Impeller for centrifugal fan and centrifugal fan

Abstract

The present application discloses an impeller for a centrifugal fan and a centrifugal fan. The impeller includes a support and a plurality of blades. The support has an inner wall defining a hollow portion. A plurality of blades are arranged in the hollow portion, each of the plurality of blades is connected to the inner wall and extends in the axial direction of the support. The plurality of blades are arranged in the circumferential direction of the support. Each of the plurality of blades is curved and includes a leading edge, a trailing edge, a convex suction surface and a concave pressure surface, the suction surface and the pressure surface are arranged oppositely, the leading edge and the trailing edge are arranged oppositely, and the trailing edge is connected to the inner wall of the support. A plurality of protrusions are provided on the suction surface, which are arranged close to the leading edge. The protrusions can rectify the fluid as soon as the fluid contacts the blade. In the rectifying process, a large vortex in the fluid will be separated into a plurality of small vortices, and the friction resistance of the small vortex is smaller, which can partially offset the kinetic energy dissipated by the movement of the small vortex itself, thereby reducing the noise of the impeller and improving the performance of the centrifugal fan.

Description

Technical Field

[0001] The present application relates to the field of impellers, and in particular to an impeller for a centrifugal fan. Background Art

[0002] In the prior art, the blades in the impeller are arc-shaped, and the surface of the blades is a smooth curved surface. Since the flow separation on the blade surface is serious and vortices are formed, the aerodynamic performance of the blades is low and the noise is high. Summary of the invention

[0003] Exemplary embodiments of the present application may address at least some of the above-mentioned problems.

[0004] According to the first aspect of the present application, the present application provides an impeller for a centrifugal fan, the impeller comprising a support member and a plurality of blades. The support member is cylindrical and has an inner wall defining a hollow portion. The plurality of blades are arranged in the hollow portion, each of the plurality of blades is connected to the inner wall and extends along the axial direction of the support member, and the plurality of blades are arranged along the circumferential direction of the support member. Wherein, each of the plurality of blades is curved and comprises a leading edge, a trailing edge, a convex suction surface and a concave pressure surface, the suction surface and the pressure surface are arranged oppositely, the leading edge and the trailing edge are arranged oppositely, wherein the trailing edge is connected to the inner wall of the support member. Wherein, the suction surface is provided with a plurality of protrusions, and the plurality of protrusions are arranged close to the leading edge.

[0005] According to the impeller of the first aspect, each of the plurality of blades has a length direction defined along the axial direction of the support and a width direction from the leading edge to the trailing edge. The plurality of protrusions are arranged in a plurality of rows along the width direction, and the protrusions in each row are arranged along the length direction. In the width direction, the protrusions in different rows are arranged staggered with each other.

[0006] According to the impeller of the first aspect, projections of the plurality of protrusions on a plane perpendicular to a radial direction of the support member do not overlap.

[0007] According to the impeller of the first aspect described above, the respective protrusions in each row have the same shape and size.

[0008] According to the impeller of the first aspect, each of the protrusions has a protrusion height, which is the distance between the highest point of the top of the protrusion and the suction surface in the axial cross section of the support. The shape of each of the plurality of protrusions is set to have the highest point of the top, and the highest points of the tops of the protrusions in each row are arranged along a straight line parallel to the axial direction of the support; the distance S between the straight line where the highest points of the tops of the row of protrusions farthest from the leading edge are located and the straight line where the ends of the leading edge are located satisfies the blade width W:

[0009] S = A × W;

[0010] The value range of A is greater than or equal to 1 / 3 and less than or equal to 2 / 5.

[0011] According to the impeller of the first aspect, in each row of protrusions, the highest points of the tops of two adjacent protrusions have the same interval.

[0012] According to the impeller of the first aspect, the plurality of protrusions are arranged such that, in two adjacent rows of protrusions, the height of the protrusions in the row close to the leading edge is not less than the height of the protrusions in the row close to the trailing edge.

[0013] According to the impeller of the first aspect, the tops of the plurality of protrusions have lower portions located around the highest point.

[0014] According to the impeller of the first aspect, each of the plurality of protrusions is partially spherical, olive-shaped or teardrop-shaped.

[0015] According to a second aspect of the present application, the present application provides a centrifugal fan comprising the above-mentioned impeller.

