Fuel nozzles and combustion equipment

Abstract

The present application relates to a fuel nozzle, comprising: a main channel, one end of which is blind, the side wall of the main channel being provided with a plurality of fuel outlets near the blind end; and a plurality of branch channels, the inlet of each branch channel being communicated with a corresponding fuel outlet, the outlet of the branch channel being higher than the fuel outlet communicated therewith, the outlets of the plurality of branch channels being located outside the main channel. The present application also relates to a combustion device provided with the above fuel nozzle.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of combustion, and in particular to a fuel nozzle and a combustion device. Background Art

[0002] The pulverized coal burner is the core equipment for organizing the efficient combustion of pulverized coal. The pulverized coal burner in the existing technology generally includes structures such as the primary air channel, the central air channel, and the secondary air channel. The central air channel is in the center of the burner, the primary air channel transports the pulverized coal to be sprayed into the furnace, and the secondary air channel is on the periphery of the primary air channel. The secondary air channel often includes an inner secondary air channel and an outer secondary air channel. The secondary air surrounds the periphery of the primary air, forming a combustion mode of air-enclosed powder. The primary air carrying pulverized coal entering the burner is ejected from only one nozzle, namely the fuel nozzle. This fuel organization method uses the principle of jet entrainment to strengthen the mixing of fuel and air and the reflux of hot flue gas to ensure stable flame combustion. Its flame rigidity is large and the flame is long.

[0003] Chinese patent ZL201410367608.8 discloses a pulverized fuel self-preheating device and method, and a pulverized fuel combustion boiler system. The pulverized fuel is partially burned and released heat in the self-preheating device, and the pulverized fuel itself is added to form a high-temperature gas-solid mixed fuel (for general coal, it can reach 700-1000°C), which is then burned. This method forms a high-temperature gas-solid mixed fuel by preheating, and the high-temperature solid fuel therein is easy to burn after modification. It has many advantages such as good ignition stability, good burnout and low nitrogen oxide emissions. It is an efficient and clean coal combustion technology.

[0004] However, the physical and chemical properties of high-temperature gas-solid mixed fuels are completely different from those of room-temperature pulverized coal. Existing pulverized coal burners suitable for room-temperature pulverized coal are difficult to adapt to the combustion mechanism of high-temperature gas-solid mixed fuels formed after self-preheating. No other fuel combustion mechanism technology can achieve efficient and clean combustion of high-temperature gas-solid mixed fuels. Summary of the Invention

[0005] The present invention is proposed to alleviate or solve at least one aspect or at least one point of the above problems.

[0006] The invention provides a multi-channel high-temperature gas-solid mixed fuel nozzle and a combustion device having the fuel nozzle.

[0007] According to one aspect of an embodiment of the present invention, a fuel nozzle is provided, comprising:

[0008] a main channel, one end of the main channel being a blind end, and a side wall of the main channel being provided with a plurality of fuel outlets near the blind end; and

[0009] A plurality of branch channels are provided, wherein the inlet of each branch channel is connected to the corresponding fuel outlet, the outlet of the branch channel is higher than the fuel outlet connected thereto, and the outlets of the plurality of branch channels are located outside the main channel.

[0010] According to another aspect of an embodiment of the present invention, a combustion system is provided, comprising:

[0011] combustion space;

[0012] At least one nozzle is adapted to provide fuel into the combustion space, and the at least one nozzle comprises the above-mentioned fuel nozzle. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1A is a schematic cross-sectional view of a fuel injection port according to an exemplary embodiment of the present invention;

[0014] Figure 1B for Figure 1A A schematic cross-sectional view of the fuel nozzle along the AA direction;

[0015] Figure 1C is a schematic cross-sectional view of a fuel injection port according to another exemplary embodiment of the present invention;

[0016] Figure 2A A schematic top view of a fuel nozzle according to another exemplary embodiment of the present invention;

[0017] Figure 2B For the Figure 2A AA cross-sectional view;

