Fan blade and fan

Abstract

The utility model belongs to the field of fans, and particularly relates to a fan blade and a fan, the suction surface and the pressure surface of the fan blade are both provided with smooth and concave flow channels, the flow channels extend in the curve direction connecting the front edge and the tail edge of the fan blade, and the multiple flow channels distributed in the radial direction of the fan blade form a wave-shaped structure; according to the structure, the flowing path of airflow passing through the fan blades is optimized, turbulence and resistance are reduced, the airflow is smoother and more stable, and therefore noise generated by airflow turbulence during operation of the fan is effectively reduced.

Description

Technical Field

[0001] This application relates to the field of fans, and more particularly to a fan blade and a fan. Background Technology

[0002] Fans are based on aerodynamic principles, using an electric motor to drive the blades to rotate and generate directional airflow, thereby accelerating the movement of surrounding air. This design not only achieves effective cooling but also enhances ventilation within a space. Fans have an extremely wide range of applications, from regulating indoor temperature and increasing air circulation in homes and offices, to cooling computer cases, and even providing ventilation in large spaces such as factory workshops and warehouses, ensuring a comfortable working environment and the safe operation of equipment.

[0003] Currently, fan blade structures are diverse, including straight airfoil, curved airfoil (bent backward), forward-curved airfoil, and adjustable airfoil designs. These blades, through unique blade shapes and angles, combined with the arrangement of blades, blade supports, and blade shrouds, achieve efficient airflow generation, meeting the needs of various application scenarios.

[0004] However, current fans cause significant operating noise due to vibrations caused by the interaction between the high-speed rotating blades and the air. Utility Model Content

[0005] This application provides a fan blade and a fan to solve the problem of excessive operating noise caused by the vibration of the high-speed rotating fan blades interacting with the air during operation.

[0006] In a first aspect, embodiments of this application provide a fan blade, comprising: both the suction surface and the pressure surface of the fan blade have smooth, recessed flow channels, the flow channels are directed along a curved direction connecting the leading edge and the trailing edge of the fan blade, and a plurality of the flow channels distributed radially along the fan blade constitute a wave-shaped structure.

[0007] As an optional implementation, the fan blade provided in this application has a flow channel that is recessed from the leading edge of the fan blade and transitions smoothly to the middle portion of the fan blade until there is no recess.

[0008] As an optional implementation, the fan blade provided in this application has a flow channel that is concave from the leading edge of the fan blade, transitions smoothly to no concavity in the middle portion of the fan blade, and then concave again from the middle portion of the fan blade and continues to the trailing edge of the fan blade.

[0009] As an optional implementation, the fan blade provided in this application has a flow channel that is recessed from the middle portion of the fan blade and extends to the trailing edge of the fan blade.

[0010] As an optional implementation, the fan blade provided in this application has a flow channel that is recessed from the leading edge of the fan blade and extends to the trailing edge of the fan blade.

[0011] As an optional implementation, the fan blade provided in this application has a flow channel that gradually narrows from the edge of the fan blade toward the center.

[0012] As an optional implementation, the fan blade provided in this application has the flow channel oriented along the circumference of the fan blade.

[0013] As an optional implementation, the fan blade provided in this application has a wave-shaped structure that is a periodically repeating wave shape.

[0014] As an optional implementation, the fan blade provided in this application has a periodic repeating wave shape that is a sine curve shape or a near-sine curve shape.

[0015] Secondly, embodiments of this application provide a fan including the fan blades described in any of the claims in the first aspect above.

[0016] This application provides a fan blade and a fan, wherein both the suction surface and the pressure surface of the fan blade have smooth concave flow channels. The flow channels run along the curved direction connecting the leading edge and trailing edge of the fan blade, and multiple flow channels distributed radially along the fan blade form a wave-shaped structure. This structure optimizes the flow path of airflow through the fan blade, reduces turbulence and resistance, and makes the airflow smoother and more stable, thereby effectively reducing the noise generated by airflow turbulence during fan operation. Attached Figure Description

[0017] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0018] Figure 1 Schematic diagram of the fan blades provided in this application Figure 1 ;

[0019] Figure 2 Schematic diagram of the fan blades provided in this application Figure 2 ;

[0020] Figure 3 Schematic diagram of the fan blades provided in this application Figure 3 ;

[0021] Figure 4 Schematic diagram of the fan blades provided in this application Figure 4 ;

[0022] Figure 5 Schematic diagram of the fan blades provided in this application Figure 5 .

