the blunt body structure.

[0013] In some embodiments of the present invention, both the outer swirl structure and the inner swirl structure include multiple swirl blades, which are uniformly arranged at a certain angle.

[0014] In some embodiments of the present invention, the outer swirl blades and the inner swirl blades are arranged in the same direction.

[0015] In a second aspect of the present invention, a method for operating a multi-fuel burner employing a dual-swirl micro-mixing structure is provided, comprising the following steps:

[0016] Hydrogen is mixed with the air between the first and second cylinders, and the mixing is enhanced by dispersed small holes and outer swirl blades. Methane is mixed with the air between the second and third cylinders, and the mixing is enhanced by dispersed small holes and inner swirl blades. Ammonia is mixed with the air in the third cylinder, and the mixing is enhanced by circumferentially arranged small holes and a blunt body structure. The three mixed gases have a mutual ignition effect after being ignited at the top.

[0017] During combustion, continuous circulation of cooling water prevents the burner from burning at high temperatures.

[0018] One or more technical solutions of the present invention have the following beneficial effects:

[0019] (1) The multi-fuel burner provided by the present invention has a central ammonia orifice transverse jet fast mixing, a middle layer methane orifice transverse jet fast mixing, and an outer layer hydrogen orifice transverse jet fast mixing on the burner body. The dispersed arrangement of the orifice transverse jet structure (micro-mixing structure) can not only improve the jet velocity and enhance the mixing effect, but also, in particular, can play a role in preventing backfire for hydrogen, a highly reactive fuel.

[0020] (2) The multi-fuel burner provided by this invention has swirl vanes in the hydrogen and methane channels after the transverse jet mixing in the small holes, and a blunt body structure at the end of the ammonia pipeline. The swirl parameters in the hydrogen and methane channels are independent of each other, so as to achieve a more flexible structural setting for different fuel characteristics. Hydrogen and methane are easy to ignite and are arranged in the outer layer of the burner for combustion; ammonia is difficult to ignite and is injected into the central area of ​​the burner. Under the ignition effect of the outer flame surface, the ignition performance of ammonia is improved. In the mixed fuel combustion mode, the backflow zone generated by the inner and outer swirl vanes and the central blunt body helps the interaction between the flames of each layer and strengthens combustion; in the single fuel combustion mode, the swirl vane / blunt body structure of each combustion zone can maintain the combustion stability of its own flame.

[0021] (3) The multi-fuel burner provided by the present invention has a spoke structure design for both the hydrogen pipeline and the methane pipeline. The pipelines are evenly distributed along the radial direction of the cylinder, and a series of equally spaced small holes are opened at the same position on each pipeline as gas outlets. The larger outlet flow velocity is beneficial to improve the turbulence loudness and enhance the local mixing effect, ensuring that the ejected gas is evenly distributed in the circumferential direction and can be evenly mixed with air at various positions in the cylinder space.

[0022] (4) The multi-fuel burner provided by the present invention has a backflow phenomenon in the design of the swirl blade structure and the blunt body structure. The backflow introduces some combustion products back into the combustion zone and mixes them again with the newly entered fuel and air. The generation of this backflow can improve the utilization rate of fuel and air during the combustion process, making the combustion more complete, reducing the generation of incomplete combustion products, and improving the combustion efficiency.

[0023] (5) The ignition characteristics of the three fuels are hydrogen > methane > ammonia. This invention arranges the three fuels from the outside to the inside, which can effectively ignite the less flammable fuels in the inner layer with the more stable flame of the outer layer. In addition, the required volumetric flow rate of hydrogen fuel is much higher than that of methane when achieving the same power combustion. In this design, hydrogen is arranged in the outermost layer, and the larger cross-sectional area of ​​the hydrogen / air mixture outlet can ensure that the hydrogen velocity and methane velocity at the burner outlet are not much different when achieving the same heat load combustion, thus ensuring stable combustion. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall structure of the multi-fuel burner according to an embodiment of the present invention;

[0025] Figure 2 This is a top view of the multi-fuel burner according to an embodiment of the present invention;

[0026] Figure 3 This is a bottom view of the multi-fuel burner according to an embodiment of the present invention;

[0027] Figure 4 This is an internal cross-sectional view of the multi-fuel burner according to an embodiment of the present invention;

[0028] Figure 5 This is a schematic diagram of the lower half of the multi-fuel burner according to an embodiment of the present invention;

[0029] Figure 6 This is an internal cross-sectional view of the lower half of the multi-fuel burner according to an embodiment of the present invention;

[0030] Figure 7 This is a layout diagram of the hydrogen pipeline;

[0031] Figure 8 This is a layout diagram of the cooling water pipes;

[0032] Figure 9 This is a layout diagram of the methane pipeline;

[0033] Figure 10 This is a schematic diagram of the upper half of the multi-fuel burner according to an embodiment of the present invention;

[0034] Figure 11 This is an internal sectional view of the upper half of the multi-fuel burner according to an embodiment of the present invention;

[0035] Figure 12 This is a side view of the upper half of the multi-fuel burner according to an embodiment of the present invention;

[0036] Figure 13 This is a bottom view of the upper half of the multi-fuel burner according to an embodiment of the present invention.

