Cross-flow fan blade and cross-flow fan

Abstract

The present application relates to the technical field of cross-flow fan, in particular to a cross-flow fan blade and a cross-flow fan blade, the cross-flow fan blade comprises a leading edge and a trailing edge, and the suction surface of the trailing edge is provided with a plurality of sawteeth which are unevenly distributed, the cross-flow fan blade provided by the present application can effectively reduce the surface layer pressure pulsation of the blade suction surface, weaken the airflow separation of the pressure surface of the trailing edge, and improve the BPF noise of the blade, in addition, the sawteeth are unevenly distributed, the periodic time intervals of the airflow cut by each sawtooth are not equal, and the composition and frequency of the small vortex noise generated are not completely the same, therefore, the problem of resonance peak value caused by the superposition of the noise with the same composition and frequency can be effectively avoided, and the blade frequency noise is further reduced.

Description

Technical Field

[0001] This invention relates to the field of cross-flow fan technology, specifically to a cross-flow fan blade and a cross-flow fan impeller. Background Technology

[0002] Cross-flow fan blades are commonly used in wall-mounted split air conditioning units. The blade surface design of most cross-flow fan blades is a smooth parabola or a smoothly transitioned curve. When airflow passes over the blades, a boundary layer forms on the blade surface. During high-speed operation, especially at the suction side at the trailing edge, severe airflow separation occurs, leading to a thickening of the boundary layer at the trailing edge and the formation of large-area vortices. Furthermore, at the blade trailing edge, the fluid boundary layers from the suction and pressure sides merge to form a wake region. In this region, the pressure and velocity gradients of the airflow are significantly lower than in the mainstream area of ​​the blade surface. Therefore, when the fan rotor is operating, the airflow at the inlet of the internal flow channel at the blade trailing edge exhibits significant instability. This non-uniform airflow and vortex shedding periodically interfere with the surrounding air medium, generating pressure pulsations and creating discrete frequency noise.

[0003] Chinese patent CN208203655 discloses a cross-flow fan blade with serrations on its pressure surface. The tooth width of the serrations is 5% to 10% of the blade's centerline arc length, and the serrations are positioned between 50% and 90% of the blade's centerline arc length. While the serrations on the pressure surface of this cross-flow fan blade can reduce noise to some extent, the surface pressure pulsation on the suction surface of the blade is relatively high. Furthermore, the equidistant tooth spacing of the serrations causes resonance problems when noise of the same composition and frequency is superimposed on the separating vortex, resulting in relatively severe noise from the fan blade. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the problems of high surface pressure pulsation on the suction surface of the cross-flow fan blade in the prior art, and the superposition of noise of the same composition and frequency when the equidistant saw teeth act on the separation vortex, thereby producing resonance. The present invention provides a cross-flow fan blade and cross-flow fan blade that can effectively reduce surface pressure pulsation on the suction surface of the blade and avoid the problem of noise of the same composition and frequency superimposed and producing resonance caused by the equidistant saw teeth acting on the separation vortex, thereby improving the BPF noise of the blade.

[0005] To address the aforementioned problems, in a first aspect, the present invention provides a cross-flow fan blade, the blade comprising a leading edge and a trailing edge, wherein the suction surface of the trailing edge is provided with a plurality of unequally spaced serrations.

[0006] Optionally, the tooth pitch of the plurality of saw teeth is set by adjusting the sine frequency.

[0007] Optionally, the suction surface of the blade near the trailing edge is provided with a plurality of oblique grooves to form the serrations, the serrations being oblique teeth with the tips inclined toward the trailing edge.

[0008] Optionally, the blade has a pressure surface and a suction surface arranged opposite to each other, and the diameter of the largest inscribed circle between the pressure surface and the suction surface is set to D. max If the tooth depth of the helical tooth groove is H, then H must satisfy the following condition:

[0009] 1 / 10D max ≤H≤1 / 2D max .