[0018] Figure 3A is a schematic cross-sectional view of a fuel injection port according to yet another exemplary embodiment of the present invention;

[0019] Figure 3B for Figure 3A A schematic cross-sectional view of the fuel nozzle along the AA direction;

[0020] Figure 4A A schematic cross-sectional view of a fuel injection port according to another exemplary embodiment of the present invention;

[0021] Figure 4B for Figure 4A A schematic cross-sectional view of the fuel nozzle along the AA direction;

[0022] Figure 5A A schematic cross-sectional view of a fuel injection port according to another exemplary embodiment of the present invention;

[0023] Figure 5B for Figure 5A A schematic cross-sectional view of the fuel nozzle along the AA direction;

[0024] Figure 5C for Figure 5A The fuel nozzle along Figure 5B BB-direction cross-sectional diagram;

[0025] Figures 6A-6D FIG. 1 is a schematic diagram of a combustion device according to an exemplary embodiment of the present invention, the combustion device comprising a fuel nozzle according to the present invention. DETAILED DESCRIPTION

[0026] The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the overall inventive concept of the present invention and should not be understood as limiting the present invention. In the present invention, the same reference numerals represent the same or similar components.

[0027] Figure 1A is a schematic cross-sectional view of a fuel injection port according to an exemplary embodiment of the present invention. Figure 1B for Figure 1A Schematic cross-sectional view of the fuel nozzle along the AA direction.

[0028] like Figure 1A As shown, the fuel nozzle includes a fuel main channel 1 and a fuel branch channel. The fuel main channel is defined by a wall 11. The inlet of the fuel branch channel communicates with the fuel outlet 13 of the main channel 1. The fuel branch channel includes an outlet 14. Figure 1A As shown, the outlet 14 is located at a position higher than the fuel outlet 13. Figure 1A and Figure 1B As shown, the outlet 14 is located outside the main channel 1. Figure 1A As shown, the top of the main channel 1 is a blind end 12. Optionally, the blind end 12 is in the form of a semicircular dome. In one embodiment of the present invention, Figure 1A As shown, the top of the blind end 12 is higher than the outlet 14 of the branch channel.

[0029] In the present invention, the main channel 1 and the branch channel are cast by refractory materials. The main channel 1 is generally a tubular with a circular cross section. In one embodiment, the thickness of the wall 11 is not less than 50 mm. A fuel branch channel is provided on the side wall of the main channel 1 near the blind end 12. Figure 1A As shown, the branch channel is an L-shaped elbow made of refractory material, one end of which is connected to the main channel 1 through the fuel outlet 13 and the other end is the outlet 14.

[0030] The number of branch channels is set to 2 to 8. Figures 1A and 1B The embodiment in which the number of branch channels is 4 is shown, and correspondingly, the number of outlets 14 is also 4. Figure 1B As shown, the branch channels may be arranged at equal intervals in the circumferential direction around the main channel.

[0031] The high temperature fuel enters the branch channel uniformly and is ejected from multiple outlets 14 into the furnace space (see Figures 6A-6D ), the fuel flow directions of the multiple fuel streams from the outlet 14 may be parallel to each other, such as Figure 1A In other words, Figure 1A As shown, the outlet 14 of the branch channel is connected to the vertical channel of the branch channel, and the vertical channel is parallel to the center line of the main channel 1.

[0032] Figure 1C FIG is a schematic cross-sectional view of a fuel injection nozzle according to another exemplary embodiment of the present invention. Figure 1C As shown, the fuel flow direction of the multiple fuel streams from the outlet 14 may have a certain angle with the axis of the main channel 1, and the angle range is 0° to 30°, that is, Figure 1C In the example, the fuel is sprayed upward at an angle. Although not shown, Figure 1C The structure shown can also have Figure 1B The cross-sectional structure shown.

[0033] In a further embodiment, swirl blades (not shown) may be provided in the branch channels to enhance the rotation of the airflow, thereby further reducing the flame stiffness, expanding the lateral diffusion of the flame, and improving the flame fullness.

