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A propeller imparts momentum to a fluid which causes a force to act on the ship. [1] The ideal efficiency of any propulsor is that of an actuator disc in an ideal fluid. This is called the Froude efficiency and is a natural limit which cannot be exceeded by any device, no matter how good it is.
For a displacement vessel, that is the usual type of ship, three main types of resistance are considered: that due to wave-making, that due to the pressure of the moving water on the form, often not calculated or measured separately, and that due to friction of moving water on the wetted surface of the hull. These can be split up into more ...
An advanced type of propeller used on the American Los Angeles-class submarine as well as the German Type 212 submarine is called a skewback propeller. As in the scimitar blades used on some aircraft, the blade tips of a skewback propeller are swept back against the direction of rotation. In addition, the blades are tilted rearward along the ...
However, in commercial ships and in traditional machinery arrangement, contra-rotating propellers are rare, due to cost and complexity. ABB provided an azimuth thruster for ShinNihonkai Ferries in form of the CRP Azipod, [2] claiming efficiency gains from the propeller (about 10% increase [3]) and a simpler hull design.
A view of the end of the thruster unit from Yamato I, at the Ship Science Museum in Tokyo. MHD has no moving parts, which means that a good design might be silent, reliable, and efficient. Additionally, the MHD design eliminates many of the wear and friction pieces of the drivetrain with a directly driven propeller by an engine. Problems with ...
The rim-driven thruster, also known as rim-driven propulsor/propeller (or RDP) is a novel type of electric propulsion unit for ships. The concept was proposed by Kort around 1940, but only became commercially practical in the early 21st century due to advances in DC motor controller technology. [ 1 ]
Model of Emma Mærsk undergoing testing in a ship model basin. In marine engineering, a ship motion test is hydrodynamic test performed with ship models for the purpose of designing a new (full sized) ship, or refining the design of a ship to improve its performance at sea. [1] Tests are carried out in a ship model basin or "towing tank". [2]
Ships propelled by medium or high speed diesel engines may have one or two (sometimes more) propellers, commonly with one or more engines driving each propeller shaft through a gearbox. Where more than one engine is geared to a single shaft, each engine will most likely drive through a clutch, allowing engines not being used to be disconnected ...