We claim the ornamental design for a fan with air purification function, as shown and described.
FIG. 1 is a perspective view of a fan with air purification function showing the new design;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a rear elevation view thereof;
FIG. 4 is a left-side elevation view thereof;
FIG. 5 is a right-side elevation view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof;
FIG. 8 is a partial enlarged view taken along the line 8-8 of FIG. 1; and,
FIG. 9 is a cross-sectional view taken along the line 9-9 of FIG. 2.
The broken lines illustrate portions of the fan with air purification function that form no part of the claimed design. The broken line rectangle surrounding the partial view of the fan with air purification function in FIG. 8 forms no part of the claimed design.