| 摘要 |
PURPOSE:To obtain high propelling efficiency with simple construction by arranging a spiral guide on the inner cylindrical surface of a duct installed on either flow-in side or flow-out side of a screw propeller so that water flow is accelerated in the turning direction opposite to that of the screw propeller. CONSTITUTION:Water introduced into a duct 2 as shown with arrows A by turning a screw propeller 1 in the C direction can be accelerated in the B direction, opposite to that of the screw propeller 1, by means of a spiral guide 2a formed on the inner surface of a duct 2 when the water flows toward the screw propeller 1, thereby reducing turning angular velocity of the water flow behind the screw propeller 1 and making the water flow behind the screw propeller 1 closer to laminar flow as shown with arrows D. Thus, turning velocity of the water flow behind the screw propeller 1 can be reduced, propeller thrust can be increased and propelling efficiency (eta) can be increased, contributing to energy saving.
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