Blade structure, axial flow fan blade, axial flow fan and air conditioner

Abstract

The invention provides a blade structure, an axial flow blade, an axial flow fan and an air conditioner, the blade structure comprises a blade body, the blade body comprises a front edge, a suction surface, a tail edge and a pressure surface which are sequentially connected end to end, the pressure surface and the suction surface respectively extend between the front edge and the tail edge, in the airflow flowing direction, the front edge or the pressure surface is provided with a leading-in hole, and the leading-in hole is communicated with the suction surface. A leading-out hole is formed in the tail edge or the suction surface; a silencing cavity is formed in the blade body, the guide-in hole and the guide-out hole communicate with the silencing cavity, the guide-in hole guides airflow into the silencing cavity, and the guide-out hole guides the airflow in the silencing cavity out of the blade body. The leading-in holes reduce impact noise of airflow to the front edge, and the leading-out holes reduce noise of the trailing edge by changing the flowing state of the airflow at the trailing edge.

Description

Technical Field

[0001] The present invention belongs to the technical field of air conditioners, and particularly relates to a blade structure, an axial-flow impeller, an axial-flow fan, and an air conditioner. Background Art

[0002] With the increasing demand of modern industrial and civil equipment for efficient ventilation, heat dissipation, and air circulation, axial-flow impellers are widely used as key pneumatic components. However, when traditional axial-flow impellers operate at high wind speeds and large flow rates, due to pneumatic noise and mechanical vibration problems, the equipment generates relatively high operating noise, directly affecting the user experience and environmental comfort. Although existing technologies reduce noise by optimizing the blade geometry or using sound-absorbing materials, it is often difficult to achieve a significant noise reduction effect while ensuring the aerodynamic performance. Especially in application scenarios with high wind speeds and large flow rates, the interaction between the blade and the airflow easily causes pneumatic noise. Summary of the Invention

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

[0004] The present invention 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 in sequence from head to tail. The pressure surface and the suction surface extend between the leading edge and the trailing edge respectively. In the airflow direction, an inlet hole is provided on the leading edge or the pressure surface, and an outlet hole is provided on the trailing edge or the suction surface;

[0006] A sound-absorbing cavity is provided inside the blade body. The inlet hole and the outlet hole are respectively communicated with the sound-absorbing cavity. The inlet hole guides the airflow into the sound-absorbing cavity, and the outlet hole guides the airflow in the sound-absorbing cavity out of the blade body.

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

[0008] In some embodiments, the blade body is a double-layer airfoil structure. Taking 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 the inner airfoil forms the sound-absorbing cavity. The inlet hole guides the airflow from the outer airfoil into the sound-absorbing cavity.

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

[0010] In some embodiments, it further includes a serrated structure. The suction surface is provided with the outlet holes. The outlet holes are close to the trailing edge. The trailing edge is provided with the serrated structure, and the serrated structure is located on the air outlet path of the outlet holes.

[0011] In some embodiments, taking the width direction of the blade body as the projection plane, the serrated structure includes a plurality of serrations. The plurality of serrations are arranged along the width direction of the trailing edge, and the tooth width of the serrations is tapered in a direction away from the trailing edge.

[0012] In some embodiments, taking the width direction of the blade body as the projection plane, the outlet holes include a plurality of sub-channels. The plurality of sub-channels are all communicated with the sound-absorbing cavity. The plurality of sub-channels are arranged in one-to-one correspondence with the plurality of serrations, so that the air outlet path of the sub-channels is located on the tip axis of the serrations.

[0013] In some embodiments, taking the width direction of the blade body as the projection plane, the maximum width of the serrations is w, the length of the serrations is L, the airfoil chord length of the blade body is c, the value range of the maximum width w is 1.3% - 2.8% of the airfoil chord length c, and the value range of the length L is 4.2% - 6.1% of the airfoil chord length c.

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

[0015] An axial-flow wind blade includes a plurality of blade structures, and the blade structures are the above-mentioned blade structures.

[0016] An axial-flow fan includes an axial-flow wind blade, and the axial-flow wind blade is the above-mentioned axial-flow wind blade.

[0017] An air conditioner includes an axial-flow fan, and the axial-flow fan is the above-mentioned axial-flow fan.

[0018] A blade structure, an axial-flow wind blade, an axial-flow fan and an air conditioner provided by the present invention have the following beneficial effects:

[0019] In the present invention, by providing an inlet hole at the leading edge or the pressure surface, a part of the high-speed airflow can be introduced into the muffler cavity, thereby reducing the direct impact of the airflow on the leading edge, reducing the noise generated by the airflow impact, and the inlet hole can change the distribution of the airflow on the blade surface. Since a part of the airflow is introduced into the muffler cavity, the airflow velocity and pressure distribution along the pressure surface and the suction surface change, thereby optimizing the airflow flow state on the blade surface and reducing the vortex noise generated by the uneven distribution of the airflow. In addition, the presence of the inlet hole can provide an additional flow path for the airflow, enabling the airflow to be partially diverted before entering the blade surface, thereby reducing the turbulence intensity of the airflow on the blade surface, enhancing the stability of the airflow flow, and reducing the aerodynamic noise caused by turbulence. The high-speed airflow flowing out of the outlet hole contacts and collides with the airflow at the trailing edge or the suction surface, which can cause the airfoil boundary layer to shed in advance. The shedding of the boundary layer can change the flow state of the airflow at the trailing edge, reduce the interaction between the boundary layer and the trailing edge, and thereby reduce the aerodynamic noise at the trailing edge. The combined action of the inlet hole and the outlet hole can reduce the noise generation of the airflow on the blade surface from multiple aspects. The inlet hole reduces the impact noise of the airflow on the leading edge, and the outlet hole reduces the trailing edge noise by changing the airflow flow state at the trailing edge. The combination of the two enables the entire blade structure to significantly reduce the aerodynamic noise during high wind speed and large flow operation, improving the quietness of the equipment operation and the environmental comfort.

