Wind wheel blades

Abstract

The present invention discloses a blade of a wind wheel, wherein the blade extends in a front-rear direction, and the blade has a leeward surface located at the upper side and a windward surface located at the lower side, the windward surface is intercepted by a plane perpendicular to the left-right direction to form a lower surface profile, and the leeward surface is intercepted to form an upper surface profile, the lower surface profile includes a lower convex line and an upper concave line, and the line connecting the two end points of the lower surface profile is used as a reference, the lower convex line is in a shape of at least a portion convex downward, the upper concave line is in a shape of at least a portion concave upward, and the upper concave line is located at the rear side of the lower convex line. The blade of the wind wheel according to the embodiment of the present invention has a good noise reduction effect.

Description

Technical Field

[0001] The present invention relates to the technical field of power equipment, and in particular to a blade of a wind wheel. Background Art

[0002] As the appearance and performance of window air conditioners are improved, the noise problem has increasingly attracted the attention of users, enterprises and scientific researchers. Therefore, research on noise reduction technology for window air conditioners has very important practical application value. Summary of the invention

[0003] The present invention aims to solve one of the technical problems in the related art at least to a certain extent. To this end, one object of the present invention is to provide a blade of a wind wheel with good noise reduction effect.

[0004] According to the blades of the wind wheel according to an embodiment of the present invention, the blades extend in the front-to-back direction, and the blades have a leeward surface located on the upper side and a windward surface located on the lower side, the windward surface is cut by a plane perpendicular to the left-right direction to form a lower surface profile line, and the leeward surface is cut by a plane perpendicular to the left-right direction to form an upper surface profile line, the lower surface profile line includes a lower convex line and an upper concave line, with the line connecting the two end points of the lower surface profile line as a reference, the lower convex line is in a shape in which at least a portion is convex downward, the upper concave line is in a shape in which at least a portion is concave upward, and the upper concave line is located on the rear side of the lower convex line.

[0005] The blades of the wind wheel according to the embodiment of the present invention have a good noise reduction effect.

[0006] In addition, the blades of the wind wheel according to the above embodiment of the present invention may also have the following additional technical features:

[0007] In some embodiments, a dimension L1' of the lower convex line along the front-to-back direction is smaller than a dimension L2' of the upper concave line along the front-to-back direction.

[0008] In some embodiments, L1':L2' is in the range of 1:9 to 1:5.

[0009] In some embodiments, L1':L2' is in the range of 1:8 to 1:6.

[0010] In some embodiments, a height H1' of the lower convex line is smaller than a height H2' of the upper concave line.

[0011] In some embodiments, H1':H2' is in the range of 1:5 to 1:3.

[0012] In some embodiments, the height of the lower convex line is H1', ​​the dimension of the windward surface along the front-rear direction is LY', and H1':LY' is in the range of 0.02 to 0.03.

[0013] In some embodiments, the height of the concave portion of the upper concave line is H2', the dimension of the windward surface along the front-rear direction is LY', and H2':LY' is in the range of 0.08 to 0.1.

[0014] In some embodiments, the distance between the top of the lower convex line and the front end point of the lower convex line in the front-back direction is L3', and the distance between the top of the lower convex line and the rear end point of the lower convex line in the front-back direction is L4', L3'<L4'.

[0015] In some embodiments, L3' / L4' is in the range of 1 / 5 to 1 / 3.

[0016] In some embodiments, the distance between the top of the lower convex line and the front end point of the lower convex line in the front-to-back direction is L3', the dimension of the windward surface along the front-to-back direction is LY', and L3' / LY' is in the range of 0.0125 to 0.05.

[0017] In some embodiments, the distance between the top of the upper concave line and the front end point of the upper concave line in the front-back direction is L5', and the distance between the top of the upper concave line and the rear end point of the upper concave line in the front-back direction is L6', and L5'<L6'.

[0018] In some embodiments, L5' / L6' is in the range of 0.7 to 0.9.

[0019] In some embodiments, the distance between the top of the upper concave line and the rear end point of the upper concave line in the front-to-back direction is L6', the dimension of the windward surface along the front-to-back direction is LY', and L6' / LY' is in the range of 0.45 to 0.55.

[0020] In some embodiments, the rear endpoint of the lower convex line is connected to the front end point of the upper concave line; and / or the front end point of the lower convex line extends to the front end point of the windward surface; and / or the rear endpoint of the upper concave line extends to the rear end point of the windward surface.

[0021] In some embodiments, the lower convex line and the upper concave line are both arc surfaces.

[0022] In some embodiments, the windward surface is a smooth curved surface.

[0023] In some embodiments, at least a portion of the leeward surface is convex upward.

[0024] In some embodiments, the leeward surface is shaped to extend first upward and then downward from the front end point to the rear end point.

[0025] In some embodiments, the distance between the top of the leeward surface and the front end point of the leeward surface in the front-rear direction is L7', and the distance between the top of the leeward surface and the rear end point of the leeward surface in the front-rear direction is L8', and L7'<L8'.

[0026] In some embodiments, L7' / L8' is in the range of 1 / 3 to 2 / 3.

[0027] In some embodiments, a ratio H3' / LB' of a maximum height H3' of the leeward surface convexity to a dimension LB' of the leeward surface in the front-rear direction is in a range of 0.14 to 0.16, preferably in a range of 0.153 to 0.154.

[0028] In some embodiments, the front end point of the windward surface is connected to the front end point of the leeward surface; and / or the rear end point of the windward surface is connected to the rear end point of the leeward surface.

[0029] In some embodiments, the leeward surface is a smooth curved surface.

[0030] In some embodiments, the leading edge thickness of the blade is greater than the trailing edge thickness of the blade, and the thickness of the blade gradually decreases from the leading edge to the trailing edge.

[0031] In some embodiments, the thickness of the blade increases first and then decreases in the front-to-back direction.

[0032] In some embodiments, the front end of the blade has a maximum thickness at a position with a spacing of 0.1LP to 0.2LP, where LP is the length of the blade along the front-to-back direction.

