Evaluation of hovering thrust performance of shrouded rotors for multi-rotor UAVs to reduce weight

In this study, we experimentally evaluated the hovering performance of shrouded rotors for small multi-rotor unmanned aerial vehicles (UAVs). In a shrouded rotor, the rotor is surrounded by a round duct. This rotor is superior to normal open rotors because it protects the rotary wing, reduces noise, and improves hovering performance. However, shrouded rotors have not been used much in small UAVs because they increase the weight of the UAV body. To design a shroud that maintains the hovering performance at a reduced weight, we evaluated the effects of different shroud shapes on the hovering performance. We examined three components of a shroud that affect the aerodynamic performance: (1) the shroud position to the rotor, (2) the diffuser length, and (3) the length of the inlet curve. The experimental results confirmed that the hovering performance was improved with a compact shrouded rotor compared to an open rotor. We were able to reduce the shroud weight and maintain the improved hovering performance of the shrouded rotor for small UAV flight.