[0037] In the diagram: 1. First cylinder; 2. Second cylinder; 3. Third cylinder; 4. Hydrogen inlet pipe; 5. Hydrogen annular channel; 6. Hydrogen pipe; 7. Hydrogen outlet; 8. Cooling water inlet pipe; 9. First cooling water annular channel; 10. Cooling water pipe; 11. Second cooling water annular channel; 12. Cooling water outlet pipe; 13. Methane inlet pipe; 14. Methane annular channel; 15. Methane pipe; 16. Methane outlet; 17. Outer swirl vane; 18. Inner swirl vane; 19. First air passage; 20. Second air passage; 21. Third air passage; 22. Ammonia inlet; 23. Ammonia outlet. Detailed Implementation

[0038] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0039] Example 1

[0040] In a typical embodiment of the present invention, a multi-fuel burner employing a dual-swirl micro-mixing structure is proposed, such as... Figure 1 As shown, it includes a first cylinder 1, a second cylinder 2, and a third cylinder 3 arranged sequentially from the outside to the inside. An outer swirl vane 17 is provided between the first cylinder 1 and the second cylinder 2, and an inner swirl vane is provided between the second cylinder 2 and the third cylinder 3. The space between the first cylinder 1 and the second cylinder 2 serves as a mixing channel for hydrogen and air, the space between the second cylinder 2 and the third cylinder 3 serves as a mixing channel for methane and air, and the interior of the third cylinder 3 serves as a mixing channel for ammonia and air.

[0041] Specific examples Figures 2 to 4 As shown, the first cylinder 1, the second cylinder 2, and the third cylinder 3 all have a certain thickness and are divided into an upper structure and a lower structure. The swirl blades are set in the upper structure, and the gas pipeline is set in the lower structure.

[0042] like Figure 5 and Figure 6 As shown, the interior of the first cylinder 1 is provided with a hydrogen annular channel 5, a first cooling water annular channel 9 and a methane annular channel 14 arranged sequentially from top to bottom. In this embodiment, the hydrogen annular channel 5 and the methane annular channel 14 are both annular channels along the cylinder wall, and the first cooling water annular channel 9 is an annular pipe with a notch at 345°.

[0043] like Figure 7As shown, the annular hydrogen channel 5 is connected to multiple radially arranged hydrogen pipes 6. The ends of the hydrogen pipes 6 are fixed to the second cylinder 2. Multiple hydrogen outlets 7 are evenly arranged between the first cylinder 1 and the second cylinder 2. The multiple radially arranged hydrogen pipes 6 are equally spaced, and the spacing angle in this embodiment is 15°.

[0044] like Figure 8 As shown, the methane annular channel 14 is connected to a plurality of radially arranged methane tubes 15. The methane tubes 15 pass through the second cylinder, and the ends of the methane tubes 15 are fixed on the third cylinder 3. A plurality of methane outlets 16 are evenly arranged between the second cylinder 2 and the third cylinder 3. The plurality of radially arranged methane tubes 15 are equally spaced, and the spacing angle in this embodiment is 15°.

[0045] like Figure 9 As shown, the second cylinder 2 has a second cooling water annular channel 11 inside. The second cooling water annular channel 11 is connected to the first cooling water annular channel 9 through multiple radially arranged cooling water pipes 10. The first cooling water annular channel 9 is an annular channel with a notch. The first cooling water annular channel 9 is connected to the cooling water inlet pipe 8, and the cooling water pipe 10 located at the notch is connected to the cooling water outlet pipe 12. In this embodiment, the multiple radially arranged cooling water pipes 10 are equally spaced, and the spacing angle in this embodiment is 15°.

[0046] In this embodiment, each cooling water pipe 10 is directly below the corresponding hydrogen pipe 6, and the methane pipe 15 has an angle of 7.5° with the adjacent hydrogen pipe.

[0047] Furthermore, an ammonia gas channel is provided inside the third cylinder. The upper end of the ammonia gas channel is a blunt body structure. Multiple ammonia gas outlets 23 are uniformly arranged on the blunt body structure. The direction of the ammonia gas outlets is inclined downward. The angle between the axis of the circular hole and the axis of the burner is 45°. Ammonia gas enters from the ammonia gas inlet 22, flows upward along the ammonia gas channel, and flows out from the ammonia gas outlet 23.

