支承非对称对双转子系统动力特性的影响规律

Effect of asymmetrical supports on the dynamic characteristics of a dual-rotor system

支承刚度非对称广泛存在于转子支承系统中,然而非对称支承对工程中双转子系统动力特性的复杂影响规律尚不明确。为此,以典型发动机同向转动的双转子支承系统为研究对象,根据该发动机薄壁柔性机匣支承的特点,提出支承非对称系数指标,研究了支承非对称存在与否及其变化对双转子支承系统临界转速、稳态不平衡响应、进动方向及进动轨迹的影响。研究发现:支承非对称的存在会导致与之相关的振型所对应的正进动临界转速增大、反进动临界转速减小;部分支点在反进动临界转速附近出现响应峰值并且伴随着进动平面内振动相位的变化;转子进动更为复杂,同一个转子上正反进动同时出现,转子特定节点的进动轨迹也会随转速产生较为复杂的变化;进一步研究发现,非对称系数的增大会使得出现反进动的转速和位置区域总体增大,但在特定转速或特定位置反进动区域也可能变小;所得规律可为发动机双转子系统复杂支承条件下的动力学设计及特殊振动现象产生原因阐释提供参考。

The asymmetry of support stiffness widely exists in the rotor support system.However,the complex influence of asymmetric supports on the dynamic characteristics of the dual-rotor system in engineering is not yet very clear.For this reason,a dual-rotor support system rotating in the same direction in a typical engine was taken as a research object.According to the characteristics of the thin-walled flexible casing support of the engine,the index of support asymmetry coefficient was introduced,and the effects of the existence of support asymmetry and its variation on the critical speed,steady-state unbalance response,whirling direction and whirling trajectory of the dual-rotor support system were studied.It is found that the support asymmetry will lead to the increase of forward critical speed and the decrease of backward critical speed corresponding to relevant vibration modes.The response peak at some pivots appears near the critical speed of whirling and it is accompanied by the change of vibration phase in the whirling plane.The whirling of the rotor is more complex.The forward and backward whirling may occur simultaneously on the same rotor,and the whirling trajectory of some specific node of the rotor will change quite complicatedly along with the rotational speed.The further study shows that the increase of asymmetric coefficient will result in an overall increase in the speed and position regions where the backward whirling occurs,but the area of the backward whirling may also decrease in certain specific speed or position.The results provide a reference to the dynamic design of engine dual-rotor systems under complex support conditions and some special vibration phenomena could be explained.