Outer fire cover and combustor thereof

Abstract

The invention discloses an outer burner cap, which comprises an upper burner cap, a lower burner cap, a lower burner cap and a plurality of outer burner caps, and is characterized in that the upper burner cap comprises an annular top plate and an annular side plate extending downwards from the radial inner side of the annular top plate; the lower fire cover is arranged below the annular top plate and located on the periphery of the annular side plate, an annular air cavity with a downward opening is formed between the lower fire cover and the annular side plate, an annular fire groove communicated with the annular air cavity is formed between the lower fire cover and the annular top plate, and the annular fire groove is obliquely formed in the vertical direction; and the caliber of the annular fire groove is gradually reduced along the gas outlet direction. According to the outer fire cover, airflow can be smoother, smoke is lower, and meanwhile tempering is not prone to occurring. The invention further discloses a combustor.

Description

Technical Field

[0001] The present invention relates to the technical field of burners, and in particular to an outer fire cover and a burner thereof. Background Art

[0002] There are relatively few annular slot flame shapes on the market at present. Generally, a slot is obliquely cut into an integral fire cover to a certain depth. While cutting through the fire holes, the ribs are not cut off. Due to processing limitations, generally the wall thickness of this flame shape is small and the fire slots are relatively small. Otherwise, its strength or working conditions are difficult to meet the requirements. Therefore, multiple fire slots need to be cut to make the area of the fire holes reach the design value, and such a processing method is destined to make the widths of the inner and outer sides of the fire slots the same.

[0003] Since the inclination angles of the fire slots are all the same, this causes the air flow to be intercepted when entering the fire cover, making the air flow not smooth, reducing the entrainment performance, and having a high flue gas, which is not conducive to improving the thermal efficiency. Summary of the Invention

[0004] The present invention aims to solve at least one of the problems existing in the related art to a certain extent. For this purpose, the present invention provides an outer fire cover that can make the air flow smoother, the flue gas lower, and is not prone to flashback. The present invention also provides a burner.

[0005] According to the above-provided outer fire cover, it is realized through the following technical solutions:

[0006] An outer fire cover includes: an upper fire cover including an annular top plate and an annular side plate extending downward from the radially inner side of the annular top plate; a lower fire cover disposed below the annular top plate and outside the annular side plate. An annular air cavity with a downward opening is formed between the lower fire cover and the annular side plate, and an annular fire slot communicating with the annular air cavity is formed between the lower fire cover and the annular top plate. The annular fire slot is obliquely arranged in the vertical direction, and the caliber of the annular fire slot gradually decreases along the air outlet direction.

[0007] In some embodiments, the annular fire slot has an upper slot wall surface and a lower slot wall surface arranged oppositely, and the slope of the upper slot wall surface is less than the slope of the lower slot wall surface.

[0008] In some embodiments, the inclination angle of the upper slot wall surface is 30-45°, and the inclination angle of the lower slot wall surface is 32-50°.

[0009] In some embodiments, a limiting step is provided at the bottom of the annular top plate near the annular side plate, and the limiting step constitutes the top surface of the annular air cavity.

[0010] In some embodiments, a first flame stabilizing groove is formed on the outer side wall of the lower burner cap and is located below the annular flame groove. The lower burner cap is provided with a flame stabilizing hole group located on the periphery of the annular air cavity. The upper end of the flame stabilizing hole group communicates with the first flame stabilizing groove, and the lower end penetrates through the bottom of the lower burner cap. The flame stabilizing hole group includes a plurality of outer flame stabilizing holes arranged at circumferential intervals.

[0011] In some embodiments, a second flame stabilizing groove is further formed on the outer side wall of the lower burner cap and is located between the annular flame groove and the first flame stabilizing groove. The lower burner cap is provided with a flow dividing hole group located between the annular air cavity and the flame stabilizing hole group. The upper end of the flow dividing hole group communicates with the second flame stabilizing groove, and the lower end penetrates through the bottom of the lower burner cap. The flow dividing hole group includes a plurality of inner flame stabilizing holes arranged at circumferential intervals.

[0012] In some embodiments, the diameter of the second flame stabilizing groove is larger than that of the first flame stabilizing groove, and the diameter of the inner flame stabilizing hole is larger than that of the outer flame stabilizing hole.

[0013] In some embodiments, the diameter of the first flame stabilizing groove is 0.6 - 1.5 mm, and the diameter of the second flame stabilizing groove is 0.8 - 1.5 mm.

