Multipoint high temperature sensing with regenerated fiber Bragg gratings

Abstract

Two application examples of RFBG sensor arrays that are intended for high temperature profile measurements in chemical reaction vessels and in a gas turbine exhaust duct are described. The array for the chemical reaction vessel includes four sub-arrays with six measurement points each, distributed over a length of 2.3 m. By employing a largescale test facility, temperature profiles extending over 2.3 m with temperatures in the range of 200 °C to 500 °C were acquired with this RFBG array and an excellent agreement with thermocouple data was demonstrated. The second application reported is the measurement of the radial temperature distribution within the exhaust duct of a 7 MW gas turbine. Therefore, a three-point RFBG array was mounted radially in the exhaust gas stream and significant changes in the measured temperature gradient were observed when the engine was in idle or in full load operation mode. In addition to these field deployments of RFBG sensors, long-term annealing experiments at 450 °C in the research lab showed only a shift of the nonlinear temperature calibration curve without changing its shape, allowing recalibrations of RFBG sensor arrays at single temperature points. These examples demonstrate the suitability of RFBG based multipoint high temperature sensing for industrial applications.