Rotor assembly, axial flow fan and extractor hood

Abstract

The present application relates to fan mechanical technology field, especially to a kind of moving blade assembly, axial flow fan and range hood, including shell and the hub being set in the shell;Multiple blades, with the rotary axis of the hub as center symmetrically arranged, the top of the blade and the inner wall of the shell are spaced, the blade has suction surface and pressure surface;First shoulder, protruding on the suction surface, along the flow direction of airflow, the first shoulder is inclined and extended upwards on the suction surface, so that the first shoulder and the inner wall of the shell form tapered airflow passage;And, second shoulder, protruding on the pressure surface, along the flow direction, the second shoulder is inclined and extended downwards on the pressure surface, so that the second shoulder and the inner wall of the shell form gradually expanded airflow passage.The moving blade assembly structure can reduce the leakage flow in airflow passage without changing the blade tip clearance.

Description

Technical Field

[0001] This invention relates to the field of fan machinery technology, and in particular to a moving blade assembly, an axial flow fan, and a range hood. Background Technology

[0002] Axial flow fans are a commonly used type of fan in range hoods. They are called axial flow fans because the airflow inside the fan flows along the fan axis. Axial flow fans are generally widely used in applications where high flow rate and low pressure requirements are needed, such as range hoods.

[0003] When axial flow fans are used in range hoods, the impeller tip clearance Δh often needs to be set to a relatively large value to prevent grease buildup from condensing inside the fan and affecting the blade rotation. However, increasing the tip clearance can negatively impact fan performance. The most significant effect is the increased leakage flow, which affects not only the fan's flow efficiency but also the noise generated during operation, negatively impacting the user experience. Summary of the Invention

[0004] In view of this, it is necessary to provide a moving blade assembly, an axial flow fan and a range hood to address the above problems. The moving blade assembly structure can reduce leakage flow in the airflow channel without changing the blade tip clearance.

[0005] A first aspect of the present invention provides a moving blade assembly, the moving blade assembly comprising:

[0006] Housing and hub disposed within the housing;

[0007] Multiple blades are arranged symmetrically about the axis of rotation of the hub. The tips of the blades are spaced apart from the inner wall of the housing. Each blade has a suction surface and a pressure surface.

[0008] A first shoulder, protruding from the suction surface and extending obliquely upward along the airflow direction, forms a gradually narrowing airflow channel between the first shoulder and the inner wall of the housing; and...

[0009] The second shoulder is provided on the pressure surface and extends obliquely downward along the flow direction, so that a gradually expanding airflow channel is formed between the second shoulder and the inner wall of the housing.

[0010] This design, with the blades spaced apart from the inner wall of the casing, prevents the accumulation of oil, dust, and other contaminants on the blade tips. The first shoulder forms a tapering airflow channel on the suction surface, allowing the airflow to accelerate within this channel and providing an upward velocity component, thus preventing leakage flow from directly entering the main flow path near the suction surface. The second shoulder forms a widening airflow channel on the pressure surface, allowing the airflow to gradually decelerate within this channel and providing a downward velocity component to counteract the upward leakage flow, thereby reducing leakage. The two shoulders on either side of the blade reduce the impact of leakage, significantly improving leakage within the blade assembly, greatly reducing tip leakage loss, increasing impeller efficiency and airflow, and significantly reducing noise at the blade assembly. Furthermore, the shoulders on both sides also contribute to the structural stability of the blades.

[0011] In one embodiment, the first shoulder and the second shoulder have the same mass, and / or the first shoulder, the second shoulder and the blade are integrally formed.

[0012] This design, with the first and second shoulders having the same mass, further enhances the stability of the blade. Furthermore, molding the two shoulders integrally with the blade not only simplifies the overall machining process of the moving blade assembly but also results in a more robust structure.

[0013] In one embodiment, along the flow direction, the front ends of both the first shoulder and the second shoulder do not extend beyond the front end of the blade.

[0014] This design avoids the first and second protruding shoulders from affecting the airflow at the air inlet.

