Research on Aerodynamic Characteristics of Discrete Rotor for Ultrahigh-Speed Rotorcraft

To further enhance the speed of vertical takeoff and landing aircraft, rotor stowage during high-speed flight is essential and allows conversion to a fixed-wing mode. This paper introduces the concept of a discrete rotor for ultrahigh-speed helicopters, where each blade of the main rotor is divided into multiple independent single-blade rotors. An aerodynamic analysis model based on the free-wake method incorporating the blade flapping motion equations and the wind-tunnel trim model is developed. Under the premise of identical thrust coefficients, the simulation results based on the model demonstrate that, due to the significant reduction in wake interaction between blades, both single-blade rotor and discrete rotor improve the aerodynamic efficiency compared to the classic multiblade rotor under hover and most forward flight conditions. This efficiency advantage initially increases with the rising forward flight speed but subsequently diminishes. The maximum relative power load factor of the single-blade rotor and discrete rotor compared with the classic multiblade rotor is 12.5%. To further validate the conclusions, experimental study is conducted in a 0.75 m diameter wind tunnel. The test results demonstrate that both single-blade rotor and discrete rotor exhibit significant improvements in aerodynamic efficiency compared with the classic multiblade rotor.