[0016] The protrusions on the impeller of the present application can rectify the fluid as soon as the fluid contacts the blades, and after rectification, no other protrusions contact the rectified fluid, thereby preventing the fluid from being disturbed again. During the rectification process, the large vortex in the fluid will be separated into several small vortices, the upper direction of the vortex is consistent with the direction of fluid movement, and the bottom direction is opposite to the direction of fluid movement. The friction resistance of this small vortex is smaller, which can partially offset the kinetic energy dissipated by the movement of the small vortex itself, thereby reducing the noise of the impeller and improving the performance of the centrifugal fan. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The features and advantages of the present application may be better understood by reading the following detailed description with reference to the accompanying drawings, in which like reference numerals refer to like components throughout, wherein:

[0018] Figure 1 is a three-dimensional diagram of the centrifugal fan of the present application;

[0019] Figure 2 yes Figure 1 A perspective view of the impeller shown;

[0020] Figure 3 yes Figure 2 A perspective view of the blade shown;

[0021] Figure 4 yes Figure 3 A top view of a first embodiment of a blade is shown wherein the projection is partially spherical;

[0022] Figure 5A-5B yes Figure 4 A radial cross-section of the blade shown;

[0023] Figure 6 is a top view of a second embodiment of a blade of the present application, wherein the protrusion is olive-shaped;

[0024] Figure 7 It is an enlarged view of the olive-shaped protrusion;

[0025] Figure 8 is a top view of a third embodiment of the blade of the present application, wherein the protrusion is in the shape of a water drop;

[0026] Fig. 9 It is an enlarged view of the teardrop-shaped protrusion;

[0027] Fig. 10A This is a simulation diagram of turbulent kinetic energy of an impeller without a protrusion;

[0028] Figures 10B-10D These are the turbulent kinetic energy simulation diagrams of impellers with partially spherical protrusions, olive-shaped protrusions, and water drop-shaped protrusions. DETAILED DESCRIPTION

[0029] Various specific embodiments of the present invention will be described below with reference to the accompanying drawings that form a part of this specification. It should be understood that although terms indicating directions, such as "front", "rear", "upper", "lower", "left", "right", etc., are used in the present invention to describe various example structural parts and elements of the present invention in a directional or orientational manner, these terms are used here only for the purpose of convenience of description and are determined based on the example orientations shown in the accompanying drawings. Since the embodiments disclosed in the present invention can be set in different directions, these directional terms are only used as illustrations and should not be regarded as limitations. In the following drawings, the same parts use the same figure numbers, and similar parts use similar figure numbers.

[0030] Figure 1 1 is a perspective view of the centrifugal fan 100 of the present application. Figure 1As shown, the centrifugal fan 100 includes a volute 101, an impeller 102 and a driving device 103. Specifically, the volute 101 is substantially cylindrical and has a volute hollow portion. An air inlet channel is provided on the left and right sides of the volute 101, and an air outlet channel is provided at the rear of the circumference of the volute 101. The impeller 102 is accommodated in the volute hollow portion of the volute 101. The impeller 102 is substantially cylindrical and has a rotation axis X. The driving device 103 is arranged on the left side of the volute 101, and the driving shaft of the driving device 103 is coaxially arranged with the rotation axis X of the impeller 102. The driving shaft of the driving device 103 is connected to the impeller 102 to drive the impeller 102 to rotate. When the driving device 103 is started, the impeller 102 rotates around the rotation axis X, and the fluid (for example, wind) can enter the volute 101 from the air inlet channels on the left and right sides, and then be discharged from the air outlet channel at the rear of the volute 101.

