Low drag fan assembly

Abstract

A fan assembly includes a circular first array of first fan blades; a first primary ring member supportively connecting inner extremities of the first blades about a fan axis, respective end extremities of at least a majority of the first blades defining inside and outside diameters of the array, the first blades being oriented for producing a primary axial fluid flow between the inside and outside diameters in response to rotation of the first ring member, the first ring member extending between the inside and outside diameters. A second primary ring member connects outer extremities of the first blades, the first blades in combination with the first ring member defining a generally circular opening about the fan axis. Optionally a circular second array of a plurality of second blades that are oriented for producing secondary axial fluid flow in an opposite direction relative to the primary axial fluid flow, a secondary ring connecting outer extremities of second blades, end extremities of at least a majority of the second blades defining an outside diameter of the second array. A plurality of spokes extend inwardly from the first primary ring member for rotatably supporting the first primary ring member, a hub connecting the spokes to a rotating element, the second blades also being held in fixed relation to the spokes, whereby, when the rotating element is being rotated for producing the primary axial flow, an unimpeded secondary axial flow is produced within the opening outside of the secondary ring.