According to embodiments of the invention, an impeller includes a hub, and a plurality of radial blades for drawing the air inflow axially through the hub and delivering the drawn air radially towards the outside. A ring is attached to one or more tips of the plurality of radial blades to block a portion of the tip toward the inlet side of the impeller. The preferred blockage factor, which is the ratio of a height of the ring to a height of the tip, is approximately in a range between 30% and 40%. By blocking a portion of the tip toward the inlet side of the impeller, the low-momentum flow zone toward the inlet side of impeller is blocked, while the high-momentum flow zone toward the back side of impeller is enhanced. As such, the performance of the impeller is enhanced.