[0031] Figure 2 yes Figure 1 The three-dimensional view of the impeller 102 is shown. Figure 2 As shown, the impeller 102 includes a support member 201. The support member 201 is cylindrical and has an inner wall 212 that defines a hollow portion of the support member. Specifically, the support member 201 includes a first ring 221, a second ring 222, a third ring 223, a plurality of first support rods 224, and a plurality of second support rods 225. The plurality of first support rods 224 are disposed between the first ring 221 and the second ring 222, and the left end of each of the plurality of first support rods 224 is connected to the first ring 221, and the right end of each of the plurality of first support rods 224 is connected to the second ring 222. The plurality of first support rods 224 are evenly arranged along the circumferential direction of the support member 201. There is a spacing between the plurality of first support rods 224. Similarly, several second support rods 225 are arranged between the second ring 222 and the third ring 223, and the left end of each of the several second support rods 225 is connected to the second ring 222, and the right end of each of the several second support rods 225 is connected to the third ring 223. Several second support rods 225 are evenly arranged along the circumferential direction of the support member 201. There is a spacing between the several second support rods 225. The number of the several first support rods 224 and the several second support rods 225 is the same, and the several first support rods 224 and the several second support rods 225 are arranged accordingly. In other words, each of the several first support rods 224 and the corresponding second support rod 225 are arranged on the same straight line, which is parallel to the rotation axis X of the impeller 102. It should be noted that, although each of the several first support rods 224 and the corresponding second support rod 225 are arranged on the same straight line in the present application, those skilled in the art can understand that each of the several first support rods 224 and the corresponding second support rod 225 can also be arranged at a certain angle.

[0032] like Figure 2 As shown, the impeller 102 further includes a plurality of blades 202. Each of the plurality of blades 202 is connected to the inner wall 212. The plurality of blades 202 are formed to extend along the circumferential direction of the support member 201. The number of the plurality of blades 202 is set corresponding to the number of the plurality of first support rods 224 and the plurality of second support rods 225. That is, the blades 202 are set on the inner wall 212 of the first support rod 224 and the second support rod 225.

[0033] In the example of the present application, the impeller 102 is an impeller with air intake from both sides. Those skilled in the art can understand that for an impeller with air intake from one side (i.e., the left side or the right side), only two support rings and a number of blades 202 arranged between the two support rings are required. Therefore, each of the several blades 202 described below refers to a blade 202 arranged between the first ring 221 and the second ring 222 or a blade 202 arranged between the second ring 222 and the third ring 223.

[0034] Figure 3 yes Figure 2 The perspective view of the first embodiment of the blade 202 is shown to illustrate the specific structure of the blade 202. Figure 3 As shown, the blade 202 is curved. It includes a leading edge 301, a trailing edge 302, a suction surface 305 and a pressure surface 306. The leading edge 301 and the trailing edge 302 are arranged opposite to each other. The trailing edge 302 is connected to the inner wall 212 (for example, the first support rod 224 and / or the second support rod 225) of the support member 201. The suction surface 305 and the pressure surface 306 are arranged opposite to each other. The suction surface 305 is convex, while the pressure surface 306 is concave. The blade 202 has a blade length L defined along the axial direction of the support member 201 and a blade width W from the leading edge 301 to the trailing edge 302. Several protrusions 311 are provided on the suction surface 305, and the several protrusions 311 are arranged close to the leading edge 301. The protrusion 311 can be in a variety of shapes, such as partially spherical, olive-shaped or water drop-shaped.

[0035] Figure 4 yes Figure 3 The top view of the blade 202 is shown. Figure 5A-5B yes Figure 4 The radial cross-sectional view of the blade 202 is shown to further illustrate the specific structure of the blade 202 and the plurality of protrusions 311. Figure 4-5B As shown, several protrusions 311 are arranged in three rows along the width direction of the blade 202, and the protrusions 311 in each row are arranged along the length direction of the blade 202. In the width direction of the blade 202, the protrusions 311 in different rows are arranged staggered with each other. Figure 4As shown in the enlarged view in , the dotted lines represent the projections of each protrusion 311 in the length direction (i.e., in a radial plane perpendicular to the support member 201). It can be seen from the enlarged view that the projections of each protrusion 311 in the length direction are non-overlapping. When the fluid enters the impeller 102 from the air inlet channel, the fluid will first contact the leading edge 301 of the blade 202 and flow toward the trailing edge 302. The several protrusions 311 arranged near the leading edge 301 can rectify the fluid, separate the large vortex generated by the rotation into several small vortices, and after the protrusions 311 arranged closer to the leading edge 301 (i.e., the front row) contact the fluid, the protrusions 311 closer to the trailing edge 302 (i.e., the rear row) will not contact the fluid that has been rectified by the protrusions 311 near the leading edge 301 again. This can make the fluid velocity distribution in the impeller 102 more uniform.