[0048] In this embodiment, the methane outlet, hydrogen outlet, and ammonia outlet are all equally spaced circular holes.

[0049] Hydrogen gas enters through hydrogen inlet pipe 4, flows along a hydrogen annular channel into equally spaced hydrogen pipes, and finally exits through equally spaced hydrogen outlets 7 on the hydrogen pipes. Cooling water enters through cooling water inlet pipe 8, flows along a first cooling water annular channel 9 into equally spaced cooling water pipes 10, then converges into a second cooling water annular channel 11, and finally flows out through cooling water outlet pipe 12. Methane enters through methane inlet pipe 13, flows along a methane annular channel 14 into equally spaced methane pipes 15, and finally exits through equally spaced methane outlets 16 on the methane pipes.

[0050] In this embodiment, both the hydrogen outlet and the methane outlet are horizontal, allowing the lateral jet to mix better with the vertical airflow.

[0051] like Figure 10-13 As shown, the outer swirl blades and the inner swirl blades are arranged in the same direction. The blades of the outer swirl blades and the inner swirl blades can be installed at different tilt angles as needed, with an angle range of 30°-60°.

[0052] In this embodiment, the spacing between each blade of the outer swirl blade is 15°, and the spacing between each blade of the inner swirl blade is 30°.

[0053] In this invention, the angle and number of swirl blades are adjustable, depending on the burner size and the number of swirl blades, making the burner more adaptable to different operating conditions. Furthermore, the spacing angle and number of the hydrogen pipe, methane pipe, and cooling water pipe can also be adjusted according to the actual burner size and operating conditions.

[0054] The working principle of the multi-fuel burner with a dual-swirl micro-mixing structure provided in this embodiment is as follows:

[0055] Hydrogen gas exits horizontally from hydrogen outlet 7 and mixes with air flowing vertically upwards from the first air channel 19. Both then pass through the outer swirl vanes 17, enhancing the mixing effect and promoting combustion stability. Ammonia gas exits from ammonia outlet 23 and mixes with air flowing vertically upwards from the third air channel 21. The ammonia gas ejected from outlet 23 forms a 45° angle with the air flowing vertically upwards from the third air channel 21 on the blunt-body structure. This collision of the two gases ensures a more uniform mixing of ammonia and air, and the mixed gas is ignited at the top. Methane exits horizontally from methane outlet 16 and mixes with air flowing vertically from the second air channel 20. Both then pass through the inner swirl vanes 18, enhancing the mixing effect and promoting combustion stability. Air is fed axially into the burner. The bottom of the first air channel 19, the second air channel 20, and the third air channel 21 are air inlets, and the top is the air outlet. The axially flowing air mixes with the corresponding fuel gases in the three channels.

[0056] Hydrogen and methane are both highly reactive gases, while ammonia has lower combustion reactivity compared to them. The combustion flame, from the outside in, consists of a hydrogen flame, a methane flame, and an ammonia flame; these three flames can ignite each other. Methane and hydrogen burn faster and can also stabilize the combustion of ammonia.

[0057] Backflow occurs in both the outer swirl blade 17 and the inner swirl blade 18, as well as the bluff body structure on the ammonia pipeline. Backflow reintroduces some combustion products into the combustion zone, where they mix again with the newly entering fuel and air, improving the utilization rate of fuel and air during combustion, resulting in more complete combustion and reducing the generation of incomplete combustion products.

[0058] When hydrogen is ignited, a backfire typically occurs, where the flame propagates backward from the burner into the gas pipeline. This backfire can potentially trigger an explosion, causing unpredictable accidents. Therefore, hydrogen backfire is a crucial safety concern in hydrogen energy applications. In this invention, the hydrogen outlet is located below the outer swirl vanes, forming equally spaced circular holes on the spoked straight tube. This outlet placement ensures that the hydrogen flame can only appear at a minimum level with the outer swirl vanes, flush with the spoked straight tube. Furthermore, the absence of oxidizer within the spoked straight tube, coupled with the burner material absorbing some of the flame's heat, prevents the flame from returning to the pipeline.

[0059] During combustion, the high temperature of combustion raises the temperature of the swirl burner. Exposed to high temperature and excess air, the carbon elements in the burner may react chemically with oxygen to form gaseous carbon dioxide or directly vaporize into gases such as carbon monoxide, leading to a reduction in the carbon content on the material surface, i.e., decarburization. Decarburization affects the structure and performance of the burner, causing the burner components to gradually lose their original strength and wear resistance, thus significantly shortening their service life. To solve this problem, this invention installs cooling water pipes inside the burner, continuously circulating cooling water to reduce the burner temperature and extend its service life. Simultaneously, the placement of hydrogen pipes and outlets, along with the presence of wall-mounted cooling water pipes, avoids the potential danger of hydrogen backfire and solves the problem of hydrogen backfire caused by fuel preheating.

