US 6,116,856 A · Bi-directional fan having asymmetric, reversible blades

Abstract

A bi-directional fan includes asymmetrically-shaped fan blades wherein, at each transverse cross-section of the blade, the profile of the blade includes a leading portion lying on one side of a straight line connecting the leading and trailing edges of the blade and a trailing portion lying on the opposite side of the straight line. The leading portion of the blade is larger than the trailing portion of the blade, and the point at which the blade's mean line of profile crosses the straight line is closer to the trailing edge than the leading edge. From the leading edge to a point of maximum camber, the shape of the profile of the blade is described by a polynomial expression. From the point of maximum camber to the trailing edge, the shape of the profile of the blade is described by a cosine wave function. The larger leading portion presents a greater forward-curved surface area which allows the blade to move air more efficiently in the forward direction. While the efficiency of the asymmetric fan blade is reduced in the reverse direction, when the fan is used in the forward direction more than 50% of the time, the overall efficiency of the asymmetric-blade fan is greater than that of the symmetric-blade fan. Each asymmetric fan blade can assume either of two oppositely-oriented positions, allowing one set of identical blades to provide a range of different forward and reverse air flow efficiencies.

Claims18

Dependent claims

A bi-directional axial flow fan, comprising:

an impeller hub rotatable about an axis;
a motor for rotating said impeller hub in either of two directions about the axis;
and
a plurality of asymmetric blades extending from said hub in a direction radial to the axis,
wherein each of said blades has a cross-sectional profile transverse to the radial direction including:
a leading portion extending from a leading edge of the blade and lying on one side of a line connecting the leading edge of the blade and a trailing edge of the blade;
and a trailing portion extending from the trailing edge of the blade and lying on an opposite side of the line, the leading portion and the trailing portion joining at an intersection on the line, which intersection is closer to one of the leading edge of the blade and the trailing edge of the blade than to the other of the leading edge of the blade and the trailing edge of the blade.

4 more elements

An asymmetric fan blade having a cross-sectional profile including:

a leading portion extending from a leading edge of the blade and lying on one side of a line connecting the leading edge of the blade and a trailing edge of the blade;
and a trailing portion extending from the trailing edge of the blade and lying on an opposite side of the line, the leading portion and the trailing portion joining at an intersection on the line, wherein a shape of a first section of the leading portion extending from the leading edge to a point of maximum camber is described by a polynomial function, and wherein a shape of a second section of the leading portion extending from the point of maximum camber to the intersection and a shape of the trailing portion are described by a cosine function.

A method of constructing an asymmetric fan blade having a cross-sectional profile including a leading portion extending from a leading edge of the blade and lying on one side of a line connecting leading edge of the blade and a trailing edge of the blade, and a trailing portion extending from the trailing edge of the blade and lying on an opposite side of the line, the leading portion and the trailing portion joining at an intersection on the line, the method comprising the steps of:

shaping a first section of the leading portion extending from the leading edge to a point of maximum camber in accordance with a polynomial function;
shaping a second section of the leading portion extending from the point of maximum camber to the intersection in accordance with a cosine function;
and
shaping the trailing portion in accordance with the cosine function.

1 more element

Dependencies are inferred from the claim text.

Bi-directional fan having asymmetric, reversible blades

Life of this patent

Bi-directional fan having asymmetric, reversible blades

Life of this patent

Abstract

Claims18