The ornamental design for a portable aircirculator, as shown and described.
FIG. 1 is a right side front perspective view of a portable air circulator showing my new design;
FIG. 2 is a left side rear perspective view thereof;
FIG. 3 is a front elevation view thereof;
FIG. 4 is a right side elevation view thereof;
FIG. 5 is a left side elevation view thereof;
FIG. 6 is a rear elevation view thereof; and,
FIG. 7 is a top plan view thereof.
The broken line showing of portions of the air circulator is included for the purpose of illustrating environmental structure and forms no part of the claimed design.