[0033] In some embodiments, the blade extends from the leading edge to the trailing edge along a convex arc in the middle. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 and Figure 2 Schematic diagram of a blade according to an embodiment of the present invention.

[0035] Figure 3 and Figure 4 is a cross-sectional view of a blade according to an embodiment of the present invention.

[0036] Figure 5 Schematic diagram of a wind wheel according to an embodiment of the present invention.

[0037] Figure 6 is a cross-sectional view of a wind wheel according to an embodiment of the present invention.

[0038] Figure 7 It is a schematic diagram of the arrangement of the mid-arc lines of the blades in the wind wheels of different groups according to the present invention.

[0039] Figure 8 It is a schematic diagram of the arrangement of blades in different groups of wind wheels of the present invention.

[0040] Fig. 9 Schematic diagram of a blade in one embodiment of the present invention. DETAILED DESCRIPTION

[0041] The noise of window air conditioners is mainly composed of mechanical noise, electromagnetic noise, and aerodynamic noise, among which aerodynamic noise accounts for the largest proportion. Therefore, the noise of the duct system has become the focus of research on air conditioning noise reduction. The duct system is mainly composed of a volute and an impeller. There are few studies on the noise reduction of window air conditioner duct systems, but there are more extensive studies on the noise problem of centrifugal fans. The impeller is a rotating component in the fan, which plays an important role in the energy transfer of the fan and is also an important source of noise.

[0042] The long-eared owl can swoop silently at a flying speed of 8m / s, which also corresponds to the inlet speed of the general fan airflow. The 40% cross-section airfoil with good aerodynamic performance and low noise characteristics is extracted, which can be used in the improvement of fan blade profiles.

[0043] The present invention extracts a 40% span-wise airfoil of a long-eared owl wing with low noise characteristics, takes a centrifugal fan for a certain type of window air conditioner as the research object, and uses a numerical simulation method to analyze the influence of different application modes of the mid-arc lines of the owl-like wing airfoil on the noise performance of the fan. The effectiveness of the numerical calculation model and the optimization design is verified through experimental means, and the noise reduction effect is visualized and analyzed.

[0044] Among them, the 40% spanwise airfoil refers to the airfoil of the long-eared owl's wing at 40% of the cross-section along the wingspan direction (the direction of wing extension), which exhibits high efficiency and low noise performance; similarly, a 30% spanwise airfoil can also be used.

[0045] Of course, the blades, impellers, etc. in the present invention are not limited to being used in window-type air conditioners.

[0046] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0047] like Figure 1According to the blade 1 of the wind wheel according to the embodiment of the present invention, the blade 1 extends in the front-to-back direction, and has a leeward surface 101 located on the upper side and a windward surface 104 located on the lower side, the windward surface 104 includes a lower convex surface 102 and an upper concave surface 103, the lower convex surface 102 is in a shape in which at least a portion is convex downward away from the leeward surface 101, the upper concave surface 103 is in a shape in which at least a portion is concave upward toward the leeward surface 101, and the upper concave surface 103 is located on the rear side of the lower convex surface 102.

[0048] According to the blade 1 of the wind wheel of the embodiment of the present invention, when the airflow passes through the windward surface 104, it will first pass through the lower convex surface 102 and then pass through the upper concave surface 103. The guidance of the upper convex surface and the lower convex surface 102 can effectively reduce the noise of the airflow.

[0049] It should be noted that the above concave and convex are specific to the blade itself as a reference, and the surface connecting the front edge and the rear edge of the windward surface is the reference surface. The surface that is convex downward from the reference surface is convex downward, and the surface that is concave upward relative to the reference surface is concave upward. Specifically, the reference surface is defined according to the following method: take a point on the front edge of the windward surface, find a point corresponding to the point on the rear edge of the windward surface, connect the two points to form a line, select all the points on the front edge of the windward surface as lines, and these lines are combined to form the reference surface.

[0050] Of course, this is only one embodiment of the present invention, that is, the airflow direction and the surface guiding the airflow in the present invention can be in other forms, for example, the airflow first passes through the upper concave surface and then passes through the lower convex surface.

[0051] In addition, it should be noted that the directions of up, down, left, right, front, and back in the present invention are described based on the drawings, and these directions will change accordingly for different uses and placements of the blades. In addition, the following description of height, etc. is also based on the directions in the drawings, which is intended to simplify the description for easy understanding and cannot be understood as limiting the scope of protection of the present invention.

[0052] exist Figure 1 In the illustrated embodiment, the front edge and the rear edge of the windward surface are parallel to each other, and the reference surface is formed into a plane, while when the front edge and the rear edge of the windward surface are not parallel, the reference surface may not be a plane. For example, the front edge and the rear edge of the windward surface are inclined to each other; or at least one of the front edge and the rear edge of the windward surface is in an arc shape.

[0053] In some embodiments of the present invention, the dimension L1 of the lower convex surface 102 along the front-to-back direction is smaller than the dimension L2 of the upper concave surface 103 along the front-to-back direction, so as to improve the flow guiding effect of the lower convex surface 102 and reduce noise.

[0054] Taking the case where the airflow first passes through the lower convex surface 102 as an example, under the guiding effect of the lower convex surface 102, the gas can be better guided to the blades, thereby improving the conveying efficiency of the blades and avoiding turbulence.

[0055] In addition, in the present invention, L1 may also be set to be greater than L2, which can also reduce noise.

[0056] Further, the ratio of L1 to L2 may have different forms, for example, L1:L2 is in the range of 1:9 to 1:5. Preferably, L1:L2 is in the range of 1:8 to 1:6.

[0057] In some embodiments of the present invention, the height H1 of the lower convex surface 102 is smaller than the height H2 of the upper concave surface 103. After being guided by the lower convex surface 102, the airflow enters the upper concave surface 103. Since the upper concave surface 103 has a relatively large depth, the airflow will be thrown out by the upper concave surface 103, which can not only reduce or avoid the noise generated by the unstable circulation of the airflow, but also facilitate the delivery of the airflow, so that the airflow can be delivered quickly and stably, thereby improving the efficiency of air supply.

