Axial flow impeller and axial flow fan

Abstract

The axial flow impeller comprises a hub rotating around the axis and a plurality of blades distributed in the circumferential direction of the hub, in the axial direction from the air outlet side to the air inlet side, the diameter of the hub is gradually reduced, the front edges of the blades are close to the air inlet side, and the rear edges of the blades are close to the air outlet side. And the contact surfaces of the roots of the blades and the peripheral surface of the hub are arc-shaped. The axial flow impeller can control secondary flow and flow separation on the suction surface and the pressure surface, flow loss is reduced, and aerodynamic performance is improved; meanwhile, the front edge and the rear edge of each blade can have a good airflow guiding effect, fluid impact and energy loss on the inlet side of the axial flow impeller are reduced, and the performance of the impeller is improved.

Description

Technical Field

[0001] This application relates to the technical field of axial flow impellers, and particularly to an axial flow impeller and an axial flow fan. Background Art

[0002] The three-dimensional geometry of an axial flow impeller determines its aerodynamic performance. It consists of a hub, blades, and an additional structure on the crown side. A good geometry can improve the uniformity of the airflow passing through the impeller, thereby reducing the aerodynamic losses when the airflow enters, passes through, and exits the impeller.

[0003] Most existing axial flow impellers adopt a single plate form or curved blades with equal thickness. This causes the movement of the fluid on the pressure side and suction side of the blade to be restricted to a single path, resulting in separation or large eddies, leading to a decrease in the energy loss efficiency. In fact, the path of the fluid when passing through the impeller is relatively complex, rather than a neat linear single form. This requires the pressure side and suction side of the blade to exhibit different characteristics to adapt to the fluid flow path, suppress the secondary flow in the flow channel, reduce the flow loss, and improve the aerodynamic performance. Summary of the Invention

[0004] The purpose of this application is to provide an axial flow impeller and an axial flow fan, which can control the secondary flow and flow separation on the suction side and pressure side, reduce the flow loss, and improve the aerodynamic performance.

[0005] To achieve the above purpose, this application provides an axial flow impeller, including a hub rotating around an axis and a plurality of blades distributed circumferentially on the hub. In the axial direction of the hub from the air outlet side to the air inlet side, the diameter of the hub gradually decreases. The leading edge of the blade is close to the air inlet side, the trailing edge of the blade is close to the air outlet side, and the contact surface between the root of the blade and the outer peripheral surface of the hub is arc-shaped.

[0006] Preferably, in the projection of the blade onto the plane where the axis is located along the rotation direction of the hub, the projected profile of the blade includes a crown profile line, a leading edge profile line, a trailing edge profile line, and a hub surface profile line;

[0007] The leading edge profile line intersects the crown profile line and the hub surface profile line at point A and point B respectively. The trailing edge profile line intersects the crown profile line and the hub surface profile line at point C and point D respectively. The included angle between the tangent line of the leading edge profile line at point A and the tangent line at point B is greater than 120° and less than 180°. The included angle between the tangent line of the trailing edge profile line at point C and the tangent line at point D is greater than 120° and less than 180°;

[0008] The hub surface contour line is a parabola, and the included angle between the tangent line of the hub surface contour line at point B and the axis is greater than 15° and less than 30°.

[0009] Preferably, the axis of symmetry of the parabola is perpendicular to the axis, the shroud contour line is parallel to the axis, and the trailing edge contour line is closer to the vertex of the parabola than the leading edge contour line.

[0010] Preferably, the leading edge contour line and the trailing edge contour line are spline curves or circular arc lines, and on the axis direction, both the leading edge contour line and the trailing edge contour line bulge toward the side of the vertex.

[0011] Preferably, the formula of the parabola is defined as:

[0012] ;

[0013] where, the absolute value of a is greater than , less than ; b and c are constants, and x and y are the curve coordinates of the parabola.

