Blade structure, axial flow fan blade and axial flow fan

Abstract

The utility model provides a kind of blade structure, axial flow fan blade and axial flow fan, blade structure includes blade body, blade body includes head-tail connection's leading edge, suction surface, trailing edge and pressure surface, pressure surface and suction surface respectively extend between leading edge and trailing edge, in airflow flow direction, leading edge or pressure surface is provided with import hole, trailing edge or suction surface is provided with export hole;Blade body is provided with muffling cavity, import hole and export hole are communicated with muffling cavity respectively, import hole guides airflow to muffling cavity, export hole exports airflow in muffling cavity from blade body.The utility model import hole reduces the impact noise of airflow to leading edge, export hole reduces trailing edge noise by changing airflow flow state at trailing edge.

Description

Technical Field

[0001] This utility model belongs to the field of wind turbine technology, specifically relating to a blade structure, an axial flow fan blade, and an axial flow fan. Background Technology

[0002] With the increasing demand for efficient ventilation, heat dissipation, and air circulation in modern industrial and civil equipment, axial flow fans are widely used as key aerodynamic components. However, traditional axial flow fans exhibit significant operating noise due to aerodynamic noise and mechanical vibration during high-speed, high-flow-rate operation, directly impacting user experience and environmental comfort. Although existing technologies reduce noise through methods such as optimizing blade geometry or using sound-absorbing materials, it is often difficult to achieve significant noise reduction while maintaining aerodynamic performance, especially in high-speed, high-flow-rate applications where the interaction between the blades and the airflow easily generates aerodynamic noise. Utility Model Content

[0003] This invention provides a blade structure, an axial flow fan blade, and an axial flow fan, which can solve the technical problem that it is difficult to achieve significant noise reduction while ensuring aerodynamic performance by optimizing blade geometry or using sound-absorbing materials to reduce noise.

[0004] This utility model provides a blade structure, which includes a blade body;

[0005] The blade body includes a leading edge, a suction surface, a trailing edge, and a pressure surface that are connected end to end. The pressure surface and the suction surface extend between the leading edge and the trailing edge, respectively. In the direction of airflow, the leading edge or the pressure surface is provided with an inlet hole, and the trailing edge or the suction surface is provided with an outlet hole.

[0006] The blade body is provided with a noise-absorbing cavity. The inlet hole and the outlet hole are respectively connected to the noise-absorbing cavity. The inlet hole guides the airflow into the noise-absorbing cavity, and the outlet hole discharges the airflow in the noise-absorbing cavity out of the blade body.

[0007] In some embodiments, the suction surface is provided with the inlet hole, which is close to the leading edge; the pressure surface is provided with the outlet hole, which is close to the trailing edge.

[0008] In some embodiments, the blade body is a double-airfoil structure. With the longitudinal section of the blade body as the projection plane, the blade body has an inner airfoil and an outer airfoil. The inner airfoil is located inside the outer airfoil and forms the silencing cavity. The inlet hole guides the airflow from the outer airfoil to the silencing cavity.

[0009] In some embodiments, the profile of the inner airfoil is formed by proportionally scaling down the profile of the outer airfoil.

[0010] In some embodiments, a serrated structure is also included, wherein the suction surface is provided with the outlet hole, the outlet hole is close to the tail edge, the tail edge is provided with the serrated structure, and the serrated structure is located on the air outlet path of the outlet hole.

[0011] In some embodiments, with the width direction of the blade body as the projection plane, the serrated structure includes a plurality of serrations, the plurality of serrations being arranged along the width direction of the trailing edge, and the tooth width of the serrations being gradually reduced in the direction away from the trailing edge.

[0012] In some embodiments, with the width direction of the blade body as the projection plane, the outlet hole includes multiple sub-channels, each of which is connected to the silencing cavity. The multiple sub-channels are arranged in a one-to-one correspondence with the multiple serrations, so that the air outlet path of the sub-channel is located on the tip axis of the serration.

[0013] In some embodiments, the width direction of the blade body is taken as the projection plane, the maximum width of the serration is w, the length of the serration is L, the airfoil chord length of the blade body is c, the maximum width w ranges from 1.3% to 2.8% of the airfoil chord length c, and the length L ranges from 4.2% to 6.1% of the airfoil chord length c.

[0014] In some embodiments, the serrated structure is integrally formed with the blade body, and with the longitudinal section of the blade body as the projection plane, the extension length of the serrated structure in the airflow direction is 10% of the airfoil chord length of the blade body.

[0015] An axial flow fan blade includes multiple blade structures, wherein the blade structures are as described above.

[0016] An axial flow fan includes an axial flow fan blade, wherein the axial flow fan blade is the aforementioned axial flow fan blade.

[0017] The blade structure, axial flow fan blade, and axial flow fan provided by this utility model have the following beneficial effects:

[0018] In this invention, by providing inlet holes at the leading edge or pressure surface, a portion of the high-speed airflow can be guided into the silencing cavity, thereby reducing the direct impact of the airflow on the leading edge and lowering the noise generated by the airflow impact. Furthermore, the inlet holes can alter the airflow distribution on the blade surface. Because part of the airflow is guided into the silencing cavity, the velocity and pressure distribution of the airflow along the pressure and suction surfaces changes, thus optimizing the airflow state on the blade surface and reducing eddy noise caused by uneven airflow distribution. In addition, the presence of the inlet holes provides an additional flow channel for the airflow, allowing it to be partially diverted before entering the blade surface, thereby reducing the turbulence intensity on the blade surface, enhancing the stability of the airflow, and lowering aerodynamic noise caused by turbulence. The high-speed airflow exiting the outlet holes collides with the airflow at the trailing edge or suction surface, causing the airfoil boundary layer to detach prematurely. This boundary layer detachment alters the airflow state at the trailing edge, reducing the interaction between the boundary layer and the trailing edge, thereby lowering aerodynamic noise at the trailing edge. The synergistic effect of the inlet and outlet holes can reduce the noise generated by airflow on the blade surface from multiple aspects. The inlet hole reduces the impact noise of airflow on the leading edge, while the outlet hole reduces trailing edge noise by changing the airflow state at the trailing edge. The combination of the two enables the entire blade structure to significantly reduce aerodynamic noise when operating at high wind speeds and large flow rates, thereby improving the quietness of equipment operation and environmental comfort.

