We claim the ornamental design for a centrifugal fan, as shown and described.
FIG. 1 is a front side elevation view of a centrifugal fan embodying our design;
FIG. 2 is a rear side elevation view of the centrifugal fan shown in FIG. 1;
FIG. 3 is a right side elevation view of the centrifugal fan shown in FIG. 1;
FIG. 4 is a left side elevation view of the centrifugal fan shown in FIG. 1;
FIG. 5 is a top plan view of the centrifugal fan shown in FIG. 1;
FIG. 6 is a bottom plan view of the centrifugal fan shown in FIG. 1; and,
FIG. 7 is a perspective view of the centrifugal fan shown in FIG. 1.
The broken line showing of portions of the centrifugal fan is included for the purpose of illustrating environmental structure and forms no part of the claimed design.