Non-Contact Measurement of Blade Vibration in an Axial Compressor

Area of Science:

• Mechanical Engineering
• Aerospace Engineering
• Vibrational Analysis

Background:

• Complex blade responses like rotating stall and resonances challenge current engine monitoring.
• State-of-the-art tip-timing systems and operator expertise are often insufficient for accurate detection.
• Previous studies in Poland used limited sensors, hindering the observation of simultaneous or higher-order modes.

Purpose of the Study:

• To analyze forced vibrations of axial compressor blades in a SO-3 turbojet engine.
• To observe simultaneous responses and higher-order modes using a multichannel tip-timing system.
• To identify potential failure symptoms by comparing blade responses in healthy and unhealthy engine configurations.

Main Methods:

• Utilized a multichannel tip-timing system for enhanced data acquisition.
• Applied all-blade spectrum analysis and circumferential fitting to a harmonic oscillator model.
• Calculated Pearson coefficient of correlation to validate fitting accuracy.
• Developed a modal solver for on-the-fly tracking of vibration frequency and engine order.

Main Results:

• Observed simultaneous responses and higher-order modes previously difficult to detect.
• Successfully distinguished blade responses between healthy and unhealthy engine states.
• Validated the effectiveness of the harmonic oscillator model and Pearson correlation for fitting accuracy.
• Demonstrated the capability of the modal solver to track synchronous and asynchronous vibrations.

Conclusions:

• The multichannel tip-timing system significantly improves the observation of complex blade vibrations.
• The developed analysis methods aid in identifying potential engine failures and avoiding operator misinterpretations.
• The proposed modal solver offers an efficient and accurate approach to analyzing engine vibrations, reducing configuration workload.