Blades and axial flow fans using them

Abstract

This application discloses a blade, comprising: a pressure surface and a suction surface, a blade tip, a blade root, a leading edge, and a trailing edge. The blade includes a wave-like portion, comprising at least two peaks and at least two troughs. The at least two peaks and at least two troughs are staggered in the radial direction of the blade, and each peak and each trough extends circumferentially along the blade. The blade of this application and the axial flow fan using this blade increase the blade's strength by providing at least two consecutive pairs of peaks and troughs in the radial direction of the blade, preventing the blade from breaking at the blade root under excessive power. This application controls the position and camber of the peaks and troughs, thereby effectively controlling airflow separation on the blade surface without affecting the working efficiency of the axial flow fan. Simultaneously, due to the increased peaks and troughs, the surface area of ​​the blade increases, the working area increases, and the working efficiency of the axial flow fan is actually improved.

Description

Technical Field

[0001] This application relates to the field of rotating machinery such as fans, pumps and compressors, and more specifically to a blade and an axial flow fan using the blade. Background Technology

[0002] Generally, rotating machinery such as fans consists of a number of blades arranged circumferentially at intervals. Each blade is formed by several airfoil sections extending longitudinally along their leading and trailing edges. The blade has a leading edge for inflowing media and a trailing edge for outflowing media, as well as a concave pressure surface and a convex suction surface. The part of the blade near the hub is called the blade root, and the part with the largest diameter is called the blade tip. Existing blades, when rotating, are subjected to centrifugal force, resulting in insufficient blade strength and easy deformation at the blade tip. Summary of the Invention

[0003] To address the above problems, at least one objective of this application in a first aspect is to provide a blade comprising: a pressure surface and a suction surface, the pressure surface and the suction surface forming two opposing surfaces of the blade; a blade tip, a blade root, a leading edge, and a trailing edge, the blade tip, the blade root, the leading edge, and the trailing edge defining the outer edges of the pressure surface and the suction surface, wherein the leading edge and the trailing edge extend from the blade tip to the blade root, respectively; wherein the blade includes a wave-like portion comprising at least two peaks and at least two troughs, the troughs being formed by at least one recessed portion recessed in a direction from the pressure surface to the suction surface, and the peaks being formed by at least one arched portion arched in a direction from the suction surface to the pressure surface, the at least one recessed portion and the at least one arched portion being connected to form the wave-like portion; wherein the at least two peaks and the at least two troughs are staggered in the radial direction of the blade, and each peak and each trough extends circumferentially along the blade.

[0004] According to the first aspect above, the blade is capable of rotating about a rotation axis perpendicular to a normal plane; each wave crest forms a wave crest arc on the projection of the blade onto the normal plane; and each wave trough forms a wave trough arc on the projection of the blade onto the normal plane; wherein each wave crest arc and each wave trough arc are concentric arcs centered on the projection center of the rotation axis.

[0005] According to the first aspect above, in the radial direction from the leaf tip to the leaf root, the at least two peaks and the at least two troughs sequentially include a first trough, a first peak, a second trough, and a second peak, wherein the first trough is closest to the leaf tip.

[0006] According to the first aspect above, the blade has a radial height, which is the distance between the blade root and the blade tip on the projection of the blade onto the normal plane of the blade; wherein, the distance between the first trough and the blade root is (0.9~0.95)L; the distance between the first peak and the blade root is (0.7~0.8)L; the distance between the second trough and the blade root is (0.45~0.55)L; and the distance between the second peak and the blade root is (0.2~0.3)L.

[0007] According to the first aspect above, the distance from the first trough to the leaf root is 0.9375L; the distance from the first peak to the leaf root is 0.75L; the distance from the second trough to the leaf root is 0.5L; and the distance from the second peak to the leaf root is 0.25L.

