INTEGRATED FIBER OPTIC LIGHT PROBE - MEASUREMENT OF STATIC DEFLECTIONS IN ROTATING TURBOMACHINERY

This paper describes the design, fabrication, and testing of an integr ated fiber optic light probe system for monitoring blade tip deflectio ns, vibrational modes, and changes in blade tip clearances in the comp ressor stage of rotating turbomachinery. The system comprises a set of integrated fiber optic light probes which are positioned to detect th e passing blade tip at the lending and the trailing edges. In this con figuration measurements of both blade vibrations and steady-state blad e deflection can be obtained from the timing information provided by e ach light probe, which comprises an integrated fiber optic transmittin g channel and a number of high numerical aperture receiving fibers, al l mounted in the same cylindrical housing. A spatial resolution of 50 mu m is possible with the integrated fiber optic technology, while kee ping the outer diameter below 2.5 mm. Additionally, one fiber sensor p rovides a capability of monitoring changes in the blade tip clearance of the order of 10 mu m. Measurements from a single stage compressor f acility and an engine-fan rig in a 9 ftx15 ft subsonic wind tunnel are presented. (C) 1996 American Institute of Physics.