双转子-中介轴承系统非线性振动特性

针对航空发动机双转子-中介轴承系统建立了简化动力学模型,考虑了中介轴承分数指数非线性、径向游隙和参数激励等非线性因素,以及高低转子系统的双频不平衡激励。采用数值积分方法求解获得系统的非线性振动响应,发现高低压转子分别通过系统一阶临界转速时引起的主共振附近转速区域内均存在振动突跳和双稳态现象,并分析了偏心距、转速比、中介轴承刚度、滚子数目及径向游隙对系统振动突跳与双稳态特性的影响。结果表明:减小转子偏心距能有效降低相应的共振峰峰值并抑制振动突跳行为,但双稳态区间会变宽;提高高低压转子的转速比将引起两个共振峰间距变大,但共振峰对应的转速之比约等于转速比;在一定范围内增大中介轴承刚度、增加滚子数目或减小径向游隙均可使双稳态区间变窄。研究成果有助于认识中介轴承的本质非线性特性对双转子系统非线性振动特性的影响,为提高航空发动机转子系统的运行稳定性提供了一定的理论指导。

Nonlinear vibration characteristics of a dual-rotor system with inter-shaft bearing

Here, a simplified dynamic model for a dual-rotor system with inter-shaft bearing in aero-engine was established considering fraction exponent type nonlinearity of inter-shaft bearing, radial clearance and parametric excitations etc. nonlinear factors as well as dual-frequency unbalance excitations of the dual-rotor system. Nonlinear vibration responses of the system are solved using the numerical integration method. Their characteristics and effects of eccentricity, rotating speed ratio, bearing stiffness, roller number and radial clearance of the inter-shaft bearing on them were studied. The results showed that vibration jump and bi-stable phenomena are observed when rotating speed passing through the first critical speed of the system;decrease in rotor eccentricity can effectively reduce corresponding resonance peak values and suppress vibration jump behavior, but the rotating speed interval for bi-stable state is widened;increase in the rotating speed ratio of higher pressure rotor and lower pressure one can cause the distance between two resonance peaks to be enlarged, but the ratio of two rotating speeds corresponding to two resonant peaks is approximately equal to the former;increasing inter-shaft bearing’s stiffness or roller number, or decreasing its radial clearance can cause the rotating speed interval for bi-stable state to be narrowed;these results are helpful for understanding nonlinear characteristics of inter-shaft bearing and their effects on nonlinear vibration features of the dual-rotor system, and can provide a certain theoretical guidance for improving the operation stability of aero-engine rotor systems.