Bionic fan blade, axial flow fan and rail vehicle

Abstract

The invention discloses a bionic fan blade, an axial flow fan and a rail vehicle, and relates to the technical field of fan blades, the bionic fan blade is used for being arranged on a hub of the axial flow fan, and the bionic fan blade comprises a blade body, a flange and a surface structure with a pit. Wherein the blade body is provided with a blade pressure surface and a blade suction surface; the turnup is arranged at the top of the blade body, extends from the blade pressure surface to the blade suction surface and is turned to one side of the blade suction surface; the surface structure is arranged on the outer side of the turnup, and the pits in the surface structure are non-uniformly distributed in the spanwise direction and the chordwise direction of the blade body. According to the bionic fan blade, the problem that the aerodynamic noise cannot be obviously reduced on the premise that the current axial flow fan blade meets the performance indexes such as air volume and pressure rise is solved.

Description

Technical Field

[0001] The present application relates to the technical field of fan blades, and in particular to a bionic fan blade, an axial flow fan and a rail vehicle. Background Art

[0002] In the field of rail vehicle ventilation and air conditioning technology, fans, as key fluid machinery, are widely used in air conditioning and ventilation systems, as well as in the forced cooling systems of equipment compartments. Specifically, axial fans are commonly used in the condensing heat dissipation process of air conditioning units, leveraging their high air volume and low pressure rise to achieve efficient heat removal from the off-board heat exchanger. Centrifugal fans are often used in the passenger compartment air ducts to meet the "higher pressure rise and lower air volume" requirements.

[0003] However, with increasing rail vehicle speeds and increasingly stringent external noise limits, the aerodynamic noise problem of axial fans has become increasingly prominent. Research has shown that axial fan noise has become one of the main contributors to the vehicle's external noise level. Its noise energy is primarily concentrated in the low- and medium-frequency broadband noise generated by tip leakage vortices, trailing edge vortex shedding, and their mutual interference. Although existing technologies have achieved some noise suppression through methods such as adjusting blade sweep, increasing tip clearance, or attaching simple shields, these measures are often accompanied by drawbacks such as reduced air volume, insufficient pressure rise, or limited structural space, making it difficult to achieve an effective balance between "maintaining performance" and "reducing noise."

[0004] Therefore, the current axial fan blades are still unable to achieve a significant reduction in aerodynamic noise while simultaneously meeting performance indicators such as air volume and pressure rise, becoming a technical bottleneck restricting further noise reduction and energy saving of rail vehicles. Summary of the Invention

[0005] The purpose of this application is to provide a bionic fan blade and a rail vehicle, which solves the problem that current axial flow fan blades cannot achieve a significant reduction in aerodynamic noise while meeting performance indicators such as air volume and pressure rise.

[0006] To achieve the above objectives, the present application provides a bionic fan blade for being arranged on the hub of an axial flow fan, the bionic fan blade comprising:

[0007] a blade body, the blade body having a blade pressure surface and a blade suction surface;

[0008] A flange, the flange being provided at the top of the blade body, the flange extending from the blade pressure surface toward the blade suction surface and being turned toward one side of the blade suction surface;

[0009] A surface structure with pits is provided on the outer side of the flange, and the pits on the surface structure are unevenly distributed along the span direction and the chord direction of the blade body.

[0010] In some embodiments, the trailing edge of the blade body is provided with tail fin-shaped serration units spaced apart along the span direction of the blade body.

[0011] In some embodiments, each of the tail fin-shaped sawtooth units is inclined in a direction away from the flange, each of the tail fin-shaped sawtooth units has a beveled side and an arcuate side, and the distance between any two adjacent tail fin-shaped sawtooth units ranges from 8 to 12 mm.

[0012] In some embodiments, the bionic fan blade further includes a plurality of ridges provided on the suction surface of the blade, each ridge is provided in one-to-one correspondence with each tail fin-shaped serrated unit, and each ridge extends along the chord direction of the blade body.

[0013] In some embodiments, the outer edge profile of the flange is configured to adopt a bionic curve of the outer edge profile of a butterfly wing.

[0014] In some embodiments, the pit is spherical, and the diameter of the pit ranges from 2 to 3.6 mm, wherein the diameter of the pit in the middle area of ​​the blade body is smaller than the diameter of the pit in the areas on both sides of the blade body.

[0015] In some embodiments, the distribution density of the pits is proportional to the area and local surface curvature of the flange.