[0014] Preferably, the trailing edge intersects the outer peripheral surface of the hub at a preset point, the trailing edge extends away from the hub, in the projection of any blade along the axial direction of the hub, the projected preset point is defined as point E, the projected trailing edge is defined as the trailing edge projection line, the connection line between point E and the hub axis is defined as the first connection line, and any point F other than point E on the trailing edge projection line is selected, and the connection line between point F and the hub axis is defined as the second connection line;

[0015] The second connection line is located on the first side of the first connection line, and the included angle between the first connection line and the second connection line is the stacking angle θ. As point F gradually moves away from point E on the path where the trailing edge projection line is located, the stacking angle θ gradually increases.

[0016] Preferably, between point E and the middle of the trailing edge projection line, as point F gradually moves away from point E on the path where the trailing edge projection line is located, the increasing rate of the stacking angle θ gradually decreases;

[0017] Between the middle of the trailing edge projection line and the top of the trailing edge projection line, as point F gradually moves away from point E on the path where the trailing edge projection line is located, the increasing rate of the stacking angle θ gradually increases.

[0018] Preferably, the fitting curve of the leading edge of the blade falls within the surface equation:

[0019] ;

[0020] where, , , , ; , , where x and y are the curve coordinates of the leading edge fitting curve.

[0021] Preferably, when the contact surface is projected onto the plane where the axis is located along the rotation direction of the hub, it is a parabola;

[0022] In the projection of the trailing edge along the axial direction of the hub, the included angle between the line connecting the root of the trailing edge and the hub axis and the line connecting a point on the trailing edge and the hub axis gradually increases in the extending direction of the trailing edge;

[0023] The leading edge fitting curve of the blade falls within a preset curve equation.

[0024] An axial flow fan includes the above-mentioned axial flow impeller.

[0025] Compared with the prior art, in this application, by optimizing the structure of the hub, the axial flow impeller shows a better pressure increasing effect, thereby improving the aerodynamic performance; by optimizing the structure of the blade, the secondary flow and flow separation on the suction surface and the pressure surface are controlled, the flow loss is reduced, and the aerodynamic performance is improved. At the same time, the leading and trailing edges of the blade can show a better air flow guiding effect, reducing the fluid impact and energy loss on the inlet side of the axial flow impeller and improving the impeller performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0027] Figure 1 It is a schematic diagram of the structure of the meridian plane region provided by the embodiment of the present application;

[0028] Figure 2 It is a schematic diagram of the shape of the meridian plane region provided by the embodiment of the present application;

[0029] Figure 3 It is a simulation schematic diagram of the air flow efficiency with respect to angle β and angle φ provided by the embodiment of the present application;

[0030] Figure 4 It is a three-dimensional structure schematic diagram of the axial flow impeller provided by the embodiment of the present application;

[0031] Figure 5Axial projection schematic diagram of the axial flow impeller provided by the embodiment of the present application;

[0032] Figure 6 Schematic diagram of the simulated variation of the stacking angle θ provided by the embodiment of the present application;

[0033] Figure 7 Side view of the axial flow impeller provided by the embodiment of the present application;

[0034] Figure 8 Schematic diagram of the fitting of the blade edge curve provided by the embodiment of the present application;

[0035] Figure 9 Schematic diagram of the fitting of the leading edge curve provided by the embodiment of the present application.

[0036] In the figure: 1 - hub; 2 - blade; 3 - plane; 4 - meridional plane region;

[0037] 21 - leading edge; 22 - blade crown; 23 - trailing edge; 24 - pressure surface; 25 - suction surface;

[0038] 41 - leading edge contour line; 42 - blade crown contour line; 43 - trailing edge contour line; 44 - hub surface contour line;

[0039] 51 - leading edge projection line; 52 - blade crown projection line; 53 - trailing edge projection line;

[0040] 61 - leading edge fitting curve; 62 - blade crown fitting curve; 63 - trailing edge fitting curve. Detailed implementation manners

[0041] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0042] It should be noted that in this embodiment, the orientation or positional relationship indicated by "upper", "lower", "front", "rear", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation to the present application. In addition, "first", "second", "third", "fourth" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0043] In order to enable those skilled in the art of this technology to better understand the solution of the present application, the present application will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0044] As Figure 1 shown, in this embodiment, an axial-flow impeller is provided. The axial-flow impeller includes a hub 1 that rotates around an axis and a plurality of blades 2 distributed circumferentially on the hub 1. The blades 2 are integrally connected to the hub 1, and the blades 2 and the hub 1 can rotate together around the above-mentioned axis. Among them, the blades 2 are usually evenly distributed on the outer peripheral surface of the hub 1, having high dynamic balance and flow field stability; of course, the blades 2 can also be unevenly distributed on the outer peripheral surface of the hub 1, which can adapt to complex working conditions and reduce resonance; details are not described one by one here, and all fall within the protection scope of this application.

