基于机匣应变的航空发动机碰摩故障识别

Aero-Engine Rub-Impact Fault Identification Based on Casing Strain in Flight

针对双转子航空发动机采用柔性机匣设计理念,提出了在进气机匣或中介机匣承力支板加装应变桥路,从机匣动应变中提取特征频率来识别发动机转静碰摩故障的一种方法。建立了简化的转子-机匣碰摩动力学模型,分析得出了双转子发动机转静碰摩特征频率,利用该特征频率准确识别出了某型发动机飞行试验中多次转静碰摩故障。理论分析和飞行试验表明:机匣应变能够灵敏的拾取转静碰摩振动信号;双转子发动机发生转静碰摩时,振动频谱中会出现mΩH ±nΩL高低压转频组合频率成分,可依据该组合频率来判断碰摩故障是否发生;振动频谱中出现mΩH ±ΩL组合频率成分并不能定位高压转子发生碰摩,同理,振动频谱中出现ΩH ±nΩL组合频率成分也不能定位低压转子发生碰摩。

A method for identification aero-engine rotor-stator rub-impact fault is proposed in view of the concept of the flexible casing design for dual-shaft aero- engine. Rub-impact is recognized through seeking the characteristic frequencies from dynamic strain before strain bridges should be installed in the inlet or intermediate casing. A simplified rotor-casing rub-impact dynamics model is established, and the dual-shaft engine rubbing characteristic frequencies are analyzed. Through seeking the characteristic frequencies several rub-impact faults are identified accurately in flight test at a certain aero-engine. Theoretical analysis and flight test show that the casing strain can sensitively pick up rub-impact vibration signals. When rubimpact fault occurs the combined frequencies of the high-rotor and low-rotor rotational frequency mΩH ±nΩL will appear in vibration spectrum, and the rub-impact fault can be judged from the combined frequencies. The combination frequencies mΩH ±ΩL appeared in vibration spectrum are felt to locate a high-pressure rotor rubbing. Similarly, the combination frequencies ΩH ±nΩL are felt to a locate low-pressure rotor rubbing.