[0034] By arranging multiple branch channel outlets on the top of the main channel, hot fuel can be sprayed into the furnace from multiple outlets at the same time, so that the combustion organization is changed from a single cluster of flames to multiple flame columns, which improves the combustion efficiency, enhances the flame combustion stability, and improves the uniformity of the boiler cross-sectional load.

[0035] like Figure 1A and 1C As shown, the outer side of the lower end of the blind end 12 defines a portion of the inner wall surface of the corresponding branch channel, and the outer side of the lower end of the blind end 12 is substantially flush with the outer wall surface 11 of the main channel 1.

[0036] In e.g. Figure 1A and Figure 1C In the embodiment shown, the outlet 14 of the branch channel is arranged around the main channel 1, and the fuel outlet 13 is substantially directly connected to the branch channel. In this case, the distance d1 between the center of the outlet 14 of the branch channel and the center of the main channel 1 in the transverse direction perpendicular to the center line of the main channel is in the range of 2-5 times the diameter (outer diameter) of the branch channel. Figure 1B shown.

[0037] However, a connecting channel may also be provided between the branch channel and the fuel outlet 13 . Figure 2A and Figure 2B Such an embodiment is shown. Figure 2Ais a schematic top view of a fuel nozzle according to another exemplary embodiment of the present invention, Figure 2B For the Figure 2A In an optional embodiment, the distance d2 between the center of the outlet 14 of the branch channel and the center of the main channel 1 in the transverse direction perpendicular to the center line of the main channel is greater than 2 times the diameter (outer diameter) of the branch channel. Figure 2B shown.

[0038] Reference above Figures 1A-1C Other structural descriptions can also be applied to Figure 2A-2B The structure shown will not be described in detail here.

[0039] You can also set the center wind at the fuel nozzle. Figures 3A-5C Example description.

[0040] Figure 3A FIG. 1 is a schematic cross-sectional view of a fuel injection port according to another exemplary embodiment of the present invention. Figure 3B for Figure 3A Schematic cross-sectional view of the fuel nozzle along the AA direction. Figure 3A and Figure 3B The structure shown is Figure 1A and Figure 1B The structures shown differ mainly in Figure 3A and Figure 3B In the structure shown, an air duct is provided for supplying combustion air to the fuel leaving through the outlet 14 of the branch channel. Its function is to mix the central air with the fuel to produce a partial combustion reaction before the fuel is ejected into the furnace, thereby increasing the ejection temperature of the hot fuel and the reaction rate of the hot fuel in the furnace.

[0041] like Figure 3A and Figure 3B As shown, the air duct 2 includes an air supply duct 21, a central air duct 22 and a branch air duct 23. Figure 3A and 3B As shown, the airflow ejection direction of the branch air duct 23 is consistent with the direction of the fuel entering the branch channel. The central air can be mixed into each branch channel in advance. After the central air is injected into the branch channel, it mixes with the hot fuel and reacts and then flows out from the outlet 14.

[0042] like Figure 3A and 3B As shown, the branch air duct 23 is communicated with the central air duct 22 , and at least a portion of the central air duct 22 is arranged in the main channel 1 ; at least a portion of the branch air duct 23 is arranged in the main channel 1 .

[0043] exist Figure 3BIn the embodiment, the outlet of the branch air duct 23 is arranged in the main channel and is arranged toward the corresponding fuel outlet 14. Although not shown, in an optional embodiment, the outlet of the branch air duct 23 can also be arranged in the corresponding branch channel, that is, extending through the fuel outlet 14.

[0044] Figure 4A is a schematic cross-sectional view of a fuel injection port according to yet another exemplary embodiment of the present invention. Figure 4B for Figure 4A Schematic diagram of the cross section of the fuel nozzle along the AA direction. Figure 4A As shown, an annular wind box 32 is provided below the branch channel, and the annular wind box 32 is provided with branch air ducts 33 having the same number as the branch channels. Each branch air duct 33 passes through the lower wall of the branch channel and extends into the interior of the branch channel. Figure 4A As shown, the extension direction of the branch air duct 33 in the branch channel is consistent with the fuel outflow direction of the branch channel.