[0020] In the present invention, when the airflow enters the muffler cavity through the inlet hole, a relatively enclosed space is provided inside the muffler cavity. Its main purpose is to reduce the high-frequency discrete noise generated by the passing frequency of the blade. The sound wave reflects back and forth between the inner wall surfaces of the cavity, thereby achieving the purpose of reducing noise. There is a velocity difference and a pressure difference between the suction surface and the pressure surface of the blade. This pressure difference is one of the main reasons for generating aerodynamic noise. The muffler cavity can change the path of the local airflow, enabling part of the airflow to enter the blade interior through the muffler cavity and rejoin the mainstream through the outlet hole. The muffler cavity, together with the inlet hole and the outlet hole, constitutes a complete noise reduction system. The inlet hole introduces the airflow into the muffler cavity, the muffler cavity processes the noise in the airflow, and the outlet hole reintroduces the processed airflow to a suitable position (such as the trailing edge or the suction surface). This combined action can ensure that the airflow flows more orderly on the blade surface, reducing the noise generated by the airflow disorder. Brief Description of the Drawings

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings described below are only exemplary. For those of ordinary skill in the art, without creative efforts, other implementation drawings can also be obtained based on the provided drawings.

[0022] Figure 1 Schematic diagram of the blade structure according to an embodiment of the present invention;

[0023] Figure 2 Schematic diagram of the longitudinal section of the blade structure according to an embodiment of the present invention;

[0024] Figure 3 Schematic diagram of the inner airfoil, outer airfoil and biological airfoil according to an embodiment of the present invention;

[0025] Figure 4 Schematic diagram of the sawtooth structure according to an embodiment of the present invention;

[0026] Figure 5 Schematic diagram of the sawtooth according to an embodiment of the present invention;

[0027] Figure 6 Velocity vector diagram of the airfoil section according to an embodiment of the present invention;

[0028] Figure 7 Velocity vector diagram of the local section of the trailing edge according to an embodiment of the present invention;

[0029] Figure 8 Pressure contour map distribution according to an embodiment of the present invention;

[0030] Figure 9 Volume distribution diagram of the velocity contour map according to an embodiment of the present invention;

[0031] Figure 10 Fitted and optimized profile line of the inner airfoil and outer airfoil according to an embodiment of the present invention.

[0032] Accompanying drawings: 1 - leading edge; 2 - suction surface; 3 - trailing edge; 4 - pressure surface; 5 - inlet hole; 6 - outlet hole; 601 - sub-channel; 7 - sound absorption cavity; 801 - inner airfoil; 802 - outer airfoil; 9 - sawtooth structure; 901 - sawtooth; 10 - blade body; 11 - biological airfoil. Detailed implementation manners

[0033] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way restrictive of the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0034] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by orientation terms such as "front, rear, upper, lower, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom", etc. is usually based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description. Without contrary description, these orientation terms do not indicate and imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation on the protection scope of the present invention; the orientation terms "inside, outside" refer to the inside and outside relative to the contour of each component itself.

[0035] For the sake of convenience of description, spatial relative terms such as "above...", "over...", "on the upper surface of...", "upper...", etc. can be used here to describe the spatial positional relationship between a device or feature shown in the drawings and other devices or features. It should be understood that the spatial relative terms are intended to include different orientations in use or operation in addition to the orientation described in the drawings for the device. For example, if the device in the drawing is inverted, the device described as "above other devices or structures" or "over other devices or structures" will then be positioned "below other devices or structures" or "under other devices or structures".

[0036] Referring jointly to 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 that are connected end to end in sequence. The pressure surface 4 and the suction surface 2 extend between the leading edge 1 and the trailing edge 3 respectively. In the airflow direction, an inlet hole 5 is provided on the leading edge 1 or the pressure surface 4, and an outlet hole 6 is provided on the trailing edge 3 or the suction surface 2; a sound-absorbing cavity 7 is provided inside the blade body 10, and the inlet hole 5 and the outlet hole 6 are respectively communicated with the sound-absorbing cavity 7. The inlet hole 5 guides the airflow into the sound-absorbing cavity 7, and the outlet hole 6 discharges the airflow in the sound-absorbing cavity 7 out of the blade body 10.

[0037] Specifically, after the air flow reaches the leading edge 1 position, the static pressure reaches the highest value. The air flow collides with the leading edge 1. Part of the air flow flows along the suction surface 2, and the other part of the air flow flows along the pressure surface 4. Due to the relatively gentle curvature of the pressure surface 4, the air flow velocity is relatively low and the static pressure is relatively high. The curvature of the suction surface 2 is relatively large, and the air flow accelerates due to the contraction of the flow channel, and the velocity is significantly higher than that of the pressure surface 4, and the static pressure decreases to form 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 air flows re-converge at the trailing edge 3. Since the inlet hole 5 is provided at the leading edge 1 or the pressure surface 4 in this embodiment, the high-speed air flow flowing to the inlet hole 5 is diverted into the sound-absorbing cavity 7. Through the sound-absorbing cavity 7, while ensuring the aerodynamic performance of the blade body 10, part of the air flow is diverted to the outlet hole 6. The high-speed air flow flowing out from the outlet hole 6 contacts and collides with the air flow at the trailing edge 3 or the suction surface 2, so that the airfoil boundary layer falls off in advance, thereby further reducing the noise.

