Dynamic and static pressure mixed gas radial bearing

Abstract

The invention relates to a dynamic and static pressure mixed gas radial bearing, and belongs to the technical field of air bearings. The shaft sleeve is sleeved with the bearing seat, a limiting part is arranged outside the shaft sleeve, and a limiting groove is correspondingly formed in the inner wall of the bearing seat; in the radial direction, the bump foil assemblies are arranged between the shaft sleeve and the bearing seat, and in the circumferential direction, the bump foil assemblies are arranged between the limiting parts at intervals; a plurality of first air inlet holes are formed in the bottom of the limiting groove, a plurality of second air inlet holes are formed in the limiting part, and the first air inlet holes correspond to the second air inlet holes in position. According to the design, the integrity of the bump foil assembly can be guaranteed, the structure is simple, machining is convenient, and mounting and dismounting are more convenient. When the speed of the rotor is low, the static pressure gas forms a gas film, and the bearing capacity of the dynamic and static pressure mixed gas radial bearing is enhanced. When the rotating speed of the rotor is high, dynamic pressure can be generated on the basis of static pressure, and the dynamic pressure and static pressure mixed gas radial bearing has larger bearing capacity due to superposition of the dynamic pressure and the static pressure.

Description

Technical Field

[0001] The invention relates to a dynamic and static pressure mixed gas radial bearing, belonging to the technical field of air foil bearings. Background Art

[0002] A foil gas bearing is a sliding bearing that uses gas as a lubricant, often air. Gas bearings can be divided into hydrodynamic gas bearings, hydrostatic gas bearings, and hydrodynamic-hydrostatic mixed gas bearings based on the principle of load-bearing capacity. Hydrodynamic gas bearings do not require external air supply and suspend the rotor through the dynamic pressure effect generated by the high-speed rotation of the rotor. However, hydrodynamic gas bearings have poor stability at high speeds and can only provide limited load-bearing capacity, which restricts their wider application. Hydrostatic gas bearings use external air supply to deliver high-pressure gas between the top foil of the bearing and the rotor, thereby creating an air film that suspends the rotor. However, hydrostatic gas bearings have low load-bearing capacity and consume a lot of hydrostatic gas.

[0003] Combining a gas dynamic bearing with a gas static bearing to form a dynamic and static gas bearing effectively compensates for the low load-bearing capacity of the dynamic gas bearing. In existing dynamic and static gas bearing structures, the corrugated foil is located between the shaft sleeve and the bearing seat. The corrugated foil is typically equipped with a ventilation duct connected to an external high-pressure gas source. This design and installation are relatively complex. Furthermore, during use, the corrugated foil is squeezed by the gas film and moves in a circular direction. This existing ventilation duct design inevitably affects the normal operation of the corrugated foil. Summary of the Invention

[0004] In response to the deficiencies in the prior art, the present invention provides a dynamic-static pressure mixed gas radial bearing, in which a sleeve is mounted inside the bearing seat, and at least two limiting portions are provided on the outside of the sleeve, and a corresponding limiting groove is provided on the inner wall of the bearing seat; an external high-pressure gas source enters the gap between the rotor and the sleeve through a first air inlet hole provided on the bearing seat, a second air inlet hole on the sleeve, and a third air inlet hole. This design can ensure the integrity of the wave foil assembly, has a simple structure, is convenient for processing, installation, and disassembly. When the rotor speed is low, the static pressure gas forms an air film, which can reduce friction power consumption and enhance the bearing capacity of the bearing. When the rotor speed increases to a certain value, the bearing will generate dynamic pressure on the basis of the static pressure. The superposition of dynamic pressure and static pressure makes the dynamic-static pressure mixed gas radial bearing have a greater bearing capacity.

[0005] The technical solution of the present invention is: A dynamic and static pressure mixed gas radial bearing, comprising a bearing seat, a shaft sleeve and a plurality of corrugated foil assemblies; The shaft sleeve is sleeved inside the bearing seat, and at least two limiting parts are provided on the outside of the shaft sleeve, and the inner wall of the bearing seat is correspondingly provided with limiting grooves; In the radial direction, the corrugated foil assembly is arranged between the shaft sleeve and the bearing seat, and in the circumferential direction, the corrugated foil assembly is arranged between the limiting parts at intervals; A plurality of first air inlet holes are provided at the bottom of the limiting groove, a plurality of second air inlet holes are provided on the limiting portion, and the bearing is further provided with an air inlet joint, which is connected to the first air inlet hole and the second air inlet hole; The shaft sleeve is also provided with a third air inlet hole, and the second air inlet hole is communicated with the third air inlet hole.

