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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 ...
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, in comparison to a similar-sized propeller in free air. Ducted fans are quieter, and offer good opportunities for thrust vectoring.
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 ...
This high-speed, hot-gas exhaust blends with the low speed, cool-air exhaust from the fan stage, and both contribute to the overall thrust of the engine. Depending on what proportion of cool air is bypassed around the engine core, a turbofan can be called low-bypass, high-bypass, or very-high-bypass engines.
The craft achieved a speed of 4 mph (6.4 km/h), but Stevens abandoned propellers due to the inherent danger in using the high-pressure steam engines. His subsequent vessels were paddle-wheeled boats. [15] By 1827, Czech inventor Josef Ressel had invented a screw propeller with multiple blades on a conical base. He tested it in February 1826 on ...
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.
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 ...
Examples of ships using pumpjets are the Car Nicobar-class patrol vessels, the Hamina-class missile boats, Valour-class frigates, the Stena high-speed sea service ferries, the Royal Navy Swiftsure, Trafalgar and Astute-class submarines, as well as the United States Seawolf and Virginia-classes, and the Russian Borei-class submarines.