[0014] According to the burner provided above, it is achieved through the following technical solutions:

[0015] A burner includes: an outer burner cap as described above; a distributor installed at the bottom of the outer burner cap, and the inner ring wall of which is inserted into the annular air cavity. The distributor is provided with a plurality of air inlets arranged at circumferential intervals. A premixing cavity is formed between the lower burner cap and the distributor, and the premixing cavity communicates with the air inlets, the annular air cavity and the outer flame stabilizing holes of the lower burner cap respectively.

[0016] In some embodiments, the air inlets are located directly below the annular air cavity, and an inner guiding surface is provided above the air inlets at the position on the inner cavity wall surface of the premixing cavity corresponding to the air inlets. The inner guiding surface is used to guide the air flow into the annular air cavity; or the air inlets are located radially outside the annular air cavity, and an outer guiding surface is provided above the air inlets at the position on the outer cavity wall surface of the premixing cavity corresponding to the air inlets. The outer guiding surface is used to guide the air flow to the bottom of the lower burner cap.

[0017] In some embodiments, a blocking portion extending outward is integrally formed on the radial inner side wall surface of the air inlet, and an air vent gap is left between the free end of the blocking portion and the radial outer side wall surface of the air inlet. The air vent gap is located radially outside the annular air cavity.

[0018] Compared with the prior art, the present invention has at least the following beneficial effects:

[0019] 1. The outer burner cap of the present invention forms an annular air cavity between the upper burner cap and the lower burner cap and an annular fire groove communicating with the annular air cavity. The annular fire groove is arranged obliquely in the vertical direction, and the diameter of the annular fire groove gradually decreases along the air outlet direction. Compared with the existing burner caps with the same inclination angle of the fire groove, firstly, the air flow is smoother when flowing through the annular fire groove; secondly, the flue gas can be effectively reduced, which is beneficial to reducing the requirement of the primary air coefficient of the burner, making the combustion more stable and facilitating the improvement of the thermal efficiency; thirdly, it is not easy to have flashback and can effectively reduce the extinguishing noise.

[0020] 2. By arranging a first flame stabilizing structure and a second flame stabilizing structure on the lower burner cap, with the second flame stabilizing structure located between the first flame stabilizing structure and the annular fire groove, on the one hand, the flame is made more stable and the probability of flashback is further reduced; on the other hand, the annular fire groove is shunted; thirdly, through the cooperation of the first flame stabilizing structure, the second flame stabilizing structure and the annular fire groove, the problems of large combustion noise and abnormal noise are effectively solved, so that the outer burner cap can be applied to two different types of burners, namely, the forced-draft type and the non-forced-draft type. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic structural diagram of the outer burner cap in Embodiment 1 of the present invention;

[0022] Figure 2 is a cross-sectional view of the outer burner cap in Embodiment 1 of the present invention;

[0023] Figure 3 is the explosion of the burner in Embodiment 1 of the present invention Figure 1 ;

[0024] Figure 4 is the explosion of the burner in Embodiment 1 of the present invention Figure 2 ;

[0025] Figure 5 is a schematic structural diagram of the burner in Embodiment 1 of the present invention;

[0026] Figure 6 is the cross-section of the burner in Embodiment 1 of the present invention Figure 1 ;

[0027] Figure 7 is the cross-section of the burner in Embodiment 1 of the present invention Figure 2 ;

[0028] Figure 8 is a cross-sectional view of the outer burner cap in Embodiment 2 of the present invention;

[0029] Figure 9 is a cross-sectional view of the burner in Embodiment 3 of the present invention;

[0030] Figure 10 is a cross-sectional view of the flame divider in Embodiment 3 of the present invention;

[0031] Figure 11 It is a cross-sectional view of the burner in Embodiment 4 of the present invention.

