Multi-stage drainage fan

Abstract

The present invention relates to the technical field of heat dissipation devices, and in particular to a multi-stage drainage fan, comprising a fan body and a drain, the drain comprising a drainage chamber surrounded by a top wall, a bottom wall and side walls connected between the top wall and the bottom wall, second drainage channels corresponding to the first drainage channels are spaced apart in the drainage chamber, the first drainage channel and the corresponding second drainage channel are connected, the present invention forms a primary drainage by directing the jet generated by the jet hole of the fan body into the corresponding first drainage channel after passing through the gap between the fan body and the drain, and sucking in the gas circumferentially outside the area opposite to the jet hole in the gap, the airflow flowing in from the first drainage channel will produce a pulling effect on the gas in the second drainage hole when flowing through the second drainage channel, thereby generating at least one secondary drainage, thereby substantially increasing the amount of airflow finally ejected from the side wall outlet, so as to improve the heat dissipation efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of heat dissipation devices, and in particular to a multi-stage drainage fan. Background Art

[0002] Seeking more efficient heat dissipation technologies and devices in confined spaces has become an urgent need for the 3C electronics industry to further enhance its intelligence. Placing piezoelectric-driven micro-volume fans as heat dissipation devices in the internal space of terminal products is believed to generate greater thermal benefits. However, the demand for lightweight and thin design of electronic products makes the installation space for piezoelectric fans extremely limited, and the limitation on the thickness of piezoelectric fans is particularly evident.

[0003] Existing piezoelectric fans are categorized as forward-jet and side-jet based on the direction of airflow. The air outlet of a forward-jet fan faces the center of the heat source, forcing it to overlap with the heat source in thickness during use, increasing the overall thickness. Furthermore, the heat-carrying gas that completes the heat exchange lacks the power to be directed out of the product, leading to hot air stagnation or circulation between the fan and the heat source, affecting heat dissipation efficiency. These issues make forward-jet fans unsuitable for heat dissipation within the confined spaces of 3C smart terminal products.

[0004] The side-spray fan has a side air outlet, and the heat source is set in the outflow direction of the fan, which overcomes the above-mentioned problems of the straight-spray fan. However, since the direction of the airflow is inconsistent with the final outflow direction of the airflow, the airflow needs to be deflected at a large angle in the space. This process will cause energy loss, resulting in insufficient airflow flow ejected from the side air outlet, and the purpose of efficient heat dissipation cannot be achieved. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: in order to solve the problem of insufficient air flow rate ejected from the side air outlet in the prior art, a multi-stage drainage fan is provided.

[0006] The technical solution adopted by the present invention to solve the technical problem is: a multi-stage airflow fan, comprising a fan body and airflow diverters arranged on one side or both sides of the fan body with a gap therebetween, wherein the airflow diverters guide the airflow generated by the fan body to be ejected in a set direction:

[0007] The fan body is provided with at least two jet holes on one side close to the flow guider, and the airflow generated by the fan body is ejected through the jet holes;

[0008] The flow guider includes a flow chamber enclosed by a top wall, a bottom wall, and a side wall connected between the top wall and the bottom wall. The flow chamber extends in a set direction and penetrates the side wall, and forms an outlet at the penetration point of the side wall. The top wall is arranged near the fan body. The top wall is provided with a first flow channel corresponding to each of the jet holes and penetrating the top wall in an area opposite to the at least two jet holes.

[0009] Second drainage channels corresponding to the first drainage channels are distributed in the drainage cavity at intervals, the first drainage channel is connected to the corresponding second drainage channel, the second drainage channel is connected to the outlet, and the flow area of ​​the second drainage channel tends to gradually increase along the extension path from the second drainage channel to the outlet.

[0010] Furthermore, the flow area of ​​the first drainage channel is larger than the flow area of ​​the jet hole opposite thereto.

[0011] Furthermore, at least one second drainage hole is provided at one end of the side wall forming the drainage cavity away from the outlet, and the second drainage hole passes through the side wall and is connected to the drainage port of at least one second drainage channel, and the drainage port is located between the first drainage channel corresponding to the second drainage channel and the outlet.

