The Faults Diagnosis Of Rotor System Base On Dynamic Stress Measurement Of Elastic Support

The rotor system is the central part of the aero-engine and other rotating machinery. China’s aero-engine development and high-performance engine research have shown that the engine failure caused by the rotor-bearing system has become a major problem in aero-engine development and research. Study on the failure of the rotor system is to prevent the system and the whole engine from possible damage, which is meaningful to national economy and safety.A rat-cage-type elastic support and a squeeze film damper are usually used in small and medium sized aero-engine rotor systems. This article focuses on vibration signal acquisition and analysis methods base on the dynamic stress measurement of elastic supports of rotors. Different ways to obtain the vibration signals for faults diagnosis are showed and the relative results are compared.The elastic support works at relatively low temperature,and it is a static part of the compressor. The rotor vibration can cause alternate stress at the root of the elastic strips of the elastic support, on which tiny sensors such as strain gages are pasted. The vibration signals measured by the strain gages are obtained from the lead wires through the hole or hollow vanes of the case. On one hand, the vibration stress is monitored to ensure that the squeeze film damper works in the linear region, avoiding film shock when it works in the non-linear region. On the other hand, the fault characteristics of the rotor can be extracted from the dynamic stress signal via appropriate analytical methods. Comparing with the signal of accelerometers fitted on the case, the signals obtained directly from the elastic support of the rotor have better quality to show the vibration characteristics of the rotor system. The route through which the vibration of the rotor transfers to the accelerometers is more complicate since the vibration of other parts of the engine is measured by the accelerometers as well. The signals of the accelerometers include the vibration response of other parts except for the rotor, such as the case, the vanes, and the gear-box of the test-bed. Therefore, the fault characteristics extracted from the signals of the accelerometers are not as specific and sensitive as that of the strain gages pasted on the elastic strips.The application of the faults diagnosis method base on the dynamic stress measurement shows that the method is very helpful and efficient to recognize the faults of rotors with elastic supports.