  Radiative heat transfer has been proven to be important during the ignition
process in gas turbine. Those radiating gases (CO2, H2O, CO) generated during
combustion may display strong spectral, or nongray behavior, which is difficult
to both characterize and calculate. In this work, both the full-spectrum
k-distribution (FSK) and weighted-sum-of-gray-gases (WSGG) method, along with
the Dynamic-thickened-flame (DTF) and Large-Eddy-Simulation (LES) methods, are
used to analyze how spectral behavior affects the ignition process in an
experimental gas turbine. Results show that radiation affects the ignition
process by heating the relatively low temperature regions. Consequently, each
ignition phase is differently affected by different spectral treatments. During
the initial kernel phase, spectral properties have minimal influence on flame
structures and the ignition delay time due to the negligible radiation and
optically-thin scenario. However, during the flame growth phase, significant
differences appear in the flame structure and the flame propagation speed among
different spectral treatments. After the flame fill the combustor and during
the stable combustion phase, differences in flame structures calculated by
different models become less, but radiation still play an important role in
combustion. Therefore, high-fidelity spectral models are recommended during the
modelling of the ignition process in the gas turbine.