[0012] Furthermore, the top wall has a first drainage area corresponding to each of the first drainage channels, and the first drainage area is an adjacent area on the top wall provided on the outer periphery of the corresponding first drainage channel;

[0013] The bottom wall has a second drainage area corresponding to the first drainage area one by one, and the second drainage area and the corresponding first drainage area are directly opposite;

[0014] At least one of the first drainage areas and / or at least one of the second drainage areas is penetrated by a first drainage hole communicating with the second drainage channel.

[0015] Furthermore, the first drainage hole is located in a region opposite to an extension path of the second drainage channel toward the outlet.

[0016] Furthermore, each of the second drainage channels is individually connected to the first drainage hole, and the first drainage holes are all arranged on the top wall.

[0017] Solution 1 for forming a second drainage channel with a gradually increasing flow area: the top wall is a plate-like structure with a variable thickness; along the extension path from the second drainage channel to the outlet, the thickness of the top wall opposite the second drainage channel gradually decreases, so that the flow area of ​​the second drainage channel gradually increases along the extension path from the second drainage channel to the outlet;

[0018] Alternatively, the bottom wall is a plate-like structure with a variable thickness; along the extension path from the second drainage channel to the outlet, the thickness of the bottom wall opposite the second drainage channel gradually decreases, so that the flow area of ​​the second drainage channel tends to gradually increase along the extension path from the second drainage channel to the outlet;

[0019] Alternatively, the top wall and the bottom wall are both plate-like structures with variable thickness; along the extension path from the second drainage channel to the outlet, the thickness of the top wall opposite the second drainage channel gradually decreases, and the thickness of the bottom wall opposite the second drainage channel gradually decreases, so that the flow area of ​​the second drainage channel tends to gradually increase along the extension path from the second drainage channel to the outlet;

[0020] The second scheme for forming a second drainage channel with a flow area that tends to gradually increase is that the top wall is a flat plate structure, and along the extension path from the second drainage channel to the outlet, the width dimension of the second drainage channel in the longitudinal direction that intersects with the extension path space of the second drainage channel to the outlet gradually increases, so that the flow area of ​​the second drainage channel tends to gradually increase along the extension path from the second drainage channel to the outlet.

[0021] Furthermore, the flow area of ​​the first drainage channel is 1.1 to 10 times the flow area of ​​the corresponding jet hole.

[0022] Furthermore, each second drainage channel is connected to the same outlet.

[0023] Furthermore, the flow areas of at least two of the jet holes are the same or different.

[0024] Furthermore, it further comprises a partition plate, and the fan body is connected to the flow guider through the partition plate;

[0025] The partition plate is a plurality of partitions discretely arranged between the fan body and the top wall, and the opening between two adjacent partitions constitutes a through hole, which allows external ambient air to enter the gap between the fan body and the flow guider;

[0026] Alternatively, the partition plate is a continuous partition plate in a closed-loop structure arranged between the fan body and the top wall, and at least one hole structure or groove structure is provided on the partition plate, and the hole structure or groove structure constitutes a flow hole, and the flow hole allows external ambient gas to enter the gap between the fan body and the deflector.

[0027] The beneficial effect of the present invention is that the multi-stage induced draft fan of the present invention forms a primary induced draft by directing the jet generated by the jet hole of the fan body into the corresponding first induced draft channel through the gap between the fan body and the guider, and then sucking in the gas in the outer circumference of the area opposite to the jet hole in the gap, so that the flow direction of the fluid is deflected after entering the second induced draft channel. Although energy loss occurs, the airflow has high inertia after being rectified by the first induced draft channel, and can still maintain a certain momentum to flow through the second induced draft channel and finally be ejected from the outlet on the side wall. In this process, on the one hand, since the flow area of ​​the second induced draft channel tends to gradually increase along the extension path from the second induced draft channel to the outlet, the airflow slows down and restores the pressure when flowing through the second induced draft channel, which can increase the flow rate; on the other hand, when the airflow flows through the second induced draft channel, it will also produce a pulling effect on the gas in the second induced draft hole, thereby generating at least one secondary induced draft, thereby substantially increasing the amount of airflow finally ejected from the side wall outlet, so as to improve the heat dissipation efficiency.