[0015] In one embodiment, along the flow direction, the rear ends of both the first shoulder and the second shoulder do not extend beyond the rear end of the blade.

[0016] This design avoids exacerbating airflow interference between the two protruding shoulders and the stationary blades located behind the moving blade assembly.

[0017] In one embodiment, along the flow direction, the lengths of the first shoulder and the second shoulder are both 'a', and the length of the blade corresponding to the location of the first shoulder and the second shoulder is 't', where 'a' and 't' satisfy the following relationship: 0.8t <a<t。

[0018] With such a setting, the relationship between the lengths a of the two shoulders and the length t of the blade is satisfied as above, which can avoid the interference of the first shoulder and the second shoulder on the air flow on the front and rear sides of the blade. At the same time, the shoulders on both sides can also serve as a strengthening structure for the blade, significantly improving the structural strength of the blade and having a sufficient impact on the air flow on the suction surface and the pressure surface.

[0019] In one embodiment, the vertical distance from the root to the top of the blade is h, the distance between the front end of the first shoulder and the top of the blade is x1, and the relationship between h and x1 is satisfied as follows: 0.5h < x1 < h, and / or, the vertical distance from the root to the top of the blade is h, the distance between the front end of the second shoulder and the top of the blade is x2, and the relationship between h and x2 is satisfied as follows: 0 < x2 < 0.5h.

[0020] With such a setting, it can be ensured that the shoulders on both sides are located at positions on the blade relatively close to the blade tip where leakage flow occurs, thereby better improving the leakage flow.

[0021] In one embodiment, along the flow direction, the length of the blade is t; the included angle between the inclined extension direction of the first shoulder on the suction surface and the flow direction is θ1, arctan(x1 / t) > θ1 > 0; the included angle between the inclined extension direction of the second shoulder on the pressure surface and the air flow direction is θ2, arctan(x2 / t) > θ2 > 0.

[0022] With such a setting, it can be ensured that the shoulders on both sides are inclined at an appropriate angle along the preset direction, thereby better guiding the air flow to generate a velocity against the leakage flow direction.

[0023] In one embodiment, the thicknesses of the first shoulder and the second shoulder are d, and the gap between the top of the blade and the inner wall of the housing is Δh, 0.5 * Δh < d < 3 * Δh.

[0024] With such a setting, when the thicknesses of the shoulders on both sides are within the above range, it can ensure the structural strength while avoiding the shoulders occupying too much air flow area.

[0025] In a second aspect of the present invention, an axial flow fan is provided, which includes the moving blade assembly in any of the above embodiments and a stationary blade assembly.

[0026] In a third aspect of the present invention, an oil fume extractor is provided, which is characterized in that the oil fume extractor includes the axial flow fan in any of the above embodiments.

[0027] In the aforementioned range hood, because the blades in the moving blade assembly are respectively provided with a first shoulder and a second shoulder on both sides, and the shoulders on both sides are inclined in a preset direction, they can guide the airflow passing over the corresponding surfaces of the blades, thereby improving leakage flow. Thus, when setting the blade tip clearance between the blade tip and the inner wall of the casing, concerns about leakage flow can be disregarded, and it can be set slightly larger, thereby meeting the design requirements of the axial flow fan in the range hood. At the same time, the two shoulders also serve to block grease, preventing grease from accumulating on the inner wall of the casing. Attached Figure Description

[0028] Figure 1 This is a structural schematic diagram of an axial flow fan in the prior art. The view shown in the figure is from the suction surface of the blades.

[0029] Figure 2 for Figure 1 The diagram shows the structure of the axial flow fan as viewed from the pressure surface.

[0030] Figure 3 An exploded structural view of an axial flow fan according to an embodiment of the present invention;

[0031] Figure 4 for Figure 3 A schematic diagram of the blades of the axial flow fan shown in the figure;

[0032] Figure 5 for Figure 3 A schematic diagram of the structure of the axial flow fan as seen from the self-priming surface;

[0033] Figure 6 for Figure 3 The diagram shows the structure of the axial flow fan as viewed from the pressure surface.