[0038] In this embodiment, by providing the inlet hole 5 at the leading edge 1 or the pressure surface 4, part of the high-speed air flow can be introduced into the sound-absorbing cavity 7. Its main purpose is to reduce the high-frequency discrete noise generated by the passing frequency of the blade, thereby reducing the direct impact of the air flow on the leading edge 1 and reducing the noise generated by the air flow impact. Moreover, the inlet hole 5 can change the distribution of the air flow on the blade surface. Since part of the air flow is introduced into the sound-absorbing cavity 7, the air flow velocity and pressure distribution along the pressure surface 4 and the suction surface 2 change, thereby optimizing the air flow state on the blade surface and reducing the eddy current noise generated by the uneven distribution of the air flow. In addition, the existence of the inlet hole 5 can provide an additional flow channel for the air flow, so that the air flow can be partially diverted before entering the blade surface, thereby reducing the turbulence intensity of the air flow on the blade surface, enhancing the stability of the air flow, and reducing the aerodynamic noise caused by turbulence. The high-speed air flow flowing out from the outlet hole 6 contacts and collides with the air flow at the trailing edge 3 or the suction surface 2, which can make the airfoil boundary layer fall off in advance. The shedding of the boundary layer can change the flow state of the air flow at the trailing edge 3 and reduce the interaction between the boundary layer and the trailing edge 3, thereby reducing the aerodynamic noise at the trailing edge 3. The combined action of the inlet hole 5 and the outlet hole 6 can reduce the noise generation of the air flow on the blade surface from multiple aspects. The inlet hole 5 reduces the impact noise of the air flow on the leading edge 1, and the outlet hole 6 reduces the noise at the trailing edge 3 by changing the flow state of the air flow at the trailing edge 3. The combination of the two enables the entire blade structure to significantly reduce the aerodynamic noise during high wind speed and large flow operation, improving the quietness of the equipment operation and the environmental comfort.

[0039] In this embodiment, when the airflow enters the muffler chamber 7 through the inlet hole 5, a relatively enclosed space is provided inside the muffler chamber 7. Sound waves are reflected back and forth between the inner wall surfaces of the chamber, thereby achieving the purpose of reducing noise. There are velocity differences and pressure differences between the suction surface 2 and the pressure surface 4 of the blade. This pressure difference is one of the main reasons for generating aerodynamic noise. The muffler chamber 7 can change the path of the local airflow, enabling part of the airflow to enter the blade interior through the muffler chamber 7 and rejoin the mainstream through the outlet hole 6. The muffler chamber 7, the inlet hole 5, and the outlet hole 6 together form a complete noise reduction system. The inlet hole 5 introduces the airflow into the muffler chamber 7, the muffler chamber 7 processes the noise in the airflow, and the outlet hole 6 reintroduces the processed airflow to a suitable position (such as the trailing edge 3 or the suction surface 2). This synergistic effect can ensure that the airflow on the blade surface flows more orderly, reducing the noise generated due to airflow turbulence.

[0040] It should be noted that in this embodiment, the cross-sectional (longitudinal section) geometric shape of the blade body 10 is airfoil-shaped. The line connecting the leading edge 1 and the trailing edge 3 is the chord length of the airfoil. 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, therefore, the inlet hole 5 can be selectively arranged either on the leading edge 1 or on the pressure surface 4. Such an arrangement of the inlet hole 5 can avoid pressure concentration at these two locations. Similarly, the outlet hole 6 can be selectively arranged either on the trailing edge 3 or on 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 muffler chamber 7.

[0041] Combined with Figures 1 to 3 、 Figures 6 to 9 As shown, an inlet hole 5 is provided on the suction surface 2, and the inlet hole 5 is close to the leading edge 1; an outlet hole 6 is provided on the pressure surface 4, and the outlet hole 6 is close to the trailing edge 3.

[0042] Specifically, combined with Figure 8 the shown pressure contour map and Figure 6The airfoil section velocity vector diagram shown. In the preferred embodiment of the present example, an inlet hole 5 is provided on the suction surface 2, and an outlet hole 6 is provided on the pressure surface 4. The area near the leading edge 1 of the suction surface 2 is a key position where the air flow accelerates due to the contraction of the flow channel and the static pressure decreases, forming a low-pressure area. Here, the air flow velocity is high and the pressure is low, which is likely to generate a large pressure difference with the pressure surface 4, causing aerodynamic noise and vortices. By providing the inlet hole 5 in this area of the suction surface 2, part of the high-speed air flow can be introduced into the sound-absorbing cavity 7, reducing the air flow velocity in this area and the pressure difference, thereby weakening the pressure difference between the low-pressure area and the pressure surface 4 and reducing the noise source caused by the pressure difference; The trailing edge 3 is the position where two air flows (the air flows along the suction surface 2 and the pressure surface 4) re-converge. The air flow here is complex, prone to generating vortices and pressure fluctuations, and thus generating noise. By providing the outlet hole 6 near the trailing edge 3 on the pressure surface 4, the air flow in the sound-absorbing cavity 7 can be exported, contacting and colliding with the air flow at the trailing edge 3 to form a thicker boundary layer air flow, causing the airfoil boundary layer to shed in advance, changing the air flow convergence mode and pressure distribution at the trailing edge 3, reducing the vortex intensity and pressure fluctuations at the trailing edge 3, and reducing the noise at the trailing edge 3.