[0036] like Figure 4-5B As shown, the shapes of the protrusions 311 provided on the suction surface 305 are the same, but the protrusions 311 located in different rows may have different sizes. Specifically, the protrusion 311 has a top. The top includes a highest point and a lower portion located around the highest point. The highest point of the top of the protrusion 311 is located in the middle of the protrusion 311, so that there is a smoother transition from the highest point to the suction surface 305. On the axial cross-section of the support member 201, the distance between the highest point of the top and the suction surface 305 is farther than the distance between any other point on the protrusion 311 and the suction surface 305. Since the protrusion 311 is a symmetrical figure, the highest point of the top is located on the geometric center axis of the protrusion 311. The geometric center axis of the protrusion 311 is arranged perpendicular to the suction surface 305. As shown Figure 5A As shown, the highest points of the tops of the protrusions 311 in each row are arranged along a straight line parallel to the axial direction of the support member 201. The distance S between the straight line where the highest points of the tops of the protrusions 311 in the row farthest from the leading edge 301 (i.e., the last row) are located and the straight line where the ends of the leading edge 301 are located satisfies the blade width W:

[0037] S = A × W;

[0038] The value range of A is greater than or equal to 1 / 3 and less than or equal to 2 / 5.

[0039] The distance between the straight line where the highest point of the top of each protrusion 311 in the first row is located and the end of the front edge 301 is distance S1, and the distance between the straight line where the highest point of the top of each protrusion 311 in the second row is located and the straight line where the highest point of the top of each protrusion 311 in the third row is distance S2. Wherein, distance S, distance S1 and distance S2 satisfy:

[0040] S1=B×S,

[0041] The value range of B is greater than or equal to 1 / 4 and less than or equal to 1 / 3.

[0042] The distance between the highest point of the top of each protrusion 311 and the suction surface 305 is the protrusion height H. The protrusion height H of each protrusion 311 in each row is the same. Among them, the protrusion 311 closest to the leading edge 301 is the first row, and the protrusion height of each protrusion 311 in the first row is H1. The protrusion height of each protrusion 311 in the second row is H2. The protrusion height of each protrusion 311 in the third row is H3. Several protrusions 311 are configured as follows: in two adjacent rows of protrusions 311, the protrusion height of a row of protrusions 311 close to the leading edge 301 is not less than the protrusion height of a row of protrusions 311 close to the trailing edge 302. That is, in two adjacent rows of protrusions 311, the protrusion height of a row of protrusions 311 close to the leading edge 301 is greater than or equal to the protrusion height of a row of protrusions 311 close to the trailing edge 302. The height of the protrusions 311 arranged near the trailing edge 302 should not exceed the height of the protrusions of a row of protrusions 311 near the leading edge 301 , which can prevent the protrusions 311 from generating additional vortices.

[0043] As an example, the protrusion height H1, the protrusion height H2, and the protrusion height H3 satisfy:

[0044] H1≤0.25mm; H2=C×H1; H3=D×H2;

[0045] Among them, the value range of C is greater than or equal to 0.9 and less than or equal to 1, and the value range of D is greater than or equal to 0.9 and less than or equal to 1.

[0046] As described above, the protrusion 311 can be in various shapes, such as a partially spherical shape, an olive shape, or a teardrop shape. As a first embodiment, Figure 4-5B The protrusion 311 shown in the figure is partially spherical. Specifically, the partially spherical protrusion 311 has a spherical diameter D, and the spherical diameter D of each protrusion 311 in each row is the same. Among them, the protrusion 311 closest to the leading edge 301 is the first row, and the spherical diameter of each protrusion 311 in the first row is D1. The spherical diameter of each protrusion 311 in the second row is D2. The spherical diameter of each protrusion 311 in the third row is D3. The spherical diameter D1, the spherical diameter D2 and the spherical diameter D3 satisfy:

[0047] D1=E×W; D2=F×D1; D3=G×D2;

[0048] Among them, the value range of E is greater than or equal to 0.06 and less than or equal to 0.08, the value range of F is greater than or equal to 0.9 and less than or equal to 1, and the value range of G is greater than or equal to 0.9 and less than or equal to 1.

[0049] In addition, for the protrusions 311 in the same row, the protrusions 311 are evenly spaced along the length direction of the blade 202. The distance between the highest points of the tops of two adjacent protrusions 311 is M. The distance M satisfies:

[0050] M=4×D1.