[0019] In this invention, after the airflow enters the silencing cavity through the inlet hole, the cavity provides a relatively enclosed space. Its main purpose is to reduce the high discrete noise generated by the passing frequency of the blades. Sound waves reflect back and forth between the cavity's inner walls, thereby reducing noise. There are velocity and pressure differences between the suction and pressure surfaces of the blades. This pressure difference is one of the main causes of aerodynamic noise. The silencing cavity can alter the path of the local airflow, allowing some airflow to enter the blade interior through the silencing cavity and then rejoin the main flow through the outlet hole. The silencing cavity, along with the inlet and outlet holes, constitute a complete noise reduction system. The inlet hole introduces airflow into the silencing cavity, which processes the noise in the airflow. The outlet hole redirects the processed airflow to a suitable location (such as the trailing edge or suction surface). This synergistic effect ensures a more orderly flow of air on the blade surface, reducing noise caused by airflow turbulence. Attached Figure Description

[0020] To more clearly illustrate the embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the blade structure according to an embodiment of the present invention;

[0022] Figure 2 This is a schematic diagram of the longitudinal section of the blade structure according to an embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram of the inner airfoil, outer airfoil, and biological airfoil of an embodiment of the present invention;

[0024] Figure 4 This is a schematic diagram of the sawtooth structure according to an embodiment of the present utility model;

[0025] Figure 5 This is a schematic diagram of the saw teeth in an embodiment of the present utility model;

[0026] Figure 6 This is a vector diagram of the airfoil section velocity according to an embodiment of the present invention;

[0027] Figure 7 This is a vector diagram of the velocity of a partial cross-section of the trailing edge in an embodiment of this utility model;

[0028] Figure 8 This is a pressure cloud map distribution according to an embodiment of the present invention;

[0029] Figure 9 This is a velocity cloud map volume distribution diagram of an embodiment of the present invention;

[0030] Figure 10 The inner and outer airfoils of this utility model are fitted and optimized profiles.

[0031] Attached Figures: 1-Leading edge; 2-Suction surface; 3-Tail edge; 4-Pressure surface; 5-Inlet hole; 6-Outlet hole; 601-Sub-channel; 7-Silence cavity; 801-Inner airfoil; 802-Outer airfoil; 9-Serrated structure; 901-Serrated tooth; 10-Blade body; 11-Bio-airfoil. Detailed Implementation

[0032] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present utility model or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model without creative effort are within the scope of protection of the present utility model.

[0033] In the description of this utility model, it should be understood that the directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this utility model. The directional terms "inner" and "outer" refer to the inner and outer contours of each component itself.

[0034] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used here to describe the spatial positional relationship of a device or feature as shown in the figure with other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation in addition to the orientation of the device as described in the figure. For example, if a device in the figure is inverted, a device described as "above" or "on top of" other devices or structures will subsequently be positioned as "below" or "under" other devices or structures.

[0035] See also Figure 1 and Figure 2 As shown, according to an embodiment of the present invention, a blade structure is provided, which includes a blade body 10; the blade body 10 includes a leading edge 1, a suction surface 2, a trailing edge 3, and a pressure surface 4 connected end to end, the pressure surface 4 and the suction surface 2 extending between the leading edge 1 and the trailing edge 3 respectively, and in the airflow direction, the leading edge 1 or the pressure surface 4 is provided with an inlet hole 5, and the trailing edge 3 or the suction surface 2 is provided with an outlet hole 6; a silencing cavity 7 is provided inside the blade body 10, the inlet hole 5 and the outlet hole 6 are respectively connected to the silencing cavity 7, the inlet hole 5 guides the airflow into the silencing cavity 7, and the outlet hole 6 outlets the airflow in the silencing cavity 7 out of the blade body 10.

[0036] Specifically, after the airflow reaches the leading edge 1, the static pressure reaches its maximum value. The airflow collides with the leading edge 1, and part of the airflow flows along the suction surface 2, while the other part flows along the pressure surface 4. Due to the gentler curvature of the pressure surface 4, the airflow velocity is relatively low, and the static pressure is high. The suction surface 2 has a larger curvature, and the airflow is accelerated due to the channel contraction, resulting in a velocity significantly higher than that of the pressure surface 4. The static pressure decreases, forming a low-pressure area. The pressure difference between the low-pressure area and the pressure surface 4 generates lift or aerodynamic load, and the two airflows re-merge at the trailing edge 3. Since this embodiment has an inlet hole 5 at the leading edge 1 or the pressure surface 4, the high-speed airflow flowing to the inlet hole 5 is guided to the silencing cavity 7. Through the silencing cavity 7, while ensuring the aerodynamic performance of the blade body 10, part of the airflow is transferred to the outlet hole 6. The high-speed airflow flowing out from the outlet hole 6 contacts and collides with the airflow at the trailing edge 3 or the suction surface 2, thereby causing the airfoil boundary layer to detach prematurely, further reducing noise.

