有初弯的刚度非对称转子的动力学特性分析及实验研究

Theoretical and Experimental Analysis on an Unbalanced Rotor with Asymmetric Rigidity and Initial Bending

对刚度不对称转子在有初始弯曲时的稳定性和动态响应特性进行了理论分析和实验研究。重点研究了初弯方向与原始不平衡方向间夹角对系统响应特性的影响 ,提出了识别转子初弯和刚度不对称情形的特征量和诊断方法。研究表明 :初始弯曲转子不仅在低转速时的振幅趋于初始弯曲值 ,而且随初始弯曲与不平衡间夹角的变化和初始弯曲与偏心距比值大小的变化振幅曲线出现很大的差异。特别是在大夹角情形下 ,夹角对振幅曲线的影响较大。当初始弯曲小于偏心距时 ,临界前振幅会随着转速升高而下降然后又上升 ,而当初始弯曲大于偏心距时 ,临界后振幅会随着转速升高而下降然后又上升。在临界前刚度不对称转子的幅频曲线有副临界现象 ,转子运转频率处于两个自然频率间时系统会失稳 ;

Dynamic behaviors of an unbalanced rotor with asymmetric rigidity and initial bending are investigated theoretically and experimentally. The dynamic response and stability of the unbalanced rotor in four combined cases of asymmetric rigidity and initial bending are presented. The following conclusions are drew: ⑴The amplitude of a rotor with initial bending is equal approximately to the initial bending value at very low rotating speed. The angle between initial bending and unbalance play a key role in the rotor vibration responses. When the angle is bigger than 90 degree, initial bending will reduce the influence of unbalance. Particularly for enough large angle, the amplitude will decrease with speed increasing before critical speed if initial bending is less than unbalance eccentricity and after critical speed if initial bending is bigger than unbalance eccentricity; ⑵There are double frequency vibrations in an asymmetric rotor. When the rotating speed lies in between two system natural bending critical speeds, the system will lose stability; ⑶The larger the unbalance parameter is, the bigger the changing of the amplitude speed curves is. Experimental study of a rotor with initial bending and unbalance is conducted, and the theoretical results coincide very well with the experimental ones. Some features are obtained for asymmetric rigidity rotor by spectrum analysis and response orbits analysis. It is found that the fundamental frequency component is much less than the 2X component at low rotating speed without initial bending and is much larger than the 2X component at low rotating speed with initial bending. The above conclusions may be applied to the diagnosing of asymmetric rigidity and initial bending of rotors.