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27 May 2011 High temperature sensing with FBGs using a tunable laser interrogation system
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Within an ESA funded project combustion chambers of Ariane V rockets are investigated for further development. Due to temperature gradients of approximately 1300 K/mm in the combustion chamber during launch, material damages occur because of the Doghouse effect. To avoid these damages, the combustion chambers have to be redesigned wherefore the occurring temperatures have to be measured with an uncertainty of ±5 K. In order to measure the temperature in the small layer between the hot exhaust emissions and the coolant, optical fiber sensing is deployed. Embedding special optical sensor fibers that are high temperature resistant within the material allows measuring the wall temperature directly. In order to demonstrate fiber optic sensing for high temperature and strain measurement, Thermo Mechanical Fatigue (TMF) panels, constructed as sandwich structure have been developed that represent the combustion chamber walls. Coated fibers which are installed in the the panel can be subjected to thermal loads up to 1000 K inside a high temperature oven. Online measurements of FBG sensors inscribed in the embedded optical fibers can be carried out. The measurement results of the FBG sensors exactly match the data of the electrical reference sensor. For FBG readout we use our newly developed Scanning Laser (SL) Interrogation System which uses a tuneable laser source. The output wavelength is determined by a set of control currents. In order to archive the required accuracy a Current Control Unit (CCU) stabilizes the control currents and thereby the output wavelengths. The CCU significantly improves the accuracy and additionally enhances the measurement rate. The high temperature measurement results demonstrate compatibility with the requirements.
© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
B. Eder, M. Plattner, P. Putzer, P. Eckert, A. Reutlinger, and T. Zeh "High temperature sensing with FBGs using a tunable laser interrogation system", Proc. SPIE 8082, Optical Measurement Systems for Industrial Inspection VII, 80823M (27 May 2011);

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