Double-Ducted Fan as an Effective Lip Separation Control Concept for Vertical-Takeoff-and-Landing Vehicles

This paper describes a novel inlet flow conditioning concept that significantly improves ducted fans’ performance and controllability. High angle-of-attack operation of fans is very common in vertical-takeoff-and-landing systems. The new named double-ducted fan (DDF) uses secondary shroud to control lip-separation-related momentum deficit at the rotor during edgewise flight. DDF helpful wide flight velocity range, its corrective aerodynamic effect becomes more pronounced with increasing velocity. A conventional baseline duct operating 90 deg angle attack compared other designs via three-dimensional, viscous, turbulent computations. custom actuator-disk model replaces zonal computation complex three-dimensional flowfield rotating frame reference. Both hover conditions are considered around unit inside ducts. Significant improvements from several areas vertical thrust enhancement, nose-up pitching moment reduction, recovery through-flow mass rate horizontal range. variable design, partial fan-in-wing implementation introduced.