[0010] Optionally, an offset arc line L1 is formed by equidistant offset of the arc surface containing the suction surface to the pressure surface, wherein the offset distance of the offset arc line L1 is H; taking the center O of the base circle of the pressure surface as the base point, setting the total span angle of the blade as α, and the offset arc line and the trailing edge as F, drawing a line L2 connecting point F through point O and using this line L2 as the lower boundary line of the serrated area; taking O as the base point and L2 as the baseline, drawing an angle line L3 in the direction of the forward edge, and using this angle line L3 as the upper boundary line of the serrated area;

[0011] The angle between L2 and L3 is the span angle θ of the sawtooth region, and θ must satisfy the following condition: 1 / 4α≤θ≤1 / 2α.

[0012] Optionally, taking O as the base point and L3 as the upper boundary line of the sawtooth region as the starting edge, n sawtooths are sequentially set from the leading edge to the trailing edge according to a preset sinusoidal frequency adjustment formula, which is as follows: θ i =θ0×i+a×sin(S×θ0×i×π / θ); where: i is the sawtooth number, i∈[1,n]; θ0 is the angle between two adjacent sawtooths when n sawtooths are arranged at equal intervals in the sawtooth region; a is the amplitude of the sine adjustment; S is the number of sine adjustments; θ i Let be the distribution angle of the i-th sawtooth from its starting edge to its tip.

[0013] Optionally, the spacing angle between two adjacent saw teeth can be set to Δθ. i Then Δθ i Satisfying: Δθ1=θ1, Δθ i =θ i -θ i-1 (2≤i≤n); set in each Δθ i Within the range, the intersection point A of the boundary line near the tail edge and the suction surface arc is the tip of each sawtooth; the tip A of the i-th sawtooth i With the (i+1)th tooth tip A i+1 The spacing is the sawtooth pitch λ. i The λ i The size of Δθi They are positively correlated.

[0014] Optionally, each Δθ i Within the range, the root point m of each saw tooth i All fall on the offset circular arc L1, with the set point m. i O, A i The angle β formed i =∠m i OA i ,β i Satisfying 0≤β i ≤Δθ i .

[0015] Optionally, the tip A of the i-th sawtooth i With tooth root point m i The edge formed by the connecting lines is the short side of the helical tooth, and i satisfies i∈[1,n-1]; the tip A of the i-th sawtooth. i The root m of the (i-1)th saw tooth i-1 The edge formed by the connecting lines is the long edge of the oblique tooth, and i satisfies i∈[2,n].

[0016] In a second aspect, the present invention provides a cross-flow fan blade, including a central impeller, the central impeller including an annular disc and a plurality of blades evenly spaced around the annular disc, the blades being cross-flow fan blades as described in any of the above embodiments.

[0017] The present invention has the following advantages:

[0018] This invention utilizes a serrated structure on the suction surface of the blade's trailing edge. Firstly, the pressure difference created by the height difference between the serrations and the blade surface effectively suppresses airflow separation on the suction surface near the trailing edge, enhancing the stability of the blade's wake airflow. Secondly, the serrated structure cuts through vortices caused by the shedding of large-scale vortices resulting from airflow separation, decomposing these vortices into smaller ones, thereby reducing blade discrete noise. This effectively improves the airflow separation phenomenon on the suction surface of traditional cross-flow wind turbines, weakens suction surface pressure pulsation, and thus improves blade BPF noise. Furthermore, the serrations are distributed with unequal tooth pitch, and the periodic time intervals for each serration cutting the airflow are not equal. The resulting small vortex noise components and frequencies are also not entirely the same. Therefore, it effectively avoids the problem of resonance peaks caused by the superposition of noise with the same components and frequencies, further improving the blade's noise reduction effect. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 A schematic diagram of the original leaf shape (without serrations) is shown;

[0021] Figure 2 A schematic diagram of the improved blade with unequally spaced serrations in the embodiment is shown.