[0023] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments.

[0024] Reference numerals: 1. Suction surface; 2. Pressure surface; 3. Flow channel; 4. Leading edge; 5. Trailing edge. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] First, those skilled in the art should understand that these embodiments are merely for explaining the technical principles of this utility model and are not intended to limit the scope of protection of this utility model. Those skilled in the art can make adjustments as needed to adapt to specific application scenarios.

[0027] Secondly, it should be noted that in the description of this utility model, the terms "inner" and "outer," etc., which indicate the direction or positional relationship, are based on the direction or positional relationship shown in the accompanying drawings. This is only for the convenience of description and does not indicate or imply that the device or component must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this utility model.

[0028] Furthermore, it should be noted that, in the description of this utility model, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; 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; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0029] Fans are based on aerodynamic principles, using an electric motor to drive the blades to rotate and generate directional airflow, thereby accelerating the movement of surrounding air. This design not only achieves effective cooling but also enhances ventilation within a space. Fans have an extremely wide range of applications, from regulating indoor temperature and increasing air circulation in homes and offices, to cooling computer cases, and even providing ventilation in large spaces such as factory workshops and warehouses, ensuring a comfortable working environment and the safe operation of equipment.

[0030] Currently, fan blade structures are diverse, including straight airfoil, curved airfoil (bent backward), forward-curved airfoil, and adjustable airfoil designs. These blades, through unique blade shapes and angles, combined with the arrangement of blades, blade supports, and blade shrouds, achieve efficient airflow generation, meeting the needs of various application scenarios.

[0031] However, current fans cause significant operating noise due to vibrations caused by the interaction between the high-speed rotating blades and the air.

[0032] To address the aforementioned issues, this application provides a fan blade and a fan, comprising a fan blade with a smooth, recessed flow channel 3. The flow channel 3 on the suction surface 1 and the pressure surface 2 is designed to run along the curved direction from the leading edge 4 to the trailing edge 5 of the fan blade, and multiple radially distributed flow channels 3 form a wave-shaped structure. This structure optimizes the flow path of airflow through the fan blade, reduces turbulence and resistance, and makes the airflow smoother and more stable, thereby effectively reducing the noise generated by airflow turbulence during fan operation.

[0033] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0034] This application provides a fan blade, such as Figures 1 to 5 As shown, in this embodiment, a fan blade has a smooth, recessed flow channel 3 on both the suction surface 1 and the pressure surface 2. The flow channel 3 is directed along the curve connecting the leading edge 4 and the trailing edge 5 of the fan blade, and multiple flow channels 3 distributed radially along the fan blade form a wave-shaped structure.

[0035] Both the suction surface 1 and pressure surface 2 of the fan blade have smoothly recessed flow channels 3. These flow channels 3 do not extend in a straight line, but follow a curved path connecting the leading edge 4 and trailing edge 5 of the fan blade. Specifically, multiple flow channels 3 distributed radially along the fan blade together form a wave-shaped structure, where radial refers to the direction radiating outward from the center of rotation of the fan blade. This arrangement allows airflow to pass more smoothly through the fan blade surface, reducing turbulence and drag.

[0036] The wavy flow channel 3 is designed to improve the aerodynamic performance of the fan blades. By designing the shape and orientation of the flow channel 3, airflow can be guided more effectively, reducing friction between the airflow and the fan blade surface, and consequently, energy loss. Furthermore, this structure effectively reduces airflow separation, further improving the fan blade's efficiency. The wavy structure not only helps improve airflow characteristics but also enhances the mechanical strength and stability of the fan blades themselves to a certain extent.

[0037] The wave-shaped flow channel design of the fan blades also helps to increase their natural frequency. The natural frequency is the natural frequency of an object's vibration, while a fan generates a specific excitation frequency during operation. If the natural frequency of the fan blades is too close to the excitation frequency of the fan, resonance may occur, leading to vibration problems throughout the machine. By adjusting the design of the fan blades to change their natural frequency, the two can be offset, resonance can be avoided, and the risk of overall machine vibration can be reduced.

