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Garcia I.,University of the Basque Country | Zubia J.,University of the Basque Country | Berganza A.,University of the Basque Country | Beloki J.,Aeronautical Technologies Center | And 5 more authors.
Journal of Lightwave Technology | Year: 2015

Tip clearance is critical to the performance of rotating turbomachinery. The objective of this paper is to develop a noncontact sensor with a precision of 30 μm to measure tip clearance in a turbine rig assembled in a wind tunnel. To carry out the measurements, an optical sensor whose main component is a bundle of optical fibers is employed. We use four different configurations of this sensor, which are tested in two distinct turbines with the aim of minimizing the effect of the noise on the repeatability of the measurements. Each configuration serves to increase the precision until the required performance is achieved for the measurement of the tip clearance. Our results may be helpful to develop applications related to structural health monitoring or active clearance-control systems. © 2015 IEEE. Source


Garcia I.,University of the Basque Country | Beloki J.,Aeronautical Technologies Center | Zubia J.,University of the Basque Country | Durana G.,University of the Basque Country | Aldabaldetreku G.,University of the Basque Country
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2013

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. © 2013 SPIE. Source


Zubia J.,University of the Basque Country | Garcia I.,University of the Basque Country | Berganza A.,University of the Basque Country | Beloki J.,Aeronautical Technologies Center | And 2 more authors.
International Conference on Transparent Optical Networks | Year: 2014

For the last few years, we have been carrying out tip-clearance (TC) measurements in turbine rigs using optical sensors in collaboration with the Aeronautical Technologies Center. Several turbines with completely different blade profiles have been tested with satisfying results. The reflective intensity-modulated sensor used in these tests is based on a trifurcated bundle of optical fibers. This sensor is the ideal candidate for TC measurements because of its low cost, simplicity, robustness and the capability of performing tip-timing measurements (TT) employing the same probe. In the case of TC measurements, the main requirement is a precision of at least 30 μm. In order to get this precision, the latest improvements of the sensor have been focused on reducing the modal noise at the endface of the transmitting fiber of the bundle. For this purpose, different approaches were developed using mode-scramblers, plastic optical fibers and a single-mode illuminating fiber. The results obtained in the tests demonstrate that it is possible to achieve the demanded precision. Hence, in next test campaign, three sensors will be used to determine clearance at three different points of a rotating disk that belongs to a real aircraft engine. © 2014 IEEE. Source


Zubia J.,University of the Basque Country | Garcia I.,University of the Basque Country | Beloki J.,Aeronautical Technologies Center | Durana G.,University of the Basque Country | And 3 more authors.
Proceedings of 22nd International Conference on Plastical Optical Fibers, POF 2013 | Year: 2013

The first sensor we present is a low-cost current sensor, whose operational principle is Faraday rotation of a light beam through a magneto-optical material under the influence of a magnetic field. The results show that the sensor presents high sensitivity and a linear response in the range from 0 to 800A. The second sensor measures tip clearance (TC) and blade-tip timing measurements (BTT). Both are critical parameters in turbine assessment. For BTT measurements, the travelling wave spectrum was obtained and with regard to TC, the mean error obtained was 34 μm. Source


Garcia I.,University of the Basque Country | Zubia J.,University of the Basque Country | Berganza A.,University of the Basque Country | Beloki J.,Aeronautical Technologies Center | And 2 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

The influence of the tip clearance on the performance of rotating turbo machinery is well known. The objective of this work was to measure this parameter using a non-contact sensor with a precision of 30 μm in a real turbine. An optical sensor whose main component is a bundle of optical fibers was selected to carry out the measurements. Three different configurations of the sensor have been tested by taking measurements on two distinct turbines. Tip-clearance measurements are achieved with the desired precision, providing the opportunity to develop applications related to structural health monitoring or active clearance-control systems. © 2014 SPIE. Source

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