[0006] According to a preferred embodiment of the present invention, the bump foil assembly includes a bottom foil, the inner side of the bottom foil is provided with one or more single-layer bump foils along the axial direction, and one end of the single-layer bump foil is a fixed end, and the other end of the single-layer bump foil is a free end; Alternatively, one or more double-layer corrugated foils are arranged on the inner side of the bottom foil in the axial direction, and one end of the double-layer corrugated foil is a fixed end, and the other end of the double-layer corrugated foil is a free end.

[0007] Preferably, according to the present invention, the double-layer corrugated foil includes a first corrugated foil and a second corrugated foil stacked together, and the second corrugated foil and the first corrugated foil are stacked on the bottom foil from inside to outside, and the two ends of the first corrugated foil are fixed together with the two ends of the second corrugated foil.

[0008] According to the preferred embodiment of the present invention, the first corrugated foil includes a plurality of first circular arcs and second circular arcs connected in sequence, and the radius of the first circular arc is greater than the radius of the second circular arc; The second corrugated foil includes a plurality of third circular arcs and fourth circular arcs connected in sequence. The third circular arc has the same structure as the second circular arc, and the fourth circular arc has the same structure as the first circular arc.

[0009] Preferably, according to the present invention, a first connecting portion is set between the first arc and the second arc, and a second connecting portion is set between the third arc and the fourth arc; and the first arc is overlapped on the upper part of the third arc and the second connecting portions on both sides of the third arc, and the second arc and the first connecting portions on both sides of the second arc are overlapped on the upper part of the fourth arc.

[0010] Preferably, according to the present invention, the aperture of the first air inlet hole is larger than the aperture of the second air inlet hole, and the aperture of the second air inlet hole is larger than the aperture of the third air inlet hole.

[0011] Preferably, according to the present invention, the air inlet connector passes through the first air inlet hole, and the end of the air inlet connector is threadedly connected to the inner wall of the second air inlet hole.

[0012] Preferably, according to the present invention, a rear end cover is provided at one end of the bearing seat, and the rear end cover is fixed to the bearing seat by bolts. A retaining ring is provided at the other end of the bearing seat for limiting the corrugated foil assembly in the axial direction.

[0013] Preferably, according to the present invention, two second air inlet holes are provided on the limiting portion, a ventilation groove is opened on the bottom surface of the limiting portion, and the ventilation groove is connected to the adjacent second air inlet holes, thereby diverting a part of the external high-pressure air source to the ventilation groove; at least one first heat dissipation groove is provided on one side of the ventilation groove.

[0014] According to a preferred embodiment of the present invention, a second heat dissipation slot is further provided on one side of the air outlet end of the second air inlet, and both the first heat dissipation slot and the second heat dissipation slot are provided on a side of the stopper portion close to the fixed end of the double-layer corrugated foil or the single-layer corrugated foil. The first heat dissipation slot and the second heat dissipation slot are used to dissipate heat from the corrugated foil assembly.

[0015] The beneficial effects of the present invention are: 1. In the present invention, the bump foil assembly adopts a split design, with a limiting portion used to limit the bump foil assembly in the circumferential direction, a shaft sleeve and a bearing seat used to limit the assembly in the radial direction, and a retaining ring and a rear end cover respectively provided in the front and rear directions for limiting the assembly.

[0016] 2. The first air inlet hole on the limit groove, the second air inlet hole on the limit part, and the third air inlet hole on the sleeve form an air inlet channel, eliminating the interference of traditional ventilation ducts on the movement of the bump foil, which is conducive to the stable operation of the bump foil assembly. The high-pressure gas source enters the gap between the rotor and the dynamic and static pressure mixed gas radial bearing through the air inlet channel. When the rotor speed is low, the static pressure gas forms an air film, which can reduce friction power consumption and enhance the load-bearing capacity of the dynamic and static pressure mixed gas radial bearing. When the rotor speed increases to a certain value, the dynamic and static pressure mixed gas radial bearing will generate dynamic pressure on the basis of static pressure. The synergistic effect of dynamic pressure and static pressure makes the dynamic and static pressure mixed gas radial bearing have a greater load-bearing capacity.