[0028] Other features and advantages of the present application will become apparent from the following detailed description of exemplary embodiments of the present application with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention will be further described below with reference to the accompanying drawings and examples.

[0030] Figure 1 is a schematic diagram of a multi-stage drainage fan of the present invention;

[0031] Figure 2 is a schematic diagram of the jet hole, the first drainage channel and the first drainage hole projected onto the cross section of the side wall;

[0032] Figure 3 Schematic diagram of a drain with a top wall having a planar plate-like structure;

[0033] Figure 4 is a schematic cross-sectional view of a flow diverter with gradually increasing width in the longitudinal direction intersecting the second drainage channel and the extension path space of the second drainage channel toward the outlet;

[0034] Figure 5 Schematic diagram of a drainage device provided with a second drainage hole;

[0035] Figure 6 Schematic diagram of a drainage device provided with a first drainage hole and a second drainage hole;

[0036] Figure 7 It is a schematic diagram of a multi-stage induced draft fan having multiple outlets on the same side;

[0037] Figure 8 It is a schematic diagram of a multi-stage drainage fan provided with a partition plate according to the present invention.

[0038] In the figure: 1, drainer, 11, top wall, 12, side wall, 13, bottom wall, 1-1, first drainage channel, 1-2, second drainage channel, 1-2a, drainage port, 1-3, outlet, 1-4, first drainage hole, 1-5, second drainage hole;

[0039] 2. Fan body, 21. Jet hole;

[0040] 3. Partition plate, 31. Through hole, 3-1. Gap. DETAILED DESCRIPTION

[0041] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams that illustrate the basic structure of the present invention only in a schematic manner. Therefore, they only show components relevant to the present invention, and directions and references (e.g., up, down, left, right, etc.) may be used solely to facilitate the description of features in the drawings. The following detailed description is therefore not to be taken in a limiting sense, and the scope of the claimed subject matter is defined solely by the appended claims and their equivalents.

[0042] Example 1

[0043] like Figure 1 As shown, a multi-stage airflow fan includes a fan body 2 and an airflow guider 1 disposed on one or both sides of the fan body 2 with a gap 3-1 therebetween. The airflow guider 1 guides the airflow generated by the fan body 2 to be ejected in a set direction. The set direction refers to the direction in which the outlet 1-3 of the multi-stage airflow fan of this embodiment is toward the heat source, thereby realizing heat dissipation of the heat source by using the multi-stage airflow fan of this embodiment:

[0044] At least two jet holes 21 are provided on one side of the fan body 2 close to the deflector 1. The shape of the jet hole 21 can be circular, square, rectangular, elliptical or other shapes, and there is no limitation on this. In addition, the flow areas of at least two jet holes 21 can be the same or different. In this embodiment, the shape of the jet hole 21 is circular, and the flow areas of at least two jet holes 21 are the same for illustration, but this does not constitute a limitation to the present invention.

[0045] The airflow generated by the fan body 2 is ejected through the jet holes 21; the deflector 1 includes a deflection chamber enclosed by a top wall 11, a bottom wall 13, and a side wall 12 connected between the top wall 11 and the bottom wall 13. The deflection chamber extends in a set direction and penetrates the side wall 12, and an outlet 1-3 is formed at the penetration of the side wall 12. The top wall 11 is arranged near the fan body 2, and the areas of the top wall 11 opposite to the at least two jet holes 21 are respectively provided with first deflection channels 1-1 corresponding to the jet holes 21 and penetrating the top wall 11; second deflection channels 1-2 corresponding to the first deflection channels 1-1 are distributed at intervals in the deflection chamber, and the first deflection channels 1-1 are connected to the corresponding second deflection channels 1-2;

[0046] The second drainage channels 1-2 are all connected to the outlet 1-3. It can be that each second drainage channel 1-2 is connected to the same outlet 1-3, such as Figure 2 It can also be that the drainage cavity extends in a set direction and passes through the side wall 12 to form a plurality of outlets 1-3, and the second drainage channels 1-2 are connected to the corresponding outlets 1-3, such as Figure 7 As shown; there may even be multiple outlets 1-3, and the same outlet 1-3 may be connected to one or two or more second drainage channels 1-2.

