Patent ID: 6554574
Filing Date: 2003-04-29
Classification: F04D,Y10S

Abstract:
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 (&bgr;) which decreases gradually and constantly from the root (5) to wards the end (6) of the blade (4), the blade angle (&bgr;) 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 (&thgr;i . . . , n), the unequal spacing angles (&thgr;i . . . , n) varying in percentage (&thgr;%) by values between 0.5% and 10% compared to a configuration with equal spacing angles (&thgr;=) for fans with the same number (n) of blades, that is:0.5&lE;&thgr;%&lE;10, where Î¸&it;â€ƒ&it;%=Î¸i,â€¦&it;â€ƒ,n-Î¸=Î¸=&CenterDot;100,so that the fan (1; 30) is substantially balanced naturally.