[0016] In some embodiments, at least a portion of the interior of the recess is filled with a compressible microporous material layer, and the microporous material layer is configured to change the volume of the recess by passive suction / exhaust to adjust the tip leakage intensity.

[0017] The present application also provides an axial flow fan, comprising a hub, and also comprising bionic fan blades as described in any one of the above items, which are evenly distributed along the circumferential direction of the hub, and the number of the bionic fan blades is 6.

[0018] The present application also provides a rail vehicle, comprising the above-mentioned axial flow fan.

[0019] In contrast to the aforementioned background technology, the bionic fan blade provided in the embodiments of the present application is intended for installation on the hub of an axial flow fan. The bionic fan blade comprises a blade body, a flange, and a surface structure with pits. The blade body comprises a pressure side and a suction side; the flange is disposed at the top of the blade body, extending from the pressure side toward the suction side and tilted toward one side of the suction side; the surface structure is disposed on the outer side of the flange, with the pits on the surface structure being unevenly distributed along the spanwise and chordwise directions of the blade body.

[0020] To overcome the bottleneck of the prior art, namely, "the inability to effectively reduce aerodynamic noise while maintaining air volume and pressure rise," the embodiments of the present application introduce a coupled bionic structure of "a non-smooth surface structure of flange + non-uniform pits" on the axial flow fan blade, which produces at least the following beneficial effects:

[0021] Since the flow at the tip of the fan blade has a significant impact on aerodynamic noise (the tip leakage vortex is the main source of medium and low-frequency broadband noise outside the vehicle), for this reason, the present application sets a flange at the blade tip, and extends it from the pressure surface of the blade toward the suction surface of the blade and turns to one side of the suction surface of the blade. This blade tip flange design is conducive to guiding the airflow in the gap from the pressure surface of the blade to the suction surface, thereby effectively restricting the direction of the leakage flow, shortening the roll-up distance of the leakage vortex, and thus reducing the aerodynamic noise of the tip leakage flow. At the same time, the non-smooth surface structure on the outside of the flange can improve the flow state of the airflow in the blade tip gap, and the non-uniform pits will cause the airflow to form turbulence at the blade and induce micro-turbulent pulsations locally, so that the airflow is closely attached to the blade surface, reducing airflow separation, and further reducing the aerodynamic noise of the tip leakage flow. In addition, by arranging the flange and the pit at the top of the blade, there is no need to install additional protective covers or silencer accessories, and the space utilization rate is high. It is particularly suitable for application scenarios with limited space in rail vehicle air-conditioning units and equipment compartments. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the following briefly introduces the drawings required for use in the embodiments or related technical descriptions. Obviously, the drawings described below are merely embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without any creative work.

[0023] Figure 1 The structure of the bionic fan blade in the embodiment of this application is shown in FIG. Figure 1 .

[0024] Figure 2 The structure of the bionic fan blade in the embodiment of this application is shown in FIG. Figure 2 .

[0025] Figure 3 The structure of the bionic fan blade in the embodiment of this application is shown in FIG. Figure 3 .

[0026] Figure 4 The structure of the bionic fan blade in the embodiment of this application is shown in FIG. Figure 4 .

[0027] Figure 5 for Figure 1 Enlarged schematic diagram of area A in the middle.

[0028] Figure 6 for Figure 4 Schematic diagram of the enlarged portion B.

[0029] Figure 7 This is a front view of the assembly of the hub and bionic fan blades of the axial flow fan in the embodiment of the present application.

[0030] Figure 8 This is a side view of the assembly of the hub and bionic fan blades of the axial flow fan in an embodiment of the present application.

[0031] Figure 9 This is a back view of the assembly of the hub and bionic fan blades of the axial flow fan in an embodiment of the present application.

[0032] in:

[0033] 10-Bionic fan blades;

[0034] 11-blade body, 111-blade pressure surface, 112-blade suction surface;

[0035] 12-Flanging;

[0036] 13- Surface structure;

[0037] 14- pit;

[0038] 15-tail fin-shaped sawtooth unit, 151-bevel edge, 152-arc edge;

[0039] 20-wheel hub. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0041] In order to enable those skilled in the art to better understand the present application, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0042] See also Figures 1 to 4 The bionic fan blade 10 provided in the embodiment of the present application is used to be set on the hub 20 of the axial flow fan. The bionic fan blade 10 includes a blade body 11, a flange 12 and a surface structure 13 with a pit 14.

