| 摘要 |
A low-aspect ratio propeller system is provided with a multiple ring structure (42) formed with a plurality of circular or non-circular; annular, narrrow equivalent air foil rings (56.1, 56.2, 56.3; 56.4) which are held by rails (44) in a predetermined relationship with the propeller blades (44). The upstream ping (56.1) is located downstream from the tip vortex of the propeller (44) within the axial span of the propeller. One or more additional downstream-located rings (56.2, 56.3, 56.4) are used so as to provide at least one annular multiple ring-defined pump aperture (60, 62; 64) through or which peripheral vortices generated by the propeller blades (44) or fan blades may enhance the mass flow. These vortices increase thrust beacause their induction action on the rings, (56.1, 56.2, 56.3, 56.4) increase beneficial ring flow circulation. Augmented ring flow reduces the velocities in the expanding wake by increasing the mass flow. The destruction of tip and root vortices reduces noise. The multiple ring structure (42) also serves as a guard.
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