[0037] In this embodiment, by providing an inlet hole 5 at the leading edge 1 or pressure surface 4, a portion of the high-speed airflow can be introduced into the silencing cavity 7. The main purpose is to reduce the high discrete noise generated by the blade's passing frequency, thereby reducing the direct impact of the airflow on the leading edge 1 and lowering the noise caused by airflow impact. Furthermore, the inlet hole 5 can alter the airflow distribution on the blade surface. Since part of the airflow is introduced into the silencing cavity 7, the velocity and pressure distribution of the airflow along the pressure surface 4 and suction surface 2 change, thus optimizing the airflow state on the blade surface and reducing eddy noise caused by uneven airflow distribution. In addition, the presence of the inlet hole 5 provides an additional flow channel for the airflow, allowing it to be partially diverted before entering the blade surface, thereby reducing the turbulence intensity on the blade surface, enhancing the stability of the airflow, and lowering aerodynamic noise caused by turbulence. The high-speed airflow exiting from the outlet hole 6 collides with the airflow at the trailing edge 3 or suction surface 2, causing the airfoil boundary layer to detach prematurely. The detachment of the boundary layer can change the airflow state at the trailing edge 3, reducing the interaction between the boundary layer and the trailing edge 3, thereby lowering the aerodynamic noise at the trailing edge 3. The synergistic effect of the inlet hole 5 and the outlet hole 6 can reduce the noise generated by airflow on the blade surface from multiple aspects. The inlet hole 5 reduces the impact noise of airflow on the leading edge 1, and the outlet hole 6 reduces the noise of the trailing edge 3 by changing the airflow state at the trailing edge 3. The combination of the two enables the entire blade structure to significantly reduce aerodynamic noise when running at high wind speed and large flow, thereby improving the quietness of equipment operation and environmental comfort.

[0038] In this embodiment, when the airflow enters the silencing cavity 7 through the inlet hole 5, the interior of the silencing cavity 7 provides a relatively enclosed space, where sound waves reflect back and forth between the inner walls, thereby reducing noise. There are velocity and pressure differences between the suction surface 2 and the pressure surface 4 of the blade. This pressure difference is one of the main causes of aerodynamic noise. The silencing cavity 7 can alter the path of the local airflow, allowing some airflow to enter the blade interior through the silencing cavity 7 and then rejoin the main flow through the outlet hole 6. The silencing cavity 7, together with the inlet hole 5 and the outlet hole 6, constitute a complete noise reduction system. The inlet hole 5 introduces airflow into the silencing cavity 7, which processes the noise in the airflow. The outlet hole 6 redirects the processed airflow to a suitable location (such as the trailing edge 3 or the suction surface 2). This synergistic effect ensures a more orderly flow of air on the blade surface, reducing noise caused by airflow turbulence.

[0039] It is worth noting that in this embodiment, the cross-sectional (longitudinal section) geometry of the blade body 10 is an airfoil, the line connecting the leading edge 1 and the trailing edge 3 is the airfoil chord, the lower surface or concave surface of the blade body 10 is the pressure surface 4, and the upper surface or convex surface of the blade body 10 is the suction surface 2. Since the airflow pressure at the leading edge 1 and the pressure surface 4 is greater than that at the suction surface 2, the inlet hole 5 can be set on either the leading edge 1 or the pressure surface 4. This setting of the inlet hole 5 can avoid pressure concentration at these two locations. Similarly, the outlet hole 6 can be set on either the trailing edge 3 or the suction surface 2 to ensure that the airflow flowing through the suction surface 2 can contact and collide with the airflow flowing through the silencer cavity 7.

[0040] See also Figures 1 to 3 , Figures 6 to 9 As shown, the suction surface 2 is provided with an inlet hole 5, which is close to the leading edge 1; the pressure surface 4 is provided with an outlet hole 6, which is close to the trailing edge 3.

[0041] Specifically, in combination Figure 8 The pressure cloud map shown and Figure 6The airfoil cross-section velocity vector diagram shown in this embodiment preferably features an inlet hole 5 on the suction surface 2 and an outlet hole 6 on the pressure surface 4. The region near the leading edge 1 of the suction surface 2 is a critical area where the airflow accelerates due to channel contraction and static pressure decreases, forming a low-pressure zone. Here, the airflow velocity is high and the pressure is low, easily generating a large pressure difference with the pressure surface 4, causing aerodynamic noise and eddies. By providing an inlet hole 5 in this region of the suction surface 2, some of the high-speed airflow can be guided into the silencing cavity 7, reducing the airflow velocity in this region and decreasing the pressure difference, thereby weakening the pressure difference between the low-pressure zone and the pressure surface 4. To reduce noise sources caused by pressure difference; trailing edge 3 is the re-merging point of two airflows (airflows flowing along suction surface 2 and pressure surface 4). The airflow here is complex and prone to generating eddies and pressure fluctuations, which in turn generate noise. An outlet hole 6 is set at the pressure surface 4 near trailing edge 3 to outlet the airflow in the silencing cavity 7 and allow it to contact and collide with the airflow at trailing edge 3, forming a thicker boundary layer airflow. This causes the airfoil boundary layer to fall off earlier, changes the airflow merging mode and pressure distribution at trailing edge 3, reduces the eddy intensity and pressure fluctuations at trailing edge 3, and reduces trailing edge 3 noise.

[0042] In this embodiment, a combination of active and passive noise reduction technologies is adopted to achieve a high-efficiency balance between aerodynamic performance and noise reduction effect, providing a better solution for the widespread application of axial flow fan blades. Passive suppression mainly reduces the generation or propagation of noise through the design of physical structures, such as the silencing cavity 7 set in this embodiment. Active suppression reduces aerodynamic noise by actively controlling the boundary layer. This is achieved by introducing changes in the boundary layer flow to reduce the energy content of the hydrodynamic pressure field, such as the outlet hole 6 set in this embodiment.

[0043] In one specific implementation, the optimal arrangement of the inlet hole 5 is on the pressure surface 4. The inlet hole 5 is a strip-shaped hole. This embodiment only shows one inlet hole 5. In other embodiments, the number of inlet holes 5 can be flexibly adjusted according to requirements. In addition, the position of the inlet hole 5 on the leading edge 1 or the pressure surface 4 can be flexibly adjusted according to noise reduction requirements. Taking the blade body 10 as a reference, the position of the inlet hole 5 is located within 110% of the blade's leading edge. The specific position can be designed according to the pressure concentration area of ​​the leading edge 1 and flexibly adjusted according to the airflow direction.

