Patent attributes
An axial-flow impeller includes a hub and blades. A tail edge of one blade has recessed portions successively arranged in a direction from a blade root of the blade to an outer edge of the blade. On a reference projection of the impeller on a reference plane perpendicular to a rotation axis of the impeller, a first connection line connects a starting point of a first recessed portion closest to the blade root and an end point of a second recessed portion closest to the outer edge, a second connection line connects a tail edge point of the blade root and the end point of the second recessed portion, one or more of the recessed portions is each partially located at a front-edge side of the second connection line, and remaining one or more of the recessed portions is each completely located between the first and second connection lines.