[0008] According to the first aspect above, on any circumferential cross-section of the blade, the acute circumferential angle between the trailing edge and the leading edge forms a circumferential wrap angle; wherein, on the circumferential cross-section where the first trough is located, the acute circumferential angle between the trailing edge and the leading edge forms a circumferential wrap angle, and the acute circumferential angle of the first trough is 0.6θ1; on the circumferential cross-section where the first crest is located, the acute circumferential angle between the trailing edge and the leading edge forms a circumferential wrap angle, and the acute circumferential angle of the first crest is 0.9θ2; on the circumferential cross-section where the second trough is located, the acute circumferential angle between the trailing edge and the leading edge forms a circumferential wrap angle, and the acute circumferential angle of the second trough is 0.7θ3; on the circumferential cross-section where the second crest is located, the acute circumferential angle between the trailing edge and the leading edge forms a circumferential wrap angle, and the acute circumferential angle of the second crest is 0.8θ4.

[0009] According to the first aspect above, any point on the blade has a circumferential position angle, and on the circumferential cross section of the point, the circumferential position angle is the acute circumferential angle between the point and the leading edge; the circumferential position angle of the starting position of the first trough is θ1, and the circumferential position angle of the ending position of the first trough is 0.4θ1; the circumferential position angle of the starting position of the first crest is θ2, and the circumferential position angle of the ending position of the first crest is 0.1θ2; the circumferential position angle of the starting position of the second trough is θ3, and the circumferential position angle of the ending position of the second trough is 0.3θ3; the circumferential position angle of the starting position of the second crest is θ4, and the circumferential position angle of the ending position of the second crest is 0.2θ4.

[0010] According to the first aspect above, the blade has a blade radius, which is the distance between the blade tip and the axis of rotation; on each radial section of the blade, the maximum arch height of the first trough is (0.6~4)%R; the maximum arch height of the first crest is (1.4~12)%R; the maximum arch height of the second trough is (0.6~4)%R; and the maximum arch height of the second crest is (0.6~3)%R.

[0011] According to the first aspect above, the peaks and troughs are rounded.

[0012] At least one object of the second aspect of this application is to provide an axial flow impeller comprising: a hub having a rotation axis about which the hub is rotatable; and at least two blades according to any one of the first aspects, the at least two blades being arranged on the outer circumferential surface of the hub. Attached Figure Description

[0013] Figure 1 This is a perspective structural diagram of one embodiment of the axial flow fan of this application;

[0014] Figure 2A for Figure 1 A three-dimensional structural diagram of the hub and one blade in the axial flow fan shown.

[0015] Figure 2B for Figure 2A The projection of the blade onto its normal plane is shown.

[0016] Figure 2C for Figure 2A A radial cross-sectional view of the blade is shown.

[0017] Figure 3A and Figure 3B A comparison diagram of blade deformation between the axial flow fan of this application and the prior art;

[0018] Figure 4A and Figure 4B This is a comparison diagram of blade stress between the axial flow fan of this application and the prior art. Detailed Implementation

[0019] Various specific embodiments of this application will now be described with reference to the accompanying drawings, which form part of this specification. It should be understood that although directional terms such as "front," "rear," "upper," "lower," "left," "right," "top," and "bottom" are used in this application to describe various exemplary structural parts and elements, their use is merely for illustrative purposes and is based on the exemplary orientations shown in the accompanying drawings. Since the embodiments disclosed in this application can be arranged in different orientations, these directional terms are for illustrative purposes only and should not be considered as limiting.