[0044] See also Figures 1 to 3 As shown, the blade body 10 has a double-layer airfoil structure. With the longitudinal section of the blade body 10 as the projection plane, the blade body 10 has an inner airfoil 801 and an outer airfoil 802. The inner airfoil 801 is located inside the outer airfoil 802. The inner airfoil 801 forms a sound-absorbing cavity 7. The inlet hole 5 guides the airflow from the outer airfoil 802 to the sound-absorbing cavity 7.

[0045] Specifically, in this embodiment, the blade body 10 has a double-layer airfoil structure. The inner airfoil 801 is equivalent to forming a hollow structure inside the blade body 10, that is, a sound-absorbing cavity 7. The outer airfoil 802 is equivalent to including a leading edge 1, a suction surface 2, a trailing edge 3, and a pressure surface 4 connected end to end. An inlet hole 5 is provided on the suction surface 2. The inlet hole 5 is inclined. One end of the inlet hole 5 extends to the inner airfoil 801, that is, the inlet hole 5 is connected to the sound-absorbing cavity 7. The other end of the inlet hole 5 extends to the outer airfoil 802. One end of the outlet hole 6 extends to the inner airfoil 801. The other end of the outlet hole 6 extends to the outer airfoil 802 along the airflow direction, that is, it extends to the trailing edge 3.

[0046] In this embodiment, the pressure surface 4 and suction surface 2 of the bio-airfoil 11 are modified to increase the pressure difference between the upper and lower surfaces of the blade, thereby improving the aerodynamic performance of the blade. At the same time, the pressure at the leading edge 1 of the airfoil is reduced, thus reducing the inflow noise at the leading edge 1. The inner airfoil 801 provides a relatively independent and sufficiently spacious area for noise absorption and reduction, allowing airflow to enter and undergo energy conversion and dissipation. The inlet hole 5 is located on the suction surface 2 of the outer airfoil 802 and extends obliquely to the inner airfoil 801 (silencing cavity 7). The outlet hole 6 extends from the inner airfoil 801 to the trailing edge 3 of the outer airfoil 802. This path design requires the airflow to travel a relatively long path after entering the silencer cavity 7 before exiting through the outlet hole 6. The outer airfoil 802 is still a complete airfoil structure, including the leading edge 1, suction surface 2, trailing edge 3, and pressure surface 4 connected end to end, which can ensure the basic aerodynamic performance of the blade. The airflow mainly flows on the surface of the outer airfoil 802, generating aerodynamic effects such as lift or thrust. The silencing cavity 7 formed by the inner airfoil 801 is relatively independent and does not significantly interfere with the basic aerodynamic shape of the outer airfoil 802. Thus, while achieving noise reduction, the aerodynamic performance of the blade is not significantly affected. The double-airfoil structure creates two different pressure zones inside the blade: the pressure distribution on the surface of the outer airfoil 802 and the pressure inside the inner airfoil 801 (silencing cavity 7). By rationally designing the position and shape of the inlet hole 5 and the outlet hole 6, the pressure inside the silencing cavity 7 can be adjusted to coordinate with the pressure distribution on the surface of the outer airfoil 802. The inlet hole 5 guides the high-pressure airflow from the suction surface 2 of the outer airfoil 802 into the silencing cavity 7, which can appropriately reduce the local pressure at the suction surface 2 and reduce the pressure difference between the suction surface 2 and the pressure surface 4, thereby reducing aerodynamic noise caused by the pressure difference and also helping to optimize the overall aerodynamic performance of the blade. By using a double-airfoil design, the aerodynamic performance of the fan is ensured while the aerodynamic noise of the fan is reduced by actively combining passive noise reduction methods, thereby achieving a balance between low noise and high-efficiency aerodynamic performance.

[0047] It is worth noting that, in order to facilitate the display of the internal structure of the blade body 10, the illustration only shows a section of the blade. In reality, the root and tip of the blade should be closed according to the design. The shape of the silencer cavity 7 cannot be effectively observed in the complete blade body 10. Therefore, even if the longitudinal section of the blade body 10 is used as the projection plane, the silencer cavity 7 in this embodiment is actually a relatively closed chamber with walls on both sides. The airflow can only flow into the silencer cavity 7 through the inlet hole 5.

[0048] See also Figures 1 to 3 As shown, the profile of the inner airfoil 801 is formed by proportionally scaling down the profile of the outer airfoil 802.

[0049] In this embodiment, since the inner airfoil 801 is formed by proportionally scaling down the profile of the outer airfoil 802, the inner airfoil 801 and the outer airfoil 802 have similar geometric shapes. According to the principle of similarity in fluid mechanics, this similarity ensures that the flow characteristics around the outer airfoil 802 and the inner airfoil 801 are similar. After being proportionally scaled down, the inner airfoil 801 can inherit the aerodynamic characteristics of the outer airfoil 802. This allows the inner and outer airfoils 802 to be considered as a whole when optimizing the overall aerodynamic performance of the blade. In addition, the proportionally scaled-down inner airfoil 801 makes the spatial distribution of the silencing cavity 7 more uniform. The shape and size of the silencing cavity 7 match the shape of the outer airfoil 802, providing a relatively stable silencing space at different positions on the blade. For the machining of the blade body 10, designing the inner and outer airfoils 802 using the same reference (the profile of the outer airfoil 802) ensures the consistency and accuracy of the design parameters. During the manufacturing process, the shape of the inner airfoil 801 can be obtained by scaling the outer airfoil 802 proportionally, which reduces errors in the design and manufacturing process.