[0022] Figure 3 A schematic diagram of the serrated leaf shape parameters in the embodiment is shown;

[0023] Figure 4 A partially enlarged view of the structural parameters of the serrated leaf-shaped portion in the embodiment is shown;

[0024] Figure 5 A cross-sectional schematic diagram of the impeller and blades of the cross-flow fan blades in the embodiment is shown;

[0025] Figure 6 A schematic diagram of the structure of the impeller and blades of the cross-flow fan blades in the embodiment is shown;

[0026] Figure 7 The diagram shows the airflow distribution on the surface of the original blade shape;

[0027] Figure 8 The diagram shows the airflow distribution on the blade surface of the improved unequal-pitch serrations in the embodiment;

[0028] Figure 9 The noise cloud diagram of the original blade cross-flow fan is shown;

[0029] Figure 10 The noise cloud map of the airflow distribution on the blade surface of the improved unequal-pitch serrated blade in the embodiment is shown;

[0030] Explanation of reference numerals in the attached figures:

[0031] 1. Blade; 11. Pressure surface; 12. Suction surface; 13. Leading edge; 14. Trailing edge; 10. Serration; 101. Long side of helical tooth; 102. Short side of helical tooth; 2. Annular disc. Detailed Implementation

[0032] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and 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. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0034] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0035] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0036] Example 1

[0037] like Figures 1 to 10 As shown, this embodiment provides a cross-flow fan blade 1, which includes a leading edge 13 and a trailing edge 14. The suction surface 12 of the trailing edge 14 is provided with a plurality of unequally spaced serrations 10. The blade 1 has a pressure surface 11 and a suction surface 12 distributed on both sides of the leading edge 13 and the trailing edge 14, wherein the surface of the pressure surface 11 is set as a smooth arc surface, and the suction surface 12 is provided with a plurality of unequally spaced serrations 10 near the trailing edge 14.

[0038] By incorporating a serrated structure on the suction surface 12 of the trailing edge 14 of blade 1, the pressure difference created by the height difference between the serrations 10 and the blade surface can effectively suppress airflow separation on the suction surface 12 near the trailing edge 14, enhancing the stability of the blade 1's wake airflow. Furthermore, the serrated structure can cut through vortices caused by the shedding of large-scale vortices resulting from airflow separation, decomposing these vortices into smaller vortices, thereby reducing the discrete noise of blade 1. This effectively improves the airflow separation phenomenon on the suction surface 12 during the operation of traditional cross-flow wind turbines, reduces pressure pulsation on the suction surface 12, and thus improves the blade's BPF noise. In addition, the serrations 10 are distributed with unequal tooth pitch, and the periodic time intervals for each serration 10 cutting the airflow are not equal. The components and frequencies of the generated small vortex noise are also not entirely the same. Therefore, the problem of resonance peaks caused by the superposition of noise with the same components and frequencies can be effectively avoided, further improving the noise reduction effect of blade 1.

[0039] In some preferred embodiments of this example, the tooth pitch of the plurality of saw teeth 10 is set by adjusting the sine frequency. By adjusting the tooth pitch of the saw teeth 10 by adjusting the sine frequency, the unequal distribution can be formed into a distribution that can be specifically adjusted, which facilitates the optimization of the specific parameters of the unequal distribution in subsequent research and development testing, thereby obtaining the optimal solution.

[0040] In some preferred embodiments of this example, the suction surface 12 of the blade 1 is provided with a plurality of oblique grooves near the trailing edge 14 to form the serrations 10, wherein the serrations 10 are oblique teeth with the tips inclined toward the trailing edge 14.

[0041] In the above embodiment, a serrated groove is provided on the suction surface 12 of the blade 1 near the trailing edge 14 to form an inclined serration 10, the tips of which are inclined towards the trailing edge 14. Since airflow separation mainly occurs in the lower half of the blade near the trailing edge 14, and the closer to the trailing edge 14, the more severe the airflow separation, the serration area is set near the blade root. By utilizing the pressure difference between the inside of the groove and the blade surface, the airflow separation phenomenon can be effectively alleviated. Furthermore, the use of serrations with backward-inclined tips as serrations 10 further increases fluid adhesion at the trailing edge 14 and weakens airflow separation, thereby reducing flow loss.