[0032] In the figure: 1 - upper fire cover, 11 - annular top plate, 111 - pilot holes, 112 - upper groove wall surface, 113 - limiting step, 12 - annular side plate;

[0033] 2 - lower fire cover, 211 - annular gas chamber, 212 - annular fire trough, 22 - lower groove wall surface, 231 - first flame stabilizing trough, 232 - outer flame stabilizing holes, 241 - second flame stabilizing trough, 242 - inner flame stabilizing holes, 25 - fixing column;

[0034] 3 - flame distributor, 311 - inner ring wall, 312 - outer ring wall, 32 - air inlet, 33 - premixing chamber, 331 - inner flow guiding surface, 332 - outer flow guiding surface, 341 - blocking part, 342 - ventilation gap, 35 - air passage, 36 - connecting hole. Detailed implementation manners

[0035] The following embodiments are used to illustrate the present invention, but the present invention is not limited by these embodiments. Modifying the specific implementation manners of the present invention or making equivalent replacements for some technical features without departing from the spirit of the present invention scheme shall be covered within the scope of the technical solution claimed by the present invention.

[0036] Embodiment 1

[0037] Referring to Figure 1-2 This embodiment provides an outer fire cover. The outer fire cover is a split fire cover, which includes an upper fire cover 1 and a lower fire cover 2. The upper fire cover 1 includes an annular top plate 11 and an annular side plate 12 extending downward from the radially inner side of the annular top plate 11. In this embodiment, the annular top plate 11 and the annular side plate 12 are integrally formed. A pilot part is provided on the annular top plate 11, and the pilot part includes a plurality of pilot holes 111 arranged at intervals. The lower fire cover 2 is arranged below the annular top plate 11 and outside the annular side plate 12. An annular gas chamber 211 with a downward opening is formed between the lower fire cover 2 and the annular side plate 12, and an annular fire trough 212 with an opening toward the radially outer side is formed between the lower fire cover 2 and the annular top plate 11. The annular fire trough communicates with the annular gas chamber 211 and the pilot part respectively, so as to facilitate the flame to ignite the outer ring gas ejected from the annular fire trough 212 through the pilot part. After this part of the outer ring gas is ignited, a complete ring-shaped seam fire is formed, and the flame is stable and beautiful.

[0038] In this embodiment, the annular fire trough 212 is arranged obliquely in the vertical direction, and the caliber of the annular fire trough 212 gradually decreases along the air outlet direction. In this way, on the one hand, the air flow is smoother when flowing through the annular fire trough, and on the other hand, the flue gas can be effectively reduced, which is conducive to reducing the requirement of the primary air coefficient of the burner. The air volume requirement of the forced-draft burner is low, the combustion is more stable, which is convenient for improving the thermal efficiency. Thirdly, it is not easy to have flashback, and the quenching noise can be effectively reduced.

[0039] Reference Figure 2 , the annular fire trough 212 has an upper trough wall surface 112 and a lower trough wall surface 22 arranged oppositely, wherein the upper trough wall surface 112 is the radially outer end of the bottom surface of the annular top plate 11, and the lower trough wall surface 22 is the top surface of the upper fire cap. Specifically, the slope of the lower trough wall surface 22 is greater than that of the upper trough wall surface 112, so that the inclination angles of the upper trough wall surface 112 and the lower trough wall surface 22 are different, so that the air flow will not be intercepted, ensuring smoother air flow and effectively reducing flue gas. In this embodiment, the inclination angle of the upper trough wall surface 112 is 30-45°, preferably 40°, and the inclination angle of the lower trough wall surface 22 is 32-50°, preferably 42°. In this way, on the one hand, the flue gas is reduced to avoid high flue gas caused by a large inclination angle, and on the other hand, it is ensured that the inlet area of the annular fire trough 212 is slightly larger than its outlet area, so that the annular fire trough can play a role in reducing the probability of flashback and quenching noise. It should be noted that when the area difference between the inlet and the outlet of the annular fire trough 212 is too large, which is equivalent to the depth of the annular fire trough not working, there will be a large quenching noise when turning off the fire in the case of flashback limit gas or low pressure.

[0040] In addition, a limiting step 113 is arranged at the bottom of the annular top plate 11 close to the annular side plate 12. The limiting step 113 is formed by the radially inner side of the bottom of the annular top plate 11, and the limiting step 113 forms the cavity top surface of the annular air cavity 211, which is used to cooperate and abut with the inner wall of the distributor ring of the burner, so as to stably and reliably place the upper fire cap 1 on the top of the distributor of the burner.