[0043] The blade body 11 has a blade pressure surface 111 and a blade suction surface 112 .

[0044] It should be noted that the so-called blade pressure surface 111 refers to the side of the blade that directly faces the incoming airflow during rotation and is subjected to higher static pressure. The airflow on this side is compressed by the work performed by the blade, hence the term "pressure surface." In the geometric description of the blade cross section, it generally corresponds to the "lower surface" or "concave surface" of the blade (airfoil). The so-called blade suction surface 112 refers to the surface opposite the blade pressure surface 111. The airflow on this side is accelerated and the static pressure is reduced due to the flow around the blade, creating a "suction" effect, hence the term "suction surface." In blade geometry, it generally corresponds to the "upper surface" or "convex surface."

[0045] The flange 12 is provided at the top of the blade body 11 . The flange 12 extends from the blade pressure surface 111 toward the blade suction surface 112 and is turned toward one side of the blade suction surface 112 .

[0046] Since there is a 5mm gap between the top of the bionic fan blade 10 and the air guide ring, the flow at the top of the bionic fan blade 10 has an important impact on the aerodynamic noise. The blade top flange design is adopted to help guide the airflow in the gap between the top of the bionic fan blade 10 and the air guide ring from the blade pressure surface 111 to the blade suction surface 112.

[0047] Please also refer to Figure 5 The surface structure 13 is a non-smooth surface structure. The surface structure 13 is arranged on the outer side of the flange 12 . The pits 14 on the surface structure 13 are unevenly distributed along the span direction and the chord direction of the blade body 11 .

[0048] It should be noted that the span-wise direction of the blade body 11 refers to the direction extending from the root of the blade body 11 (the end closest to the hub 20) to the tip (the end away from the hub 20), that is, along the length (span) of the blade body 11, which can be simply understood as the direction along the "length" of the blade body 11. The chord-wise direction of the blade body 11 refers to the direction extending from the leading edge (the end first contacted by the airflow) to the trailing edge (also known as the trailing edge) of the blade body 11, that is, along the blade chord line, which can be simply understood as the direction along the "width" of the blade body 11.

[0049] In order to overcome the bottleneck pointed out in the prior art that "aerodynamic noise cannot be effectively reduced while maintaining air volume and pressure rise", the embodiment of the present application introduces a coupled bionic structure of "a non-smooth surface structure 13 of a flange 12 + non-uniform pits 14" on the axial flow fan blade.

[0050] Since the flow at the tip of the fan blade has a significant impact on the aerodynamic noise (the blade tip leakage vortex is the main source of medium and low-frequency broadband noise outside the vehicle), the present application provides a flange 12 at the blade tip, and extends it from the blade pressure surface 111 toward the blade suction surface 112 and flips to one side of the blade suction surface 112. This blade tip flange 12 design is conducive to guiding the airflow in the gap from the blade pressure surface 111 to the suction surface, thereby effectively restricting the direction of the leakage flow, shortening the rolling distance of the leakage vortex, and thus reducing the aerodynamic noise of the blade tip leakage flow.

[0051] At the same time, the non-smooth surface structure 13 on the outside of the flange 12 can improve the flow state of the airflow in the blade tip gap. The non-uniform pits 14 will cause the airflow to form turbulence at the blade and induce micro-turbulent pulsations locally, so that the airflow fits closely to the blade surface, reducing airflow separation and further reducing the aerodynamic noise of the blade tip leakage.

[0052] The use of the non-uniform dimple 14 design can dissipate the energy of the leakage vortex in advance, reducing the vortex intensity of the blade tip leakage vortex by 10%-25%, thereby reducing the noise outside the vehicle by 3-5dB while ensuring that the air volume is not reduced. Moreover, the dimple 14 can also reduce the wall friction resistance under non-stall conditions and offset the additional resistance brought by the flange 12. Numerical calculations show that at the same speed, the pressure rise of the blade of the present application drops by less than 1%, and the air volume remains basically unchanged, thus solving the defect of "it is difficult to achieve both performance and noise" in current fan blades.

[0053] In addition, the flange 12 and the pit 14 are arranged at the top of the blade, and there is no need to install additional shields or silencer accessories, which has high space utilization and is particularly suitable for application scenarios where space is limited in rail vehicle air-conditioning units and equipment cabins.