[0042] Combination Figure 7 and Figure 8 As shown in the figure, the dark area on the vertical axis represents the low-speed, low-energy fluid region, which is mainly caused by the shedding of the wake vortex. This will reduce the aerodynamic efficiency of blade 1 and increase BPF noise. The low-energy region of the oblique toothed blade 1 with sinusoidal frequency adjustable tooth pitch provided in this embodiment is significantly delayed, and the area of ​​the region is significantly reduced compared with the original blade shape of blade 1, which can achieve the purpose of improving efficiency and reducing noise.

[0043] Table 1 Comparison of air volume for different blade shapes

[0044] Original leaf shape 397.6 Straight teeth 375.8 Backward tilting teeth 394.3

[0045] Since the airflow tends to separate from the blade tip to the blade root on the suction surface 12, the backward-inclined teeth used in this embodiment, which are inclined towards the blade root, better match the airflow direction, thereby effectively reducing airflow separation. The backward-inclined serrated blade shape can disperse vortices and increase the adhesion of small airflow streams, thus delaying airflow separation. Furthermore, combined with... Figure 1 , Figure 2 , Figure 7 , Figure 8 As can be seen from Table 1 above, in this embodiment, the airflow is almost unaffected by the aforementioned backward-inclined teeth compared to the original blade shape, while the airflow is as high as 20m³ compared to the straight-tooth blade 1. 3 / h can effectively improve airflow separation.

[0046] In some preferred embodiments of this example, such as Figure 2 and Figure 3 As shown, the diameter of the largest inscribed circle between the pressure surface 11 and the suction surface 12 is set to D. max If the tooth depth of the helical tooth groove is H, then H must satisfy the following condition: 1 / 10D max ≤H≤1 / 2D max .

[0047] In the above embodiment, the design of the oblique toothed airfoil scheme mainly controls the pressure difference at the trailing edge 14 of the blade surface to suppress airflow separation at the blade surface, thereby reducing the blade's BPF noise. If the tooth depth of the oblique tooth groove is too small, the pressure difference amplitude at the blade surface is low, and the airflow improvement effect is not obvious. If the tooth depth is too large, it will cause a large flow loss and reduce the original aerodynamic performance of the airfoil. Therefore, this embodiment conducted an optimization experiment on the numerical range of the tooth depth. The experiment found that the tooth depth is 1 / 10D. max ~1 / 2D max The optimal range is within which airflow separation can be effectively alleviated without causing significant flow loss or reducing the original aerodynamic performance.

[0048] In some preferred embodiments of this example, such as Figure 2As shown, an offset arc line L1 is formed by equidistant offset of the arc surface 12 onto the pressure surface 11, where the offset distance of the offset arc line L1 is H. Taking the center O of the base circle of the pressure surface 11 as the base point, the total span angle of the blade 1 is set as α, and the offset arc line L1 and the trailing edge 14 are F. A line L2 is drawn connecting point O and point F, and this line L2 is used as the lower boundary line of the serrated area. Taking O as the base point and L2 as the baseline, an angle line L3 is drawn in the direction of the forward edge 13, and this angle line L3 is used as the upper boundary line of the serrated area. The angle formed by L2 and L3 is the span angle θ of the serrated area, and θ must satisfy the following condition: 1 / 4α≤θ≤1 / 2α.

[0049] Since airflow separation mainly occurs in the lower half of the blade near the trailing edge 14, and the separation is more severe closer to the trailing edge 14, the airflow adheres more strongly to the blade surface closer to the leading edge 13 beyond the blade, which is the main aerodynamic work area of ​​the blade 1. If the serrated area is too small, it will not significantly improve the airflow adhesion on the suction surface 12 and will not achieve noise reduction; if the area is too large, it will damage the high-efficiency area of ​​the original suction surface 12 of the blade 1, affecting the aerodynamic performance of the blade 1 and causing airflow loss. Therefore, this embodiment conducted an optimization experiment on the effective area of ​​the serrated 10. The experiment found that the optimal range for the serrated area is 1 / 4 to 1 / 2 of the span angle of the entire blade 1. This approach will not damage the aerodynamic performance of the blade 1 or cause airflow loss, while effectively improving the airflow adhesion on the suction surface 12 and achieving a good noise reduction effect.

