Axial flow fan
View Patent ↗Disclosed is an axial flow fan capable of achieving reduction of noise while having a high blowing efficiency compared to the power consumption of a motor adapted to drive the axial flow fan. The axial flow fan includes a hub, and a plurality of blades extending radially around the hub. Each blade has a sweep angle varying gradually from a backward angle at a root of the blade connected to the hub to a forward angle at a tip of the blade, while having a flow dispersion region having a plurality of regions where the sweep angle is alternately changed, at a region defined between a backward sweep angle region at the root of the blade and a forward sweep angle region at the tip of the blade. Each blade has a longitudinal cross section curved to have a wave structure between the root of the blade and the tip of the blade. The axial flow fan may further include a fan band connecting tips of the blades. The axial flow fan achieves reduction of blowing noise by receiving air in a dispersed state at the leading edge of each blade, discharging air in a dispersed state at the trailing edge of each blade, and offsetting turbulent flows of air by virtue of the wave-shaped longitudinal cross-sectional structure of each blade.
1. An axial flow fan including a hub, and a plurality of blades extending radially around the hub, wherein:
each of the blades has a sweep angle varying gradually from a backward angle at a root of the blade connected to the hub to a forward angle at a tip of the blade;
each of the blades has a flow dispersion region having a plurality of regions where the sweep angle is alternately changed, at a region defined between a backward sweep angle region at the root of the blade and a forward sweep angle region at the tip of the blade; and
each of the blades has a leading edge extending from the root of the blade to the tip of the blade, and has a sweep angle varying gradually from a maximum backward angle at the root of the blade to a maximum forward angle at the tip of the blade while being alternately changed in direction at an intermediate portion of the leading edge from a backward direction, corresponding to a sweep direction at the root of the blade, to a forward direction, and then from the forward direction to the backward direction, so that the sweep angle is finally changed from the backward direction to the forward direction corresponding to a sweep direction at the tip of the blade.
2. The axial flow fan according to claim 1 , wherein each of the blades has a trailing edge having the same sweep angle variation characteristics as those of the leading edge.
3. The axial flow fan according to claim 1 , further comprising:
a fan band connecting tips of the blades.
4. The axial flow fan according to claim 1 , wherein each of the blades has a width gradually increasing as the blade extends from its root to its tip.
5. The axial flow fan according to claim 1 , wherein each of the blades has a longitudinal cross section curved to have a wave structure between the root of the blade and the tip of the blade.
6. The axial flow fan according to claim 1 , wherein the absolute value of the forward sweep angle in the flow dispersion region on a mid-chord line between leading and trailing edges of the each of the blades corresponds to ⅔ or less of the absolute value of the backward sweep angle at the root of the blade.
7. The axial flow fan according to claim 6 , wherein the absolute value of the backward sweep angle in the flow dispersion region corresponds to ⅔ or less of the absolute value of the forward sweep angle at the tip of the blade.
8. The axial flow fan according to claim 1 , wherein the flow dispersion region of each of the blades is defined within a range of 0.15 to 0.75 of a non-dimensional radius expressed by the following expression:
Non-Dimensional Radius
=
r
-
Rh
Rt
-
Rh
where “r” is a radial length from a center of the hub to an optional point on the blade, “Rh” is a radius of the hub, and “Rt” is a radial length from the center of the hub to the tip of the blade.
9. An axial flow fan including a hub, and a plurality of blades extending radially around the hub, wherein:
each of the blades has a sweep angle varying gradually from a forward angle at a root of the blade to a backward angle at a tip of the blade; and
each of the blades has a flow dispersion region having a plurality of regions where the sweep angle is alternately changed, at a region defined between a forward sweep angle region at the root of the blade and a backward sweep angle region at the tip of the blade.
10. The axial flow fan according to claim 9 , wherein each of the blades has a leading edge extending from the root of the blade to the tip of the blade, and has a sweep angle varying gradually from a maximum forward angle at the root of the blade to a maximum backward angle at the tip of the blade while being alternately changed in direction at an intermediate portion of the leading edge from a forward direction, corresponding to a sweep direction at the root of the blade, to a backward direction, and then from the backward direction to the forward direction, so that the sweep angle is finally changed from the forward direction to the backward direction corresponding to a sweep direction at the tip of the blade.
11. An axial flow fan including a hub, and a plurality of blades extending radially around the hub, wherein:
each of the blades has a sweep angle varying gradually from a backward angle at a root of the
blade connected to the hub to a forward angle at a tip of the blade;
each of the blades has a flow dispersion region having a plurality of regions where the sweep
angle is alternately changed, at a region defined between a backward sweep angle region at
the root of the blade and a forward sweep angle region at the tip of the blade; and
each of the blades has a longitudinal cross section curved to have a wave structure between the root of the blade and the tip of the blade.