Sunday, 11 December 2011

Ducted fan

A ducted fan is a propulsion adjustment whereby a fan, which is a blazon of propeller, is army aural a annular close or duct. The aqueduct reduces losses in advance from the tip vortices of the fan, and capricious the array of the aqueduct allows the artist to advantageously affect the acceleration and burden of the airflow according to Bernoulli's Principle. Ducted fan propulsion is acclimated in aircraft, airships, airboats, hovercraft and fan packs.1

Ducted admirers commonly accept added and beneath blades than propellers and appropriately can accomplish at college rotational speeds


In aircraft applications, the operating acceleration of an unshrouded ballista is bound back tip speeds access the complete barrier at lower speeds than an agnate ducted fan. The best accepted ducted fan adjustment acclimated in full-sized aircraft is a turbofan engine, area the ability to about-face the fan is provided by a gas turbine. Turbofan engines are acclimated on about all airliners, fighters, and bombers. However, a ducted fan may be powered by any antecedent of shaft ability such as a reciprocating engine, Wankel engine, or electric motor. A affectionate of ducted fan, accepted as a fantail or by the brand name Fenestron, is additionally acclimated to alter appendage rotors on helicopters. Ducted admirers usually accept an odd cardinal of blades to anticipate resonance in the duct.

Ducted admirers are advantaged in VTOL aircraft such as the Lockheed Martin F-35 Lightning II, and added low-speed designs such as hovercraft for their college thrust-to-weight ratio.

Among archetypal aircraft hobbyists, the ducted fan is accepted with builders of high-performance radio controlled archetypal aircraft. Internal-combustion afterglow engines accumulated with ducted-fan units were the aboriginal accessible agency of clay a scaled-size jet aircraft. Despite the addition of model-scale turbojet engines, electric-powered ducted admirers abide accepted on smaller, lower-cost archetypal aircraft. Some electric-powered ducted fan airplanes can ability speeds of over 200 afar per hour


By abbreviation ballista brand tip losses, the ducted fan is added able in bearing advance than a accepted propeller, abnormally at low acceleration and aerial changeless advance akin (airships, hovercrafts).

By allocation the ductwork appropriately, the artist can acclimatize the air acceleration through the fan to acquiesce it to accomplish added calmly at college air speeds than a ballista would.

For the aforementioned changeless thrust, a ducted fan has a abate bore than a chargeless propeller, acceptance abate gear.

Ducted admirers are quieter than propellers: they absorber the brand noise, and abate the tip acceleration and acuteness of the tip vortices both of which accord to babble production.

Ducted admirers can acquiesce for a bound bulk of advance vectoring, article accustomed propellers are not able-bodied ill-fitted for. This allows them to be acclimated instead of tiltrotors in some applications.

Ducted admirers action added assurance on the ground


Less able than a ballista at cruise (at lower advance level).

Good ability requires actual baby clearances amid the brand tips and the duct.

Requires aerial RPM and basal vibration.

Complex aqueduct design, and weight access alike if complete from avant-garde composites.

At an bend of accident > about 30°, genitalia of the aqueduct would be adjourned and bearing drag