[0043] In this embodiment, an active and passive noise reduction technology combination method is adopted to finally achieve an efficient balance between aerodynamic performance and noise reduction effect, providing a better solution for the wide application of axial flow fan blades. Among them, passive suppression mainly reduces the generation or propagation of noise through the design of physical structures. For example, the sound-absorbing cavity 7 set in this embodiment. Active suppression reduces aerodynamic noise through active control of the boundary layer. By introducing changes in the boundary layer flow to reduce the energy content of the hydrodynamic pressure field, such as the setting of the outlet hole 6 in this embodiment.

[0044] As a specific implementation method, the optimal setting method of the inlet hole 5 is to be set on the pressure surface 4. The shape of the inlet hole 5 is a strip-shaped hole. In this embodiment, only one inlet hole 5 is shown. In other embodiments, the setting quantity can be flexibly adjusted according to requirements. In addition, according to the noise reduction requirements, the setting position of the inlet hole 5 on the leading edge 1 or the pressure surface 4 can be flexibly adjusted. If the entire blade body 10 is taken as a reference, the position of the inlet hole 5 is within 110% of the blade along the blade leading edge 1, and the specific position can be designed according to the pressure concentration area of the leading edge 1 and flexibly adjusted according to the air flow direction.

[0045] Combined with reference to Figures 1 to 3 As shown, 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, and the inner airfoil 801 forms the sound-absorbing cavity 7. The inlet hole 5 diverts the air flow from the outer airfoil 802 into the sound-absorbing cavity 7.

[0046] Specifically, the blade body 10 in this embodiment has a double-layer airfoil structure. The inner airfoil 801 forms a hollow structure inside the blade body 10, that is, the sound-absorbing cavity 7. The outer airfoil 802 includes a leading edge 1, a suction surface 2, a trailing edge 3, and a pressure surface 4 that are connected end to end in sequence. 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 communicates with 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, and the other end of the outlet hole 6 extends along the air flow direction to the outer airfoil 802, that is, to the trailing edge 3.

[0047] In this embodiment, by improving the profiles of the pressure surface 4 and the suction surface 2 of the biological airfoil 11, the pressure difference between the upper and lower surfaces of the blade is increased to improve the aerodynamic performance of the blade. At the same time, the pressure at the leading edge 1 of the airfoil is reduced to lower the inflow noise at the leading edge 1 of the airfoil. The inner airfoil 801 provides a relatively independent and sufficient space area for the absorption and reduction of noise, enabling the air flow to enter and undergo energy conversion and dissipation. The inlet hole 5 is provided on the suction surface 2 of the outer airfoil 802 and extends obliquely to the inner airfoil 801 (sound-absorbing cavity 7). The outlet hole 6 extends from the inner airfoil 801 to the trailing edge 3 of the outer airfoil 802. Such a path design allows the air flow to pass through a longer path before being discharged from the outlet hole 6 after entering the sound-absorbing cavity 7. The outer airfoil 802 remains a complete airfoil structure, including a leading edge 1, a suction surface 2, a trailing edge 3, and a pressure surface 4 that are connected end to end in sequence, which can ensure the basic aerodynamic performance of the blade. The air flow mainly flows on the surface of the outer airfoil 802 to generate aerodynamic effects such as lift or thrust. The sound-absorbing cavity 7 formed by the inner airfoil 801 is relatively independent and will not significantly interfere with the basic aerodynamic shape of the outer airfoil 802, thus ensuring that the aerodynamic performance of the blade is not significantly affected while achieving the noise reduction function. The double-layer airfoil structure results in two different pressure regions inside the blade: the pressure distribution on the surface of the outer airfoil 802 and the pressure inside the inner airfoil 801. By reasonably designing the positions and shapes of the inlet hole 5 and the outlet hole 6, the pressure inside the sound-absorbing cavity 7 can be adjusted to be coordinated with the pressure distribution on the surface of the outer airfoil 802. The inlet hole 5 introduces the high-pressure air flow at the suction surface 2 of the outer airfoil 802 into the sound-absorbing 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 the aerodynamic noise caused by the pressure difference and also helping to optimize the overall aerodynamic performance of the blade. Through the double-layer airfoil design, while ensuring the aerodynamic performance of the fan, the aerodynamic noise of the fan is reduced by actively combining passive noise reduction methods, thus achieving the balance between low noise and high aerodynamic performance.

[0048] It should be noted that for the convenience of showing the internal structure of the blade body 10, only a section of the wind blade is intercepted in the figure. In actual wind blades, according to the design, the blade root and the tip should be in a closed state. The shape of the sound-absorbing cavity 7 cannot be effectively observed in the complete blade body 10. Therefore, even when the longitudinal section of the blade body 10 is used as the projection plane, the sound-absorbing cavity 7 in this embodiment is substantially a relatively closed chamber, with wall bodies provided on both sides thereof, and the air flow can only flow into the sound-absorbing cavity 7 through the inlet holes 5.

[0049] Combined with the reference to Figures 1 to 3 As shown, the profile line of the inner airfoil 801 is formed by proportionally reducing the profile line of the outer airfoil 802.

[0050] In this embodiment, since the inner airfoil 801 is formed by proportionally reducing the profile line of the outer airfoil 802, the inner airfoil 801 and the outer airfoil 802 have similar geometric shapes. According to the similarity principle in fluid mechanics, such a similar shape can ensure that the flow characteristics of the air flow around the outer airfoil 802 and the inner airfoil 801 have a certain similarity. After the inner airfoil 801 is proportionally reduced, it can inherit the aerodynamic characteristics of the outer airfoil 802. This enables 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 reduced inner airfoil 801 makes the spatial distribution of the sound-absorbing cavity 7 more uniform. The shape and size of the sound-absorbing cavity 7 match the shape of the outer airfoil 802, and can provide a relatively stable sound-absorbing space at different positions of the blade. For the machining of the blade body 10, designing the inner and outer airfoils 802 based on the same reference (the profile line of the outer airfoil 802) can ensure the consistency and accuracy of the design parameters. During the manufacturing process, only by performing proportional scaling based on the profile line of the outer airfoil 802 can the shape of the inner airfoil 801 be obtained, reducing the errors in the design and manufacturing processes.

