Resistance Reduction in Merchant Ships by the New Propulsion System

摘要

The new propulsion system uses a hydraulic transmission outside the ship's hull. An axial flow pump driven directly at high speed by the ship's prime mover imports energy to the seawater which drives the propeller through turbine blades attached internal to the hub. This study explored the feasibility and the advantages of using the inflow into the pump of the new propulsion system as a means for boundary layer suction control. The results show that boundary layer control is limited to prevention of boundary layer separation at the stern. The rate of suction is insufficient to affect the wave drag of the hull. The effect of boundary layer suction is limited to the stabilization of the flow within the boundary layer and some reduction of its thickness. The flow into the propeller disc can be improved and smoothed out by a suction slot operating near the stern of the vessel. Recommendations are given for tests with models of merchant ship forms to define quantitatively the use of the inflow into the pump of the new propulsion system on the boundary layer separation and drag reduction by boundary layer suction.