[0038] This application provides a fan blade, in which both the suction surface 1 and the pressure surface 2 of the fan blade have smooth, recessed flow channels 3. The flow channels 3 are oriented along the curved direction connecting the leading edge 4 and the trailing edge 5 of the fan blade, and multiple flow channels 3 distributed radially along the fan blade form a wave-shaped structure. This structure optimizes the flow path of airflow through the fan blade, reduces turbulence and resistance, and makes the airflow smoother and more stable, thereby effectively reducing the noise generated by airflow turbulence during fan operation.

[0039] In one alternative implementation, the flow channel 3 is recessed from the leading edge 4 of the fan blade, transitioning smoothly in the middle portion of the fan blade until there is no recess.

[0040] The flow channel 3 of the fan blade is concave starting from the leading edge 4, gradually transitioning to a smooth surface in the middle section until it disappears. This concavity from the leading edge 4 guides the airflow entering the fan blade more smoothly, effectively reducing separation and vortex formation caused by sudden changes in airflow direction. This not only helps reduce noise caused by turbulence but also improves the fan's efficiency. Furthermore, as the airflow moves towards the middle of the fan blade, the flow channel 3 gradually becomes smoother until it disappears completely. This transition ensures that the airflow remains relatively stable as it passes over the fan blade, reducing energy loss.

[0041] This unique flow channel 3 design has several positive impacts on improving fan blade performance. First, the recessed design starting from the leading edge 4 allows the airflow entering the fan blade to better conform to the expected flow path, thus avoiding unnecessary energy loss. Second, the smooth transition from the middle section of the fan blade to the unrecessed section allows the airflow to continue flowing along the fan blade surface with minimal resistance, further reducing the possibility of turbulence.

[0042] In one alternative implementation, the flow channel 3 is concave from the leading edge 4 of the fan blade, transitions smoothly to no concavity in the middle part of the fan blade, and then concaves again from the middle part of the fan blade to the trailing edge 5 of the fan blade.

[0043] The fan blade design incorporates a flow channel 3 structure. This structure begins with a concave shape at the leading edge 4, gradually transitioning to a flatter shape in the middle section of the blade until the concavity disappears. It then concaves again from the middle section to the trailing edge 5. This design optimizes airflow behavior as it passes through the fan blade, thereby improving overall aerodynamic performance. The initial concavity at the leading edge 4 helps guide airflow more smoothly into the fan blade area, reducing airflow separation and vortex formation, thus lowering noise and improving fan efficiency. As the airflow continues to move backward, the flow channel 3 gradually flattens out, which helps maintain airflow stability and avoids unnecessary turbulence and energy loss.

[0044] However, the secondary indentation occurs when the airflow approaches the middle of the fan blade, at which point the flow channel 3 begins to indent again, continuing all the way to the trailing edge 5. This design takes into account the changes the airflow may experience as it passes through the fan blade. The initial indentation provides good inlet conditions for the airflow, while the smooth transition in the middle ensures stable airflow. But as the airflow moves towards the trailing edge 5, the airflow velocity increases and the pressure decreases, which may lead to new flow problems, such as reattachment points or reformed turbulence. By introducing the indentation again after the middle of the fan blade, a more uniform and efficient flow of airflow across the entire fan blade surface can be ensured. This not only improves the overall efficiency of the fan but also further reduces operating noise and enhances the user experience.

[0045] Furthermore, this double-recessed design with a gentle transition in the middle also has a positive impact on the mechanical strength of the fan blades. Because airflow is guided more effectively, the occurrence of localized high-stress areas is reduced. At the same time, this design also helps to improve the natural frequency distribution of the fan blades, offsetting them from the operating frequency of the fan, thereby reducing the risk of resonance, lowering overall machine vibration, and extending the service life of the equipment.

[0046] In one possible implementation, the flow channel 3 is recessed from the middle part of the fan blade and extends to the trailing edge 5 of the fan blade.

