Investigation on wall and gas temperatures inside a swirled oxy-fuel combustion chamber using thermographic phosphors, O2 rotational and vibrational CARS

Wall and gas phase temperatures inside a swirled oxy-fuel combustion chamber are important to characterize the combustion process. Wall temperatures were measured by thermographic phosphors and discussed in combination with gas phase temperatures. For gas phase temperatures an O2 vibrational coherent anti-Stokes Raman scattering (CARS) approach was compared to a N2/O2 rotational CARS (RCARS) system. The vibrational CARS (VCARS) setup was favorable due to higher signal strength at high temperatures. With this system gas phase temperature profiles inside a swirled oxy-fuel combustion chamber were measured and discussed for different operation conditions. The location of intermittent reaction zones could be determined. In order to provide a measurement tool for gas-assisted pulverized solid fuel flames the developed O2-VCARS system was successfully tested in such a harsh environment. Possible error sources related to particles within the probe volume are discussed

Characterization of temperature distributions in a swirled oxy-fuel coal combustor using tomographic absorption spectroscopy with fluctuation modelling

Oxy-fuel combustion promises efficient and inexpensive carbon dioxide sequestration and is therefore subject to active experimental research. However, the transfer of mature, non-intrusive diagnostic methods for temperature measurement like Coherent Anti-Stokes Raman Spectroscopy (CARS) from air-fed to oxy-fuel systems is challenging due to the deficiency in diatomic species suitable for thermometry. Although not limited to oxy-fuel atmospheres, we demonstrate the application of linear hyperspectral absorption tomography on water vapor in a swirled oxy-fuel coal combustor as a complementary diagnostic method, supplementing reference and validation data sets. Due to the burner design an axisymmetric reconstruction of the time-averaged temperature field is conducted. To compensate the temperature bias expected when evaluating time-averaged spectroscopic data we incorporate turbulent temperature fluctuations into our spectroscopic model, providing a fluctuation measure in addition to mean temperatures. The results quantitatively agree with vibrational O2-CARS measurements and qualitatively recreate spatial structures known from particle image velocimetry (PIV) flow fields