[0041] Reference Figure 1-2, Further, a first flame stabilizing groove 231 is provided on the outer side wall of the lower fire cover 2 below the annular fire groove 212. The first flame stabilizing groove 231 is located below the annular fire groove, and the first flame stabilizing groove 231 is arranged to incline upward from inside to outside; the lower fire cover 2 is provided with a flame stabilizing hole group outside the annular air cavity 211. The upper end of the flame stabilizing hole group communicates with the first flame stabilizing groove 231, and the lower end penetrates through the bottom of the lower fire cover 2. The flame stabilizing hole group includes a plurality of outer flame stabilizing holes 232 arranged at circumferential intervals, and the outer flame stabilizing holes 232 are arranged vertically or inclined in the vertical direction. Thus, the flame stabilizing hole group and the first flame stabilizing groove 231 together form a first flame stabilizing structure, which is beneficial to improving the flame stability and combustion thermal efficiency. Since the flame stabilizing hole group is separated from the annular air cavity 211, this prevents the interference of the gas at the inlet of the flame stabilizing hole group and the inlet of the annular fire groove, which is beneficial to ensuring the uniformity and beauty of the flame of the annular slit fire.

[0042] Reference Figure 1-2 , Even further, a second flame stabilizing groove 241 is further provided on the outer side wall of the lower fire cover 2 between the annular fire groove 212 and the first flame stabilizing groove 231. The second flame stabilizing groove is arranged to incline upward from inside to outside; the lower fire cover 2 is further provided with a flow dividing hole group between the annular air cavity 211 and the flame stabilizing hole group. The upper end of the flow dividing hole group communicates with the second flame stabilizing groove 241, and the lower end penetrates through the bottom of the lower fire cover 2. The flow dividing hole group includes a plurality of inner flame stabilizing holes 242 arranged at circumferential intervals, and the inner flame stabilizing holes 242 are arranged to incline upward from inside to outside. Thus, the flow dividing hole group and the second flame stabilizing groove 241 together form a second flame stabilizing structure. On the one hand, it is further beneficial to strengthen the flame stability and further reduce the probability of flashback. On the other hand, it realizes the flow division of the gas at the annular fire groove, prevents the gas outlet speed at the annular fire groove from being too fast. On the third hand, through the cooperation of the first flame stabilizing structure, the second flame stabilizing structure and the annular fire groove, the problems of large combustion noise and abnormal noise are effectively solved, so that the outer fire cover can be applicable to two different burners, namely the forced-draft type and the non-forced-draft type.

[0043] Specifically, the diameter H2 of the second flame stabilizing groove 241 is larger than the diameter H1 of the first flame stabilizing groove 231, and the diameter of the inner flame stabilizing hole 242 is larger than the diameter of the outer flame stabilizing hole 232. In this embodiment, the diameter H1 of the first flame stabilizing groove 231 is 0.6 - 1.5 mm, preferably 0.8 mm, and the diameter H2 of the second flame stabilizing groove 241 is 0.8 - 1.5 mm, preferably 1 mm. Both the outer flame stabilizing hole and the inner flame stabilizing hole are circular fire holes, which are convenient for controlling the gas outlet volume, have strong manufacturability, and are stable and reliable in processing.

[0044] Reference Figure 1-2 , Further, a plurality of fixing columns 25 extending downward are provided at circumferential intervals on the bottom of the lower fire cover 2. The fixing columns 25 are used for connecting and fixing with the flame divider of the burner, so as to stably and reliably install the lower fire cover on the outer ring wall of the flame divider.

[0045] Reference Figure 3-7, this embodiment also provides a burner, which is a forced-draft burner or a non-forced-draft burner, and includes an outer fire cap and a gas distributor 3 as described above. The gas distributor 3 is installed at the bottom of the outer fire cap, and its inner ring wall 311 is inserted into the annular gas chamber 211, and the top of the inner ring wall 311 abuts against the limiting step of the upper fire cap 1. Specifically, at least part of the upper fire cap 1 is installed on the top of the inner ring wall 311 of the gas distributor 3, and at least part of the lower fire cap 2 is installed on the top of the outer ring wall 312 of the gas distributor 3.

[0046] The gas distributor 3 is provided with a plurality of air inlets 32 arranged at circumferentially uniform intervals. A premixing chamber 33 is formed between the lower fire cap 2 and the gas distributor 3. The premixing chamber 33 communicates with the air inlets 32, the annular gas chamber 211, and the outer flame stabilizing holes 232 of the lower fire cap 2 respectively. Thus, under the action of the gas distributor 3, the gas distribution uniformity is improved, making the flame of the outer fire cap more uniform and beautiful.

