Centrifugal fan

A centrifugal fan configured such that an impeller having a plurality of blades along a circumferential direction and disposed between a disk-shaped main plate and an annular shroud is accommodated in a casing, and air is suctioned from a suction opening and discharged outward in a radial direction of the impeller by a centrifugal force due to a rotation of the impeller, thereby discharging the air from the casing,

• wherein the casing includes an upper plate formed with the suction opening, a lower plate, and a plurality of supporting struts interposed between the upper plate and the lower plate, and lateral sides formed between the supporting struts, wherein each of the lateral sides of the casing have only the supporting struts to form discharge openings,
• wherein at least one of the supporting struts comprises:
• a first side wall that is positioned at upstream side with respect to a rotational direction of the impeller;
• a second side wall that is positioned at downstream side with respect to the rotational direction of the impeller;
• and
• a third side wall that is arranged to face the impeller, and
• wherein the first side wall is arranged to be inclined inward from one of the lateral sides of the casing.
• wherein the air suctioned from the suction opening of the upper plate is discharged outward in the radial direction of the impeller through spaces between the plurality of blades, and the air discharged outward in the radial direction of the impeller is discharged from the discharge openings,
• wherein the plurality of blades of the impeller are backward inclined blades in a rotation direction, and
• wherein each of the supporting struts has a surface which matches a line passing through a center point of a radius of curvature of an arc surface of each of the blades and a leading edge of an outer circumferential edge of the corresponding blade.