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Proceedings Paper

Turbine-blade tip clearance and tip timing measurements using an optical fiber bundle sensor
Author(s): Iker Garcia; Josu Beloki; Joseba Zubia; Gaizka Durana; Gotzon Aldabaldetreku
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Paper Abstract

Traditional limitations of capacitive, inductive or discharging probe sensor for tip timing and tip clearance measurements are overcome by reflective intensity modulated optical fiber sensors. This paper presents the signals and results corresponding to a one stage turbine rig which rotor has 146 blades, obtained from a transonic wind-tunnel test. The probe is based on a trifurcated bundle of optical fibers that is mounted on turbine casing. It is composed of a central illuminating fiber that guides the light from a laser to the turbine blade, and two concentric rings of receiving fibers that collect the reflected light. Two photodetectors turn this reflected light signal from the receiving rings into voltage. The electrical signals are acquired and saved by a high-sample-rate oscilloscope. In tip clearance calculations the ratio of the signals provided by each ring of receiving fibers is evaluated and translated into distance. In the case of tip timing measurements, only one of the signals is considered to get the arrival time of the blade. The differences between the real and theoretical arrival times of the blades are used to obtain the deflections amplitude. The system provides the travelling wave spectrum, which presents the average vibration amplitude of the blades at a certain nodal diameter. The reliability of the results in the turbine rig testing facilities suggests the possibility of performing these measurements in real turbines under real working conditions.

Paper Details

Date Published: 13 May 2013
PDF: 9 pages
Proc. SPIE 8788, Optical Measurement Systems for Industrial Inspection VIII, 87883H (13 May 2013); doi: 10.1117/12.2020540
Show Author Affiliations
Iker Garcia, Univ. of the Basque Country (Spain)
Josu Beloki, Aeronautical Technologies Ctr. (Spain)
Joseba Zubia, Univ. of the Basque Country (Spain)
Gaizka Durana, Univ. of the Basque Country (Spain)
Gotzon Aldabaldetreku, Univ. of the Basque Country (Spain)

Published in SPIE Proceedings Vol. 8788:
Optical Measurement Systems for Industrial Inspection VIII
Peter H. Lehmann; Wolfgang Osten; Armando Albertazzi, Editor(s)

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