Tip Timing Based Non-contact Vibration Measurement of Aero-engine Turbine Blades

Non-contact vibration measurement based on tip timing has been widely used in aero-engine blade health monitoring. However, it is different to inspect the vibration of turbine blades with small size in high rotating speeds, temperature and pressure operation. To overcome the difficulty of aero-engine turbine blade measurement, firstly, the optical sensor with cooling channel is designed and a novel air-cooling method is proposed. Secondly, a disk for once-per-revolution (OPR) sensor placement is designed and the black paint is sprayed on the shaft. The OPR signal can be achieved by detecting the intensity change of light as the shaft rotates. Thirdly, the non-contact vibration measurement based on tip timing is conducted to monitor turbine blades, and the resonance frequencies, blade tip vibration amplitude and rotational speeds of blades are obtained. The test results show that the 1st bending mode resonance of the turbine blades occurred at about 8200r/min excited by engine order 12 and 9100r/min excited by engine order 11. Furthermore, the identified vibration parameters from the test have a good match with the results of the numerical calculation. It demonstrates the promise of the proposed non-contact vibration measurement technique based on blade tip timing for health monitoring of aero-engine turbine blades.