航空发动机双转子轴间碰摩非线性动力学特性

Nonlinear Dynamics of Dual-Rotor System in Aero-Engine under Rub-Impact Between Shafts

航空发动机双转子之间通常采用封严结构,容易导致双转子发生轴间碰摩。针对双转子轴间碰摩问题,推导了轴间碰摩力模型,结合实体有限元法建立了双转子轴间碰摩动力学模型,并将固定模态界面综合法和数值方法结合,提出了此类高维转子轴间碰摩响应的一般计算流程。基于该计算流程,详细研究了轴间碰摩导致的双转子复杂非线性动力学特性。结果表明:双转子发生轴间碰摩时,主要存在持续碰摩、间歇碰摩和自激振动三种碰摩状态。持续碰摩主要引起双转子间振动耦合;间歇碰摩对转子产生较明显冲击特征,导致转子频域响应中出现多阶模态频率成分及组合频率成分;自激振动则是由切向摩擦诱发的、转子正进动模态频率成分主导的一种运动状态,此时转子呈正向涡动,但振动幅值很高,对转子危害极大。通过减小摩擦系数或碰摩刚度,能显著减小自激振动发生的转速范围,提升转子运行稳定性。

Sealing structure is usually used in dual-rotor system of aero-engine,which can easily lead to rub-impact between shafts.The rub-impact force model between shafts is derived,and the dynamic model of rub-impact is established based on solid finite element method.The general calculation process of rub-impact response between shafts is proposed by combining fixed mode interface synthesis method and numerical method.Based on this calculation process,the nonlinear dynamic characteristics of dual-rotor system caused by rub-impact between shafts were studied in detail.The results show that there are three rub-impact conditions which were continuous rubbing,intermittent rub-impact and self-excited vibration when inter-shaft rub-impact occurs.Continuous rubbing mainly causes vibration coupling between two rotors.Intermittent rub-impact has obvious impact characteristics on the rotor,resulting in multi-order modal components and combined components in the frequency domain response.The self-excited vibration is mainly induced by tangential friction and dominated by the positive precession mode frequency component of the rotor.At this time,the rotor whirls forward while the vibration amplitude is high,which could cause severe damage to the rotor.By reducing the friction coefficient or rubbing stiffness,the speed range of self-excited vibration can be significantly reduced and the rotor operation stability can be improved.