[0017] 3. When a double-layer corrugated foil structure is adopted, the alternating lamination design of large arcs and small arcs in the double-layer corrugated foil structure enhances the elastic support and damping of the corrugated foil structure, further improving the bearing capacity of the dynamic and static pressure mixed gas radial bearing.

[0018] 4. A ventilation groove, a first heat dissipation groove and a second heat dissipation groove are provided inside the limiting part, which can divert a small amount of external high-pressure gas into the installation space of the bump foil assembly, thereby improving the heat dissipation effect of the bump foil assembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic structural diagram of the dynamic and static pressure mixed gas radial bearing provided by the present invention.

[0020] Figure 2 This is a schematic diagram of the explosion of the dynamic and static pressure mixed gas radial bearing provided by the present invention.

[0021] Figure 3 This is a structural schematic diagram of the bearing seat provided by the present invention.

[0022] Figure 4 This is a schematic structural diagram of the shaft sleeve provided by the present invention.

[0023] Figure 5 This is a view of the dynamic and static pressure mixed gas radial bearing provided by the present invention.

[0024] Figure 6 for Figure 5 Schematic diagram of the cross section along the AA direction.

[0025] Figure 7 This is a schematic structural diagram of a corrugated foil assembly with a double-layer corrugated foil structure provided by the present invention.

[0026] Figure 8 This is a schematic cross-sectional view of a single double-layer corrugated foil provided by the present invention.

[0027] Figure 9 This is a schematic structural diagram of the limiting portion provided by the present invention.

[0028] 1. Bearing seat, 2. Bushing, 3. Corrugated foil assembly, 4. Limiting part, 5. Limiting groove, 6. First air inlet hole, 7. Second air inlet hole, 8. Third air inlet hole, 9. Bottom foil, 10. Double-layer corrugated foil, 11. First corrugated foil, 12. Second corrugated foil, 13. First arc, 14. Second arc, 15. Third arc, 16. Fourth arc, 17. First connecting part, 18. Second connecting part, 19. Inlet joint, 20. Rear end cover, 21. Retaining ring, 22. Bolt, 23. Ventilation groove, 24. Second heat dissipation slot, 25. First heat dissipation slot. DETAILED DESCRIPTION

[0029] Several embodiments of the present application will be disclosed below with diagrams to clearly and completely describe the technical solution of the present invention, which constitute a part of the present application. The drawings in the specification are used to provide a further understanding of the present invention. The schematic embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0030] It should be noted that unless the directions are defined separately, the directions such as up, down, left, and right mentioned in this document are based on the embodiments of this application. Figure 2 The directions of up, down, left, and right shown are used as the reference. If the specific posture changes, the directional indication will also change accordingly. The terms "first," "second," and similar terms used in this application do not indicate any order, quantity, or importance, but are simply used to distinguish different components. In addition, in various embodiments of the present disclosure, the same or similar reference numerals represent the same or similar components.

[0031] In the present invention, unless otherwise specified or limited, the terms "connection" and "fixation" should be understood in a broad sense. For example, "connection" can refer to a fixed connection, a detachable connection, or an integral connection, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0032] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in this field can implement it. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0033] Example 1 This embodiment provides a dynamic and static pressure mixed gas radial bearing, such as Figure 1 、 Figure 2 、 Figure 3 and Figure 4 As shown, it includes a bearing seat 1, a shaft sleeve 2 and several foil assemblies 3; The shaft sleeve 2 is mounted inside the bearing seat 1, and at least two limiting portions 4 are provided on the outside of the shaft sleeve 2, and a limiting groove 5 is provided on the inner wall of the bearing seat 1 accordingly; specifically, two, three, four or more limiting portions 4 can be provided according to needs. The drawings of this patent illustrate the provision of four limiting portions 4 as an example.

