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efficiency by up to 90% in most cases, in comparison to a similar-sized propeller in free air. Ducted fans are quieter, and offer good opportunities for thrust vectoring. The shroud offers good protection to ground personnel from accidentally contacting the spinning blades, as well as protecting the
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Drawbacks include increased weight due to the added structure of the shroud, a need for precision in tolerances of blade-tip to shroud clearance, a need for better vibration control compared to free-air propellers, and complex duct design requirements. Lastly, when at high angles of attack, the
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Principally, it reduces the vortices created by air flowing round the ends of the blades. This reduces the aerodynamic losses or drag, thus increasing the overall efficiency of the fan. Because of this, the fan can either be used to provide increased thrust and aircraft performance, or be made
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An advantage of the pod approach is that the design of each component can be matched to the others, helping to maximise performance and minimise weight. It also eases the vehicle designer's task of integration with the vehicle and its systems.
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Like any other fan, propeller or rotor, a ducted fan is characterised by the number of blades. The Rhein
Flugzeugbau (RFB) SG 85 had three blades, while the Dowty Rotol Ducted Propulsor had seven. The blades may be of fixed or variable pitch.
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The duct or shroud is an aerodynamic ring which surrounds the fan and closely fits the blade tips. It must be made rigid enough not to distort under flight loads nor touch the blades as they turn. The duct performs several functions:
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The reduced tip vortices also mean that the fan wake is less turbulent. With careful design, the heated discharge from the engine cooling system can be injected into the low-turbulence fan wake to increase thrust.
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The fan may be mounted directly on the powerplant output shaft, or driven remotely via an extended drive shaft and gearing. In the remote arrangement, several fans may be driven by a single powerplant.
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In some cases, a shrouded rotor can be 94% more efficient than an open rotor. The improved performance is mainly because the outward flow is less contracted and thus carries more kinetic energy.
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usually make use of the better high-speed performance of a low bypass ratio turbofan with a smaller fan diameter. However, a ducted fan may be powered by any source of shaft power such as a
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engines, electric-powered ducted fans remain popular on smaller, lower-cost model aircraft. Some electric-powered ducted fan airplanes can reach speeds of more than 320km/h (200mph).
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A ducted fan may be powered by any kind of motor capable of turning the fan. Examples include piston, rotary (Wankel), and turboshaft combustion engines, as well as electric motors.
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A ducted fan has three main components; the fan or propeller which provides thrust or lift, the duct or shroud which surrounds the fan, and the engine or motor which powers the fan.
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It acts as a protective device, both to protect objects such as ground staff from being hit by the whirling blades, and to protect the blades from damage during such an impact.
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VTOL aircraft. The high-bypass turbofan engines used on many modern airliners is an example of a very successful and popular use of ducted fan design.
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combined with ducted-fan units were the first achievable means of modeling a scaled-size jet aircraft. Despite the introduction of model-scale
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It provides acoustic shielding which, together with the reduced energy waste, significantly cuts noise emissions from the propeller.
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contain a duct integrated into the fan assembly; the duct is also used for mechanically mounting the fan to other components.
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at lower speeds than an equivalent ducted fan. The most common ducted fan arrangement used in full-sized aircraft is a
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Efficiency advantages are reduced, and may even be reversed, at lower rotation speeds, thrust levels and airspeeds.
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In aircraft applications, the operating speed of an unshrouded propeller is limited since tip speeds approach the
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An assembly designed throughout as a single integrated unit is referred to as a fan pod or ducted propulsor.
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of the duct the designer can advantageously affect the velocity and pressure of the airflow according to
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Ducted Fan or
Shrouded Rotor Aerodynamics and its Application in Miniature VTOL Aerial Vehicles
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Hover and wind-tunnel testing of shrouded rotors for improved micro air vehicle design
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Complex duct design, and weight increase even if constructed from advanced composites.
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Ducted fans are used for propulsion or direct lift in many types of vehicle including
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Good efficiency requires very small clearances between the blade tips and the duct.
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Requires reduced vibration levels compared to a free propeller or rotor.
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hobbyists, the ducted fan is popular with builders of high-performance
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222:. High bypass ratio turbofan engines are used on nearly all civilian
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242:. A kind of ducted fan, known as a fantail or by the trademark name
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blades themselves from external debris or objects. By varying the
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441:"Jon Longbottom - Mechanical aeronautics, thesis in PDF format"
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Avian
Gyroplane with ducted pusher prop (but no tail-boom)
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engine, where the power to turn the fan is provided by a
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53:. When used in vertical takeoff and landing (
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100:shroud can stall and produce high drag.
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381:Performance Study of a Ducted Fan System
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428:Jane's All the World's Aircraft 1980-81
409:Jane's All the World's Aircraft 1980-81
379:Anita I. Abrego and Robert W. Bulaga; "
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284:, and other low-speed designs such as
57:) applications it is also known as a
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396:", 2009. (retrieved 22 March 2022).
206:Dirigible airship with ducted fans
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353:(example of a ducted fan aircraft)
328:personal aircraft with ducted fans
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480:, 2008. Accessed: 28 August 2015.
282:Lockheed Martin F-35 Lightning II
300:radio controlled model aircraft
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45:or shroud. Other terms include
496:Aircraft propulsion components
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315:cooling fans used in computers
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1:
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41:mounted within a cylindrical
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276:Ducted fans are favored in
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246:, is also used to replace
359:(example of a ducted fan
271:Air Cushion Landing Craft
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347:(in marine applications)
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33:is a thrust-generating
477:University of Maryland
430:, Jane's, 1980. p.725.
411:, Jane's, 1980. p.704.
341:(a form of jet engine)
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16:Air moving arrangement
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280:aircraft such as the
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94:Bernoulli's principle
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232:reciprocating engine
392:Kotwani, Kailash; "
83:The duct increases
470:Pereira, Jason L.
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51:shrouded propeller
29:In aeronautics, a
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304:Glow plug engines
269:Ducted fan on an
226:, while military
156:Ducted propulsion
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506:Ventilation fans
501:Aircraft engines
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446:. Archived from
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345:Ducted propeller
191:aerodynamic drag
47:ducted propeller
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357:Avian Gyroplane
339:Geared turbofan
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187:angle of attack
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383:", NASA, 2002.
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351:RFB Fantrainer
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326:Martin Jetpack
296:model aircraft
240:electric motor
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59:shrouded rotor
35:mechanical fan
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453:on 2014-01-02
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236:Wankel engine
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455:. Retrieved
448:the original
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198:Applications
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78:powered lift
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252:helicopters
248:tail rotors
220:gas turbine
168:Limitations
490:Categories
474:p147+p11.
457:2014-01-02
368:References
286:hovercraft
144:Powerplant
74:hovercraft
66:aeroplanes
31:ducted fan
244:Fenestron
224:airliners
39:propeller
24:Bell X-22
361:autogyro
333:See also
308:turbojet
228:fighters
216:turbofan
185:At high
70:airships
294:Among
104:Design
85:thrust
76:, and
451:(PDF)
444:(PDF)
313:Most
238:, or
324:The
278:VTOL
121:Duct
55:VTOL
43:duct
250:on
112:Fan
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49:or
37:or
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416:^
401:^
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363:)
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Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
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