In this work, we report a new approach for fabricating a high sensitivity lysozyme biosensing. The aforementioned device consists of an optimized Fabry-Perot micro-cavity (FPC) fabricated onto cleaved end of a standard single mode fibre (SMF). The sensitive part of our device is the external face of the FPC, which was ad-hoc functionalized in order to provide high selectivity and high sensitivity. From the experimental test carried out, we have found that our sensor has a sensitivity higher than others reported so far, to the best of our knowledge. In addition, the platform introduced here can operate over a broad wavelength which makes it adaptable to different sensing targets. In addition, our sensor offers several advantages such as repeatability of fabrication, wide operating range and small size and weight, which benefit its sensing applications.
In turbomachinery, engine vibrations play an essential role, since they may lead to a fast component degradation, lowering the performance and ultimately yielding to fatigue damage. For these reasons, there is a high demand for measurement methods to monitor the behavior of the engine shaft adequately. In this experiment, we characterize the shaft behavior of a turbomachine by measuring the blade tip clearance and by converting it to a shaft displacement. To achieve this goal, we have employed two optical displacement sensors and we have applied the full spectrum technique.
Impact detection is used as proof of concept to demonstrate that the design principle of optical fibre-based reflective
displacement sensors is versatile enough to fit applications that go beyond the original concept for which they were
designed, i.e. Tip Clearance and Tip Timing. For that, a custom software has been created that allows to find the best
fibre arrangement within the fibre bundle that matches the specifications of the target application. After fabricating the
fibre bundle, the validity and usefulness of the simulations have been assessed by means of laboratory measurements on
the reflective displacement sensor. Finally some preliminary impact tests have been carried out to confirm the previous
work.
The results of an experimental investigation on the vibrational behaviour of a rotating disk are reported. This disk is a prototype that simulates a component of an aircraft engine. The air flow through the gap between the edge of the disk and the casing, produced because of the pressure difference between the upstream and downstream parts of the disk, might force the disk to flutter under certain circumstances. This situation is simulated in a wind tunnel. The main goal of the tests is to evaluate the vibrational behaviour of a rotating disk, obtaining the correspondence between the vibration frequencies of the disk and the pressure differences when the disk is rotating at diverse speeds. An innovative noncontact technique is utilised, which employs three optical sensors that are angularly equidistributed on the casing of the wind tunnel. In order to verify the results given by the optical sensors, a strain gauge was mounted on the surface of the rotating disk. The results show a perfect agreement between the vibration frequencies detected by both kinds of sensors, proving that the combination of both allows the calculation of the nodal diameter corresponding to the vibration of the disk.
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.
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.
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