[0058] Further, H1:H2 is in the range of 1:5 to 1:3.

[0059] In some embodiments of the present invention, the height of the lower convex surface 102 is H1, the dimension of the windward surface 104 along the front-to-back direction is LY, and H1:LY is in the range of 0.02 to 0.03.

[0060] Further, the height of the upper concave surface 103 is H2, the dimension of the windward surface 104 along the front-rear direction is LY, and H2:LY is in the range of 0.08 to 0.1.

[0061] In some embodiments of the present invention, the distance between the top of the lower convex surface 102 and the front edge of the lower convex surface 102 in the front-to-back direction is L3, and the distance between the top of the lower convex surface 102 and the rear edge of the lower convex surface 102 in the front-to-back direction is L4, and L3<L4.

[0062] Preferably, L3 / L4 is in the range of 1 / 5 to 1 / 3.

[0063] In some embodiments of the present invention, the distance between the top of the lower convex surface 102 and the front edge of the lower convex surface 102 in the front-to-back direction is L3, the dimension of the windward surface 104 in the front-to-back direction is LY, and L3 / LY is in the range of 0.0125 to 0.05.

[0064] In some embodiments of the present invention, the distance between the top of the upper concave surface 103 and the front edge of the upper concave surface 103 in the front-to-back direction is L5, and the distance between the top of the upper concave surface 103 and the rear edge of the upper concave surface 103 in the front-to-back direction is L6, and L5<L6.

[0065] Further, L5 / L6 is in the range of 0.7 to 0.9.

[0066] In some embodiments of the present invention, the distance between the top of the upper concave surface 103 and the rear edge of the upper concave surface 103 in the front-to-back direction is L6, the dimension of the windward surface 104 in the front-to-back direction is LY, and L6 / LY is in the range of 0.45 to 0.55.

[0067] In some embodiments of the present invention, the rear edge of the lower convex surface 102 is connected to the front edge of the upper concave surface 103, so as to further facilitate the guidance of the airflow.

[0068] In addition, the lower convex surface 102 and the upper concave surface 103 may also be connected by a plane, a curved surface or other forms of surfaces.

[0069] Furthermore, the front edge of the lower convex surface 102 extends to the front edge of the windward surface 104. Furthermore, the rear edge of the upper concave surface 103 extends to the rear edge of the windward surface 104. The guiding effect of the airflow is further improved.

[0070] Preferably, the lower convex surface 102 and the upper concave surface 103 are both cambered surfaces. In addition, the lower convex surface 102 and the lower concave surface 103 in the present invention can also be in other forms, such as being formed by connecting a plurality of planes.

[0071] Advantageously, the windward surface 104 is a smooth curved surface. In other words, each part of the windward surface 104 is smoothly transitioned, for example, a rounded corner can be provided for smooth transition.

[0072] In some embodiments of the present invention, at least a portion of the leeward surface 101 is convex upward. The leeward surface can also guide airflow.

[0073] Further, the leeward surface 101 extends upward first and then downward from the front edge to the rear edge. In other words, the leeward surface does not have an undulating shape, but is only a single plane, or in other words, a straight line connecting any two points on the leeward surface is located on the inner side (lower side) of the leeward surface.

[0074] Advantageously, the distance between the top of the leeward surface 101 and the front edge of the leeward surface 101 in the front-rear direction is L7, and the distance between the top of the leeward surface 101 and the rear edge of the leeward surface 101 in the front-rear direction is L8, and L7<L8.

[0075] Further, L7 / L8 is in the range of 1 / 3 to 2 / 3.

[0076] Advantageously, a ratio H3 / LB of a maximum height H3 of the convexity of the leeward surface 101 to a dimension LB of the leeward surface 101 in the front-rear direction is in a range of 0.14 to 0.16.

[0077] In the appended Figure 1 In the figure, since the front edge of the leeward surface is connected to the front edge of the windward surface, and the rear edge of the leeward surface is connected to the rear edge of the windward surface, the dimension LB of the leeward surface along the front-to-back direction is the same as the dimension LY of the windward surface along the front-to-back direction.

[0078] Preferably, H3 / LB is in the range of 0.153 to 0.154.

[0079] In some embodiments of the present invention, the front edge of the windward surface 104 is connected to the front edge of the leeward surface 101.

[0080] Furthermore, the rear edge of the windward surface 104 is connected to the rear edge of the leeward surface 101 .

[0081] Advantageously, the leeward surface 101 is a smooth curved surface.

[0082] Preferably, the leading edge thickness of the blade 1 is greater than the trailing edge thickness of the blade 1 , and the thickness of the blade 1 gradually decreases from the leading edge to the trailing edge.

[0083] In some embodiments of the present invention, the thickness of the blade 1 first increases and then decreases in the front-to-back direction.

[0084] Further, the front end of the blade 1 has a maximum thickness at a position with a spacing of 0.1LP to 0.2LP, where LP is the length of the blade 1 along the front-rear direction.

[0085] In some embodiments of the present invention, the blade 1 extends from the leading edge to the trailing edge along a convex arc in the middle.

[0086] In addition, the present invention also provides another blade.

[0087] like Figure 2 According to the blade 1 of the wind wheel of the embodiment of the present invention, the blade 1 extends in the front-to-back direction, and the blade 1 has a leeward surface 101 located on the upper side and a windward surface 104 located on the lower side, and the lower surface profile 104' includes a lower convex line 102' and an upper concave line 103'. Specifically, the blade is cut with a plane perpendicular to the left-right direction, wherein the windward surface forms a lower surface in the cross section, and the leeward surface forms an upper surface profile in the cross section. The lower convex line 102' is in a shape in which at least a portion of it convexes downward away from the upper surface profile 101', and the upper concave line 103' is in a shape in which at least a portion of it is concave upward toward the upper surface profile 101', and the upper concave line 103' is located at the rear side of the lower convex line 102'.

[0088] The blades 1 of the wind wheel according to the embodiment of the present invention can effectively reduce the noise of airflow.