[0051] As a specific implementation manner, to ensure the structural strength of the blade and the action range of the sound-absorbing cavity 7, the scaling ratio of the profile line of the sound-absorbing cavity 7 is set between 20% and 70%, that is, the minimum ratio is that the total chord length of the inner airfoil is 20% of the outer airfoil, and the maximum scaling ratio is 70%. The noise reduction effect and the noise reduction frequency range of the sound-absorbing cavity 7 are related to its internal dimensions and can be calculated according to the formula for calculation, where The square root of the ratio of the cavity volume to the opening area, where c is the speed of sound and f is the frequency band for noise reduction. Taking the model provided by the present invention as an example, its cavity volume is 917.76 mm² * X (X is the blade length along the span), and the opening area of the inlet hole 5 is 2.83 mm * X (X is the blade length along the span). According to the calculation formula, the muffler cavity 7 structure designed with these dimensions can effectively reduce the noise value at around 300 Hz. Different fans have different passing frequencies of the fan blades according to their different numbers of blades and rotational speeds. The muffling frequency can be made the same as the passing frequency of the fan blades by changing the volume ratio and inlet area of the muffler cavity 7 to achieve the purpose of noise reduction.

[0052] As a specific implementation, through the inlet hole 5, the inner airfoil 801, and the outlet hole 6, a muffler cavity 7 is formed inside the blade. By reasonably designing the internal airfoil space and the outlet area of the outlet hole 6, the muffling frequency of the muffler cavity 7 can be made to coincide with the blade frequency of the fan, thereby achieving the purpose of active noise reduction.

[0053] As a specific implementation, since the profile of the inner airfoil 801 is formed by proportionally reducing the profile of the outer airfoil 802, see Figure 3 shown, in which the biological airfoil 11 is shown. The cross-sectional airfoil of the owl wing along the span ratio of 40% has a relatively large overall thickness and curvature. To effectively establish the internal airfoil, the CST parametric method is used to parametrically model the profile of the pressure surface 4 (lower surface), and the entropy production rate, lift-drag ratio, and noise value at fixed points are used as target parameters, and the multi-objective optimization method is used to optimize it to obtain the profile of the suction surface 2 of the outer airfoil 802. The CST (Class-Shape Transformation) parametric method is a technology for describing and adjusting geometric shapes, widely used in fields such as aviation and fluid dynamics. Through the CST parametric method, users can flexibly adjust the geometric shape of the airfoil to meet different design requirements. In this embodiment, the profile of the inner airfoil 801 is proportionally reduced from the profile of the outer airfoil 802. The specific reduction parameters are: combined with see Figure 10 For the fitted optimized curve, the profile fitting curve is as follows:

[0054] y = a1x + a2x 2 + a3x 3 + a4x 4 + c1

[0055] Among them, a1 = -0.152 ± 0.038, a2 = 0.017 ± 0.0016, a3 = -2.87E-4 ± 2.44E-5, a4 = 1.28E-4 ± 1.21E-7, c1 = 0.98819 ± 0.12741. It should be noted that since the numerical values of the formula coefficients are relatively long and the letters are only coefficients without special limitations, the entropy production rate, lift-drag ratio, and noise value at the fixed point are target parameters, and the optimization method does not need to be described in detail in this embodiment. It is a general method, and this embodiment is only used to illustrate the optimization results.

[0056] Referring to Figures 1 to 5 As shown, it further includes a serrated structure 9. An outlet hole 6 is provided on the suction surface 2. The outlet hole 6 is close to the trailing edge 3. The trailing 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.

[0057] In this embodiment, the inlet hole 5 diverts the airflow from the outer airfoil 802 to the muffler cavity 7. The outlet hole 6 is provided on the suction surface 2 and is not provided on the trailing edge 3. Therefore, a serrated structure 9 is provided at the trailing edge 3. According to the structural characteristics, the airflow flowing out of the outlet hole 6 will flow through the serrated structure 9 again. While reducing the noise at the trailing edge 3, it can generate a locally velocity-concentrated airflow at the trailing edge 3, forming a relatively thick boundary layer airflow. The high-speed airflow flowing out of the outlet hole 6 contacts and collides with the airflow at the trailing edge 3, so that the boundary layer at the trailing edge 3 of the airfoil falls off in advance, and further reduces the noise at the trailing edge 3.

[0058] In this embodiment, by setting up the sound-absorbing cavity 7, the inlet hole 5 and the outlet hole 6, a complete air flow channel can be formed. The setting of the serrated structure 9 is also equivalent to reducing the generation and propagation of noise by improving the physical structure of the blade body 10. Both the serrated structure 9 and the sound-absorbing cavity 7 reduce noise through passive suppression. Specifically, the serrated structure 9 can change the flow direction and velocity distribution of the air flow at the trailing edge 3, making the originally relatively regular air flow become complex and disordered. This disturbing effect can destroy the large eddy structure formed at the trailing edge 3 and split it into multiple smaller eddies. The serrated structure 9 provides multiple abrupt direction change points for the air flow, making it difficult for the air flow to maintain a stable attachment state at the trailing edge 3. When the air flow passes through the serrations 901, small separated eddies will form at the trailing edge of each serration 901. These separated eddy flows will gradually accumulate and cause the boundary layer to shed in advance. After the boundary layer sheds in advance, the shed boundary layer air flow will mix with the external high-speed air flow. This mixing process can increase the energy exchange between the air flows and accelerate the energy dissipation of the air flow. The serrated structure 9, together with the noise reduction structures such as the outlet hole 6, the sound-absorbing cavity 7, and the inlet hole 5, forms a complete noise reduction system. After the air flow flowing out of the outlet hole 6 passes through the serrated structure 9, its noise reduction effect is further enhanced, making the entire blade more effective in terms of aerodynamic noise control. This synergistic effect can ensure that the air flow on the blade surface is more orderly, reduce the disorder and impact of the air flow at the trailing edge 3, and thus achieve all-round noise reduction from the air flow source to the outlet of the trailing edge 3, improving the overall noise reduction performance of the blade.