[0020] Figure 1 This is a top-down perspective structural view of one embodiment of the axial flow fan 100 of this application. Figure 1 As shown, the axial flow fan 100 includes an annular guide ring 101, a hub 110, and three blades 102, which are disposed within the annular guide ring 101. The hub 110 has a rotation axis x, and the cross-section of the hub 110 perpendicular to the rotation axis x is circular. The annular guide ring 101 is rotationally symmetrical about the rotation axis x. The three blades 102 are evenly arranged on the outer circumferential surface of the hub 110 and are integrally connected to the hub 110. The hub 110 and the blades 102 can rotate together about the rotation axis x within the cavity 105 of the annular guide ring 101. As an example, the axial flow fan 100 of this application rotates counterclockwise (i.e.,...). Figure 1 The blade 102 rotates about the rotation axis x (in the direction indicated by the middle arrow). The upper surface of the blade 102 forms a pressure surface 111, and the lower surface of the blade 102 forms a suction surface 112. Those skilled in the art will understand that the hub 110 can also be of other shapes, and the number of blades 102 can be at least two. The shape of the hub 110 can be configured to match the number of blades 102. For example, when the number of blades 102 is four, the cross-section of the hub 110 perpendicular to the rotation axis x can also be quadrilateral.

[0021] When the axial flow fan 100 is running, the hub 110 drives each blade 102 to rotate together. However, under the action of centrifugal force, the connection between the blade 102 and the hub 110 is prone to breakage. Furthermore, the blade tip of the blade 102 bears significant pressure and is prone to deformation, thus affecting the gap between the blade 102 and the annular guide ring 101, and consequently affecting the working efficiency of the axial flow fan 100. This application enhances the strength of the blade 102 by providing a wavy, corrugated section in the radial direction of the blade 102. The specific structure of the blade 102 is described below.

[0022] Figure 2A for Figure 1 A three-dimensional structural diagram of the hub 110 and one of the blades 102, viewed from the front. Figure 2BThis is a projection of the blade 102 onto its normal plane, used to show the specific shape and structure of the blade 102. For example... Figure 2A and Figure 2B As shown, the blade 102 has a tip 215, a root 216, a leading edge 213, and a trailing edge 214. The root 216 is located at the edge of the blade 102 for connection with the outer circumferential surface of the hub 110. The tip 215 is located on the opposite side edge to the root 216. The leading edge 213 extends from the leading edge of the tip 215 to the leading edge of the root 216, and the trailing edge 214 extends from the trailing edge of the tip 215 to the trailing edge of the root 216. Thus, the tip 215, root 216, leading edge 213, and trailing edge 214 define the outer edges of the pressure surface 111 and suction surface 112 of the blade 102.

[0023] The blade 102 has a radial height L and a radius R. The radial height L is the distance between the blade tip 215 and the blade root 216 of the blade 102. The radius R is the distance between the blade tip 215 and the axis of rotation x.

[0024] The blade 102 also includes a wavy section comprising at least two crests and at least two troughs, which are staggered in the radial direction of the blade to form the wavy shape. The wavy section enhances the strength of the blade 102 and improves its resistance to centrifugal force during rotation, thus making it less prone to breakage at the blade root 216. Specifically, the wavy section includes at least two recesses extending from the pressure surface 111 towards the suction surface 112 and at least two arches extending from the suction surface 112 towards the pressure surface 111. The at least one recess and at least one arch connect to form the wavy structure. A trough is formed by the lowest point of the recess, and a crest is formed by the highest point of the arch. In the embodiment shown in the figure, at least one recessed portion consists of two recessed portions, namely recessed portion 220 and recessed portion 222. A first trough 240 is formed at the lowest point of recessed portion 220, and a second trough 242 is formed at the lowest point of recessed portion 222. Similarly, at least one arched portion consists of two arched portions, namely arched portion 221 and arched portion 223. A first peak 241 is formed at the highest point of arched portion 221, and a second peak 243 is formed at the highest point of arched portion 223. Furthermore, in the radial direction from the blade tip 215 to the blade root 216, the first trough 240, the first peak 241, the second trough 242, and the second peak 243 are arranged alternately. That is, the first trough 240 is closest to the blade tip 215, and the second peak 243 is closest to the blade root 216.

