Improved spectral absorption-coefficient grouping strategies in radiation heat transfer calculations for combustion gases with pressure and temperature inhomogeneity

The grouping strategy for the spectral absorption coefficient of gases used in multigroup full spectrum k distribution and multiscale multigroup full spectrum k distribution models was improved to enable radiation-heat transfer calculations of combustion gas with temperature inhomogeneity under various pressures or large pressure gradients. The improvements in calculation accuracy resulting from different grouping strategies were evaluated using a series of semi-1D problems in which strong temperature and pressure inhomogeneity were present. Finally, the evaluations are given for the calculation of radiation heat transfer characteristics and thermal emission imaging of the exhaust system of a parallel turbine-based combined cycle (TBCC) engine.