Fan blade structure and axial flow fan

Abstract

The utility model discloses a kind of fan blade structure and axial flow fan, belong to fluid conveying technical field.Its fan blade structure includes several blades and hub, blade is vertically installed on hub, and blade is evenly distributed along the outside lateral of hub;Blade has center line, and the geometric shape of blade meets axial center symmetry;On the section parallel to the axis of hub, center line is located at the center position of vertical section, and center line vertically passes through the vertical section of blade;The axial flow fan of the utility model replaces double fan blade structure by above-mentioned fan blade structure, realizes the high symmetry of positive and negative air supply performance, effectively promotes bidirectional ventilation efficiency, significantly reduces equipment volume and energy consumption under same power, improves the stability of whole machine operation.

Description

Technical Field

[0001] This utility model relates to the field of fluid transport technology, and in particular to a fan blade structure and an axial flow fan. Background Technology

[0002] As a crucial device for indoor air exchange in buildings, the core component of a fresh air system, the axial flow fan, drives airflow, extends the air volume within the duct, and achieves effective exchange of indoor and outdoor air. With increasingly stringent requirements for indoor air quality, existing fresh air systems now incorporate bidirectional ventilation to ensure efficient air circulation. In this context, traditional axial flow fans with unidirectional blades are insufficient to meet the demands of bidirectional airflow regulation. Even with forced forward and reverse rotation of a single blade, the airflow difference between forward and reverse rotation can exceed 20%, failing to guarantee consistent bidirectional ventilation.

[0003] Therefore, such as Figure 1 As shown, traditional axial flow fans adopt a single motor-driven dual-blade collaborative design, which leads to increased equipment size, higher equipment cost, and more complex installation. Consequently, traditional axial flow fans are less efficient than ordinary fans, both in terms of assembly and air volume. This limits the operating efficiency of axial flow fans in fresh air systems, making it difficult to meet the dual requirements of energy saving and efficient air delivery. Utility Model Content

[0004] The technical problem to be solved by this utility model is: in order to solve the problems of uneven air volume, low efficiency and complex structure of traditional axial flow fans in bidirectional ventilation in fresh air systems, this utility model provides an axial flow fan for use in fresh air systems. By optimizing the fan blade structure, it achieves a high degree of symmetry in forward and reverse air supply performance, effectively improves bidirectional ventilation efficiency, replaces the dual-fan structure, significantly reduces equipment size and energy consumption under the same power, and improves the overall operational stability of the machine.

[0005] The technical solution adopted by this utility model to solve its technical problem is: a wind turbine structure, including a number of blades and a hub, wherein the blades are vertically mounted on the hub and the blades are evenly distributed along the outer circumference of the hub. On the radially bisected section of the hub, the blade has an asymmetrical airfoil structure, that is, the shape of the two sides of the blade chord is asymmetrically arranged; The blade's geometry satisfies axial central symmetry. On the plane parallel to the hub axis and dividing the blade, the vertical cross-section of the blade has a center of symmetry, and the centers of symmetry of each vertical cross-section form a centerline; that is, the centerline is located at the center of the vertical cross-section and passes perpendicularly through it. Therefore, the asymmetric airfoil blade exhibits directional aerodynamic characteristics. Specifically, during forward rotation, the airfoil camber matches the airflow direction, resulting in greater thrust; during reverse rotation, the camber is opposite to the airflow direction, significantly reducing thrust and directly causing airflow differences. In contrast, the central symmetric structure ensures that the airflow channel shape is completely consistent during both forward and reverse rotation. This design effectively counteracts directional influences and eliminates bidirectional airflow differences. Simultaneously, the centrally symmetrical design ensures that the forces exerted on the airflow by the blades on both sides are completely symmetrical during rotation, preventing additional radial forces or torques caused by force imbalance. This balancing performance significantly reduces the vibration amplitude during blade rotation, thereby reducing structural resonance and noise caused by vibration, and improving operational stability and service life. Furthermore, the centrally symmetrical structure allows for a more uniform distribution of mass and stress on the blades, avoiding localized stress concentration. Symmetrical blades can more evenly withstand airflow impacts and centrifugal forces, reducing the risk of damage such as blade deformation and cracks, and significantly improving the overall structural durability.

[0006] Furthermore, on the radially segmented section of the hub, the airfoil thickness of the blade is uniformly distributed, or gradually decreases from the root to the tip, making the airfoil thickness approximately uniform. Compared to existing blade designs with non-uniform thickness distribution, this homogenization avoids local "thin-thick" boundary zones, resulting in a more balanced stress distribution when the material is subjected to rotational centrifugal force and airflow impact pressure. This reduces the risk of cracks and deformation caused by stress concentration, significantly improving fatigue life and reducing maintenance costs. Simultaneously, the uniform or near-uniform thickness design simplifies mold manufacturing and blade forming processes, reducing production costs and improving the consistency and yield of mass production. Moreover, in the low-turbulence airflow environment of the fresh air system, the uniform thickness airfoil provides greater stability. When airflow passes through, boundary layer separation is more controllable, less prone to turbulence amplification due to sudden changes in local thickness, thus reducing drag fluctuations and ensuring the uniformity of the output airflow.

[0007] Furthermore, on the radial plane of the hub, the root projections between adjacent blades have no overlapping area, while the outer edge projections between adjacent blades do overlap. Existing wind turbine structures have overlapping projections of the blade roots on the radial plane, creating localized obstruction. During rotation, this overlapping area hinders airflow, causing airflow to accumulate and backflow near the root, forming vortices. This design eliminates the overlapping root projections, reserving a smoother flow path for airflow. Airflow can flow evenly along the outer edge of the root, reducing drag losses caused by obstruction and simultaneously reducing vibration and noise caused by turbulence, indirectly improving the aerodynamic efficiency of the blades. The overlapping outer edge projections ensure that the airflow does not decrease due to the reduced area of ​​individual blades, while effectively reducing the vortex area, thereby improving the overall efficiency of the wind turbine.

[0008] Furthermore, the root length of the leaf is less than the outer edge length, so that the leaf gradually expands from the root to the outer edge.

[0009] Furthermore, the number of blades is defined as n, the arc length of the root of the blade projected onto the radial plane of the hub is l, and the diameter of the hub is d. In order to ensure that the projections of the roots of adjacent blades onto the radial plane of the hub do not overlap, the geometric relationship must be satisfied: l < πd / n.

[0010] Furthermore, the blades are symmetrically S-shaped, with the S-curve smoothly transitioning along the blade axis. This allows for gradual airflow guidance as the airflow passes through the blade channel, effectively reducing the risk of airflow separation. While maintaining symmetry, this structure optimizes the pressure distribution on the blade surface, further reducing wind resistance fluctuations and improving airflow efficiency. The S-shaped design also enhances the structural toughness of the blades, enabling them to maintain deformation stability even under high-speed rotation. This prevents aerodynamic balance disruption due to elastic deformation, thereby ensuring the long-term quiet operation and reliability of the fresh air system.

[0011] Furthermore, the root length of the blade is equal to the outer edge length, the S-shape of the root of the blade tends to be vertical, and the S-shape of the outer edge of the blade tends to be horizontally extended; so that the roots of adjacent blades maintain sufficient spacing in the axial projection, while the outer edges of the blades form an overlapping pattern in the axial projection.

[0012] Furthermore, a guide cone is provided at one end of the hub, and the guide cone is integrally formed coaxially with the hub. Compared with the traditional structure where the hub and guide cone are installed separately, the integral design eliminates connection gaps, avoids airflow disturbance and eddy current loss caused by assembly errors, and further improves air intake efficiency. Under the high-speed operation of the fresh air system, the streamlined profile of the guide cone can effectively guide the airflow to converge smoothly along the axial direction, reduce radial turbulence and energy loss, and improve the overall ventilation efficiency. At the same time, the integral structure enhances the connection strength between the hub and the guide cone, avoids loosening or fatigue cracking caused by vibration during high-speed rotation, and significantly improves operational safety and durability.

[0013] Furthermore, the guide cone is positioned in the forward rotation direction of the fan blade structure, so that it can fully exert its guiding effect when the fan is rotating forward, optimize the pre-swirl direction of the airflow, and reduce the separation loss caused by the mismatch of the intake angle of attack.

[0014] An axial flow fan for use in a fresh air system includes: The impeller with the above-described blade structure is used to generate airflow and achieve efficient and low-noise gas transport. An electric motor for driving an impeller to rotate; the electric motor includes a stator assembly and a rotor assembly, the rotor assembly being rotatably disposed inside the stator assembly; Ductwork is used to guide the airflow generated by the impeller for directional transport. in: The motor and impeller are coaxially arranged and both are located inside the duct. One end of the rotor assembly extends into the hub and is fixedly connected to the hub. The stator assembly is located outside the hub and is fixedly connected to the inner wall of the duct. In traditional axial flow fans, the blade root projections overlap, which blocks the airflow path between the motor and the outside, resulting in obstructed heat dissipation and increased temperature, thus affecting the lifespan and operational stability. This structure, however, ensures that the blade root projections on the radial plane of the hub do not overlap, allowing airflow to flow directly over the motor surface through the gap between the roots, accelerating heat exchange, effectively reducing the motor's operating temperature, and making it more suitable for the relatively enclosed working environment of a fresh air system. Furthermore, the impeller blades have a gap between the inner walls of the duct, ensuring no frictional contact when the impeller rotates at high speed, while reducing airflow leakage losses.

[0015] The beneficial effects of this invention are that the impeller structure features asymmetrical airfoil blades with a centrally symmetrical axial profile. This centrally symmetrical design ensures stable aerodynamic performance of the impeller under both forward and reverse rotation conditions, avoiding localized stress concentration and improving the reliability and adaptability of the fan operation. Furthermore, the centrifugal forces of each blade cancel each other out during rotation, eliminating the need for additional counterweight adjustments. This not only reduces additional wear on core components such as the shaft and bearings but also reduces additional energy loss caused by imbalance during equipment operation, indirectly improving the system's operating efficiency and lifespan.

[0016] This invention features a wind turbine blade structure with uniformly thick airfoil blades, which are easier to manufacture and inspect than traditional variable cross-section blades, reducing production costs. Simultaneously, the uniform thickness design avoids localized "thin-thickness" boundary zones, resulting in a more even stress distribution when the material is subjected to rotational centrifugal force and airflow impact pressure, reducing the risk of cracks and deformation caused by stress concentration. In the low-turbulence airflow environment of a fresh air system, the uniformly thick airfoil provides greater stability. Boundary layer separation is more controllable as airflow passes through, reducing the likelihood of turbulence amplification due to sudden changes in local thickness, thereby minimizing drag fluctuations and ensuring the uniformity of the output airflow.

[0017] The blade structure of this invention, in terms of axial projection, shows no overlap at the root of adjacent blades even when there is overlap at the edges. Compared to existing blade root projection overlap structures, this design provides a smoother channel for airflow, allowing airflow to flow evenly along the outer side of the root, reducing drag loss caused by obstruction, resulting in a smaller vortex area, and simultaneously reducing vibration and noise caused by turbulence, indirectly improving the aerodynamic efficiency of the blades. In the fresh air system, airflow can flow directly over the motor surface through the gap between the roots, accelerating heat exchange and effectively reducing the motor's operating temperature.

[0018] The axial flow fan of this invention features asymmetric airfoil blades that optimize the pressure difference distribution between the pressure and suction surfaces while ensuring high aerodynamic performance, thus reducing flow separation. Combined with a centrally symmetrical layout, the fan maintains good airflow and static pressure output in both bidirectional operation modes, adapting to the frequent start-stop and variable operating conditions of fresh air systems. The overall structure is compact, making it easy to integrate into small installation spaces, and by reducing mechanical vibration and aerodynamic noise, it significantly improves indoor air quality and user comfort. Attached Figure Description

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] Figure 1 This is a three-dimensional schematic diagram of an existing dual-blade axial flow motor.

[0021] Figure 2 This is a three-dimensional schematic diagram of the blade structure in this utility model.

[0022] Figure 3 yes Figure 2 A three-dimensional schematic diagram of a single blade.

[0023] Figure 4 yes Figure 2 A front view of the overall structure.

[0024] Figure 5 This is a front view schematic diagram of an existing single-blade axial flow motor.

[0025] Figure 6 yes Figure 2 A bottom view of the overall structure.

[0026] Figure 7 This is a three-dimensional schematic diagram of the wind turbine blade structure viewed from below.

[0027] Figure 8 yes Figure 4 A schematic cross-sectional view at section A.

[0028] Figure 9 yes Figure 4 A schematic diagram of the structure of a single blade at section A.

[0029] Figure 10 Is adopted Figure 2 A three-dimensional assembly drawing of an axial flow fan with a medium-sized blade structure.

[0030] Figure 11 yes Figure 10 Assembly diagram of a axial flow fan (partially cut open duct).

[0031] Figure 12 This is a flow field simulation diagram of a traditional axial flow fan.

[0032] Figure 13 This is a flow field simulation diagram of the axial flow fan of this utility model.

[0033] Figure 14 This is a flow field analysis diagram of a traditional axial flow fan.

[0034] Figure 15 This is a flow field analysis diagram of the axial flow fan of this utility model.

[0035] In the diagram: 1. Impeller; 11. Hub; 12. Guide cone; 13. Blade; 2. Motor; 3. Duct; 41. Vortex I; 42. Vortex II; 43. Deceleration zone I; 44. Deceleration zone II. Detailed Implementation

[0036] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the present invention, and therefore only show the components relevant to the present invention.

[0037] Example 1: like Figure 10 , Figure 11 and Figure 2 The image shown is a preferred embodiment of this utility model, an axial flow fan applied in a fresh air system, comprising: An impeller 1 is used to generate airflow and realize gas transport. The impeller 1 includes a number of blades 13 and a hub 11. The blades 13 are vertically mounted on the hub 11 and the blades 13 are evenly distributed along the outer circumference of the hub 11. Motor 2 is used to provide power for the rotation of impeller 1. Motor 2 includes a stator assembly and a rotor assembly. The stator assembly is fixed to the inner wall of the air duct 3, and one end of the rotor assembly is located inside the hub 11 and is fixedly connected to the hub 11. Duct 3 is used to guide the airflow direction and enhance the overall structural stability. Impeller 1 and motor 2 are located inside duct 3, and stator assembly is fixedly connected to the inner wall of duct 3. Therefore, inside the duct 3, the motor 2 drives the hub 11 and blades 13 to rotate synchronously through the rotor assembly, thereby achieving efficient airflow output; the motor 2 can operate in both directions to adapt to the bidirectional ventilation requirements of the fresh air system.

[0038] Reference Figure 2 , Figure 4 , Figure 8 and Figure 9 On the radial section of the impeller 1 hub 11, the blade 13 has an asymmetrical airfoil structure, that is, the shape of the two sides of the airfoil chord of the blade 13 is asymmetrically set. Similar to the existing wind turbine structure, the blade 13 with the asymmetrical airfoil structure has a large thrust when rotating forward and the airfoil camber matches the airflow direction. When rotating backward, the camber is opposite to the airflow direction and the thrust decreases significantly, which directly leads to the difference in air volume.

[0039] To meet the bidirectional airflow requirements of the fresh air system, this embodiment optimizes the structure of blade 13 to minimize the difference in airflow between forward and reverse rotation, thereby achieving efficient bidirectional airflow. The specific details are as follows: like Figures 2-4As shown, on any plane parallel to the axis of hub 11 and dividing the blade 13, the blade 13 is symmetrically S-shaped, with the center of the S-shape being the center of symmetry. Each plane parallel to the axis of hub 11 and dividing the blade 13 has a center of symmetry, and these centers of symmetry form a centerline, ensuring that the geometry of the blade 13 satisfies axial central symmetry. Furthermore, the centerline perpendicularly passes through and bisects the vertical section of the blade 13. Thus, axial central symmetry ensures that the airflow channel shape of the asymmetrical airfoil structure blade 13 is completely consistent in both forward and reverse rotation, effectively counteracting directional influences and eliminating bidirectional airflow differences. Meanwhile, the centrally symmetrical design ensures that the forces exerted on the airflow by the blades 13 on both sides are completely symmetrical when the blades 13 rotate, avoiding additional radial forces or torques caused by force imbalance. This balancing performance significantly reduces the vibration amplitude of the blades 13 during rotation, thereby reducing structural resonance and noise caused by vibration, and improving operational stability and service life. In addition, the centrally symmetrical structure makes the mass distribution and stress distribution of the blades 13 more uniform, avoiding local stress concentration. The symmetrical blades 13 can more evenly bear the impact of airflow and centrifugal force, reducing the risk of damage such as deformation and cracks of the blades 13, and significantly improving the durability of the overall structure.

[0040] in: The axial profile thickness of blade 13 can gradually decrease from the center to the edge, or it can be like... Figure 3 As shown, the axial profile thickness of blade 13 remains the same. The same thickness design helps to simplify the mold processing technology, reduce manufacturing costs, and improve the overall structural strength of the blade. Especially under high-speed rotation conditions, it can effectively resist the deformation caused by centrifugal force.

[0041] Reference Figure 8 , Figure 9 On the radially segmented section of the hub 11, the airfoil thickness of the blade 13 can be uniformly or approximately uniformly set, meaning the width of the radially segmented section of the blade 13 remains consistent from the center to the edge or decreases slightly. Compared to the non-uniform thickness distribution design of existing wind turbine blade structures (i.e., the radially segmented section width shortens significantly from the root to the tip), this homogenization or near-homogenization treatment avoids local "thin-thick" interface areas, resulting in a more balanced stress distribution when the material is subjected to rotational centrifugal force and airflow impact pressure. This reduces the risk of cracks and deformation caused by stress concentration, significantly improving its fatigue life and reducing maintenance costs. Simultaneously, the uniform thickness design simplifies mold manufacturing and blade forming processes, reduces production costs, and improves the consistency and yield of batch manufacturing.

[0042] Reference Figure 12 The flow field simulation diagram of the conventional axial flow fan (with uneven thickness) shown is compared with Figure 13The diagram shown is a flow field simulation of an axial flow fan (uniform thickness) under the same operating conditions in this embodiment. In this simulation, the existing blades generate vortex 1 (41) during operation, while the blade 13 in this embodiment generates vortex 2 (42) under the same operating conditions. Figure 12 and Figure 13 The comparison shows that the intensity and distribution range of Vortex 2 42 are significantly smaller than those of Vortex 1 41, indicating that a uniformly thick airfoil is more stable in the low-turbulence environment of the fresh air system. When airflow passes through, boundary layer separation is more controllable, and turbulence is less likely to intensify due to sudden changes in local thickness, thus reducing drag fluctuations and ensuring the uniformity of the output airflow.

[0043] Example 2: Based on Example 1, the structure of impeller 1 is further optimized, as follows: Reference Figures 2-3 The hub 11 has a guide cone 12 at one end of the fan blade structure in the forward rotation direction. The guide cone 12 is integrally formed coaxially with the hub 11. Compared with the traditional separate installation structure of hub 11 and guide cone 12, the integral design eliminates connection gaps, avoids airflow disturbance and eddy current loss caused by assembly errors, and improves air intake efficiency. Under the high-speed operation of the fresh air system, the streamlined profile of the guide cone 12 can effectively guide the airflow to converge smoothly along the axial direction, reduce radial turbulence and energy loss, and improve the overall ventilation efficiency. At the same time, the integral structure enhances the connection strength between hub 11 and guide cone 12, avoids loosening or fatigue cracking caused by vibration during high-speed rotation, and significantly improves operational safety and durability.