[0054] Of course, according to actual needs, the present application forms the flange 12 and the pit 14 integrally at the top of the blade, and the pit 14 can be directly formed by additive manufacturing or precision casting to reduce processing costs.

[0055] Please also refer to Figure 6 The trailing edge of the blade body 11 is provided with tail fin-shaped sawtooth units 15 arranged at intervals along the span direction of the blade body 11.

[0056] In some embodiments, each tail fin-shaped sawtooth unit 15 is inclined in a direction away from the flange 12 , each tail fin-shaped sawtooth unit 15 has a beveled edge 151 and an arcuate edge 152 , and the distance between any two adjacent tail fin-shaped sawtooth units 15 is in the range of 8-12 mm.

[0057] Each tail fin-shaped serrated unit 15 forms a noise reduction structure at the trailing edge of the blade, and the noise reduction structure is designed based on the bionic design of the fish tail fin. The downward inclination angle of each tail fin-shaped serrated unit 15 can be about 30°, the length of the hypotenuse 151 of the tail fin-shaped serrated unit 15 is about 8 mm, the length of the arcuate edge 152 is about 15 mm, and the spacing between two adjacent tail fin-shaped serrated units 15 can be 10 mm.

[0058] By adopting the above-mentioned setting method, the noise reduction structure imitating the tail fin structure can make the airflow shedding at the trailing edge of the blade more uniform, thereby reducing the amplitude of the pressure fluctuation at the trailing edge of the blade, moving the airflow separation point backward, reducing the turbulence intensity of the shedding airflow, and further reducing the aerodynamic noise.

[0059] It should be noted that each tail fin-shaped sawtooth unit 15 forms a spanwise segmented cut at the trailing edge, which "chop[es]" the originally shed trailing edge vortex into several smaller vortices. The bionic curve of a fish's tail fin (hypotenuse + arc edge) smoothes the spanwise gradient of the trailing edge pressure pulsation. The 30° downward tilt angle provides a vortex shedding effect while avoiding excessive increase in trailing edge thickness. Experimental results show that with a parameter combination of a 30° downward tilt angle, an 8mm length of the hypotenuse 151, a 15mm length of the arc edge 152, and a 10mm spacing between adjacent tail fin-shaped sawtooth units 15, the peak of the main frequency of blade trailing edge vortex shedding is reduced by 3-6dB, the noise spectrum transforms from discrete peaks to a broadband continuous spectrum, and the overall sound pressure level is significantly reduced.

[0060] In addition, the tail fin-shaped serrated unit 15 can be cast together with the blade body 11 or completed through laser cutting / additive manufacturing post-processing, without the need for additional parts. It is particularly suitable for scenarios where space is limited in rail vehicle air-conditioning units and equipment compartments, and has good engineering feasibility.

[0061] In some embodiments, the bionic fan blade 10 further includes a plurality of ridges provided on the blade suction surface 112 , each ridge being provided in one-to-one correspondence with each tail fin-shaped sawtooth unit 15 , and each ridge extending along the chord direction of the blade body 11 .

[0062] It can be seen that the ridges extend along the chordwise direction on the suction surface 112 of the blade, forming a leading-to-trailing-edge vortex management channel with the tail fin-shaped sawtooth unit 15. The secondary flow vortices induced by the ridges and the small-scale trailing-edge vortices after the sawtooth cutting cancel each other out in phase, further reducing the far-field sound pressure level peak (generally by 2-3dB). At the same time, the spanwise constraint of the boundary layer on the suction surface 112 of the blade by the ridges reduces the amplitude of turbulent pulsation at the trailing edge, further attenuating the discrete noise outside the vehicle. In addition, the chordwise ridges act as local micro-winglets, suppressing the spanwise secondary flow on the suction surface 112 of the blade. At the same speed, the lift coefficient of the blade is increased, while the pressure rise remains basically unchanged, achieving the application effect of reducing noise without reducing efficiency.

[0063] The ridges and each tail fin-shaped sawtooth unit 15 can be completed in one step during casting or additive manufacturing without any additional assembly process.

[0064] In some embodiments, the outer edge profile of the flange 12 is configured to adopt a bionic curve of the outer edge profile of a butterfly wing.