[0034] In the radial direction, the bump foil assembly 3 is arranged between the shaft sleeve 2 and the bearing seat 1, and in the circumferential direction, the bump foil assembly 3 is arranged at intervals between the limit parts 4; the bump foil assembly 3 forms an unclosed circular ring along the circumferential direction, and the adjacent limit parts 4 provide space for the bump foil assembly 3 to move along the circumferential direction; when the air film squeezes the bump foil assembly 3, the bump foil assembly 3 will be flattened to a certain extent.

[0035] A plurality of first air inlet holes 6 are provided at the bottom of the limiting groove 5, a plurality of second air inlet holes 7 are provided on the limiting portion 4, and the shaft sleeve 2 is further provided with an air inlet connector 19, which connects the first air inlet holes 6 and the second air inlet holes 7; The shaft sleeve 2 is further provided with a third air inlet hole 8 , and the second air inlet hole 7 is communicated with the third air inlet hole 8 .

[0036] The bearing seat 1 is provided with a plurality of first air inlet holes 6 along the axial direction of the radial bearing. The embodiment is described by taking two first air inlet holes 6 as an example. Similarly, the number of the second air inlet holes 7 and the third air inlet holes 8 is the same as that of the first air inlet holes 6.

[0037] The installation and working process of the above-mentioned dynamic and static pressure mixed gas radial bearing is as follows: The corrugated foil assembly 3 and the shaft sleeve 2 are sequentially mounted on the inner side of the bearing seat 1 , and an external high-pressure gas source is connected to the air inlet end of the air inlet connector 19 .

[0038] High-pressure gas output from the outlet of the inlet connector 19 enters the gap between the dynamic-static mixed gas radial bearing and the rotor. For low-speed rotors, the high-pressure gas source forms an air film between the dynamic-static mixed gas radial bearing and the rotor, supporting the rotor's suspension. When the rotor reaches a certain speed, the dynamic-static mixed gas radial bearing generates dynamic pressure on top of the static pressure. The superposition of dynamic and static pressure gives the dynamic-static mixed gas radial bearing greater load-bearing capacity.

[0039] Example 2 This embodiment provides a dynamic and static pressure mixed gas radial bearing, which differs from the first embodiment in that: The bump foil assembly 3 includes a bottom foil 9. A single-layer bump foil is disposed on the inner side of the bottom foil 9 in the axial direction. One end of the single-layer bump foil is a fixed end fixed to the bottom foil 9, and the other end of the single-layer bump foil is a free end. Alternatively, one or more double-layered bump foils 10 are arranged on the inner side of the bottom foil 9 along the axial direction, and one end of the double-layered bump foil 10 is a fixed end fixed on the bottom foil 9 , and the other end of the double-layered bump foil 10 is a free end.

[0040] When only one single-layer corrugated foil or double-layer corrugated foil 10 is provided, the single-layer corrugated foil or double-layer corrugated foil 10 is a whole structure; when multiple single-layer corrugated foils or double-layer corrugated foils 10 are provided, the single-layer corrugated foil or double-layer corrugated foil 10 is sequentially provided on the inner side of the bottom foil 9 .

[0041] Example 3 This embodiment provides a dynamic and static pressure mixed gas radial bearing, which differs from the second embodiment in that: like Figure 5 、 Figure 7 and Figure 8 As shown, the double-layer corrugated foil 10 includes a first corrugated foil 11 and a second corrugated foil 12 stacked together, and the second corrugated foil 12 and the first corrugated foil 11 are stacked sequentially from the inside to the outside on the bottom foil 9. The two ends of the first corrugated foil 11 and the two ends of the second corrugated foil 12 are fixed together.

[0042] Example 4 This embodiment provides a dynamic and static pressure mixed gas radial bearing, which differs from the third embodiment in that: like Figure 5 、 Figure 7 and Figure 8 As shown, the first corrugated foil 11 includes a plurality of first circular arcs 13 and second circular arcs 14 connected in sequence, and the radius of the first circular arc 13 is greater than the radius of the second circular arc 14; The second bump foil 12 includes a plurality of third arcs 15 and fourth arcs 16 connected in sequence. The third arc 15 has the same structure as the second arc 14 , and the fourth arc 16 has the same structure as the first arc 13 .