[0047] In this embodiment, the air inlets 32 are arranged radially outside the annular gas chamber 211, so that the outlet of the air inlets 32 is staggered from the inlet of the annular gas chamber 211, effectively preventing the outer ring gas from flowing straight up from the air inlets 32 to the root of the annular fire trough 212, which is beneficial to reducing the air flow velocity at the annular fire trough, thereby making the flame of the outer fire cap more uniform. In addition, the air inlets 32 are located radially outside the bottom surface of the premixing chamber 33. An outer guiding surface 332 is provided at the position of the outer wall surface of the premixing chamber 33 corresponding to the air inlets 32 and above the air inlets 32. The outer guiding surface 332 is an outer inclined surface extending upward and toward the inside of the premixing chamber, and is used to guide the air flow to the bottom of the lower fire cap 2. In this way, the air flow quickly flows into the premixing chamber through the outer guiding surface. On the one hand, it avoids the air flow directly hitting the root of the annular fire trough, and on the other hand, it makes the air flow buffered, ensuring a more uniform pressure distribution in the premixing chamber, and further making the flame of the outer fire cap more uniform.

[0048] Reference Figure 4-7 , the gas distributor 3 is provided with a plurality of air channels 35 located below the premixing chamber 33 and arranged at circumferential intervals. The air channels 35 and the air inlets 32 are arranged in a staggered manner along the circumferential direction of the gas distributor 3, so as to realize supplementing the secondary air required for combustion to the burner through the air channels 35. In addition, a plurality of fixing columns 25 extending downward into the premixing chamber 33 are provided at circumferential intervals at the bottom of the lower fire cap 2. Connecting holes 36 are opened at the positions of the bottom surface of the premixing chamber 33 corresponding to the fixing columns. During installation, a connecting piece (such as a screw) passes through the connecting holes 36 from bottom to top and is tightly connected to the fixing columns, so that the lower fire cap 2 and the gas distributor 3 are connected as a whole.

[0049] Embodiment 2

[0050] Reference Figure 8, the difference between this embodiment and Embodiment 1 lies in the specific structure of the lower fire cover 2. In this embodiment, the lower fire cover 2 only has the first flame stabilizing structure, that is, the second flame stabilizing structure of the lower fire cover 2 is omitted, so that the overall structure of the lower fire cover 2 is simpler, more convenient for rapid processing and forming, and the manufacturing cost is lower. At this time, the outer fire cover is only applicable to non-blast burners.

[0051] Embodiment 3

[0052] Reference Figure 9-10 , the difference between this embodiment and Embodiment 1 or 2 lies in that a blocking portion 341 extending outward is integrally formed on the radial inner side wall surface of the air inlet 32, and a ventilation gap 342 is left between the free end of the blocking portion 341 and the radial outer side wall surface of the air inlet 32. The ventilation gap 342 is located radially outside the annular gas chamber 211. When the outer ring gas flows upward and passes through the added blocking portion 341, the flow direction is bent to form a buffer, and then it flows upward through the smaller ventilation gap 342 into the larger premixing chamber 33, so that the pressure in the distributor 3 is more uniform.

[0053] Therefore, by adding the blocking portion 341 at the air inlet 32, the air flow is made to deflect more outward, preventing the outer ring gas from directly flushing the root of the annular fire trough, which is beneficial to improving the gas distribution effect, making the flame more stable, and at the same time beneficial to reducing the whistling sound and flue gas, and is more applicable to blast burners.

[0054] Embodiment 4

[0055] Reference Figure 11 , the difference between this embodiment and Embodiment 1 or 2 lies in that the installation position of the air inlet 32 is different, and the outer guiding surface is changed to an inner guiding surface. In this embodiment, the air inlet 32 is located directly below the annular gas chamber 211, and an inner guiding surface 331 located above the air inlet 32 is provided at the position of the inner cavity wall surface of the premixing chamber 33 corresponding to the air inlet 32. The inner guiding surface 331 is an inner inclined surface that slopes upward and toward the inside of the premixing chamber 33, and is used to guide the air flow into the annular gas chamber 211, so as to facilitate quickly guiding the air flow flowing out of the air inlet 32 into the annular gas chamber.