[0050] As a specific implementation, to ensure the structural strength of the blade and the effective range of the silencing cavity 7, the scaling ratio of the silencing cavity 7 is set between 20% and 70%, that is, the minimum ratio is 20% of the total chord length of the inner airfoil to the outer airfoil, and the maximum scaling ratio is 70%. The noise reduction effect and noise reduction frequency range of the silencing cavity 7 are related to its internal dimensions and can be determined according to the formula... Perform calculations, where The square root of the ratio of cavity volume to opening area, where c is the speed of sound and f is the noise reduction frequency range, is used as an example of the model provided in this utility model. Its cavity volume is 917.76 mm²*X (X is the blade span), and its opening area is 2.83 mm²*X (X is the blade span). According to the calculation formula, the silencing cavity 7 structure designed with these dimensions can effectively reduce noise levels around 300 Hz. Different fans have different blade numbers and rotational speeds, resulting in different blade passage frequencies. The silencing frequency can be made the same as the blade passage frequency by changing the volume ratio and inlet area of ​​the silencing cavity 7, thus achieving the purpose of noise reduction.

[0051] As a specific implementation method, a silencing cavity 7 is formed inside the blade through the inlet hole 5, the inner airfoil 801, and the outlet hole 6. By rationally designing the internal airfoil space and the outlet area of ​​the outlet hole 6, the silencing frequency of the silencing cavity 7 can coincide with the blade frequency of the fan, thereby achieving the purpose of active noise reduction.

[0052] As one specific implementation, since the profile of the inner airfoil 801 is formed by proportionally scaling down the profile of the outer airfoil 802, see [reference needed]. Figure 3 As shown, the biological airfoil 11 is an owl wing airfoil with a span-to-width ratio of 40%. Due to its large overall thickness and curvature, to effectively establish the internal airfoil, the CST parametric method is used to parametrically model the profile of its pressure surface 4 (lower surface). Entropy production rate, lift-to-drag ratio, and noise values ​​at fixed points are used as target parameters, and a multi-objective optimization method is employed to optimize it, thereby obtaining the suction surface 2 profile of the outer airfoil 802. CST (Class-Shape Transformation) parametric method is a technique for describing and adjusting geometry, widely used in aerospace, fluid dynamics, and other fields. Through the CST parametric method, users can flexibly adjust the geometry of the airfoil to meet different design requirements. In this embodiment, the profile of the inner airfoil 801 is a proportionally scaled-down version of the profile of the outer airfoil 802. The specific scaling parameters are as follows: (Refer to [reference]). Figure 10 To fit the optimized curve, the fitted curve for this profile is as follows:

[0053] y = a1x + a2x 2 +a3x 3 +a4x 4 +c1

[0054] Wherein, a1 = -0.152 ± 0.038, a2 = 0.017 ± 0.0016, a3 = -2.87E-4 ± 2.44E-5, a4 = 1.28E-4 ± 1.21E-7, and c1 = 0.98819 ± 0.12741. It is worth noting that, due to the long numerical values ​​of the formula coefficients, the letters are only coefficients and are not specifically limited. The entropy yield, lift-to-drag ratio, and noise values ​​at fixed points are the target parameters. The optimization method is not described in detail in this embodiment, as it is a general method. This embodiment is only used to illustrate the optimization results.

[0055] See also Figures 1 to 5 As shown, it also includes a serrated structure 9, and an outlet hole 6 is provided on the suction surface 2. The outlet hole 6 is close to the tail edge 3, and the tail edge 3 is provided with a serrated structure 9, and the serrated structure 9 is located on the air outlet path of the outlet hole 6.

[0056] In this embodiment, the inlet hole 5 guides the airflow from the outer airfoil 802 to the silencing cavity 7. The outlet hole 6 is provided on the suction surface 2. The outlet hole 6 is not provided on the trailing edge 3. Therefore, a serrated structure 9 is provided at the trailing edge 3. According to the structural features, the airflow flowing out of the outlet hole 6 will flow through the serrated structure 9 again. While reducing the noise of the trailing edge 3, it can generate local velocity concentration airflow at the trailing edge 3, forming a thicker boundary layer airflow. The high-speed airflow flowing out of the outlet hole 6 comes into contact with and collides with the airflow at the trailing edge 3, thereby causing the boundary layer of the airfoil trailing edge 3 to fall off in advance, and further reducing the noise of the trailing edge 3.

[0057] In this embodiment, a complete airflow channel can be formed by setting the silencing cavity 7, the inlet hole 5, and the outlet hole 6. The serrated structure 9 is equivalent to improving the physical structure of the blade body 10 to reduce the generation and propagation of noise. Both the serrated structure 9 and the silencing cavity 7 reduce noise through passive suppression. Specifically, the serrated structure 9 can change the flow direction and velocity distribution of the airflow at the trailing edge 3, making the originally relatively regular airflow more complex and turbulent. This disturbance can destroy the large vortex structure formed at the trailing edge 3, splitting it into multiple smaller vortices. The serrated structure 9 provides multiple abrupt change points in the direction of airflow, making it difficult for the airflow to maintain a stable attachment state at the trailing edge 3. When the airflow flows through the serration 901, small separation vortices will form at the trailing edge of each serration 901. These separation vortices will gradually accumulate and cause the boundary layer to fall off prematurely. After the boundary layer falls off prematurely, the detached boundary layer airflow mixes with the external high-speed airflow. This mixing process can increase the energy exchange between airflows and accelerate the energy dissipation of the airflow. The serrated structure 9, together with the outlet hole 6, the silencing cavity 7, and the inlet hole 5, forms a complete noise reduction system. The airflow from the outlet hole 6 is further enhanced in noise reduction after passing through the serrated structure 9, making the entire blade more effective in aerodynamic noise control. This synergistic effect ensures that the airflow on the blade surface is more orderly, reducing the turbulence and impact of the airflow at the trailing edge 3, thereby achieving all-round noise reduction from the airflow source to the outlet of the trailing edge 3 and improving the overall noise reduction performance of the blade.

