| 摘要 |
<p>A fan apparatus is described that comprises a rotational hub that defines a central axis, a first fan blade coupled to the rotational hub and extending radially outward from the central axis, wherein the first fan blade has a first pitch angle; a second fan blade coupled to the rotational hub and extending radially outward from the first central axis, wherein the second fan blade has a second pitch angle opposite the first pitch angle; and a housing that defines cylindrical interior volume with a central axis coaxial with the central axis of the rotational hub, wherein the first and second fan blades reside within the cylindrical interior volume.</p> |
