Wednesday, December 22, 2021

Talking about Marine propulsion

9:13 PM |

Marine propulsion is the mechanism or system used to generate thrust to move a ship or boat across water.

Numerous types of propulsion have been developed over time.

Screw- power is transmitted from the engine to the screw by way of a propeller shaft, which may be connected to a gearbox. 
Smaller vessels tend to have a single screw, even very large ships such as tankers, container ships and bulk carriers may have single screws for reasons of fuel efficiency.

Paddle wheel is large wheel, generally built of a steel framework, upon the outer edge of which are fitted numerous paddle blades

Pump-jet uses a ducted propeller (axial-flow pump), centrifugal pump, or mixed flow pump to create a jet of water for propulsion.

But the most interesting one in my opinion is Voith-Schneider cyclo-rotor which is a practical cyclorotor that provides instant thrust in any direction. There is no need to turn a propulsor. Most ships with VSPs do not need or have a rudder.


While paddles and sails are still used on some smaller boats, most modern ships are propelled by mechanical systems consisting of an electric motor or engine turning a propeller, or less frequently, in pump-jets, an impeller.

Manpower, in the form of paddles, and sail were the first forms of marine propulsion. Rowed galleys, some equipped with sail, also played an important early role. The first advanced mechanical means of marine propulsion was the marine steam engine, introduced in the early 19th century.

During the 20th century it was replaced by two-stroke or four-stroke diesel engines, outboard motors, and gas turbine engines on faster ships. Marine nuclear reactors, which appeared in the 1950s, produce steam to propel warships and icebreakers; commercial application, attempted late that decade, failed to catch on.

Electric motors using electric battery storage have been used for propulsion on submarines and electric boats and have been proposed for energy-efficient propulsion.


Development in liquefied natural gas (LNG) fueled engines are gaining recognition for their low emissions and cost advantages.

Stirling engines, which are quieter, smoother running, propel a number of small submarines in order to run as quietly as possible. Its design is not used in civilian marine application due to lower total efficiency than internal combustion engines or power turbines.

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