[0060] Due to the different properties of various gases, most existing burners are single-gas fuel burners, and a few are burners that use two gaseous fuels. This invention, however, designs a burner that incorporates three gaseous fuels. Hydrogen, ammonia, and methane, three gases with different properties, can be burned individually or simultaneously in the burner, enabling flexible conversion of traditional hydrocarbon fuels. Furthermore, compared to methane, hydrogen has a higher calorific value, but its molar mass is relatively smaller. To achieve the same power output, the required hydrogen fuel volumetric flow rate is much higher than that of methane. In this invention, the hydrogen flow pipe area is larger than the methane flow pipe area, thus ensuring that the hydrogen velocity and methane velocity at the burner outlet are not significantly different when achieving the same heat load combustion, guaranteeing stable combustion.

[0061] Example 2

[0062] In a typical embodiment of the present invention, a method for operating a multi-fuel burner employing a dual-swirl micro-mixing structure is proposed, comprising the following steps:

[0063] Hydrogen is mixed with the air between the first and second cylinders, and the mixing is enhanced by the outer swirl vanes; methane is mixed with the air between the second and third cylinders, and the mixing is enhanced by the outer swirl vanes; ammonia is mixed with the air inside the third cylinder, and the mixing is enhanced by the bluff body structure; the three mixed gases are ignited together at the top.

[0064] During combustion, the burner temperature is reduced by continuously circulating cooling water.

[0065] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A multi-fuel burner employing a dual-swirl micro-mixing structure, characterized in that, It includes a first cylinder, a second cylinder, and a third cylinder arranged sequentially from the outside to the inside. An outer swirling structure is provided between the first cylinder and the second cylinder, and an inner swirling structure is provided between the second cylinder and the third cylinder. The space between the first cylinder and the second cylinder serves as a mixing channel for hydrogen and air, the space between the second cylinder and the third cylinder serves as a mixing channel for methane and air, and the interior of the third cylinder serves as a mixing channel for ammonia and air. The interior of the first cylinder is provided with a hydrogen annular channel, a first cooling water annular channel, and a methane annular channel; The hydrogen annular channel is connected to multiple hydrogen pipes arranged radially. The ends of the hydrogen pipes are fixed on the second cylinder. Multiple hydrogen outlets are evenly arranged radially between the first cylinder and the second cylinder. The methane annular channel is connected to multiple methane tubes arranged radially. The methane tubes pass through the second cylinder, and the ends of the methane tubes are fixed on the third cylinder. Multiple methane outlets are evenly arranged radially between the second cylinder and the third cylinder.

2. The multi-fuel burner employing a dual-swirl micro-mixing structure as described in claim 1, characterized in that, The second cylinder has a second cooling water annular channel inside, which is connected to the first cooling water annular channel through multiple radially arranged cooling water pipes.

3. The multi-fuel burner employing a dual-swirl micro-mixing structure as described in claim 2, characterized in that, The first cooling water annular channel is an annular channel with a gap. The first cooling water annular channel is connected to the cooling water inlet pipe, and the cooling water pipe located at the gap is connected to the cooling water outlet pipe.

4. The multi-fuel burner employing a dual-swirl micro-mixing structure as described in claim 1, characterized in that, The third cylinder is provided with an ammonia gas channel. The upper end of the ammonia gas channel is a blunt body structure, and multiple ammonia gas outlets are uniformly arranged along the circumference of the blunt body structure.

5. The multi-fuel burner employing a dual-swirl micro-mixing structure as described in claim 1, characterized in that, Both the outer and inner swirling structures include multiple swirling blades, which are evenly spaced at a certain angle.

6. The multi-fuel burner employing a dual-swirl micro-mixing structure as described in claim 5, characterized in that, The outer and inner swirl blades are arranged in the same direction.

7. A method for operating a multi-fuel burner employing a dual-swirl micro-mixing structure as described in any one of claims 1-6, characterized in that, Includes the following steps: Hydrogen is mixed with the air between the first and second cylinders, and the mixing is enhanced by dispersed small holes and outer swirl blades. Methane is mixed with the air between the second and third cylinders, and the mixing is enhanced by dispersed small holes and inner swirl blades. Ammonia is mixed with the air in the third cylinder, and the mixing is enhanced by circumferentially arranged small holes and a blunt body structure. The three mixed gases have a mutual ignition effect after being ignited at the top. During combustion, continuous circulation of cooling water prevents the burner from burning at high temperatures.

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