[0059] With reference to Figures 1 to 5 As shown, taking the width direction of the blade body 10 as the projection plane, the serrated structure 9 includes a plurality of serrations 901. The plurality of serrations 901 are arranged along the width direction of the trailing edge 3, and the tooth width of the serration 901 is tapered in a direction away from the trailing edge 3.

[0060] 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 a plurality of triangular serrations 901. The shape and volume of each serration 901 are the same. The plurality of serrations 901 are arranged in rows on the trailing edge 3, and the width of the serration 901 is tapered in a direction away from the trailing edge 3. A high-speed area and a high-pressure area are formed in the triangular area of the serration 901. At this time, through the guidance of the air flow by the outlet hole 6, the outlet air flow can more effectively contact the boundary layer air flow on the blade surface.

[0061] In this embodiment, multiple serrations 901 are arranged in rows along the width direction of the trailing edge 3, and the tooth width of each serration 901 tapers in a direction away from the trailing edge 3. When the air flow passes through the trailing edge 3, this tapered serration 901 shape can disperse the air flow that originally concentrated on impacting the trailing edge 3 onto multiple serrations 901. The serration structure 9 disrupts the originally regular air flow at the trailing edge 3, causing the air flow to form multiple small-scale vortices at the trailing edge 3 instead of a large one. The energy of the small-scale vortices is relatively low and decays faster during propagation. The boundary layer air flow that detaches in advance mixes with the external high-speed air flow. The serration structure 9 increases the turbulence of the air flow, making the energy exchange between the air flows more sufficient and accelerating the energy dissipation of the air flow. 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 effects throughout the width range of the trailing edge 3. This evenly distributed serration structure 9 can avoid the problem of noise concentration caused by poor noise reduction effects in local areas.

[0062] Combined with reference to Figures 1 to 9 As shown, taking the width direction of the blade body 10 as the projection plane, the outlet holes 6 include multiple sub-channels 601. The multiple sub-channels 601 are all communicated with the sound absorption cavity 7. The multiple sub-channels 601 are arranged in 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.

[0063] Specifically, the outlet holes 6 of this embodiment can either be a complete hole structure or multiple sub-channels 601. The sub-channels 601 are isolated from each other, that is, the air flow in the sound absorption cavity 7 flows into the multiple sub-channels 601 respectively, and the air flow flows out from the multiple sub-channels 601 respectively. In combination with this embodiment, multiple serrations 901 are also provided. One sub-channel 601 is arranged in one-to-one correspondence with one serration 901, and the air outlet path of the sub-channel 601 is located on the tip axis of the serration 901. When the high-speed air flow flows out from the sub-channel 601, due to its direction and position being precisely aligned with the tip of the serration 901, the air flow will concentrate near the tip of the serration 901 and interact with the mainstream air flow at the trailing edge 3, thereby more effectively changing the flow state of the air flow, causing the high-speed air flow of the outlet hole 6 to contact and collide with the air flow at the trailing edge 3, so that the boundary layer of the airfoil trailing edge 3 detaches in advance.

[0064] In this embodiment, multiple sub-channels 601 correspond one-to-one with multiple sawteeth 901. Along the entire width direction of the trailing edge 3 of the blade, each sawtooth 901 can be evenly impacted by the air flow flowing out of the sub-channel 601, making the air flow disturbance at the trailing edge 3 more uniform. This enables the air flow impact force to be evenly distributed on multiple sawteeth 901 at the trailing edge 3, avoiding the over-concentration of the air flow impact force in a single area due to a single outlet hole 6, thereby reducing the blade damage that may be caused by excessive local stress. The high-speed air flow flowing out of the sub-channel 601 contacts and collides with the air flow at the trailing edge 3 at the tip of the sawtooth 901, prompting the boundary layer to detach in advance at the positions of multiple sawteeth 901. Through the detachment of the boundary layer at multiple points, the air flow state at the trailing edge 3 is further changed, reducing the interaction noise between the boundary layer and the trailing edge 3. Moreover, after the air flows out of multiple sub-channels 601 and mixes with the air flow at the trailing edge 3, a more complex turbulent structure is formed. This complex turbulence can accelerate the conversion of the kinetic energy in the air flow into heat energy, further reducing the kinetic energy of the air flow and the impact and collision of the air flow at the trailing edge 3. In addition, if one sub-channel 601 is blocked, the other sub-channels 601 can still normally discharge the air flow, and continue to reduce the noise at the trailing edge 3 through the corresponding sawteeth 901, ensuring that the overall performance of the noise reduction system is not severely affected. The corresponding setting of multiple sub-channels 601 and multiple sawteeth 901 provides a redundant design. Even if the performance of a certain sub-channel 601 or sawtooth 901 decreases due to wear or damage, the other sub-channels 601 and sawteeth 901 can still continue to play the role of noise reduction. In other embodiments, different sub-channels 601 can be optimized according to the air flow distribution and noise characteristics at the trailing edge 3 to adapt to different working conditions. This flexibility enables the blade to maintain a good noise reduction effect under various operating conditions.