[0047] The flow channel 3 structure of the fan blade is concave from the middle part of the blade and extends to the trailing edge 5. Specifically, this design does not guide the airflow entering the fan blade from the beginning, but rather, after the airflow has initially contacted the fan blade surface and formed a certain flow pattern, the concavity in the middle part further adjusts and optimizes the direction of the airflow. The purpose of this is to ensure that the airflow remains as smooth as possible throughout its passage through the fan blade, reducing unnecessary turbulence and energy loss.

[0048] The concavity starting from the middle of the fan blade and extending to the trailing edge 5 is designed to further improve the aerodynamic performance of the blade. Since the airflow has already established certain flow characteristics as it passes through the front half of the blade, introducing a concavity in the middle better accommodates these characteristics, thus guiding the airflow to transition more smoothly to the trailing edge 5. This not only helps reduce airflow separation and vortex formation, thereby reducing operating noise, but also significantly improves the fan's efficiency. Furthermore, this design helps improve the distribution of airflow on the blade surface, resulting in a more uniform stress distribution, reducing the occurrence of localized high-stress areas, and ultimately improving the overall strength and durability of the fan blade.

[0049] Under different operating conditions, such as varying speeds or loads, the interaction between airflow and the fan blade surface changes. The design, which begins with a concave indentation in the middle and extends to the trailing edge 5, ensures that the fan blades maintain good performance under various conditions. For example, at high speeds, this design helps effectively disperse airflow pressure, preventing efficiency loss or additional noise caused by excessive local pressure. At low speeds, it ensures sufficient airflow to maintain necessary ventilation.

[0050] The concave design, extending from the middle to the trailing edge 5, also positively impacts the overall stability of the fan system. By optimizing the airflow path, not only can the performance of individual fan blades be improved, but the harmonious flow of air within the entire fan system can also be promoted, reducing vibration and noise levels within the system.

[0051] In one possible implementation, the flow channel 3 is recessed from the leading edge 4 of the fan blade and extends to the trailing edge 5 of the fan blade.

[0052] The flow channel 3 of the fan blade is concave from the leading edge 4 and extends along the entire length of the blade from the leading edge 4 to the trailing edge 5, forming a continuous concave path. This unique design provides an optimized flow path for the airflow, allowing it to pass more smoothly over the surface of the blade as it rotates. This design, with the entire length concave from the leading edge 4 to the trailing edge 5, takes into account the behavior of the airflow across the entire blade surface, ensuring that the airflow can flow efficiently along a predetermined path from the moment it enters the blade.

[0053] The concave flow channel 3, starting from the leading edge 4 of the fan blade and extending to the trailing edge 5, is designed to optimize the aerodynamic performance of the fan blade, thereby improving the overall efficiency of the fan and reducing operating noise. The concave flow channel 3 design allows the airflow to flow more closely to the surface of the fan blade, which not only helps to reduce airflow separation but also effectively suppresses the formation of eddies, thereby reducing energy loss and noise levels.

[0054] The continuous concave design from the leading edge 4 to the trailing edge 5 also plays a positive role in enhancing the mechanical strength and durability of the fan blades. In traditional designs, airflow passing over the fan blades can lead to localized stress concentrations, especially near the airflow separation point, which can easily cause vibration and fatigue damage. By optimizing the airflow distribution and making it more evenly distributed on the fan blade surface, these uneven stresses and vibrations can be effectively reduced, thereby extending the service life of the fan blades. At the same time, this design also helps to disperse the pressure of the airflow on the fan blade surface, avoiding material deformation or damage caused by localized high pressure, and improving the fan blades' ability to resist changes in the external environment.

[0055] The continuous concave design from the leading edge 4 to the trailing edge 5 ensures effective airflow management and control, regardless of whether the operation is at high or low speeds. For example, at high speeds, it effectively reduces turbulence and noise, while at low speeds, it ensures sufficient ventilation to meet different heat dissipation requirements.

[0056] In one possible implementation, the flow channel 3 gradually narrows from the edge of the fan blade toward the center.

[0057] The flow channel 3 structure of the fan blade begins at the edge of the blade and gradually decreases in width as it extends towards the center. This design not only alters the path of airflow on the fan blade surface but also affects airflow distribution and velocity. Specifically, when airflow enters from the outer edge of the fan blade, it first encounters a wider inlet, which facilitates smooth entry into the fan blade and rapid diffusion.

