失衡旋翼的直升机自激振动分析模型

 直升机使用中很可能出现旋翼各片桨叶特性不一致的情况,为了研究失衡旋翼对直升机自激振动的影响,建立了适用于地面、悬停及前飞状态的旋翼/机体耦合动稳定性分析模型。采用当量铰旋翼模型,计入动力入流的影响,分别在旋转坐标系和固定坐标系中建立了桨叶及机体的动力学方程。以减摆器失效对直升机地面共振的影响为例,对桨叶及机体的时域响应进行了非线性数值仿真,用Floquet传递矩阵法计算了摆振后退型模态频率及阻尼,并用时域分析进行了检验。结果表明,其中一个减摆器失效后,各片桨叶摆振运动特性相差很大,系统的摆振后退型模态阻尼下降幅度高达60%以上。

Analytical Model of Helicopter Self-Excitation with Unbalanced Rotor

Helicopter rotor blade dissimilarities such as blade to balde aerodynamic,stiffness,mass and damping unbalanced are most likely to ccour in operations.To study the effects of blade dissimilarities to helicopter self-excitations,analytical model of rotor/fuselage coupled stability is presented which is appropriate to helicopter ground resonance,hovering or trimmed flight air resonance.Equivalent hinged stiffness rotor blade and dynamic inflow model are taken into account.Dynamic equations of each blade and fuselage motions are derived,respectively,at rotating and fixed frame coordinates.The model is then employed in study of the effects of a damper failure on ground resonance stability.Numerical simulations are conducted to demonstrate the blade flap,lag,fuselage roll and pitch responses.The regressive lag modal damping is resolved with Floquet transform matrix technology and verified by time-domain analysis.It shows that the characteristics of each blade lead-lag behavior is very dissimilar arising from a damper failure,and the regressive lag modal damping has above 60% decrement.