Axial flow fan
AssigneeSPAL S.r.l.
InventorAlessandro Spaggiari
Life of this patent
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Abstract
The axial flow fan (1; 30) comprises a central hub (3; 33) a plurality of blades (4; 34) which have a root (5; 35), and an end (6; 36). According to one embodiment, the blades (4; 34) are spaced at unequal angles (θi . . . , n) which can vary in percentage (θ%) from 0.5% to 10%, compared to the configuration with equal spacing angles (θ=) for fans with an equal number of blades. Preferably, the blades (4; 34) are delimited by a convex edge (7; 37), whose projection onto the rotation plane of the fan is defined by a parabolic segment and a concave edge (8; 38) whose projection onto the rotation plane of the fan is defined by a circular arc.
Claims11
An axial flow fan (1;
- 30) having a geometrical centre, rotating in a rotation plane (XY) about an axis (2) coinciding with the geometrical centre of the fan (1), the fan (1) including a central hub (3;
- 33), a plurality (n) of blades (4;
- 34) each having a root (5;
- 35) and an end (6;
- 36), each blade (4;
- 34) being also delimited by a convex edge (7) defined by a parabolic segment and a concave edge (8) defined by a second degree geometric curve, each blade (4;
- 34) consisting of blade sections with aerodynamic profiles (18), said aerodynamic profiles (18) having a leading edge, a trailing edge and having a blade angle (β) which decreases gradually and constantly from the root (5) to wards the end (6) of the blade (4), the blade angle (β) being defined as the current angle between the rotation plane (XY) and a straight line joining the leading edge to the trailing edge of the aerodynamic profile (18) of each blade section, the blades (4;
- 34) being spaced at unequal angles (θi . . . , n), the unequal spacing angles (θi . . . , n) varying in percentage (θ%) by values between 0.5% and 10% compared to a configuration with equal spacing angles (θ=) for fans with the same number (n) of blades, that is:
- 0.5≦θ%≦10, where θ % = θ i , … , n - θ = θ = · 100 ,
- so that the fan (1;
- 30) is substantially balanced naturally.
The fan according to claim 12 characterized in that the blades (4) are formed of sections whose aerodynamic profiles (18) each have a blade angle (β) that decreases gradually and constantly from the root (5) to wards the end (6) of the blade (4) according to a cubic law of variation as a function of the radius of the fan at which said sections are located.
Dependencies are inferred from the claim text.