[0056] The above are only some embodiments of the present invention. For those of ordinary skill in the art, without departing from the inventive concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. An external fire cover, characterized in that: include: The upper fire cover (1) comprises an annular top plate (11) and an annular side plate (12) extending downward from the radial inner side of the annular top plate (11); A lower fire cover (2) is arranged below the annular top plate (11) and located outside the annular side plate (12); an annular air cavity (211) opening downward is formed between the lower fire cover (2) and the annular side plate (12); an annular fire groove (212) communicating with the annular air cavity (211) is formed between the lower fire cover (2) and the annular top plate (11); the annular fire groove (212) is arranged obliquely in the vertical direction, and the diameter of the annular fire groove (212) gradually decreases along the gas outlet direction.

2. An external fire cover according to claim 1, characterized in that: The annular fire groove (212) comprises an upper groove wall surface (112) and a lower groove wall surface (22) which are arranged opposite to each other, and the slope of the upper groove wall surface (112) is smaller than the slope of the lower groove wall surface (22).

3. An external fire cover according to claim 2, characterized in that: The inclination angle of the upper groove wall surface (112) is 30 to 45 degrees, and the inclination angle of the lower groove wall surface (22) is 32 to 50 degrees.

4. An external fire cover according to claim 1, characterized in that: A limiting step (113) is provided at the bottom of the annular top plate (11) and is arranged close to the annular side plate (12), and the limiting step (113) constitutes the cavity top surface of the annular air cavity (211).

5. The outer fire cover according to claim 1, characterized in that: A first flame stabilizing groove (231) located below the annular fire groove (212) is provided on the outer wall of the lower fire cover (2), and the lower fire cover (2) is provided with a flame stabilizing hole group located outside the annular air cavity (211), the upper end of the flame stabilizing hole group is connected to the first flame stabilizing groove (231), and the lower end passes through the bottom of the lower fire cover (2), wherein the flame stabilizing hole group includes a plurality of outer flame stabilizing holes (232) arranged circumferentially at intervals.

6. An external fire cover according to claim 5, characterized in that: A second flame stabilizing groove (241) is also provided on the outer wall of the lower fire cover (2) and is located between the annular fire groove (212) and the first flame stabilizing groove (231); the lower fire cover (2) is provided with a diverter hole group located between the annular air cavity (211) and the flame stabilizing hole group; the upper end of the diverter hole group is connected to the second flame stabilizing groove (241), and the lower end passes through the bottom of the lower fire cover (2); wherein the diverter hole group includes a plurality of inner flame stabilizing holes (242) arranged circumferentially at intervals.

7. An external fire cover according to claim 6, characterized in that: The caliber of the second flame stabilizing groove (241) is greater than the caliber of the first flame stabilizing groove (231), and the diameter of the inner flame stabilizing hole (242) is greater than the diameter of the outer flame stabilizing hole (232).

8. An external fire cover according to claim 7, characterized in that: The caliber of the first flame stabilizing groove (231) is 0.6-1.5 mm, and the caliber of the second flame stabilizing groove (241) is 0.8-1.5 mm.

9. A burner, characterized in that: include: An external fire cover as claimed in any one of claims 1 to 8; The ignition divider (3) is installed at the bottom of the outer fire cover and its inner ring wall (311) is inserted into the annular air cavity (211). The ignition divider (3) is provided with a plurality of air inlets (32) arranged at intervals in the circumferential direction. A premixing chamber (33) is formed between the lower fire cover (2) and the ignition divider (3). The premixing chamber (33) is respectively connected to the air inlet (32), the annular air cavity (211) and the outer flame stabilizing hole (232) of the lower fire cover (2).

10. A burner according to claim 9, characterized in that: The air inlet (32) is located directly below the annular air cavity (211), and an inner guide surface (331) located above the air inlet (32) is provided on the inner wall of the premixing cavity (33) at a position corresponding to the air inlet (32), and the inner guide surface (331) is used to guide the airflow into the annular air cavity (211); or The air inlet (32) is located radially outside the annular air cavity (211), and an outer guide surface (332) located above the air inlet (32) is provided at a position on the outer cavity wall of the premixing cavity (33) corresponding to the air inlet (32), and the outer guide surface (332) is used to guide the airflow to the bottom of the lower fire cover (2).

11. A burner according to claim 9 or 10, characterized in that: A blocking portion (341) extending outward is integrally formed on the radial inner wall surface of the air inlet (32), and a ventilation gap (342) is left between the free end of the blocking portion (341) and the radial outer wall surface of the air inlet (32), and the ventilation gap (342) is located radially outside the annular air cavity (211).

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