[0058] See also Figures 1 to 5 As shown, with the width direction of the blade body 10 as the projection plane, the serrated structure 9 includes multiple serrations 901. The multiple serrations 901 are arranged along the width direction of the trailing edge 3, and the tooth width of the serrations 901 is gradually reduced in the direction away from the trailing edge 3.

[0059] Specifically, taking the width direction of the trailing edge 3 of the blade body 10 as the projection plane, the serrated structure 9 is formed by multiple triangular serrations 901. Each serration 901 has the same shape and volume. Multiple serrations 901 are arranged in rows on the trailing edge 3. The width of the serrations 901 gradually decreases in the direction away from the trailing edge 3. A high-speed zone and a high-pressure zone are formed in the triangular area of ​​the serrations 901. At this time, the airflow is guided by the outlet hole 6, which can more effectively make the outlet airflow contact the boundary layer airflow on the blade surface.

[0060] In this embodiment, multiple serrations 901 are arranged in a row along the width direction of the trailing edge 3, and the tooth width of each serration 901 gradually decreases away from the trailing edge 3. When the airflow passes through the trailing edge 3, this gradually decreasing shape of the serrations 901 can disperse the airflow that was originally concentrated on impacting the trailing edge 3 onto multiple serrations 901. The serration structure 9 disrupts the originally regular airflow at the trailing edge 3, causing the airflow to form multiple small-scale vortices at the trailing edge 3 instead of a large vortex. The energy of the small-scale vortices is relatively low and attenuates faster during propagation. The boundary layer airflow that falls off prematurely mixes with the high-speed airflow outside. The serration structure 9 increases the turbulence of the airflow, making the energy exchange between the airflows more complete and accelerating the energy dissipation of the airflow. In addition, the multiple serrations 901 of the serration structure 9 are evenly distributed along the width direction of the trailing edge 3, which can ensure good noise reduction effect throughout the entire width range of the trailing edge 3. This evenly distributed serration structure 9 can avoid the noise concentration problem caused by poor noise reduction effect in local areas.

[0061] See also Figures 1 to 9 As shown, with the width direction of the blade body 10 as the projection plane, the outlet hole 6 includes multiple sub-channels 601, all of which are connected to the silencing cavity 7. The multiple sub-channels 601 are arranged in a one-to-one correspondence with multiple serrations 901, so that the air outlet path of the sub-channel 601 is located on the tip axis of the serration 901.

[0062] Specifically, in this embodiment, the outlet hole 6 can be a complete hole structure or multiple sub-channels 601. The sub-channels 601 are isolated from each other, that is, the airflow in the anechoic chamber 7 flows into multiple sub-channels 601 respectively, and the airflow flows out from multiple sub-channels 601 respectively. In this embodiment, multiple serrations 901 are also provided. One sub-channel 601 is corresponding to one serration 901. The air outlet path of the sub-channel 601 is located on the tip axis of the serration 901. When the high-speed airflow flows out from the sub-channel 601, because its direction and position are precisely aligned with the tip of the serration 901, the airflow will concentrate near the tip of the serration 901 and interact with the mainstream airflow at the trailing edge 3, thereby more effectively changing the flow state of the airflow, so that the high-speed airflow of the outlet hole 6 contacts and collides with the airflow at the trailing edge 3, thereby causing the boundary layer of the airfoil trailing edge 3 to fall off in advance.

[0063] In this embodiment, multiple sub-channels 601 correspond one-to-one with multiple serrations 901. Along the entire width of the trailing edge 3 of the blade, each serration 901 is uniformly impacted by the airflow exiting the sub-channels 601, making the airflow disturbance at the trailing edge 3 more uniform. This ensures that the airflow impact force is evenly distributed across the multiple serrations 901 at the trailing edge 3, avoiding excessive concentration of airflow impact force in one area due to a single outlet hole 6, thereby reducing potential blade damage caused by excessive local stress. The high-speed airflow exiting the sub-channels 601 collides with the airflow at the tips of the serrations 901 and at the trailing edge 3, causing the boundary layer to detach prematurely at multiple serration 901 locations. This boundary layer detachment at multiple points further alters the airflow state at the trailing edge 3, reducing the interaction noise between the boundary layer and the trailing edge 3. Furthermore, the mixing of the airflow exiting the multiple sub-channels 601 with the airflow at the trailing edge 3 forms a more complex turbulent structure. This complex turbulence accelerates the conversion of kinetic energy in the airflow into thermal energy, further reducing the kinetic energy of the airflow and minimizing the impact and collision at the trailing edge 3. Furthermore, if one sub-channel 601 is blocked, other sub-channels 601 can still normally discharge airflow, continuing to reduce trailing edge noise through the corresponding serrations 901. This ensures that the overall performance of the noise reduction system is not severely affected. The correspondence between multiple sub-channels 601 and multiple serrations 901 provides a redundant design. Even if the performance of a certain sub-channel 601 or serration 901 deteriorates due to wear or damage, other sub-channels 601 and serrations 901 can still continue to play a noise reduction role. In other embodiments, different sub-channels 601 can be optimized according to the airflow distribution and noise characteristics at the trailing edge 3 to adapt to different operating conditions. This flexibility allows the blade to maintain good noise reduction performance under various operating conditions.

[0064] See also Figure 6 As shown, the velocity vector diagram of the airfoil section clearly shows that the airflow flows through the inner airfoil to the trailing edge 3 of the blade. For the outer airfoil surface, it can be seen that the airflow flows steadily along the suction surface 2 of the blade. When it passes the outlet hole 6, the airflow streamline changes significantly, the airflow attached to the blade surface becomes chaotic, and the surface attachment flow ends. This also shows that the blade outlet hole 6 has the function of causing the boundary layer on the blade surface to fall off in advance.