[0045] In the axial direction of the hub 1 from the air outlet side to the air inlet side, the diameter of the hub 1 gradually decreases. The root of the blade 2 contacts the outer peripheral surface of the hub 1. The leading edge 21 of the blade 2 is close to the air inlet side, the trailing edge 23 of the blade 2 is close to the air outlet side, and the length of the leading edge 21 is greater than the length of the trailing edge 23. The contact surface between the root of the blade 2 and the outer peripheral surface of the hub 1 is arc-shaped. Further, along the rotation direction of the hub 1, the projection of the above contact surface onto the plane 3 where the axis of the hub 1 is located is a parabola.

[0046] Further, in the projection of the blade 2 onto the plane 3 where the axis is located along the rotation direction of the hub 1, please refer to Figure 1 , the blade 2 will form a projection area on this plane 3. This projection area is defined as the meridian plane area 4. The boundary of this area includes the shroud contour line 42 as the upper boundary, the leading edge contour line 41 as the front boundary, the trailing edge contour line 43 as the rear boundary, and the hub surface contour line 44 as the lower boundary. The middle flow domain surrounded by the four contour lines is the meridian plane area 4 through which the fluid flows.

[0047] Among them, the shroud contour line 42 is the contour line formed by the projection of the shroud 22 of the blade 2, the leading edge contour line 41 is the contour line formed by the projection of the leading edge 21 of the blade 2, the trailing edge contour line 43 is the contour line formed by the projection of the trailing edge 23 of the blade 2, and the hub surface contour line 44 is the contour line formed by the projection of the outer surface of the hub 1. The contour line refers to the boundary line of the projected shape, that is, the projections of the shroud 22, the leading edge 21, the trailing edge 23, and the outer surface of the hub 1 respectively serve as the boundary lines of the meridian plane area 4.

[0048] Please refer to Figure 2 , Figure 2It is a schematic diagram of the shape of the meridional plane region 4. It can be seen that the leading edge contour line 41 intersects with the shroud contour line 42 and the hub surface contour line 44 at point A and point B respectively. The included angle β formed by the tangents of the leading edge contour line 41 at point A and at point B satisfies 120° < β < 180°; the trailing edge contour line 43 intersects with the shroud contour line 42 and the hub surface contour line 44 at point C and point D respectively. The included angle φ formed by the tangents of the trailing edge contour line 43 at point C and at point D satisfies 120° < φ < 180°. For β and φ within the above angle ranges, please refer to Figure 3 , the air flow efficiency is significantly improved. Therefore, within this angle range, the setting methods of the leading edge 21 and the trailing edge 23 can exhibit better air flow guiding effects. Further, when β = 150° and φ = 150°, the corresponding efficiency is the highest.

[0049] In addition, in this embodiment, the hub surface contour line 44 is the above-mentioned parabola, which can enable the axial flow impeller to exhibit better diffusing effects, thereby improving the aerodynamic performance; and the hub 1 is an axisymmetric component about the axis, that is, the outer surface of the hub 1 has the same parabola characteristics. The included angle α formed by the tangent of the hub surface contour line 44 at point B and the axis satisfies 15° < α < 30°; within this angle range, the fluid impact and energy loss on the inlet side of the axial flow impeller are reduced, and the performance of the axial flow impeller is improved. Through the above design of the meridional plane region 4, the secondary flow and flow separation on the suction surface 25 and the pressure surface 24 can be controlled, the flow loss can be reduced, and the aerodynamic performance can be improved.