[0025] Further reference Figure 2BAs shown, on the projection of the blade 102 onto the normal plane, each crest and trough extends circumferentially along the blade 102, and their projection lines form concentric arcs centered at the projection point O of the rotation axis x. Specifically, the first trough 240 forms a trough arc 230 on the projection of the blade 102 onto the normal plane. The trough arc 230 intersects the trailing edge 214 at point K and extends from point K to point M. That is, the projection line of the first trough 240, the trough arc 230, is the arc KM. Extending the trough arc 230, it intersects the leading edge 213 at point J. The first crest 241 forms a crest arc 231 on the projection of the blade 102 onto the normal plane. The crest arc 231 intersects the trailing edge 214 at point N and extends from point N to point I. In other words, the projection line of the first crest 241, the crest arc 231, is the arc NI. Extending the crest arc 231, it intersects the leading edge 213 at point G. The second trough 242 forms a trough arc 232 on the projection of the blade 102 onto the normal plane. The trough arc 232 intersects the trailing edge 214 at point E and extends from point E to point F. In other words, the projection line of the second trough 242, the trough arc 232, is the arc EF. Extending the trough arc 232, it intersects the leading edge 213 at point D. The second crest 243 forms a crest arc 233 on the projection of the blade 102 onto the normal plane. The crest arc 233 intersects the trailing edge 214 at point B and extends from point B to point C. In other words, the projection line of the second crest 243, the crest arc 233, is the arc BC. The crest arc 233 is extended and intersects the leading edge 213 at point A.

[0026] In some specific embodiments, the distance between the projection line of the trough arc 230 and the blade root 216 is 0.9 to 0.95 times the distance between the projection line of the blade tip 215 and the projection line of the blade root 216. That is, the distance between the first trough 240 and the blade root 216 is 0.9 to 0.95 times the radial height L of the blade; for example, in this embodiment, the distance between the first trough 240 and the blade root 216 is 0.9375L. The distance between the projection line of the crest arc 231 and the blade root 216 is 0.7 to 0.8 times the distance between the projection line of the blade tip 215 and the projection line of the blade root 216. That is, the distance between the first crest 241 and the blade root 216 is 0.7 to 0.8 times the radial height L of the blade; for example, in this embodiment, the distance between the first crest 241 and the blade root 216 is 0.75L. The distance between the projection line of the trough arc 232 and the blade root 216 is 0.45 to 0.55 times the distance between the projection lines of the blade tip 215 and the blade root 216. That is, the distance between the second trough 242 and the blade root 216 is 0.45 to 0.55 times the radial height L of the blade. For example, in this embodiment, the distance between the second trough 242 and the blade root 216 is 0.5L. The distance between the projection line of the crest arc 233 and the blade root 216 is 0.2 to 0.3 times the distance between the projection lines of the blade tip 215 and the blade root 216. That is, the distance between the second crest 243 and the blade root 216 is 0.2 to 0.3 times the radial height L of the blade. For example, in this embodiment, the distance between the second crest 243 and the blade root 216 is 0.25L.

[0027] Furthermore, in the circumferential direction of blade 102, for any circumferential section, the acute circumferential angle between the trailing edge 214 and the leading edge 213 forms a circumferential wrap angle θ. On this circumferential section, the acute circumferential angle between each point and the leading edge 213 is the circumferential position angle of that point. For example, in some specific embodiments, on the circumferential section where the first trough 240 is located, the circumferential wrap angle between the trailing edge 214 and the leading edge 213 is the acute circumferential angle θ1 corresponding to the arc JK where the trough arc 230 is located. On the circumferential section where the first trough 240 is located, the circumferential position angle of point M is 0.4θ1. That is, the acute circumferential angle corresponding to the arc between point M and point J is 0.4θ1, and the acute circumferential angle of the trough arc 230 is 0.6θ1. Therefore, the arc length of the trough arc 230 is 0.6 times the arc length of the arc JK.