[0089] It should be noted that the above concave and convex are specific to the blade itself as a reference, and the surface connecting the front end point and the rear end point of the lower surface profile is the reference surface. The surface that bulges downward from the reference surface is the convex surface, and the surface that is recessed upward relative to the reference surface is the concave surface. Specifically, the reference surface is defined in the following way: take a point on the front end point of the lower surface profile, find a point corresponding to the point on the rear end point of the lower surface profile, connect the two points to form a line, select all the points on the front end point of the lower surface profile to make lines, and these lines are combined to form the reference surface.

[0090] In addition, it should be noted that in the blades described in the previous embodiments, the blades are cut perpendicular to the left and right directions to obtain the upper surface profile lines, lower surface profile lines and other structures in the present application, but this does not mean that the blades in the present application are the same as the blades in the previous embodiments. The combination of the upper surface profile lines and the lower surface profile lines in the present application can obtain blades of different embodiments.

[0091] For example, the blade is configured to be composed of multiple parts arranged in an staggered manner, and the cross-section of each part may have the upper surface profile and the lower surface profile of the present invention, or only a part of the cross-section may have the upper surface profile and the lower surface profile of the present invention.

[0092] In some embodiments of the present invention, the dimension L1' of the lower convex line 102' along the front-to-back direction is smaller than the dimension L2' of the upper concave line 103' along the front-to-back direction, so as to improve the flow guiding effect of the lower convex line 102' and reduce noise.

[0093] Further, L1':L2' is in the range of 1:9 to 1:5.

[0094] Preferably, L1':L2' is in the range of 1:8 to 1:6.

[0095] In some embodiments of the present invention, the lower convex line 102' has a lower convex height H1' that is smaller than the upper concave height H2' of the upper concave line 103'. After being guided by the lower convex line 102', the airflow enters the upper concave line 103'. Since the upper concave line 103' has a relatively large depth, the airflow will be thrown out by the upper concave line 103', which can not only reduce or avoid the noise generated by the unstable circulation of the airflow, but also facilitate the delivery of the airflow, so that the airflow can be delivered quickly and stably, thereby improving the efficiency of air delivery.

[0096] Further, H1':H2' is in the range of 1:5 to 1:3.

[0097] In some embodiments of the present invention, the height of the lower convex line 102' is H1', ​​the dimension of the lower surface profile line 104' along the front-to-back direction is LY', and H1':LY' is in the range of 0.02 to 0.03.

[0098] Further, the height of the upper concave line 103' is H2', the dimension of the lower surface profile line 104' along the front-rear direction is LY', and H2':LY' is in the range of 0.08 to 0.1.

[0099] In some embodiments of the present invention, the distance between the top of the lower convex line 102' and the front end of the lower convex line 102' in the front-back direction is L3', and the distance between the top of the lower convex line 102' and the rear end of the lower convex line 102' in the front-back direction is L4', L3'<L4'.

[0100] Preferably, L3' / L4' is in the range of 1 / 5 to 1 / 3.

[0101] In some embodiments of the present invention, the distance between the top of the lower convex line 102' and the front end of the lower convex line 102' in the front-rear direction is L3', the dimension of the lower surface profile line 104' in the front-rear direction is LY', and L3' / LY' is in the range of 0.0125 to 0.05.

[0102] In some embodiments of the present invention, the distance between the top of the upper concave line 103' and the front end of the upper concave line 103' in the front-back direction is L5', and the distance between the top of the upper concave line 103' and the rear end of the upper concave line 103' in the front-back direction is L6', L5'<L6'.

[0103] Further, L5' / L6' is in the range of 0.7 to 0.9.

[0104] In some embodiments of the present invention, the distance between the top of the upper concave line 103' and the rear end point of the upper concave line 103' in the front-rear direction is L6', the dimension of the lower surface profile line 104' in the front-rear direction is LY', and L6' / LY' is in the range of 0.45 to 0.55.

[0105] In some embodiments of the present invention, the rear end point of the lower convex line 102' is connected to the front end point of the upper concave line 103'.

[0106] Furthermore, the front end point of the lower convex line 102 ′ extends to the front end point of the lower surface profile line 104 ′.

[0107] Furthermore, the rear end point of the upper concave line 103' extends to the rear end point of the lower surface profile line 104'.

[0108] Preferably, the lower convex line 102 ′ and the upper concave line 103 ′ are both cambered surfaces.

[0109] Advantageously, the lower surface profile 104 ′ is a smooth curved surface.

[0110] In some embodiments of the present invention, at least a portion of the upper surface profile line 101 ′ is convex upward.

[0111] Furthermore, the upper surface profile line 101 ′ is a shape extending first upward and then downward from the front end point to the rear end point.

[0112] Advantageously, the distance between the top of the upper profile line 101' and the front end of the upper profile line 101' in the front-rear direction is L7', and the distance between the top of the upper profile line 101' and the rear end of the upper profile line 101' in the front-rear direction is L8', L7'<L8'.

[0113] Further, L7' / L8' is in the range of 1 / 3 to 2 / 3.

[0114] Advantageously, a ratio H3' / LB' of a maximum height H3' of the convexity of the upper surface profile line 101' to a dimension LB' of the upper surface profile line 101' in the front-rear direction is in a range of 0.14 to 0.16.

[0115] In the appended Figure 2 In the figure, since the front end point of the upper surface profile is connected to the front end point of the lower surface profile, and the rear end point of the upper surface profile is connected to the rear end point of the lower surface profile, the dimension LB' of the upper surface profile along the front-to-back direction is the same as the dimension LY' of the lower surface profile along the front-to-back direction.

[0116] Preferably, H3' / LB' is in the range of 0.153 to 0.154.

[0117] In some embodiments of the present invention, the front end of the lower surface profile line 104' is connected to the front end of the upper surface profile line 101'.

[0118] Furthermore, the rear end point of the lower surface profile line 104 ′ is connected to the rear end point of the upper surface profile line 101 ′.

[0119] Advantageously, the upper surface profile 101 ′ is a smooth curved surface.

[0120] Preferably, the leading edge thickness of the blade 1 is greater than the trailing edge thickness of the blade 1 , and the thickness of the blade 1 gradually decreases from the leading edge to the trailing edge.

