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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 ...
A propulsor is a mechanical device that gives propulsion. 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.
Azimuth thrusters (and Kort nozzles) have both advantages and disadvantages when compared to cycloidal drives. The azimuth thruster is less efficient and slower to manoeuvre, but is likely to be cheaper in the short term. Life cycle costs favour the Voith solution, something reflected in the residual value of a Voith water tractor.
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.
As originally built, Mohawk had two controllable-pitch Kort-nozzle propellers for propulsion. She had two 20-cylinder Diesel engines, GM EMD 20-645F7B, [4] which provided 4,500 shaft horsepower. These would drive the ships at 15 knots. She also had a 300-horsepower bow thruster to improve maneuverability. [2] [5]
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 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.