[0047] It is not difficult to understand that the jet hole 21 provided on the fan body 2 is opposite to the top wall 11 of the deflector 1, and the outlets 1-3 are provided on the side wall 12 that encloses the deflection cavity. After the airflow is ejected from the jet hole 21 of the fan body 2, the flow direction is deflected under the action of the deflector 1, so that the multi-stage deflection fan of this embodiment has the function of side jetting.

[0048] Similarly, the cross-sectional shape of the first drainage channel 1-1 may be circular, square, rectangular, elliptical, or other shapes, without limitation. In this embodiment, the cross-sectional shape of the first drainage channel 1-1 is circular for illustration, but this does not constitute a limitation of the present invention. The flow area of ​​the first drainage channel 1-1 is larger than the flow area of ​​the jet hole 21 opposite thereto. Preferably, the flow area of ​​the first drainage channel 1-1 is 1.1 to 10 times the flow area of ​​the jet hole 21 opposite thereto, so that the airflow ejected from the jet hole 21 can be received by the first drainage channel 1-1, thereby avoiding flow loss caused by wall reflection.

[0049] The flow area of ​​the second drainage channel 1-2 gradually increases along the extension path from the second drainage channel 1-2 to the outlet 1-3;

[0050] The top wall 11 has a first drainage area corresponding to the first drainage channel 1-1. The first drainage area is an adjacent area on the top wall 11 provided on the outer peripheral side of the corresponding first drainage channel 1-1.

[0051] The bottom wall 13 has a second drainage area corresponding to the first drainage area one by one, and the second drainage area and the corresponding first drainage area are directly opposite;

[0052] The first drainage area and / or the second drainage area are penetrated by the first drainage hole 1-4 connected to the second drainage channel 1-2; that is, the first type is: the first drainage area is penetrated by the first drainage hole 1-4 connected to the second drainage channel 1-2, the second type is: the second drainage area is penetrated by the first drainage hole 1-4 connected to the second drainage channel 1-2, and the third type is: the first drainage area is penetrated by the first drainage hole 1-4 connected to the second drainage channel 1-2, and the second drainage area is also penetrated by the first drainage hole 1-4 connected to the second drainage channel 1-2; in this way, by arranging the first drainage hole 1-4 in the adjacent area of ​​the first drainage channel 1-1 corresponding to the second drainage channel 1-2, the technical effect that can be achieved is to make full use of the high inertia of the airflow after being rectified by the first drainage channel 1-1; the configuration relationship between the jet hole 21, the first drainage channel 1-1, the second drainage channel 1-2, the first drainage hole 1-4 and the outlet 1-3 is as follows: Figure 1-Figure 2 shown.

[0053] Preferably, if Figure 2 As shown, the first drainage hole 1-4 is located in the first drainage area 11-1 and / or the second drainage area 13-1 in an area opposite to the extension path of the second drainage channel 1-2 toward the outlet 1-3. In other words, the drainage hole is located in the direction of the extension path of the second drainage channel 1-2 toward the outlet 1-3. When the first drainage hole 1-4 is arranged on the bottom wall 13, it is staggered with the first drainage channel 1-1. In other words, when the first drainage hole 1-4 is arranged on the bottom wall 13, the first drainage hole 1-4 is not arranged opposite to the first drainage channel 1-1.

[0054] Further preferably, each second drainage channel 1 - 2 is equipped with a first drainage hole 1 - 4 , and the first drainage holes 1 - 4 are all provided on the top wall 11 .