[0050] In some preferred embodiments of this example, such as Figure 2 , Figure 3 , Figure 5 and Figure 6 As shown, with O as the base point and L3 as the upper boundary line of the sawtooth region as the starting edge, n sawtooth teeth 10 are sequentially set from the leading edge 13 to the trailing edge 14 according to a preset sinusoidal frequency adjustment formula. The sinusoidal frequency adjustment formula is as follows: θ i =θ0×i+a×sin(S×θ0×i×π / θ); where: i is the serration number 10, i∈[1,n]; θ0 is the interval angle between two adjacent serrations 10 when n serrations 10 are arranged at equal intervals in the serration region; a is the amplitude of the sine adjustment; S is the number of sine adjustments; θ i Let be the distribution angle of the i-th sawtooth 10 from its starting edge to its tip.

[0051] In the above embodiment, the sawtooth 10 is arranged in an unequal interval manner using sinusoidal adjustment. The range of values ​​for amplitude a and the number of sinusoidal adjustments S is not limited; both amplitude a and the number of sinusoidal adjustments S can be arbitrary values. For example, the number of sinusoidal adjustments S can be understood as the number of peaks and troughs generated during the unequal interval adjustment. The optimal parameters for unequal interval adjustment may change for different blade shapes and wind turbine specifications. The values ​​of amplitude a and the number of sinusoidal adjustments S need to be adjusted according to the actual operating conditions.

[0052] Furthermore, in some preferred embodiments, such as Figure 3 As shown, the upper boundary line L3 of the sawtooth region passes through the center of the largest inscribed circle between the pressure surface 11 and the suction surface 12, and the intersection point of the upper boundary line L3 of the sawtooth region and the arc where the suction surface 12 is located is set as E. Point E is used as the starting point of the long side 101 of the oblique tooth of the first sawtooth 10.

[0053] Furthermore, such as Figure 5 As shown, the spacing angle between two adjacent sawtooth 10 is set to Δθ. i Then Δθ i Satisfying: Δθ1=θ1, Δθ i =θ i -θ i-1 (2≤i≤n); set in each Δθ i Within the range, the intersection point A of the boundary line near the tail edge 14 and the arc of the suction surface 12 is the tip of each sawtooth 10; the tip A of the i-th sawtooth 10 i With the (i+1)th tooth tip A i+1 The spacing is the 10-tooth pitch λ of the sawtooth. i The λ i The size of Δθ i They are positively correlated, i.e., Δθ i The larger the tooth pitch λ between two adjacent saw teeth 10, the larger it is. i The larger Δθ is, the better. i The smaller the pitch, the smaller the tooth spacing between two adjacent saw teeth 10. In this embodiment, θ i Let θ be the distribution angle of the i saw teeth from the starting edge to their tips, and θ i The sine frequency adjustment formula θ i =θ0×i+a×sin(S×θ0×i×π / θ) is calculated, therefore, the tooth pitch λ of sawtooth 10 can be deduced. i and the interval angle Δθ i All of these were determined by adjusting the sinusoidal frequency.

[0054] The above describes and defines the specific distribution of individual teeth and the distribution of adjacent tooth spacing λ in the sawtooth region of this embodiment. This embodiment employs a method of noise reduction using unequally spaced oblique teeth. On one hand, it utilizes the pressure difference formed by the height difference of the oblique tooth grooves to suppress airflow separation near the suction surface 12 of the trailing edge 14, enhancing the stability of the airflow in the blade wake. On the other hand, it uses the sawtooth structure to cut the vortex clusters caused by the shedding of large-scale vortices formed by airflow separation, decomposing the vortices into smaller vortices, thereby reducing the discrete noise of the blade 1. Furthermore, the unequally spaced sinusoidal adjustment of the sawtooth 10 distribution ensures that the periodic time intervals of the sawtooth 10 cutting the airflow are not equal, resulting in different components and frequencies of the generated small vortex noise. This avoids the resonance peak caused by the superposition of noise with the same components and frequencies, further reducing the frequency noise of the blade 1 and improving its noise reduction effect.