[0065] In other words, the curvilinear design of flange 12 is biomimetic, inspired by the outer edge profile of a butterfly wing. The butterfly's outer edge profile has a non-uniform curvature distribution, with a "slow in front and sharp in the back" pattern. This provides a large local convergence angle at the leading edge of flange 12, suppressing the initial momentum of the leakage jet. Meanwhile, the curvature is rapidly released at the trailing edge, forming a counter-vortex pair that phase-destroys the main vortex of the leakage vortex, thereby reducing the aerodynamic noise of the tip leakage flow. Compared to traditional straight or circular flanges, the butterfly's outer edge profile produces a smaller local adverse pressure gradient in the large curvature area, reducing the risk of boundary layer separation on the flange surface and lowering the added drag coefficient, thereby achieving noise reduction and efficiency improvement without sacrificing air volume and pressure rise.

[0066] In some embodiments, the pit 14 is spherical, and the diameter of the pit 14 ranges from 2 to 3.6 mm, wherein the diameter of the pit 14 in the middle area of ​​the blade body 11 is smaller than the diameter of the pit 14 in the two side areas of the blade body 11 .

[0067] It's important to note that the noise-reducing dimples 14 at the blade tips are a non-smooth surface designed to mimic the surface of a beetle. These dimples 14 are spherical with a diameter ranging from 2mm to 3.6mm. The diameter of the dimples 14 in the center of the blade is smaller, while the diameters of the dimples 14 on the sides are larger. This non-smooth surface, created by the dimples 14, improves the flow of air through the tip clearance. The dimples 14 create turbulence at the blade, ensuring a close fit between the airflow and the blade surface, minimizing separation and further reducing the aerodynamic noise of tip leakage.

[0068] In some embodiments, the pits 14 may be distributed non-uniformly according to the area and surface curvature of the blade tip flange 12 . For example, the distribution density of the pits 14 is proportional to the area and local surface curvature of the flange 12 .

[0069] By simultaneously increasing the density of dimples 14, more dimples can be concentrated in high-curvature, large-area areas, forming a dense network of micro-turbulence dissipators. This further reduces turbulent kinetic energy and noise in these areas. Furthermore, since stress concentration is more pronounced in flanged areas with greater curvature, increasing the density of dimples 14 proportionally to this curvature can even out local wall thickness reduction, avoid local stress peaks, and improve fatigue life, thus meeting the high-reliability operation requirements of rail vehicles.

[0070] In some embodiments, at least a portion of the interior of the dimple 14 is filled with a compressible microporous material layer, which is configured to change the volume of the dimple 14 by passive suction / exhaust to adjust the tip leakage intensity.

[0071] The flow resistivity σ of the microporous material layer can be set at to When the tip clearance changes with the operating conditions, the microporous material layer changes the volume of the pit 14 through passive suction / exhaust, thereby adaptively adjusting the tip leakage flow intensity.

[0072] Specifically, the microporous material layer features a compressible, resilient porous structure that passively absorbs and exhausts air during turbine operation. When the tip clearance decreases transiently due to wheel-rail vibration or thermal expansion and contraction, the microporous layer is compressed and exhausts air, shrinking the effective volume of the pit 14 and the cross-sectional area of ​​the leakage flow path. Conversely, when the clearance increases, the microporous layer rebounds and absorbs air, expanding the pit volume and automatically compensating for the leakage path. This passive regulation further reduces the fluctuation amplitude of the tip leakage vortex, thereby further reducing noise.

[0073] It is important to note that the material of the microporous material layer should take into account requirements such as compressibility and resilience, fatigue resistance, temperature resistance, and process feasibility. For example, open-cell foam metals (open-cell foam aluminum, nickel foam, or copper foam), polymer microporous elastomers (polyurethane microporous elastomer, silicone rubber microporous mat, etc.), or fiber-matrix composite microporous felt (glass fiber needle-punched felt impregnated with fluororubber / epoxy microporous resin) can be used.

[0074] Furthermore, the non-smooth surface (dimples 14) and the flange 12 spatially form a coupled noise reduction zone: the distance L from the center of each dimple 14 to the suction-side edge of the flange 12 satisfies 0.5d ≤ L ≤ 2d, where d is the diameter of the dimple 14. This coupled noise reduction zone serves to suppress the roll-up intensity of the tip leakage vortex. Within this coupled noise reduction zone, the suction-side surface of the flange 12 is further provided with an annular micro-rib concentric with the dimple 14. The ratio of the micro-rib's height h to the dimple 14's depth δ is 0.3 ≤ h / δ ≤ 0.7, forming a localized secondary flow barrier that further weakens the leakage flow.

