Key Technology Research On Aerodynamic Shape Of Ducted Co-axial Rotor Uav

The ducted co-axial rotor uav has the advantages of Vertical Take-off and Landing(VTOL),and it has the excellent development potential not only with the characteristics of low noise,high security and flexible operation,but can also offset the effects of torque with two co-axial rotors rotating in the opposite directions.Nevertheless,the flow field characteristic of ducted propeller system is complicated.In this paper,the key technologies involved in the process of design and analysis with ducted co-axial rotor uav have been studied theoretically and numerically.Focus on analyzing aerodynamics of ducted single rotor and ducted co-axial rotor using theoretical computational method derivation and CFD numerical simulation method solution.The specified research including:(1)An aerodynamic configuration of ducted co-axial rotor uav has been proposed.The structure of double propeller,duct and control rudders have been determined.The traditional propeller aerodynamic theory,momentum theory and blade element theory,has been discussed and the combination of momentum theory and blade element theory has been adopted to establish the aerodynamic calculation model.The effect on propeller in duct has been discussed with various duct scale factor,distance between twin-rotor and angle of incidence.It lays a solid foundation for the overall design.(2)The CFD numerical simulation method has been used to calculation the aerodynamic characteristics of single rotor,co-axial rotor,ducted single rotor and ducted co-axial rotor at hover state.The flow field of propeller has been divided into two subzones,one is stationary subzone contains duct and the other is the rotational subzone contains rotors.The interface boundary condition has been established between two domains to keep flux conservation.The aerodynamic performances were numerically solved by Navier-Stokes equations with sliding mesh technique based on Multiple Reference Frame(MRF).The coupling implicit algorithm based on density,spatial discrete method of finite volume and Standard k-epsilon turbulence model has been adopted in establishing CFD solving model,which described the influence of rotation and vortex flow effectively.The mechanism of improving aerodynamic efficiency with installed duct is summarized.(3)A small aerodynamic performance testing platform has been established to measure the advantages of duct.The lift has been tested by various rotation speed and distance between twin-rotor in hover.The numerical simulation method has been proved to be effective by comparing CFD results with test results.These three aerodynamic analysis method in this study offer a new way for the design of ducted co-axial rotor uav.