[0045] like Figure 4A As shown, the air duct 3 includes an air supply pipe 31, an annular air box 32, and a branch air duct 33. Figure 4B As shown, the outlet of the branch air duct 33 is arranged at the center of the outlet 14 of the branch channel.

[0046] In an optional embodiment, the insertion height of the branch air duct 33 in the branch channel is adjustable. By adjusting the insertion height, the mixing and reaction time of the branch air duct 33 and the hot fuel can be adjusted, thereby changing the combustion rate and reaction characteristics after the hot fuel is ejected.

[0047] exist Figures 3A-4B In the illustrated embodiment, the branch air duct is disposed in the branch channel, but the present invention is not limited thereto. Figures 5A-5C Additional embodiments are shown. Figure 5A is a schematic cross-sectional view of a fuel injection port according to another exemplary embodiment of the present invention, Figure 5B for Figure 5A A schematic cross-sectional view of the fuel nozzle along the AA direction in FIG. Figure 5C for Figure 5A The fuel nozzle along Figure 5B Schematic diagram of the cross section along the BB direction.

[0048] like Figures 5A-5C As shown, each branch air duct 43 is arranged outside the main channel 1 and between adjacent branch channels in the circumferential direction. Figure 5B As shown, multiple branch channels are arranged at equal intervals in the circumferential direction, multiple branch air ducts 43 are arranged at equal intervals in the circumferential direction, each branch channel is placed between two adjacent branch air ducts in the circumferential direction, and each branch air duct is placed between two adjacent branch channels in the circumferential direction.

[0049] In an exemplary embodiment of the present invention, the fuel nozzle is a high-temperature fuel nozzle, ie, the temperature of the fuel flow entering the fuel nozzle is not less than 700°C.

[0050] Figures 6A-6D FIG. 1 is a schematic diagram of a combustion device according to an exemplary embodiment of the present invention, the combustion device comprising a fuel nozzle according to the present invention.

[0051] like Figure 6A As shown, the main channel 1 is arranged at the bottom center of the boiler. When the hot fuel flows to the top, it is ejected through 2-8 nozzles tightly surrounding the fuel channel. Figure 6A The fuel nozzle in Figure 3A However, the fuel nozzles of other embodiments may also be applied to Figure 6A middle.

[0052] exist Figure 6A In the process, the central air is fully mixed with the hot fuel and then sprayed into the furnace from the outlets 14 of the multiple branch channels. The thermal power of the nozzle is reduced, which makes it more convenient for the efficient combustion of the fuel.

[0053] like Figure 6A As shown, a secondary air device 5 is installed at the bottom of the furnace. After the hot fuel is ejected, multiple flames are formed in the middle and lower part of the furnace 6. These flames ignite and stabilize each other. The presence of multiple flames within the large cross-sectional space of the furnace increases the contact area between the fuel and air, ensuring complete fuel combustion and uniform furnace temperature distribution. The combined volume of the central and secondary air is less than the theoretical air volume for hot fuel combustion. The middle and lower part of the furnace remains in a reducing atmosphere. The HCN, NH3, and coke N in the hot fuel are easily converted to N2 below the tertiary air flow. Above the tertiary air flow, the furnace becomes an oxidizing atmosphere, ensuring complete fuel burnout.

[0054] Optionally, the multi-channel fuel nozzles can be arranged in a counter-hedge manner, or applied to boilers with top-mounted burners, or applied to horizontal pulverized coal boilers, kilns, etc., as shown in the schematic diagram. Figures 6B-6D As shown. Figures 6B-6D The fuel nozzle shown adopts Figure 1A The structure shown is shown, but the fuel injection nozzles in other embodiments can also be used.