[0065] See also Figures 1 to 9 As shown, with the width direction of the blade body 10 as the projection plane, the maximum width of the serration 901 is w, the length of the serration 901 is L, and the length L is specifically the vertical distance from the root to the tip of the serration 901. The airfoil chord length of the blade body 10 is c, the maximum width w ranges from 1.3% to 2.8% of the airfoil chord length c, and the length L ranges from 4.2% to 6.1% of the airfoil chord length c.

[0066] In this embodiment, since the blade body 10 is a double-layer airfoil structure, and the airfoil chord length is the same as that of the outer airfoil 802, the range of values ​​for the maximum width w and the length L are limited. Within this parameter range, the blade body 10 structure exhibits high aerodynamic and noise performance, while avoiding excessive airflow separation or the generation of new strong noise sources due to excessive size. By limiting the size of the serrations 901 within a reasonable range, an optimal balance can be achieved between the blade's noise reduction performance and aerodynamic performance. This allows the blade to meet noise requirements while maintaining good working efficiency, thus improving the overall performance of the product. Furthermore, the airfoil chord length is a commonly used parameter in airfoil design. The dimensions of the sawtooth structure 9 are adapted to the airfoil chord length of the blade. The chord length is a basic dimensional parameter of the blade. By proportionally limiting the maximum width and length of the sawtooth 901 to the chord length, it can be ensured that the sawtooth structure 9 plays an appropriate role in the overall scale of the blade. Using the airfoil chord length as the selection benchmark can enhance the versatility of the structure and facilitate its application on other airfoils. For blades of different sizes, as long as the sawtooth structure 9 is designed according to this proportional range, it can be ensured that the sawtooth 901 has similar effects in airflow control and noise reduction. Whether the blade is large or small, effective noise reduction function can be obtained through this proportional relationship.

[0067] See also Figures 1 to 9 As shown, the serrated structure 9 is integrally formed with the blade body 10. Taking the longitudinal section of the blade body 10 as the projection plane, the extension length of the serrated structure 9 in the airflow direction is 10% of the airfoil chord length of the blade body 10.

[0068] Specifically, the serrated structure 9 allows the airflow on the blade surface to concentrate and pass through the tooth surface rather than through gaps. The blade structure essentially includes two parts: the blade body 10 and the serrated structure 9. The serrated structure 9 and the blade body 10 are integrally formed. Although this embodiment is provided with a serrated structure 9, the serrated structure 9 is processed on the original size of the blade body 10. For example, the trailing edge 3 is cut to form the serrated structure 9. This does not change the maximum size of the blade body 10, nor does it extend the trailing edge 3 of the blade. Figures 1 to 3 The image shown is a partial view taken to show the relative position of the vent and the trailing edge 3 of the blade serration 901. In actual application, the serration structure 9 is integrally formed with the blade body 10.

[0069] In this embodiment, the serrated structure 9 is integrally formed with the blade body 10, avoiding the potential weakness at the connection point caused by additional connecting parts. The entire blade structure is a single unit with high structural strength, better able to withstand various loads under airflow. The integrally formed serrated structure 9 provides greater stability in airflow control. Since the serrated structure 9 and the blade body 10 are an integral unit, the position and shape of the serrations 901 will not change due to loosening or displacement at the connection point, thus ensuring the stability and consistency of the noise reduction effect. The extension length of the serrated structure 9 is 10% of the airfoil chord length of the blade body 10. This ratio is optimized. Within this length range, the serrated structure 9 can generate appropriate disturbance to the airflow, causing the boundary layer to detach prematurely, thereby reducing the noise of the trailing edge 3. Furthermore, the serrated structure 9 is manufactured at the trailing edge 3 of the blade body 10, without significantly affecting the overall aerodynamic shape of the blade. The aerodynamic performance of the blade is mainly determined by the shape of the blade body 10. The serrated structure 9 is relatively small in size and optimized in design, so it will not have a significant negative impact on aerodynamic performance.

[0070] It is worth noting that the extension length of the sawtooth structure 9 is not the same parameter as the length L. The extension length of the sawtooth structure 9 is greater than the length L. The extension length of the sawtooth structure 9 refers to the inclined surface of the sawtooth 901.

[0071] In one specific implementation, there is a certain distance between the outlet hole 6 and the root of the serrated structure 9. Taking the longitudinal section of the blade body 10 as the projection plane, the outlet hole 6 is located above the serrated structure 9, that is, the sub-channel 601 is exactly set above the triangular serration 901 to enhance the contact and collision effect. The shape of the outlet hole 6 is not limited, and the width of the sub-channel 601 should be 50% ± 5% of the maximum width w of the serration 901. The air outlet path of the outlet hole 6 is on the same straight line as the tooth surface of the serration 901. For example, the position of the air guide hole should be designed at a distance of 1% to 3% of the airfoil chord length c from the root of the serration 901. If the airfoil chord length is 100mm, the length L of the serration 901 should be between 4.2% and 6.1% * C. If the length of the serration 901 is 6% * C, then the projection position of the root of the serration 901 is at 94mm, and the corresponding air outlet position is set between the projection position of 91 and 93mm.

[0072] An axial flow fan blade includes multiple blade structures, the blade structures described above.

[0073] Specifically, an axial flow fan blade includes a hub and multiple blade structures, which are distributed circumferentially around the hub. When the motor drives the hub to rotate, it causes the blades to rotate around the axis. The leading edge 1 of the blade cuts into the air, and the airflow creates a pressure difference on the blade surface (low pressure on the upper surface and high pressure on the lower surface), generating lift.

