Fiber-optic Multipoint Sensor Networks
In gas turbines and chemical reactors, important operating parameters such as efficiency and wear, but also plant safety, depend on compliance with specific temperature profiles. As the basis for further technological innovations, a sensor technology is being researched as part of a third-party funded project that increases the spatial resolution of the measured temperature profiles and at the same time reduces the space requirement and cabling effort. This is not feasible with conventional electrical temperature sensors.
So-called fiber Bragg gratings (FBG) are small, wavelength-selective partial mirrors in optical fibers. They are sensitive to changes in the local strain and temperature state of the optical fiber used and offer several unique sensing properties. In particular, immunity to electromagnetic interference and the possibility of wavelength multiplexing allow them to be used in previously inaccessible areas with minimal space requirements.
Key data and technical details
- High-temperature multi-point sensors based on regenerated fiber Bragg gratings (RFBG)
- Wavelength-temperature characteristic with measurement deviation ±2°C from 20°C to 800°C
- Sensor networks with 24 measuring points at 2 mm diameter and a length up to 2.4 m
- Spatial resolution of the temperature profiles up to 5 mm
- Average drift rate 1 K/year (over two years at 500°C)
- Planning and setting up the laboratory infrastructure for the production of the sensor prototypes
- Research on the physical formation processes of high-temperature-stable FBGs
- Comprehensive investigations regarding calibration and long-term stability (drift, corrosion)
- Development of a suitable assembly technique/protective enclosure
- Creation of LabVIEW applications for simulation, data processing and visualization
Result / success
The research project succeeded in transferring RFBG technology from the laboratory to real applications and demonstrating its functionality. This includes the use in gas turbines up to 60 MW and, for the first time, a long-term measurement over two years in a test reactor.
The results were published in a total of 6 articles in scientific journals and presented at 4 scientific conferences. Furthermore, a patent application was filed.
The funding organization Bayerische Forschungsstiftung (BFS) lists the project in the annual report 2019 under the heading “Success Stories”. Based on these successes, further research contracts could already be defined.
Links to Open Access Publications:
Measurements in the Gas Turbine: https://doi.org/10.3390/ijtpp5040025
Measurements in the test reactor: https://doi.org/10.3390/s19245476
BFS Annual Report 2019 (page 30): https://forschungsstiftung.de/assets/mediathek/jahresberichte/Jahresbericht_2019.pdf
News from Munich University of Applied Sciences on the Siemens Energy research contract: