ductedfan

A ducted fan is a propulsion device in which a rotor, usually a propeller or axial-flow fan, is mounted inside a cylindrical duct or shroud. The enclosing duct directs and confines the airflow, producing an annular jet that can increase thrust for a given rotor speed and reduce aerodynamic noise by shielding the blades from direct view.

Operation and design considerations: The duct helps convert a portion of the rotor’s energy into a higher static pressure, improving thrust especially at low forward speeds. Key design parameters include the fan diameter, the length and shape of the duct, inlet lip geometry, and blade count. When well matched to the rotor, a ducted fan can offer higher thrust efficiency at hover and takeoff conditions and can help stabilize the flow entering the rotor.

Advantages: Ducted fans provide strong static thrust, potential noise reduction, and improved safety for ground personnel due to the enclosed, non-visible rotating blades. They are well suited to compact vertical takeoff and landing configurations and can enable shorter-wing aircraft designs.

Disadvantages: The added duct increases weight and aerodynamic drag, complicates fabrication and maintenance, and can reduce efficiency at higher forward speeds if the ducting is not optimized. Performance is sensitive to manufacturing tolerances and boundary-layer behavior.

Applications and history: The concept has been explored in aviation since the early 20th century and remains of interest for experimental aircraft, unmanned aerial vehicles, and some VTOL and urban air mobility concepts. Ducted fans are chosen when high thrust at low speeds and safety considerations outweigh the penalties of extra mass and drag.