[0055] In this embodiment, as Figure 4 As shown, each Δθ i Within the range, the root point m of each saw tooth 10 i All fall on the offset circular arc L1, with the set point m. i O, A i The angle β formed i =∠m i OA i ,β i Satisfying 0≤β i ≤Δθ i .

[0056] Furthermore, the tip A of the i-th sawtooth 10 i With tooth root point m i The edge formed by the connecting lines is the short side 102 of the helical tooth, and i satisfies i∈[1,n-1]; the tip A of the i-th sawtooth 10 i The root m of the (i-1)th serration 10 i-1 The edge formed by the connecting line is the long side 101 of the helical tooth, and i satisfies i∈[2,n].

[0057] The above scheme can be used to adjust the length and tilt angle of the long side 101 and the short side 102 of the helical teeth. The adjustment method of the long side 101 and the short side 102 of the helical teeth is limited, but the specific value range of the length of the long side 101 and the short side 102 of the helical teeth is not limited. Within the adjustment range, all values ​​of the long side 101 and the short side 102 of the helical teeth can achieve the preset noise reduction effect. This embodiment does not limit this.

[0058] For example, in the schematic diagram of the wind turbine in this embodiment, the number of helical tooth segments n = 5, the span angle θ of the sawtooth region θ = 32.5°, the number of sinusoidal adjustments S = 2, and the adjustment amplitude a = 1. Then, according to the sinusoidal frequency adjustment formula: θ i=θ0×i+a×sin(S×θ0×i×π / θ), the calculated sawtooth non-uniform distribution parameters are as follows:

[0059] Table 2. Distribution parameters of unequal-distance sawtooth patterns

[0060] <![CDATA[θ i ]]> 7.45 13.59 18.91 25.05 32.5 <![CDATA[Δθ i ]]> 7.45 6.14 5.32 6.13 7.45

[0061] Combination Figure 9 and Figure 10 The noise contrast cloud map shows the color difference distribution on the vertical axis. Areas with higher whiteness have higher noise values, while areas with lower whiteness have lower noise values. Compared to the original blade shape, the cross-flow fan blade provided in this embodiment, using a slanted toothed blade design in the cross-flow duct, exhibits significantly reduced whiteness and broadband noise levels near the volute tongue and front exhaust grille, and a significant decrease in the noise gradient distribution between blades.

[0062] This embodiment provides comparative test data on the performance of the original blade shape, the uniformly distributed serrated blade shape with θ0 = 6.5°, and the unequally spaced serrated blade shape, as detailed below:

[0063] Table 3 Performance Comparison of Different Leaf Shape Schemes

[0064] Original leaf shape 397.6 59.1 33.2 <![CDATA[θ0=6.5° uniformly distributed锯齿 blade profile]]> 393.7 57.3 29.6 Unequally spaced serrated leaf shape 394.3 56.1 26.5

[0065] As can be seen from Table 3 above, the air volume of the unequally spaced sawtooth blade provided in this embodiment is basically on the same order of magnitude as that of the original blade. In terms of total noise and peak frequency, the sinusoidal unequally spaced sawtooth blade is the optimal solution in terms of noise and sound quality.

[0066] This embodiment provides a cross-flow wind turbine blade 1 with a trailing edge 14 and suction surface 12 having a sawtooth structure. The sawtooth structure is composed of backward-inclined helical teeth, and each sawtooth 10 adopts a cross-flow blade shape with helical tooth pitch λ adjusted by sinusoidal frequency. This effectively solves the resonance problem caused by the superposition of noise of the same component and frequency when the equidistant sawtooth blade acts on the separation vortex, and overcomes the defect of heavy discrete frequency noise in traditional wind turbine blades.

[0067] Example 2

[0068] like Figure 5 and Figure 6 As shown, this embodiment provides a cross-flow fan blade, including a central impeller. The central impeller includes an annular disc 2 and a plurality of blades 1 evenly spaced around the annular disc 2. The blades 1 are the cross-flow fan blades 1 described in any of the embodiments of the above embodiment 1.