[0065] Referring to Figure 6 As shown, it is the velocity vector diagram of the airfoil section. It can be clearly seen that the air flow passes through the internal airfoil and flows to the trailing edge 3 of the blade. For the outer airfoil surface, it can be found that the air flow flows stably along the suction surface 2 of the blade. When passing through the position of the outlet hole 6, the air flow streamline changes significantly, and the attached air flow on the blade surface starts to be chaotic and ends the attached flow on the surface. This also shows that the blade outlet hole 6 has the function of causing the boundary layer on the blade surface to detach in advance.

[0066] Referring to Figures 1 to 9 As shown, taking the width direction of the blade body 10 as the projection plane, the maximum width of the sawtooth 901 is w, the length of the sawtooth 901 is L, and the length L is specifically the vertical distance from the root to the tip of the sawtooth 901. The chord length of the airfoil of the blade body 10 is c, and the value range of the maximum width w is 1.3% - 2.8% of the chord length c of the airfoil, and the value range of the length L is 4.2% - 6.1% of the chord length c of the airfoil.

[0067] In this embodiment, since the blade body 10 of this embodiment has a double-layer airfoil structure, the airfoil chord length of this embodiment is the airfoil chord length of the outer airfoil 802. The value ranges of the maximum width w and the length L are limited. Under this parameter range, the blade body 10 structure has high aerodynamic performance and noise performance, and at the same time, it will not cause excessive air flow separation or generate new strong noise sources due to too large size. By limiting the size of the serrations 901 within a reasonable range, the best balance can be achieved between the noise reduction performance and the aerodynamic performance of the blade. This enables the blade to maintain good working efficiency while meeting the noise requirements, improving the comprehensive performance of the product. In addition, the airfoil chord length is a common parameter in airfoil design. The size of the serration structure 9 is adapted to the airfoil chord length of the blade. The chord length is a basic scale parameter of the blade. Limiting the maximum width and length of the serrations 901 to a proportion of the chord length can ensure that the serration structure 9 plays an appropriate role in the overall scale of the blade. Taking the airfoil chord length as the selection reference can enhance the versatility of this structure and facilitate its application on other airfoils. For blades of different sizes, as long as the serration structure 9 is designed according to this proportion range, it can be ensured that the serrations 901 have similar effects in air flow control and noise reduction. Whether the blade is large or small, an effective noise reduction function can be obtained through this proportional relationship.

[0068] Combined with reference to Figures 1 to 9 As shown, the serration structure 9 is integrally formed with the blade body 10. Taking the longitudinal section of the blade body 10 as the projection plane, in the air flow direction, the extension length of the serration structure 9 is 10% of the airfoil chord length of the blade body 10.

[0069] Specifically, the structural form of the serration structure 9 causes the air flow on the blade surface to concentrate on passing through the tooth surface rather than the gap. Substantially, the blade structure includes two parts: the blade body 10 and the serration structure 9. The serration structure 9 is integrally formed with the blade body 10. Although this embodiment is provided with the serration structure 9, the serration structure 9 is processed on the original size of the blade body 10. For example, the trailing edge 3 is cut to form the serration structure 9, which will not change the maximum size of the blade body 10 nor extend the trailing edge 3 of the blade. Figures 1 to 3 It is only a partial view intercepted for the convenience of showing the relative position of the air outlet and the trailing edge 3 of the blade serrations 901. In the actual application process, the serration structure 9 is integrally formed with the blade body 10.

[0070] In this embodiment, the serrated structure 9 is integrally formed with the blade body 10, avoiding the problem of weak joints that may be caused by additional connecting components. The entire blade structure is a single entity, having a relatively high structural strength and being able to better withstand various loads under the action of air flow. The integrally formed serrated structure 9 is more stable in terms of air flow control. Since the serrated structure 9 and the blade body 10 are a single entity, the position and shape of the serrations 901 will not change due to loosening or displacement at the joints, thus ensuring the stability and consistency of the noise reduction effect. The extended length of the serrated structure 9 is 10% of the chord length of the airfoil of the blade body 10. This ratio is optimized. Within this length range, the serrated structure 9 can generate appropriate disturbances to the air flow, causing the boundary layer to shed in advance, achieving the effect of reducing the noise at the trailing edge 3. In addition, the processing of the serrated structure 9 is carried out at the trailing edge 3 of the blade body 10, which will not have a significant impact on 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 size of the serrated structure 9 is relatively small and is optimized, and will not have an obvious negative impact on the aerodynamic performance.

[0071] It should be noted that the extended length of the serrated structure 9 and the length L are not the same parameter. The extended length of the serrated structure 9 is greater than the length L. The extended length of the serrated structure 9 refers to the inclined surface of the serrations 901.

[0072] As a 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 arranged above the triangular serrations 901 to enhance the effect of contact and collision. The shape of the outlet hole 6 is not limited. The width of the sub-channel 601 should be 50% ± 5% of the maximum width w of the serrations 901. The air outlet path of the outlet hole 6 is on the same straight line as the tooth surface of the serrations 901. For example, the position of the air guide hole should be designed at a position 1% - 3% of the chord length c of the airfoil from the root of the serrations 901. If the chord length of the airfoil is 100 mm, the length L of the serrations 901 should be 4.2% - 6.1% * C. If the length of the serrations 901 is 6% C, the projected position of the root of the serrations 901 is at 94 mm, and the corresponding position of the air outlet hole is set between 91 - 93 mm of the projected position.

[0073] An axial flow fan blade includes a plurality of blade structures, and the blade structure is the above-mentioned blade structure.