[0121] In some embodiments of the present invention, the thickness of the blade 1 first increases and then decreases in the front-to-back direction.

[0122] Further, the front end of the blade 1 has a maximum thickness at a position with a spacing of 0.1LP to 0.2LP, where LP is the length of the blade 1 along the front-rear direction.

[0123] In some embodiments of the present invention, the blade 1 extends from the leading edge to the trailing edge along a convex arc in the middle.

[0124] In addition, the present invention also provides a blade of a wind wheel in another embodiment. It should be noted that the blades of different embodiments provided by the present invention can be combined together.

[0125] According to the blade of the wind wheel of the embodiment of the present invention, the blade extends in the front-to-back direction, and the blade has a leeward surface located on the upper side and a windward surface located on the lower side, the windward surface is intercepted by a plane perpendicular to the left-right direction to form a lower surface profile line, and the leeward surface is intercepted to form an upper surface profile line, a coordinate system is established with the front end point of the lower surface profile line as the origin, the line connecting the two end points of the lower surface profile line as the x-axis, and the up-down direction as the y-axis, and the lower surface profile line satisfies:

[0126]

[0127]

[0128]

[0129] in, is the mid-arc coordinate of the blade, is the Y coordinate value of the lower surface profile, is the distribution of the thickness of the blade along the vertical direction on the x-axis, is the length of the lower surface profile along the left and right direction, x is the x-axis coordinate, , is the maximum Y-axis coordinate value of the middle arc, are the polynomial coefficients describing the blades, is the maximum thickness of the blade, are the polynomial coefficients describing the blade.

[0130] The blades of the wind wheel according to the embodiment of the present invention adopt an owl-wing blade design, which can reduce noise while ensuring or improving the air supply effect.

[0131] According to one embodiment of the present invention, and are the polynomial coefficients obtained by least squares fitting.

[0132] Further, , , , , , , .

[0133] Preferably, and satisfy:

[0134]

[0135]

[0136] in,

[0137] Advantageously, =0.4.

[0138] According to the above formulas, the 40% cross-section airfoil of the long-eared owl wing is extracted. The specific parameters of the airfoil are shown in Table 1, where +y / c is the relative coordinate of the upper surface line of the blade, and -y / c is the relative coordinate of the lower surface line of the blade. Fig. 9 It is an owl-wing airfoil profile drawn based on airfoil data points.

[0139] Furthermore, the upper surface profile satisfy:

[0140] in, is the Y coordinate value of the upper surface profile.

[0141] Furthermore, the front end point of the windward surface is connected to the front end point of the leeward surface, and the rear end point of the windward surface is connected to the rear end point of the leeward surface.

[0142] Table 1 Owl-like wing airfoil parameters

[0143]

[0144] In addition, the present invention also provides a wind wheel 100, comprising: a shell 2 and blades 1, the shell 2 having an air inlet 201 and an air outlet 202, the blades are arranged on the shell, and the blades extend in a direction from the air inlet to the air outlet, and the blades are blades according to the aforementioned wind wheel.

[0145] Further, the blades include a plurality of blades, the plurality of blades are arranged in a ring shape at intervals, and the blades extend from a leading edge to a trailing edge along a radial direction of the ring shape.

[0146] Advantageously, the blade extends along an arc line from the leading edge to the trailing edge. Further, the blade extends along an arc line from the leading edge to the trailing edge.

[0147] Preferably, the leading edge of the blade is adjacent to the center of the ring, the leading edge of the blade has an installation angle in the range of 20° to 60°, and the trailing edge of the blade has an installation angle in the range of 80° to 120°.

[0148] In order to clearly illustrate the advantages of the wind wheel having the blades of the present invention, the present invention describes in detail the testing method for the wind wheel.

[0149] The blades of the present invention can reduce the noise of the wind wheel and improve the air supply effect of the wind wheel. The present invention tested the wind wheel of the present invention under the following test environment.

[0150] 1 Numerical calculation

[0151] 1.1 Physical Model

[0152] Taking the window air conditioner room as an example, the indoor air duct system of the window air conditioner is mainly composed of a volute and an impeller.

[0153] According to the structure of the air duct system, the fluid area is three-dimensionally modeled. The fluid area is mainly divided into the inlet area, impeller area, and volute area (the inlet and outlet extend 0.5 and 1 times the outer diameter of the impeller respectively). ICEM is used for unstructured meshing, and local mesh encryption is performed on the leading and trailing edges of the impeller blades and the volute tongue area. Under the premise of the selected turbulence model near-wall equation, the y+ value of the mesh area is between 30 and 100. In order to ensure the accuracy and effectiveness of the numerical calculation, the mesh is verified to be independent. Finally, the mesh in the inlet area is 790,000, the mesh in the impeller area is 1.53 million, and the mesh in the volute area is 1.72 million, totaling 4.04 million.

[0154] 1.2 Flow field calculation

[0155] 1.2.1 Constant calculation

[0156] The commercial software Fluent was used to numerically calculate the internal flow field. The control equation was the Navier-Stokes equation. The Realizable k-epsilon model was used for turbulence calculation. The near-wall equation used the standard wall function. The pressure-velocity coupling used the SIMPLE algorithm. The pressure discretization format used the PRESTO! format. The momentum equation, energy equation, and turbulence dissipation equation all used the second-order upwind format. The calculation convergence residual was set to 10 -4 The total pressure at the inlet boundary is set to 0Pa, and the static pressure at the outlet is set to 0Pa to calculate the maximum air volume. The volute area and the inlet area are set as static areas, and the impeller area is set as a rotating area. The FrameMotion model is used, and the rotation speed of the rotating area is set to 1500rpm.

[0157] 1.2.2 Unsteady calculation

[0158] The converged solution of the steady calculation is used as the initial value for the unsteady calculation. The second-order implicit format is used for the time term. The impeller area is a rotating area and the Mesh Motion model is used instead. The time step of the unsteady calculation is determined by the following formula:

[0159]

[0160] Where: K is the maximum number of iterations in each time step, K=30; n is the impeller speed, n=1500rpm; Z is the number of impeller blades, Z=11.

