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Kort nozzle The towboat Dolphin I in a floating drydock on the Mississippi River in Algiers, Louisiana. A ducted propeller, also known as a Kort nozzle, is a marine propeller fitted with a non-rotating nozzle. It is used to improve the efficiency of the propeller and is especially used on heavily loaded propellers or propellers with limited ...
Ludwig Kort (1888 - 1958 [1]) was a German fluid dynamicist known for developing the ducted propeller, or Kort nozzle. In an attempt to reduce canal erosion, Kort discovered that directing the wake of a propeller through a short, stationary nozzle also increased thrust. [2] He submitted a U.S. patent for this technique, which was awarded in ...
Azimuth thrusters on the tug Oued el Kebir - note the Kort nozzles. There are two major variants, based on the location of the motor: [citation needed] Mechanical transmission, which connects a motor inside the ship to the outboard unit by gearing. The motor may be diesel or diesel-electric.
The word is commonly used in the marine vernacular, and implies a mechanical assembly that is more complicated than a propeller. The Kort nozzle, pump-jet and rim-driven thruster are examples. An example propulsor is shown in the accompanying picture. It has a shroud which cuts down on blade-tip cavitation and radiated noise.
The Z-drives have four-bladed propellers which are 57.1 inches (145 cm) in diameter [21] and are equipped with Kort nozzles. They can be operated in "tiller mode" where the Z-drives turn in the same direction to steer the ship, or in "Z-conn mode" where the two Z-drives can turn in different directions to achieve specific maneuvering objectives.
A ducted propeller is mounted as an integral part of the rudder and is fixed to it. The duct is a Kort nozzle and enables the propeller to develop more thrust than an unducted propeller. The Pleuger rudder is necessarily mounted in the flow from the main engine's propeller in a ship with an odd number of propellers.
The Voith Schneider propeller was originally a design for a hydro-electric turbine. [2] Its Austrian inventor, Ernst Schneider, had a chance meeting on a train with a manager at Voith's subsidiary St. Pölten works; this led to the turbine being investigated by Voith's engineers, who discovered that although it was no more efficient than other water turbines, Schneider's design worked well as ...
The Kort nozzle is a sturdy cylindrical structure around a special propeller having minimum clearance between the propeller blades and the inner wall of the Kort nozzle. The thrust-to-power ratio is enhanced because the water approaches the propeller in a linear configuration and exits the nozzle the same way.