[0050] In some embodiments, the shroud contour line 42 is arranged parallel to the axis. The leading edge contour line 41 and the trailing edge contour line 43 are located outside the parabola. Specifically, the leading edge contour line 41 and the trailing edge contour line 43 of the parabola are located between the shroud contour line 42 and the hub surface contour line 44. At the same time, the trailing edge contour line 43 is arranged closer to the vertex of the parabola compared to the leading edge contour line 41. It can be seen that the leading edge contour line 41 is closer to the air inlet side of the axial flow impeller, and compared with the trailing edge contour line 43, the leading edge contour line 41 is longer. Therefore, the leading edge 21 can generate a greater thrust, which can make the air flow more smooth between the impellers and have a higher efficiency. And the shorter trailing edge contour line 43 can make the air flow out more smoothly, ensuring the aerodynamic performance.

[0051] It should be noted that the hub surface contour line 44 is not a complete parabola, but a section is selected from the complete parabola, and the axis of symmetry of the parabola is perpendicular to the axis. Please refer to Figure 2 , the diameters at both axial ends of the hub 1 are different, and the end with the smaller diameter is oriented towards the air inlet side; through the above setting method, the impact of the hub 1 on the air flow can be reduced and the efficiency can be improved. And the hub 1 is an axisymmetric structure about the axis, which can enable the hub 1 to rotate stably around the axis, and the hub 1 and the blades 2 correspondingly arranged on the hub 1 can rotate smoothly, avoiding separation or large eddies.

[0052] Please refer to Figure 2 , the leading edge contour line 41 and the trailing edge contour line 43 are spline curves or circular arc lines. In the axial direction, both the leading edge contour line 41 and the trailing edge contour line 43 bulge towards the vertex side; or rather, compared with the leading edge contour line 41, the line connecting points A and B is closer to the air inlet side, while the vertex of the parabola is closer to the air outlet side. The leading edge 21 can more easily cut the air and reduce the impact of the air on the leading edge 21. Similarly, compared with the trailing edge contour line 43, the line connecting points C and D is closer to the air inlet side.

[0053] The parabolic formula constructed by the above hub surface contour line 44 is defined as:

[0054] ;

[0055] where the absolute value of a is greater than , less than ; b and c are constants, and x and y are the curve coordinates of the parabola. It should be noted that the range of a includes . The positive or negative value of a only determines the opening direction of the parabola, and there is no excessive restriction here. It is only necessary to ensure that the shape of the parabola falls within the range defined by the above formula. Based on the equation of the above parabola and in combination with the value range of the angle α, the axial flow impeller can exhibit the optimal diffusing effect, thereby improving the overall aerodynamic performance.

[0056] Please refer to Figure 4 and Figure 5 , in the axial projection of the trailing edge 23 along the hub 1, the included angle between the line connecting the root of the trailing edge 23 and the axis of the hub 1 and the line connecting a point on the trailing edge 23 and the axis of the hub 1 gradually increases in the extending direction of the trailing edge 23; specifically, in the axial projection of the blade 2 along the hub 1, the area formed by the projection includes the crown projection line 52 as the upper boundary, the leading edge projection line 51 as the front boundary, the trailing edge projection line 53 as the rear boundary, and the hub projection line as the lower boundary. That is, the above projection lines also belong to the contour lines. It should be noted that in three-dimensional space, the root of the trailing edge 23 is not set at the boundary of the outer peripheral surface of the hub 1, but compared with a preset point on the outer peripheral surface. Therefore, in the axial projection, affected by the parabolic structure of the hub 1, the projection of the hub 1 will block the preset point and part of the projection line of the trailing edge 23. Similarly, the projection of the hub 1 will also block part of the projection line of the leading edge 21 and part of the area at the root of the blade 2.

[0057] For more accurate description, the above preset point is defined as point E in the axial projection. Please refer to Figure 5, the trailing edge 23 extends away from the hub 1. In the projection, the trailing edge 23 is defined as the trailing edge projection line 53. The trailing edge projection line 53 is the actual projection line of the trailing edge 23, that is, the trailing edge projection line 53 includes the part of the projection line blocked by the projection of the hub 1. In the axial projection, the axial center projection of the hub 1 is a point. The connection line between point E and the axial center projection is defined as the first connection line. Any point F other than point E is selected on the trailing edge projection line 53. The connection line between point F and the axial center projection is defined as the second connection line.