[0028] Similarly, on the circumferential section where the first crest 241 is located, the circumferential wrap angle is the acute circumferential angle θ2 corresponding to the arc GN, and the circumferential position angle of point I is 0.1θ2. That is to say, the acute circumferential angle corresponding to the arc between point I and point G is 0.1θ2, and the acute circumferential angle of the crest arc 231 is 0.9θ2. Therefore, the arc length of the crest arc 231 is 0.9 times the arc length of the arc GN.

[0029] On the circumferential section where the second trough 242 is located, the circumferential wrap angle is the acute circumferential angle θ3 corresponding to the arc DE, and the circumferential position angle of point F is 0.3θ3. That is, the acute circumferential angle corresponding to the arc between points F and D is 0.3θ3, and the acute circumferential angle of the trough arc 232 is 0.7θ2. Therefore, the arc length of the trough arc 232 is 0.7 times the arc length of the arc DE.

[0030] On the circumferential section where the second crest 243 is located, the circumferential wrap angle is the acute circumferential angle θ4 corresponding to the arc AB, and the circumferential position angle of point C is 0.2θ4. That is, the acute circumferential angle corresponding to the arc between points C and A is 0.2θ4, and the acute circumferential angle of the crest arc 233 is 0.8θ4. Therefore, the arc length of the crest arc 233 is 0.8 times the arc length of the arc AB.

[0031] Those skilled in the art will understand that, although in this embodiment each crest and trough starts from the trailing edge 214 and extends towards the front edge 213, in some other embodiments, each crest and trough may also start from other positions in the circumferential direction and extend towards the front edge, provided that their length in the circumferential direction meets the requirements.

[0032] Further reference Figure 2C As shown, on the radial section of blade 102, each crest and trough has a certain camber height H. Here, camber height refers to the distance in the thickness direction of the blade between the radially aligned line connecting the crest or trough to the corresponding adjacent crest or trough, blade root, or blade tip. For example, the camber height of the first crest 241 is the distance in the thickness direction of the blade 102 between the radially aligned line connecting the first trough 240 and the second trough 242. The camber height of the second crest 243 is the distance in the thickness direction of the blade 102 between the radially aligned line connecting the second trough 242 and the blade root 216. The camber height of the first trough 240 is the distance in the thickness direction of the blade 102 between the radially aligned line connecting the blade tip 215 and the first crest 241. The arch height of the second trough 242 is the distance between the line connecting the first peak 241 and the second peak 243 in the radial direction and the second trough 242 in the thickness direction of the blade 102.

[0033] In some specific embodiments, the maximum arch height of the first trough 240 is 0.6%R to 4%R, the maximum arch height of the first peak 241 is 1.4%R to 12%R, the maximum arch height of the second trough 242 is 0.6%R to 4%R, and the maximum arch height of the second peak 243 is 0.6%R to 3%R.

[0034] By providing at least two crests and at least two troughs in the radial direction of the blade 102, not only can the strength of the blade 102 be increased, but the working efficiency of the axial flow fan 100 can also be improved.

[0035] It should be noted that although the blade shown in this embodiment includes two crests and two troughs arranged continuously and alternately in the radial direction, other embodiments may include more crests and troughs.

[0036] The axial flow fan 100 of this application and a conventional axial flow fan (e.g., an axial flow fan with the same diameter of 510 mm) were compared in a test according to the ANSI / AMCA Standard 210-16. The results are shown in Table 1.

[0037] Conventional axial flow fan This embodiment features an axial flow fan. Fan efficiency (%) 42.3 48.5

[0038] Table 1. Comparison of fan efficiency between conventional axial flow fans and axial flow fan 100.

[0039] As can be seen from Table 1, the fan efficiency of the axial flow fan 100 of this application is improved compared with that of conventional axial flow fans.