[0034] Figure 7 for Figure 3 The schematic diagram of the axial flow fan shown is viewed from the self-priming surface, which is compared to... Figure 5 The fluid flow path, indicated by the arrow, has been added;

[0035] Figure 8 for Figure 3 The schematic diagram of the axial flow fan shown is viewed from the pressure surface, which is compared to... Figure 6 The fluid flow path, indicated by the arrow, has been added;

[0036] Figure 9a For corresponding Figure 1 Simulated cloud map;

[0037] Figure 9b For corresponding Figure 2 Simulated cloud map;

[0038] Figure 9cFor corresponding Figure 7 Simulated cloud map;

[0039] Figure 9d For corresponding Figure 8 Simulated cloud map.

[0040] Figure label:

[0041] 1. Housing; 10. Air inlet; 2. Hub; 3. Blade; 30. Suction surface; 31. Pressure surface; 4. First shoulder; 5. Second shoulder; 6. Stationary blade assembly; 61. Stationary blade; 62. Stationary blade housing; 63. Stationary blade hub. Detailed Implementation

[0042] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0043] In the description of this invention, it should be understood that the terms "center," "longitudinal," and "lateral" are used interchangeably.

[0044]

[0045] The orientations or positional relationships indicated by terms such as "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" are based on the orientations or positional relationships shown in the accompanying drawings and are only for the purpose of facilitating the description of the present invention and simplifying the description. They are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the present invention.

[0046] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0047] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0048] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0049] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0050] First refer to Figure 1 and Figure 2 As shown, in existing axial flow fans, moving blade assemblies and stationary blade assemblies 6' are spaced apart within the casing 1' along the fluid inflow direction, wherein blades 3' are mounted on the hub 2' of the moving blades. To prevent oil and other contaminants from accumulating on the inner wall of the casing 1', a relatively large gap l is generally required between the tip of the blade 3' and the inner wall of the casing 1'. However, at the tip of the blade 3', some of the airflow that passes over the tip of the blade 3' forms a leakage flow. Figure 1 As indicated by the arrow, on the suction surface of blade 3', there will be a leakage flow from the casing 1' towards the tip of blade 3'; and as... Figure 2 As shown by the arrow, leakage flow occurs from the tip of blade 3' towards the inner wall of casing 1' on the pressure surface of blade 3'. The leakage flow becomes more pronounced as the gap l increases. This not only affects the overall efficiency of the fan but also generates significant noise.

[0051] To reduce the impact of leakage flow, common methods include reducing the clearance h or designing complex shapes at the tip of the blade 3'. However, the clearance h usually cannot be designed too small, and designing the tip of the blade 3' places high demands on the machining and assembly precision of the blade, making it difficult to guarantee product quality and significantly increasing costs.

[0052] To solve the above problem, see Figures 3 to 7 As shown in the figure, one embodiment of the present invention first provides a moving blade assembly for use in the axial flow fan shown in the figure, which may include a stationary blade assembly 6 in addition to the moving blade assembly.

[0053] The moving blade assembly includes a housing 1, a hub 2 disposed within the housing 1, and multiple blades 3 fixedly disposed on the outer periphery of the hub 2. The multiple blades 3 are arranged in a centrally symmetrical manner with the rotation axis of the hub 2 as the center, and a gap Δh is left between the top of the blades 3 and the inner wall of the housing 1.

[0054] The blade 3 has a suction surface 30 facing the airflow and a pressure surface 31 facing away from the airflow. Specifically, the suction surface 30 has a first shoulder 4 protruding along the direction of airflow (i.e., from...). Figure 3 The air inlet 10 flows into the housing 1 in a direction parallel to the rotation axis of the hub 2. The first shoulder 4 extends obliquely upward on the suction surface 30, thereby forming a gradually narrowing airflow channel between the first shoulder 4 and the inner wall of the housing 1. A second shoulder 5 is provided on the pressure surface 31. Along the flow direction, the second shoulder 5 extends obliquely downward, thereby forming a gradually widening airflow channel between the second shoulder 5 and the inner wall of the housing 1.

[0055] refer to Figure 7 As shown, on the suction surface 30, the gradually narrowing airflow channel between the first shoulder 4 and the inner wall of the housing 1 simultaneously attracts and accelerates the incoming airflow and guides it obliquely. Thus, the incoming airflow accelerates within this gradually narrowing airflow channel, and, originally it should flow according to... Figure 1 The horizontally flowing airflow shown in the figure is converted into an inclined flow along the first upward-sloping shoulder 4. This inclined flow has a vertically upward velocity component, which can prevent the downward leakage flow shown in the figure from entering the main channel and reduce the influence of the leakage flow on the suction surface 30.

[0056] refer to Figure 8 As shown, on the pressure surface 31, the gradually expanding airflow channel between the second shoulder 5 and the inner wall of the housing 1 simultaneously decelerates and obliquely guides the inflowing airflow. Thus, the inflowing airflow slows down within this gradually expanding airflow channel, and, originally it should flow according to... Figure 2The horizontally flowing airflow shown in the figure is converted into an inclined flow along the downward-sloping second shoulder 5. This inclined flow has a vertically downward velocity component, so that the airflow in the main channel can counteract the upward leakage flow shown in the figure and reduce the influence of the leakage flow on the pressure surface 31.

[0057] Comparison Figures 9a to 9d As shown in the simulated cloud map, Figure 9a and Figure 9b China Figure 1 and Figure 2 The image shows an airflow cloud diagram inside an axial flow fan without a shoulder structure. Figure 9a In the middle, the airflow within the circle clearly flows downwards at an angle. This flow intensifies the downward flow of the leaking air into the main channel, interfering with the airflow within the main channel. Figure 9b In the middle, looking from right to left (the direction of airflow into the pressure surface), the airflow inside the circle is obviously tilted upward, and this part of the airflow will pass over the top of the blade to form a leakage flow.

[0058] and Figure 9c To and Figure 7 Correspondingly, the airflow cloud diagram inside the axial fan with the first shoulder 4 on the suction surface 30 is shown. In the diagram, the airflow within the circle is relatively gentle, and the downward leakage flow is significantly weakened, so the leakage flow will not interfere with the flow of fluid in the main channel.

[0059] Figure 9d To and Figure 8 Correspondingly, the airflow cloud diagram inside the axial flow fan with the second shoulder 5 on the pressure surface 31 is shown. In the diagram, the airflow within the circle is inclined downwards along the second shoulder 5, thus preventing it from flowing upwards over the blade tip to form a leakage flow, and the leakage flow is weakened. Meanwhile, in comparison... Figure 9b and Figure 9d The vortex situation near the stationary blade is significantly reduced by the moving blade assembly with the second shoulder 5, which is also beneficial to the performance improvement of the axial flow fan.

[0060] As can be seen, adapting to the influence of airflow on the suction surface 30 and the pressure surface 31, the first shoulder 4 and the second shoulder 5 are inclined upwards and downwards respectively, arranged asymmetrically. This allows the airflow on both sides of the blade 3 to be guided differently, thereby specifically reducing the impact of leakage flow. Simultaneously, the first shoulder 4 and the second shoulder 5 are similar to a structure with two reinforcing ribs on each side of the blade 3, increasing the strength of the blade 3 with the arrangement of the two shoulders. In one embodiment, the first shoulder 4, the second shoulder 5, and the blade 3 are integrally formed.

[0061] The suction surface 30 and the pressure surface 31 of the blade 3 are both provided with shoulder structures, and the structural stability of the blade 3 is also significantly improved compared with the single-sided shoulder structure. In one embodiment, the first shoulder 4 and the second shoulder 5 have the same mass, so that the weights on both sides of the blade 3 can be made substantially the same, and its structural stability can be further improved.

