A New Resonant Based Method for the Measurement of Turbine Blade Tip Clearance

Measurement of turbine blade tip clearance is necessary for active control systems for maintaining the optimized clearance. Improved blade tip clearance can provide a signifi cant reduction in specifi c fuel consumption and time-on-wing, and improvements in engine effi ciency as well as payload capabilities in high pressure compressors and high pressure turbines. Reported works on blade tip clearance measurement in rockets, gas engines and steam turbines has the capability to measure the tip clearance as well as time of arrival. Eddy current sensors, due to their noncontact sensing requirements, low power consumption, insensitivity to contaminants are most viable for detecting the turbine blade parameters. Resonating cantilever beam with piezoelectric excitation and detection with a magnet at the end as tip mass has been reported as eddy current based thickness measurement system. This paper discusses on extending the same principle for eddy current based turbine blade tip clearance measurement system. The work focusses on demonstrating the validity of the concept proposed for measuring tip clearance using a laboratory test apparatus, and to outline future course of action for application in aircraft engines.