[0075] The non-smooth surface structure 13, flange 12, and tail fin-shaped serrations 15 are formed as a single-piece metal or composite component through additive manufacturing. Laser selective melting parameters are controlled during the additive manufacturing process to form a hardened layer with a thickness of 0.05mm-0.15mm around the edges of the dimples 14, increasing hardness by 20%-40% compared to the base material. This ensures aerodynamic noise reduction while also increasing the wear life of the blade tip.

[0076] In summary, this application applies a specific bionic structure to the low-noise bionic design of axial flow fan blades. On the basis of ensuring the flow rate, pressure head and other performance of the axial flow fan, the blade top flange 12 is designed based on the bionic design of the edge of a butterfly wing, the surface structure 13 of the blade flange 12 is designed based on the bionic design of the non-smooth surface of a beetle pit, and the blade trailing edge is designed based on the bionic design of a fish tail fin. By improving the airflow in the blade top and trailing edge areas, the aerodynamic noise of the axial flow fan is reduced.

[0077] Please also refer to Figure 7 、 Figure 8 and Figure 9 The present application provides an axial flow fan, including a hub 20, and also includes bionic fan blades 10 evenly distributed along the circumferential direction of the hub 20, as described in the above specific embodiment. The number of bionic fan blades 10 is preferably 6.

[0078] The present application provides a rail vehicle, including the axial flow fan described in the above specific embodiment; other parts of the rail vehicle can refer to relevant technologies and will not be elaborated in this article.

[0079] It should be noted that, in this specification, relational terms such as first and second are merely used to distinguish one entity from other entities, but do not necessarily require or imply any actual relationship or order between these entities.

[0080] The above is a detailed introduction to the bionic fan blades, axial flow fans and rail vehicles provided by the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the scheme of the present application and its core ideas. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the present application.

Claims

1. A bionic fan blade, used to be arranged on the hub of an axial flow fan, characterized in that: The bionic fan blade comprises: a blade body, the blade body having a blade pressure surface and a blade suction surface; A flange, the flange being provided at the top of the blade body, the flange extending from the blade pressure surface toward the blade suction surface and being turned toward one side of the blade suction surface; A surface structure with pits is provided on the outer side of the flange, and the pits on the surface structure are unevenly distributed along the span direction and the chord direction of the blade body.

2. The bionic fan blade according to claim 1, characterized in that: The trailing edge of the blade body is provided with tail fin-shaped sawtooth units arranged at intervals along the span direction of the blade body.

3. The bionic fan blade according to claim 2, characterized in that: Each of the tail fin-shaped sawtooth units is inclined in a direction away from the flange, each of the tail fin-shaped sawtooth units has a beveled side and an arcuate side, and the distance between any two adjacent tail fin-shaped sawtooth units ranges from 8 to 12 mm.

4. The bionic fan blade according to claim 2, characterized in that: The bionic fan blade further includes a plurality of ridges arranged on the suction surface of the blade, each of the ridges is arranged in a one-to-one correspondence with each of the tail fin-shaped sawtooth units, and each of the ridges extends along the chord direction of the blade body.

5. The bionic fan blade according to claim 1, characterized in that: The outer edge profile of the flange is configured as a bionic curve adopting the outer edge profile of a butterfly wing.

6. The bionic fan blade according to claim 1, characterized in that: The pit is spherical, and the diameter of the pit ranges from 2 to 3.6 mm, wherein the diameter of the pit in the middle area of ​​the blade body is smaller than the diameter of the pit in the areas on both sides of the blade body.

7. The bionic fan blade according to claim 1, characterized in that: The distribution density of the pits is proportional to the area of ​​the flange and the curvature of the local surface.

8. The bionic wind turbine blade according to any one of claims 1 to 7, characterized in that: At least a portion of the interior of the recess is filled with a compressible microporous material layer, and the microporous material layer is configured to change the volume of the recess by passive suction / exhaust, so as to adjust the blade tip leakage flow intensity.

9. An axial flow fan, comprising a hub, characterized in that: It also includes bionic fan blades according to any one of claims 1 to 8, which are evenly distributed along the circumferential direction of the hub, and the number of the bionic fan blades is 6.

10. A rail vehicle, characterized in that: Comprising the axial flow fan as claimed in claim 9.

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