[0161] According to calculations, the time step length in the unsteady calculation process of the present invention is s, the impeller rotates 5 weeks, and the calculation results of the monitored variables show obvious periodic changes, indicating that the flow in the fan has reached a stable flow state.

[0162] 1.2.3 Noise calculation

[0163] The stable flow field obtained by unsteady calculation is used as the input condition of the FW-H acoustic equation, and the noise source and receiving point are set, and then the transient calculation of the impeller rotating for 5 weeks is performed. Since the integral solution method is used in Fluent software to calculate the far-field noise, there is no need to establish an additional acoustic grid outside the convection field. Therefore, when setting the noise source and receiving point, the noise source is set to the volute and impeller wall, and the noise receiving point is set according to the test point specified on the indoor side of the window air conditioner in GBT 7725-2004 "Room Air Conditioner" for comparison with the experiment. According to the coordinate system, the final receiving point is set to (-40.32mm, 8.01mm, 1110.6mm).

[0164] After the sound field calculation is completed, the spectrum diagram of noise calculation can be obtained through fast Fourier transform. The passing frequency of the blade can be calculated as follows:

[0165]

[0166] Where: I is the harmonic number (I=1 is the fundamental frequency). The fundamental frequency of the fan calculated by formula (8) is 275 Hz, and the wavelength is 1.2364 m. Since the wavelength is much larger than the characteristic size of the fan, the reflection, diffraction and scattering of the noise between the volute and the impeller can be ignored in the noise calculation.

[0167] 2 Experimental testing

[0168] 2.1 Aerodynamic performance test

[0169] The aerodynamic performance test was carried out in accordance with GB / T1236-2000 Performance test of industrial ventilators using standardized air ducts, using a type B test device. The system mainly consists of a test fan, an auxiliary fan, a nozzle, a temperature sensor, a differential pressure transmitter, and a data acquisition system. Through the above devices and instruments, the nozzle diameter suitable for the test was selected, and the fan flow was finally obtained through the data acquisition system. In the test, the outlet grille, dust removal net, evaporator and other components were removed, and only the fan part was retained, the purpose of which was to facilitate comparison with numerical calculations.

[0170] 2.2 Noise Test

[0171] The noise test was conducted in a professional semi-anechoic room with a laboratory background noise of 17.0dB. The test used a B&K 4189 sound pressure sensor to measure the sound pressure, which was transmitted to the LMS SCADAS Mobile SCM01 data acquisition system through a B&K 2669 preamplifier. The collected signal was processed by the LMS Test.Xpress 7A vibration noise analysis software. Before the experiment, the sound pressure sensor was calibrated with a B&K 4231 acoustic calibrator, and the test was carried out after the operation was stable. The experimental device meets the requirements of GBT7725-2004 "Room Air Conditioner". The test noise test points are measured according to the standard, that is, 1m from the front surface of the air conditioner and 1m from the ground, which is the same as the receiving point for noise calculation.

[0172] 2.3 Comparison and verification between experimental test and numerical simulation

[0173] Table 2 gives the comparison results of experimental tests and numerical simulations. The fan test was conducted when the air conditioner was removed from the outlet grille, dust removal net, and evaporator. Through preliminary experimental tests, it was found that the air conditioning components such as the outlet grille, dust removal net, and evaporator have a certain impact on the air volume, but have little impact on the noise. Therefore, air conditioning noise reduction can focus on reducing fan noise. Numerical simulation of a simple fan can simplify the calculation model, save calculation time, and achieve the purpose of noise prediction. Comparing the experimental and numerical calculation results of the fan, the errors are all within 5%, indicating that the calculation method is reliable and can accurately simulate the aerodynamic performance and noise of the fan.

[0174] Table 2 Comparison results between experimental test and numerical simulation.

[0175]

[0176] 3 Application of owl-wing blades

[0177] The 40% cross-section airfoil of the long-eared owl's wing has its own unique mid-arc line, so there are many ways to apply the airfoil in the improvement of the fan blade. It can be distributed according to the conventional single arc mid-arc line, or according to its own airfoil mid-arc line. The present invention uses the extracted owl-wing-like airfoil to arrange the owl-wing-like airfoil according to the mid-arc line of the prototype blade, the single arc mid-arc line, and the airfoil mid-arc line. Because of the fixed relationship between the inlet and outlet installation angles of the blade and the mid-arc line, the airfoil mid-arc line is distributed to ensure its original mid-arc line, and to ensure that the inlet installation angle and outlet installation angle of the blade are the same as those of the prototype blade. Therefore, there are four different airfoil arrangements. The four different mid-arc line distributions are as follows: Figure 7 As shown in the figure, four types of owl-wing airfoil are installed as follows Figure 8As shown, the relevant parameters of the impeller are shown in Table 3, where groups 1, 2, 3, and 4 are respectively distributed according to the prototype mid-arc line, the single arc mid-arc line, the mid-arc line of the airfoil with the same inlet installation angle, and the mid-arc line of the airfoil with the same outlet installation angle.

[0178] Table 3 Parameters of prototype and simulated owl-wing impeller

[0179]

[0180] The numerical simulation method is used to calculate the air volume and noise of four fans with owl-wing blades. In order to ensure the comparability of the calculation results, the four different fans with owl-wing blades use the same calculation model, grid division and calculation method. The specific results are shown in Table 4.

[0181] Table 4 Calculation results of the prototype and four types of owl-wing blade fans

[0182]

[0183] From the analysis of Table 4, we can see that different application modes of the owl-wing airfoil have different effects on the aerodynamic performance and noise of the fan. The wind volume of the fan with the owl-wing airfoil and the same mid-arc distribution as the prototype with the blade inlet installation angle increased by 13m 3 / h, but the noise also increased by 0.4dB; the fans using the owl-wing airfoil according to the prototype mid-arc, single arc mid-arc and the same blade outlet angle as the prototype have different degrees of noise reduction while keeping the air volume basically unchanged. Among them, the owl-wing airfoil with the single arc mid-arc distribution has the greatest degree of noise reduction, which can be reduced by 1.7dB compared with the prototype. It can be seen that the application of the owl-wing airfoil in the centrifugal fan can greatly reduce the aerodynamic noise of the fan while ensuring the aerodynamic performance of the fan.