[0040] Figure 3A and Figure 3B A comparison diagram of blade deformation of the axial flow fan 100 of this application and a conventional axial flow fan (e.g., an axial flow fan with the same diameter of 510 mm) is shown to illustrate that the axial flow fan of this application can reduce the blade tip deformation. Figure 3A and Figure 3B As shown, in both conventional axial flow fans and the axial flow fan 100 of this application, the blade tips are most prone to deformation. Deformation at the blade tips leads to increased leakage at the blade tips, thus affecting the working efficiency of the axial flow fan. Furthermore, the maximum deformation at the blade tip of a conventional axial flow fan reaches 37.144 mm, while the maximum deformation at the blade tip of the axial flow fan 100 of this application is only 11.25 mm. And from... Figure 3A and Figure 3B As can be seen, in the axial flow fan 100 of this application, the deformation range of the blade tip is also reduced. This indicates that the axial flow fan of this application can reduce the amount and range of deformation at the blade tip.

[0041] Figure 4A and Figure 4B A stress comparison diagram is shown between the axial flow fan 100 of this application and a conventional axial flow fan (e.g., an axial flow fan with the same diameter of 510 mm), to illustrate that the axial flow fan of this application can increase the strength of the blades. Figure 4A and Figure 4BAs shown, the blade roots of both conventional axial flow fans and the axial flow fan 100 of this application experience the highest stress, making them most prone to breakage. Furthermore, the maximum stress at the blade root of a conventional axial flow fan reaches 21.755 MPa, while the maximum stress at the blade root of the axial flow fan 100 of this application is only 11.536 MPa. This demonstrates that the axial flow fan of this application can reduce the maximum stress at the blade root, thereby increasing blade strength.

[0042] The blades described in this application, and the axial flow fan using these blades, increase blade strength by incorporating at least two consecutive pairs of crests and troughs in the radial direction of the blades, preventing breakage at the blade root under excessive power. Generally, adding crests and troughs to axial flow fan blades leads to airflow separation on the blade surface, affecting the fan's efficiency. However, this application controls the position and camber of the crests and troughs, effectively controlling airflow separation on the blade surface and ensuring no impact on the axial flow fan's efficiency. Furthermore, the increased surface area and working area of ​​the blades, due to the added crests and troughs, actually improve the axial flow fan's efficiency.

[0043] Although this application will be described with reference to the specific embodiments shown in the accompanying drawings, it should be understood that the blades and axial flow fans of this application can have many variations without departing from the spirit, scope, and context of the teachings of this application. Those skilled in the art will also recognize that there are different ways to modify the structural details of the embodiments disclosed in this application, all of which fall within the spirit and scope of this application and the claims.

Claims

1. A blade, characterized in that: The blade (102) comprises: A pressure surface (111) and a suction surface (112), the pressure surface (111) and the suction surface (112) forming two opposing surfaces of the blade (102); and The blade has a tip (215), a root (216), a leading edge (213), and a trailing edge (214), which define the outer edges of the pressure surface (111) and the suction surface (112), wherein the leading edge (213) and the trailing edge (214) extend from the tip (215) to the root (216), and wherein the acute circumferential angle between the trailing edge (214) and the leading edge (213) forms a circumferential wrap angle θ in any circumferential section of the blade (102). The blade includes a wave-shaped portion comprising at least two peaks (241, 243) and at least two troughs (240, 242). The troughs (240, 242) are formed by at least one recess (220, 222) that is recessed in the direction from the pressure surface (111) to the suction surface (112). The peaks (241, 243) are formed by at least one arched portion (221, 223) that is arched in the direction from the suction surface (112) to the pressure surface (111). The at least one recess (220, 222) and the at least one arched portion (221, 223) are connected to form the wave-shaped portion. The at least two peaks (241, 243) and the at least two troughs (240, 242) are staggered radially on the blade (102), and each peak (241, 243) and each trough (240, 242) extends circumferentially on the blade (102). In the radial direction from the blade tip (215) to the blade root (216), the at least two peaks (241, 243) and the at least two troughs (240, 242) sequentially include a first trough (240), a first peak (241), a second trough (242), and a second peak (243), wherein the first trough (240) is closest to the blade tip (215). Wherein, on the circumferential section where the first trough (240) is located, the acute circumferential angle between the trailing edge (214) and the leading edge (213) forms a circumferential wrap angle θ1, and the acute circumferential angle of the first trough (240) is 0.6θ1; On the circumferential section where the first wave crest (241) is located, the acute circumferential angle between the trailing edge (214) and the leading edge (213) forms a circumferential wrap angle θ2, and the acute circumferential angle of the first wave crest (241) is 0.9θ2; On the circumferential section where the second trough (242) is located, the acute circumferential angle between the trailing edge (214) and the leading edge (213) forms a circumferential wrap angle θ3, and the acute circumferential angle of the second trough (242) is 0.7θ3; On the circumferential section where the second wave peak (243) is located, the acute circumferential angle between the trailing edge (214) and the leading edge (213) forms a circumferential wrap angle θ4, and the acute circumferential angle of the second wave peak (243) is 0.8θ4.

