航空发动机轴承内环松动理论研究

Theoretical Investigation on Loose Inner Ring of Aero-engine Bearing

研究了轴承内环松动的航空发动机转子系统的振动特性。结合内环间隙的轴承组件的结构和几何特点,研究轴承内环和锁紧螺母之间的相对运动关系。在此基础上提出了轴承内环和锁紧螺母之间滑动摩擦载荷的计算方法。建立了带有轴承内环间隙的竖式转子的动力学方程。该方程考虑了内环间隙带来的刚度非线性以及内环和锁紧螺母之间的摩擦载荷带来的阻尼非线性。数值求解动力学方程,得到转子系统的振动响应如波形、频谱和轴心轨迹等。定量研究转子结构参数,如转子的不平衡量、内环间隙尺寸和锁紧螺母拧紧力矩等对转子振动特性的影响。结果表明:内环端面和锁紧螺母之间的内摩擦取决于它们的相对运动关系,正比于锁紧螺母拧紧力矩,并可能促进转子同步正进动,进而导致转子失稳;转子失稳时,振动响应包含系统固有频率、工频及固有频率和工频的差频3种等频率成分;转子不平衡量、内环间隙大小和锁紧螺母拧紧力矩等均对转子的失稳产生影响;合理控制这些参数可以避免因内环松动导致的转子失稳。

The investigation on dynamical behavior of an aero-engine rotor system with loose inner ring was performed.The relative motion between the inner ring and the lock nut was proposed according to the geometrical and structural features of a loose inner ring,based on which the calculation method of the sliding frictional load on the lock nut was presented. This project set up a model for a vertically assembled rotor with loose inner ring,which accounted for both the stiffness nonlinearity and the damp nonlinearity introduced by the clearance and the frictional load on the lock nut respectively. The dynamical equation was solved numerically,which gave the dynamical responses of the rotor system,like wave plot,frequency spectrum and locus of the disk center,etc. The influences of the structural parameters on the rotor,say,the unbalance mass of the rotor,the clearance between the inner ring and the journal,the tightening torque of the lock nut,were identified quantitatively. It turned out that the synchronous forward whirl was promoted and the instability of the rotor was possibly to occur due to the internal friction dependent on relative sliding motion and proportional to the tightening torque; a rotor instability was observed with frequencies,say,the nature frequency,the rotating frequency,and the difference between them; the boundary of rotor instability was defined in terms of parameters,say,unbalance mass,the clearance between the inner ring and the journal and the tightening torque; an appropriate parameter condition was of significance to avoid the rotor instability.