The propeller with a small duct of this invention has the propeller 10 attached to the stern of the hull 1, and the duct 20 mounted in front of the propeller 10, The diameter (Ddin) of the duct 20 To 20% or more and 50% or less of the diameter Dp of the propeller 10, and the pitch H of the propeller 10 becomes the maximum value at the blade root of the propeller and the blade tip. In the energy saving device which combines the characteristics of both the large duct and the medium duct, it is characterized by the reduced pitch which decreases in the radius (R) direction, which becomes the minimum value in Fig. 1). By disposing the small duct 20 close to the front of the propeller 10, in the real sea area where the A load of degree increases, the cavitation is suppressed, and then the propeller that dominates the efficiency ( 10) Optimize the load distribution in the radial (R) direction using interference with the small duct 20 The.
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