The NASA Glenn Research Center is developing a revolutionary engine concept called the Magnetically Levitated Ducted Fan. The objective of this work is to demonstrate the feasibility of a pollution-free electromagnetic propulsor for all-electric flight. This concept will help to reduce harmful emissions, to reduce the Nation's dependence on fossil fuels, and to mitigate many of the concerns and limitations encountered in conventional engine systems such as bearing wear, leaks, seal failure, and friction loss. The general concept is depicted in the following figure.
Early concept of the Magnetically Levitated Ducted Fan.
Long description.
This fully integrated system concept incorporates many advanced technologies into a new aeropropulsion system architecture. The innovative physical layout consists of a ducted fan drum rotor with blades attached at the outer diameter and supported by a stress tuner ring at the inner diameter. The drum rotor is made of composite material and is contained within a static shell assembly, or "stator." Magnetic fields suspend and support the rotor assembly within the stator. The rotor is driven by modulated electromagnetic fields between the rotor and the stator. Optimal modulation will be achieved via the controller and power electronic drive circuitry between the power source and the propulsor. This concept exploits unique physical dimensions and a large available surface area to optimize a custom, integrated electromagnetic system that provides both levitation and propulsion functions. Advanced technologies developed for particle accelerators, and currently under development for maglev trains and rocket launchers, served as pathfinders for adaptation into the application.
Development of this concept was funded through the Revolutionary Aeropropulsion Concepts (RAC) program beginning in 2003. During this first year, the focus of the work was on the development of the magnetic levitation system. The electromagnetic concept under investigation uses permanent magnet elements attached to the outer circumference of the rotor drum and wire coils placed in the stator shell. The permanent magnets are arranged in a Halbach configuration, which results in the production of a sinusoidally varying, periodic magnetic field in the vicinity of the stator coils. This magnetic array configuration was pioneered by Klaus Halbach for use in particle accelerators. When set in motion, the time-varying magnetic fields interact with the passive coils in the stator assembly to produce repulsive forces between the stator and the rotor, providing magnetic suspension. The beauty of this technique is that it is inherently stable once the rotor reaches a critical speed and, thus, requires no active feedback control or superconductivity as seen in many traditional implementations of magnetic suspension.
Small-scale levitation model rotor.
Small-scale levitation model stator.
To date, theoretical calculations have been produced to predict the levitation forces developed by a cylindrical Halbach array and coil assembly. Early experimental hardware was successfully designed and developed that validated the basic principles and the theoretical work. On the basis of these findings, a small-scale system was designed that will serve as a levitation demonstration model. The rotor and stator of the demonstration model are shown in the preceding figures. The purpose of this model is to demonstrate stable suspension of a rotorlike body within a stator assembly.
The next step in the development process will be to further develop the electromagnetic propulsion concept and integrate both the magnetic suspension and propulsion function into a single multifunction assembly. In addition to aircraft engines, this technology has potential application in ultraefficient motors, computer memory systems, manufacturing equipment, and space power systems such as flywheels.
Glenn contact: Dawn C. Emerson, 216-433-8901, Dawn.C.Emerson@nasa.gov
Author: Dawn C. Emerson
Headquarters program office: OAT
Programs/Projects: RAC
Last updated: January 21, 2005
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