[0044] Example 3: Refer to Figure 5 In traditional axial flow fans, the roots and tips of adjacent blades overlap in the radial projection of the hub. When the axial flow fan rotates, this overlapping area obstructs airflow, causing airflow to accumulate and backflow near the roots, forming vortices. These vortices significantly increase flow resistance, reduce fan efficiency, and induce localized vibration and noise. To eliminate this adverse effect, this embodiment optimizes the blade layout based on Embodiment 2: the roots of adjacent blades 13 are staggered in the radial projection of the hub 11, preventing overlap and effectively avoiding airflow accumulation and backflow in the root region, significantly weakening vortex intensity and reducing flow resistance. Furthermore, the outer edge projections of adjacent blades 13 are partially overlapped. For the impeller 1 as a whole, this ensures that the airflow does not decrease due to the reduced area of ​​a single blade 13, while effectively reducing the vortex area, thereby improving the overall efficiency of the fan. The specific solution is as follows: Reference Figure 4 Let n be the number of blades 13, l be the arc length of the root of blade 13 projected onto the radial plane of hub 11, and d be the diameter of hub 11. In this embodiment, the axial dimension (i.e., arc length l) of the root of the blade 13 is reduced so that the root length of the blade 13 is less than the outer edge length, that is, the blade 13 gradually expands from the root to the outer edge; in order to ensure that the projections of the roots of adjacent blades 13 on the radial plane of the hub 11 do not overlap, the geometric relationship must be satisfied: l < πd / n.

[0045] Thus we get: Figure 6 , Figure 7 As shown, on the radial plane of the hub 11, there is no overlap in the root projections between adjacent blades 13 (see reference). Figure 6 (Most of the middle circle is extended), there is an overlapping area in the outer edge projection between adjacent blades 13 (refer to...) Figure 7 (The part circled in the middle).

[0046] Reference Figure 14 The flow field analysis diagram of the conventional axial flow fan (with overlapping projections at the blade roots) shown is compared with... Figure 15 The flow field simulation diagram of the axial flow fan (with staggered blade roots) of this embodiment is shown. In the conventional axial flow fan, a deceleration region 43 is generated behind it during operation. In this embodiment, under the same operating conditions, a second deceleration region 44 is generated behind it. The comparison shows that the second deceleration region 44 is significantly smaller than the first deceleration region 43, indicating that the airflow is smoother after the blade roots are staggered, and the backflow phenomenon is significantly reduced. The airflow recovers its speed faster after leaving the blades, resulting in less energy loss and effectively improving the overall aerodynamic efficiency of the fan. Simultaneously, the non-overlapping root projection design makes the pressure distribution more uniform, avoiding the formation of local low-pressure areas and further suppressing vortex development. This optimized structure not only reduces wind noise but also improves the system's operational stability.

[0047] In addition, refer to Figure 11 The stator assembly of motor 2 is located below impeller 1, and the radial diameter of the stator assembly is larger than the diameter of hub 11. Along the axial projection, the roots of its blades 13 are arranged around motor 2. If a traditional axial flow fan is used, the overlapping projections of its blade roots will block the airflow path between motor 2 and the outside, resulting in obstructed heat dissipation and increased temperature of the stator assembly of motor 2, thus affecting its lifespan and operational stability. However, this structure ensures that the projections of the roots of blades 13 on the radial plane of hub 11 do not overlap, allowing airflow to flow directly over the surface of motor 2 through the gaps between the roots, accelerating heat exchange, effectively reducing the operating temperature of motor 2, and making it more suitable for the relatively enclosed working environment of fresh air systems.

[0048] Example 4: Based on the theory of Example 3, an alternative structure to the scheme of Example 3 is proposed, as follows: Reference Figure 4Let n be the number of blades 13, l be the arc length of the root of the blade 13 projected onto the radial plane of the hub 11, and d be the diameter of the hub 11. In order to ensure that the projections of the roots of adjacent blades 13 onto the radial plane of the hub 11 do not overlap, the geometric relationship must be satisfied: l < πd / n. The root length of blade 13 is equal to the outer edge length. The S-shape of the root of blade 13 tends to be vertical, while the S-shape of the outer edge of blade 13 tends to be horizontally extended. That is, from the axial direction, the angle formed by the root of blade 13 and the axis of hub 11 is smaller than the angle formed by the outer edge of blade 13 and the axis of hub 11. Thus, it is also possible to achieve that the roots of adjacent blades 13 have no overlapping area in the projection, while the outer edges of blades 13 form an overlapping area in the projection.

