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In aeronautics, a ducted fan is a thrust-generating mechanical fan or propeller mounted within a cylindrical duct or shroud. Other terms include ducted propeller or shrouded propeller . [ 1 ] When used in vertical takeoff and landing ( VTOL ) applications it is also known as a shrouded rotor .
The propulsive efficiency is always less than one, because conservation of momentum requires that the exhaust have some of the kinetic energy, and the propulsive mechanism (whether propeller, jet exhaust, or ducted fan) is never perfectly efficient. It is greatly dependent on exhaust expulsion velocity and airspeed.
This high efficiency and power is what allows such large fans to be viable, and the increased thrust available (up to 75,000 lbs per engine in engines such as the Rolls-Royce Trent XWB or General Electric GENx), have allowed a move to large twin engine aircraft, such as the Airbus A350 or Boeing 777, as well as allowing twin engine aircraft to ...
It helps in understanding the efficiency of the propeller at different speeds and is particularly useful in the design and analysis of propeller-driven vehicles.It is the ratio of the freestream fluid speed to the propeller, rotor, or cyclorotor tip speed. When a propeller-driven vehicle is moving at high speed relative to the fluid, or the ...
A propfan, also called an open rotor engine, open fan engine [1] [2] or unducted fan (as opposed to a ducted fan), is a type of aircraft engine related in concept to both the turboprop and turbofan, but distinct from both. The design is intended to offer the speed and performance of a turbofan, with the fuel economy of a turboprop.
While there is a loss in efficiency as the fan is drawing on a smaller area of the free stream and so using less air, this is balanced by the ducted fan retaining efficiency at higher speeds where conventional propeller efficiency would be poor. A ducted fan or propeller also has certain benefits at lower speeds but the duct needs to be shaped ...
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 ...
An axial fan is a type of fan that causes gas to flow through it in an axial direction, parallel to the shaft about which the blades rotate. The flow is axial at entry and exit. The fan is designed to produce a pressure difference, and hence force, to cause a flow through the fan. Factors which determine the performance of the fan include the ...