[0055] Based on the above, the present invention proposes the following technical solutions:

[0056] 1. A fuel nozzle, comprising:

[0057] a main channel, one end of the main channel being a blind end, and a side wall of the main channel being provided with a plurality of fuel outlets near the blind end; and

[0058] A plurality of branch channels are provided, wherein the inlet of each branch channel is connected to the corresponding fuel outlet, the outlet of the branch channel is higher than the fuel outlet connected thereto, and the outlets of the plurality of branch channels are located outside the main channel.

[0059] 2. The fuel nozzle according to item 1, wherein:

[0060] The plurality of fuel outlets include two fuel outlets, and the two fuel outlets are arranged opposite to each other;

[0061] The plurality of branch channels include two branch channels, and the two branch channels are arranged around the main channel and opposite to each other on both sides of the main channel.

[0062] 3. The fuel nozzle according to item 1, wherein:

[0063] The plurality of fuel outlets include n fuel outlets, the plurality of branch channels include n branch channels, and n is a natural number greater than 2;

[0064] The n fuel outlets are arranged at equal intervals in a circumferential direction around the main channel, and the n branch channels are arranged at equal intervals in a circumferential direction around the main channel.

[0065] 4. The fuel nozzle according to item 1, wherein:

[0066] The outlet of the branch channel is communicated with the vertical channel of the branch channel, and the vertical channel is parallel to the center line of the main channel.

[0067] 5. The fuel nozzle according to item 1, wherein:

[0068] The outlet of the branch channel is communicated with the oblique channel of the branch channel, and the oblique channel extends obliquely away from the main channel.

[0069] 6. The fuel nozzle according to item 1, wherein:

[0070] The top of the blind end is higher than the outlet of the branch channel.

[0071] 7. The fuel nozzle according to 6, wherein:

[0072] The blind end has a curved outer end surface, and the top of the curved outer end surface is higher than the fuel outlet.

[0073] 8. The fuel nozzle according to item 1, wherein:

[0074] The outer side of the lower end of the blind end defines a portion of the inner wall surface of the corresponding branch channel, and the outer side of the lower end of the blind end is substantially flush with the outer wall surface of the main channel.

[0075] 9. The fuel nozzle according to item 1, wherein:

[0076] In a transverse direction perpendicular to the center line of the main channel, the size of the blind end is larger than that of the main channel, and the lower side surface of the blind end defines a portion of the inner wall surface of the corresponding branch channel.

[0077] 10. The fuel nozzle according to item 1, wherein:

[0078] The distance between the center of the outlet of the branch channel and the center of the main channel in a transverse direction perpendicular to the center line of the main channel is not less than 2 times the outer diameter of the branch channel.

[0079] 11. The fuel nozzle according to item 1, wherein:

[0080] A distance between a center of an outlet of the branch channel and a center of the main channel in a transverse direction perpendicular to a center line of the main channel is in a range of 2-5 times an outer diameter of the branch channel.

[0081] 12. The fuel nozzle according to any one of 1 to 11, wherein:

[0082] The fuel nozzle is further provided with an air duct for supplying combustion air to the fuel leaving through the outlet of the branch channel.

[0083] 13. The fuel nozzle according to 12, wherein:

[0084] The air duct includes a plurality of branch air ducts, and each branch air duct is suitable for introducing combustion air into a corresponding branch channel.

[0085] 14. The fuel nozzle according to 13, wherein:

[0086] The air duct includes a central air duct, branch air ducts communicating with the central air duct, and at least a portion of the central air duct is disposed in the main channel;

[0087] At least a portion of the branch air duct is arranged in the main channel.

[0088] 15. The fuel nozzle according to 14, wherein:

[0089] The outlet of the branch air duct is arranged in the main channel and is arranged toward the corresponding fuel outlet; or

[0090] The outlet of the branch air duct is arranged in the corresponding branch channel.

[0091] 16. The fuel nozzle according to 13, wherein:

[0092] The air duct includes a bellows arranged outside the main channel, the branch air ducts are communicated with the bellows outside the main channel, and the branch air ducts extend into corresponding branch channels.