[0049] It should be noted that the impeller 1 with the blade 13 structure described above is not only applicable to the axial flow fan of this embodiment, but can also be extended to other types of ventilation equipment or fluid transport systems; in addition, the fixed connection mentioned in the above embodiment can be a direct contact fixation or a fixation can be achieved through an intermediate component connection.

[0050] Based on the above-described preferred embodiments of this utility model, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the technical concept of this utility model. The technical scope of this utility model is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A wind turbine blade structure, characterized in that: It includes several blades (13) and a hub (11), wherein the blades (13) are vertically mounted on the hub (11) and the blades (13) are evenly distributed circumferentially along the outer side of the hub (11); in: The blade (13) has a centerline, and the geometry of the blade (13) satisfies axial central symmetry. On the plane parallel to the axis of the hub (11) and dividing the blade (13), the centerline is located at the center of the vertically divided section, and the centerline passes perpendicularly through the vertically divided section of the blade (13).

2. The wind turbine blade structure as described in claim 1, characterized in that: On the radially split section of the hub (11), the blade (13) has an asymmetric airfoil structure, and the airfoil thickness of the blade (13) is uniformly set or gradually decreases from the root to the tip.

3. The wind turbine blade structure as described in claim 2, characterized in that: The axial profile thickness of the blade (13) gradually decreases or remains constant from the center to the edge.

4. The wind turbine blade structure as described in claim 3, characterized in that: On the radial plane of the hub (11), there is no overlap in the root projection between adjacent blades (13), but there is an overlap in the outer edge projection between adjacent blades (13).

5. The wind turbine blade structure as described in claim 4, characterized in that: The number of blades (13) is defined as n, the arc length of the root of the blade (13) projected onto the radial plane of the hub (11) is l, and the diameter of the hub (11) is d. In order to ensure that the projections of the roots of adjacent blades (13) onto the radial plane of the hub (11) do not overlap, the geometric relationship must be satisfied: l < πd / n.

6. The wind turbine blade structure as described in claim 1, characterized in that: One end of the hub (11) is provided with a guide cone (12), which is set in the positive rotation direction of the wind turbine structure. The guide cone (12) is coaxially and integrally formed with the hub (11).

7. The wind turbine blade structure as described in claim 4, characterized in that: The root length of the leaf (13) is less than the outer edge length, and the leaf (13) has a gradually expanding shape from the root to the outer edge.

8. The wind turbine blade structure as described in claim 4, characterized in that: On a cross section parallel to the axis of the hub (11), the blade (13) is symmetrically S-shaped; the root length of the blade (13) is equal to the outer edge length, the root S-shape of the blade (13) tends to be vertical, and the outer edge S-shape of the blade (13) tends to be laterally extended.

9. An axial flow fan, used in a fresh air system, characterized in that, include: Impeller (1), wherein the impeller (1) adopts the wind turbine structure described in any one of claims 1-8; The motor (2) is used to drive the impeller (1) to rotate; the motor (2) includes a stator assembly and a rotor assembly, the rotor assembly being rotatably disposed inside the stator assembly; Duct (3) is used to guide the airflow generated by the impeller (1) for directional transport; Wherein: the motor (2) and the impeller (1) are coaxially arranged and both are located inside the air duct (3); one end of the rotor assembly extends into the interior of the hub (11) and is fixedly connected to the hub (11); the stator assembly is located outside the hub (11) and is fixedly connected to the inner wall of the air duct (3).

10. The axial flow fan as described in claim 9, characterized in that: There is a gap between the blade (13) and the inner wall of the duct (3).

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