Blade and axial flow impeller using same

1. A blade, comprising:

a blade tip, a blade root, a leading edge, a trailing edge, an upper surface and a lower surface, the upper surface and the lower surface being disposed opposite each other; the blade tip, the blade root, the leading edge, and the trailing edge surrounding the upper surface and the lower surface, and connecting the upper surface and the lower surface; and the blade being rotatable about a rotation axis, the rotation axis being perpendicular to a normal plane;

characterized in that:

the blade tip comprises a blade tip base part and a blade tip trailing part, the blade tip base part extending from the leading edge, and the blade tip trailing part extending from the trailing edge and being bent upwards relative to the blade tip base part;

wherein an angle of attack of a chord of the blade tip trailing part is greater than an angle of attack of a chord of the blade tip base part,

wherein the trailing edge is provided with multiple grooves, and a projection of the trailing edge on the normal plane in a direction of the rotation axis is a second curve, wherein an included angle between groove walls of each groove is a, a groove depth is H, and a length of the second curve is L, and

wherein the included angle and the groove depth satisfy, respectively:

α∈[10°,110°];

H=W×L, W ∈[1.5%,20%].

2. The blade of claim 1 , characterized in that: the upper surface extends smoothly from the blade tip to the blade root.

3. The blade of claim 1 , characterized in that:

a range of values of the angle of attack of the chord of the blade tip trailing part is greater than or equal to 20° and less than or equal to 30°.

4. The blade of claim 1 , characterized in that:

a proportion of a length of the blade tip taken up by the blade tip trailing part is greater than or equal to 1/12 and less than or equal to ⅛.

5. The blade of claim 1 , characterized in that:

a projection of the leading edge on the normal plane in the direction of the rotation axis is a first curve, and the first curve has an even number of inflection points;

the rotation axis and the normal plane perpendicularly intersect at a perpendicular foot;

a line connecting any point on the first curve and the perpendicular foot is a first connecting line;

a line connecting the perpendicular foot and a point of projection of an intersection point of the blade root and the leading edge on the normal plane in the direction of the rotation axis is a second connecting line;

an included angle between the first connecting line and the second connecting line is a leading edge angle θ; and

the leading edge angle θ of any point on the first curve satisfies θ∈[0°,20°].

6. The blade of claim 1 , characterized in that:

the included angle α between the groove walls of a groove closest to the blade tip in the multiple grooves satisfies: α∈[80°, 110°].

7. The blade of claim 1 , characterized in that:

a length of the trailing edge between groove walls of two adjacent grooves is the same.

8. The blade claim 1 , characterized in that:

on the trailing edge of the blade, the upper surface of the blade extends further than the lower surface in a circumferential direction, and a cross section of the trailing edge in the circumferential direction of the blade is arc-shaped.

9. An axial flow impeller, comprising:

a hub, the hub having a rotation axis, the hub being rotatable about the rotation axis; and

at least two blades, the at least two blades being arranged on an outer circumferential face of the hub, wherein each blade of the at least two blades comprises:

a blade tip, a blade root, a leading edge, a trailing edge, an upper surface, and a lower surface, the upper surface and the lower surface being disposed opposite each other; the blade tip, the blade root, the leading edge, and the trailing edge surrounding the upper surface and the lower surface and connecting the upper surface and the lower surface, and the blade being rotatable about the rotation axis, the rotation axis being perpendicular to a normal plane;

characterized in that:

the blade tip comprises a blade tip base part and a blade tip trailing part, the blade tip base part extending from the leading edge, and the blade tip trailing part extending from the trailing edge and being bent upwards relative to the blade tip base part;

wherein an angle of attack of a chord of the blade tip trailing part is greater than an angle of attack of a chord of the blade tip base part,

wherein the trailing edge is provided with multiple grooves, and a projection of the trailing edge on the normal plane in a direction of the rotation axis is a second curve, wherein an included angle between groove walls of each groove is a, a groove depth is H, and a length of the second curve is L, and

wherein the included angle and the groove depth satisfy, respectively:

α∈[10°,110°];

H=W×L, W ∈[1.5%,20%].

10. A blade, comprising:

a blade tip, a blade root, a leading edge, a trailing edge, an upper surface, and a lower surface, the upper surface and the lower surface being disposed opposite each other; the blade tip, the blade root, the leading edge, and the trailing edge surrounding the upper surface and the lower surface and connecting the upper surface and the lower surface, and the blade being rotatable about a rotation axis, the rotation axis being perpendicular to a normal plane;

characterized in that:

the blade tip comprises a blade tip base part and a blade tip trailing part, the blade tip base part extending from the leading edge, and the blade tip trailing part extending from the trailing edge and being bent upwards relative to the blade tip base part;

wherein an angle of attack of a chord of the blade tip trailing part is greater than an angle of attack of a chord of the blade tip base part, and

wherein, on the trailing edge of the blade, the upper surface of the blade extends further than the lower surface in a circumferential direction, and a cross section of the trailing edge in the circumferential direction of the blade is arc-shaped.