[0093] 17. The fuel nozzle according to 16, wherein:

[0094] The air duct further includes a length adjustment device for adjusting the length of the branch air duct extending into the branch channel.

[0095] 18. The fuel nozzle according to 16, wherein:

[0096] An extension direction of the branch air duct in the branch channel is consistent with a fuel outflow direction of the branch channel.

[0097] 19. The fuel nozzle according to item 12, wherein:

[0098] The air duct includes a plurality of branch air ducts, each of which is arranged outside the main duct and between adjacent branch air ducts in a circumferential direction.

[0099] 20. The fuel nozzle according to 19, wherein:

[0100] The air duct further includes a bellows, which is arranged on the outside of the main channel, and each branch air duct is communicated with the bellows.

[0101] 21. The fuel nozzle according to claim 19, wherein:

[0102] The multiple branch channels are arranged at equal intervals in the circumferential direction, the multiple branch air ducts are arranged at equal intervals in the circumferential direction, each branch channel is placed between two adjacent branch air ducts in the circumferential direction, and each branch air duct is placed between two adjacent branch channels in the circumferential direction.

[0103] 22. The fuel nozzle according to 13 or 19, wherein:

[0104] The number of the branch air ducts corresponds to the number of the fuel outlets.

[0105] 23. The fuel nozzle according to item 1, wherein:

[0106] A swirl structure is provided in the branch channel near an outlet of the branch channel, and the swirl structure is used to rotate the fluid flowing through the swirl structure.

[0107] 24. The fuel nozzle according to any one of 1-23, wherein:

[0108] The fuel nozzle is a fuel nozzle suitable for a fuel flow having a temperature not lower than 700° C. to pass through.

[0109] 25. A combustion device comprising:

[0110] combustion space;

[0111] At least one nozzle is suitable for providing fuel into the combustion space, and the at least one nozzle comprises a fuel nozzle according to any one of 1-23.

[0112] 26. The combustion apparatus according to 25, wherein:

[0113] The combustion space is a vertical combustion space, and the fuel nozzle is arranged at the bottom, top or side of the vertical combustion space; or

[0114] The combustion space is a horizontal combustion space, and the fuel nozzle is arranged at the front of the horizontal combustion space.

[0115] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made to the embodiments and combinations of elements may be made without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A fuel nozzle for supplying fuel into a combustion space, comprising: a main channel, one end of the main channel being a blind end, a side wall of the main channel being provided with a plurality of fuel outlets near the blind end, the fuel nozzles being suitable for passing fuel having a temperature not lower than 700° C.; and Multiple branch channels, each branch channel's inlet communicates with a corresponding fuel outlet, the branch channel's outlet is higher than the fuel outlet it communicates with, and the outlets of the multiple branch channels are located outside the main channel. in: The high-temperature gas-solid fuel is suitable for being sprayed into the combustion space simultaneously in the form of multiple flame columns from the outlets of multiple branch channels.

2. The fuel nozzle according to claim 1, wherein: The plurality of fuel outlets include two fuel outlets, and the two fuel outlets are arranged opposite to each other; The plurality of branch channels include two branch channels, and the two branch channels are arranged around the main channel and opposite to each other on both sides of the main channel.

3. The fuel nozzle of claim 1 , wherein: The plurality of fuel outlets include n fuel outlets, the plurality of branch channels include n branch channels, and n is a natural number greater than 2; The n fuel outlets are arranged at equal intervals in a circumferential direction around the main channel, and the n branch channels are arranged at equal intervals in a circumferential direction around the main channel.

4. The fuel nozzle of claim 1 , wherein: The outlet of the branch channel is communicated with the vertical channel of the branch channel, and the vertical channel is parallel to the center line of the main channel.

5. The fuel nozzle of claim 1 , wherein: The outlet of the branch channel is communicated with the oblique channel of the branch channel, and the oblique channel extends obliquely away from the main channel.

