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Infrared-optical characterization of emitting and absorbing gases at high temperatures and high pressures
Matthias Zipf, Jochen Manara, Thomas Stark, Mariacarla Arduini, Hans-Peter Ebert and Jürgen Hartmann

In the context of the optimization of stationary gas turbines, the surface temperatures of the turbine blades have to be measured by a non-contact technique using radiation thermometers during operation of the turbine. Nowadays turbine blades are protected by thermal barrier coatings. The infrared-optical properties of these coatings require the usage of the MIR or LWIR region for non-contact measurement of the surface temperatures. For performing such measurements and for properly analyzing the derived data, the transmission and absorption spectra of the combustion gas mixture within the turbine were determined at the local conditions during operation of the turbine.

Therefore, subject of this work is the measurement of the transmission spectra of carbon dioxide and water vapor at high temperatures and high pressures to identify a wavelength range, which is almost free of absorption and emission effects. In order to perform these measurements a Fourier-transform infrared spectrometer in combination with a high temperature and high pressure gas cell was used.

The obtained results showed that the wavelength region around 10 μm is nearly free of influence of the combustion gas, even at high temperatures and high pressures. The received data was compared with equivalent HITRAN-simulations that matched the measurement results well. Therefore, this wavelength region is available for non-contact temperature measurement.

Keywords: Gas transmission spectra, gas turbine, combustion gas, radiation thermometry, non-contact temperature measurement, thermal radiation, long wavelength infrared pyrometry, Fourier-transform infrared spectrometer

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