[0058] The second connection line is located on the first side of the first connection line. Specifically, the second connection line is located on the side close to the leading edge projection line 51, that is, regardless of the position of point F, the second connection line is always located on the side of the first connection line close to the leading edge projection line 51. The included angle between the first connection line and the second connection line is the stacking angle θ. As point F gradually moves away from point E on the path where the trailing edge projection line 53 is located, the stacking angle θ gradually increases, and the change of the stacking angle θ is non-linear. Specifically, the path where the trailing edge projection line 53 is located is made dimensionless. The trailing edge projection line 53 is defined as zero to one from point E to the top. Please refer to Figure 6 , the abscissa is the dimensionless width length, that is, 0 - 1, and the ordinate is the angle of the stacking angle θ.

[0059] It can be seen that on the path from point E to the middle of the trailing edge projection line 53, as point F gradually moves away from point E, the increasing rate of the stacking angle θ gradually decreases. Specifically, the change of the stacking angle θ shows an increasing trend on 0 - 0.5, where the increasing rate continuously decreases, that is, the slope continuously decreases. On the path from the middle of the trailing edge projection line 53 to the top of the trailing edge projection line 53, as point F gradually moves away from point E, the increasing rate of the stacking angle θ gradually increases. Specifically, on 0.5 - 1, the stacking angle θ still continuously increases, but the increasing trend shows an accelerating trend, that is, the slope continuously increases until it increases to a specific value. The change of the stacking angle realized in the above way can make the shape of the trailing edge 23 of the blade 2 present a special twisted form when viewed from the air outlet side direction, which can reduce the air flow separation phenomenon at the trailing edge 23, improve the aerodynamic noise. Please refer to the schematic diagrams of the air inlet side and the air outlet side Figure 7 .

[0060] Figure 8 It is a schematic diagram of the three-dimensional fitting curve of the edge of the blade 2. The leading edge 21 corresponds to the leading edge fitting curve 61, the blade crown 22 corresponds to the blade crown fitting curve 62, and the trailing edge 23 corresponds to the trailing edge fitting curve 63. Among them, the leading edge fitting curve 61 is as Figure 9 , the leading edge fitting curve 61 falls on a preset surface equation, and the preset surface equation is as follows:

[0061]

[0062] Among them, , , , ; , , where x and y are the curve coordinates of the leading-edge fitting curve 61; such that the inlet angle of the leading-edge fitting curve 61 presents a reasonable distribution state, which can reduce the impact of the leading edge 21 on the fluid on the air inlet side, avoid energy loss, and improve the performance of the fan. Further, A = 0.0339; B = 0.02433; C = -0.05745; D = -97.59.

[0063] When the axial-flow impeller of the present application rotates, the air flow enters from the air inlet side. Due to the angle arrangement at the key positions of the blade 2 and the special profiles of the leading edge 21, the trailing edge 23, and the hub 1, kinetic energy and static pressure are generated when the fluid medium passes through the blade 2 (including the leading edge 21, the trailing edge 23, the pressure surface 24, and the suction surface 25). Under the action of a certain amount of kinetic energy and static pressure energy, the fluid medium flows out along the hub 1 and the blade 2 from the air outlet side. By means of the special meridian plane region 4, the secondary flow and flow separation on the suction surface 25 and the pressure surface 24 are controlled, the flow loss is reduced, and the aerodynamic performance is improved; by designing the stacking angle θ, the flow separation at the tail of the blade 2 is reduced, and the aerodynamic noise is reduced; by designing the leading-edge 21 curve, the impact loss when the fluid enters the blade 2 is reduced, and the efficiency is improved.

[0064] The present application also provides an axial-flow fan, which includes the above-mentioned axial-flow impeller.

[0065] It should be noted that in this specification, relational terms such as first and second are only used to distinguish one entity from several other entities, and do not necessarily require or imply any actual relationship or order between these entities.

[0066] Specific examples are used in this article to elaborate on the principle and implementation manner of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application. It should be pointed out that for those of ordinary skill in the art in this technical field, without departing from the principle of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. An axial flow impeller, characterized in that: The invention comprises a hub (1) rotating about an axis and a plurality of blades (2) distributed around the hub (1); the diameter of the hub (1) gradually decreases in the axial direction from the air outlet side to the air inlet side; the leading edge (21) of the blade (2) is close to the air inlet side; the trailing edge (23) of the blade (2) is close to the air outlet side; and the contact surface between the root of the blade (2) and the outer peripheral surface of the hub (1) is arc-shaped.