[0043] Example 5 This embodiment provides a dynamic and static pressure mixed gas radial bearing, which differs from the fourth embodiment in that: like Figure 7 and Figure 8 As shown, a first connecting portion 17 is provided between the first arc 13 and the second arc 14, and a second connecting portion 18 is provided between the third arc 15 and the fourth arc 16; and the first arc 13 is overlapped on the third arc 15 and the second connecting portion 18 on both sides of the third arc 15, and the second arc 14 and the first connecting portion 17 on both sides of the second arc 14 are overlapped on the upper part of the fourth arc 16.

[0044] When the air film squeezes the double-layer corrugated foil 10, the first corrugated foil 11 and the second corrugated foil 12 can bear the air film pressure from two directions. Under the action of the first connecting part 17 and the second connecting part 18, the interaction between the various structures of the double-layer corrugated foil 10 forms a gradient support, so that the air bearing can withstand a larger load.

[0045] Example 6 This embodiment provides a dynamic and static pressure mixed gas radial bearing, which differs from the first embodiment in that: like Figure 3 、 Figure 4 and Figure 6 As shown, the aperture of the first air inlet hole 6 is larger than that of the second air inlet hole 7. The aperture of the second air inlet hole 7 is larger than that of the third air inlet hole 8.

[0046] When the rotor rotates, the sleeve 2 will move along the circumferential direction. Such an arrangement can provide space for the sleeve 2 to move along the circumference.

[0047] Example 7 This embodiment provides a dynamic and static pressure mixed gas radial bearing, which differs from the first embodiment in that: The air inlet connector 19 passes through the first air inlet hole 6 , and a distal end of the air inlet connector 19 is threadedly connected to an inner wall of the second air inlet hole 7 .

[0048] Example 8 This embodiment provides a dynamic and static pressure mixed gas radial bearing, which differs from the first embodiment in that: like Figure 1 、 Figure 2 and Figure 3As shown, a rear end cover 20 is provided at one end of the bearing seat 1, and the rear end cover 20 is fixed to the bearing seat 1 by bolts 22. A retaining ring 21 is provided at the other end of the bearing seat 1 for limiting the bump foil assembly 3 in the axial direction.

[0049] Example 9 This embodiment provides a dynamic and static pressure mixed gas radial bearing, which differs from the second embodiment in that: like Figure 9 As shown, two second air inlet holes 7 are provided on the limiting portion 4, and a ventilation groove 23 is opened on the bottom surface of the limiting portion 4. The limiting portion 4 is welded to the outside of the shaft sleeve 2, and the bottom surface of the limiting portion 4 contacts the outside of the shaft sleeve 2, and the ventilation groove 23 is connected to the adjacent second air inlet holes 7, so that the external high-pressure air source can flow out through the second air inlet holes 7 and then be diverted to the ventilation groove 23; at least one first heat dissipation groove 25 is provided on one side of the ventilation groove 23.

[0050] Example 10 This embodiment provides a dynamic and static pressure mixed gas radial bearing, which differs from the ninth embodiment in that: like Figure 9 As shown, a second heat dissipation slot 24 is further provided on one side of the outlet end of the second air inlet 7, and both the first heat dissipation slot 25 and the second heat dissipation slot 24 are provided on the side of the stopper 4 close to the fixed end of the double-layer bump foil 10 or the single-layer bump foil. The first heat dissipation slot 25 and the second heat dissipation slot 24 are used to dissipate heat from the bump foil assembly 3.

[0051] The sizes of the first heat dissipation groove 25 and the second heat dissipation groove 24 of the ventilation groove 23 are much smaller than the diameter of the second air inlet 7 and can be set as needed.

[0052] A small portion of the high-pressure gas output from the outlet end of the air inlet connector 19 is discharged through the second heat dissipation slot 24 opened in the second air inlet hole 7 and the first heat dissipation slot 25 opened in the ventilation groove 23, thereby achieving heat dissipation for the bump foil assembly.

[0053] The foregoing description shows and describes preferred embodiments of the present application. However, as previously mentioned, it should be understood that the present application is not limited to the form disclosed herein and should not be construed as excluding other embodiments. Rather, the present application may be used in various other combinations, modifications, and environments, and may be modified within the contemplation of the present invention through the teachings above or through techniques or knowledge in the relevant field. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present application shall be within the scope of protection of the appended claims.

