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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 diameter. It was developed first by Luigi Stipa (1931) and later by Ludwig Kort (1934). The Kort nozzle is ...
Free response questions typically require little work for instructors to write, but can be difficult to grade consistently as they require subjective judgments. Free response tests are a relatively effective test of higher-level reasoning, as the format requires test-takers to provide more of their reasoning in the answer than multiple choice ...
The high-bypass turbofan engines used on many modern airliners is an example of a very successful and popular use of ducted fan design. The duct increases thrust efficiency by up to 90% in most cases [citation needed], in comparison to a similar-sized propeller in free air. Ducted fans are quieter, and offer good opportunities for thrust vectoring.
A ducted fan or propeller also has certain benefits at lower speeds but the duct needs to be shaped in a different manner than one for higher speed flight. More air is taken in and the fan therefore operates at an efficiency equivalent to a larger un-ducted propeller.
A rim-driven thruster integrates an electric motor into a ducted propeller. The cylindrical duct acts as the stator, while the tips of the blades act as the rotor. They typically provide high torque and operate at low RPMs, producing less noise. The system does not require a shaft, reducing weight.
Though the term is most commonly applied to aircraft, its most ubiquitous propeller example is a common outboard motor for a small boat. “Pusher configuration” describes the specific (propeller or ducted fan ) thrust device attached to a craft, either aerostats ( airship ) or aerodynes (aircraft, WIG , paramotor , rotorcraft ) or others ...
An airbreathing jet engine (or ducted jet engine) is a jet engine in which the exhaust gas which supplies jet propulsion is atmospheric air, [1] which is taken in, compressed, heated, and expanded back to atmospheric pressure through a propelling nozzle. [2]
A bypass ratio of 6, for example, means that 6 times more air passes through the bypass duct than the amount that passes through the combustion chamber. Turbofan engines are usually described in terms of BPR, which together with overall pressure ratio, turbine inlet temperature and fan pressure ratio are important design parameters.