[0055] The top wall 11 is a plate-like structure with a variable thickness. Along the extension path from the second drainage channel 1-2 to the outlet 1-3, the thickness of the top wall 11 opposite to the second drainage channel 1-2 gradually decreases, so that the flow area of ​​the second drainage channel 1-2 gradually increases along the extension path from the second drainage channel 1-2 to the outlet 1-3. Figure 1 As shown;

[0056] Alternatively, the bottom wall 13 is a plate-like structure with a variable thickness; along the extension path from the second drainage channel 1-2 to the outlet 1-3, the thickness of the bottom wall 13 opposite the second drainage channel 1-2 gradually decreases, so that the flow area of ​​the second drainage channel 1-2 gradually increases along the extension path from the second drainage channel 1-2 to the outlet 1-3;

[0057] Alternatively, the top wall 11 and the bottom wall 13 are both plate-like structures with variable thickness; along the extension path from the second drainage channel 1-2 to the outlet 1-3, the thickness of the top wall 11 opposite the second drainage channel 1-2 gradually decreases, and the thickness of the bottom wall 13 opposite the second drainage channel 1-2 gradually decreases, so that the flow area of ​​the second drainage channel 1-2 gradually increases along the extension path from the second drainage channel 1-2 to the outlet 1-3;

[0058] Alternatively, the top wall 11 is a planar plate-shaped structure, and along the extension path from the second drainage channel 1-2 to the outlet 1-3, the width of the second drainage channel 1-2 in the longitudinal direction intersecting with the extension path space of the second drainage channel 1-2 to the outlet 1-3 gradually increases, so that the flow area of ​​the second drainage channel 1-2 tends to gradually increase along the extension path from the second drainage channel 1-2 to the outlet 1-3, as shown in FIG. Figure 3-Figure 4 shown.

[0059] Thus, by arranging the deflector 1 on one side or both sides of the fan body 2 with a gap 3-1 between them, at least two jet holes 21 are arranged on the side of the fan body 2 close to the deflector 1, and the top wall 11 of the deflector 1 and the area opposite to the at least two jet holes 21 are respectively provided with a first deflection channel 1-1 that passes through the top wall 11. The airflow generated by the fan body 2 is ejected through the jet holes 21, and the gas outside the area opposite to the jet holes 21 in the gap 3-1 between the fan body 2 and the deflector 1 is sucked in to form a primary deflection, so that the flow direction of the fluid is deflected after entering the second deflection channel 1-2. Although energy loss occurs, the airflow has high inertia after being rectified by the first deflection channel 1-1, and can still maintain a certain momentum to flow through the second deflection channel 1-2 and finally be ejected from the outlet 1-3 on the side wall 12. In this process, on the one hand, since the flow area of ​​the second deflection channel 1-2 is increased along the second deflection channel 1- 2 shows a gradually increasing trend on the extension path toward the outlet 1-3. When the airflow flows through the second drainage channel 1-2, the pressure is restored while slowing down, which can increase the flow rate. On the other hand, since at least one first drainage hole 1-4 is correspondingly penetrated in the area on the top wall 11 or / and the bottom wall 13 opposite to the extension path of the second drainage channel 1-2 toward the outlet 1-3, the first drainage hole 1-4 is connected to the corresponding second drainage channel 1-2, and even at least one second drainage hole 1-5 is provided on the side wall 12 at the end of the drain device 1 away from the outlet 1-3, which penetrates the side wall 12 and is connected to at least one second drainage channel 1-2. When the airflow flows through the second drainage channel 1-2, it will also produce a pulling effect on the gas in the first drainage hole 1-4 and / or the second drainage hole 1-5, thereby generating at least one secondary drainage, thereby substantially increasing the amount of airflow finally ejected from the outlet 1-3 of the side wall 12, so as to improve the heat dissipation efficiency.

[0060] The fan body 2 in this embodiment can adopt any one of the fans with at least two air outlets in the prior art, especially any one of the piezoelectric fans with at least two air outlets in the prior art. The airflow generated by the fan body 2 is ejected from the air outlet, and the air outlet is the jet hole 21 in this embodiment; for example, the fan body 2 in this embodiment can be but is not limited to the fluid generating device disclosed in the Chinese patent with publication number CN119084287A, and the hole portion in the patent corresponds to the jet hole 21 in this embodiment; the fan body 2 in this embodiment can also adopt the high-order resonance fluid generating device disclosed in the Chinese patent with publication number CN118979867A, and the hole portion in the patent corresponds to the jet hole 21 in this embodiment.