[0051] Figure 6 3 is a top view of the second embodiment of the blade 202 of the present application, wherein the protrusion 311 is olive-shaped. Figure 7 is an enlarged view of the olive-shaped protrusion 311, and relative to Figure 6 The protrusion 311 shown is rotated 90°. Specifically, the edge of the olive-shaped protrusion 311 includes a first edge 701 located at the left and right parts and a second edge 702 located at the upper and lower parts. The first edge 701 and the second edge 702 are both arcs, and the radius of the first edge 701 is R1, and the radius of the second edge 702 is R2. The edge of the olive-shaped protrusion 311 is symmetrical with respect to the axis X and the axis Y. The intersection of the axis X and the axis Y is O, which is the highest point of the top of the protrusion 311. The center O1 of the radius R1 of the first edge 701 is located on the axis X, and the distance from the intersection O is L1. The center O2 of the radius R2 of the second edge 702 is located on the axis Y, and the distance from the intersection O is L2. The radius R1 of the first edge 701, the distance L1 between the center O1 and the intersection O, the radius R2 of the second edge 702, and the distance L2 between the center O2 and the intersection O satisfy:

[0052] R1=K1×W; L1=K2×W; R2=K3×W; L2=K4×W;

[0053] Among them, the value range of K1 is greater than 0.5 and equal to and less than or equal to 1.2, the value range of K2 is greater than or equal to 0.07 and less than or equal to 0.09, the value range of K3 is greater than 0 and less than or equal to 0.04, and the value range of K4 is greater than 0.05 and less than or equal to 0.07.

[0054] In addition, for the protrusions 311 in the same row, the protrusions 311 are evenly spaced along the length direction of the blade 202. The distance between the highest points of the tops of two adjacent protrusions 311 is M. The distance M satisfies:

[0055] M=8×(R1-L1).

[0056] Figure 8 3 is a top view of the blade 202 of the third embodiment of the present application, wherein the protrusion 311 is in the shape of a water drop. Fig. 9 is an enlarged view of the teardrop-shaped protrusion 311, and relative to Figure 8 The protrusion 311 shown is rotated 90°. Specifically, the edges of the teardrop-shaped protrusion 311 include a first edge 901 located on the left, a second edge 902 located on the upper and lower parts, and a third edge 903 located on the right. The first edge 901 and the second edge 902 are both arcs, and the radius of the first edge 901 is R1, and the radius of the second edge 902 is R2. The third edge 903 is a straight line. The edges of the teardrop-shaped protrusion 311 are symmetrical with respect to the axis X. The center of the circle of the radius R1 of the first edge 901 is O, which is the highest point of the top of the protrusion 311 and is located on the axis X. The angle formed by the third edge 903 on the right and the axis X is φ. The value range of the angle φ is greater than or equal to 8° and less than or equal to 20°. The length of the third edge 903 is L. The radius R1 of the first edge 901, the radius R2 of the second edge 902, and the length L of the third edge 903 satisfy:

[0057] R1=J1×W; R2=J2×W; L=J3×W;

[0058] Among them, the value range of J1 is greater than 0.04 and equal to and less than or equal to 0.05, the value range of J2 is greater than or equal to 0.3 and less than or equal to 0.52, and the value range of J3 is greater than or equal to 0.05 and less than or equal to 0.07.

[0059] In addition, for the protrusions 311 in the same row, the protrusions 311 are evenly spaced along the length direction of the blade 202. The distance between the highest points of the tops of two adjacent protrusions 311 is M. The distance M satisfies:

[0060] M=8×R1.

[0061] Fig. 10A This is a simulation diagram of the turbulent kinetic energy of an impeller without a protrusion. Figures 10B-10D These are the turbulent kinetic energy simulation diagrams of the impellers with partially spherical protrusions, olive-shaped protrusions, and water drop-shaped protrusions. It can be seen from the figure that Fig. 10A The turbulent kinetic energy of the impeller in is the largest. Figures 10B-10D The turbulent kinetic energy shown in is small. After calculation and analysis, under the same air volume and speed, the turbulent kinetic energy of the impeller without protrusions is approximately 1.2KJ, while the turbulent kinetic energy of the impeller with partially spherical protrusions, olive-shaped protrusions and water drop-shaped protrusions are 1.11KJ, 1.1KJ and 1.12KJ respectively. Compared with the impeller without protrusions, its turbulent kinetic energy can be reduced by about 10%.

