含滚动轴承径向游隙的航空发动机整机振动响应特征分析

Characteristics Analysis of Aero-Engine Whole Vibration

关键词:  径向游隙  整机振动  有限元模型  赫兹接触力  不平衡力

Key words:  Radial clearance  Whole vibration  Finite element model  Hertz contact force  Unbalanced force

摘要:

针对航空发动机支承系统中各支承处滚动轴承径向游隙对整机振动响应影响的灵敏度问题，建立了含滚动轴承径向游隙的真实发动机转子-支承-机匣整机振动模型，转子与机匣采用有限元模型，支承采用集总质量模型，分别考虑了四个不同支承处的滚动轴承径向游隙和赫兹接触力的强非线性，利用数值积分方法求解耦合系统的响应，分析了整机振动响应特征。对整机振动影响较大的支承S2处，分析了不同转速下，转子、滚动轴承外圈、机匣的响应特征；分析了非线性接触力随时间-滚珠数目变化、以及滚动轴承承载变化规律；分析了该支承处径向游隙对接触力的影响。结果表明:(1)转速越高，随着间隙增大，机匣加速度振幅跳跃和滞后现象越明显，且由于滚动轴承的变刚度，当刚度变化较剧烈时，系统的固有频率被激发，即频率锁定现象；(2)在大间隙下，转速在两阶临界转速之间，转子容易出现时而挤压，时而不挤压滚动轴承外圈的现象，即不稳定现象，可以通过减小径向游隙，从而增加转子的稳定性，同时减小整机振动。

Abstract:

For the sensitivity problem of the effects of rolling bearing radial clearance on the whole vibration at different supports in the aero-engine support system，a model is established for a real engine rotor-bearing-casing. The rotor and casing systems are modeled by means of the finite element model. The support systems are modeled by lumped-mass model. Rolling bearing radial clearance and strong-nonlinearity of Hertz contact force at four different supports are considered. The coupled system response is obtained by the numerical integral method. The characteristics of the whole vibration response are analyzed. For the support S2，which influences the whole vibration larger，the rotor，outer ring of rolling bearing and casing response characteristics at different rotating speeds are analyzed. The nonlinear contact force law which changed with time and rolling numbers and the changed load law of the rolling bearing are analyzed. The influence on contact force by the radical clearance is analyzed. The results show that the higher the rotating speed，as the clearance increases，the more obviously acceleration amplitude jumps and lags and due to the variable stiffness of the rolling bearing，when the stiffness changes fiercely，the natural frequency is excited，that is frequency-locked phenomenon. When the radical clearance is large and the rotating speed is between two order radical speed，the rotor sometimes squeezes and sometimes does not squeeze the outer ring，that is，instability phenomenon occurs. Reducing the radical clearance can increase the rotor stability and reduce the whole vibration.