[0074] Specifically, the axial flow fan blade includes a hub and a plurality of blade structures, and the plurality of blade structures are circumferentially spaced apart along the hub. When the motor drives the hub to rotate, driving the blades to rotate around the axis, the leading edge 1 of the blade cuts into the air, and an air flow forms a pressure difference on the blade surface (low pressure on the upper surface, high pressure on the lower surface), generating lift.

[0075] In this embodiment, each blade structure adopts the above noise reduction design, including the inlet hole 5, the sound absorption cavity 7, the outlet hole 6, the serrated structure 9, etc. When the axial flow fan blade rotates, the air flow passes through the blade surface. The inlet hole 5 guides part of the air flow into the sound absorption cavity 7, reducing the impact noise of the air flow on the leading edge 1 and the suction surface 2 of the blade. The serrated structure 9 further optimizes the air flow at the trailing edge 3, causing the boundary layer to shed in advance and reducing the noise at the trailing edge 3. This all-round noise reduction design from the air flow source to the outlet of the trailing edge 3 significantly reduces the noise during the operation of the axial flow fan blade. The inlet hole 5, the sound absorption cavity 7, the outlet hole 6 and the serrated structure 9 together constitute a multi-stage noise reduction system. The air flow is guided into the sound absorption cavity 7 when entering the leading edge 1 of the blade, flows out from the outlet hole 6 after being processed by the sound absorption cavity 7, and finally undergoes further optimization by the serrated structure 9. This multi-stage synergistic effect can effectively reduce the noise in different frequency ranges, enabling the axial flow fan blade to operate with low noise under various working conditions.

[0076] An axial flow fan includes an axial flow fan blade, and the axial flow fan blade is the above-mentioned axial flow fan blade.

[0077] In this embodiment, the axial flow fan further includes a motor, and the motor drives the axial flow fan blade to rotate. Each blade of the axial flow fan blade adopts a multi-stage noise reduction design, including the inlet hole 5, the sound absorption cavity 7, the outlet hole 6 and the serrated structure 9. These settings can effectively reduce the noise generated when the air flow flows on the blade surface. When the motor drives the axial flow fan blade to rotate, the air flow enters the sound absorption cavity 7 through the inlet hole 5 at the leading edge 1 of the blade, flows out from the outlet hole 6 after being processed by the sound absorption cavity 7, and finally undergoes optimization by the serrated structure 9, reducing the noise at the trailing edge 3. The design of the serrated structure 9 and the sound absorption cavity 7 can reduce the impact and collision of the air flow 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 all-round noise reduction measure significantly reduces the noise during the operation of the axial flow fan, providing a quieter working environment for users.

[0078] An air conditioner includes an axial flow fan, and the axial flow fan is the above-mentioned axial flow fan.

[0079] It is easy for those skilled in the art to understand that, on the premise of no conflict, the above-mentioned advantageous methods can be freely combined and superimposed.

[0080] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention. The above is only the preferred implementation manner of the present invention. It should be noted that for those of ordinary skill in the art in this technical field, several improvements and variations can be made without departing from the technical principle of the present invention, and these improvements and variations should also be regarded as within the protection scope of the present invention.

Claims

1. A blade structure, characterized in that, Comprising: 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) that are connected in sequence from head to tail. The pressure surface (4) and the suction surface (2) extend between the leading edge (1) and the trailing edge (3) respectively. In the airflow direction, an inlet hole (5) is provided on the leading edge (1) or the pressure surface (4), and an outlet hole (6) is provided on the trailing edge (3) or the suction surface (2); A sound-absorbing cavity (7) is provided inside the blade body (10). The inlet hole (5) and the outlet hole (6) are respectively communicated with the sound-absorbing cavity (7). The inlet hole (5) guides the airflow into the sound-absorbing cavity (7), and the outlet hole (6) guides the airflow in the sound-absorbing cavity (7) out of the blade body (10).

2. The blade structure according to claim 1, wherein The inlet hole (5) is provided on the suction surface (2), and the inlet hole (5) is close to the leading edge (1); the outlet hole (6) is provided on the pressure surface (4), and the outlet hole (6) is close to the trailing edge (3).

3. The blade structure according to claim 1, wherein, The blade body (10) is of 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 sound-absorbing cavity (7), and the inlet hole (5) guides the airflow from the outer airfoil (802) into the sound-absorbing cavity (7).

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

5. The blade structure according to any one of claims 1 to 4, characterized in that, It further includes a serrated structure (9). The outlet hole (6) is provided on the suction surface (2), and the outlet hole (6) is close to the trailing edge (3). The trailing 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, wherein, Taking the width direction of the blade body (10) as the projection plane, the serrated structure (9) includes a plurality of serrations (901). The plurality of serrations (901) are arranged along the width direction of the trailing edge (3), and the tooth width of the serration (901) is tapered in a direction away from the trailing edge (3).

7. The blade structure according to claim 6, wherein Taking the width direction of the blade body (10) as the projection plane, the outlet hole (6) includes a plurality of sub-channels (601). The plurality of sub-channels (601) are all communicated with the sound-absorbing cavity (7). The plurality of sub-channels (601) are arranged in one-to-one correspondence with the plurality of 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, wherein Taking 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, wherein, The sawtooth structure (9) is integrally formed with the blade body (10). Taking the longitudinal section of the blade body (10) as the projection plane, in the air flow direction, the extension length of the sawtooth structure (9) 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 an axial flow impeller, characterized in that, The axial flow fan blade is the axial flow fan blade according to claim 10.

12. An air conditioner, comprising an axial flow fan, characterized in that, The axial flow fan is the axial flow fan according to claim 11.

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