Study On The Overall Design And Aerodynamic Characteristics Of The Tri-Tilt-rotor UAV With Flying-wing Configuration

Tilt-rotor UAV not only takes into account the characteristics of rotor and fixed-wing UAV,but also can take off and land vertically and fly forward at high speed.In addition,its complicated flight mode brings great aerodynamic influence to UAV.Based on the fiying-wing configuration tri-tilt-rotor UAV as the research object,and according to the problems of small load and short endurance of the traditional tilt-rotor UAV,the paper proposes a configuration scheme of the fiying-wing configuration tilt-rotor UAV with the front and rear three rotor tiltable.Through its calculation,modeling and simulation analysis,a tri-tilt-rotor UAV is designed to meet the mission requirements,and its aerodynamic characteristics are studied by computational fluid dynamics.Firstly,according to the design requirements,the overall configuration is compared and selected.According to the selected fiying-wing spinning office,the overall parameters of tri-tilt-rotor UAV are determined.The calculation,design and modeling of the wing,fuselage,control surface,winglet,power unit and tilting mechanism,as well as the design of landing gear are carried out for the UAV.Then,the multi-reference frame is used to establish a numerical calculation method suitable for the fiying-wing configuration tri-tilt-rotor UAV,and CATIA software is used to carry out the reverse modeling of propeller CAD.The validity of the numerical calculation method is verified by comparing the experimental and calculated values of propeller tension and power.Finally,based on the established aerodynamic model and numerical calculation method,the Fluent software is used to calculate and analyze the vertical climb state,forward flight and tilting transition state of the tri-tilt-rotor UAV in hover,the aerodynamic influence of the propeller on the airframe,the lateral heading and longitudinal static stability of the UAV in forward flight state.The simulation results show that the load of rotor on the airframe can be almost ignored in hovering state,but in vertical climbing state,the existence of rotor causes the airframe to suffer greater resistance and greater pitching moment.In the forward flight state,the UAV has good lateral heading and longitudinal static stability.The existence of rotor can effectively improve the lift of the airframe,but the interference of rotor reduces the lift-to-drag ratio of the whole aircraft.In the transitional state of tilting,with the increase of tilting angle,the lift and resistance decrease first and then increase,and the body tends to rise first and then lower its head.In this paper,the aerodynamic characteristic curves of different flight states are calculated and analyzed,which provides a theoretical basis for the design and subsequent control research of the tri-tilt-rotor UAV.