[0058] The flow channel 3, which gradually narrows from the edge to the center, optimizes the aerodynamic performance of the fan blades. By adjusting the width of the flow channel 3, the speed and direction of the airflow can be effectively controlled, allowing the airflow to better conform to the fan blade surface and reducing turbulence and vortex generation. This not only helps improve fan efficiency but also reduces operating noise. Furthermore, because the airflow speed increases and the pressure decreases when passing through the narrow section, this further enhances the airflow's penetration, ensuring more effective gas exchange or cooling.

[0059] In addition to improving aerodynamic performance, the gradually narrowing flow channel design also enhances the mechanical strength of the fan blades. By employing a gradually narrowing design, airflow can be distributed more evenly across the fan blade surface, thereby reducing the occurrence of uneven stress. Simultaneously, this design also helps to disperse the pressure of the airflow on the fan blade surface, preventing material deformation or damage caused by localized high pressure, and improving the fan blades' ability to resist changes in the external environment.

[0060] Furthermore, the interaction between airflow and the fan blade surface varies under different operating conditions. For example, at high speeds, the gradually narrowing flow channel 3 helps to effectively manage airflow and reduce turbulence and noise; while at low speeds, it ensures sufficient ventilation and maintains the necessary heat dissipation.

[0061] In one possible implementation, the flow channel 3 is oriented along the circumference of the fan blade.

[0062] The airflow channels 3 of the fan blades are arranged circumferentially around the fan blades. Circumferentially refers to the direction around the axis of rotation of the fan blades. This design allows the airflow to flow in a more natural direction as it passes through the fan blades, rather than being forced to change direction or undergoing abrupt changes.

[0063] First, the circumferentially arranged flow channels 3 help reduce airflow turbulence and vortices. The circumferential flow channels 3 allow the airflow to adhere more closely to the fan blade surface, maintaining a more stable flow state. This not only reduces noise levels but also improves fan efficiency because energy loss is reduced. Furthermore, because the airflow flows circumferentially, it better utilizes centrifugal force, further enhancing the airflow's penetration and coverage.

[0064] Secondly, this design ensures a more uniform airflow distribution across the fan blade surface. By employing the circumferential flow channel design, a balanced airflow distribution across the entire fan blade surface can be achieved. This uniform airflow distribution not only improves the overall performance of the fan but also helps extend the lifespan of the fan blades because it reduces the occurrence of localized high-stress areas and lowers the risk of fatigue damage.

[0065] In addition, the circumferential flow channel 3 design also has certain mechanical advantages. Because the airflow can pass through the fan blades more smoothly, vibrations caused by turbulence are reduced, which directly enhances the stability and reliability of fan operation.

[0066] Overall, the flow channel 3 design arranged circumferentially along the fan blades not only brings higher efficiency and lower noise levels to the fan, but also enhances the reliability and durability of the equipment, providing users with a better user experience.

[0067] In one possible implementation, the wave structure is a periodically repeating wave shape.

[0068] Periodic repeating wave shapes are not a single wave line or a simple wave surface. Each wave unit follows the same geometric rules, including the wave undulation, the position of the crest and trough, and the wave width and height, which remain highly consistent.

[0069] Because the wave units support each other, they form a strong and stable structure. When external forces are applied to this structure, the forces can be evenly distributed among the wave units, reducing local stress concentration and thus effectively preventing structural damage.

[0070] Furthermore, this periodically repeating wave-like structure enhances structural strength while also offering a degree of flexibility. The wave shape allows it to better withstand various external loads. For example, in wind turbine blade applications, the wave-like structure effectively disperses the pressure of airflow on the blade surface, reducing the risk of deformation caused by localized high pressure. Simultaneously, this structure improves aerodynamic performance by guiding airflow more smoothly across the blade surface, reducing turbulence and noise, and enhancing the overall efficiency of the wind turbine.

[0071] In one possible implementation, the periodically repeating wave shape is a sine curve shape or a near-sine curve shape.