[0184] 5 Test results and noise reduction analysis

[0185] 5.1 Test results

[0186] Based on the numerical simulation, the experimental test method is used to compare and verify the calculation results. ABS material is used to process the prototype of the owl-wing impeller (Group 2) with the best noise reduction effect, that is, the impeller with the owl-wing airfoil distributed in the arc line of a single arc, and the same material as the prototype impeller is maintained, thereby ignoring the influence of the material on the fan performance and noise.

[0187] Table 5 gives the comparison results of experimental test and numerical simulation. It can be seen from Table 5 that both the experimental test and numerical simulation of the fan with owl-wing blades show that the fan air volume remains basically unchanged while the noise is significantly reduced. Compared with the experimental test, the results of numerical simulation show that the air volume of the fan with owl-wing blades is slightly different from the experimental measured air volume, with a relative error of 1.7%, while the relative error of noise is 3.4%. Within the range of engineering allowable error, it can be considered that numerical calculation can quantitatively predict the noise. Through experimental verification, the use of owl-wing airfoil blades can reduce the fan noise by 1.3dB, showing a good noise reduction effect.

[0188] Table 5 Comparison results between experimental test and numerical simulation

[0189]

[0190] 5.2 Internal flow and noise analysis

[0191] The following takes the application of the owl-wing airfoil with the best noise reduction effect as an example to analyze its internal flow and noise reduction mechanism compared with the prototype.

[0192] The analysis shows that the flow conditions of the prototype impeller and the owl-wing impeller are good at the outlet of the volute, and the flow is basically the same, but the flow in the impeller area of ​​the fan with owl-wing blades can better adhere to the blade surface, which is conducive to the stability of the fluid flow. In the impeller area inside the volute, the flow performance of the owl-wing impeller is better. Compared with the prototype blade, the low-speed area of ​​the suction surface is reduced, the flow separation is weakened, and the generation and development of vortices are suppressed. The noise in the macro aspect is the reduction of the broadband noise of the fan.

[0193] The passing frequency of the fan blades is 275Hz, which is basically consistent with the rotation frequency calculated in the figure. The noise shows obvious periodicity with frequency, and the noise shows obvious peaks at the base frequency and the double frequency, which is consistent with the theoretical analysis. It can be seen from the figure that the noise distribution of the fan using owl-wing blades is basically lower than that of the prototype blade fan at each frequency, and the peaks at the base frequency and the double frequency are also lower than the prototype blade fan. The noise peaks at 275Hz, 1375Hz, and 3025Hz are reduced by 1.0dB, 2.2dB, and 3.7dB, respectively. The final numerical calculation result is a noise reduction of 1.7dB, indicating that the fan using owl-wing blades has good low-noise characteristics.

[0194] The 1 / 3 octave spectrum analysis can more clearly reflect the spectrum characteristics of the noise source. Compared with the prototype fan, the fan with owl-wing blades has reduced noise in the entire frequency band. It can be seen that the fan with owl-wing blades has a more obvious noise reduction at frequencies after 600Hz, which is consistent with the phenomenon that owls produce low-noise flight in the medium and low frequency bands. The fan broadband noise and discrete noise are reduced, indicating that the use of owl-wing blades has an improvement effect on the vortex noise caused by flow separation and the rotation noise caused by the unsteady action between the blades and the volute tongue.

[0195] The mean value of the sound pressure pulsation directly reflects the sound source area and clearly shows the contribution of each part to the noise. Since the impeller is an open impeller and the collector outlet is larger than the inner diameter of the impeller, the axial air intake has a greater impact on the end of the impeller front disk. In addition, because the airflow is in the process of axial to radial rotation, the leading edge of the blade is greatly impacted by the airflow. In the figure, the pressure pulsation values ​​at the end of the impeller front disk and the leading edge of the blade are large, which contributes more to the noise. Comparing the prototype blade and the owl-wing blade, it can be found that the use of the owl-wing blade can reduce the pressure pulsation at the leading edge of the blade. Its leading edge structure can make the airflow more smoothly from the axial to radial direction to enter the impeller flow channel, effectively suppressing the noise generated by the pressure pulsation in the leading edge area. It can be seen that the use of the owl-wing blade reduces the pressure pulsation in the volute and volute tongue, and the area with severe local pressure pulsation is reduced, which can weaken the unsteady effect of the blade and the volute tongue.

[0196] 6 Conclusion

[0197] The present invention extracts a 40% cross-section airfoil of a long-eared owl wing with good aerodynamic performance and low noise characteristics, and applies it to the improvement of the blade profile of a centrifugal fan blade for a window air conditioner. The noise reduction effect of different application modes of the owl-like wing airfoil is studied by numerical simulation, and the internal flow and noise reduction mechanism of the best effect are analyzed. The experimental verification is carried out, and the following conclusions are obtained:

[0198] (1) The noise reduction problem of window air conditioners mainly lies in the reduction of fan aerodynamic noise. The numerical calculation model and calculation method established for the centrifugal fan used in window air conditioners can effectively simulate the air volume and noise of the fan.

[0199] (2) Among the four different owl-wing airfoil distributions, the fan with the airfoil distributed according to its own mid-arc line (the blade inlet installation angle is the same as the prototype) has an air volume that is 13m higher than the prototype 3 / h, but the noise also increased by 0.4dB; the fans with airfoils following the prototype mid-arc, single circular mid-arc, and airfoil mid-arc (the blade outlet installation angle is the same as the prototype) all had reduced noise while the air volume remained unchanged. Among them, the fan with airfoils following the single circular mid-arc distribution had reduced noise by 1.3dB through experiments.