2. The axial flow impeller according to claim 1, characterized in that: In a projection of the blade (2) along the rotation direction of the hub (1) onto the plane (3) where the axis is located, the projection profile of the blade (2) includes a blade crown profile (42), a leading edge profile (41), a trailing edge profile (43), and a hub surface profile (44); The leading edge contour line (41) intersects with the blade crown contour line (42) and the wheel hub surface contour line (44) at points A and B, respectively; the trailing edge contour line (43) intersects with the blade crown contour line (42) and the wheel hub surface contour line (44) at points C and D, respectively; an angle formed by a tangent line of the leading edge contour line (41) at point A and a tangent line at point B is greater than 120° and less than 180°; an angle formed by a tangent line of the trailing edge contour line (43) at point C and a tangent line at point D is greater than 120° and less than 180°; The hub surface contour line (44) is a parabola, and the angle formed by the tangent line of the hub surface contour line (44) at the point B and the axis is greater than 15° and less than 30°.

3. The axial flow impeller according to claim 2, characterized in that: The symmetry axis of the parabola is perpendicular to the axis, the blade crown contour line (42) is parallel to the axis, and the trailing edge contour line (43) is closer to the vertex of the parabola than the leading edge contour line (41).

4. The axial flow impeller according to claim 3, characterized in that: The leading edge contour line (41) and the trailing edge contour line (43) are spline curves or arc lines, and the leading edge contour line (41) and the trailing edge contour line (43) are both convex toward one side of the vertex in the axial direction.

5. The axial flow impeller according to any one of claims 2 to 4, characterized in that: The formula of the parabola is defined as: ； Among them, the absolute value of a is greater than , less than ; b and c are constants, and x and y are the curve coordinates of the parabola.

6. The axial flow impeller according to claim 1, characterized in that: The trailing edge (23) intersects with the outer peripheral surface of the hub (1) at a preset point, the trailing edge (23) extends in a direction away from the hub (1), in any projection of the blade (2) along the axial direction of the hub (1), the preset point after projection is defined as point E, the trailing edge (23) after projection is defined as a trailing edge projection line (53), a line connecting the point E and the axis of the hub (1) is defined as a first line, and any point F other than point E on the trailing edge projection line (53) is selected, and a line connecting the point F and the axis of the hub (1) is defined as a second line; The second connecting line is located on a first side of the first connecting line, and an angle formed by the first connecting line and the second connecting line is a stacking angle θ. As the point F gradually moves away from the point E on the path where the trailing edge projection line (53) is located, the stacking angle θ gradually increases.

7. The axial flow impeller according to claim 6, characterized in that: Between the point E and the middle of the trailing edge projection line (53), as the point F gradually moves away from the point E on the path where the trailing edge projection line (53) is located, the rate of increase of the stacking angle θ gradually decreases; Between the middle of the trailing edge projection line (53) and the top of the trailing edge projection line (53), as the point F gradually moves away from the point E on the path of the trailing edge projection line (53), the increasing rate of the stacking angle θ gradually increases.

8. The axial flow impeller according to claim 1, characterized in that: The leading edge fitting curve (61) of the blade (2) falls into the surface equation: ； in, , , , ; , , x, y are the curve coordinates of the leading edge fitting curve (61).

9. The axial flow impeller according to claim 1, characterized in that: The contact surface is projected along the rotation direction of the hub (1) onto the plane (3) where the axis is located, forming a parabola; In a projection of the trailing edge (23) along the axial direction of the hub (1), an angle formed by a line connecting the root of the trailing edge (23) and the axis of the hub (1) and a line connecting a point on the trailing edge (23) and the axis of the hub (1) gradually increases in the extending direction of the trailing edge (23); The leading edge fitting curve (61) of the blade (2) falls within a preset curve equation.

10. An axial flow fan, characterized in that: It comprises the axial flow impeller as described in any one of claims 1 to 9.

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