2. The blade according to claim 1, characterized in that: The blade (102) is capable of rotating about a rotation axis (x), which is perpendicular to the normal plane; Each of the wave crests (241, 243) forms a wave crest arc (231, 233) on the projection of the blade (102) onto the normal plane; and Each of the valleys (240, 242) forms a valley arc (230, 232) on the projection of the normal plane of the blade (102). Each of the wave crest arcs (231, 233) and each of the wave trough arcs (230, 232) are concentric arcs centered at the projection center (O) of the rotation axis (x).

3. The blade according to claim 1, characterized in that: The blade (102) has a blade radial height (L), which is the distance between the blade root (216) and the blade tip (215) on the projection of the blade (102) onto the normal plane. Wherein, the distance between the first trough (240) and the leaf root (216) is (0.9~0.95)L; The distance between the first wave peak (241) and the leaf root (216) is (0.7~0.8)L; The distance between the second trough (242) and the leaf root (216) is (0.45~0.55)L; The distance between the second peak (243) and the leaf root (216) is (0.2~0.3)L.

4. The blade according to claim 3, characterized in that: The distance between the first trough (240) and the leaf root (216) is 0.9375L; The distance between the first peak (241) and the leaf root (216) is 0.75L; The distance between the second trough (242) and the leaf root (216) is 0.5L; The distance between the second peak (243) and the leaf root (216) is 0.25L.

5. The blade according to claim 1, characterized in that: Any point on the blade (102) has a circumferential position angle, and on the circumferential cross section of the point, the circumferential position angle is the acute circumferential angle between the point and the leading edge; The circumferential position angle of the starting position of the first trough (240) is θ1, and the circumferential position angle of the ending position of the first trough (240) is 0.4θ1; The circumferential position angle of the starting position of the first wave peak (241) is θ2, and the circumferential position angle of the ending position of the first wave peak (241) is 0.1θ2; The circumferential position angle of the starting position of the second trough (242) is θ3, and the circumferential position angle of the ending position of the second trough (242) is 0.3θ3; The circumferential position angle of the starting position of the second peak (243) is θ4, and the circumferential position angle of the ending position of the second peak (243) is 0.2θ4.

6. The blade according to claim 1, characterized in that: The blade (102) is rotatable about the rotation axis (x), and the blade (102) has a blade radius (R), which is the distance between the blade tip (215) and the rotation axis (x). On each radial section of the blade (102), the maximum arch height of the first trough (240) is (0.6~4)%R; The maximum arch height of the first peak (241) is (1.4~12)%R; The maximum arch height of the second trough (242) is (0.6~4)%R; The maximum arch height of the second peak (243) is (0.6~3)%R.

7. The blade according to claim 1, characterized in that: The peaks (241, 243) and troughs (240, 242) are rounded.

8. An axial flow impeller (100), characterized in that... include: A hub (110) having a rotation axis (x) and being rotatable about the rotation axis (x); and At least two blades (102) according to any one of claims 1-7, the at least two blades (102) being arranged on the outer circumferential surface of the hub (110).

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