The growing interest on improving the efficiency of hybrid unmanned aerial vehicles (UAVs) is derived from their capability to perform vertical take-off and landing (VTOL), in addition to forward flight. This paper aims to analyse the advantages of integrating distributed electric propulsion (DEP) with ducted-fan technology to improve the performance of UAVs during VTOL and hover flight.
Their investigation starts with a flying wing configuration incorporating two embedded wing ducted-fans equipped with front-mounted tilting dual ducted-fans system. Experimental tests comparing ducted-fan and unducted propulsion system under hover conditions are presented. The VTOL and hover capabilities are validated through outdoor flight tests of both XEVTOL-2FNW and XEVTOL-4FNW prototypes during multirotor flight. Finally, wind tunnel experiments assess the impact of wing-embedded ducts on aerodynamic efficiency during fixed-wing flight.
Experimental propulsion tests showed a 35% increase in thrust for ducted-fan compared to free rotor. Outdoor flight tests validated the VTOL and hovering capabilities of both the XEVTOL-2FNW and XEVTOL-4FNW prototypes. The six rotor prototype (XEVTOL-4FNW) demonstrated a 16% higher energy efficiency than the four rotor prototype (XEVTOL-2FNW). Additionally, comparative wind tunnel experiments assessed the influence of wing-embedded ducted-fans on aerodynamic efficiency during fixed-wing flight.
This research advances hybrid VTOL technology by integrating DEP with embedded ducted-fan systems to enhance multirotor flight performance. The experimental study highlights thrust improvements from ducted-fans, assesses energy efficiency via outdoor flight tests with prototypes, and compares these findings with the aerodynamic impacts of embedded wing ducted-fans.