[0062] As described above, when the axial flow fan is used in an occasion such as an oil fume machine where there may be oil stains or large dust, the oil stains and dirt often enter the housing 1 along the air flow and condense and accumulate on the inner wall of the housing 1. In the embodiment, the first shoulder 4 and the second shoulder 5 protrude from both sides of the blade 3, so as to be able to block the oil stains, dust, etc. between the shoulders and the hub 2 to a certain extent, and prevent them from accumulating on the inner wall of the housing 1. Thus, the gap Δh between the top of the blade 3 and the inner wall of the housing 1 can be set to a relatively small value.

[0063] Refer to Figure 5 and Figure 6 As shown in Figure 5 where it is horizontal from left to right in Figure 6 and horizontal from right to left in

[0064] In the direction of the air flow, the front ends of both the first shoulder 4 and the second shoulder 5 do not extend beyond the front end of the blade 3. In this way, the first shoulder 4 and the second shoulder 5 can be prevented from generating a disturbing flow effect on the air flow at the air inlet 10.

[0065] Further, in the direction of the air flow, the rear ends of both the first shoulder 4 and the second shoulder 5 do not extend beyond the rear end of the blade 3. As mentioned above, in the axial flow fan, a stationary blade assembly 6 is provided at the rear side of the moving blade assembly. The stationary blade assembly 6 is a stationary structure. Before the air flow enters the stationary blade assembly 6, the smaller the range of the eddy current, the more beneficial it is to improve the performance of the fan. By terminating the two shoulders before the tail of the blade 3, the interference of the shoulders on the air flow between the moving blade assembly and the stationary blade assembly 6 can be avoided, and the dynamic-static interference can be reduced.

[0066] As Figure 5As shown in the figure, in one embodiment, the vertical distance from the root to the top of the blade 3 is h, the distance between the front end of the first shoulder 4 and the top of the blade 3 is x1, and the relationship between h and x1 satisfies: 0.5h < x1 < h. As Figure 6 shown in the figure, the distance between the front end of the second shoulder 5 and the top of the blade 3 is x2, and the relationship between h and x2 satisfies: 0 < x2 < 0.5h. In this way, the positions of both the first shoulder 4 and the second shoulder 5 are located at the part of the blade 3 relatively close to the housing 1, that is, both shoulders are arranged close to the position where the leakage flow is generated, so that the leakage flow can be better improved.

[0067] Continue to refer to Figure 5 and Figure 6 shown in the figure, along the gas flow direction, the included angle between the inclined extension direction of the first shoulder 4 on the suction surface 30 and the horizontal gas flow direction is θ1, and arctan(x1 / t) > θ1 > 0. The included angle between the inclined extension direction of the second shoulder 5 on the pressure surface 31 and the horizontal gas flow direction is θ2, and arctan(x2 / t) > θ2 > 0. As described above, the two shoulders are inclined in different directions (viewed from the same side), which have completely different effects on the gas flow on both sides of the blade 3. By moderately restricting the inclination angles of the two shoulders, the gas flow can be better guided to have a sufficient impact on the leakage flow of the corresponding surface, so as to minimize the generation of leakage flow or reduce its impact as much as possible.

[0068] Combined with Figure 4 and Figure 5 the markings shown in the figure, the thickness of the first shoulder 4 and the second shoulder 5 is d, and the gap between the top of the blade 3 and the inner wall of the housing 1 is Δh. The relationship between the two parameters satisfies: 0.5 * Δh < d < 3 * Δh. In this way, by restricting the thickness d of the first shoulder 4 and the second shoulder 5 within the above range, while ensuring that the blade 3 has sufficient structural strength, it is possible to avoid the two shoulders occupying too much gas flow area.