[0074] In this embodiment, each blade structure employs the aforementioned noise reduction design, including an inlet hole 5, a silencing cavity 7, an outlet hole 6, and a serrated structure 9. When the axial flow fan blade rotates, the airflow passes over the blade surface. The inlet hole 5 guides part of the airflow into the silencing cavity 7, reducing the impact noise of the airflow on the leading edge 1 and suction surface 2 of the blade. The serrated structure 9 further optimizes the airflow at the trailing edge 3, causing the boundary layer to detach earlier and reducing the noise at the trailing edge 3. This all-round noise reduction design from the airflow source to the outlet of the trailing edge 3 significantly reduces the noise of the axial flow fan blade during operation. The inlet hole 5, the silencing cavity 7, the outlet hole 6, and the serrated structure 9 together constitute a multi-stage noise reduction system. When the airflow enters the leading edge 1 of the blade, it is guided into the silencing cavity 7, processed by the silencing cavity 7, and then flows out from the outlet hole 6. Finally, it is further optimized by the serrated structure 9. This multi-stage synergistic effect can effectively reduce noise in different frequency ranges, enabling the axial flow fan blade to maintain low-noise operation under various operating conditions.

[0075] An axial flow fan includes an axial flow fan blade, wherein the axial flow fan blade is as described above.

[0076] In this embodiment, the axial flow fan also includes a motor that drives the axial flow blades to rotate. Each blade of the axial flow fan adopts a multi-stage noise reduction design, including an inlet hole 5, a silencing cavity 7, an outlet hole 6, and a serrated structure 9. These designs can effectively reduce the noise generated when the airflow flows on the blade surface. When the motor drives the axial flow fan to rotate, the airflow enters the silencing cavity 7 through the inlet hole 5 at the leading edge 1 of the blade. After being processed by the silencing cavity 7, it flows out through the outlet hole 6. Finally, after being optimized by the serrated structure 9, the noise at the trailing edge 3 is reduced. The design of the serrated structure 9 and the silencing cavity 7 can reduce the impact and collision of the airflow at the trailing edge 3, reducing energy loss. This helps to improve the overall efficiency of the axial flow fan and reduce energy consumption. This comprehensive noise reduction measure significantly reduces the noise of the axial flow fan during operation, providing users with a quieter working environment.

[0077] It will be readily understood by those skilled in the art that the aforementioned advantageous methods can be freely combined and superimposed without conflict.

[0078] The above are merely preferred embodiments of this utility model and are not intended to limit the scope of this utility model. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model should be included within the protection scope of this utility model. The above are only preferred embodiments of this utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of this utility model, and these improvements and modifications should also be considered within the protection scope of this utility model.

Claims

1. A blade structure, characterized in that, include: Blade body (10); The blade body (10) includes a leading edge (1), a suction surface (2), a trailing edge (3), and a pressure surface (4) connected end to end. The pressure surface (4) and the suction surface (2) extend between the leading edge (1) and the trailing edge (3), respectively. In the direction of airflow, the leading edge (1) or the pressure surface (4) is provided with an inlet hole (5), and the trailing edge (3) or the suction surface (2) is provided with an outlet hole (6). The blade body (10) is provided with a silencing cavity (7). The inlet hole (5) and the outlet hole (6) are respectively connected to the silencing cavity (7). The inlet hole (5) guides the airflow into the silencing cavity (7), and the outlet hole (6) outlets the airflow in the silencing cavity (7) out of the blade body (10).

2. The blade structure according to claim 1, characterized in that, The suction surface (2) is provided with the inlet hole (5), which is close to the leading edge (1); the pressure surface (4) is provided with the outlet hole (6), which is close to the trailing edge (3).

3. The blade structure according to claim 1, characterized in that, The blade body (10) is a double-layer airfoil structure. Taking the longitudinal section of the blade body (10) as the projection plane, the blade body (10) has an inner airfoil (801) and an outer airfoil (802). The inner airfoil (801) is located inside the outer airfoil (802). The inner airfoil (801) forms the silencing cavity (7). The inlet hole (5) guides the airflow from the outer airfoil (802) to the silencing cavity (7).

4. The blade structure according to claim 3, characterized in that, The profile of the inner airfoil (801) is formed by proportionally reducing the profile of the outer airfoil (802).

5. The blade structure according to any one of claims 1 to 4, characterized in that, It also includes a serrated structure (9), the suction surface (2) is provided with the outlet hole (6), the outlet hole (6) is close to the tail edge (3), the tail edge (3) is provided with the serrated structure (9), and the serrated structure (9) is located on the air outlet path of the outlet hole (6).

6. The blade structure according to claim 5, characterized in that, With the width direction of the blade body (10) as the projection plane, the sawtooth structure (9) includes a plurality of sawtooths (901), the plurality of sawtooths (901) are arranged along the width direction of the trailing edge (3), and the tooth width of the sawtooths (901) is gradually reduced in the direction away from the trailing edge (3).

7. The blade structure according to claim 6, characterized in that, With the width direction of the blade body (10) as the projection plane, the outlet hole (6) includes multiple sub-channels (601), all of which are connected to the silencing cavity (7). The multiple sub-channels (601) are arranged in a one-to-one correspondence with the multiple serrations (901) so that the air outlet path of the sub-channel (601) is located on the tip axis of the serration (901).

8. The blade structure according to claim 7, characterized in that, With the width direction of the blade body (10) as the projection plane, the maximum width of the serration (901) is w, the length of the serration (901) is L, the airfoil chord length of the blade body (10) is c, the value range of the maximum width w is 1.3% to 2.8% of the airfoil chord length c, and the value range of the length L is 4.2% to 6.1% of the airfoil chord length c.

9. The blade structure according to claim 5, characterized in that, The serrated structure (9) is integrally formed with the blade body (10). Taking the longitudinal section of the blade body (10) as the projection plane, the extension length of the serrated structure (9) in the airflow direction is 10% of the airfoil chord length of the blade body (10).

10. An axial flow fan blade, comprising a plurality of blade structures, characterized in that, The blade structure is the blade structure according to any one of claims 1 to 9.

11. An axial flow fan, comprising axial flow blades, characterized in that, The axial flow fan blade is the axial flow fan blade as described in claim 10.

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