[0062] In addition, compared to setting the protrusion at other positions of the blade, the protrusion set near the leading edge 301 can rectify the fluid as soon as the fluid contacts the blade, and after the rectification, no other protrusion contacts the rectified fluid, thereby preventing the fluid from being disturbed again. During the rectification process, the large vortex in the fluid will be separated into several small vortices, the upper direction of the vortex (close to the leading edge 301) is consistent with the direction of fluid movement, and the bottom direction (close to the trailing edge 302) is opposite to the direction of fluid movement. The friction resistance of this small vortex is smaller, which can partially offset the kinetic energy dissipated by the movement of the small vortex itself, thereby reducing the noise of the impeller and improving the performance of the centrifugal fan.

[0063] It should be noted that, although three rows of protrusions are shown in the present application, any number of rows of protrusions are within the protection scope of the present application.

[0064] Although only some features of the present application have been illustrated and described herein, various modifications and changes may be made to those skilled in the art. Therefore, it should be understood that the appended claims are intended to cover all the above modifications and changes that fall within the spirit and scope of the present application.

Claims

1. An impeller for a centrifugal fan, characterized in that: The impeller comprises: A support member (201), the support member (201) is cylindrical and has an inner wall (212) defining a hollow portion (211); and a plurality of blades (202), the plurality of blades (202) being arranged in the hollow portion (211), each of the plurality of blades (202) being connected to the inner wall (212) and extending along the axial direction of the support member (201), and the plurality of blades (202) being arranged along the circumferential direction of the support member (201); Each of the plurality of blades (202) is curved and comprises a leading edge (301), a trailing edge (302), a convex suction surface (305) and a concave pressure surface (306); the suction surface (305) and the pressure surface (306) are arranged opposite to each other, the leading edge (301) and the trailing edge (302) are arranged opposite to each other, and the trailing edge (302) is connected to the inner wall (212) of the support member (201); Wherein, the suction surface (305) is provided with a plurality of protrusions (311), and the plurality of protrusions (311) are arranged close to the leading edge (301); Each of the plurality of blades (202) has a length direction defined along the axial direction of the support member (201) and a width direction from the leading edge (301) to the trailing edge (302); The plurality of protrusions (311) are arranged in a plurality of rows along the width direction, and the protrusions (311) in each row are arranged along the length direction; The projections of the plurality of protrusions (311) on a plane perpendicular to the radial direction of the support member (201) do not overlap.

2. The impeller for a centrifugal fan according to claim 1, characterized in that: The protrusions (311) in each row have the same shape and size.

3. The impeller for a centrifugal fan according to claim 1, characterized in that: Each of the protrusions (311) has a protrusion height, and the protrusion height is the distance between the highest point of the top of the protrusion (311) and the suction surface (305) on the axial cross section of the support member (201); The shape of each of the plurality of protrusions (311) is configured to have a highest point on the top, and the highest points of the tops of the protrusions (311) in each row are arranged along a straight line parallel to the axial direction of the support member (201); the distance S between the straight line where the highest points of the tops of the row of protrusions (311) farthest from the leading edge (301) are located and the straight line where the ends of the leading edge (301) are located and the blade width W satisfy: S = A × W; The value range of A is greater than or equal to 1 / 3 and less than or equal to 2 / 5.

4. The impeller for a centrifugal fan according to claim 3, characterized in that: In each row of protrusions (311), the highest points of the tops of two adjacent protrusions (311) have the same interval.

5. The impeller for a centrifugal fan according to claim 3, characterized in that: The plurality of protrusions (311) are arranged such that, in two adjacent rows of protrusions (311), the height of the protrusions in a row of protrusions (311) close to the leading edge (301) is not less than the height of the protrusions in a row of protrusions (311) close to the trailing edge (302).

6. The impeller for a centrifugal fan according to claim 3, characterized in that: The tops of the plurality of protrusions (311) have lower portions located around the highest point.

7. The impeller for a centrifugal fan according to claim 2, characterized in that: Each of the plurality of protrusions (311) is partially spherical, olive-shaped or teardrop-shaped.

8. The impeller for a centrifugal fan according to claim 1, characterized in that: The plurality of protrusions (311) are arranged closer to the leading edge (301) than to the trailing edge (302).

9. A centrifugal fan, characterized in that: The centrifugal fan comprises an impeller according to any one of claims 1-7.

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