Design And Analysis Of Active Swept-tip Rotor Dynamics

As one of the key components of helicopter,rotor is working in the complex flow field environment,improving the aerodynamic effect of rotor has always been the focus of helicopter rotor research.Compared with the traditional rectangular blade,the swept-tip blade rotor can reduce the compressibility of the air around the forward blade and delay the occurrence of the shock wave of the forward blade,so as to increase the drag divergent Mach number of the forward blade and improve the aerodynamic performance of the rotor.At the same time,blade tip back sweep will cause the center of gravity in chord direction to move backward,which will strengthen the aeroelastic coupling effect of the rotor and lead to the blade is prone to dynamic instability.Based on the multi-body dynamics and Hamilton principle,in which the moderate deformation beam element model is used as the blade structure model,the two-dimensional section quasi-steady aerodynamic model is used as the blade aerodynamic model,the Dress linear inflow model and the nonlinear generalized dynamic inflow model are used as the rotor inflow model,the aeroelastic coupling dynamic analysis model of the swept-tip blade rotor is established.The accuracy of the nonlinear generalized dynamic inflow model is verified by 2MRTS rotor experimental data of NASA.The accuracy of the aeroelastic coupling dynamic model of the rotor is verified by the model of the rotor blade of BO105.Based on the parameters of the rotor blade model of BO105,the numerical analysis is carried out to investigate the influence of tip back sweep on rotor dynamic characteristics,dynamic load and aeroelastic stability.The results show that the first-order torsional frequency of the blade increases with the increase of the tip sweep angle,while the tip sweep has a great influence on the torsional load of the blade section,and the first-order lag damping of the blade decreases with the increase of the sweep angle.Finally,a set of driving mechanism based on shape memory alloy wire is designed,which can realize the variable swept angle of the tip.The working principle and the structural design process of shape memory alloy driver are introduced in detail,and the strength and rigidity of the key components of the driver are checked and analyzed by ANSYS finite element numerical software.