Claims

1. A dynamic and static pressure mixed gas radial bearing, characterized in that: It includes a bearing seat, a shaft sleeve and several corrugated foil components; The shaft sleeve is sleeved inside the bearing seat, and at least two limiting parts are provided on the outside of the shaft sleeve, and the inner wall of the bearing seat is correspondingly provided with limiting grooves; In the radial direction, the corrugated foil assembly is arranged between the shaft sleeve and the bearing seat, and in the circumferential direction, the corrugated foil assembly is arranged between the limiting parts at intervals; A plurality of first air inlet holes are provided at the bottom of the limiting groove, a plurality of second air inlet holes are provided on the limiting portion, and the bearing is further provided with an air inlet joint, which is connected to the first air inlet hole and the second air inlet hole; The shaft sleeve is also provided with a third air inlet hole, and the second air inlet hole is communicated with the third air inlet hole.

2. The dynamic and static pressure mixed gas radial bearing according to claim 1, characterized in that: The bump foil assembly includes a bottom foil, wherein the inner side of the bottom foil is provided with a single-layer bump foil or more in the axial direction, and one end of the single-layer bump foil is a fixed end, and the other end of the single-layer bump foil is a free end; Alternatively, one or more double-layer corrugated foils are arranged on the inner side of the bottom foil in the axial direction, and one end of the double-layer corrugated foil is a fixed end, and the other end of the double-layer corrugated foil is a free end.

3. The dynamic and static pressure mixed gas radial bearing according to claim 2, characterized in that: The double-layer corrugated foil comprises a first corrugated foil and a second corrugated foil which are stacked together. The second corrugated foil and the first corrugated foil are stacked on the bottom foil from inside to outside. Both ends of the first corrugated foil are fixed together with both ends of the second corrugated foil.

4. The dynamic and static pressure mixed gas radial bearing according to claim 3, characterized in that: The first corrugated foil includes a plurality of first circular arcs and second circular arcs connected in sequence, and the radius of the first circular arc is greater than the radius of the second circular arc; The second corrugated foil includes a plurality of third circular arcs and fourth circular arcs connected in sequence. The third circular arc has the same structure as the second circular arc, and the fourth circular arc has the same structure as the first circular arc.

5. The dynamic and static pressure mixed gas radial bearing according to claim 4, characterized in that: A first connecting portion is set between the first arc and the second arc, and a second connecting portion is set between the third arc and the fourth arc; and the first arc is overlapped on the upper part of the third arc and the second connecting portions on both sides of the third arc, and the second arc and the first connecting portions on both sides of the second arc are overlapped on the upper part of the fourth arc.

6. The dynamic and static pressure mixed gas radial bearing according to claim 1, characterized in that: The aperture of the first air inlet hole is larger than that of the second air inlet hole, and the aperture of the second air inlet hole is larger than that of the third air inlet hole.

7. The dynamic and static pressure mixed gas radial bearing according to claim 1, characterized in that: The air inlet connector passes through the first air inlet hole, and the end of the air inlet connector is threadedly connected to the inner wall of the second air inlet hole.

8. The dynamic and static pressure mixed gas radial bearing according to claim 1, characterized in that: A rear end cover is provided at one end of the bearing seat, and the rear end cover is fixed to the bearing seat by bolts. A retaining ring is provided at the other end of the bearing seat for limiting the corrugated foil assembly in the axial direction.

9. The dynamic and static pressure mixed gas radial bearing according to claim 2, characterized in that: Two second air inlet holes are provided on the limiting portion, a ventilation groove is provided on the bottom surface of the limiting portion, and the ventilation groove is connected to adjacent second air inlet holes, and at least one first heat dissipation groove is provided on one side of the ventilation groove.

10. The dynamic and static pressure mixed gas radial bearing according to claim 9, characterized in that: A second heat dissipation groove is further provided on one side of the air outlet end of the second air inlet, and the first heat dissipation groove and the second heat dissipation groove are both opened on one side of the limiting portion close to the fixed end of the double-layer corrugated foil or the single-layer corrugated foil.

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