[0069] Refer to Figure 3 、 Figure 5 shown in the figure, in the second aspect of the present invention, an axial flow fan is further provided. In addition to the moving blade assembly described in the foregoing embodiments, the axial flow fan further includes a stationary blade assembly 6. Similar to the moving blade assembly, the stationary blade assembly 6 also includes stationary blade vanes 61, a stationary blade housing 62, and a stationary blade hub 63. Different from the moving blade assembly, the two ends of the stationary blade vanes 61 are generally connected to the stationary blade hub 63 and the stationary blade housing 62 respectively.

[0070] In one embodiment, for the convenience of the assembly, maintenance, etc. of the axial flow fan, the stationary blade housing 62 and the housing 1 in the moving blade are separately manufactured and assembled to form an integral axial flow fan housing structure.

[0071] Furthermore, a third aspect of the present invention provides a range hood having the axial flow fan described in the foregoing embodiments.

[0072] The technical features of the above-described embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0073] Those skilled in the art should recognize that the above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Any appropriate changes and variations made to the above embodiments within the essential spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A rotor blade assembly, characterized by The moving blade assembly comprises: a housing (1) and a hub (2) arranged in the housing (1); a plurality of blades (3) arranged in a central symmetry with the axis of revolution of the hub (2) as the center, the tip of the blade (3) being arranged in a spaced manner with the inner wall of the housing (1), the blade (3) having a suction surface (30) and a pressure surface (31); a first shoulder (4) protruding on the suction surface (30), the first shoulder (4) extending upwardly on the suction surface (30) in the flow direction of the airflow, so that a gradually tapered airflow passage is formed between the first shoulder (4) and the inner wall of the housing (1); and a second shoulder (5) protruding on the pressure surface (31), the second shoulder (5) extending downwardly on the pressure surface (31) in the flow direction, so that a gradually expanding airflow passage is formed between the second shoulder (5) and the inner wall of the housing (1).

2. The blade assembly of claim 1, wherein, The first shoulder (4) and the second shoulder (5) have the same mass, and / or the first shoulder (4), the second shoulder (5) and the blade (3) are integrally formed.

3. The blade assembly of claim 1, wherein, In the flow direction, the front end of the first shoulder (4) and the front end of the second shoulder (5) do not exceed the front end of the blade (3).

4. The blade assembly of claim 3, wherein, In the flow direction, the rear end of the first shoulder (4) and the rear end of the second shoulder (5) do not exceed the rear end of the blade (3).

5. The blade assembly of claim 4, wherein, In the flow direction, the length of the first shoulder (4) and the length of the second shoulder (5) are both a, and the length of the blade (3) corresponding to the positions where the first shoulder (4) and the second shoulder (5) are arranged is t, and the relationship between a and t satisfies the following relationship: 0.8t 6. The blade assembly of any one of claims 1-5, wherein, The vertical distance from the root of the blade (3) to the top of the blade (3) is h, the distance between the front end of the first shoulder (4) and the top of the blade (3) is x1, and the relationship between h and x1 satisfies the following relationship: 0.5h The vertical distance from the root of the blade (3) to the top of the blade (3) is h, the distance between the front end of the second shoulder (5) and the top of the blade (3) is x2, and the relationship between h and x2 satisfies the following relationship: 0 7. The blade assembly of claim 6, wherein, In the flow direction, the length of the blade (3) is t; The angle between the inclined extension direction of the first shoulder (4) on the suction surface (30) and the flow direction is θ1, and arctan(x1 / t)>θ1>0; The angle between the inclined extension direction of the second shoulder (5) on the pressure surface (31) and the flow direction is θ2, and arctan(x2 / t)>θ2>0.

8. The blade assembly of any one of claims 1-5, wherein, The thickness of the first shoulder (4) and the second shoulder (5) is d, the gap between the top of the blade (3) and the inner wall of the housing (1) is Δh, and 0.5*Δh 9. An axial flow fan characterised in that, The axial flow fan comprises the moving blade assembly according to any one of claims 1-8 and a stationary blade assembly (6).

10. A range hood characterized by The range hood includes the axial flow fan recited in claim 9.

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