[0061] Example 2

[0062] The difference between Example 2 and Example 1 is that at least one second drainage hole 1-5 is provided at one end of the side wall 12 that encloses the drainage cavity and is away from the outlet 1-3. The second drainage hole 1-5 passes through the side wall 12 and is connected to the drainage hole 1-2a of at least one second drainage channel 1-2. The drainage hole 1-2a is located between the first drainage channel 1-1 corresponding to the second drainage channel 1-2 and the outlet 1-3. The drainage hole 1-2a can be, but is not limited to, located on any side of the circumference of the second drainage channel 1-2 in which it is located. For example, the drainage hole 1-2a can be located in the middle part of the second drainage channel 1-2; so as to make full use of the high inertia of the airflow after being rectified by the first drainage channel 1-1, and to draw more gas from the second drainage hole 1-5, thereby substantially increasing the amount of airflow finally ejected from the outlet 1-3 of the side wall 12, so as to improve the heat dissipation efficiency. Figure 5-Figure 6 shown.

[0063] Example 3

[0064] The difference between this embodiment and embodiment 1 or 2 is that: Figure 8 As shown, it also includes a partition plate 3, the fan body 2 is connected to the flow diverter 1 through the partition plate 3, and the partition plate 3 can be specifically fixedly connected to the shell of the fan body 2;

[0065] The partition plates 3 are a plurality of partitions discretely disposed between the fan body 2 and the top wall 11. The plurality of partitions may be spaced apart along the circumference of the fan body 2. The openings between two adjacent partitions constitute flow holes 31. The flow holes 31 allow external ambient air to enter the gap 3-1 between the fan body 2 and the flow guider 1.

[0066] Alternatively, the partition plate 3 is a continuous partition plate 3 in a closed-loop structure arranged between the fan body 2 and the top wall 11. The partition plate 3 may be in a circular ring shape, and at least one hole structure or groove structure is provided on the partition plate 3. The hole structure or groove structure constitutes a flow hole 31, and the flow hole 31 allows external ambient gas to enter the gap 3-1 between the fan body 2 and the deflector 1.

[0067] Thus, the fan body 2 and the drain 1 can be constructed into an integral module.

[0068] The above description of the preferred embodiments of the present invention is intended to serve as a guide. Based on the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A multi-stage drainage fan, characterized in that: The invention comprises a fan body (2) and a flow guide (1) arranged on one side or both sides of the fan body (2) with a gap (3-1) therebetween, wherein the flow guide (1) guides the airflow generated by the fan body (2) to be ejected in a set direction. At least two jet holes (21) are provided on one side of the fan body (2) close to the flow guider (1), and the airflow generated by the fan body (2) is ejected through the jet holes (21); The flow guider (1) comprises a flow guide cavity enclosed by a top wall (11), a bottom wall (13), and a side wall (12) connected between the top wall (11) and the bottom wall (13); the flow guide cavity extends in a set direction and penetrates the side wall (12), and forms an outlet (1-3) at the penetration point of the side wall (12); the top wall (11) is arranged close to the fan body (2); and the regions of the top wall (11) opposite to the at least two jet holes (21) are respectively provided with first flow guide channels (1-1) corresponding to the jet holes (21) and penetrating the top wall (11); Second drainage channels (1-2) corresponding to the first drainage channels (1-1) are distributed in the drainage cavity at intervals, the first drainage channel (1-1) and the corresponding second drainage channel (1-2) are connected, the second drainage channel (1-2) is connected with the outlet (1-3), and the flow area of ​​the second drainage channel (1-2) tends to gradually increase along the extension path from the second drainage channel (1-2) to the outlet (1-3).

2. The multi-stage airflow fan according to claim 1, characterized in that: The flow area of ​​the first drainage channel (1-1) is larger than the flow area of ​​the jet hole (21) opposite thereto.

3. The multi-stage airflow fan according to claim 2, characterized in that: At least one second drainage hole (1-5) is provided at one end of the side wall (12) that encloses the drainage cavity and is away from the outlet (1-3). The second drainage hole (1-5) passes through the side wall (12) and is connected to the drainage hole (1-2a) of at least one second drainage channel (1-2). The drainage hole (1-2a) is located between the first drainage channel (1-1) corresponding to the second drainage channel (1-2) and the outlet (1-3).

