垂直着陆中直升机旋翼动力学行为研究

Dynamic behaviors of helicopter rotor in vertical landing

提出了直升机垂直着陆撞击激起旋翼扰动的动力学模型,为预估粗暴着陆时起落架载荷和旋翼液压阻尼器轴向速度幅值给出了一种数值模拟方法。以弹性轴承旋翼直升机为例,对垂直着陆时直升机机体、起落架、旋翼桨叶及阻尼器的动力响应进行了数值模拟,分析了着陆撞击引起机体和旋翼扰动的力学机理,可知在起落架触地后的第1个振荡周期中,各片桨叶将经历其不同的摆振幅值,并激起旋翼摆振后退型响应。着陆撞击引起桨叶的大扰动,将冲开阻尼器的定压安全活门,严重降低其等效阻尼。随机着陆时,起落架触地速度及过载系数、旋翼挥舞及摆振幅度和阻尼器速度峰值等动态参数由于着陆时机体的姿态角及角速度不同呈现很大的分散性,其分散性与着陆高度有关。

A dynamic model for helicopter rotor perturbation excited by impact of vertical landing is proposed,and a numerical simulation method is given to predict landing gear loading and the axial velocity amplitude of hydraulic lag damper in hard landing.Dynamic responses of helicopter fuselage,landing gears,rotor blades and lag dampers are numerical simulated in the vertical landing of an elastic globe-hinge rotor helicopter.The mechanical mechanism of lead-lag disturbance of the rotor blade due to the landing impact is analyzed.It is found that in the first period of oscillation after landing,each blade will undergo different amplitude of lead-lag displacement and result in response of regressive lag mode of rotor.Large disturbance of the rotor blade caused by landing impact will blow off the relieve valve of the damper,significantly decreasing the equivalent damping of the damper.As the sample helicopter undergoes a random vertical landing,the dynamic parameters such as impact velocities and overload factors of landing gears,the amplitude of blade flap and lead-lag displacement,and axial velocity of the damper are shown to be significantly scattered due to different attitudes and angular velocities of the airframe at landing,and the scatter depends on landing altitude.