[0069] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A cross-flow fan blade, characterized in that, The blade (1) includes a leading edge (13) and a trailing edge (14). The suction surface (12) of the blade (1) near the trailing edge (14) is provided with multiple oblique grooves to form serrations (10). The serrations (10) are oblique teeth with the tooth tips inclined toward the trailing edge (14). The tooth pitch of the multiple serrations (10) is set by adjusting the sine frequency. The blade (1) has a pressure surface (11) and a suction surface (12) arranged opposite to each other. The tooth depth of the oblique tooth groove is H. The circular arc surface where the suction surface (12) is located is offset from the pressure surface (11) by an equidistant offset to form an offset circular arc line L1, wherein the offset distance of the offset circular arc line L1 is H. Taking the center O of the base circle of the pressure surface (11) as the base point, the intersection of the offset arc and the tail edge (14) is F. Draw a line L2 through point O and connect point F, and take this line L2 as the lower boundary line of the sawtooth region. Using O as the base point and L2 as the baseline, draw an angle line L3 in the direction of the front edge (13), and use this angle line L3 as the upper boundary line of the sawtooth region; Using O as the base point and the upper boundary line of the sawtooth region as the starting edge, n sawtooths (10) are sequentially set from the leading edge (13) to the trailing edge (14) according to the preset sinusoidal frequency adjustment formula, which is as follows: ； Where: the angle between L2 and L3 is the span angle θ of the sawtooth region, i is the sawtooth (10) number, i∈[1,n]; θ0 is the interval angle between two adjacent sawtooth (10) when n sawtooth (10) are arranged at equal intervals in the sawtooth region; a is the sine adjustment amplitude; S is the number of sine adjustments; θ i Let be the distribution angle of the i-th sawtooth (10) from the starting edge to its tip.

2. The cross-flow fan blade according to claim 1, characterized in that, The diameter of the largest inscribed circle between the pressure surface (11) and the suction surface (12) is set to D. max Then H must satisfy the following conditions: 1 / 10D max ≤H≤1 / 2D max 。 3. The cross-flow fan blade according to claim 1 or 2, characterized in that, Set the total span angle of the blade (1) to α, and θ must satisfy the following condition: 1 / 4α≤θ≤1 / 2α.

4. The cross-flow fan blade according to claim 1 or 2, characterized in that, Set the interval angle between two adjacent sawtooths (10) to Δ. θ i , then Δ θ i Satisfy: Δ θ 1= θ 1, Δ θ i = θ i - θ i-1 (2≤i≤n); Set in each Δ θ i Within the range, the intersection point A of the boundary line near the tail edge (14) and the arc of the suction surface (12) is the tip of each sawtooth (10); The tip A of the i-th sawtooth (10) i With the (i+1)th tooth tip A i+1 The spacing is the tooth pitch λ of the sawtooth (10). i The λ i Size and Δ θ i They are positively correlated.

5. The cross-flow fan blade according to claim 4, characterized in that, Each Δ θ i Within the range, the root point m of each saw tooth (10) i All fall on the offset circular arc L1, with the set point m. i O, A i The angle β formed i =∠m i OA i ,β i Satisfying 0≤β i ≤Δ θ i .

6. The cross-flow fan blade according to claim 4, characterized in that, The tip A of the i-th sawtooth (10) i With tooth root point m i The edge formed by the connecting line is the short side of the helical tooth (102), and i satisfies i∈[1,n-1]; The tip A of the i-th sawtooth (10) i The root m of the (i-1)th sawtooth (10) i-1 The edge formed by the connecting line is the long edge of the helical tooth (101), and i satisfies i∈[2,n].

7. A cross-flow fan blade, characterized in that, The wind turbine includes a central impeller, which includes an annular disc (2) and a plurality of blades (1) evenly spaced around the annular disc (2), wherein the blades (1) are cross-flow wind turbine blades (1) as described in any one of claims 1-6.

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