4. The multi-stage airflow fan according to any one of claims 1 to 3, characterized in that: The top wall (11) has a first drainage area corresponding one-to-one to the first drainage channel (1-1), and the first drainage area is an adjacent area on the top wall (11) provided on the outer peripheral side of the corresponding first drainage channel (1-1); The bottom wall (13) has a second drainage area corresponding to the first drainage area (11-1) on a one-to-one basis, and the second drainage area and the corresponding first drainage area are directly opposite; At least one of the first drainage areas and / or at least one of the second drainage areas is penetrated by a first drainage hole (1-4) that is in communication with a second drainage channel (1-2).

5. The multi-stage airflow fan according to claim 4, characterized in that: The first drainage hole (1-4) is located in a region opposite to an extension path of the second drainage channel (1-2) toward the outlet (1-3).

6. The multi-stage airflow fan according to claim 5, characterized in that: Each of the second drainage channels (1-2) is individually connected to the first drainage hole (1-4), and the first drainage holes (1-4) are all arranged on the top wall (11).

7. The multi-stage airflow fan according to any one of claims 1 to 3, characterized in that: The top wall (11) is a plate-like structure with a variable thickness; along the extension path from the second drainage channel (1-2) toward the outlet (1-3), the thickness of the top wall (11) opposite to the second drainage channel (1-2) gradually decreases, so that the flow area of ​​the second drainage channel (1-2) tends to gradually increase along the extension path from the second drainage channel (1-2) toward the outlet (1-3); Alternatively, the bottom wall (13) is a plate-like structure with a variable thickness; along the extension path from the second drainage channel (1-2) to the outlet (1-3), the thickness of the bottom wall (13) opposite to the second drainage channel (1-2) gradually decreases, so that the flow area of ​​the second drainage channel (1-2) tends to gradually increase along the extension path from the second drainage channel (1-2) to the outlet (1-3); Alternatively, the top wall (11) and the bottom wall (13) are both plate-like structures with variable thickness; along the extension path from the second drainage channel (1-2) toward the outlet (1-3), the thickness of the top wall (11) opposite to the second drainage channel (1-2) gradually decreases, and the thickness of the bottom wall (13) opposite to the second drainage channel (1-2) gradually decreases, so that the flow area of ​​the second drainage channel (1-2) tends to gradually increase along the extension path from the second drainage channel (1-2) toward the outlet (1-3).

8. The multi-stage airflow fan according to any one of claims 1 to 3, characterized in that: The top wall (11) is a planar plate-shaped structure, and along the extension path from the second drainage channel (1-2) to the outlet (1-3), the width of the second drainage channel (1-2) in the longitudinal direction intersecting with the extension path space of the second drainage channel (1-2) to the outlet (1-3) gradually increases, so that the flow area of ​​the second drainage channel (1-2) tends to gradually increase along the extension path from the second drainage channel (1-2) to the outlet (1-3).

9. The multi-stage airflow fan according to any one of claims 1 to 3, characterized in that: The flow area of ​​the first drainage channel (1-1) is 1.1 to 10 times the flow area of ​​the corresponding jet hole (21).

10. The multi-stage airflow fan according to any one of claims 1 to 3, characterized in that: Each second drainage channel (1-2) is in communication with the same outlet (1-3).

11. The multi-stage induced draft fan according to any one of claims 1 to 3: the flow areas of at least two of the jet holes (21) are the same or different.

12. The multi-stage airflow fan according to any one of claims 1 to 3, further comprising a partition plate (3), wherein the fan body (2) is connected to the airflow guider (1) via the partition plate (3); The partition plate (3) is a plurality of partitions discretely arranged between the fan body (2) and the top wall (11), and the opening between two adjacent partitions constitutes a through-hole (31). The through-hole (31) allows external ambient air to enter the gap (3-1) between the fan body (2) and the flow guider (1); Alternatively, the partition plate (3) is a continuous partition plate (3) in a closed-loop structure disposed between the fan body (2) and the top wall (11), and the partition plate (3) is provided with at least one hole structure or slot structure, wherein the hole structure or slot structure constitutes a flow hole (31), and the flow hole (31) allows external ambient air to enter the gap (3-1) between the fan body (2) and the flow guide (1).

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