[0200] (3) The owl-wing blade fan with the best noise reduction effect was analyzed. It was found that the use of airfoil blades can reduce the low-speed separation area in the impeller flow channel and inhibit the generation and development of vortices. The airfoil leading edge structure can make the airflow more stable from the axial to the radial direction, weaken the pressure pulsation at the leading edge of the blade, effectively inhibit the noise generated by the pressure pulsation in the leading edge area, and reduce the pressure pulsation in the volute and tongue area. The broadband noise and discrete noise of the fan are reduced.

[0201] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0202] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0203] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0204] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0205] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0206] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A blade of a wind wheel, It is characterized in that The blade extends in the front-rear direction, and the blade has a leeward surface located at the upper side and a windward surface located at the lower side, the windward surface is cut by a plane perpendicular to the left-right direction to form a lower surface profile, and the leeward surface is cut by a plane perpendicular to the left-right direction to form an upper surface profile, the lower surface profile includes a lower convex line and an upper concave line, with the line connecting the two end points of the lower surface profile as a reference, the lower convex line is in a shape that at least a portion is convex downward, the upper concave line is in a shape that at least a portion is concave upward, and the upper concave line is located at the rear side of the lower convex line; The dimension L1' of the lower convex line along the front-to-back direction is smaller than the dimension L2' of the upper concave line along the front-to-back direction; L1':L2' is in the range of 1:9 to 1:5; The convex height H1' of the lower convex line is smaller than the concave height H2' of the upper concave line; H1':H2' is in the range of 1:5 to 1:3; The height of the lower convex line is H1', ​​the dimension of the windward surface along the front-rear direction is LY', and H1':LY' is in the range of 0.02 to 0.03; The height of the concave portion of the upper concave line is H2', the dimension of the windward surface along the front-rear direction is LY', and H2':LY' is in the range of 0.08 to 0.

1.

2. The blade of the wind wheel according to claim 1, It is characterized in that L1':L2' is in the range of 1:8 to 1:

6.

3. The blade of the wind wheel according to claim 1, It is characterized in that The distance between the top of the lower convex line and the front end point of the lower convex line in the front-back direction is L3', and the distance between the top of the lower convex line and the rear end point of the lower convex line in the front-back direction is L4', L3'<L4'.

4. The blade of the wind wheel according to claim 3, It is characterized in that L3' / L4' is in the range of 1 / 5 to 1 / 3.

5. The blade of the wind wheel according to claim 1, It is characterized in that The distance between the top of the lower convex line and the front end point of the lower convex line in the front-to-back direction is L3', the dimension of the windward surface along the front-to-back direction is LY', and L3' / LY' is in the range of 0.0125 to 0.

05.

6. The blade of the wind wheel according to claim 1, It is characterized in that The distance between the top of the upper concave line and the front end point of the upper concave line in the front-back direction is L5', and the distance between the top of the upper concave line and the rear end point of the upper concave line in the front-back direction is L6', L5'<L6'.

7. The blade of the wind wheel according to claim 6, It is characterized in that L5' / L6' is in the range of 0.7 to 0.

9.

8. The blade of the wind wheel according to claim 1, It is characterized in that The distance between the top of the upper concave line and the rear end point of the upper concave line in the front-rear direction is L6', the dimension of the windward surface along the front-rear direction is LY', and L6' / LY' is in the range of 0.45 to 0.

55.

9. The blade of a wind wheel according to any one of claims 1 to 8, It is characterized in that The rear end point of the lower convex line is connected to the front end point of the upper concave line; and / or The front end point of the lower convex line extends to the front end point of the windward surface; and / or The rear end point of the upper concave line extends to the rear end point of the windward surface.

10. The blade of a wind wheel according to any one of claims 1 to 8, It is characterized in that The lower convex line and the upper concave line are both cambered surfaces.

11. The blade of a wind wheel according to any one of claims 1 to 8, It is characterized in that The windward surface is a smooth curved surface.

12. The blade of the wind wheel according to claim 1, It is characterized in that At least a portion of the leeward surface is in an upwardly convex shape.

13. The blade of the wind wheel according to claim 12, It is characterized in that The leeward surface is in a shape that extends first upward and then downward from the front end point to the rear end point.

14. The wind wheel blade according to claim 12, It is characterized in that The distance between the top of the leeward surface and the front end point of the leeward surface in the front-rear direction is L7', and the distance between the top of the leeward surface and the rear end point of the leeward surface in the front-rear direction is L8', L7'<L8'.

15. The wind wheel blade according to claim 14, It is characterized in that L7' / L8' is in the range of 1 / 3 to 2 / 3.

16. The blade of the wind wheel according to claim 12, It is characterized in that A ratio H3' / LB' of a maximum height H3' of the leeward surface convexity to a dimension LB' of the leeward surface in the front-rear direction is in the range of 0.14 to 0.

16.

17. The blade of the wind wheel according to claim 12, It is characterized in that A ratio H3' / LB' of a maximum height H3' of the leeward surface convexity to a dimension LB' of the leeward surface in the front-rear direction is in the range of 0.153 to 0.

154.

18. The blade of a wind wheel according to any one of claims 1 to 8 and 12 to 17, It is characterized in that The front end point of the windward surface is connected to the front end point of the leeward surface; and / or The rear end point of the windward surface is connected to the rear end point of the leeward surface.

19. A blade for a wind wheel according to any one of claims 1 to 8 and 12 to 17, It is characterized in that The leeward surface is a smooth curved surface.

20. The blade of the wind wheel according to claim 1, It is characterized in that The leading edge thickness of the blade is greater than the trailing edge thickness of the blade, and the thickness of the blade gradually decreases from the leading edge to the trailing edge.

21. The blade of the wind wheel according to claim 1, It is characterized in that The thickness of the blade increases first and then decreases in the front-to-back direction.

22. The wind wheel blade according to claim 21, It is characterized in that The blade has a maximum thickness at a position with a spacing of 0.1LP to 0.2LP along the front end of the blade, wherein LP is the length of the blade along the front-to-back direction.

23. The blade of the wind wheel according to claim 1, It is characterized in that The blade extends from the leading edge to the trailing edge along a convex arc in the middle portion.

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