# Advancements and Applications of Rim-Driven Fans in Aerial Vehicles: A Comprehensive Review
## 2 Features and Benefits of the RDF Jet
### Rim-Driven Configuration  
RDFs are primarily distinguished by their shaftless architecture as opposed to traditional motor-propeller designs (Figure 1). A ducted fan drum rotor with attached blades at the outer diameter makes up the actual arrangement. The rotor is housed inside a stator, and it is powered by electromagnetic fields that are modulated between the two components. The controller and power electronic drive circuits between the power source and integrated motor assembly provide optimal modulation. The rotor assembly is suspended and supported by magnetic fields inside the stator (Figure 2). Using torque applied to the drum rotor, which has blades mounted on the revolving shell, the levitated ducted fan, a self-contained electromagnetic propulsor, generates thrust. Using the large surface area and unique physical dimensions of the rotor's outer circle  
Figure 1: (**a**) Layout of a rim-driven fan (RDF), (**b**) configuration of a rim-driven propeller (Copyrright (2023), with permission from Elsevier). Figure 2: Configuration of a rim-driven thruster (RDT). 1. Front Cover, 2. Propellers, 3. Rotor, 4. Magnets, 5. Rotor Sealing, 6. Stator Sealing, 7. Stator, 8. Rear Cover. is essential for developing the most efficient electromagnetic levitation and propulsion mechanism between the rotor and stator. Key to this concept is the novel application of electromagnetic propulsion and the non-contact support system. The fan blades in a rim-driven propeller or turbofan are rotated by the rim, rather than an axis. Under the dynamic magnetic force between the inner rim and outer ring/shell magnets, the rim spins. High-intensity permanent magnet plates, which have no electrical connections, are implanted in the rotor's inner rim. These stators, which are induced by an external power source, are effectively controlled by a high-power circuit. Hence, the stators within the rim of the RDF jet are supplied with significant electrical energy and are regulated through the utilization of a robust and powerful circuitry system. This is how RDF is able to distribute power from the rim to the blades without going via the central shaft. Therefore, more air can enter because there is no central shaft to restrict it. Utilizing a rim-driven method rather than an axis-driven one makes it much easier to resist high torque. Direct power transfer is another distinction between rim-driven and axis-driven systems. With a typical fan, the original driving force is delivered in a two-step indirect way from the turbine to the shaft to the fan blade. Meanwhile, the rotor's power is sent directly from the rim to the fan blade in an RDF. Its greater drivability enables a thicker blade to revolve faster and more easily to satisfy the resistive torque generated by the RDF jet engine's high thrust output. Unlike traditional jet engines that use gas turbines or diesel, the RDF uses an electric motor. Modern electric motor technology is used in the rim-driven motor, drastically increasing its power output per unit of weight. The RDF jet is able to utilize materials with a low specific density. Fiber-reinforced composite (FRC) plastic, ceramic matrix composite metal (CMC), new alloys, and many other composites can be used in the production of housings, wheels, and fans, respectively. Integrating these cutting-edge advances allows the RDF jet to be constructed while meeting stringent mass requirements. RDF jets are compact cubic cylinders with easy installation and alignment. Hence, the implementation of distributed electric propulsion (DEP) can be straightforwardly achieved through the deployment of multiple RDF jets distributed across the entirety of the aircraft. Propulsion systems can harness the advantageous interactions between aerodynamics and propulsion, surpassing the capabilities of traditional setups due to their adaptable placement, scaling, and operational versatility [27; 28].