[0072] First, the periodic wave structure, employing a sinusoidal or near-sinusoidal shape, leverages the smooth transition characteristic of a sine curve. That is, the transition from crest to trough is gradual and continuous, avoiding abrupt angle changes and thus reducing energy loss and turbulence formation during airflow or water flow. This structure guides airflow more smoothly across the fan blade surface, reducing efficiency loss due to airflow separation and lowering operating noise.

[0073] Secondly, the periodic repetition of the sinusoidal shape provides the structure with greater stability and strength. Because the geometric parameters (such as wavelength and amplitude) remain consistent across each wave element, the entire structure can distribute stress evenly under external loads, reducing the occurrence of localized high-stress points and effectively preventing structural damage. Especially when facing dynamic loads, such as wind impacts, the flexible nature of the sinusoidal shape allows the structure to deform appropriately to absorb energy, rather than directly resisting external forces, thus greatly improving the structure's safety and durability.

[0074] This application also provides a fan, including the fan blades provided above.

[0075] The fan employs an innovative blade design, with smoothly recessed flow channels 3 on both the suction surface 1 and the pressure surface 2. These flow channels 3 extend along the curved direction connecting the leading edge 4 and the trailing edge 5 of the blade, forming a wave-like structure radially distributed along the blade. Specifically, these flow channels 3 can be recessed starting from the leading edge 4 and gradually transitioning to a non-recessed state in the middle section, or they can be recessed again in the middle section and continue to the trailing edge 5. Alternatively, some designs allow the recess to begin in the middle of the blade and continue to the trailing edge 5, or the recess to begin at the leading edge 4 and extend to the trailing edge 5.

[0076] To further optimize the airflow path, some designs feature flow channel 3 that gradually narrows from the edge of the fan blade towards the center. This helps guide airflow more smoothly across the fan blade surface, reducing turbulence and energy loss. Other designs align flow channel 3 along the circumference of the fan blade, ensuring uniform airflow distribution across the entire blade surface, reducing noise and improving fan efficiency. Specifically, the wave-like structure is designed with a periodically repeating wave shape, which can be a sine curve or an approximate sine curve to achieve optimal aerodynamic performance.

[0077] This new fan design not only improves the performance of individual blades but also significantly enhances the efficiency of the entire fan system. Fans with this design excel in a variety of applications, from data center environments requiring efficient cooling to home appliances prioritizing quiet operation. For example, in data center cooling systems, the fan manages heat more effectively, maintaining optimal server operating temperatures while reducing energy consumption and noise levels. In the home appliance sector, this fan provides a quieter operating experience, meeting users' needs for a comfortable living environment.

[0078] The technical solution of this utility model has been described in conjunction with the specific embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the protection scope of this utility model is obviously not limited to these specific embodiments. Without departing from the principle of this utility model, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the protection scope of this utility model.

Claims

1. A fan blade, characterized in that, Both suction and pressure sides of the vane have smooth concave flow channels, the flow channels are oriented along a curve connecting a leading edge and a trailing edge of the vane, and a plurality of the flow channels distributed along a radial direction of the vane form a wave structure.

2. The leaf according to claim 1, characterized in that The flow channels are concave from the leading edge of the vane, and transition smoothly to no concave at a middle portion of the vane.

3. The leaf according to claim 1, wherein The flow channels are concave from the leading edge of the vane, transition smoothly to no concave at a middle portion of the vane, and again concave from the middle portion and continue to the trailing edge of the vane.

4. The leaf according to claim 1, wherein The flow channels are concave from a middle portion of the vane and continue to the trailing edge of the vane.

5. The leaf according to claim 1, wherein The flow channels are concave from the leading edge of the vane and continue to the trailing edge of the vane.

6. A leaf according to any one of claims 2-4, characterised in that The flow channels taper from the edge to the middle of the vane.

7. A leaf according to any one of claims 1-5, characterised in that The flow channels are oriented along a circumferential direction of the vane.

8. A leaf according to any one of claims 1-5, characterised in that The wave structure is a periodically repeating wave shape.

9. The leaf according to claim 8, characterized in that The periodically repeating wave shape is a sinusoidal shape or a near sinusoidal shape.

10. A fan, characterized by A plurality of vanes as claimed in any one of claims 1-9.

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