6. The fuel nozzle of claim 1, wherein: The top of the blind end is higher than the outlet of the branch channel.

7. The fuel nozzle of claim 6, wherein: The blind end has a curved outer end surface, and the top of the curved outer end surface is higher than the fuel outlet.

8. The fuel nozzle of claim 1, wherein: The outer side of the lower end of the blind end defines a portion of the inner wall surface of the corresponding branch channel, and the outer side of the lower end of the blind end is substantially flush with the outer wall surface of the main channel.

9. The fuel nozzle of claim 1 , wherein: In a transverse direction perpendicular to the center line of the main channel, the size of the blind end is larger than that of the main channel, and the lower side surface of the blind end defines a portion of the inner wall surface of the corresponding branch channel.

10. The fuel nozzle of claim 1, wherein: The distance between the center of the outlet of the branch channel and the center of the main channel in a transverse direction perpendicular to the center line of the main channel is not less than 2 times the outer diameter of the branch channel.

11. The fuel nozzle of claim 10, wherein: A distance between a center of an outlet of the branch channel and a center of the main channel in a transverse direction perpendicular to a center line of the main channel is in a range of 2-5 times an outer diameter of the branch channel.

12. The fuel nozzle according to any one of claims 1 to 11, wherein: The fuel nozzle is further provided with an air duct for supplying combustion air to the fuel leaving through the outlet of the branch channel.

13. The fuel nozzle of claim 12, wherein: The air duct includes a plurality of branch air ducts, and each branch air duct is suitable for introducing combustion air into a corresponding branch channel.

14. The fuel nozzle of claim 13, wherein: The air duct includes a central air duct, branch air ducts communicating with the central air duct, and at least a portion of the central air duct is disposed in the main channel; At least a portion of the branch air duct is arranged in the main channel.

15. The fuel nozzle of claim 14, wherein: The outlet of the branch air duct is arranged in the main channel and is arranged toward the corresponding fuel outlet; or The outlet of the branch air duct is arranged in the corresponding branch channel.

16. The fuel nozzle of claim 13, wherein: The air duct includes a bellows arranged outside the main channel, the branch air ducts are communicated with the bellows outside the main channel, and the branch air ducts extend into corresponding branch channels.

17. The fuel nozzle of claim 16, wherein: The air duct further includes a length adjustment device for adjusting the length of the branch air duct extending into the branch channel.

18. The fuel nozzle of claim 16, wherein: An extension direction of the branch air duct in the branch channel is consistent with a fuel outflow direction of the branch channel.

19. The fuel nozzle of claim 12, wherein: The air duct includes a plurality of branch air ducts, each of which is arranged outside the main duct and between adjacent branch air ducts in a circumferential direction.

20. The fuel nozzle of claim 19, wherein: The air duct further includes a bellows, which is arranged on the outside of the main channel, and each branch air duct is communicated with the bellows.

21. The fuel nozzle of claim 19, wherein: The multiple branch channels are arranged at equal intervals in the circumferential direction, the multiple branch air ducts are arranged at equal intervals in the circumferential direction, each branch channel is placed between two adjacent branch air ducts in the circumferential direction, and each branch air duct is placed between two adjacent branch channels in the circumferential direction.

22. The fuel nozzle of claim 13 or 19, wherein: The number of the branch air ducts corresponds to the number of the fuel outlets.

23. The fuel nozzle of claim 1, wherein: A swirl structure is provided in the branch channel near an outlet of the branch channel, and the swirl structure is used to rotate the fluid flowing through the swirl structure.

24. A combustion device comprising: combustion space; At least one nozzle is adapted to provide fuel into the combustion space, wherein the at least one nozzle comprises a fuel nozzle according to any one of claims 1-23.

25. The combustion apparatus of claim 24, wherein: The combustion space is a vertical combustion space, and the fuel nozzle is arranged at the bottom, top or side of the vertical combustion space; or The combustion space is a horizontal combustion space, and the fuel nozzle is arranged at the front of the horizontal combustion space.

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